PARTICLE SIZE EFFECT ON SOY PROTEIN ISOLATE EXTRACTION

This study was undertaken to determine if the yield and purity of soy protein isolates could be improved by changing the particle size of the starting raw material. Soy protein isolates were extracted from hexane defatted soy flour ground to three different average particle sizes (89.5 ± 1.1, 184.2 ± 1.6 and 223.4 ± 6.4 µm). By decreasing the average particle diameter of the starting raw material (soy flour) from 223.4 to 89.5 µm the total solids recovery increased from 23 to 32% (P = 0.00008), while the protein recovery increased from 40 to 52% (P = 0.00004). Final protein content (i.e., purity) of the soy protein isolates was not significantly impacted by average particle size. The results clearly demonstrated that protein recovery can be increased by >30% by decreasing the average particle size of the starting raw material (i.e., defatted soy flour), without having any detrimental impact on the purity of the final soy protein isolate.     

EFFECTS OF SOY PROTEIN AND FREEZING TREATMENTS ON COOKING LOSS AND COMPOSITION OF BEEF PATTIES

All-beef and soy-extended patties were frozen to −18°C in either 24, 48, 72 or 96h and stored at −23, −18 or −7°C for 6, 9, 12, 18 or 24 months. The addition of soy resulted in a substantial reduction in cooking loss for patties cooked from the frozen state with a greater retention of moisture in cooked patties. Freezing reduced cooking loss for soy-extended patties, but increased cooking loss for all-beef patties. Faster freezing (-18°C in 24 h vs. −18°C in 96 h) reduced cooking loss and produced higher moisture values in all-beef patties. Patties stored at –7°C lost more moisture during cooking. Increased frozen storage time had a minimal effect on cooking losses, moisture and fat levels. Where it is essential for frozen patties to sustain minimal cooking losses with maximal moisture in cooked patties, the inclusion of soy protein concentrate, faster freezing, and storage at –18°C or colder are suggested.     

EFFECT OF SOY PROTEIN ISOLATE AND SOY FIBER ON COLOR, PHYSICAL AND SENSORY CHARACTERISTICS OF BAKED PRODUCTS

Quick breads were formulated to contain 0%, 40%, 50% or 60% Soy Protein Isolate and Fiber (SPI/Fiber), and yeast breads were formulated to contain 0%, 14%, 21% or 28% SPI/Fiber replacement for wheat flour. Physical and sensory data were collected. As SPI/fiber level increased, muffin batter specific gravity, baked product air cell number, Instron peak force to compress by 75%, a value, beany flavor, grain-like flavor, aftertaste, moistness and denseness increased while muffin peak height at the crown, baked volume, L and b values, hue angle, sweetness and crumbliness decreased. There were significant negative correlations between increased level of SPI/fiber in muffins and acceptability of flavor and texture, as well as willingness to purchase or purchase the product at a higher price. As SPI/fiber level increased, bread dough pH after fermentation, air cell number, Instron peak force to compress by 75%, a and b values, beany flavor, grain-like flavor, and aftertaste increased while loaf volume, peak height at the crown, L value, hue angle, cohesiveness and crumbliness decreased. There were significant negative correlation coefficients between level of SPI/fiber and acceptability of flavor and texture, as well as willingness to purchase the product or to purchase it at a higher price.     

混合条件对大豆蛋白塑料特性的影响

研究了高速混合机混合，捏合，研磨和粉碎机混合4种不同混合方式，及不同混合时间对大豆蛋白生物降解塑料机械特性和吸水率的影响。结果表明采用研磨混合方式大豆蛋白塑料具有最大拉伸强度、伸长率及最小吸水率，其值分别为4．50MPa、309％、145％和170％；研磨时间为25min时，大豆蛋白塑料拉伸强度最大，伸长率及吸水率最小，分别为5．30MPa、220％、143％和206％。     

HEAT INDUCED GELS FROM PARTIALLY HYDROLYZED SOY PROTEIN ISOLATE1

Heat induced gels can be obtained from partially hydrolyzed soy protein isolate (HSPI). The gel forming ability of each of the HSPI fractions (peptides of varying molecular weight and solubility) were studied, after being separated by preparative Sephadex gel filtration chromatography. The insoluble peptide fraction had no gel forming ability. Peptides larger than 5,000 Daltons, those lower than 5,000 Daltons and a fraction of the very hydrophobic peptides formed weak gels when heated alone. Interactions between several peptide fractions were necessary in order to yield a gel with the strength of the one formed by whole HSPI. A mechanism explaining (1) the action of the proteolytic enzyme in breaking down the protein and (2) the peptide interaction needed for the gel formation, is proposed.     

凝胶多糖与大豆分离蛋白可食性复合膜的制备

以凝胶多糖和大豆分离蛋白作为成膜基材，添加甘油作为增塑剂，研制了一种可食性复合膜，并通过红外光谱谱图初步探讨了复合膜的成膜机理。正交优化实验结果表明：在干燥温度50℃、大豆分离蛋白浓度2％、凝胶多糖浓度1.2％、甘油浓度1％条件下，所得膜具有较好的抗拉强度和阻湿性能。     

EFFECTS OF SOY PROTEIN ISOLATES ON QUALITY OF CHOCOLATES DURING STORAGE

The effect of soy protein isolate (SPI) on oxidation rate, changes in color and hardness, and microbiological aspect of chocolates during storage were studied. The Peroxide Value (PV) of the control and 5% showed SPI were highest in week 3 and decreased at the following week, while 10% SPI showed the lowest PV in week 10 as compared to the others. The Anisidine Value (AV) of all chocolates showed an increasing pattern during 10 weeks of storage. The Total Oxidation Value (TV) of all chocolates was found to be highest at week 3 and lowest at week 10 when 10% SPI was used. During storage, all chocolates slightly increased in hardness and turned darker in color. The Total Plate Count (TPC) of the control and SPI chocolates was less than 1,000 colonies/g.     

EFFECTS OF PROCESSING ON ADSORPTION OF OFF-FLAVORS ONTO SOY PROTEIN1

Heats of adsorption and adsorption coefficients for the reversible adsorption of several aliphatic alcohols, aldehydes, and ketones on soy protein were measured using gas chromatography. The physical state of protein samples was changed by heating at 100°C and 121°C at moisture contents of 29%and 40%. A comparison was made with values for untreated soy isolate and sheared soy isolate, and the effects of moisture, temperature, and their interaction were examined by analysis of variance. Heats of adsorption were unchanged, but changes in adsorption coefficients of the treated samples demonstrated a significant decrease in binding that can be attributed to protein denaturation. The response depended on the interaction of moisture and temperature effects.     

大豆不同脱腥方法对豆乳中蛋白质含量及脱腥效果影响的研究

大豆在加工过程中所产生的豆腥味是研究开发新的蛋白食品的主要障碍。在众多的脱腥专利技术中,结合热处理钝化大豆中的脂肪氧化酶是广为采用而较为有效的方法。由于热处理虽则使豆乳风味及口感有明显改善,但也程度不同地降低了大豆蛋白的可溶性,影响了大豆蛋白的得率。本文就几种行之有效的脱腥方法进行了比较,并对豆乳中蛋白质的影响规律作了某些探讨。     

EFFECTS OF ACETYLATION ON PHYSICOCHEMICAL PROPERTIES OF J1S SOY PROTEIN

Acetylation of ε-amino groups of lysine residues changed conformation of glycinin isolated from soybean, the extent of which depended upon the degree of modification. Soy glycinin with lysine residue modifications of 0%, 28%, 65%, 85%, and 95% were used for the experiment. Accessibility of tyrosine and tryptophan residues, which were shown to increase as modification percent increased, were detected using uv absorption spectra and fluorescence spectra, respectively. Surface hydrophobicity was found to increase more than two times over native glycinin, when lysine residues were excessively modified to above 95%. Masking of charged lysine residues, exposure of hydrophobic interior, and subunit dissociation should have contributed to the increase. Enthalpy, as obtained from differential scanning calorimetry, dropped from 3.6 callg native protein to 0 callg protein, when lysine residues were acetylated above 65%. implicating complete denaturation. The hydrolytic rates, using α-chymotrypsin, increased initially, then decreased at more than 65% lysine modification.     

ULTRASTRUCTURE OF SOY PROTEIN FIBERS FRACTURED BY VARIOUS TEXTURE MEASURING DEVICES

Abstract. Spun soy fibers fractured by the tensile test, Warner-Bratzler shear, Kramer Shear Press and a modified Volodkevich wedge were examined with the scanning electron microscope. Fracture in the tensile test occurred almost always at a macrocavity, the weakest point in the fiber. Warner-Bratzler shear induced compression and flow at the zone of rupture, but not as markedly as in the case of the modified Volodkevich wedge. Fracture by the Kramer Shear Press was the closest to pure shear. Some of the exposed fracture surfaces revealed internal structures in the fibers such as macrocavities and distinct skin and core sections. The mechanism of rupture by these tests was more complex than expected.     

POTENTIAL FOR UTILIZING 11S SOY GLOBULAR PROTEIN TO STUDY TEXTURE FORMATION1

A corn meal based model food system was successfully utilized in experiments designed to measure the influence of protein type on product integrity. The food systems were processed using either a capillary rheometer or an extrusion capillary rheometer to produce the texturized product. The Warner-Bratzler Shear test and the Ottawa texture measuring tests were utilized to indicate product integrity. The purified 11S soy protein produced a product with greater integrity as measured by maximum shear value than an equivalent amount of soy protein isolate from which it was derived.