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Physicochemical and antioxidant properties of dietary fibers from Qingke (hull-less barley) flour as affected by ultrafine grinding
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
Available online at www.sciencedirect.com
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Physicochemical and antioxidant properties of dietary fibers from Qingke (hull-less barley) flour as affected by ultrafine grinding Bin Dua,b,c, Fengmei Zhua, Baojun Xuc,n,1 a
Hebei Normal University of Science and Technology, Qinhuangdao 066600, Hebei, China School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China c Food Science and Technology Program, Beijing Normal University—Hong Kong Baptist University United International College, Zhuhai 519085, Guangdong, China b
ar t ic l e in f o
abs tra ct
Article history:
The effect of particle size of Qingke flour and particle size of dietary fiber (DF) on
Received 27 March 2014
physicochemical and antioxidant capacities of DF was investigated. Qingke and extracted
Received in revised form
DF were ground by regular and ultrafine grinding and their particle sizes were determined
27 July 2014
using laser diffraction method. The results indicated that ultrafine grinding could
Accepted 20 September 2014
effectively pulverize DF particles to submicron scale; the particle size distribution was close to a Gaussian distribution. The soluble DF in Qingke flour was increased significantly
Keywords:
after ultrafine grinding. With the decrease of particle size, the water holding capacity
Qingke
(WHC) of Qingke DF was reduced (po0.05), while the swelling capacity, oil binding capacity
Dietary fiber
(OBC), and nitrite ion absorption capacity were increased (po0.05), and the water retention
Superfine grinding
capacity (WRC) had no significant change. The antioxidant activities of Qingke DF were
Hydration properties
increased after ultrafine grinding. Micronized insoluble DF showed increased DPPH radical scavenging activity and ferric reducing antioxidant power. & 2014 Elsevier Ltd. All rights reserved.
1.
Introduction
Dietary fiber (DF) is involved in disease prevention and enhanced health of consumers. In particular, soluble components of DF have several physicochemical functions (such as increased water binding and alteration of the food matrix viscosity) which in turn contribute to physiological attenuations such as cholesterol and fat binding, decrease in blood glucose levels, preventing constipation and facilitating good colonic health (Foschia, Peressini, Sensidoni, & Brennan, 2013). It has been proved that intake of diet containing high DF is negatively related to the incidence rate of chronic diseases, such as n
obesity, diabetes mellitus, large bowel cancer, cardiovascular disease, colonic diverticulitis and constipation (Eshak et al., 2010; Isken, Klaus, Osterhoff, Pfeiffer, & Weickert, 2010; Kim, 2000). Nowadays, the average worldwide ingestion of DF is still considerably lower than the recommended daily intake levels. So, it is necessary to add DF to food products. DFs have been extensively studied for their ability to regulate transit time due to the increase of stool bulk, and other beneficial properties such as hydration properties like swelling, water-holding and water retention capacities (Robertson et al., 2000). Growing attention has been paid to Qingke (Hordeum vulgare L. var. nudum Hook. f) due to its specific attributes,
Corresponding author. Tel.: +86 756 3620636; fax: +86 756 3620882. E-mail address: [email protected] (B. Xu). 1 Present address: Baojun Xu, 28, Jinfeng Road, Tangjiawan, Zhuhai 519085, Guangdong, China.
http://dx.doi.org/10.1016/j.bcdf.2014.09.003 2212-6198/& 2014 Elsevier Ltd. All rights reserved.
171
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
such as high beta-glucan content, high total DF content, highfeeding value (animal nutrition), and high-malt quality. The health benefits of DF have been widely recognized. Qingke, also called hull-less barley, differs from regular hulled barley cultivars, as it is a barley line with fewer hulls to cover the caryopsis (Han et al. 2008; Thomason, Brooks, Griffey, & Vaughn, 2009). Qingke is the main staple food crop in Qinghai-Tibet Plateau, China. Hull-less barley with low amylose and high β-glucan is used as an essential food crop for human consumption, as a brewing material and as an important feed source (Nimazhaxi, 1998; Luan & He, 2004; Yang, Christensen, Mckinnon, Beattie, and Yu, 2013). Ultrafine grinding technology is an emerging technology showing great potential in nutraceuticals and functional foods manufacture for human health improvement (Chen, Weiss, & Shahidi, 2006). Constituents in ultrafine powders are easily absorbed during digestion in the GI track of humans, and this may have an impact on improving the quality and safety of food products and positively influencing human health. Although the effect of ultrafine grinding on antioxidant properties of wheat bran DF (Zhu, Huang, Peng, Qian, & Zhou, 2010) and wine grape pomace DF (Zhu, Du, & Li, 2014a) have been published, the use of ultrafine grinding in DF processing remains rather limited. Probably due to the toughness and polymeric nature of DF in various plant materials, as well as rather inadequate equipment support for production of ultrafine powders (Zhu et al., 2010). Since the reduction of particle size would substantially increase the particle surface area and cause the release of some antioxidant compounds (Rosa, Barron, Gaiani, Dufour, & Micard, 2013), it is valuable to examine how hydration and antioxidant properties of DF are affected by ultrafine grinding. The objective of this study was to evaluate the application of ultrafine grinding technology for producing Qingke DF in the submicron range and to investigate the effects of ultrafine grinding on the physicochemical and antioxidant properties of insoluble DF from Qingke.
2.3. Preparation of insoluble dietary fiber (IDF) before ultrafine grinding IDF before ultrafine grinding was prepared from Qingke flour using the procedure described by Park, Jiang, Simonsen, and Zhao (2009) with minor modifications. Briefly, Qingke flour (100 g, 0.42 mm) was sonicated in pH 6.0 water (2000 mL) at 20 1C for 20 min. α-Amylase (2000 U/g) (1 g) was added, and the mixture was incubated at 60 1C for 3.5 h. Protease (200,000 U/g) (0.5 g) was added, and the mixture was incubated at 55 1C for 3 h. Finally, the residue was washed with cold water and dried at 50 1C overnight in a vacuum oven to yield a fraction denoted as Qinke IDF.
2.4. Preparation of Qingke flour and IDF with ultrafine grinding Qingke flour and IDF were further micronized by a mini-type airflow pulverization instrument (QLM-80 K, Shangyu City Heli Powder Engineering Co., Ltd., Zhejiang, China). The working pressure was set at 70 Mpa, and the working frequency was set at 40 Hz. Qingke flour and IDF after ultrafine grinding were sealed in aluminum foil containers and kept in a desiccator for further study. The whole flow chart of material processing in this study is elucidated in Fig. 1.
2.5. Determination of DF content in Qingke flours from regular and ultrafine grinding The moisture content, total dietary fiber (TDF), IDF and soluble dietary fiber (SDF) contents in flours were determined using the respective AOAC methods (AOAC, 2000, 2005, 1996).
Qingke
Regular grinding
Qingke wholegrain flour
2.
Materials and methods
2.1.
Materials and chemicals
Blue Qingke (Dulihuang) was purchased from Qinghai Xinlvkang Food Co., Ltd. (Qinghai, China) originating from the 2012 crop year. Phosphate-buffered saline (PBS, pH 7.0), α-amylase, and protease were purchased from Beijing Aoboxing Biotechnology Co., Ltd. (Beijing, China). Gallic acid, 1,1-diphenyl-2picrylhydrazyl (DPPH), 2,4,6-tri (2-pyridyl)-s-triazine (TPTZ) were purchased from National Standard Samples Center (Beijing, China). All other reagents were of analytical grade.
2.2.
Extraction
Insoluble dietary fiber (IDF) Ultrafine grinding (UFG) UFG flour
UFG IDF
Preparation of Qingke flour with regular milling
Qingke flour was ground by a regular laboratory mill (FZ102, Tianjin Taisite Co. Ltd., Tianjin, China), and passed through a 40-mesh (0.42 mm) screen.
Physicochemical properties
Antioxidant properties
Fig. 1 – Flow chart for the study on Qingke flour and IDF.
172
2.6.
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
Particle size measurement of Qingke DF
A laser diffraction particle size analyzer (LA-920, Horiba Limited, Japan) was employed for the determination of primary particle size distribution. The samples (Qingke flour and IDF) were suspended in ethanol directly in the measurement cell (small volume unit sample module) and the suspensions were analyzed when the obscuration was between 70 and 80%.
2.7.
Hydration properties of IDF
2.7.1.
Water-holding capacity (WHC) of IDF
WHC is defined by the quantity of water that is bound to the fibers without the application of any external force (except for gravity and atmospheric pressure). Accurately weighed dried IDF (1.0 g) was loaded into a graduated test tube, around 30 mL of water was added and it was hydrated for 18 h. The supernatant was subsequently removed by passing through a sintered glass crucible (G4) under vacuum. The hydrated weight of IDF was recorded, and it was dried at 105 1C for two hr to obtain the residual dry weight (Raghavendra, Rastogi, Raghavarao, & Tharanathan, 2004). WHC g=g ¼ ðHydrated weight–Dry weightÞ=Dry weight
2.7.2.
Water retention capacity (WRC) of IDF
WRC is defined as the quantity of water that remains bound to the hydrated fiber following the application of an external force (pressure or centrifugation). Accurately weighed dried IDF (1.0 g) was loaded into a graduated centrifugal tube, 30 mL of water was added and the sample was allowed to hydrate for 18 h. Following centrifugation at 3000 g for 20 min, the supernatant was removed by passing through a sintered glass crucible (G4) under vacuum. The hydrated weight was recorded, and then sample was dried at 105 1C for 2 h to obtain its dry weight (Raghavendra et al., 2004). WRC g=g ¼ ðHydrated weight after centrifugation–Dry weightÞ =Dry weight
2.7.3.
Swelling capacity of IDF
Swelling property is defined as the ratio of the volume occupied when the sample is immersed in excess of water after equilibration to the actual weight. Accurately weighed dried IDF (0.2 g) was placed in a graduated test tube, around 10 mL of water was added, and IDF was allowed to hydrate for 18 h. The final volume attained by the sample was measured after 18 h (Raghavendra et al., 2004). SwellingcapacityðmL=gÞ ¼ Volume occupied by sample =Original sample weight
2.7.4.
Oil-binding capacity (OBC) of IDF
OBC was determined by the method of Sangnark and Noomhorm (2003) with slight modifications. A dried IDF (5.0 g) was mixed with peanut oil in a centrifugal tube and left for 1 h at room temperature (25 1C). The mixture was then centrifuged at 1500 g for 10 min, the supernatant was decanted and the pellet was recovered by filtration through
a nylon mesh. OBC was expressed as follows: OBC g=g ¼ ðPellet weight–Original dry weightÞ =Original dry weight
2.7.5.
Nitrite ion absorption capacity of IDF
Nitrite is a reactive ion and can react with secondary amines and amides under acid conditions to form N-nitroso compounds, many of which have been shown to be carcinogenic in animals (Lijinsky, 1984). Nitrite scavenging capacity may be a contributing factor in the possible role of dietary ingredients for protecting against gastric cancer development (Moller, Dahl, & Bockman, 1988). A dried IDF sample (1.0 g) was mixed with 100 mL 1 mol/L NaNO2 solution in a 250-mL conical flask. The pH was adjusted to 2.0 (gastric pH). The mixture was then incubated at 37 1C for 75 min under continuous mild agitation. The residual concentration of nitrite ion was subsequently measured, and nitrite ion absorption capacity was expressed as follows: Nitrite ion absorption capacity ðμg=gÞ ¼ ðNitrite ion before absorption–Nitrite ion after absorptionÞ =Dry weight
2.8.
Preparation of antioxidative components of IDF
An amount of 3.0 g of each Qingke IDF before and after ultrafine grinding was stirred for 1 h in 15 mL n-hexane with a magnetic stirrer at room temperature and filtered. The residues obtained after filtration were dried and then extracted with 80% methanol (30 mL) by stirring for 2 h with a magnetic stirrer. The mixture obtained was filtered and filled up to 100 mL with 80% methanol, and then stored in amber colored sealed glass container at 4 1C until further antioxidant analyses.
2.9.
Determination of antioxidant activities
2.9.1.
DPPH free radical scavenging capacity assay
The DPPH radical scavenging capacity of Qingke IDF was evaluated according to the method of Xu and Chang (2007) with slight modifications. DPPH radicals have a maximum absorption at 515 nm, which discolors with addition of antioxidants. The DPPH solution in methanol (6 10 5 M) was prepared freshly, and 3 mL of this solution was mixed with 100 μL of the sample extract in methanol. The mixture was incubated for 20 min at 37 1C in a water bath, and then the decrease in absorbance at 515 nm was measured (AS). A blank containing 100 μL of methanol in the DPPH solution was prepared daily, and its absorbance was measured (AB). The experiment was carried out in triplicate. The free radical scavenging activity was calculated using the following formula: % inhibition ¼ ½ðAS – AB Þ=AB 100 where AB ¼ Absorbance of the blank, and AS ¼Absorbance of sample.
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
2.9.2.
Ferric reducing antioxidant power (FRAP) assay
The FRAP is a simple, inexpensive test that may offer a putative index of antioxidant activity. This method is based on the reduction, at low pH, of a colorless ferric complex (Fe3þ-tripyridyltriazine) to a blue-colored ferrous complex (Fe2þ-tripyridyltriazine) by the action of electron-donating antioxidants. The reduction is monitored by measuring the change of absorbance at 593 nm. The working FRAP reagent was prepared daily by mixing 10 volumes of 300 mM acetate buffer, pH 3.6, with 1 volume of 10 mM TPTZ in 40 mM hydrochloric acid and with 1 volume of 20 mM ferric chloride. A standard curve was prepared using various concentrations of FeSO4 7H2O. All solutions were used on the day of preparation. One hundred microliters of sample solutions and 300 μL of deionized water were added to 3 mL of freshly prepared FRAP reagent. The reaction mixture was incubated for 30 min at 37 1C in a water bath. Then, the absorbance of the samples was measured at 593 nm. A blank reading using acetate buffer was also taken. The difference between sample absorbance and blank absorbance was calculated and used to calculate the FARP value. The reducing capacity of the sample tested was calculated with reference to the reaction signal given by a Fe2þ solution. FRAP values were expressed as mmol Fe2þ/100 g of sample. All measurements were done in triplicate (Xu & Chang, 2007).
2.10.
173
Statistical analysis
All results in this study were expressed as mean7standard deviation of three replicates. The data were also analyzed in triplicate by one-way analysis of variance using SPSS 11.5 software package for Windows (SPSS Inc, U.S.A.), to identify differences among means.
3.
Results and discussion
3.1.
Particle size of Qingke DF after ultrafine grinding
Fig. 2 – Particle size distribution of Qingke DF after ultrafine grinding (The abscissa is the diameter (μm) of the particle size; the ordinates q% (quantity %) is the particle size distribution, and Q% is under size %.).
3.2.
As shown in Table 1, the moisture content of Qingke flour is 11.5%, and the TDF content of Qingke was 13.6%. SDF was increased from 3.79% to 6.63%, while IDF decreased from 9.76% to 7.64% after ultrafine grinding, suggesting that ultrafine grinding converts fiber components of the TDF fraction into a more soluble form. The DF are generally classified as soluble (oligosaccharides, pectins, β-glucans, and galactomanan gums alginate, psyllium fiber) or insoluble fractions (cellulose, hemicellulose, and lignin), based on their solubility in water (Kale, Pai, Hamaker, & Campanella, 2011). Soluble fiber can help to lower blood cholesterol and regulate blood glucose levels. Several studies indicate that SDF is more important than IDF in many health aspects (Galisteo, Duarte, & Zarzuelo, 2008; Vasanthan, Gaosong, Yeung, & Li, 2002). It is also an interesting challenge to change IDF into SDF. In this context, the observation that the SDF content of Qingke DF becomes higher, points to the usefulness of employing micronization techniques to enhance the nutritional quality of DF components in cereal grains.
3.3.
The particle size of Qingke DF after ultrafine grinding was distributed in a range from 2.97 μm to 39.23 μm with a mean particle size of 11.74 μm, which belongs to the submicron scale (Fig. 2). Instead, the mean particle size of Qingke DF before ultrafine grinding was 172.49 μm. The results showed that pulverization by the mini-type airflow pulverization instrument could effectively reduce the sizes of the DF particles to a submicron scale. These results were in accordance with our previous study in which the mean particle size of wine grape pomace DF was 7.06 μm using the same mini-type airflow pulverization instrument (Zhu et al., 2014a). Moreover, Zhu et al. (2010) reported the smaller particle size of ultrafine wheat bran DF was obtained using multidimensional swing high-energy nano-ball-milling. The particle size of the ultrafine DF in the latter study was 343.5 nm. It can be speculated that the different particle sizes obtained depend on the nature of the material, the grinding treatments and the experimental instruments used for micronization.
Chemical analyses
Physicochemical properties of Qingke IDF
The WHC, WRC, swelling capacity, OBC and nitrite ion absorption capacity were measured before and after ultrafine grinding. As shown in Table 2, the WHC of Qingke DF significantly decreased after ultrafine grinding. Such finding is in agreement with the results obtained by Zhu et al. (2010), who suggested that the WHC of wheat bran DF decreased from 5.89 to 3.45 g/g after the ultrafine grinding treatment. WHC is related to the porous matrix structure formed by polysaccharide chains which can hold large amounts of water through hydrogen bonding (Kethireddipalli, Hung, Phillips, & McWatters, 2002). In contrast, Zhao, Yang, Gai, & Yang, (2009) had reported that the smaller particle size of ginger powder was associated with higher WHC even when their particle sizes decreased to 7.23–8.32 μm. It was explained that micronization would expose more surface area, polar groups and other water-binding sites to the surrounding water medium. In addition, WHC of DF is strongly related to the source of the DF (Foschia et al., 2013). The swelling capacity, OBC and nitrite ion absorption capacity of Qingke DF increased after
174
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
Table 1 – Effect of ultrafine grinding on dietary fiber content in Qingke flour*. Treatments
TDF (%)
SDF (%)
IDF (%)
IDF:SDF
Regular grinding Ultrafine grinding
13.5570.61a 14.2770.76a
3.7970.22a 6.6370.35b
9.7670.64b 7.6470.53a
2.57 1.15
n
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05).
Table 2 – Effect of ultrafine grinding on physicochemical properties of Qingke IDF*. Treatments Regular grinding Ultrafine grinding n
WHC (g/g) b
4.4270.39 3.1970.07a
WRC (g/g) a
4.7370.45 4.8370.51a
Swelling capacity (mL/g) a
OBC (g/g)
Nitrite ion absorption capacity (μg/g) a
0.9570.01 1.2870.02b
0.9670.02 1.2170.01b
835.00717a 940.00712b
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05). WHC, water holding capacity; WRC, water retention capacity; OBC, oil binding capacity.
Table 3 – Effect of ultrafine grinding on DPPH scavenging activity and FRAP of Qingke IDF*. Treatments
DPPH free radical scavenging activity (%)
FRAP (mmol Fe2þ/100 g)
Regular grinding Ultrafine grinding
38.1972.21a 47.5473.08b
86.6977.65a 125.3778.28b
n
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05). FRAP, ferric reducing antioxidant power.
ultrafine grinding. According to Raghavendra et al. (2004) the swelling capacity of coconut DFs was increased when its particle size was reduced from 1127 to 550 μm. Instead, Sangnark and Noomhorm (2003) reported that the smaller particle size of sugarcane bagasse DF was associated with lower OBC. It might be then argued that the contradictory observations made in different studies concerning these physical properties might reflect differences in the experimental parameters (e.g. stirring), which can alter the physical structure of fibers (Sangnark & Noomhorm, 2003). The WRC of Qingke DF was not altered by the micronization of the sample (Table 2).
3.4.
Antioxidant activities of Qingke IDF
The DPPH and FRAP values for Qingke IDF before and after ultrafine grinding were determined. As indicated in Table 3, the FRAP value increased after ultrafine grinding. The increase of FRAP might originate from the ultrafine grinding treatment which alters the fiber matrix, thus causing some phenolics linked or embedded in a compact structure to be related or exposed. There were some other reports pointing to similar observations. Zhu et al. (2010) revealed that the TPC and FRAP of wheat bran DF increased after ultrafine grinding. The DPPH radical scavenging activity also increased after ultrafine grinding. In another study, the DPPH and FRAP of buckwheat hull IDF increased after ultrafine grinding (Zhu et al., 2014a). Instead, Zhu, Du, Li, and Li, (2014b) reported that
wine grape pomace DF after ultrafine grinding had decreased DPPH radical scavenging activity.
4.
Conclusions
Ultrafine grinding of Qingke IDF has brought about significance changes in the properties of the fiber components, i.e. improved swelling capacity, OBC and nitrite ion absorption capacity. The FRAP and DPPH also increased after ultrafine grinding. Strong correlation was observed between FRAP and DPPH scavenging capacity. The results of this study suggest that a mini-type airflow pulverization instrument could effectively reduce the particle size of Qingke IDF to submicron scale, enhance the solubility of the fiber components and thereby improve the health benefits associated with consumption of SDF. The ultrafine grinding of cereal DF may be a useful processing scheme in any fortification strategy to generate commercial functional products supplemented with DF.
Acknowledgements This research was jointly supported by Natural Science Foundation of Guangdong Province, China (Project code: S2012010008961), and a research grant from Beijing Normal University-Hong Kong Baptist University United International College (Project code: UICRG 201402), China.
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
r e f e r e n c e s
AOAC. (1996). AOAC official method 991.43. Total, soluble, and insoluble dietary fiber in foods. Washington, DC: Association of Official Analytical Chemists. AOAC. (2000). AOAC official method 925.10. (Total) and moisture in flour air oven method. Washington, DC. Association of Official Analytical Chemists. AOAC. (2005). AOAC official method 985.29. Total Dietary Fiber in Foods. Washington, DC: Association of Official Analytical Chemists. Chen, H. D., Weiss, J. C., & Shahidi, F. (2006). Nanotechnology in nutraceuticals and functional foods. Food Technology, 60, 30–36. Eshak, E. S., Iso, H., Date, C., Kikuchi, S., Watanabe, Y., & Wada, Y. (2010). Dietary fiber intake is associated with reduced risk of mortality from cardiovascular disease among Japanese men and women. Journal of Nutrition, 140, 1445–1453. Foschia, M., Peressini, D., Sensidoni, A., & Brennan, C. S. (2013). The effects of dietary fiber addition on the quality of common cereal products. Journal of Cereal Science, 58, 216–227. Galisteo, M., Duarte, J., & Zarzuelo, A. (2008). Effects of dietary fibers on disturbances clustered in the metabolic syndrome. Journal of Nutritional Biochemistry, 19, 71–84. Han, Z. X., Qian, G., Wu, F., Pan, Z. F., Deng, G. B., & Yu, M. Q. (2008). Sequences variation and classification of B-hordein genes in hull-less barley from the Qinghai-Tibet Plateau. Molecular Biology, 1, 63–70. Isken, F., Klaus, S., Osterhoff, M., Pfeiffer, A. F. H., & Weickert, M. O. (2010). Effects of long-term soluble vs. insoluble dietary fiber intake on high-fat diet induced obesity in C57BL/6J mice. Journal of Nutritional Biochemistry, 21, 278–284. Kale, M., Pai, D., Hamaker, B., & Campanella, O. (2011). Incorporation of fibers in food: A food engineering challenge. Food engineering interfaces (pp. 69–98)New York, NY: Springer Press69–98. Kethireddipalli, P., Hung, Y. C., Phillips, R. D., & McWatters, K. H. (2002). Evaluating the role of cell material and soluble protein in the functionality of cowpea (Vigna unguiculata) pastes. Journal of Food Science, 67, 53–59. Kim, Y. I. (2000). AGA technical review: Impact of dietary fiber on colon cancer occurrence. Gastroenterology, 118, 1235–1257. Lijinsky, W. (1984). Structure-activity relations in carcinogenesis by N-nitroso compounds. Genotoxicology of N-nitroso compounds (p. 189)New York, NY: Plenum Press189. Luan, Y. F., & He, Y. (2004). Tendency and counter measures on breed improvement of Tibet highland barley. Barley Science, 12, 1–4 (In Chinese). Moller, M. E., Dahl, R., & Bockman, O. C. (1988). A possible role of the dietary fibre product, wheat bran, as a nitrite scavenger. Food Chemistry and Toxicology, 26, 841–845. Nimazhaxi. (1998). Hull-less barley and food safety in the region of plateau. Tibetan Agricultural Technology, 20, 20–25 (In Chinese).
175
Park, S. I., Jiang, Y., Simonsen, J., & Zhao, Y. (2009). Feasibility of creating compression-molded biocomposite boards from berry fruit pomaces. Journal of Applied Polymer Science, 115, 127–136. Raghavendra, S. N., Rastogi, N. K., Raghavarao, K. S. M. S., & Tharanathan, R. N. (2004). Dietary fiber from coconut residue: Effects of different treatments and particle size on the hydration properties. European Food Research and Technology, 218, 563–567. Robertson, J. A., Monredon, F. D., Dysseler, P., Guillon, F., Amado, R., & Thibault, J. Y. (2000). Hydration properties of dietary fiber and resistant starch: A European collaborative study. LWT— Food Science and Technology, 33, 72–79. Rosa, N. N., Barron, C., Gaiani, C., Dufour, C., & Micard, V. (2013). Ultra-fine grinding increases the antioxidant capacity of wheat bran. Journal of Cereal Science, 57, 84–90. Sangnark, A., & Noomhorm, A. (2003). Effect of particle sizes on functional properties of dietary fiber prepared from sugarcane bagasse. Food Chemistry, 80, 221–229. Thomason, W. E., Brooks, W. S., Griffey, C. A., & Vaughn, M. E. (2009). Hulless barley seeding rate effects on grain yield and yield components. Crop Science, 49, 342–346. Vasanthan, T., Gaosong, J., Yeung, J., & Li, J. (2002). Dietary fiber profile of barley flour as affected by extrusion cooking. Food Chemistry, 77, 35–40. Xu, B. J., & Chang, S. K. C. (2007). A comprartive study on phenolic profiles and antioxidant activities of legumes as affected by extraction solvents. Journal of Food Science, 72, S159–S166. Yang, L., Christensen, D. A., Mckinnon, J. J., Beattie, A. D., & Yu, P. Q. (2013). Effect of altered carbohydrate traits in hulless barley (Hordeum vulgare L.) on nutrient profiles and availability and nitrogen to energy synchronization. Journal of Cereal Science, 58, 182–190. Zhao, X. Y., Yang, Z. B., Gai, G. S., & Yang, Y. F. (2009). Effect of superfine grinding on properties of ginger powder. Journal of Food Engineering, 91, 217–222. Zhu, K. X., Huang, S., Peng, W., Qian, H. F., & Zhou, H. M. (2010). Effect of ultrafine grinding on hydration and antioxidant properties of wheat bran dietary fiber. Food Research International, 43, 943–948. Zhu, F. M., Du, B., & Li, J. (2014a). Effect of ultrafine grinding on physicochemical and antioxidant properties of dietary fiber from wine grape pomace. Food Science and Technology International, 20, 55–62. Zhu, F. M., Du, B., Li, R. F., & Li, J. (2014b). Effect of micronization technology on functional and antioxidant properties of dietary fiber from buckwheat hulls. Biocatalysis and Agricultural Biotechnology, 3, 30–34.
Available online at www.sciencedirect.com
www.elsevier.com/locate/bcdf
Physicochemical and antioxidant properties of dietary fibers from Qingke (hull-less barley) flour as affected by ultrafine grinding Bin Dua,b,c, Fengmei Zhua, Baojun Xuc,n,1 a
Hebei Normal University of Science and Technology, Qinhuangdao 066600, Hebei, China School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China c Food Science and Technology Program, Beijing Normal University—Hong Kong Baptist University United International College, Zhuhai 519085, Guangdong, China b
ar t ic l e in f o
abs tra ct
Article history:
The effect of particle size of Qingke flour and particle size of dietary fiber (DF) on
Received 27 March 2014
physicochemical and antioxidant capacities of DF was investigated. Qingke and extracted
Received in revised form
DF were ground by regular and ultrafine grinding and their particle sizes were determined
27 July 2014
using laser diffraction method. The results indicated that ultrafine grinding could
Accepted 20 September 2014
effectively pulverize DF particles to submicron scale; the particle size distribution was close to a Gaussian distribution. The soluble DF in Qingke flour was increased significantly
Keywords:
after ultrafine grinding. With the decrease of particle size, the water holding capacity
Qingke
(WHC) of Qingke DF was reduced (po0.05), while the swelling capacity, oil binding capacity
Dietary fiber
(OBC), and nitrite ion absorption capacity were increased (po0.05), and the water retention
Superfine grinding
capacity (WRC) had no significant change. The antioxidant activities of Qingke DF were
Hydration properties
increased after ultrafine grinding. Micronized insoluble DF showed increased DPPH radical scavenging activity and ferric reducing antioxidant power. & 2014 Elsevier Ltd. All rights reserved.
1.
Introduction
Dietary fiber (DF) is involved in disease prevention and enhanced health of consumers. In particular, soluble components of DF have several physicochemical functions (such as increased water binding and alteration of the food matrix viscosity) which in turn contribute to physiological attenuations such as cholesterol and fat binding, decrease in blood glucose levels, preventing constipation and facilitating good colonic health (Foschia, Peressini, Sensidoni, & Brennan, 2013). It has been proved that intake of diet containing high DF is negatively related to the incidence rate of chronic diseases, such as n
obesity, diabetes mellitus, large bowel cancer, cardiovascular disease, colonic diverticulitis and constipation (Eshak et al., 2010; Isken, Klaus, Osterhoff, Pfeiffer, & Weickert, 2010; Kim, 2000). Nowadays, the average worldwide ingestion of DF is still considerably lower than the recommended daily intake levels. So, it is necessary to add DF to food products. DFs have been extensively studied for their ability to regulate transit time due to the increase of stool bulk, and other beneficial properties such as hydration properties like swelling, water-holding and water retention capacities (Robertson et al., 2000). Growing attention has been paid to Qingke (Hordeum vulgare L. var. nudum Hook. f) due to its specific attributes,
Corresponding author. Tel.: +86 756 3620636; fax: +86 756 3620882. E-mail address: [email protected] (B. Xu). 1 Present address: Baojun Xu, 28, Jinfeng Road, Tangjiawan, Zhuhai 519085, Guangdong, China.
http://dx.doi.org/10.1016/j.bcdf.2014.09.003 2212-6198/& 2014 Elsevier Ltd. All rights reserved.
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Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
such as high beta-glucan content, high total DF content, highfeeding value (animal nutrition), and high-malt quality. The health benefits of DF have been widely recognized. Qingke, also called hull-less barley, differs from regular hulled barley cultivars, as it is a barley line with fewer hulls to cover the caryopsis (Han et al. 2008; Thomason, Brooks, Griffey, & Vaughn, 2009). Qingke is the main staple food crop in Qinghai-Tibet Plateau, China. Hull-less barley with low amylose and high β-glucan is used as an essential food crop for human consumption, as a brewing material and as an important feed source (Nimazhaxi, 1998; Luan & He, 2004; Yang, Christensen, Mckinnon, Beattie, and Yu, 2013). Ultrafine grinding technology is an emerging technology showing great potential in nutraceuticals and functional foods manufacture for human health improvement (Chen, Weiss, & Shahidi, 2006). Constituents in ultrafine powders are easily absorbed during digestion in the GI track of humans, and this may have an impact on improving the quality and safety of food products and positively influencing human health. Although the effect of ultrafine grinding on antioxidant properties of wheat bran DF (Zhu, Huang, Peng, Qian, & Zhou, 2010) and wine grape pomace DF (Zhu, Du, & Li, 2014a) have been published, the use of ultrafine grinding in DF processing remains rather limited. Probably due to the toughness and polymeric nature of DF in various plant materials, as well as rather inadequate equipment support for production of ultrafine powders (Zhu et al., 2010). Since the reduction of particle size would substantially increase the particle surface area and cause the release of some antioxidant compounds (Rosa, Barron, Gaiani, Dufour, & Micard, 2013), it is valuable to examine how hydration and antioxidant properties of DF are affected by ultrafine grinding. The objective of this study was to evaluate the application of ultrafine grinding technology for producing Qingke DF in the submicron range and to investigate the effects of ultrafine grinding on the physicochemical and antioxidant properties of insoluble DF from Qingke.
2.3. Preparation of insoluble dietary fiber (IDF) before ultrafine grinding IDF before ultrafine grinding was prepared from Qingke flour using the procedure described by Park, Jiang, Simonsen, and Zhao (2009) with minor modifications. Briefly, Qingke flour (100 g, 0.42 mm) was sonicated in pH 6.0 water (2000 mL) at 20 1C for 20 min. α-Amylase (2000 U/g) (1 g) was added, and the mixture was incubated at 60 1C for 3.5 h. Protease (200,000 U/g) (0.5 g) was added, and the mixture was incubated at 55 1C for 3 h. Finally, the residue was washed with cold water and dried at 50 1C overnight in a vacuum oven to yield a fraction denoted as Qinke IDF.
2.4. Preparation of Qingke flour and IDF with ultrafine grinding Qingke flour and IDF were further micronized by a mini-type airflow pulverization instrument (QLM-80 K, Shangyu City Heli Powder Engineering Co., Ltd., Zhejiang, China). The working pressure was set at 70 Mpa, and the working frequency was set at 40 Hz. Qingke flour and IDF after ultrafine grinding were sealed in aluminum foil containers and kept in a desiccator for further study. The whole flow chart of material processing in this study is elucidated in Fig. 1.
2.5. Determination of DF content in Qingke flours from regular and ultrafine grinding The moisture content, total dietary fiber (TDF), IDF and soluble dietary fiber (SDF) contents in flours were determined using the respective AOAC methods (AOAC, 2000, 2005, 1996).
Qingke
Regular grinding
Qingke wholegrain flour
2.
Materials and methods
2.1.
Materials and chemicals
Blue Qingke (Dulihuang) was purchased from Qinghai Xinlvkang Food Co., Ltd. (Qinghai, China) originating from the 2012 crop year. Phosphate-buffered saline (PBS, pH 7.0), α-amylase, and protease were purchased from Beijing Aoboxing Biotechnology Co., Ltd. (Beijing, China). Gallic acid, 1,1-diphenyl-2picrylhydrazyl (DPPH), 2,4,6-tri (2-pyridyl)-s-triazine (TPTZ) were purchased from National Standard Samples Center (Beijing, China). All other reagents were of analytical grade.
2.2.
Extraction
Insoluble dietary fiber (IDF) Ultrafine grinding (UFG) UFG flour
UFG IDF
Preparation of Qingke flour with regular milling
Qingke flour was ground by a regular laboratory mill (FZ102, Tianjin Taisite Co. Ltd., Tianjin, China), and passed through a 40-mesh (0.42 mm) screen.
Physicochemical properties
Antioxidant properties
Fig. 1 – Flow chart for the study on Qingke flour and IDF.
172
2.6.
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
Particle size measurement of Qingke DF
A laser diffraction particle size analyzer (LA-920, Horiba Limited, Japan) was employed for the determination of primary particle size distribution. The samples (Qingke flour and IDF) were suspended in ethanol directly in the measurement cell (small volume unit sample module) and the suspensions were analyzed when the obscuration was between 70 and 80%.
2.7.
Hydration properties of IDF
2.7.1.
Water-holding capacity (WHC) of IDF
WHC is defined by the quantity of water that is bound to the fibers without the application of any external force (except for gravity and atmospheric pressure). Accurately weighed dried IDF (1.0 g) was loaded into a graduated test tube, around 30 mL of water was added and it was hydrated for 18 h. The supernatant was subsequently removed by passing through a sintered glass crucible (G4) under vacuum. The hydrated weight of IDF was recorded, and it was dried at 105 1C for two hr to obtain the residual dry weight (Raghavendra, Rastogi, Raghavarao, & Tharanathan, 2004). WHC g=g ¼ ðHydrated weight–Dry weightÞ=Dry weight
2.7.2.
Water retention capacity (WRC) of IDF
WRC is defined as the quantity of water that remains bound to the hydrated fiber following the application of an external force (pressure or centrifugation). Accurately weighed dried IDF (1.0 g) was loaded into a graduated centrifugal tube, 30 mL of water was added and the sample was allowed to hydrate for 18 h. Following centrifugation at 3000 g for 20 min, the supernatant was removed by passing through a sintered glass crucible (G4) under vacuum. The hydrated weight was recorded, and then sample was dried at 105 1C for 2 h to obtain its dry weight (Raghavendra et al., 2004). WRC g=g ¼ ðHydrated weight after centrifugation–Dry weightÞ =Dry weight
2.7.3.
Swelling capacity of IDF
Swelling property is defined as the ratio of the volume occupied when the sample is immersed in excess of water after equilibration to the actual weight. Accurately weighed dried IDF (0.2 g) was placed in a graduated test tube, around 10 mL of water was added, and IDF was allowed to hydrate for 18 h. The final volume attained by the sample was measured after 18 h (Raghavendra et al., 2004). SwellingcapacityðmL=gÞ ¼ Volume occupied by sample =Original sample weight
2.7.4.
Oil-binding capacity (OBC) of IDF
OBC was determined by the method of Sangnark and Noomhorm (2003) with slight modifications. A dried IDF (5.0 g) was mixed with peanut oil in a centrifugal tube and left for 1 h at room temperature (25 1C). The mixture was then centrifuged at 1500 g for 10 min, the supernatant was decanted and the pellet was recovered by filtration through
a nylon mesh. OBC was expressed as follows: OBC g=g ¼ ðPellet weight–Original dry weightÞ =Original dry weight
2.7.5.
Nitrite ion absorption capacity of IDF
Nitrite is a reactive ion and can react with secondary amines and amides under acid conditions to form N-nitroso compounds, many of which have been shown to be carcinogenic in animals (Lijinsky, 1984). Nitrite scavenging capacity may be a contributing factor in the possible role of dietary ingredients for protecting against gastric cancer development (Moller, Dahl, & Bockman, 1988). A dried IDF sample (1.0 g) was mixed with 100 mL 1 mol/L NaNO2 solution in a 250-mL conical flask. The pH was adjusted to 2.0 (gastric pH). The mixture was then incubated at 37 1C for 75 min under continuous mild agitation. The residual concentration of nitrite ion was subsequently measured, and nitrite ion absorption capacity was expressed as follows: Nitrite ion absorption capacity ðμg=gÞ ¼ ðNitrite ion before absorption–Nitrite ion after absorptionÞ =Dry weight
2.8.
Preparation of antioxidative components of IDF
An amount of 3.0 g of each Qingke IDF before and after ultrafine grinding was stirred for 1 h in 15 mL n-hexane with a magnetic stirrer at room temperature and filtered. The residues obtained after filtration were dried and then extracted with 80% methanol (30 mL) by stirring for 2 h with a magnetic stirrer. The mixture obtained was filtered and filled up to 100 mL with 80% methanol, and then stored in amber colored sealed glass container at 4 1C until further antioxidant analyses.
2.9.
Determination of antioxidant activities
2.9.1.
DPPH free radical scavenging capacity assay
The DPPH radical scavenging capacity of Qingke IDF was evaluated according to the method of Xu and Chang (2007) with slight modifications. DPPH radicals have a maximum absorption at 515 nm, which discolors with addition of antioxidants. The DPPH solution in methanol (6 10 5 M) was prepared freshly, and 3 mL of this solution was mixed with 100 μL of the sample extract in methanol. The mixture was incubated for 20 min at 37 1C in a water bath, and then the decrease in absorbance at 515 nm was measured (AS). A blank containing 100 μL of methanol in the DPPH solution was prepared daily, and its absorbance was measured (AB). The experiment was carried out in triplicate. The free radical scavenging activity was calculated using the following formula: % inhibition ¼ ½ðAS – AB Þ=AB 100 where AB ¼ Absorbance of the blank, and AS ¼Absorbance of sample.
Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
2.9.2.
Ferric reducing antioxidant power (FRAP) assay
The FRAP is a simple, inexpensive test that may offer a putative index of antioxidant activity. This method is based on the reduction, at low pH, of a colorless ferric complex (Fe3þ-tripyridyltriazine) to a blue-colored ferrous complex (Fe2þ-tripyridyltriazine) by the action of electron-donating antioxidants. The reduction is monitored by measuring the change of absorbance at 593 nm. The working FRAP reagent was prepared daily by mixing 10 volumes of 300 mM acetate buffer, pH 3.6, with 1 volume of 10 mM TPTZ in 40 mM hydrochloric acid and with 1 volume of 20 mM ferric chloride. A standard curve was prepared using various concentrations of FeSO4 7H2O. All solutions were used on the day of preparation. One hundred microliters of sample solutions and 300 μL of deionized water were added to 3 mL of freshly prepared FRAP reagent. The reaction mixture was incubated for 30 min at 37 1C in a water bath. Then, the absorbance of the samples was measured at 593 nm. A blank reading using acetate buffer was also taken. The difference between sample absorbance and blank absorbance was calculated and used to calculate the FARP value. The reducing capacity of the sample tested was calculated with reference to the reaction signal given by a Fe2þ solution. FRAP values were expressed as mmol Fe2þ/100 g of sample. All measurements were done in triplicate (Xu & Chang, 2007).
2.10.
173
Statistical analysis
All results in this study were expressed as mean7standard deviation of three replicates. The data were also analyzed in triplicate by one-way analysis of variance using SPSS 11.5 software package for Windows (SPSS Inc, U.S.A.), to identify differences among means.
3.
Results and discussion
3.1.
Particle size of Qingke DF after ultrafine grinding
Fig. 2 – Particle size distribution of Qingke DF after ultrafine grinding (The abscissa is the diameter (μm) of the particle size; the ordinates q% (quantity %) is the particle size distribution, and Q% is under size %.).
3.2.
As shown in Table 1, the moisture content of Qingke flour is 11.5%, and the TDF content of Qingke was 13.6%. SDF was increased from 3.79% to 6.63%, while IDF decreased from 9.76% to 7.64% after ultrafine grinding, suggesting that ultrafine grinding converts fiber components of the TDF fraction into a more soluble form. The DF are generally classified as soluble (oligosaccharides, pectins, β-glucans, and galactomanan gums alginate, psyllium fiber) or insoluble fractions (cellulose, hemicellulose, and lignin), based on their solubility in water (Kale, Pai, Hamaker, & Campanella, 2011). Soluble fiber can help to lower blood cholesterol and regulate blood glucose levels. Several studies indicate that SDF is more important than IDF in many health aspects (Galisteo, Duarte, & Zarzuelo, 2008; Vasanthan, Gaosong, Yeung, & Li, 2002). It is also an interesting challenge to change IDF into SDF. In this context, the observation that the SDF content of Qingke DF becomes higher, points to the usefulness of employing micronization techniques to enhance the nutritional quality of DF components in cereal grains.
3.3.
The particle size of Qingke DF after ultrafine grinding was distributed in a range from 2.97 μm to 39.23 μm with a mean particle size of 11.74 μm, which belongs to the submicron scale (Fig. 2). Instead, the mean particle size of Qingke DF before ultrafine grinding was 172.49 μm. The results showed that pulverization by the mini-type airflow pulverization instrument could effectively reduce the sizes of the DF particles to a submicron scale. These results were in accordance with our previous study in which the mean particle size of wine grape pomace DF was 7.06 μm using the same mini-type airflow pulverization instrument (Zhu et al., 2014a). Moreover, Zhu et al. (2010) reported the smaller particle size of ultrafine wheat bran DF was obtained using multidimensional swing high-energy nano-ball-milling. The particle size of the ultrafine DF in the latter study was 343.5 nm. It can be speculated that the different particle sizes obtained depend on the nature of the material, the grinding treatments and the experimental instruments used for micronization.
Chemical analyses
Physicochemical properties of Qingke IDF
The WHC, WRC, swelling capacity, OBC and nitrite ion absorption capacity were measured before and after ultrafine grinding. As shown in Table 2, the WHC of Qingke DF significantly decreased after ultrafine grinding. Such finding is in agreement with the results obtained by Zhu et al. (2010), who suggested that the WHC of wheat bran DF decreased from 5.89 to 3.45 g/g after the ultrafine grinding treatment. WHC is related to the porous matrix structure formed by polysaccharide chains which can hold large amounts of water through hydrogen bonding (Kethireddipalli, Hung, Phillips, & McWatters, 2002). In contrast, Zhao, Yang, Gai, & Yang, (2009) had reported that the smaller particle size of ginger powder was associated with higher WHC even when their particle sizes decreased to 7.23–8.32 μm. It was explained that micronization would expose more surface area, polar groups and other water-binding sites to the surrounding water medium. In addition, WHC of DF is strongly related to the source of the DF (Foschia et al., 2013). The swelling capacity, OBC and nitrite ion absorption capacity of Qingke DF increased after
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Bioactive Carbohydrates and Dietary Fibre 4 (2014) 170 –175
Table 1 – Effect of ultrafine grinding on dietary fiber content in Qingke flour*. Treatments
TDF (%)
SDF (%)
IDF (%)
IDF:SDF
Regular grinding Ultrafine grinding
13.5570.61a 14.2770.76a
3.7970.22a 6.6370.35b
9.7670.64b 7.6470.53a
2.57 1.15
n
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05).
Table 2 – Effect of ultrafine grinding on physicochemical properties of Qingke IDF*. Treatments Regular grinding Ultrafine grinding n
WHC (g/g) b
4.4270.39 3.1970.07a
WRC (g/g) a
4.7370.45 4.8370.51a
Swelling capacity (mL/g) a
OBC (g/g)
Nitrite ion absorption capacity (μg/g) a
0.9570.01 1.2870.02b
0.9670.02 1.2170.01b
835.00717a 940.00712b
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05). WHC, water holding capacity; WRC, water retention capacity; OBC, oil binding capacity.
Table 3 – Effect of ultrafine grinding on DPPH scavenging activity and FRAP of Qingke IDF*. Treatments
DPPH free radical scavenging activity (%)
FRAP (mmol Fe2þ/100 g)
Regular grinding Ultrafine grinding
38.1972.21a 47.5473.08b
86.6977.65a 125.3778.28b
n
Results were expressed as means7standard deviation (n ¼ 3). Values in the same column with different letters are significantly different (po0.05). FRAP, ferric reducing antioxidant power.
ultrafine grinding. According to Raghavendra et al. (2004) the swelling capacity of coconut DFs was increased when its particle size was reduced from 1127 to 550 μm. Instead, Sangnark and Noomhorm (2003) reported that the smaller particle size of sugarcane bagasse DF was associated with lower OBC. It might be then argued that the contradictory observations made in different studies concerning these physical properties might reflect differences in the experimental parameters (e.g. stirring), which can alter the physical structure of fibers (Sangnark & Noomhorm, 2003). The WRC of Qingke DF was not altered by the micronization of the sample (Table 2).
3.4.
Antioxidant activities of Qingke IDF
The DPPH and FRAP values for Qingke IDF before and after ultrafine grinding were determined. As indicated in Table 3, the FRAP value increased after ultrafine grinding. The increase of FRAP might originate from the ultrafine grinding treatment which alters the fiber matrix, thus causing some phenolics linked or embedded in a compact structure to be related or exposed. There were some other reports pointing to similar observations. Zhu et al. (2010) revealed that the TPC and FRAP of wheat bran DF increased after ultrafine grinding. The DPPH radical scavenging activity also increased after ultrafine grinding. In another study, the DPPH and FRAP of buckwheat hull IDF increased after ultrafine grinding (Zhu et al., 2014a). Instead, Zhu, Du, Li, and Li, (2014b) reported that
wine grape pomace DF after ultrafine grinding had decreased DPPH radical scavenging activity.
4.
Conclusions
Ultrafine grinding of Qingke IDF has brought about significance changes in the properties of the fiber components, i.e. improved swelling capacity, OBC and nitrite ion absorption capacity. The FRAP and DPPH also increased after ultrafine grinding. Strong correlation was observed between FRAP and DPPH scavenging capacity. The results of this study suggest that a mini-type airflow pulverization instrument could effectively reduce the particle size of Qingke IDF to submicron scale, enhance the solubility of the fiber components and thereby improve the health benefits associated with consumption of SDF. The ultrafine grinding of cereal DF may be a useful processing scheme in any fortification strategy to generate commercial functional products supplemented with DF.
Acknowledgements This research was jointly supported by Natural Science Foundation of Guangdong Province, China (Project code: S2012010008961), and a research grant from Beijing Normal University-Hong Kong Baptist University United International College (Project code: UICRG 201402), China.
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r e f e r e n c e s
AOAC. (1996). AOAC official method 991.43. Total, soluble, and insoluble dietary fiber in foods. Washington, DC: Association of Official Analytical Chemists. AOAC. (2000). AOAC official method 925.10. (Total) and moisture in flour air oven method. Washington, DC. Association of Official Analytical Chemists. AOAC. (2005). AOAC official method 985.29. Total Dietary Fiber in Foods. Washington, DC: Association of Official Analytical Chemists. Chen, H. D., Weiss, J. C., & Shahidi, F. (2006). Nanotechnology in nutraceuticals and functional foods. Food Technology, 60, 30–36. Eshak, E. S., Iso, H., Date, C., Kikuchi, S., Watanabe, Y., & Wada, Y. (2010). Dietary fiber intake is associated with reduced risk of mortality from cardiovascular disease among Japanese men and women. Journal of Nutrition, 140, 1445–1453. Foschia, M., Peressini, D., Sensidoni, A., & Brennan, C. S. (2013). The effects of dietary fiber addition on the quality of common cereal products. Journal of Cereal Science, 58, 216–227. Galisteo, M., Duarte, J., & Zarzuelo, A. (2008). Effects of dietary fibers on disturbances clustered in the metabolic syndrome. Journal of Nutritional Biochemistry, 19, 71–84. Han, Z. X., Qian, G., Wu, F., Pan, Z. F., Deng, G. B., & Yu, M. Q. (2008). Sequences variation and classification of B-hordein genes in hull-less barley from the Qinghai-Tibet Plateau. Molecular Biology, 1, 63–70. Isken, F., Klaus, S., Osterhoff, M., Pfeiffer, A. F. H., & Weickert, M. O. (2010). Effects of long-term soluble vs. insoluble dietary fiber intake on high-fat diet induced obesity in C57BL/6J mice. Journal of Nutritional Biochemistry, 21, 278–284. Kale, M., Pai, D., Hamaker, B., & Campanella, O. (2011). Incorporation of fibers in food: A food engineering challenge. Food engineering interfaces (pp. 69–98)New York, NY: Springer Press69–98. Kethireddipalli, P., Hung, Y. C., Phillips, R. D., & McWatters, K. H. (2002). Evaluating the role of cell material and soluble protein in the functionality of cowpea (Vigna unguiculata) pastes. Journal of Food Science, 67, 53–59. Kim, Y. I. (2000). AGA technical review: Impact of dietary fiber on colon cancer occurrence. Gastroenterology, 118, 1235–1257. Lijinsky, W. (1984). Structure-activity relations in carcinogenesis by N-nitroso compounds. Genotoxicology of N-nitroso compounds (p. 189)New York, NY: Plenum Press189. Luan, Y. F., & He, Y. (2004). Tendency and counter measures on breed improvement of Tibet highland barley. Barley Science, 12, 1–4 (In Chinese). Moller, M. E., Dahl, R., & Bockman, O. C. (1988). A possible role of the dietary fibre product, wheat bran, as a nitrite scavenger. Food Chemistry and Toxicology, 26, 841–845. Nimazhaxi. (1998). Hull-less barley and food safety in the region of plateau. Tibetan Agricultural Technology, 20, 20–25 (In Chinese).
175
Park, S. I., Jiang, Y., Simonsen, J., & Zhao, Y. (2009). Feasibility of creating compression-molded biocomposite boards from berry fruit pomaces. Journal of Applied Polymer Science, 115, 127–136. Raghavendra, S. N., Rastogi, N. K., Raghavarao, K. S. M. S., & Tharanathan, R. N. (2004). Dietary fiber from coconut residue: Effects of different treatments and particle size on the hydration properties. European Food Research and Technology, 218, 563–567. Robertson, J. A., Monredon, F. D., Dysseler, P., Guillon, F., Amado, R., & Thibault, J. Y. (2000). Hydration properties of dietary fiber and resistant starch: A European collaborative study. LWT— Food Science and Technology, 33, 72–79. Rosa, N. N., Barron, C., Gaiani, C., Dufour, C., & Micard, V. (2013). Ultra-fine grinding increases the antioxidant capacity of wheat bran. Journal of Cereal Science, 57, 84–90. Sangnark, A., & Noomhorm, A. (2003). Effect of particle sizes on functional properties of dietary fiber prepared from sugarcane bagasse. Food Chemistry, 80, 221–229. Thomason, W. E., Brooks, W. S., Griffey, C. A., & Vaughn, M. E. (2009). Hulless barley seeding rate effects on grain yield and yield components. Crop Science, 49, 342–346. Vasanthan, T., Gaosong, J., Yeung, J., & Li, J. (2002). Dietary fiber profile of barley flour as affected by extrusion cooking. Food Chemistry, 77, 35–40. Xu, B. J., & Chang, S. K. C. (2007). A comprartive study on phenolic profiles and antioxidant activities of legumes as affected by extraction solvents. Journal of Food Science, 72, S159–S166. Yang, L., Christensen, D. A., Mckinnon, J. J., Beattie, A. D., & Yu, P. Q. (2013). Effect of altered carbohydrate traits in hulless barley (Hordeum vulgare L.) on nutrient profiles and availability and nitrogen to energy synchronization. Journal of Cereal Science, 58, 182–190. Zhao, X. Y., Yang, Z. B., Gai, G. S., & Yang, Y. F. (2009). Effect of superfine grinding on properties of ginger powder. Journal of Food Engineering, 91, 217–222. Zhu, K. X., Huang, S., Peng, W., Qian, H. F., & Zhou, H. M. (2010). Effect of ultrafine grinding on hydration and antioxidant properties of wheat bran dietary fiber. Food Research International, 43, 943–948. Zhu, F. M., Du, B., & Li, J. (2014a). Effect of ultrafine grinding on physicochemical and antioxidant properties of dietary fiber from wine grape pomace. Food Science and Technology International, 20, 55–62. Zhu, F. M., Du, B., Li, R. F., & Li, J. (2014b). Effect of micronization technology on functional and antioxidant properties of dietary fiber from buckwheat hulls. Biocatalysis and Agricultural Biotechnology, 3, 30–34.