Effects of enzymatic/alkali protein removal and particle size reduction on physicochemical and functional characteristics of okara dietary fibre

The combined effects of enzymatic/alkali protein removal treatments and superfine grinding on the characteristics of okara dietary fibre (DF) were investigated. Protein removal could effectively increase the obtained DF content and further enhance water-holding capacity (WHC), swelling capacity (SC) and oil-holding capacity (OHC). The DF with Alcalase treatment and superfine grind through 500-μm mesh size had the highest total dietary fibre, WHC (12.5 g g⁻¹), SC (12.7 mL g⁻¹) and OHC (2.7 g g⁻¹). Decreasing particle size will trigger a redistribution of some fibre composition from the insoluble to the soluble fraction. The WHC and SC of the sieved DFs decreased with reducing mesh size (500–40 µm). The OHC of DF with Flavourzyme treatment reduced with decreasing mesh size (500–100 µm), but improved with mesh size less than 100 µm.     

Wet grinding characteristics of soybean for soymilk extraction

Wet grinding of hydrated soybean was carried out with mixer grinder, stone grinder and colloid mill which revealed that particle size had a profound effect on the protein recovery in the extracted milk with a maximum recovery of 89.3%. Greater reduction in particle size was achieved with mixer grinder (180 μm) with 5 min of grinding while reduction was not significant beyond 18 min (233 μm) in stone grinder. Specific energy consumption in colloid mill was only one-fourth of the mixer grinder while stone grinder required twice the energy. Although Kick’s, Rittinger’s and Bond’s laws could not be applied for total grinding duration, all the three classical laws were found suitable after the initial grain break-up period (2 min). Temperature and duration of thermal treatment given during hot extraction influenced protein recovery and viscosity of soymilk. The results suggest that colloid mill is a potential device for industrial scale operation.     

The effects of okara on rat growth, cecal fermentation, and serum lipids

Okara, a soymilk residue, was characterized and used as a supplement to enrich dietary fiber in rats. Okara comprised 49% total dietary fiber, of which only 0.55% was soluble, protein (33.4%), fat (19.8%), and ash (3.5%). Okara as a diet supplement had no influence on food intake, but the growth rate and feeding efficiency were lower in the okara-fed group than in the control group. Okara increased fecal weight and moisture. In okara-fed rats, in vivo colonic fermentation of okara resulted in a lower pH, but a higher cecal weight and higher total short chain fatty acid production, compared to controls. There were no significant differences (P≤0.05) between groups in albumin, protein, uric acid, bilirubin, or glucose content in rat serum. The okara-supplemented diet produced a nonsignificant reduction in HDL-lipids and triglycerides. Okara, a rich source of low-cost dietary fiber and protein, might be effective as a dietary weight-loss supplement with potential prebiotic effect.     

Soybean seeds and its by-product okara as sources of dietary fibre. Measurement by AOAC and Englyst methods

The composition of soybean seeds and its by-product okara has been studied in this work. Dietary fibre was analysed by Englyst et al. method, by enzymatic–gravimetric methods of AOAC and by the quantification of the monomers obtained from the AOAC residues after acid hydrolysis (AOAC plus hydrolysis). Total dietary fibre by the enzymatic–gravimetric methods of AOAC in okara (55.48 g/100 g dry matter) is more than twice that of soybean seeds (24.37 g/100 g dry matter). The proportion IF/SF is 11 in okara and 6 in soybean seeds. Dietary fibre results from enzymatic–gravimetric AOAC methods are higher in okara and soybean seed samples than those from the Englyst method (okara: 41.14 g/100 g dry matter; soybean seeds: 15.05 g/100 g dry matter), and AOAC plus hydrolysis (okara: 44.91 g/100 g dry matter; soybean seeds: 16.38 g/100 g dry matter). In the case of the insoluble fibre from both samples, AOAC plus hydrolysis gives significantly (p < 0.001) higher values than the Englyst method, whilst for soluble fibre the opposite occurs (p < 0.001). The main monomers in soybean seeds and okara fibre are glucose, galactose, uronic acids, arabinose and xylose. The proportion of each monomer is similar in soybean seeds and okara, so the healthy properties of soybean seeds fibre are also claimed for okara.     

Effect of high-fat diets supplemented with okara soybean by-product on lipid profiles of plasma,liver and faeces in Syrian hamsters

The main components of okara, a by-product from soybean, are dietary fibre and protein. In this study we fed okara based diets with different amounts of fibre, protein and isoflavones to determine their effect on the lipid profile in the plasma, liver and faeces of an animal model. Male golden Syrian hamsters were fed high-fat diets supplemented with okara for 3 weeks. The supplemented diets contained 13% or 20% of okara fibre (OK-13 and OK-20), low-protein okara with 13% of fibre (OK1-13), and isoflavone-free okara with 13% of fibre (OK2-13). Okara supplemented diets did not produce significant differences in the feed intake or body weight gain (p > 0.05). The plasma levels of triglycerides, VLDL- plus LDL cholesterol and total cholesterol in hamsters fed OK-20 decreased significantly (p < 0.05) with respect to the 20% control group (C-20). However, no significant differences (p > 0.05) were found in LDL- and HDL-cholesterol plasma levels in all experiments. Total lipids, triglycerides, total and esterified cholesterol concentrations in liver were reduced by OK-20 diet. Regarding the hamsters fed OK-13 diets, the mean values of the total lipid, triglyceride and cholesterol in the plasma and liver decreased as compared to the control (C-13), but the differences were not statistically significant. All of the okara diets assayed increased the faecal excretion of total lipids, triglycerides, free cholesterol and total nitrogen (p < 0.05) compared to their respective controls. Our results suggest that the main components of okara, dietary fibre and protein, could be related with the total lipids and cholesterol decrease in the plasma and liver, as well as with the faecal output increase in high-fat fed hamsters. Okara might play an interesting role in the prevention of hyperlipidemia and could be used as a natural ingredient or supplement for functional food preparation.     

Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk

The influence of soy protein subunit composition on the particle size distribution and solid content of soymilk and various supernatant fractions was investigated. A well-established seed variety (Harovinton), containing all protein subunits, and eleven null soybean genotypes lacking specific glycinin and β-conglycinin subunits were investigated, to determine the effect of protein composition on the physico-chemical characteristic of soymilk. Soymilk made from Harovinton and soybean lines null in glycinin showed significantly higher total solid yields than the other genotypes evaluated. Soymilks prepared from soybeans null for glycinin or lacking glycinin's group I (A₁, A₂) showed a smaller particle size distribution compared to soybean lines containing glycinin. In general, unheated soymilk made from lines having glycinin showed a bimodal size distribution with large particles, with a decrease in the particle size distribution after heating and heating with homogenization. The results of this work will help in the evaluation of breeding lines with a specific protein composition tailored to a specific processing functionality.     

东北地区大豆主栽品种油份蛋白含量的关联分析

为探寻与大豆油份含量、蛋白含量相关的关键位点,本研究选取中国东北地区92份大豆主栽品种及常用种质资源品种群体基于蛋白含量和油份含量的Meta分析,进行基于数学模型的类群划分评价,估测样本群体的结构,应用简单线性模型分析与大豆油份含量、蛋白含量相关的的位点。结果表明,通过多次迭代测试,当K=5时,即该资源群体可以分为5个亚群时,为最稳定的分类结果,并在显著水平下（p〈0.05）贡献率大于1%的标记中,得到与大豆油份含量相关标记有Sat_412,Sat_195,Satt317,Sat_187,Sat_195,Satt255,Satt713,Satt468,Satt267,Satt686,Sat_294和AZ302047,对油分含量的总贡献率为39.54%。蛋白质含量相关标记有Satt683,Sat_311,Satt578,Satt181,Satt317,Satt700,Satt713,Satt255,Sat_242和Satt720对蛋白质含量总贡献率为48.39%。这些重要的标记位点为大豆油份含量和蛋白含量的分子辅助育种提供重要基础。     

The effect of addition of flaxseed gum on the emulsion properties of soybean protein isolate (SPI)

The effect of addition of flaxseed gum on the emulsion properties of soybean protein isolate (SPI) were investigated in this study. Flaxseed gum with 0.05-0.5% (w/v) concentration was used together with 1% (w/v) SPI to emulsify 10% (v/v) soybean oil. The emulsion was analyzed for emulsion activity (turbidity), stability, particle size, surface charge, and rheological properties. The turbidity and absolute zeta-potential values decreased initially by the addition of flaxseed gum and subsequently increased with further increase in the gum concentration to reach their peak around 0.35% (w/v) gum. The particle size of the emulsion decreased and reached a minimum value at 0.1% (w/v) gum concentration. Any increase in gum concentration beyond this value resulted into increase in the particle size. This study would help to widen the application of SPI and flaxseed gum mixture, and also contribute to the understanding of protein-gum interaction in emulsion.     

Hydration properties,soymilk and okara yield of soybean affected by agronomic factors

The effects of row space and irrigation on 100‐seed weight water uptake, leaching loss, soymilk, and okara yield of soybean were investigated. Row space affected leaching loss, whereas irrigation significantly altered 100‐seed weight, water uptake, volume change, leaching loss, and the soymilk yield of soybeans. Irrigation on the third day resulted in desirable hydration properties. The soymilk yield significantly correlated (p < 0.01 or 0.05) to the hydration properties, e.g., 100‐seed weight, water uptake, volume change, and leaching loss. A predictive regression model (R = 0.860) has been proposed for the soymilk yield.