Emulsifying Capacity and Emulsion Stability of Soy Proteins Compared with Corn Germ Protein Flour

Both emulsifying capacity (EC) and emulsion stability (ES) increased with increasing concentrations from 0.4% to 0.8% of soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) when studied by response surface methodology. EC and ES increased as pH increased from 6 to 8 in all samples. Increasing incubation temperatures of protein solutions from 20–70°C or from 4–20°C did not affect EC or ES, respectively. SF had the highest EC, followd by SI, SC, and CGPF.     

Protein Solubility, Emulsifying Stability and Capacity of Two Defatted Corn Germ Proteins

Functional properties of two corn germ protein (CGP) preparations, defatted with supercritical CO₂ (SC-CO₂) or hexane, were studied using response surface methodology. Temperature of incubation influenced the functionality of both CGP preparations in a model system. Protein solubility was affected by temperature and pH. Higher emulsifying capacity was obtained as pH of CGP in solution was increased. A stable emulsion was formed from 7% SC-CO₂-CGP combined with 40% corn oil. SC-CO₂-CGP had higher protein solubility, emulsifying stability and emulsifying capacity than hexane-CGP. The different functional properties of hexane CGP may be due to the significantly higher fat content in tested preparations.     

Protein Solubility, Water Retention, and Fat Binding of Corn Germ Protein Flour Compared with Milk Proteins

Protein solubility (PS), water retention (WR), and fat binding (FB) of corn germ protein flour (CGPF), nonfat dry milk (NFDM), whey protein concentrate (WPC), and sodium caseinate (SC) were comparatively studied using response surface methodology. PS and WR of all samples were affected by pH except for WR of CGPF. PS and WR of all samples were not affected by incubation temperature except of WR of CGPF. Incubation temperature influenced FB of CGPF and WPC but not of NFDM and SC. Sample concentration significantly affected FB of all samples. CGPF was an effective protein source in terms of WR and FB. For FB, SC > CGPF = NFDM > WPC and for PS, WPC=NFDM=SC > CGPF.     

Corn Germ Protein Flour as an Extender in Broiled Beef Patties

Beef patties were extended at levels of 10, 20, and 30% of the uncooked weight with hydrated defatted corn germ protein flour (CGPF). Extended patties had lower cooking losses and higher cooked yields than control patties. Adding CGPF did not affect moisture or fat contents in broiled patties, but lowered protein content. The amino acid composition of experimental patties was comparable to that of the control. The water-holding capacity and pH of raw patties increased with increasing levels of added CGPF. Incorporation of CGPF affected sensory characteristics of the product; meaty aroma and flavor of all-meat patties was significantly higher than experimental samples and decreased with an increase in added CGPF. CGPF has potential use as an extender in coarsely ground meats.     

Functionality of Wheat Germ Protein in Comminuted Meat Products as Compared with Corn Germ and Soy Proteins

Wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF) were used as additives at a level of 3.5% in comminuted meat products (CMP). Frankfurters with protein additives showed increased water-holding capacity and batter stability and decreased cooking loss. Improved viscosity and adhesiveness were observed with protein additives when the level of added water was constant. Protein additives also influenced textural and sensory properties of frankfurters. WGPF at a level of 3.5% was found similar to effects of SF and CGPF. WGPF is a potential nonmeat protein additive that can be utilized as an extender in CMP such as frankfurters and bologna.     

Emulsifying Capacity and Stability of Goat, Waterbuffalo, Sheep and Cattle Muscle Proteins

All round muscles were excised postmortem from 40 native female young and old goat, waterbuffalo, sheep and cattle carcasses. The age break point between young and old animals was 30 months for cattle and waterbuffalo and 12 months for sheep and goat. Five animals of each species and age were slaughtered in accordance with standard commercial methods. All tissue samples were subsequently analyzed for various chemical (moisture, fat, ash, total proteins, salt soluble protein, moisture/total protein ratio, pH) and physical (emulsion stability, viscosity) properties. The emulsifying and extractable emulsifying capacity of the muscle from each species was determined.     

玉米胚芽蛋白的分离及物化特性研究

采用碱溶酸沉法提取玉米胚芽分离蛋白,利用氨基酸分析和电泳分析胚芽蛋白的氨基酸组成和有效亚基组成。凝胶层析分离玉米胚芽蛋白组分,并对各组分进行热变性温度及圆二色谱分析。氨基酸分析结果表明,玉米胚芽蛋白中谷氨酸和赖氨酸含量较高,其它氨基酸含量较均衡。还原的十二烷基硫酸钠-聚丙烯酰胺电泳(SDS-PAGE)图主要有九条谱带,其分子量依次为87.988、76.320、69.650、53.649、48.546、38.164、34.337、32.294和24.483 kDa。凝胶层析分离获得两个蛋白组分。差示扫描量热仪(DSC)分析表明分离所得两个组分的干粉变性温度分别为97.37℃和98.95℃,圆二色谱(CD)分析表明两个蛋白组分的二级结构主要为β-折叠和无规卷曲。     

Use of Defatted Corn Germ Flour in Pasta Products

Macaroni was produced from commercial durum semolina blended with 10, 20, and 30% defatted corn germ meal. The effect of germ supplementation on chemical composition, physical properties of dough, cooking characteristics, mechanical properties, and panel acceptability of macaroni were studied. Addition of corn germ meal resulted in longer mixing time of the dough, higher farinograph water absorption, higher protein content of the products and improvement of amino acids pattern. Optimum cooking time and percent increase in weight of cooked macaroni decreased with increasing levels of wheat substitution. Enrichment with germ flour had no effect on flavor and texture of conventional macaroni evaluated by taste panels; it greatly affected physical measurements of cooked product texture causing an increase of firmness.     

Wheat Germ Protein Flour Solubility and Water Retention

The effects of pH and temperature on water retention (WR), protein solubility (PS), and total solubility (TS) of defatted wheat germ protein flour (WGPF) were studied in a model system. PS of WGPF was compared with those of corn germ protein flour (CGPF), soy flour (SF), nonfat dried milk (NFDM), and egg white powder (EWP) at 1–8%. WR increased with increase in pH from 4 to 8. Maximum WR occurred at 70°C, and slight variations were observed between 5 and 30°C. PS and TS increased with increases in pH and temperature. PS of proteins was in the order of NFDM > EWP > SF > CGPF=WGPF. The results showed the potential for usage of WGPF in comminuted meats, beef patties, breads, cakes, and cookies.     

6种云南核桃蛋白质乳化性及其乳化稳定性

以6种云南主栽品种核桃为原料,利用碱溶酸沉法提取核桃蛋白质,研究氯化钠浓度、蔗糖浓度、pH值、植物油种类、油相体积、均质转速、水浴温度对不同品种核桃蛋白质乳化性及其乳化稳定性的影响。结果表明：NaCl浓度和蔗糖浓度越低,6种云南核桃蛋白质乳化性和乳化稳定性越好;pH值在等电点附近时,6种云南核桃蛋白质的乳化性最差,乳化稳定性随pH值的升高而增大;同种植物油对不同品种核桃蛋白质的乳化效果影响不同,且同一品种的核桃蛋白质加入不同植物油乳化效果也有差异;油相体积越大,6种云南核桃蛋白质的乳化性及其乳化稳定性越好,均质转速在10 000 r/min时,6种云南核桃蛋白质乳化性及其乳化稳定性差别较小,水浴温度为80℃时,核桃蛋白质的乳化稳定性最好。     

双酶分步水解玉米蛋白粉制备玉米肽干粉的研究

利用碱性蛋白酶和木瓜蛋白酶双酶对玉米蛋白粉进行分步水解,确定制备玉米肽干粉的工艺流程.对双酶分步水解和单酶单独水解进行了蛋白质收率(X)和水解度(DH)的对比分析,同时对不同活性碳浓度对水解液脱色率和氮回收率的影响进行了讨论.     

Interactions Between Lipids and Milk Proteins in Emulsion

The interactions between nitroxide homologs of fatty acids and purified components of milk proteins in a model food emulsion were studied using electron spin resonance. The importance of the interactions in emulsions decreased in the order α_s1-casein > β-lacto-globulin > β-casein β whole casein. α_s1-Casein resulted in a better organization of the lipid monolayer. Neither the flexibility nor the tertiary structure of the proteins explained this result. It appeared that the interactions occurred through lipid polar heads and protein polar side chains due to hydrogen bonds and/or electrostatic interactions.     

Aroma Characteristics of Corn Germ Protein Flours

Eight sensory attributes were established to differentiate aroma characteristics among four kinds of corn germ protein flours (CGPF) processed by treatments to improve flavor quality. The projections of sample and conceptual spaces on a two-dimensional scale reflected aroma differences among samples evaluated by panelists. Volatiles of samples were separated by gas chromatography, and peaks that elicited olfactory responses were recorded as instrumental data. The projections of sample and volatile compound spaces reflected changes of volatiles by treatments. Relationships between sensory and instrumental data were elucidated by superimposing the two spatial maps. In general, treated CGPF samples had less grainy, brown, corn-like and sweet notes than untreated CGPF samples. However, there were more green, musty and chemical notes in the treated CGPF samples.     

Functionality of Defatted Corn Germ Proteins in a Model System: Fat Binding Capacity and Water Retention

Functional properties of two corn germ protein (CGP) preparations, supercritical CO₂ (SC—CO₂) and hexane defatted, were studied in model systems using response surface methodology. The protein preparations had different fat and moisture content. The SC—CO₂ CGP was whiter (1), less red (a) and less yellow (b) in color measurement than hexane CGP. Temperature of incubation influenced the functionality of the SC—CO₂ and hexane-defatted CGP in model system. SC-CO₂ CGP had higher fat binding and water retention than hexane CGP. Fat binding decreased during the heat treatment for SC-CO₂ CGP. Water retention in both preparations increased as temperature increased to 70°C. The different functional properties of hexane CGP may be due to the extent of protein denaturation.     

Factors Affecting Emulsion Capacity as a Measure of Protein Functionality for Nonmeat Proteins

The emulsion capacity (EC) of two commonly used nonmeat proteins, isolated soy protein (ISP) and sodium caseinate (SC), was measured by using a variety of conditions. The EC end point for the different proteins was significantly influenced in different ways by environmental conditions. The end point of the ISP was decreased significantly if sodium chloride was present, if the ISP were added first to water as opposed to oil or if the temperature were increased. The end point of the SC was significantly increased by low sodium chloride levels, unaffected by order of addition to water or oil and was decreased by increasing temperature. Light microscopy demonstrated the structural changes occurring at the EC end points.     

玉米胚芽蛋白新鲜干酪风味物质的研究

将玉米胚芽蛋白和新鲜牛乳按一定的比例混合制作新鲜干酪,可赋予新鲜干酪清新的植物油脂香气。通过干酪成熟过程中NSI含量的分析,确定玉米胚芽蛋白新鲜干酪的成熟期为12d。采用顶空固相微萃取(HS-SPME)吸附并结合气质联用(GC-MS)的方法对干酪成熟过程中的挥发性成分进行分析鉴定,经过HS-SPME/GC-MS分析,成熟后的玉米胚芽蛋白新鲜干酪中含有14.26%的L-丙氨酸乙酯,7.77%的十七酸和7.60%的2,3-丁二酮,比普通新鲜干酪具有更多的奶油香气和植物油脂香气。玉米胚芽蛋白新鲜干酪仅含有一种刺激性气味物质,即辛酸,含量是3.63%,比普通新鲜干酪少。因此添加玉米胚芽蛋白可以改善新鲜干酪风味,赋予其更多的奶香和植物油脂香气。     

Comparison of the Emulsifying Properties of Fish Gelatin and Commercial Milk Proteins

ABSTRACT: We have compared the flocculation, coalescence, and creaming properties of oil-in-water emulsions prepared with fish gelatin as sole emulsifying agent with those of emulsions prepared with sodium caseinate and whey protein. Two milk protein samples were selected from 9 commercial protein samples screened in a preliminary study. Emulsions of 20 vol% n -tetradecane or triglyceride oil were made at pH 6.8 and at different protein/oil ratios. Changes in droplet-size distribution were determined after storage and centrifugation and after treatment with excess surfactant. We have demonstrated the superior emulsifying properties of sodium caseinate, the susceptibility of whey protein emulsions to increasing flocculation on storage, and the coalescence of gelatin emulsions following centrifugation.     

醇法制取玉米胚芽蛋白的工艺

研究了利用脱脂玉米胚芽粉采用醇法制备玉米胚芽蛋白的生产工艺.通过设计单因素试验和响应面分析试验,根据乙醇体积分数、液料比、浸提时间3个因素对蛋白提取率的影响,优化了玉米胚芽蛋白的制备工艺.经单因素试验得出利用玉米胚芽粉制备玉米胚芽蛋白的最佳提取条件为:乙醇体积分数为65％,液料比为10∶1 (mL∶g),温度为45℃,提取时间为1h.响应面优化的结果表明:影响玉米胚芽蛋白提取率的主要因素依次是:料液比、时间、乙醇体积分数;在乙醇体积分数为63.67％,液料比为10.25∶1(mL∶g),温度为45℃,提取时间为1.06h时,玉米胚芽蛋白的蛋白提取率达到最大.在最佳条件下蛋白质提取率可达81.87％,蛋白质质量分数达55.73％.     

Factors Affecting the Emulsifying Capacity of Bovine Muscle and Muscle Proteins

Semitendinosus muscle samples were excised prerigor from 64 crossbred beef animals. Eight animals of each sex condition (bullocks and steers) were slaughtered when they reached age end–points of 8-, 12-12-, 16- and 20-months. The results indicated a significant effect of sex on all hydrometric muscle properties. The values for these traits were generally higher in muscle from bullocks. These differences were especially pronounced in animals 16 months and older. Sex had little effect on muscle pH or the percentages of salt soluble, extractable, and total muscle protein. However, most traits were highly correlated with age. No significant effects of sex regardless of age on emulsifying capacity were noted and many of these traits were unaffected by animal age between 16 and 20 months. Although older animals have less salt soluble protein, its emulsifying capacity is greater and more efficient.