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The influence of different sugars on corn starch gelatinization process with digital image analysis method
Accepted Manuscript The Influence of Different Sugars on Corn Starch Gelatinization Process with Digital Image Analysis Method Qian Li, Hang Li, Qunyu Gao PII:
S0268-005X(14)00288-4
DOI:
10.1016/j.foodhyd.2014.08.012
Reference:
FOOHYD 2696
To appear in:
Food Hydrocolloids
Received Date: 4 April 2014 Accepted Date: 18 August 2014
Please cite this article as: Li, Q., Li, H., Gao, Q., The Influence of Different Sugars on Corn Starch Gelatinization Process with Digital Image Analysis Method, Food Hydrocolloids (2014), doi: 10.1016/ j.foodhyd.2014.08.012. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical abstract Title: The Influence of Different Sugars on Corn Starch Gelatinization Process with Digital Image Analysis Method
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Authors: Qian Li, Hang Li, Qunyu Gao*
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Affiliations: Carbohydrate Lab, College of Light Industry and Food Sciences, South China University of Technology
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The dynamic gelatinization process of corn starch under different concentrations of sucrose
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The Influence of Different Sugars on Corn Starch
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Gelatinization Process with Digital Image Analysis Method
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Qian Li, Hang Li, Qunyu Gao*
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Carbohydrate Lab, College of Light Industry and Food Sciences, South China
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University of Technology, Guangzhou 510640, P.R. China
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E-mail address: [email protected]; [email protected]
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*
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E-mail: [email protected]
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Postal address: Carbohydrate Laboratory, College of Light Industry and Food
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Sciences, South China University of Technology, Guangzhou 510640, P.R. China
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Corresponding author: Tel: +86-13660261703; Fax: +86-20-87113848
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ACCEPTED MANUSCRIPT ABSTRACT: The digital image analysis, integral optical density (IOD) method,
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combined with “the model of response difference of crystallite change (MRDCC)”
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was applied to dynamically analyze the influence of different sugars on the
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gelatinization of corn starch. All of the saccharides (ribose, fructose, glucose, sucrose,
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lactose, trehalose, maltose, raffinose and stachyose) proposed in our research showed
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protection effect on starch crystalline structure during gelatinization. The protection
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effect increased with the increase of sucrose concentration (0~20%). Trisaccharide
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and tetrasaccharide were more effective in inhibiting the gelatinization process than
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disaccharide; and the protection effect of disaccharides on starch was bigger than that
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of monosaccharide during gelatinization. The gelatinization inhibition effect had good
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relationship with nDHN (dynamic hydration number), and the increase of the equatorial
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OH (e-(OH)) group number of saccharides might increase the inhibition effect on
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starch gelatinization. However, in addition to the e-(OH) groups, the combination
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ability of sugar with water molecules might be also related to the size of the sugar
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molecules and their three-dimensional structure. We believed that owing to the helical
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structure which formed though hydrogen bonds, tetrasaccharide tended to decrease
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the hydration ability of saccharide and destabilized the water structure, thus the
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inhibitory effect of stachyose was almost the same as raffinose.
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Keywords: corn starch; gelatinization; IOD method; sugars
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1. Introduction Starch is a kind of abundant renewable resources from plants. Within the
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category of starch, corn starch, which has a long history and unique advantages, is
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very representative. It is a typical A type starch and in its polymorphs, the double
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helices are closely packed together with a small amount of structural water
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(Bogracheva, Meares, & Hedley, 2006). When raw starch granules are heated in water,
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their semicrystalline nature is gradually eliminated, resulting in structural breakdown
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and starch polymer dispersion in solution. This heat-induced starch granule
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breakdown or the order to disorder phase transition is known as gelatinization
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(Jenkins & Donald, 1998; Ratnayake & Jackson, 2008) .
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Water plays an important role in the process of thermal starch gelatinization as
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the gelatinization temperature decreases with increasing water content of starch
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suspensions. Additionally the presence of alkali, salts, sugars, lipids, alcohol, organic
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acids and their salts etc. also influence starch gelatinization by rupturing hydrogen
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bonds within the starch granule, or by forming soluble complexes with starch. They
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have an impact on the gelatinization temperature and thus affect the extent of
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gelatinization (Zobel, 1984).
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Sugars have been shown to have a significant effect on the gelatinization and
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rheological properties of starches generally, and it has been found that they can
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change the gelatinization temperature (TP) (Gonera & Cornillon, 2002; Wootton &
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Bamunuarachchi, 1980), gelatinization enthalpy change (∆H) (Wootton, et al., 1980)
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and similarly they might increase or decrease the rate and degree of gelatinization
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(Rumpold & Knorr, 2005) and retrogradation (Hoover & Senanayake, 1996). The
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effect of sugars on starch gelatinization has been studied by many researchers using a 3
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(Evans & Haisman, 1982; Hoover, et al., 1996; Kohyama & Nishinari, 1991; Perry &
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Donald, 2002; Prokopowich & Biliaderis, 1995), rheological measurements (Ahmed,
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2012; Prokopowich, et al., 1995; Sopade, Halley, & Junming, 2004), light microscopy
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(Gonera, et al., 2002; Rumpold, et al., 2005), X-ray scattering (XRD) (Hoover, et al.,
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1996; Perry, et al., 2002), nuclear magnetic resonance (NMR) (Le Botlan & Desbois,
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1995; Rumpold, et al., 2005), viscometry with a Rapid Visco Analyser (RVA) (Torley
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& Van der Molen, 2005). etc. With different parameters, these methods can
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characterize the effect of sugars on starch gelatinization properties from different
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perspectives.
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Gelatinization has been shown to be a kinetically controlled process (Slade &
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Levine, 1988). Therefore, regardless of how gelatinization is monitored, any
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quantitative description of the process will be affected by changes in conditions such
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as the heating rate and extent of agitation. Some properties (viscosity, heat uptake,
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and loss of birefringence) may be monitored continuously during the process, while
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others (e.g. volume) are monitored more conveniently after interrupting the process
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(Leach, McCowen, & Schoch, 1959). However, this interruption, and the followed
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recovery of the experiment conditions confound the meaning of the results measured
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by these techniques (Ziegler, Thompson, & Casasnovas, 1993). In order to make the
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information of starch gelatinization more accurately, the real-time detection
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instruments should be used to reduce various pre- and post- processing effects on
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starch structure.
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Based on polarizing microscopy, the IOD method was of advantage compared
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with the previous traditional method, because it is able to characterize the starch 4
ACCEPTED MANUSCRIPT granules which stay in the partially gelatinized stage. At the same time, it is a method
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of real-time monitoring that dispenses with the pre- and after- treatment of various
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samples and its resulting date can reflect the real situation of the gelatinization
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process. Our previous works (Li, Xie, Yu, & Gao, 2013, 2014) have confirmed that
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IOD method has the following advantages: 1) IOD value is a integral function that is
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related to the area and the OD (optical density) value, the area is corresponding to the
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number of starch crystalline structure, and the OD is proportional to its intensity, so it
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is more accurate compared with traditional methods such as counting the particle
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number and calculating polarization area, as a result; 2) By repetitively measuring the
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optical density of the same digital image, the error result is less than 0.1 %, which
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indicates that the systematic errors can be controlled in a small range with robustness;
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3) good reproducibility. The parallel experiments shows that the measurement error of
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a sample is less than 5 %; 4) more than 1000 starch granules can be observed in a
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digital image and higher density of microscope observation can be achieved, which
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lead to the reduction of experiment workload and the raise statistical significance. The
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model of response difference of crystallite change (MRDCC) (Li, et al., 2013, 2014)
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is a new characterization of the crystallization change degree in the starch
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gelatinization process. It characterizes that the starch gelatinization speed changes
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with the temperature. MRDCC is more sensitive and accurate compared with DSC,
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even the subtle expansion in the pre-gelatinized stage could be detected. The water structure surrounding starch chains is stabilized by saccharides in
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starch-water-saccharide systems (Katsuta, Nishimura, & Miura, 1992a). If water
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around starch chain is stabilized by saccharides, the motion of the starch chains will
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be affected. Hence the gelatinization process of starch is controlled by saccharides. As 5
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increase of e-(OH) group numbers. The saccharide molecule which has a large
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number of e-(OH) groups possesses a stronger stabilizing effect on water structure
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(Uedaira & Uedaira, 1985).
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Although a major consequence of sugars on the gelatinization of starch granules
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has been described by many theories, a universally accepted explanation that caters
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for all the measurable changes is still not available. The objective of this work,
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therefore, has been to undertake a comprehensive study of the effect of different
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sugars on the gelatinization of corn starch, by combining information from hot stage
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microscopy with image analysis of starch granules. Meanwhile, a new method,
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integral optical density (IOD) method and MRDCC were employed in this work.
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2.
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2.1 Materials
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Materials and method
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Corn starch (food grade) was purchased from Guangdong Pengjin Industrial Ltd.
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(Guangdong, China), starch composition was: corn starch 84 %, water 12.35 %,
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protein 0.3 %, ash 0.3 %, lipid 0.87 % and phosphate 0.02 % which were measured in
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our laboratory. Ribose (D-ribose) was obtained from Sigma Chemical Co. (St. Louis,
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MO, USA); Sucrose, glucose (D-glucose), fructose (D-fructose), lactose, trehalose
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(,-trehalose), and maltose were purchased from Shanghai Boao
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biological technology Co., Ltd. (Shanghai, China). Raffinose and stachyose were
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obtained from Hefei bomei biotechnology Co., Ltd. (Hefei, China). All sugars were of
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analytical grade except stachyose with a content of 85 % and the main impurity was
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raffinose.
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2.2. Preparation of sample Corn starch slurries were prepared at starch concentrations of 10 % (starch:
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distilled water =1:9, dry basis). Starch slurries with 5 %, 10 %, 15 %, 20 % (w/w) of
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sucrose and 10 % (w/w) of glucose, ribose, fructose, lactose, trehalose, maltose,
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raffinose, and stachyose were prepared separately to evaluate the effects of sugar type
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and concentration on gelatinization properties. The measured starch-sugar slurries
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were equilibrated for 2 h and then sealed between two glass cover slip using Dow
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Corning 732 Sealant before replaced in the hot stage (model THMS600, Linkam
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Scientific Instruments Ltd., Britain). Each measurement was carried out in triplicate.
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2.3. Hot stage-light microscopy
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Each specimen in the hot stage was observed under a polarization microscope
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(Vanox BHS-2, Olympus Corp., Japan) equipped with a digital camera, which can
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display live video of birefringence granules in a real time. A temperature programmer
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was connected with the hot stage to control the heating progress from 40 °C to 80 °C
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at a rate of 2 °C /min. Live pictures were captured every 5 °C when below 60 °C,
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while 2 °C above 60 °C. Fifteen digital pictures of each sample were used and each
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image (2,048×1,536, 12 bits) was saved as TIFF image file, without data compression.
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All of the samples were observed under the same aperture (maximum), light intensity
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(fixed at 9), and exposure time (40ms). The combination of eyepiece and objective
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lens were selected with a magnification of 200 times, as described in our early
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research (Li, et al., 2013).
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2.4. IOD method
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It is a new method to measure the degree of gelatinization (DG). The IOD value
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of each digital picture was calculated by the Image-pro plus 5.0 software (Li, et al.,
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2013).
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The DG based on the IOD value (DGI) was calculated as defined in our early research (Li, et al., 2013).
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Background correction: C = A − B
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DGI % = (1 − C / C0 ) × 100%
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Where A is the original IOD value (IOD value calculated from the original
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digital image when all of the birefringence remain unchanged), B is the background
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IOD value (IOD value calculated from the original digital image when all of the
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birefringence disappeared), and C0 is the initial real IOD value (IOD value of
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birefringence light derived from the specific crystal structure of starch in the initial
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digital image). In this study, the IOD value of 40 °C was set as initial IOD value.
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2.5. Model of response difference of crystallite change (MRDCC)
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The MRDCC used in this paper were obtained according to our previous method
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(Li, et al., 2013). It characterizes the starch gelatinization speed changes with the
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temperature.
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Response difference of crystallite change (RDCC) is the variation of
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crystallization degree in a certain temperature range which characterizes
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gelatinization speed, %/△T for units, (%: Gelatinization degree difference; △T: the
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range of temperature corresponding to the crystallite change). In this study, △T is
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2 °C. 8
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40, 45, 50,…60, 62 …78, 80 °C) is the degree of gelatinization (DGI) of this
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temperature measured by the IOD method minus that of the previous temperature.
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The temperature is chosen for the horizontal axis, while the RDCC is chosen for the
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vertical axis, fitting the scatter with the tension spline function, and the MRDCC is
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obtained. Pn = ( DGn − DGn −5 ) × 2 / 5 ( 40 < n < 60 )
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Pn = DGn − DGn − 2
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(4)
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( 60 < n < 80 )
(3)
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Pn is the RDCC of a certain temperature point (n), DGn is the gelatinization degree of a certain temperature point (n) measured by IOD method. In this experiment, for example, above 60 °C, the RDCC at a certain temperature,
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such as 66 °C, is the gelatinization degree at 66 °C, minus the gelatinization degree of
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the previous temperature at 64 °C. Below 60 °C (including 60 °C), the RDCC at a
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certain temperature, such as 55 °C, is the result of the gelatinization degree at 55 °C
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subtraction to the gelatinization degree of the previous temperature at 50°C, and
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multiplied by 2/5 (Li, et al., 2014).
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2.6. Statistical analysis
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In this study, the photographs were in the same luminosity background. Starch
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granules were evenly distributed to make sure that the error is reduced to a minimum.
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The result was calculated and analyzed by Excel software, and curves were obtained
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by drawing and fitting the Curve Expert-Pro. Each sample was analyzed at least
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3. Results and discussion
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3.1. The starch gelatinization process in sucrose solution In Fig.1, only part of the photographs which showed the dynamic gelatinization
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process of corn starch in sucrose solutions and three kinds of concentration 0 %, 10 %,
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20 % were selected. By comparing the images, a visual result, that sucrose had
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delayed effect on the gelatinization process of corn starch, could be obtained.
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Especially after 72 °C, the effect difference between three different concentrations
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was apparent: in pure water (0 %), the polarization of starch granules nearly
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disappeared completely; and in the concentration of 10 %, a small amount of starch
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granules still remained; while in the concentration of 20 %, a large number of starch
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particles were not gelatinized. Three kinds of state, including ungelatinized (without
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any apparent/ detectable change under the birefringence light), partially gelatinized
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(decrease of light intensity and/ or area of birefringence light), and totally gelatinized
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(totally disappearance of birefringence light) were presented during the gelatinization
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process.
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3.2. The effect of different concentration of sucrose on starch gelatinization
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Fig.2 showed the DGI-temperature relationship of corn starch in different
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concentration of sucrose solution. With the increase of sucrose concentration, starch
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gelatinization curves shifted to the higher temperature and the DG of corn starch
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decreased at the same temperature point. It indicated that the increase of the sucrose
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concentration inhibited the gelatinization of starch. For instance, when the DG was
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50 %, the temperature corresponding to 0, 5, 10, 15 and 20 % of sucrose-water system
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were 66.2, 69.0, 70.0, 71.5 and 73.8 °C respectively. The successive rise of
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temperature was required to achieve the same degree of gelatinization, which means
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the gelatinization was more difficult; when the temperature was 70 °C, the DG
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corresponding to 0, 5, 10, 15 and 20 % of sucrose-water system were 86.6, 61.7, 50.0,
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32.6 and 17.3 % respectively. The DG at the same temperature point decreased
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successively and the inhibition of starch gelatinization process was expressed as a
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result.
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Sucrose delays the start and the ending of the gelatinization process. These
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results are in agreement with the results reported by Maaurf et al (Maaurf, Che Man,
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Asbi, Junainah, & Kennedy, 2001). In their investigation, for example, from 0.0-0.2 g
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sucrose/g starch the delay of onset temperature (To) was about 2.1 °C at water: starch
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ratio 3:1, which increased from 64.4 to 66.5 °C and the delay of melting temperature
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(Tm) was about 1.7 °C which climbed from 80.4 to 82.1 °C. The delaying effect was
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even more pronounced at lower water: starch ratios (1:1). The reason was that the
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small molecules of sucrose could penetrate into the interior of starch granules during
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the gelatinization process of corn starch, and the multiple hydroxyl groups contained
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in the sucrose structure interacted with the starch chains, hindered the water swelling
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of starch. As a result, gelatinization process was delayed and the gelatinization
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temperature was increased. Furthermore, the presence of sucrose, reduced the water
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content and the water activity, thereby affected the interaction between the starch
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chains and water molecules, and finally influenced the starch gelatinization (Kohyama,
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et al., 1991). This was also interpreted by some researchers (Prokopowich, et al., 1995)
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that small carbohydrate molecules which fit well in the hydrogen bonded structure of
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water had a stabilizing effect on the polymer chains, thus retarded chain reordering.
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The reverse was true for incompatible solutes that greatly disturbed the water
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structure. In order to do comparison with the methods and results of other researchers, we
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define the temperature point when DGI reaches 10 % (the loss of optical density is
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10%) as the start temperature (Ts), and the temperature point when DGI reaches 95 %
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(the loss of optical density is 95%) as the conclusion temperature (Tc). Ts and Tc of
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corn starch heated in different concentration of sucrose were showed in Table 1. With
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the increase of sucrose concentration (0~20 %), Ts and Tc increased successively.
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Fig.3 was the MRDCC of corn starch heated in different concentration of sucrose.
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Like the condition of corn starch heated in different concentration of NaCl solution
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(Li, et al., 2014), the addition of sucrose almost had no impact on the crystalline
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change peak shape, the crystalline change peak of corn starch presented pure single
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peak because it was A type starch. The weak shoulder peaks in the left and right sides
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of the main peak (< 2%) could be neglected. The temperature corresponded with the
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highest point was defined as peak temperature (Tp), which were also listed in Table 1.
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Sucrose may change the structure of water, and immobilizes water molecules. The
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swelling of starch granules in sugar solution occurred at higher temperatures and
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required much more energy in comparison with aqueous dispersion of starch without
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sucrose. Besides, the reason for the shift of the peak temperature to higher values with
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increasing concentration of added sucrose in corn starch was attributed to the
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stabilization of the ordered region of starch on the basis of zipper model approach,
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which had also been confirmed by the situation of potato and acorn starch (Hyang
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Aee, Nam Hie, & Nishinari, 1998; Kohyama, et al., 1991). The rotational freedom of
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segments constituting a molecular zipper, i.e. molecular chains in a fringed micellar
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zipper decreased, at the same time the number of zippers increased with increasing
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concentration of added sugars (Kohyama, et al., 1991).
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3.3 The effect of monosaccharides on the gelatinization of starch
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In Fig.4, all of the three kinds of monosaccharides inhibited the gelatinization of
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corn starch compared with the condition of heated in pure water, while the inhibition
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effect was glucose > fructose > ribose. For example, when the DG was 50 %,
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temperature corresponding to pure water, ribose, fructose, and glucose were 66.2,
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66.8, 68.5 and 68.9 °C respectively. From Fig.5, we also knew that their peak
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temperature were 67.5, 68.4, 69.9 and 70.3 °C respectively. As hexoses, glucose and
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fructose were far more effective than ribose, which is a kind of pentoses in inhibiting
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the gelatinization of corn starch, and the effect of ribose was not that significant at all.
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This results are in agreement with those reported in the literature (Katsuta, et al.,
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1992a). It is well known that the conformation of glucose well matches the tridymite
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structure in water(Kabayama et al., 1958; Uedaira, et al., 1985), and that the
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equatorial hydroxyl groups in a sugar molecule may be effectively bonded with a
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water molecule, and hence the hydration of sugar hydroxyl groups has a stronger
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stabilizing effect on the water structure (Hyang Aee, et al., 1998). The effective order
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agreed with the dynamic hydration number of these sugars, nDHN=18.6 for glucose,
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16.5 for fructose and 10.6 for ribose (Uedaira, Ishimura, Tsuda, & Uedairaî, 1990;
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Uedaira, et al., 1985). nDHN is an essential quantity which expresses the hydration
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properties of solutes and it has a good linear relation with the mean number of the
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equatorial OH groups, n(e-OH) (Uedaira, et al., 1990).
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3.4 The effect of disaccharides on the gelatinization of starch
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disaccharides. All of the disaccharides in our experiment inhibited the gelatinization
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of corn starch. While the inhibition effect was trehalose ≧ sucrose > lactose >
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maltose. Sucrose molecule is consisted from a D-glucose molecule and a
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-D-fructose molecule by -1,2-glycosidic bond; lactose molecule is
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consisted
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-1,4-glycosidic bond; maltose molecule is constituted from two D-glucose
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molecules by-1,4-glycosidic bond. When the DG reached 50 %, the
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temperature corresponding to pure water, sucrose, lactose, trehalose, and maltose
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were 66.2, 70.0, 69.0, 70.0, and 68.7 °C. From Fig.7. we also knew that their Tp were
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67.5, 71.2, 69.9, 70.6 and 69.9 °C respectively. As to maltose, our result was contrary
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with that of Katsuta et al. (1992a), in their report, maltose was the most effective
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saccharide in impeding starch gelatinization compared with sucrose and other
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monosaccharides from the evaluation by rheometry for rice starch gels; however, in
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our experiment, the gelatinization protect effect of maltose (nDHN=27.1) was smaller
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than sucrose (nDHN=25.2) and trehalose (nDHN=25.4). Our result was in agreement
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with the report of Savage and Osman (Savage & Osman, 1978), they studied the
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effects of saccharides on the swelling power of starch in starch-water-saccharide
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system and proposed that maltose acted like a monosaccharide. Beside the e-(OH)
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groups, the combination ability of sugar with water molecules also related with the
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size of the sugar molecules and their three-dimensional structure. The smaller the
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sugar molecule, the easier the combination. The molecular size or/ and
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three-dimensional structure of maltose and lactose were bigger than sucrose. The
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gelatinization inhibition of lactose was similar to that of maltose. Unlike other
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disaccharides, lactose and maltose acted like monosaccharide.
a
D-glucose
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3.5 The effect of oligosaccharides on the starch gelatinization Fig.8 showed the protection effect of four types of oligosaccharides on the
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gelatinization process of corn starch. When the DG reached 50 %, the temperature
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corresponding to pure water, glucose, sucrose, raffinose and stachyose were 66.2,
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68.9, 70.0, 70.8 and 70.8 °C respectively. Raffinose has a single D-galactopyranosyl
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unit attached to sucrose by-1,4-glycosidic bond. Stachyose has a single
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D-galactopyranosyl unit attached to raffinose by-1,4-glycosidic bond.
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Trisaccharide and tetrasaccharide were more effective in inhibiting the gelatinization
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process than disaccharide; and the protection effect of disaccharides on starch was
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bigger than monosaccharide during gelatinization. These were in agreement with the
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results of Katsuta (Katsuta, et al., 1992a; Katsuta, Nishimura, & Miura, 1992b) and
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Kohyama (Kohyama, et al., 1991). The nDHN increased in the order monosaccharide <
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disaccharide < trisaccharide < tetrasaccharide, at the same time, the molecular size or/
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and three-dimensional structure decreased in the order tetrasaccharide > trisaccharide >
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disaccharide > monosaccharide. From Fig.9, the Tp corresponding to raffinose
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(72.3 °C) was almost the same as that of stachyose (72.0 °C). The inhibitory effect of
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stachyose was almost the same as raffinose, which could be interpreted as: the
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increasing inhibitory effect of the increase of nDHN, offset with decreasing effect of the
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increase of molecular size or/ and three-dimensional structure. As a tetrasaccharide,
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stachyose acted like a trisaccharide. This result was consistent with the report of
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Katsuta et al. (1992b), in which they believe that maltotetraose may have an
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unsuitable conformation for stabilizing water structure as compared to maltotriose.
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According to the theory they proposed, when the number of glycosidic linkages is ≥ 4,
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the ideal conformation of saccharides might be a helical chain. The constitution of
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ability of higher DP (degree of polymerization) oligosaccharides, thus resulting in the
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decrease in the constructability of tridymite type- inlaid structure for water. Such
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helical glycosidic linkage might tend to destabilize the water structure. Unlike
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stachyose, raffinose, which is a typical linear structure oligosaccharide, was more
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effective than glucose and sucrose in inhibiting gelatinization of corn starch.
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According to our result, the inhibition effect of stachyose was almost the same as that
345
of raffinose, evenmore, its Tp was 0.3 °C smaller to that of raffinose, which meant that
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the helical structure oligosaccharide stabilized the starch matrices, but the
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stabilization ability might be less than that of linear oligosaccharides. That is to say,
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the degree of polymerization of saccharide molecules is an important factor in
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analyzing the protection effect of saccharides on the gelatinization of starch.
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3.6 The relationship between the number of e-(OH) groups of small molecular
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saccharides and starch gelatinization
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Table 2 showed the Ts, Tc and Tp of corn starch heated in other saccharides in
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addition to sucrose. The ability of saccharides to stabilize starch structure was closely
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related to the stereochemical conformation of saccharide molecules, i.e. the mean
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value of the number of e-(OH) groups in the molecule and the hydration of
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saccharides n(e-OH), i.e. the dynamic hydration number of the molecule (nDHN).
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Fig.10 showed the relationship of Tp and nDHN of 6 kinds of saccharides.(Katsuta, et
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al., 1992a, 1992b; Uedaira, et al., 1990; Watase, Kohyama, & Nishinari, 1992) Tp and
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nDHN had good linear correlation with R2=0.928.
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4. Conclusion
A comparative study was undertaken to examine the effect of different
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saccharides on the gelatinization of corn starch by employing with a new method,
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IOD method and the MRDCC was applied to analyze the results. The increase of the
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sucrose concentration (0~20 %) inhibited the gelatinization of starch. The multiple
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hydroxyl groups contained in the sucrose structure interacted with the molecular
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chains in starch hindered the water swelling of starch, and the increasing of sucrose
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concentration reduced the water content and the water activity. All of the saccharides
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proposed in our research showed protection effect on starch crystalline structure
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during gelatinization. Among monosaccharides, the gelatinization inhibition effect
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was in the order glucose > fructose > ribose; among disaccharides, the effect was in
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the order trehalose ≧ sucrose > lactose > maltose. By analyzing the oligosaccharides,
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trisaccharide and tetrasaccharide were more effective in inhibiting the gelatinization
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process than disaccharide; and the protection effect of disaccharides on starch was
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bigger than that of monosaccharide during gelatinization. The gelatinization inhibition
375
effect had good relationship with nDHN, the increase of the e-(OH) group number of
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saccharides might increase the inhibition effect on starch gelatinization. However, we
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also found out that some disaccharides (like maltose and lactose) acted like
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monosaccharide in term of protection effect on starch gelatinization and were less
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effective than other disaccharides, which meant that beside the e-(OH) groups, the
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combination ability of sugar with water molecules might be also related to the size of
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the helical structure which formed through hydrogen bonds, tetrasaccharide tended to
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decrease the hydration ability of saccharide and destabilize the water structure, thus
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the inhibitory effect of stachyose was almost the same as raffinose.
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Acknowledgements
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The study was carried out with financially support of the State Key Program of
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National Natural Science of China (Grant No. 31130042) and Guangdong Province
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Program of China (Grant No. 2012B091100291).
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Torley, P., & Van der Molen, F. (2005). Gelatinization of starch in mixed sugar
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Wootton, M., & Bamunuarachchi, A. (1980). Application of differential
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Ziegler, G. R., Thompson, D. B., & Casasnovas, J. (1993). Dynamic
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measurement of starch granule swelling during gelatinization. Cereal Chemistry, 70,
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Table 1 Ts, Tc and Tp (°C) of corn starch heated with different concentrations of
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sucrose as determined with IOD method 5%
10%
15%
20%
Ts
61.3
63.8
64.8
66.3
67.6
Tc
73.1
75.4
76.7
77.0
79.0
Tp
67.5
70.4
71.2
73.0
75.7
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0%
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Table 2 Ts, Tc and Tp (°C) of corn starch heated with different small molecular
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saccharides at a concentration of 10 % (w/w)
added sugars
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62.0
Tc
75.9
73.1
Tp
70.3
64.0
64.1
64.5
63.5
65.5
65.7
74.5
76.0
76.2
74.5
77.3
77.3
69.9
69.9
70.6
69.9
72.3
72.0
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68.4
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Ts
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glucose ribose fructose lactose trehalose maltose raffinose stachyose
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Fig.1. Micrographs of corn starch at different temperatures (40, 55, 60, 64, 66, 68, 72,
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76 and 80 °C) and different concentrations of sucrose solutions (0 %, 10 %, 20 %)
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during heating process under polarized light
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Fig.2. Relationship between temperature and DGI of corn starch under different
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concentrations of sucrose
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Fig.3. The MRDCC of corn starch heated with different concentrations of sucrose
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Fig.4. Relationship between temperature and DGI of corn starch under different
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monosaccharides (ribose, fructose, glucose) effect
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Fig.5. The MRDCC of corn starch heated with different monosaccharides
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Fig.6. Relationship between temperature and DGI of corn starch under different
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disaccharides (sucrose, lactose, trehalose, maltose) effect
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Fig.7. The MRDCC of corn starch heated with different disaccharides
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Fig.8. Relationship between temperature and DGI of corn starch under different
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oligosaccharides (glucose, sucrose, raffinose, stachyose) effect
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Fig.9. The MRDCC of corn starch heated with different oligosaccharides
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Fig.10. The relation between Tp and nDHN. 1. Ribose; 2. Fructose; 3. Glucose; 4.
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Sucrose; 5. Trehalose; 6. Raffinose
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10 % Sucrose solution
20 % Sucrose solution
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Fig. 1
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0% 5% 10% 15% 20%
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DGI (%)
60
40
20
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60
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Temperature (℃)
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Fig. 2
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Temperature (°C) 503
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90
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water ribose fructose glucose
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DGI (%)
60
40
20
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50
60
Temperature (℃)
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Fig.4
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508 509
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water sucrose lactose trehalose maltose
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60
40
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50
60
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Temperature (℃)
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water glucose sucrose raffinose stachyose
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60
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Temperature (℃)
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Fig.9
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5
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nDHN
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Fig.10
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ACCEPTED MANUSCRIPT Highlight The IOD method was applied to study the gelatinization of corn starch in different sugar solutions A model (MRDCC) was applied to analysis the influence differences
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The protection effect on starch gelatinization increased with the increasing of sucrose concentration
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The effect of different monosaccharides, disaccharides and oligosaccharides were analyzed
S0268-005X(14)00288-4
DOI:
10.1016/j.foodhyd.2014.08.012
Reference:
FOOHYD 2696
To appear in:
Food Hydrocolloids
Received Date: 4 April 2014 Accepted Date: 18 August 2014
Please cite this article as: Li, Q., Li, H., Gao, Q., The Influence of Different Sugars on Corn Starch Gelatinization Process with Digital Image Analysis Method, Food Hydrocolloids (2014), doi: 10.1016/ j.foodhyd.2014.08.012. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical abstract Title: The Influence of Different Sugars on Corn Starch Gelatinization Process with Digital Image Analysis Method
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Authors: Qian Li, Hang Li, Qunyu Gao*
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Affiliations: Carbohydrate Lab, College of Light Industry and Food Sciences, South China University of Technology
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The dynamic gelatinization process of corn starch under different concentrations of sucrose
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The Influence of Different Sugars on Corn Starch
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Gelatinization Process with Digital Image Analysis Method
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Qian Li, Hang Li, Qunyu Gao*
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Carbohydrate Lab, College of Light Industry and Food Sciences, South China
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University of Technology, Guangzhou 510640, P.R. China
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E-mail address: [email protected]; [email protected]
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*
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E-mail: [email protected]
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Postal address: Carbohydrate Laboratory, College of Light Industry and Food
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Sciences, South China University of Technology, Guangzhou 510640, P.R. China
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Corresponding author: Tel: +86-13660261703; Fax: +86-20-87113848
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ACCEPTED MANUSCRIPT ABSTRACT: The digital image analysis, integral optical density (IOD) method,
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combined with “the model of response difference of crystallite change (MRDCC)”
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was applied to dynamically analyze the influence of different sugars on the
15
gelatinization of corn starch. All of the saccharides (ribose, fructose, glucose, sucrose,
16
lactose, trehalose, maltose, raffinose and stachyose) proposed in our research showed
17
protection effect on starch crystalline structure during gelatinization. The protection
18
effect increased with the increase of sucrose concentration (0~20%). Trisaccharide
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and tetrasaccharide were more effective in inhibiting the gelatinization process than
20
disaccharide; and the protection effect of disaccharides on starch was bigger than that
21
of monosaccharide during gelatinization. The gelatinization inhibition effect had good
22
relationship with nDHN (dynamic hydration number), and the increase of the equatorial
23
OH (e-(OH)) group number of saccharides might increase the inhibition effect on
24
starch gelatinization. However, in addition to the e-(OH) groups, the combination
25
ability of sugar with water molecules might be also related to the size of the sugar
26
molecules and their three-dimensional structure. We believed that owing to the helical
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structure which formed though hydrogen bonds, tetrasaccharide tended to decrease
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the hydration ability of saccharide and destabilized the water structure, thus the
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inhibitory effect of stachyose was almost the same as raffinose.
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Keywords: corn starch; gelatinization; IOD method; sugars
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1. Introduction Starch is a kind of abundant renewable resources from plants. Within the
35
category of starch, corn starch, which has a long history and unique advantages, is
36
very representative. It is a typical A type starch and in its polymorphs, the double
37
helices are closely packed together with a small amount of structural water
38
(Bogracheva, Meares, & Hedley, 2006). When raw starch granules are heated in water,
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their semicrystalline nature is gradually eliminated, resulting in structural breakdown
40
and starch polymer dispersion in solution. This heat-induced starch granule
41
breakdown or the order to disorder phase transition is known as gelatinization
42
(Jenkins & Donald, 1998; Ratnayake & Jackson, 2008) .
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Water plays an important role in the process of thermal starch gelatinization as
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the gelatinization temperature decreases with increasing water content of starch
45
suspensions. Additionally the presence of alkali, salts, sugars, lipids, alcohol, organic
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acids and their salts etc. also influence starch gelatinization by rupturing hydrogen
47
bonds within the starch granule, or by forming soluble complexes with starch. They
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have an impact on the gelatinization temperature and thus affect the extent of
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gelatinization (Zobel, 1984).
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Sugars have been shown to have a significant effect on the gelatinization and
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rheological properties of starches generally, and it has been found that they can
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change the gelatinization temperature (TP) (Gonera & Cornillon, 2002; Wootton &
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Bamunuarachchi, 1980), gelatinization enthalpy change (∆H) (Wootton, et al., 1980)
54
and similarly they might increase or decrease the rate and degree of gelatinization
55
(Rumpold & Knorr, 2005) and retrogradation (Hoover & Senanayake, 1996). The
56
effect of sugars on starch gelatinization has been studied by many researchers using a 3
ACCEPTED MANUSCRIPT wide range of techniques. For example, differential scanning calorimetry (DSC)
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(Evans & Haisman, 1982; Hoover, et al., 1996; Kohyama & Nishinari, 1991; Perry &
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Donald, 2002; Prokopowich & Biliaderis, 1995), rheological measurements (Ahmed,
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2012; Prokopowich, et al., 1995; Sopade, Halley, & Junming, 2004), light microscopy
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(Gonera, et al., 2002; Rumpold, et al., 2005), X-ray scattering (XRD) (Hoover, et al.,
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1996; Perry, et al., 2002), nuclear magnetic resonance (NMR) (Le Botlan & Desbois,
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1995; Rumpold, et al., 2005), viscometry with a Rapid Visco Analyser (RVA) (Torley
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& Van der Molen, 2005). etc. With different parameters, these methods can
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characterize the effect of sugars on starch gelatinization properties from different
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perspectives.
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Gelatinization has been shown to be a kinetically controlled process (Slade &
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Levine, 1988). Therefore, regardless of how gelatinization is monitored, any
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quantitative description of the process will be affected by changes in conditions such
70
as the heating rate and extent of agitation. Some properties (viscosity, heat uptake,
71
and loss of birefringence) may be monitored continuously during the process, while
72
others (e.g. volume) are monitored more conveniently after interrupting the process
73
(Leach, McCowen, & Schoch, 1959). However, this interruption, and the followed
74
recovery of the experiment conditions confound the meaning of the results measured
75
by these techniques (Ziegler, Thompson, & Casasnovas, 1993). In order to make the
76
information of starch gelatinization more accurately, the real-time detection
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instruments should be used to reduce various pre- and post- processing effects on
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starch structure.
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Based on polarizing microscopy, the IOD method was of advantage compared
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with the previous traditional method, because it is able to characterize the starch 4
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of real-time monitoring that dispenses with the pre- and after- treatment of various
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samples and its resulting date can reflect the real situation of the gelatinization
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process. Our previous works (Li, Xie, Yu, & Gao, 2013, 2014) have confirmed that
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IOD method has the following advantages: 1) IOD value is a integral function that is
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related to the area and the OD (optical density) value, the area is corresponding to the
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number of starch crystalline structure, and the OD is proportional to its intensity, so it
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is more accurate compared with traditional methods such as counting the particle
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number and calculating polarization area, as a result; 2) By repetitively measuring the
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optical density of the same digital image, the error result is less than 0.1 %, which
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indicates that the systematic errors can be controlled in a small range with robustness;
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3) good reproducibility. The parallel experiments shows that the measurement error of
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a sample is less than 5 %; 4) more than 1000 starch granules can be observed in a
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digital image and higher density of microscope observation can be achieved, which
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lead to the reduction of experiment workload and the raise statistical significance. The
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model of response difference of crystallite change (MRDCC) (Li, et al., 2013, 2014)
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is a new characterization of the crystallization change degree in the starch
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gelatinization process. It characterizes that the starch gelatinization speed changes
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with the temperature. MRDCC is more sensitive and accurate compared with DSC,
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even the subtle expansion in the pre-gelatinized stage could be detected. The water structure surrounding starch chains is stabilized by saccharides in
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starch-water-saccharide systems (Katsuta, Nishimura, & Miura, 1992a). If water
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around starch chain is stabilized by saccharides, the motion of the starch chains will
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be affected. Hence the gelatinization process of starch is controlled by saccharides. As 5
ACCEPTED MANUSCRIPT a result, the stabilization degree of saccharides on water structure increases with the
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increase of e-(OH) group numbers. The saccharide molecule which has a large
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number of e-(OH) groups possesses a stronger stabilizing effect on water structure
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(Uedaira & Uedaira, 1985).
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Although a major consequence of sugars on the gelatinization of starch granules
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has been described by many theories, a universally accepted explanation that caters
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for all the measurable changes is still not available. The objective of this work,
112
therefore, has been to undertake a comprehensive study of the effect of different
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sugars on the gelatinization of corn starch, by combining information from hot stage
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microscopy with image analysis of starch granules. Meanwhile, a new method,
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integral optical density (IOD) method and MRDCC were employed in this work.
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2.
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2.1 Materials
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Materials and method
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Corn starch (food grade) was purchased from Guangdong Pengjin Industrial Ltd.
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(Guangdong, China), starch composition was: corn starch 84 %, water 12.35 %,
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protein 0.3 %, ash 0.3 %, lipid 0.87 % and phosphate 0.02 % which were measured in
121
our laboratory. Ribose (D-ribose) was obtained from Sigma Chemical Co. (St. Louis,
122
MO, USA); Sucrose, glucose (D-glucose), fructose (D-fructose), lactose, trehalose
123
(
124
biological technology Co., Ltd. (Shanghai, China). Raffinose and stachyose were
125
obtained from Hefei bomei biotechnology Co., Ltd. (Hefei, China). All sugars were of
126
analytical grade except stachyose with a content of 85 % and the main impurity was
127
raffinose.
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2.2. Preparation of sample Corn starch slurries were prepared at starch concentrations of 10 % (starch:
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distilled water =1:9, dry basis). Starch slurries with 5 %, 10 %, 15 %, 20 % (w/w) of
131
sucrose and 10 % (w/w) of glucose, ribose, fructose, lactose, trehalose, maltose,
132
raffinose, and stachyose were prepared separately to evaluate the effects of sugar type
133
and concentration on gelatinization properties. The measured starch-sugar slurries
134
were equilibrated for 2 h and then sealed between two glass cover slip using Dow
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Corning 732 Sealant before replaced in the hot stage (model THMS600, Linkam
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Scientific Instruments Ltd., Britain). Each measurement was carried out in triplicate.
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2.3. Hot stage-light microscopy
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Each specimen in the hot stage was observed under a polarization microscope
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(Vanox BHS-2, Olympus Corp., Japan) equipped with a digital camera, which can
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display live video of birefringence granules in a real time. A temperature programmer
141
was connected with the hot stage to control the heating progress from 40 °C to 80 °C
142
at a rate of 2 °C /min. Live pictures were captured every 5 °C when below 60 °C,
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while 2 °C above 60 °C. Fifteen digital pictures of each sample were used and each
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image (2,048×1,536, 12 bits) was saved as TIFF image file, without data compression.
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All of the samples were observed under the same aperture (maximum), light intensity
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(fixed at 9), and exposure time (40ms). The combination of eyepiece and objective
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lens were selected with a magnification of 200 times, as described in our early
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research (Li, et al., 2013).
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2.4. IOD method
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It is a new method to measure the degree of gelatinization (DG). The IOD value
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of each digital picture was calculated by the Image-pro plus 5.0 software (Li, et al.,
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2013).
154
The DG based on the IOD value (DGI) was calculated as defined in our early research (Li, et al., 2013).
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Background correction: C = A − B
(1)
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DGI % = (1 − C / C0 ) × 100%
(2)
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Where A is the original IOD value (IOD value calculated from the original
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digital image when all of the birefringence remain unchanged), B is the background
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IOD value (IOD value calculated from the original digital image when all of the
160
birefringence disappeared), and C0 is the initial real IOD value (IOD value of
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birefringence light derived from the specific crystal structure of starch in the initial
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digital image). In this study, the IOD value of 40 °C was set as initial IOD value.
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2.5. Model of response difference of crystallite change (MRDCC)
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The MRDCC used in this paper were obtained according to our previous method
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(Li, et al., 2013). It characterizes the starch gelatinization speed changes with the
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temperature.
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Response difference of crystallite change (RDCC) is the variation of
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crystallization degree in a certain temperature range which characterizes
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gelatinization speed, %/△T for units, (%: Gelatinization degree difference; △T: the
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range of temperature corresponding to the crystallite change). In this study, △T is
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2 °C. 8
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40, 45, 50,…60, 62 …78, 80 °C) is the degree of gelatinization (DGI) of this
174
temperature measured by the IOD method minus that of the previous temperature.
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The temperature is chosen for the horizontal axis, while the RDCC is chosen for the
176
vertical axis, fitting the scatter with the tension spline function, and the MRDCC is
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obtained. Pn = ( DGn − DGn −5 ) × 2 / 5 ( 40 < n < 60 )
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Pn = DGn − DGn − 2
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Pn is the RDCC of a certain temperature point (n), DGn is the gelatinization degree of a certain temperature point (n) measured by IOD method. In this experiment, for example, above 60 °C, the RDCC at a certain temperature,
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such as 66 °C, is the gelatinization degree at 66 °C, minus the gelatinization degree of
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the previous temperature at 64 °C. Below 60 °C (including 60 °C), the RDCC at a
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certain temperature, such as 55 °C, is the result of the gelatinization degree at 55 °C
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subtraction to the gelatinization degree of the previous temperature at 50°C, and
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multiplied by 2/5 (Li, et al., 2014).
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2.6. Statistical analysis
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In this study, the photographs were in the same luminosity background. Starch
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granules were evenly distributed to make sure that the error is reduced to a minimum.
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The result was calculated and analyzed by Excel software, and curves were obtained
192
by drawing and fitting the Curve Expert-Pro. Each sample was analyzed at least
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triplicate. 9
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3. Results and discussion
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3.1. The starch gelatinization process in sucrose solution In Fig.1, only part of the photographs which showed the dynamic gelatinization
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process of corn starch in sucrose solutions and three kinds of concentration 0 %, 10 %,
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20 % were selected. By comparing the images, a visual result, that sucrose had
199
delayed effect on the gelatinization process of corn starch, could be obtained.
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Especially after 72 °C, the effect difference between three different concentrations
201
was apparent: in pure water (0 %), the polarization of starch granules nearly
202
disappeared completely; and in the concentration of 10 %, a small amount of starch
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granules still remained; while in the concentration of 20 %, a large number of starch
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particles were not gelatinized. Three kinds of state, including ungelatinized (without
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any apparent/ detectable change under the birefringence light), partially gelatinized
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(decrease of light intensity and/ or area of birefringence light), and totally gelatinized
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(totally disappearance of birefringence light) were presented during the gelatinization
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process.
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3.2. The effect of different concentration of sucrose on starch gelatinization
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Fig.2 showed the DGI-temperature relationship of corn starch in different
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concentration of sucrose solution. With the increase of sucrose concentration, starch
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gelatinization curves shifted to the higher temperature and the DG of corn starch
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decreased at the same temperature point. It indicated that the increase of the sucrose
214
concentration inhibited the gelatinization of starch. For instance, when the DG was
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50 %, the temperature corresponding to 0, 5, 10, 15 and 20 % of sucrose-water system
216
were 66.2, 69.0, 70.0, 71.5 and 73.8 °C respectively. The successive rise of
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218
temperature was required to achieve the same degree of gelatinization, which means
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the gelatinization was more difficult; when the temperature was 70 °C, the DG
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corresponding to 0, 5, 10, 15 and 20 % of sucrose-water system were 86.6, 61.7, 50.0,
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32.6 and 17.3 % respectively. The DG at the same temperature point decreased
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successively and the inhibition of starch gelatinization process was expressed as a
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result.
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Sucrose delays the start and the ending of the gelatinization process. These
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results are in agreement with the results reported by Maaurf et al (Maaurf, Che Man,
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Asbi, Junainah, & Kennedy, 2001). In their investigation, for example, from 0.0-0.2 g
227
sucrose/g starch the delay of onset temperature (To) was about 2.1 °C at water: starch
228
ratio 3:1, which increased from 64.4 to 66.5 °C and the delay of melting temperature
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(Tm) was about 1.7 °C which climbed from 80.4 to 82.1 °C. The delaying effect was
230
even more pronounced at lower water: starch ratios (1:1). The reason was that the
231
small molecules of sucrose could penetrate into the interior of starch granules during
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the gelatinization process of corn starch, and the multiple hydroxyl groups contained
233
in the sucrose structure interacted with the starch chains, hindered the water swelling
234
of starch. As a result, gelatinization process was delayed and the gelatinization
235
temperature was increased. Furthermore, the presence of sucrose, reduced the water
236
content and the water activity, thereby affected the interaction between the starch
237
chains and water molecules, and finally influenced the starch gelatinization (Kohyama,
238
et al., 1991). This was also interpreted by some researchers (Prokopowich, et al., 1995)
239
that small carbohydrate molecules which fit well in the hydrogen bonded structure of
240
water had a stabilizing effect on the polymer chains, thus retarded chain reordering.
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The reverse was true for incompatible solutes that greatly disturbed the water
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structure. In order to do comparison with the methods and results of other researchers, we
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define the temperature point when DGI reaches 10 % (the loss of optical density is
245
10%) as the start temperature (Ts), and the temperature point when DGI reaches 95 %
246
(the loss of optical density is 95%) as the conclusion temperature (Tc). Ts and Tc of
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corn starch heated in different concentration of sucrose were showed in Table 1. With
248
the increase of sucrose concentration (0~20 %), Ts and Tc increased successively.
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Fig.3 was the MRDCC of corn starch heated in different concentration of sucrose.
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Like the condition of corn starch heated in different concentration of NaCl solution
251
(Li, et al., 2014), the addition of sucrose almost had no impact on the crystalline
252
change peak shape, the crystalline change peak of corn starch presented pure single
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peak because it was A type starch. The weak shoulder peaks in the left and right sides
254
of the main peak (< 2%) could be neglected. The temperature corresponded with the
255
highest point was defined as peak temperature (Tp), which were also listed in Table 1.
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Sucrose may change the structure of water, and immobilizes water molecules. The
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swelling of starch granules in sugar solution occurred at higher temperatures and
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required much more energy in comparison with aqueous dispersion of starch without
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sucrose. Besides, the reason for the shift of the peak temperature to higher values with
260
increasing concentration of added sucrose in corn starch was attributed to the
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stabilization of the ordered region of starch on the basis of zipper model approach,
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which had also been confirmed by the situation of potato and acorn starch (Hyang
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Aee, Nam Hie, & Nishinari, 1998; Kohyama, et al., 1991). The rotational freedom of
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segments constituting a molecular zipper, i.e. molecular chains in a fringed micellar
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zipper decreased, at the same time the number of zippers increased with increasing
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concentration of added sugars (Kohyama, et al., 1991).
268
3.3 The effect of monosaccharides on the gelatinization of starch
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In Fig.4, all of the three kinds of monosaccharides inhibited the gelatinization of
270
corn starch compared with the condition of heated in pure water, while the inhibition
271
effect was glucose > fructose > ribose. For example, when the DG was 50 %,
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temperature corresponding to pure water, ribose, fructose, and glucose were 66.2,
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66.8, 68.5 and 68.9 °C respectively. From Fig.5, we also knew that their peak
274
temperature were 67.5, 68.4, 69.9 and 70.3 °C respectively. As hexoses, glucose and
275
fructose were far more effective than ribose, which is a kind of pentoses in inhibiting
276
the gelatinization of corn starch, and the effect of ribose was not that significant at all.
277
This results are in agreement with those reported in the literature (Katsuta, et al.,
278
1992a). It is well known that the conformation of glucose well matches the tridymite
279
structure in water(Kabayama et al., 1958; Uedaira, et al., 1985), and that the
280
equatorial hydroxyl groups in a sugar molecule may be effectively bonded with a
281
water molecule, and hence the hydration of sugar hydroxyl groups has a stronger
282
stabilizing effect on the water structure (Hyang Aee, et al., 1998). The effective order
283
agreed with the dynamic hydration number of these sugars, nDHN=18.6 for glucose,
284
16.5 for fructose and 10.6 for ribose (Uedaira, Ishimura, Tsuda, & Uedairaî, 1990;
285
Uedaira, et al., 1985). nDHN is an essential quantity which expresses the hydration
286
properties of solutes and it has a good linear relation with the mean number of the
287
equatorial OH groups, n(e-OH) (Uedaira, et al., 1990).
288
3.4 The effect of disaccharides on the gelatinization of starch
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290
disaccharides. All of the disaccharides in our experiment inhibited the gelatinization
291
of corn starch. While the inhibition effect was trehalose ≧ sucrose > lactose >
292
maltose. Sucrose molecule is consisted from a D-glucose molecule and a
293
294
consisted
295
296
molecules by
297
temperature corresponding to pure water, sucrose, lactose, trehalose, and maltose
298
were 66.2, 70.0, 69.0, 70.0, and 68.7 °C. From Fig.7. we also knew that their Tp were
299
67.5, 71.2, 69.9, 70.6 and 69.9 °C respectively. As to maltose, our result was contrary
300
with that of Katsuta et al. (1992a), in their report, maltose was the most effective
301
saccharide in impeding starch gelatinization compared with sucrose and other
302
monosaccharides from the evaluation by rheometry for rice starch gels; however, in
303
our experiment, the gelatinization protect effect of maltose (nDHN=27.1) was smaller
304
than sucrose (nDHN=25.2) and trehalose (nDHN=25.4). Our result was in agreement
305
with the report of Savage and Osman (Savage & Osman, 1978), they studied the
306
effects of saccharides on the swelling power of starch in starch-water-saccharide
307
system and proposed that maltose acted like a monosaccharide. Beside the e-(OH)
308
groups, the combination ability of sugar with water molecules also related with the
309
size of the sugar molecules and their three-dimensional structure. The smaller the
310
sugar molecule, the easier the combination. The molecular size or/ and
311
three-dimensional structure of maltose and lactose were bigger than sucrose. The
312
gelatinization inhibition of lactose was similar to that of maltose. Unlike other
313
disaccharides, lactose and maltose acted like monosaccharide.
a
D-glucose
molecule
and
a
D-galactose
molecule
by
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3.5 The effect of oligosaccharides on the starch gelatinization Fig.8 showed the protection effect of four types of oligosaccharides on the
316
gelatinization process of corn starch. When the DG reached 50 %, the temperature
317
corresponding to pure water, glucose, sucrose, raffinose and stachyose were 66.2,
318
68.9, 70.0, 70.8 and 70.8 °C respectively. Raffinose has a single D-galactopyranosyl
319
unit attached to sucrose by
320
D-galactopyranosyl unit attached to raffinose by
321
Trisaccharide and tetrasaccharide were more effective in inhibiting the gelatinization
322
process than disaccharide; and the protection effect of disaccharides on starch was
323
bigger than monosaccharide during gelatinization. These were in agreement with the
324
results of Katsuta (Katsuta, et al., 1992a; Katsuta, Nishimura, & Miura, 1992b) and
325
Kohyama (Kohyama, et al., 1991). The nDHN increased in the order monosaccharide <
326
disaccharide < trisaccharide < tetrasaccharide, at the same time, the molecular size or/
327
and three-dimensional structure decreased in the order tetrasaccharide > trisaccharide >
328
disaccharide > monosaccharide. From Fig.9, the Tp corresponding to raffinose
329
(72.3 °C) was almost the same as that of stachyose (72.0 °C). The inhibitory effect of
330
stachyose was almost the same as raffinose, which could be interpreted as: the
331
increasing inhibitory effect of the increase of nDHN, offset with decreasing effect of the
332
increase of molecular size or/ and three-dimensional structure. As a tetrasaccharide,
333
stachyose acted like a trisaccharide. This result was consistent with the report of
334
Katsuta et al. (1992b), in which they believe that maltotetraose may have an
335
unsuitable conformation for stabilizing water structure as compared to maltotriose.
336
According to the theory they proposed, when the number of glycosidic linkages is ≥ 4,
337
the ideal conformation of saccharides might be a helical chain. The constitution of
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15
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339
ability of higher DP (degree of polymerization) oligosaccharides, thus resulting in the
340
decrease in the constructability of tridymite type- inlaid structure for water. Such
341
helical glycosidic linkage might tend to destabilize the water structure. Unlike
342
stachyose, raffinose, which is a typical linear structure oligosaccharide, was more
343
effective than glucose and sucrose in inhibiting gelatinization of corn starch.
344
According to our result, the inhibition effect of stachyose was almost the same as that
345
of raffinose, evenmore, its Tp was 0.3 °C smaller to that of raffinose, which meant that
346
the helical structure oligosaccharide stabilized the starch matrices, but the
347
stabilization ability might be less than that of linear oligosaccharides. That is to say,
348
the degree of polymerization of saccharide molecules is an important factor in
349
analyzing the protection effect of saccharides on the gelatinization of starch.
350
3.6 The relationship between the number of e-(OH) groups of small molecular
351
saccharides and starch gelatinization
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Table 2 showed the Ts, Tc and Tp of corn starch heated in other saccharides in
353
addition to sucrose. The ability of saccharides to stabilize starch structure was closely
354
related to the stereochemical conformation of saccharide molecules, i.e. the mean
355
value of the number of e-(OH) groups in the molecule and the hydration of
356
saccharides n(e-OH), i.e. the dynamic hydration number of the molecule (nDHN).
357
Fig.10 showed the relationship of Tp and nDHN of 6 kinds of saccharides.(Katsuta, et
358
al., 1992a, 1992b; Uedaira, et al., 1990; Watase, Kohyama, & Nishinari, 1992) Tp and
359
nDHN had good linear correlation with R2=0.928.
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4. Conclusion
A comparative study was undertaken to examine the effect of different
362
saccharides on the gelatinization of corn starch by employing with a new method,
363
IOD method and the MRDCC was applied to analyze the results. The increase of the
364
sucrose concentration (0~20 %) inhibited the gelatinization of starch. The multiple
365
hydroxyl groups contained in the sucrose structure interacted with the molecular
366
chains in starch hindered the water swelling of starch, and the increasing of sucrose
367
concentration reduced the water content and the water activity. All of the saccharides
368
proposed in our research showed protection effect on starch crystalline structure
369
during gelatinization. Among monosaccharides, the gelatinization inhibition effect
370
was in the order glucose > fructose > ribose; among disaccharides, the effect was in
371
the order trehalose ≧ sucrose > lactose > maltose. By analyzing the oligosaccharides,
372
trisaccharide and tetrasaccharide were more effective in inhibiting the gelatinization
373
process than disaccharide; and the protection effect of disaccharides on starch was
374
bigger than that of monosaccharide during gelatinization. The gelatinization inhibition
375
effect had good relationship with nDHN, the increase of the e-(OH) group number of
376
saccharides might increase the inhibition effect on starch gelatinization. However, we
377
also found out that some disaccharides (like maltose and lactose) acted like
378
monosaccharide in term of protection effect on starch gelatinization and were less
379
effective than other disaccharides, which meant that beside the e-(OH) groups, the
380
combination ability of sugar with water molecules might be also related to the size of
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382
the helical structure which formed through hydrogen bonds, tetrasaccharide tended to
383
decrease the hydration ability of saccharide and destabilize the water structure, thus
384
the inhibitory effect of stachyose was almost the same as raffinose.
385
Acknowledgements
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The study was carried out with financially support of the State Key Program of
387
National Natural Science of China (Grant No. 31130042) and Guangdong Province
388
Program of China (Grant No. 2012B091100291).
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on the gel-sol transition of agarose by differential scanning calorimetry.
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Thermochimica Acta, 206, 163-173.
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Wootton, M., & Bamunuarachchi, A. (1980). Application of differential
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scanning calorimetry to starch gelatinization. III. Effect of sucrose and sodium
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chloride. Starch‐Stärke, 32, 126-129.
Ziegler, G. R., Thompson, D. B., & Casasnovas, J. (1993). Dynamic
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measurement of starch granule swelling during gelatinization. Cereal Chemistry, 70,
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247-251.
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Zobel, H. F. (1984). Gelatinization of starch and mechanical properties of starch pastes. Starch: Chemistry and Technology, 2, 285-309.
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ACCEPTED MANUSCRIPT 471
Table 1 Ts, Tc and Tp (°C) of corn starch heated with different concentrations of
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sucrose as determined with IOD method 5%
10%
15%
20%
Ts
61.3
63.8
64.8
66.3
67.6
Tc
73.1
75.4
76.7
77.0
79.0
Tp
67.5
70.4
71.2
73.0
75.7
SC
RI PT
0%
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Table 2 Ts, Tc and Tp (°C) of corn starch heated with different small molecular
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saccharides at a concentration of 10 % (w/w)
added sugars
477
62.0
Tc
75.9
73.1
Tp
70.3
64.0
64.1
64.5
63.5
65.5
65.7
74.5
76.0
76.2
74.5
77.3
77.3
69.9
69.9
70.6
69.9
72.3
72.0
EP
64.0
68.4
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Ts
TE D
glucose ribose fructose lactose trehalose maltose raffinose stachyose
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ACCEPTED MANUSCRIPT Figure Captions
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Fig.1. Micrographs of corn starch at different temperatures (40, 55, 60, 64, 66, 68, 72,
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76 and 80 °C) and different concentrations of sucrose solutions (0 %, 10 %, 20 %)
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during heating process under polarized light
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Fig.2. Relationship between temperature and DGI of corn starch under different
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concentrations of sucrose
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Fig.3. The MRDCC of corn starch heated with different concentrations of sucrose
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Fig.4. Relationship between temperature and DGI of corn starch under different
486
monosaccharides (ribose, fructose, glucose) effect
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Fig.5. The MRDCC of corn starch heated with different monosaccharides
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Fig.6. Relationship between temperature and DGI of corn starch under different
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disaccharides (sucrose, lactose, trehalose, maltose) effect
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Fig.7. The MRDCC of corn starch heated with different disaccharides
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Fig.8. Relationship between temperature and DGI of corn starch under different
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oligosaccharides (glucose, sucrose, raffinose, stachyose) effect
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Fig.9. The MRDCC of corn starch heated with different oligosaccharides
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Fig.10. The relation between Tp and nDHN. 1. Ribose; 2. Fructose; 3. Glucose; 4.
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Sucrose; 5. Trehalose; 6. Raffinose
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ACCEPTED MANUSCRIPT 0 % Sucrose solution
10 % Sucrose solution
20 % Sucrose solution
40
RI PT
°C
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55
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60
64
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°C
66
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ACCEPTED MANUSCRIPT 68 °C
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72
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°C
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80
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Fig. 1
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100
0% 5% 10% 15% 20%
80
RI PT
DGI (%)
60
40
20
40
50
60
70
Temperature (℃)
500
Fig. 2
TE D
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RDCC (%/2°C)
501
502
Temperature (°C) 503
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80
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ACCEPTED MANUSCRIPT
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water ribose fructose glucose
80
RI PT
DGI (%)
60
40
20
40
50
60
Temperature (℃)
506
Fig.4
510
TE D
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RDCC (%/2°C)
507
508 509
70
80
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Temperature (°C) Fig.5
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water sucrose lactose trehalose maltose
80
RI PT
DGI (%)
60
40
20
40
50
60
70
Temperature (℃)
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TE D
EP
RDCC (%/2°C)
Fig.6
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Temperature (°C)
Fig.7
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ACCEPTED MANUSCRIPT
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water glucose sucrose raffinose stachyose
80
RI PT
DGI (%)
60
40
20
40
50
60
70
Temperature (℃)
519
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RDCC (%/2°C)
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80
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Temperature (°C)
Fig.9
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ACCEPTED MANUSCRIPT 73
72
70
69
5
10
15
25
nDHN
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Fig.10
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Tp (°C)
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ACCEPTED MANUSCRIPT Highlight The IOD method was applied to study the gelatinization of corn starch in different sugar solutions A model (MRDCC) was applied to analysis the influence differences
RI PT
The protection effect on starch gelatinization increased with the increasing of sucrose concentration
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The effect of different monosaccharides, disaccharides and oligosaccharides were analyzed