大米肽的酶法制备工艺及其特性的研究

该文利用蛋白酶水解大米蛋白制备得到大米肽。比较碱性蛋白酶、中性蛋白酶、复合蛋白酶和风味酶水解大米蛋白的进程曲线，结果显示碱性蛋白酶的水解效果最好，其较佳作用条件为：底物浓度10%、pH值9.0、温度45℃、酶与底物比48 AU/kg、时间150 min。在此条件下，大米肽的得率为46.8%，纯度为71.3%。大米肽具有溶解性较好和黏度较低的特性，可以在食品中广泛应用。     

大米蛋白的酶水解动力学研究

以米渣为材料,研究碱性蛋白酶、1398中性蛋白酶和木瓜蛋白酶在不同起始pH值、加酶量和温度下水解大米蛋白的进程,建立大米蛋白酶水解动力学方程,为大米蛋白酶水解特性的研究提供依据.在一级化学反应动力学方程基础上,建立了考虑温度、起始pH值和加酶量影响的大米蛋白酶水解动力学模型,该模型可较好的描述不同蛋白酶对大米蛋白的水解进程.木瓜蛋白酶适于在较低的起始pH值下水解,加酶量、起始pH值对其水解进程的影响较大,温度变化对其水解进程的影响较小.1398中性蛋白酶适于在中性条件下水解,加酶量和水解温度对其水解进程的影响程度处于木瓜蛋白酶和碱性蛋白酶之间,起始pH值变化对其水解进程的影响不大.碱性蛋白酶适于在较高pH值下水解,加酶量对其水解进程影响不大,温度的变化对水解进程影响较大.     

酶解制备鱼鳞蛋白降血压肽的工艺优化

为有效利用鱼鳞制备降血压肽,以罗非鱼鱼鳞为原料,在121℃条件下进行热预处理15 min后,运用响应面分析法优化酶解制备鱼鳞蛋白ACE抑制肽的工艺条件。结果表明,以水解度和ACE抑制率为评价指标,筛选出碱性蛋白酶为最优酶。在单因素试验的基础上,根据Box-Behnken中心组合试验设计原理,最终确立最优的酶解工艺参数为:酶解时间2 h、酶解温度56.3℃、pH值8.0,酶底比1.1%,此条件下ACE抑制率理论值为87.95%,实际值为88.26%。最优条件下制得的酶解产物相对分子质量集中在300～3 000 Da之间,水解效果较好。本研究结果对酶解法制备鱼鳞蛋白降血压活性肽具有一定的实践参考价值。     

大米淀粉纯化工艺及其性质的研究

该文采用碱性蛋白酶对碱法制备得到的大米淀粉进行纯化，酶解条件为 pH 9，温度45℃，酶与底物比48 AU/kg，时间60 min。大米淀粉中的蛋白质含量从2.87%降低到0.40%。扫描电镜分析大米淀粉的超微结构显示，碱性蛋白酶纯化处理后的大米淀粉中未见明显的蛋白质颗粒存在。比较纯化前后的大米淀粉发现，大米淀粉经过碱性蛋白酶纯化后，其溶解度和膨润力都明显增加。     

酶解法制备豆粕水解肽工艺优化

为制备苦味低且生物活性高的豆粕水解肽,本试验在综合考虑水解酶酶切位点后选取7种酶组合对低温豆粕进行水解,以蛋白质转化率、水解度、分子量分布及智能感官评价等作为水解肽的评价指标,比较不同酶组合的作用效果。结果表明,优化得到豆粕水解肽的最佳酶法制备工艺条件:复合酶的最佳组合为碱性蛋白酶+中性蛋白酶+脱苦蛋白酶,酶解pH值依次为8.5、7.5、7.5,反应温度保持55℃,反应时间分别为3、2、2 h,经最佳酶组合制得的水解肽水解度为16%,分子量≤1 000 Da的水解肽可达89.8%,制备的水解肽理化性质及口感更优。本研究结果为豆粕资源开发及功能性肽产品的应用奠定了理论基础。     

三文鱼皮四种蛋白酶酶解物抗氧化活性及功能特性的差异研究

为进一步合理开发利用三文鱼皮,本研究对碱性蛋白酶、中性蛋白酶、风味蛋白酶和复合蛋白酶水解所制备三文鱼皮酶解物的抗氧化活性与功能特性进行了比较。结果表明,三文鱼皮碱性蛋白酶酶解物的水解度(20.18%)和三氯乙酸可溶性氮得率(40.14%)最高,小分子肽含量高达99.97%,其抗氧化活性显著优于其他组(P<0.05);且碱性蛋白酶酶解物的溶解性和持水性最高,分别为87.21%和26.92%;中性蛋白酶酶解物的持油性和乳化性能最强,分别为4.67%和14.69%;而风味蛋白酶酶解物的乳化稳定性显著优于其他组(P<0.05)。综上所述,碱性蛋白酶为制备三文鱼皮蛋白抗氧化肽的最优蛋白酶。本研究为三文鱼皮副产物的高值化利用提供了数据支持和理论基础。     

丝胶蛋白抗氧化肽的酶法制备及功能评价

为进一步开发利用废蚕丝,充分挖掘丝胶蛋白的可利用程度,该文研究了6种蛋白酶水解制备丝胶肽及产品的抗氧化活性。筛选出Alcalase碱性蛋白酶为制备丝胶抗氧化肽的理想蛋白酶,并以ABTS体系评价了丝胶肽的抗氧化活性。通过单因素试验研究了反应时间、底物浓度、反应温度、pH值、酶底物比对酶水解制备丝胶肽的影响;并通过回归正交旋转试验设计对水解条件进行优化,建立各因素与水解度和抗氧化活性的数学模型,确定Alcalase酶水解丝胶蛋白的最佳水解条件为:反应时间240min,底物浓度2%,反应温度55℃,pH8.5,酶底物比2.375%。最佳水解条件下水解度为33.35%,ABTS清除活性为43.19%。该研究为开发丝胶抗氧化肽功能产品提供了技术依据。     

挤压法生产淀粉糖浆副产物酶解条件

为实现低值蛋白质资源玉米渣的高质化利用,采用2709碱性蛋白酶,水解挤压法生产淀粉糖浆的副产物玉米渣,确定水解工艺条件.并对水解液中的肽分子质量分布状况及氨基酸组成进行了分析.结果表明,按照本研究工艺路线,采用2709碱性蛋白酶能够较为彻底地水解目标副产物中的蛋白质,水解液中分子质量小于10000 u的水解物大于总量的94.8%,并且绝大部分水解物在二肽、三肽分子质量范围内分布,水解液中含有能够满足人体生理机能需要的多种氨基酸.     

水酶法从菜籽中提取油及水解蛋白的研究

为了同时从菜籽中提取清油和水解蛋白，依次使用复合细胞壁多糖酶和碱性蛋白酶(Alcalase 2.4 L)水解湿磨菜籽浆，并利用大孔吸附树脂纯化水解蛋白液。结果表明：经过酶解(复合细胞壁多糖酶：浓度3％(v/w)，pH 5.0，48℃，5 h；Alcalase 2.4 L：浓度1.5％(v/w)，初始pH 9.0，60℃，3 h)、洗渣和破乳后总菜籽清油提取率为88％～90％，总水解蛋白提取率为93％～95％。和溶剂萃取油相比，水酶法提取油的酸价偏高，颜色略深，但过氧化值低，两者皂化价，碘价和脂肪酸组成均接近。菜籽水解蛋白分子量小于1500的组分约占96％，其中小于600的约占87％。经过大孔吸附树脂纯化后，菜籽肽中糖和灰分含量显著降低，硫苷和植酸均未检出。     

黑豆蛋白肽果汁复合饮料的研制

黑豆是种皮为黑色的大豆，其蛋白质含量高达50%，是极具开发潜力的植物蛋白资源，但黑豆蛋白质分子高度压缩折叠、不易消化，使其加工利用受到了限制。该试验采用2709碱性蛋白酶对黑豆蛋白进行有控制的水解，制备酸溶性好、易消化吸收的黑豆蛋白肽，经水解度与酸溶性蛋白肽得率测定，确定了酶解工艺条件：底物浓度为每100 mL黑豆浆含3.75 g蛋白质，酶-底物比为8 000 u/g，pH值9.0，温度50℃，酶解时间2.0 h，水解度为10%，酸溶性蛋白肽得率达85%。2709蛋白酶对黑豆蛋白具有较好的水解效果，1 kg黑豆经磨浆、酶解与离心去渣脱苦制得20 L黑豆蛋白肽混合液，将其与天然澄清苹果汁按80∶20(V/V)混合调配制备黑豆蛋白肽果汁复合饮料，产品色泽棕红清亮，具天然果汁与黑豆清香风味，蛋白质与肽类物质含量(m/V)≥1.5%，酸度(以柠檬酸计) ≥0.4 g/100 mL。     

Glycosylation and Deamidation of Rice Endosperm Protein for Improved Solubility and Emulsifying Properties

Rice endosperm protein was prepared by alkali-extraction method and subsequently modified by controlled glycosylation (RP_Glu, RP_XG), deamidation (RP_DA), and enzymatic hydrolysis by alcalase (RP_Alc) methods. The RP_Glu and RP_XG were prepared by Maillard type glycosylation with D-glucose and xanthan gum, respectively. The glycosylation improved the emulsion activity (0.721) and stability (26.8 min) of the protein but did not show a substantial improvement in solubility (39.7%). The rice protein modified by controlled alkali-deamidation (RP_DA) showed highest solubility (68%), emulsion activity (0.776), and emulsion stability (24 min) among the three protein modification methods evaluated in this study. The alcalase treatment to 1.8% DH (RP_Alc) slightly improved solubility (33%), emulsion activity (0.468), and emulsion stability (17.5 min) compared with unmodified rice protein (RP), which had 18% solubility, 0.266 emulsion activity, and 14.7 min emulsion stability. The glycosylation and deamidation methods were more effective than the controlled enzymatic hydrolysis by alcalase in improving solubility and emulsifying properties of rice endosperm protein. Glycosylated and deamidated rice endosperm proteins can find application in enhancing emulsifying properties in suitable products.     

Beta-conglycinin embeds active peptides that inhibit lipid accumulation in 3T3-L1 adipocytes in vitro

Obesity is a worldwide health concern because it is a well-recognized predictor of premature mortality. The objective was to identify soybean varieties that have improved potential to inhibit fat accumulation in adipocytes by testing the effects of soy hydrolysates having a range of protein subunit compositions on lipid accumulation and adiponectin expression in 3T3-L1 adipocytes. The results showed that differences in the protein distribution of 15 soy genotypes led to different potentials for the reduction of fat accumulation. The inhibition of lipid accumulation of soy alcalase hydrolysates in 3T3-L1 adipocytes ranged from 29 to 46%. Soy hydrolysates made from genotypes with 45.3 +/- 3.3% of total protein as beta-conglycinin, on average, showed significantly higher inhibition of lipid accumulation compared to those with 24.7 +/- 1.5% of extracted total protein as beta-conglycinin. Moreover, after in vitro simulated digestion with pepsin-pancreatin of the soy alcalase hydrolysates, 86% of the original activity remained. Adiponectin expression was induced in 3T3-L1 adipocytes treated with 15 soy hydrolysates up to 2.49- and 2.63-fold for high and low molecular weight adiponectin, respectively. The inhibition of lipid accumulation calculated from a partial least squares (PLS) analysis model correlated well with experimental data (R(2) = 0.91). In conclusion, it was feasible to differentiate soy varieties on the basis of the potential of their proteins to reduce fat accumulation using a statistical model and a cell-based assay in vitro. Furthermore, beta-conglycinin embeds more peptides than glycinin subunits that inhibit lipid accumulation and induce adiponectin in 3T3-L1 adipocytes. Therefore, soy ingredients containing beta-conglycinin may be important food components for the control of lipid accumulation in adipose tissue.     

红娘鱼降血压肽的酶解制备工艺优化及酶解产物的抗氧化活性研究

为有效利用红娘鱼制备降血压肽,以红娘鱼鱼糜为原料提取蛋白,并对其进行酶解制备降血压肽。以血管紧张素转换酶ACE抑制率和水解度为指标,通过响应面分析法对酶解红娘鱼鱼糜蛋白制备降血压肽的工艺条件进行优化,并对最优条件下制备的酶解产物进行分子量和抗氧化活性测定。结果表明,碱性蛋白酶是制备降血压肽的最适蛋白酶,响应面法优化制备降血压肽的最佳酶解条件为pH值9、酶与底物的比值(酶底比)1.4%、温度54℃、时间2 h,此条件下酶解制得的降血压多肽ACE抑制率理论值为88%,实际值为89.3%;经高效液相色谱(HPLC)分析可得酶解产物相对分子量<2 000 Da。通过测定酶解产物样品的1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除率、羟自由基(·OH)清除率及还原力判定其体外抗氧化活性,结果表明酶解产物具有较强抗氧化活性。本研究结果为红娘鱼的高值化利用提供了数据支持和理论基础。     

Lower weight gain and hepatic lipid content in hamsters fed high fat diets supplemented with white rice protein, brown rice protein, soy protein, and their hydrolysates

The physiological effects of the hydrolysates of white rice protein (WRP), brown rice protein (BRP), and soy protein (SP) hydrolyzed by the food grade enzyme, alcalase2.4 L, were compared to the original protein source. Male Syrian Golden hamsters were fed high-fat diets containing either 20% casein (control) or 20% extracted proteins or their hydrolysates as the protein source for 3 weeks. The brown rice protein hydrolysate (BRPH) diet group reduced weight gain 76% compared with the control. Animals fed the BRPH supplemented diet also had lower final body weight, liver weight, very low density lipoprotein cholesterol (VLDL-C), and liver cholesterol, and higher fecal fat and bile acid excretion than the control. Expression levels of hepatic genes for lipid oxidation, PPARα, ACOX1, and CPT1, were highest for hamsters fed the BRPH supplemented diet. Expression of CYP7A1, the gene regulating bile acid synthesis, was higher in all test groups. Expression of CYP51, a gene coding for an enzyme involved in cholesterol synthesis, was highest in the BRPH diet group. The results suggest that BRPH includes unique peptides that reduce weight gain and hepatic cholesterol synthesis.     

Glycemic Response to Oat Bran Muffins Treated to Vary Molecular Weight of β‐Glucan

Oat bran muffins, containing 4 or 8 g of β‐glucan per two‐muffin serving, were prepared with or without β‐glucanase treatment to produce a range of β‐glucan molecular weights from 130,000 to just over 2 million. Following an overnight fast, the glycemic responses elicited by the untreated and treated muffins was measured in 10 healthy subjects and compared with a control whole wheat muffin. Taken all together, the 4‐g β‐glucan/serving muffins reduced blood glucose peak rise (PBGR) by 15 ± 6% compared with the control. The 8‐g β‐glucan/serving muffins had a significantly greater effect (44 ± 5% reduction compared with the control, P < 0.05). The efficacy of the muffins decreased as the molecular weight was reduced from a 45 ± 6% reduction in PBGR (P < 0.05) for the untreated muffins (averaged of both serving sizes) to 15 ± 6% (P < 0.05) for muffins with the lowest molecular weight. As the molecular weight was reduced from 2,200,000 to 400,000, the solubility of the β‐glucan increased from a mean of 44 to 57%, but as the molecular weight was further decreased to 120,000, solubility fell to 26%. There was a significant correlation (r² = 0.729, P < 0.001) between the peak blood glucose and the product of the extractable β‐glucan content and the molecular weight of the β‐glucan extracted.     

Antihypertensive Effect of Protein Hydrolysate from Azufrado Beans in Spontaneously Hypertensive Rats

The objective of this study was to evaluate the antihypertensive potential of common bean protein hydrolysate. Protein concentrates were obtained, followed by Alcalase enzymatic hydrolysis, and then ultrafiltrated (3,000 molecular weight cutoff); the lyophilized product was named BP3. The angiotensin converting enzyme (ACE) inhibitory activity was determined as IC₅₀ (3.68 ± 0.07 μg/mL). The antihypertensive effect was evaluated in spontaneously hypertensive rats (SHR) by two assays; Captopril ACE inhibitor was used as a reference compound and water as a control. A short‐term assay showed a maximum decrease in mean arterial pressure of –41 ± 5 mmHg in SHR, 3 h after oral administration of 500 mg of BP3/kg of body weight (bw). In a long‐term assay, a significant decrease in systolic blood pressure of –24 ± 5 mmHg was observed in SHR, after 45 days of oral administration of 500 mg of BP3/kg of bw/12 h. In both assays, BP3 treatment showed antihypertensive effect over SHR, similar to Captopril treatment. The sequences of the most abundant peptides present in BP3, determined by mass spectrometry, were identified as KFPWVK, GADFRKK, and PQSPCKRVNRHS. These peptides are reported for the first time in Azufrado Higuera common beans, and they are most likely responsible for the antihypertensive effect of BP3.     

Water Solubility and Macromolecular Properties of Corn Meal Extrudates as Affected by Epichlorohydrin

Degermed corn meal adjusted to 18% moisture content (db) with epichlorohydrin (ECH) content at 0, 0.5, 1, or 2% (w/w) were extruded with a twin-screw laboratory extruder at a screw speed of 140 rpm. Compression and metering barrel zones were set at 100, 120, or 140°C. Water solubility (WS) of ground extrudates ranged from 7.6 ± 1.1% to 14.3 ± 1.3%. ECH content had a significant (P < 0.01) negative effect on WS, while barrel temperature and the interaction between barrel temperature and ECH content were not significant (P > 0.05). Presumably, ECH reduced WS of extrudates through cross-linking between hydroxyl groups on starch and protein molecules. Gel-permeation chromatography patterns for both 100 and 140°C barrel temperatures showed that high molecular weight carbohydrates in the extrudates decreased with increasing ECH content without a simultaneous increase in low molecular weight carbohydrates. This suggested that the decrease in high molecular weight fractions was due to insolubilization by cross-linking rather than degradation. SDS-PAGE revealed that two protein bands of ≈29 and 17.5 kDa disappeared, and a new band appeared at 45 kDa with increasing ECH content. This indicated that, most likely, ECH reacted with protein in addition to reacting with starch. However, glycoprotein and starch-protein complexes were not identified with electrophoresis.     

瞬时弹射式蒸汽爆破法制备速溶牦牛骨粉及其理化特性

为解决骨粉的难溶解性及制备耗时问题,该研究采用瞬时弹射式蒸汽爆破(instant catapult steam explosion,ICSE)技术制备速溶牦牛骨粉,并与常规球磨牦牛骨粉进行理化特性比较分析。通过观察不同压力(0.5~1.5 MPa)和不同保压时间(5~30 min)ICSE条件下牦牛骨的液化情况及骨粉得率,以确定牦牛骨粉的制备条件,并通过骨粉化学结构、粒度分布、微观形态、稳定性、蛋白质溶解性和钙离子释放度的测定对比分析了速溶牦牛骨粉和常规球磨骨粉的理化特性。结果显示:1.5 MPa 30 min ICSE条件下制备的骨粉(<500目)得率可达46.16%;与常规球磨牦牛骨粉相比,ICSE牦牛骨粉化学结构无明显变化,但其中值粒径(5.61μm)明显较小(P<0.05),粒度分布均匀并呈正态分布,微观形态均匀规则;ICSE牦牛骨粉的蛋白质溶解度在37、60和100℃条件下分别为97.17%、95.29%和82.07%,均明显高于球磨骨粉(4.07%,6.47%和10.17%)(P<0.05);ICSE牦牛骨粉钙离子释放度为67.42 mg/g,高于常规球磨骨粉(14.25 mg/g);此外,短时间内ICSE骨粉悬浮液在室温条件下无明显沉淀,其溶解性和稳定性优于球磨骨粉。ICSE法制备速溶牦牛骨粉解决了骨粉制备耗时长、溶解性差等问题,为骨粉的制备提供了一种新方法。     

Inhibition of lipid oxidation in cooked beef patties by hydrolyzed potato protein is related to its reducing and radical scavenging ability

Protein hydrolysates were prepared by limited alcalase hydrolysis (0.5, 1, and 6 h, corresponding to degrees of hydrolysis of 0.72, 1.9, and 2.3, respectively) of heat-coagulated potato protein. The hydrolysates were characterized for peptide composition, ferric reducing/antioxidant power (FRAP), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity, and Fe2+- and Cu2+-chelation capacity. Hydrolyzed and intact proteins were formulated (4%, w/w) into beef patties to determine in situ antioxidant efficacy. Thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) formed in cooked and PVC-packaged patties during storage (4 degrees C, 0-7 days) were analyzed. Hydrolysis increased the protein solubility by 14-19-fold and produced numerous short peptides (< 6 kDa). The FRAP values of the protein sample (23 micromol/g) increased markedly after hydrolysis but were similar between the three hydrolysates (597-643 micromol/g). Similarly, the ABTS radical-scavenging activity also was increased by hydrolysis and was the greatest for the 1-h hydrolysate. Hydrolysis increased the Cu2+-chelation activity but decreased the Fe2+-chelation ability of the protein. The production of PV in patties after 7 days of storage was lowered 44.9% and 74.5% (P < 0.05), and that of TBARS was reduced 40.9% and 50.3% (P < 0.05), by intact and hydrolyzed proteins, respectively.