Antioxidative properties of partially purified barley hordein, rice bran protein fractions and their hydrolysates

Antioxidative properties of proteins from barley and rice bran and their hydrolysates were examined. Three major hordein fractions of barley, B, C and D hordeins, were partially purified by gel filtration. Albumin, globulin, prolamin and glutelin fractions of rice bran were fractioned by the Osborne method. Hydrolysates of these protein fractions were prepared by digesting with pepsin followed by trypsin. Antioxidant properties in terms of antioxidative activity against linoleic acid peroxidation and reducing activity without the lipid adjuvant were investigated. The globulin fraction from rice bran protein revealed the strongest antioxidative activity throughout the incubation time of 7 days (p ≤ 0.05). The albumin fraction of rice bran protein showed the highest reducing activity (6964 μmol of Fe²⁺) followed by globulin, prolamin, glutelin and hordein fractions with activities of 2904, 2017, 1809 and 1333 μmol of Fe²⁺, respectively (p ≤ 0.05). Partially purified C hordein exhibited the highest reducing activity compared with B and D hordeins. Protein hydrolysates obtained after digestion with pepsin and trypsin exhibited much greater antioxidative, as well as reducing, activities than those from before digestion.     

保加利亚乳杆菌水解酪蛋白的条件及自由基清除活性的研究

利用保加利亚乳杆菌水解酪蛋白,通过测量游离氨基和酸可溶性多肽、氨基酸含量的变化,得到适宜水解酪蛋白的条件为:pH6.5~7.0、温度42℃、菌体浓度12.5OD/mL。通过制备水解程度不等的水解产物进行自由基清除活性评价,结果表明,酪蛋白经过保加利亚乳杆菌水解之后,其自由基清除活性增强。     

Rheological Behavior of Protein Hydrolysates from Papain-treated Male Gonad of Scallop (Patinopecten yessoensis)

ABSTRACT

In the present study, the rheological behavior of hydrolysates from scallop male gonad hydrolysates (SMGHs) was studied. The hydrolysates were obtained from scallop male gonads (SMGs) using papain. The changes in molecular mass of proteins in SMGHs were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that the proteins of SMGs were significantly degraded after hydrolysis with papain. The degree of hydrolysis reached to 17.8% and 20.8% for SMGHs treated by papain at 300 and 3,000 U/g protein, respectively. The SMGHs exhibited a weak strain overshoot behavior as well as non-Newtonian shear thinning flow behavior. Moreover, the rheological properties of SMGHs possessed a papain dose-dependent manner. These results suggest that SMGHs could be applied as a potential gelling and thickening agent in food formulations.     

Enzymatic Hydrolysis of Alaska Pollock Proteins Based on Kinetics Model and Lysine Biosensor–Neural Network Model

Controlled proteolysis is important for target hydrolysates. The hydrolysis kinetics of pollock bone protein (PBP) was obtained by mathematic deduction and experimental analysis. The equation of degree of hydrolysis was as follows: DH = 2.801 ln|1 + (0.06044E₀/S₀?0.1005)t|, which could predict the hydrolysis process of PBP when hydrolysis condition was strictly controlled. However, the hydrolysis reaction was affected by several factors, and the predicted value may be against the experimental result. Therefore, online monitoring was necessary for obtaining the target peptides. Biosensor and artificial neural network (ANN) were employed for monitoring hydrolysis process online. Free lysine level was chosen as the monitoring factor determined by immobilized lysine oxidase electrodes. Based on the lysine biosensor and ANN, the hydrolysis monitoring model LYS-ANN was built, including 3 input layer nodes (E₀, S₀, and LYS), 1 output layer node (DH), and 11 hidden layer nodes. R² value between sample value and simulation value was 0.9964. Simulation error was in the range of 0–4.56%, and the average relative error was 0.94%. The verification tests of PBP hydrolysis showed that the LYS-ANN model could forecast hydrolysis process successfully with high efficiency and accuracy even if the hydrolysis conditions varied.     

基于特征粘度的鳕鱼骨胶原蛋白酶解预测模型

以鳕鱼骨为原料制备胶原蛋白并对其酶解,利用人工神经网络建立鳕鱼骨胶原蛋白酶解反应的预测模型。结果显示,胶原蛋白及水解物的粘度随温度的升高而下降,随着胶原蛋白的水解程度加深,肽链长度与分子量减小,特征粘度呈现下降趋势,水解度与特征粘度呈一一映射关系。以水解产物的特征粘度、温度为输入参数,水解度作为输出参数,建立神经网络预测模型。样本值与仿真值的R2值为0.991 6,平均相对误差为2.5%,所建网络预测模型性能好、预测精度高。验证试验的相对误差为1.06%~4.32%,实现了鳕鱼骨胶原蛋白酶解反应的仿真预测与监控。     

乳清蛋白中性蛋白酶解物对Caco-2细胞铁吸收的影响

采用体外消化与Caco-2 细胞模型相结合的方法,研究了乳清蛋白浓缩物（WPC）中性酶解产物经超滤后获得的各组分对强化铁生物利用率的影响;采用Sephadex G-25 凝胶层析法对WPC的中性酶解产物的消化产物进行分离,并用Caco-2 细胞模型评价了分离后各组分对铁吸收的影响。结果表明,WPC中性酶解产物的各组分中,低分子量的组分（分子量小于10kDa）可以有效提高铁的生物利用率。组分3kR（分子量在3~10kDa之间）和3kF（分子量小于3kDa）与铁一起摄入时,铁的生物利用率分别达到23.32%、24.23%,显著高于WPC（2.58%）。铁的吸收率和生物利用率显著相关,而渗透率与生物利用率之间没有显著相关性;WPC中性酶解产物消化产物的各组分中,分子量小于1kDa 的组分将铁的吸收率提高到90.47%,显著高于空白（25.13%）。而分子量为1~5kDa 的一个组分会抑制铁的吸收。