大豆蛋白营养品质和生理功能研究进展

本文综述了大豆蛋白营养品质和生理功能研究进展。蛋白消化率正后的氨基酸得分（ＰＤＣＡＡＳ）是一种新的、更准确的评价蛋白质营养品质的方法的指标;大豆蛋白ＰＤＣＡＡＳ值为满分（１,０）,表明大豆蛋白是完全蛋白质,可满足２岁以上人体对各种必需氨基酸的需求;临床研究表明,大豆蛋白可显著降低ＬＤＬ胆固醇浓度,而对ＨＤＬ胆固醇浓度有一定程度的提高作用;与其他优质蛋白相比,大豆蛋白有利于钙的代谢;用大豆蛋白代替膳     

响应面优化大豆蛋白降粘工艺的研究

通过试验选取温度、pH和BaCl2浓度作为Box - Behnken设计的变量,利用响应面法分析得到大豆蛋白降粘的优化条件.结果表明:大豆蛋白降粘的适宜参数为温度42℃、pH4.2、BaCl2浓度1.2%,在此条件下,大豆蛋白的粘度可降低至29.3 mPa·s,与空白样相比降粘率可达95.4%.     

大豆蛋白肽降血脂功能性的研究

通过动物实验运用统计分析技术对大豆蛋白肽进行了降血脂功能研究。结果表明，大豆蛋白肽显著降低血清胆固醇的效应，主要表现在升高高密度脂蛋白胆固醇(HDL-C)，而对低密度脂蛋白胆固醇(LDL-C)有降低作用。     

热聚集大豆蛋白分子量分布及其与κ-卡拉胶相行为的研究

制备了不同的热聚集大豆蛋白,并采用体积排阻色谱(SEC-HPLC)对其分子量分布进行了表征.结果表明:热处理后的大豆蛋白主要由聚集体、中间体和未聚集部分组成,聚集体比例随加热时蛋白浓度的增加而增加.选取5%和1%大豆蛋白热聚集体和κ-卡拉胶对蛋白质-多糖的相行为进一步研究,结果蛋白浓度不同发生明显的宏观相分离所需的卡拉胶的浓度不同,5%大豆蛋白热聚集体和κ-卡拉胶的混合体系具有较窄的均相区域,表明蛋白质粒子的大小影响其与多糖的相分离行为.     

木瓜蛋白酶水解大豆分离蛋白研究

本文研究了木瓜蛋白酶对大豆分离蛋白的有限水解作用。分析了酶浓度，反应时间，温度，底物浓度，半胱氨酸，异Vc钠，亚硫酸钠浓度等因素对大豆蛋白水解作用的影响。试验得出木瓜蛋白酶水解大豆分离蛋白的较佳条件是酶浓度为8000U/g底物，反应时间150-200min，温度50℃，大豆蛋白浓度为4.5%-8%，半胱氨酸浓度0.25%。     

脲变性大豆蛋白的流变学特性研究

采用可编程控制式旋转粘度计(Brookfield RVDV-II+/SSA-SCL27),系统、定量的研究了10 wt%的分离大豆蛋白溶液经2-10 mol·L-1尿素变性处理后流变学特性.为大豆蛋白的开发应用提供理论基础.结果表明:变性前大豆蛋白水溶液呈Bingham型特征,脲变性的大豆蛋白溶液属于典型的假塑性流体;脲变性大豆蛋门溶液的表观粘度随剪切速率和温度的增大而减小、随脲浓度增大而增加;在脲浓度4～6 mol·L-1时浓度变化最明显;变性后溶液的非牛顿指数虽然增大,20℃时从0.17增加至0.3～0.4,但仍较小,所以,溶液的流动稳定性差.     

乙酸甲酯对大豆蛋白胶胶膜快干性的影响

提出了大豆蛋白胶胶膜概念,通过单因素试验研究了乙酸甲酯对大豆蛋白胶胶膜快干性及胶膜胶合强度的影响.结果表明:乙酸甲酯可以显著提高胶膜的快干性,且随着添加量的增加而增快,综合考虑乙酸甲酯大豆蛋白胶膜的干燥速率及胶合强度的影响,100 g大豆蛋白胶添加15 mL乙酸甲酯为最适添加量.     

乙醇改性大豆蛋白制豆胶的研究

研究乙醇改性大豆蛋白对木材用豆胶的胶粘性能的影响.乙醇可使大豆蛋白发生部分变性,使蛋白分子中疏水性基团暴露出来,以提高豆胶的耐水性.通过正交试验优化出最佳条件:乙醇浓度30%,蛋白与水质量比1:9、改性时间45 min、改性温度75℃.将上述最佳条件下制得的豆胶施在胡桃木样品上,经三个循环的48 h水浸泡和48 h空气干燥后剪切强度由未浸泡前的81.6 MPa降至73.9 MPa,仅下降了9.4%.结果表明:乙醇改性后的豆胶的粘接强度和耐水性都有所提高.     

大豆蛋白肽加工工艺技术概述

大豆蛋白肽比等量的氨基酸具有更高的生物活性和营养价值，具有降低胆固醇，降低血脂，降血压，预防癌症，心脏病等功能，有很大的开发利用价值。本文主要就大豆蛋白肽的几种生产方法进行了阐述，旨在为大豆蛋白肽的工业化生产提供参考。     

酶法提高大豆分离蛋白酸溶性的研究

通过单因素试验研究了植酸酶添加量、酶解时间、pH、温度和料液浓度对大豆蛋白酸溶度、透光率和料液粘度的影响,在单因素试验的基础上对pH、温度、料液浓度和时间进行四因素三水平的正交试验,结果表明,当植酸酶添加量为0.6%时,酶解的最佳条件组合为pH3.0,温度40℃,料液浓度10%,酶解时间45 min,此时大豆分离蛋白的酸溶度为45.79%,透光率为68.5%,与优化前相比,分别提高了30.65%和29.4%。     

Influence of dietary soybean trypsin inhibitors and DL-ethionine on sulfur amino acid adequacy of diets for young rats

Weanling male Wistar rats were fed 20% protein diets based on casein or either of two combinations of soy protein isolate and ground raw soy providing three levels of soybean trypsin inhibitors (SBTI; 0,448 and 808 mg of trypsin inhibited per 100g of diet respectively). DL-ethionine was included at three levels (0,0.05% and 0.10%) with each level of SBTI. After 4, 8 and 12 weeks ofad libitum feeding, diets containing SBTI without DL-ethionine were associated with decreases in weight gain, feed efficiency, serum cholesterol and serum urea nitrogen. Higher levels of triglycerides, glutamate pyruvate transaminase (SGPT) and altered serum free amino acid levels were also found. Increased dietary levels of DL-ethionine also resulted in deficits in growth and feed efficiency, decreased serum cholesterol, increased SGPT and similar alterations in serum free amino acids. Combination of dietary SBTI with DL-ethionine resulted in even greater growth deficits and serum cholesterol decreases as well as increases in SGPT and serum triglycerides and changes in serum free amino acid levels. Methionine deficiency in the young rats fed SBTI and DL-ethionine was indicated by the changes in serum amino acids and growth deficits. Moderation of some effects over the 12 week test period suggested decreased methionine requirements in the older rats.     

The cholesterol-lowering property of soybeans fed to rats is related to the fasting duration

Numerous factors affect plasma cholesterol and, therefore, representpotential interferences with the specific effects of diet on lipid metabolism.After casein intake, serum cholesterol levels depend on many experimentalconditions in rats, such as the type of casein, the presence or absence ofcholesterol in the diet, the age and strain of rat, the diet composition, thenutritional status. The effect of fasting duration on selected parameters wasstudied in adult male Wistar rats fed a 20% casein and 1% cholesterol-based diet. No changes were observed in total serum, lipoproteins-B andHDL cholesterol and in triglyceride values after an 8 h-fast compared tonon-fasted animals. A significant decrease was induced in total andlipoproteins-B cholesterol with a 12 h-fast. A prolonged fast resulted ina significant decrease in these parameters and in triglycerides and inHDL-cholesterol levels.Fasted animals fed heated soybean meal instead of casein did not display amarked decrease in serum lipids. It appeared that the fasting effect wasmore marked in animals fed casein than in animals fed soybeans. Theseresults showed the importance of experimental conditions such as nutritional status ofanimals when blood samples are taken in studies of the hypocholesterolemiceffect of soy protein compared to casein.     

Effect of full-fat or defatted rice bran on serum cholesterol

Rice bran has been shown to lower serum cholesterol in hamsters. Leghorn cockerel chicks were fed 60% full-fat rice bran (FFRB) and corn/soy (CS) diets with 0.5% added cholesterol. Both diets contained 19% protein. All reported parameters are on blood serum. Significant differences (p<0.05) were found in total cholesterol (TC), triglycerides (TG), high-density and low-density lipoprotein cholesterol (HDL and LDL). In a second study, chicks were fed FFRB, defatted rice bran (DFRB), and CS diets balanced for 18% protein, 14.47% total dietary fiber and 10.78% lipid with 0.5% added cholesterol. Both TC and TG were significantly lower (p<0.05) in chicks fed FFRB and CS diets. Significant differences were found in HDL values for all diets with FFRB exhibiting the highest mean value (155 mg/dl) and CS exhibiting the lowest mean value (114 mg/dl). All diets were significantly different (p<0.05) in LDL, with mean values of 249, 318 and 275 mg/dl for FFRB, DFRB and CS, respectively. FFRB appears to increase HDL and to lower LDL in chicks, but does not always affect TC, whereas DFRB may increase all three serum lipid components.Contribution No. 2575, Montana Agricultural Experiment Station in cooperation with Western Regional Research Center, USDA.     

The effects of low calorie diet with soy protein on cardiovascular risk factors in hyperlipidemic patients

Serum lipid abnormalities are an established risk factor for cardiovascular disease in hyperlipidemic patients. Because of the side effect of long-term medications in these patients, soy protein, as a part of healthy diet, may improve their lipid profile. The purpose of this study was to determine the effect of soy protein with low-calorie diet on lipid profiles in hyperlipidemic patient. Fifty two hyperlipidemic patients of both sex and age range of 25-65 years were participated. The patients received low-calorie diet based on 1400 kcal energy 18% protein, 24% fat and 58% carbohydrate per day for 4 weeks. The treatment group received low-calorie diet including (30 g day(-1)) of soy protein. Blood samples were obtained after an overnight (12 h) fasting period before the study and in the last day of the intervention period. Anthropometric indices and levels of serum triacylglycerol, total cholesterol, low-density lipoprotein and high-density lipoprotein were measured before and after the intervention. In groups, weight, body mass index, waist and hip circumferences were significantly reduced (p<0.05) after four weeks. In comparison with control group, the results of treatment of soy protein with low-calorie diet showed that at the end of 4th week serum low-density lipoprotein was significantly (p<0.05) decreased while an insignificant reduction was seen in total cholesterol. This study suggest that soy protein with low calorie diet for 4 weeks treatment may be safe and effective alternative therapy for diminished the cardiovascular risk factors in hyperlipidemic patients.     

The influence of four dietary proteins and sodium phytate on the metabolism of cholesterol and the lipoproteins in rat

The hypocholesterolemic effect of dietary proteins could not be related to their vegetal or animal origin and seemed correlated to their different amino acids proportions. Comparing rats fed soy protein diet to those fed casein diet for 45 days, we observed a decrease of serum HDL cholesterol levels. Furthermore sequential centrifugation showed a decrease of HDL_2–3 fraction and especially apolipoprotein E in the serum of soy protein fed rats. The sodium phytate, added to the diet, did not change the metabolism of sterols.     

Coconut kernel protein modifies the effect of coconut oil on serum lipids

Feeding coconut kernel along with coconut oil in human volunteers has been found to reduce serum total and LDL cholesterol when compared to feeding coconut oil alone. This effect of the kernel was also observed in rats. Since many plant proteins have been reported to exert a cholesterol lowering effect, a study was carried out on the effect of isolated kernel protein in rats. Feeding kernel protein resulted in lower levels of cholesterol, phospholipids and triglycerides in the serum and most tissues when compared to casein fed animals. Rats fed kernel protein had (1) increased hepatic degradation of cholesterol to bile acids, (2) increased hepatic cholesterol biosynthesis, and (3) decreased esterification of free cholesterol. In the intestine, however, cholesterogenesis was decreased. The kernel protein also caused decreased lipogenesis in the liver and intestine. This beneficial effect of the kernel protein is attributed to its very low lysine/arginine ratio 2.13% lysine and 24.5% arginine.     

Coconut kernel protein modifies the effect of coconut oil on serum lipids.

Feeding coconut kernel along with coconut oil in human volunteers has been found to reduce serum total and LDL cholesterol when compared to feeding coconut oil alone. This effect of the kernel was also observed in rats. Since many plant proteins have been reported to exert a cholesterol lowering effect, a study was carried out on the effect of isolated kernel protein in rats. Feeding kernel protein resulted in lower levels of cholesterol, phospholipids and triglycerides in the serum and most tissues when compared to casein fed animals. Rats fed kernel protein had (1) increased hepatic degradation of cholesterol to bile acids, (2) increased hepatic cholesterol biosynthesis, and (3) decreased esterification of free cholesterol. In the intestine, however, cholesterogenesis was decreased. The kernel protein also caused decreased lipogenesis in the liver and intestine. This beneficial effect of the kernel protein is attributed to its very low lysine/arginine ratio 2.13% lysine and 24.5% arginine.     

Partial replacement of dietary casein with soy protein isolate can reduce the severity of retinoid-induced hypertriglyceridemia

Previous research carried out in an animal model of retinoid-induced hypertriglyceridemia – rats fet a 13-cis retinoic acid (13cRA)-containing diet having casein as the protein source – has demonstrated that the complete replacement of dietary casein with soy protein isolate (SPI) can decrease the severity of this condition. In this study, the effect of partially replacing dietary casein with SPI was investigated. Five groups of male Fischer 344 rats were used in a 14-day study, with two groups being fed diets having casein as the protein source, without or with 13cRA (groups A and B, respectively), and three groups being fed 13cRA-containing diets in which SPI was used to bring about the isonitrogenous replacement of 25, 50, or 100% of the casein in the formula for the diet used for group B (groups C-E, respectively). Serum triglyceride concentration for group B was significantly different ( p < 0.05) from that of groups A, D, and E (5.41 vs 2.62, 4.04, and 2.66 mmol/l, respectively). Serum cholesterol concentrations for groups D and E were significantly lower ( p < 0.05) than for groups A and B (1.63 and 1.60 vs 2.00 and 2.14 mmol/l, respectively). Thus, the isonitrogenous replacement of 50% of dietary casein with SPI can reduce the severity of retinoid-induced hypertriglyceridemia while decreasing the serum concentration of cholesterol.     

大豆功能肽的研究进展

大豆功能肽是以大豆分离蛋白或者豆粕为原料酶解生成的具有生理功能的小分子量肽类。大豆功能肽的分子量小、溶解性好,在食品工业中的广泛应用。并且,具有降低血清胆固醇、降低血压、消除疲劳作用和抗氧化等许多活性作用。本文对大豆功能肽的特性、制备方法以及生物学活性等方面进行综述。