Morphological, thermal and physicochemical characteristics of small granules starch from Mirabilis jalapa L

Accepted Manuscript Title: Morphological, thermal and physicochemical characteristics of small granules starch from Mirabilis jalapa L. Author: Augusto Pumacahua-Ramos Ivo Mottin Demiate Egon Schnitzler Ana Cl´audia Bedin Javier Telis-Romero Jos´e Francisco Lopes-Filho PII: DOI: Reference:

S0040-6031(15)00002-7 http://dx.doi.org/doi:10.1016/j.tca.2015.01.001 TCA 77111

To appear in:

Thermochimica Acta

Received date: Revised date: Accepted date:

24-10-2014 25-11-2014 4-1-2015

Please cite this article as: Augusto Pumacahua-Ramos, Ivo Mottin Demiate, Egon Schnitzler, Ana Cl´audia Bedin, Javier Telis-Romero, Jos´e Francisco Lopes-Filho, Morphological, thermal and physicochemical characteristics of small granules starch from Mirabilis jalapa L., Thermochimica Acta http://dx.doi.org/10.1016/j.tca.2015.01.001 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.

Morphological, thermal and physicochemical characteristics of small granules starch from Mirabilis jalapa L.

Augusto Pumacahua-Ramos1,2,3, Ivo Mottin Demiate3, Egon Schnitzler3(*), Ana Cláudia Bedin3, Javier Telis-Romero2,José Francisco Lopes-Filho2

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State University of Ponta Grossa – UEPG - Av. Carlos Cavalcanti, 4748 – ZIP 84030-900

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Paulista State University – IBILCE/UNESP - São Jose do Rio Preto - SP – Brazil.

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Department of Food Engineering, Universidad Peruana Unión– Juliaca Peru.

– Ponta Grossa – PR – Brazil. (*)[email protected]

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Highlights

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New source of small granules starch was studied.

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DSC analysis allowed to determine the gelatinisation of starch from M. jalapa seeds.

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Structural characteristics of granules were analysed by XRD and MEV techniques.

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Abstract

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The rheological and thermal behaviour were analysed by RVA dnd TG-DTA.

Some physicochemical and thermal properties of starch from Mirabilis jalapa L, seeds

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were evaluated. The starch was extracted after hulling and grinding the seeds and the flour obtained was suspended in 0.1% (m/v) NaOH solution for 12 h at 30 °C; it was then centrifuged, re-suspended, washed with deionised water and dried in an oven with circulating air at 40 °C for 12 hours. The micro-images of starch granules were performed by using scanning electron (SEM) and non-contact atomic force microscopy

(NC-AFM) techniques; X-ray diffraction and mid-infrared spectroscopy were both used to evaluate the relative crystallinity of the starch granules. Thermal analyses TG/DTG and DSC, were applied for the analysis of thermal behavior of this starch the and the cooking behavior of its aqueous solution was studied by using a viscometer RVA. Thermogravimetry showed that once dehydrated, the starch was stable up to 292ºC after which two steps of decomposition occurred, which were attributed to decomposition and oxidation of organic matter, respectively. The gelatinisation temperature and

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enthalpy, as assessed by DSC analysis, were 82.1 °C and 5.67 J g-1, respectively. RVA

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analysis showed pasting temperature of 76.4 °C, with a low viscosity peak at 95 °C, low breakdown, and high tendency to retrograde during cooling. Microscopic results reveal

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that the starch granules had a spherical shape and 67.4% of them presented diameters

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smaller than 890 nm. The X-ray diffractogram showed a typical A-type pattern and a

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relative crystallinity of 34% with a FTIR of 1,047/1,022 cm-1 and a ratio of 1.38.

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Keywords: differential scanning calorimetry, thermogravimetry, X-ray diffractometry,

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Mirabilis jalapa starch.

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Introduction

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The Mirabilis jalapa, known in Brazil by the name ‘Marvel’ (Maravilha, in Portuguese) is an ornamental plant that has its origin in Latin America. Nowadays, it is cultivated

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almost all over the world as an ornamental plant, but in some countries it is also

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employed as a popular medicine due to its antibacterial and healing properties. Some studies that examined the active components of this plant reported two small proteins that presented strong antibacterial activity [1,2]. These proteins were characterised [3] and tested against different types of bacteria [4] and moulds of rice [5], and their

properties were confirmed, making this ornamental plant a potential industrial raw material. The seeds of this plant also present high amounts of starch. The objective of the present paper was to extract and characterise the starch from the seeds of this plant and to study the granule morphology, particle size, crystalline structure, thermal and pasting properties. Materials and methods

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Materials

Seeds from Mirabilis jalapa (white, yellow and red flowers) were collected from plants

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in the the city of São José do Rio Preto (20° 49′ 12″ S, 49° 22′ 44″ W), SP, Brazil. The

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seeds were dried at room temperature (25 °C) and stored in plastic bags until processing

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for starch extraction. The seeds were hulled and their fractions were observed under

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stereo light microscope. Some images of broken seeds were made by using a scanning

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electron microscope (SEM) in order to observe the internal structure and organisation,

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as well as the distribution of the starch granules. Standard amylose, AM (A9262) and

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amylopectin, AP (A8515) were from Sigma Chemical Co. (USA).

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Starch isolation

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The Mirabilis seeds were manually hulled and the tegument was discarded. It was milled by using a knife mill (IKA Universal Mill M 20, Germany). The material was sieved and fine flour was produced mesh no. 80; (177µm). Starch extraction was performed by washing this flour with excess of standard NaOH 0.1% (m/m) solution and the precipitate was recovered by centrifugation (2,200 g). After several successive

precipitations, the starchy pellet was washed with water until pH reached 7.0. The starch dispersion was sieved through a 53 µm mesh and then dried at 45 °C for 24 h. The dried starch lumps were disintegrated in a knife mill and sieved through mesh nº 80 (177 µm). This was then stored in sealed plastic bags until further use.

Chemical analysis

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The moisture content was calculated based on weight loss after the samples were heated

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in an oven at 105 °C/12 h. The ash content was determined by incineration in a furnace at 550 °C/6 h. The fats were obtained by extraction using hexan in a Soxhlet apparatus.

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Protein content was estimated from the nitrogen content, which was obtained by the

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micro-Kjeldahl method, using a conversion factor of 6.25 as AOAC protocols and as

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previously reported [29]. The samples were tested in triplicate.

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The amylose contents were determined using the method known as the hot NaOH

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procedure [6] as follows: the starch sample was packed in a paper filter and dipped in

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hexan; it was kept for three days at 4 to 8 °C for complete lipid extraction. After that

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period, the starch was recovered by filtration and oven dried at 40 °C/12 h for amylose

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determination. The de-fatted starch samples (100 mg) were dispersed with 1 mL of ethanol and suspended in 9 mL of 0.5 mol L-1 NaOH standard solution. The suspensions

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were heated for 30 min in a water bath at a temperature of 95 °C and then left overnight.

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The solution was diluted to 100 mL, and a 5 mL quantity was transferred into a 100 mL volumetric flask with 25 mL of distilled water. Then 1.0 mL of 1 mol L-1 acetic acid, and 2 mL of standard iodine solution (0.2 % iodine in 2 % potassium iodide) were added and the mixture was then completed to 100 mL with distilled water.

The solution was mixed and then left for approximately 20 min to develop colour in a dark room. The optical absorbance was recorded at 620 nm using a spectrophotometer (Shimadzu UVmini-1240, Tokyo, Japan). A blank, containing all the reagents except starch, was prepared for the reference cell. Solutions of intermediate AM proportions, which were obtained by mixing the standard AM and AP (20, 15, 10, 5, and 0% of AM), were prepared as described above. A straight-line plot was used to determine the contents of AM in the samples. Triplicate AM content measurements were performed

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for each sample.

Scanning electron microscopy (SEM) and atomic force microscopy (AFM)

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Scanning electron microscopy makes it possible to characterise starch granules in

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relation to their shape and size. Atomic force microscopy makes it possible to measure

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the diameter of starch granules as well as their surface characteristics. As reported by

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[7], a topographical analysis of the surface of starch may be useful for calculating the

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average diameters and two types of rugosity; the average rugosity (Ra) and its average

(1)

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quadratic root (Rq) by using the following Equations (1) and (2):

(2)

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where: Z(x) is the function that describes the surface profile analysed in terms of height (Z) and position (x) of the sample over the evaluation length (L). The morphology of the granules was analysed using a scanning electron microscope, model S-3000N SEM (Hitachi Ltd, Tokyo, Japan). A double-sided strip was affixed to the conductive support of electrons and the starch was spread on strips. These were

coated with gold using an E 102 ion sputter (Hitachi Ltd., Tokyo, Japan) for 60 s at 50 mA. The granules were then examined under the following conditions: voltage of 15.0 kV, emission current of 100 mA, high vacuum (10.4 Pa), working distance of 18.9 19.9 mm with 5,000 X and 18,000 X magnification. For the atomic force microscopy (AFM) analysis of roughness and average diameters, a suspension was prepared with 1% starch. A droplet was placed on a glass slide and left to dry at room temperature. The analysis was performed in an atomic force microscope

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(AFM), model SPM 9600 (Shimadzu) by the non-contact method with scan rate (0.8

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Hz) in areas of 2 x 2 µm and 5 x 5 µm.

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Particle size distribution

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The particle size distribution was evaluated by using a laser diffraction particle size

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analyser (Zetasizer, model Nano ZS90, Malvern Instr., UK). Starch samples of 50 mg

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were dispersed in 25 mL of distilled water and mixed in an ultrasound sonicator for 10

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min at room temperature (~25 °C) until the complete breakdown of agglomerates.

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X-ray diffraction powder patterns (XRD)

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X-ray powder diffraction patterns (XRD) were obtained by using an X-ray

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diffractometer, model Ultima 4 (Rigaku, Japan), employing Cu Kα radiation (λ = 1.541 Å) and settings of 40 kV and 20 mA. The scattered radiation was detected in the angular range of 5-80º (2θ), with a scanning speed of 8º min-1 and a step of 0.06º.

FT-IR spectroscopy

Fourier transform mid-infrared spectroscopy was employed to collect starch spectra (FT-IR PRESTIGE-21, Shimadzu, Japan) using the transmission technique. KBr pellets were made with approximately 1 mg of starch and 100 mg of KBr for IR spectroscopy, using a hydraulic press. The number of scans adopted was 64 for each sample, and a 4 cm−1 resolution considering the 4000 to 400 cm-1 range; the temperature during the analysis was 25 °C. The Excel© (Microsoft) software programme was employed to analyse the spectral data. According to Smits et al. [8] and Soest et al. [9] the

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absorbances at wavenumbers 1,047 and 1,022 cm−1 correspond to the crystalline and

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amorphous zones, respectively. The ratio of 1,047/1,022 cm−1 with values over 1.0 indicates a higher proportion of crystalline material and lower values indicate a higher

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proportion of amorphous material, as reported elsewhere [10].

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Thermogravimetry and derivative thermogravimetry (TG-DTG)

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The thermogravimetric/derivative thermogravimetric curves (TG/DTG) were obtained

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using a thermal analysis system TGA-50 (Shimadzu, Japan), where the samples were

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heated from 20 ºC to 600 ºC using open alumina crucible with approximately 3.59 mg

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of the sample under a synthetic air flow of 150 mL min−1 at a heating rate of 10 ºC min−1. The instrument was preliminarily calibrated with standard weight and with

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standard calcium oxalate monohydrate. All the mass loss percentages were determined

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using TA-60 WS data analysis software and the DTG curves [11, 12, 18].

Differential scanning calorimetry (DSC)

The DSC curves were obtained using a thermal analysis system, model DSC-Q200 (TAInstruments, USA). The samples were heated from 30 to 100 °C at a heating rate of 10 °C/min. An empty sealed aluminium crucible was used as reference to balance the total heat capacity of the sample crucible. A 4:1 (water:starch m/m) mixture was prepared and maintained for 60 min to equilibrate the moisture content. The aluminium crucibles were hermetically sealed and then the curves were performed. The instrument was previously calibrated with Indium

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99.99 % purity, melting point with Tp = 156.6 ºC, ∆H = 28.56 J g-1. The results were

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calculated with Universal Analysis 2000 software. The gelatinisation parameters were

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automatically characterised by the instrument (Universal Analysis 2000), with onset temperature (TO, °C), peak temperature (TP, °C), conclusion temperature (TC, °C) as

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well as the gelatinisation enthalpy (∆Hg, J g-1) was calculated [11, 12, 29, 32].

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Pasting properties

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The pasting properties of the samples were determined using a rapid viscometer

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analyser model RVA-4 (Newport Sci., Australia). A suspension of 2.5 g (11% moisture)

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of starch in exactly 25.5 g of distilled water underwent a controlled heating and cooling cycle under constant shear (160 rpm) where it was held at 50 ºC for two min, heated

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from 50 to 95 ºC at 6 ºC min-1, and held at 95 ºC for 5 min, cooled to 50 ºC at 6 ºC min-1

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and held at 50 ºC for 2 min. The reported values are the means of the duplicate measurements [11, 18].

Statistical analysis

Analysis of variance (ANOVA) and Tukey’s test were used to compare sample means at 95% confidence level (P < 0.05) using the STATISTICA 7.0 software (StatSoft, Inc., Tulsa, OK, USA). All the measurements were carried out in duplicate or triplicate, as stated in the description of the corresponding methods. Results and discussion

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Morphology of the starch granules

Figure 1A shows the Mirabilis jalapa flower, after that become seeds and from which

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the starch granules were extracted. In Figure 1B it can be observed by SEM the micro-

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image (magnification 20 X) a transversal cut of Mirabilis jalapa seed. Figures 1C and

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5,000 X and 18,000 X, respectively.

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1D show the SEM micro-image of the obtained starch granules with magnification

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FIGURE 1

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With SEM technique, measurements were performed and it was possible to observe that all the starch granules shown spherical shape and small size (< or around 1 µm). The

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surface of starch granules from M. jalapa, were also observed by the NC-AFM

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technique, and their appearance, size and shape were estimated [11,12]. All these small starch granules presented spherical shape with some protrusions, flat and smooth regions. When these images are compared with AFM images of other starches [11, 12, 29-31], these granules present a homogenous appearance. The NC-AFM technique makes it possible to estimate average diameters, as well as the superficial rugosity, and

these values were calculated according Equations (1) and (2) and are presented in Table 2.

Proximate composition of the starch

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The starch granules presented average diameters of 1,056 ± 128 nm or 1.06 µm, which

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is lower than other common starches as waxy corn starch (14.9 µm) and cassava starch (13.08 µm) [11,12].

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When considering particle size distribution (Fig. 2), approximately 67.4% of the

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granules had diameters in the range 825 - 955 nm and the others were in the range 712 –

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1,106 nm, resulting in 900 nm as the average diameter.

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The starch from M. jalapa, when compared with others starches [15, 19, 20] presents

FIGURE 2

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similar average diameter and lacks studies in its applications.

Starch granules with small size present different properties, as reported by Chen et al.

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[13], whose study highlighted the lower viscosity presented by potato starch granules of

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smaller diameters, and this fact was associated with the higher resistance of the smaller granules to external factors. Some uses of small size starches are cited by Chen et al. [13] and they include fat substitutes, starch-filled biodegradable films, face (dusting) powders, stabilisers in baking powders, among others. Testing potato and sweet potato starches with different granular sizes, Chen et al. [13] concluded that the granules with

the smallest diameters produced gels with higher firmness, had better processability, characterised as fluid in starch dough for noodle making, and had better quality, which the authors attributed to the higher specific surface of the granules. Small starch granules, such as those of the Okenia hypogaea (fox peanut), which were studied by Sánchez-Hernández et al. [14], could be suitable for use in the cosmetic industry due to their high adsorbent capacity or as carriers in the food industry for encapsulating flavours, dyes, essences and other substances.

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Rayner et al. [15] tested intact starch granules isolated from quinoa (Chenopodium

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quinoa Willd.) to stabilise emulsion drops in so-called Pickering emulsions. The authors were interested in food emulsions and that was their motivation for using small starch

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granules for the stabilisation, because clays and other inorganic particles are comonly

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reported in non-food applications. The authors justified their choice of quinoa starch

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due to its relatively small granule size (0.5 to 3 µm in diameter) with a uniform size

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distribution. The authors also explained that a small particle size reduces the amount

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required (mg of starch per mL of oil) to stabilise a given emulsion droplet interface. In

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conclusion, Rayner et al. [15] wrote that starch granule Pickering-type emulsion

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systems may have applications beyond that of merely food products, for example in the

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paper, cosmetic and paint industries and for pharmaceutical drug formulations where

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starch is an approved excipient.

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Relative Crystallinity

The X-ray diffractogram of M. jalapa starch is presented in Figure 3. As shown the peaks at 14.9, 17.9, 23 and 32.2 (2θ angle), Mirabilis jalapa starch corresponds to an Atype diffraction pattern, like cereal starches. The relative crystallinity calculated in

agreement with the literature [31] by a ratio between areas of the main peaks and the total diffractogram area, that resulted in 33.86%, suggesting a starch with high amylopectin content [16]. The relatively high crystallinity was confirmed by the FTIR spectra and the absorbance ratio of 1,047/1,022 cm-1 that was 1.38, which was higher than unity [8, 17].

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FIGURE 3

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Thermal properties

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The TG/DTG and DSC curves are depicted in Figure 4. TG/DTG curves show three

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main stages of decomposition and a region of stability, which is similar to starches from

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other sources [11, 12, 18, 30, 31]. The first mass loss occurs between room temperature

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up to 131ºC (8.9%) and was attributed to dehydration. Once dehydrated, the M. jalapa

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starch show stability up to 292ºC, higher than cassava starch, which was found up to

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274 °C [18]. After the stability, the M. jalapa starch show two new steps of

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decomposition that were attributed to decomposition and oxidation of organic matter

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(amylose and amylopectin) that occurs in consecutive reaction and with loss of 69.01

FIGURE 4

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and 16.95%, respectively. The final residue (ash) was 5.05%.

The starch gelatinisation is shown in Figure 4. The gelatinisation enthalpy (∆Hgel) was 5.62 J g-1 and the peak temperature was 82.1 °C. As far as we know, these values have not yet been published for Mirabilis jalapa starch. In comparison, starch, from other

small granules as quinoa which also has an A-type, presented gelatinisation enthalpies of 1.66, 6.9 and 10.3 J g-1 and gelatinisation temperatures of 64.5, 62.3 and 62.6 °C [19– 21]. Similarly, amaranth starch presented values of 2.58 and 10.6 J g-1 and 74.5 and 74.9 °C for gelatinisation enthalpy and temperature, respectively [20, 22]. The differences between enthalpy values are due the genetic varieties, provenance, climatic conditions. The obtained results of TG/DTG and DSC are depicted in Table 3.

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TABLE 3

Singh & Kaur [23] studied the thermal properties of potato starch granules with

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different diameters and reported that small granules presented slightly higher

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gelatinisation temperatures than their larger counterparts.

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Pasting behavior

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The pasting behaviour of M. jalapa starch, which was evaluated by using a RVA-4

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Viscometer is presented in Figure 5. Granular size represents an important parameter for

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starch functionality and smaller wheat starch granules have presented slightly higher gelatinisation temperatures and lower gelatinisation enthalpy [24].

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Kaur et al [25] fractionated potato starch granules into small, medium and large sizes,

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with diameter ranges of 1–20, 20–40, and 40–65 µm, respectively and observed that the pasting properties such as peak and final viscosities were lower for small size granules, while peak viscosity temperatures were lower for large granules.

Shang et al [26] studied different rice cultivars and found a high pasting temperature (87 °C) and a low viscosity peak value (1,465 cP) as well as low swelling volume and swelling power, which the authors attributed to the small size of the starch granules.

FIGURE 5

As shown in Figure 5 and in Table 4, M. jalapa starch presented a RVA profile with

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relatively high pasting temperature (76.4 °C), an absence of a pronounced peak of

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viscosity, and cooking stability during analysis. This starch also had a high tendency to

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TABLE 4

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retrogradation, as final viscosity was the highest value during all the analyses.

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From the viscoamylograph, some important points should be considered; mainly the

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pasting temperature, which is recognised as the first perceptible increase in viscosity,

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the peak viscosity, the viscosity value at 95 °C, the viscosity after holding at 95 °C, the

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viscosity at 50 °C and the viscosity after holding at 50 °C. Calculations relating to some

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other ratios should also be included, such as the breakdown (hot paste viscosity/peak viscosity), setback (cold paste viscosity/peak viscosity), total setback (cold paste

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viscosity/hot paste viscosity) and relative breakdown, which is calculated by dividing

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the difference between peak viscosity and hot viscosity by the difference between cold paste viscosity and hot paste viscosity [27, 28]. Leelavathi et al [27] reported that retrogradation during setback is largely associated with soluble amylase and Defenbaugh and Walker [28], analysing regular and high-amylose corn starches, suggested that the amylose fraction seemed to be sensitive to extended exposure to high

shear during RVA analysis, which results in low setback. As reported by [33] the pasting properties of these small granules are higher as well as the tendency to retrogradation. Conclusion

It was possible to extract and purify M. jalapa starch on a laboratory scale with 0.8% of protein by conventional alkaline procedure and the starch had small and homogeneous

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granules that presented an RVA profile with relatively high pasting temperature, high

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cooking stability and tendency to retrogradation. Thermal analysis showed typical starch behaviour during mass loss (TG/DTG) and gelatinisation (DSC), with

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gelatinisation temperature and enthalpy around 80 °C and 5.62 J g-1, respectively. The

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small diameter of starch from Mirabilis jalapa (around 1 µm), could be suitable for use

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in the pharmaceutycal and cosmetic industry atributted to their high adsortion capacity.

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Also in the food industry for encapsulating flavours, essences and other substances.

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Acknowledgements

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The authors are deeply grateful for the financial support provided by C-LABMU/UEPG,

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UNESP/IBILCE, UPeU-J, CAPES, FINEP and CNPq and for the research scholarships granted to Ivo Mottin Demiate by CNPq.

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starch. Starch/Stärke 114 (1999) 116-120.

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pasting properties. J. Integr. Study Diet. Habits. 20 (2010) 294-299.

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[22] H. Choi, W. Kim, M. Shin. Properties of Korean amaranth starch compared to waxy millet

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and waxy sorghum starches. Starch/Stärke 56 (2004) 469-477.

[23] N. Singh, L. Kaur. Morphological, thermal, rheological and retrogradation properties of

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potato starch fractions varying in granule size. J. Sci. Food Agric. 84 (2004) 1241-1252.

[24] E. Chiotelli, M.L. Meste. Effect of small and large wheat starch granules on thermo mechanical behavior of starch. Cereal Chem. 79 (2002) 286-293.

[25] L. Kaur, J. Singh, O.J. McCarthy, H. Singh. Physico-chemical, rheological and structural properties of fractionated potato starches. J. Food Eng. 82 (2007) 383-394.

[26] C. Zhang, L. Zhu, K. Shao, M. Gu, Q. Liu. Toward underlying reasons for rice starches having low viscosity and high amylose: physiochemical and structural characteristics. J. Sci. Food Agric. 93 (2013) 1543-1551.

[27] K. Leelavathi, D. Indrani, J.S. Sidhu. Amylograph pasting behavior of cereal and tuber starches. Starch/Stärke 39 (1987) 378-381.

[28] L. Deffenbaugh, C.E. Walker, Comparison of starch pasting properties in the

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Brabender viscoamylograph and the rapid visco-analyzer. Cereal Chem. 66 (1989) 493-

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499.

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Colman, E. Schnitzler. Characterisation of native starches of seeds of Araucaria

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angustiofolia from four germplasm collections. Thermochim. Acta 565 (2013) 172-177.

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Schnitzler. Structural characteristics, physico-chemical, thermal and pasting properties of potato (Solanum tuberosum L.) flour: study of different cultivars and granulometries.

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J. Therm. Anal. Calorim. 111 (2013) 2211-2216.

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E.C. Vasconcelos, E. Schnitzler. Thermal, structural and rheological properties of starch from avocado seeds (Persea Americana, Miller) modified with standard sodium hypochlorite solutions. J. Therm. Anal. Calorim. 115 (2014) 1893-1899.

[32] C. Beninca, T.A.D. Colman, L.G. Lacerda, M.A.S.C. Filho, G. Bannach, E. Schnitzler. The thermal, rheological and structural properties of cassava starch granules modified with hydrochloric acid at different temperatures. Thermochim. Acta. 552 (2013) 65-69.

[33] C. Shuh-Ming, T. Shuw-Ling, L. Cheng-YiIsolation and Characterization of the Starch from Four-O’Clock Flower (Mirabilis jalapa L.) Seed. J. Food Sci. 48 (1983)

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1238 – 1241.

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N

Table 1

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Table 2

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Chemical analysis of starch from Mirabilis jalapa seeds and its proximate composition.

Average diameters and rugosity of Mirabilis jalapa starch granules evaluated by NC-

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AFM.

Table 3

TG/DTG and DSC results of Mirabilis jalapa starch.

Table 4

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Pasting properties (RVA) of Mirabilis jalapa starch.

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Table 1

(%, m/m, in dry basis)

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Component Seeds

100

60.9

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Seed coat Endosperm flour

39.1

M

Protein

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Total Carbohydrates*

N

Starch

98.73 0.8 0.23

Ash

0.24

D

Lipids

8.60

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Amylose

A

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*Table 2

Parameters

25 µm2

100 µm2

400 µm2

Average

Diameter

1,006

1,066

1,096

1,056

Standard deviation

82

171

131

128

Average rugosity, Ra

97

127

132

119

Average quadratic rugosity, Rq

127

163

172

154

Table 3

TG results

DTG results

Step

∆m ( %)

∆T (°C)

TP (°C)

1st

8.99

21.5 – 131.1

61 (endo)

Stability

-

131.1 – 291.9

-

nd

69.01

291.9 – 419.1

354.1 (endo)

3rd

16.95

419.1 – 546.8

536.0 (endo)

2

DSC results -1

Tp (°C)

Tc (°C)

∆Hgel (J g )

76.7±0.1

82.1±0.1

87.2±0.5

5.62±0.70

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To (°C)

Time (min)

Pasting

5.4

Peak

12.1

Breakdown Final Viscosity

Viscosity (cP)

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Description

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Table 4

A

23.5±2.5

76.4 94.9

14.7

1,000±4.0

88.0

23.0

1,309±25.5

50.0

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1,016±23.0

EP CC A

Temperature (°C)

Calculated as difference

Figure Captions Figure 1: (A) Mirabilis jalapa flower; (B) SEM photomicrograph (magnification 20 X) of a transversal cut of a seed from M. jalapa; (C) SEM photomicrograph (magnification 5,000 X) of starch granules isolated from M. jalapa; (D) SEM photomicrograph (magnification 18,000 X) of starch granules isolated from M. jalapa; (E) 3D micro-image obtained by NC-AFM of the surface of starch granules. Figure 2: Particle size distribution of M. jalapa starch analysed by laser diffraction particle size.

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Figure 3: XRD diffractogram showing a typical native starch obtained from Mirabilis jalapa seeds.

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Figure 5: RVA viscograms of Mirabilis jalapa starch.

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Figure 4: (A) TG/DTG and (B) DSC profiles of Mirabilis jalapa starch.

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Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

Table 1 shows the proportion of the different parts of the Mirabilis jalapa seeds as well as their chemical composition.

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TABLE 1

TABLE 2