Angiotensin I-converting enzyme (ACE) inhibitory activities of sardinelle (Sardinella aurita) by-products protein hydrolysates obtained by treatment with microbial and visceral fish serine proteases

The angiotensin I-converting enzyme (ACE) inhibitory activities of protein hydrolysates prepared from heads and viscera of sardinelle (Sardinella aurita) by treatment with various proteases were investigated. Protein hydrolysates were obtained by treatment with Alcalase^®, chymotrypsin, crude enzyme preparations from Bacillus licheniformis NH1 and Aspergillus clavatus ES1, and crude enzyme extract from sardine (Sardina pilchardus) viscera. All hydrolysates exhibited inhibitory activity towards ACE. The alkaline protease extract from the viscera of sardine produced hydrolysate with the highest ACE inhibitory activity (63.2 ± 1.5% at 2 mg/ml). Further, the degrees of hydrolysis and the inhibitory activities of ACE increased with increasing proteolysis time. The protein hydrolysate generated with alkaline proteases from the viscera of sardine was then fractionated by size exclusion chromatography on a Sephadex G-25 into eight major fractions (P₁–P₈). Biological functions of all fractions were assayed, and P₄ was found to display a high ACE inhibitory activity. The IC₅₀ values for ACE inhibitory activities of sardinelle by-products protein hydrolysates and fraction P₄ were 1.2 ± 0.09 and 0.81 ± 0.013 mg/ml, respectively. Further, P₄ showed resistance to in vitro digestion by gastrointestinal proteases. The amino acid analysis by GC/MS showed that P₄ was rich in phenylalanine, arginine, glycine, leucine, methionine, histidine and tyrosine. The added-value of sardinelle by-products may be improved by enzymatic treatment with visceral serine proteases from sardine.     

混浊梨汁加工中PPO热失活条件的研究

研究了热处理梨汁（加或不加防褐变剂）,梨浆使其中的PPO完全及部分失活所需要的温度和时间结果为：在90℃处理果汁10s可使其中的PPO完全失活,而对于果浆则需要90℃处理15s以上.加了防褐变剂的果汁经90℃处理10s可使其中的PPO完全失活.此外,经80℃处理30s以上虽不能使其中的PPO完全失活,但添加的防褐变剂及果汁自身的pH可抑制残余的PPO,从而防止酶促褐变的发生.70℃处理梨汁40s不能防止其中的酶促褐变.     

酶水解-阴离子色谱法联用测定婴幼儿配方奶粉中果聚糖的总含量及平均聚合度

摘 要：目的 建立酶水解—离子色谱法测定婴幼儿配方奶粉中总果聚糖的分析方法。方法 通过酶水解将样品中的果聚糖水解成果糖、葡萄糖,以PA1阴离子交换柱分离,脉冲积分安培检测器进行检测果聚糖总含量,以果糖与葡萄糖产生的比例计算平均聚合度。结果 果糖、葡萄糖在0.25~25.0 mg/L范围内线性关系良好（R2>0.999）,果聚糖的回收率为96.9%~104.4%,方法检出限为195mg/kg,定量限为650mg/kg。实际样品测定中,日间的相对标准偏差（RSD,n=6）为1.15%~3.87%。结论 可用于婴幼儿配方奶粉中果聚糖的总含量及平均聚合度的测定方法。     

木霉LE02 β-1，3-葡聚糖酶酶学特性的研究

对木霉菌株LE02所产β-1,3-葡聚糖酶的酶学特性进行了研究。结果表明,该酶最适反应温度为55℃、最适反应pH值为5.0。Co~(2+)、K+、Zn~(2+)、Li~+、Ba~(2+)、Cu~(2+)以及1.0mmol/L的Fe~(2+)对该酶没有影响,Cd~(2+)和10.0mmol/L的Mg~(2+)对酶具有部分抑制作用,而低浓度的Hg~(2+)、5.0mmol/L以上的Mn~(2+)和10.0 mmol/L的Fe~(3+)能强烈抑制该酶的活性。该酶只能作用于β-1,3-糖苷键,以Larinami为底物时其米氏常数K_m值为128.34μg/mL,最大反应速度V_m为23.01μg/(min·mL)。经过SDS-PAGE测定的分子质量近似为80.137ku。     

壳聚糖涂膜对鲜切马铃薯褐变程度的影响

研究了不同壳聚糖涂膜液对鲜切马铃薯色泽、褐变强度和多酚氧化酶活力的影响。结果表明:对于鲜切马铃薯的褐变程度,以复合涂膜液Ⅰ(1%壳聚糖+0.5%抗坏血酸)或以复合涂膜液Ⅱ(1%壳聚糖+0.5%抗坏血酸+0.15%氯化钙+0.8%乙二胺四乙酸二钠)抑制效果显著,且以后者更佳。     

Enzymatic treatment of peanut kernels to reduce allergen levels

This study investigated the use of enzymatic treatment to reduce peanut allergens in peanut kernels as affected by processing conditions. Two major peanut allergens, Ara h 1 and Ara h 2, were used as indicators of process effectiveness. Enzymatic treatment effectively reduced Ara h 1 and Ara h 2 in roasted peanut kernels by up to 100% under optimal conditions. For instance, treatment of roasted peanut kernels with α-chymotrypsin and trypsin for 1–3 h significantly increased the solubility of peanut protein while reducing Ara h 1 and Ara h 2 in peanut kernel extracts by 100% and 98%, respectively, based on ELISA readings. Ara h 1 and Ara h 2 levels in peanut protein extracts were inversely correlated with protein solubility in roasted peanut. Blanching of kernels enhanced the effectiveness of enzyme treatment in roasted peanuts but not in raw peanuts. The optimal concentration of enzyme was determined by response surface to be in the range of 0.1–0.2%. No consistent results were obtained for raw peanut kernels since Ara h 1 and Ara h 2 increased in peanut protein extracts under some treatment conditions and decreased in others.     

响应面法优化复合护色剂对柿汁褐变的影响

以柿果为原料,利用曲酸、L-半胱氨酸、抗坏血酸、柠檬酸为护色剂对柿汁加工过程中抑制褐变进行研究。以褐变抑制率和色差值为指标,在添加不同浓度护色剂单因素试验基础上,进行正交试验,选取对褐变抑制率及色差值影响较大的三种护色剂为自变量,褐变抑制率为响应值,采用Box-Behnken中心组合试验和响应面分析法,研究自变量交互作用对柿汁褐变的影响。结果表明:柿汁复合护色剂最优配比为曲酸1.02g/100mL、抗坏血酸0.41g/100mL、柠檬酸0.83 g/100mL,此条件下柿汁褐变抑制率实测值为86.15%,与预测值吻合率可达97.79%,可有效抑制柿汁褐变发生。     

Some characteristics and a comparison 6f the activities of o-dihydroxyphenoloxidase activity from five yam (Dioscorea spp.) species

o-Dihydroxyphenoloxidase (E.C. 1.14.18.1) (o-DPOase) was extracted from acetone-extracted freeze-dried yam tubers, and fractionated by (NH₄)₂SO₄ precipitation and chromatography on DEAE-cellulose to give two forms from Dioscorea alta L. (cv. UM680) and three forms from D. rotundata Poir. (cv. Nwopoke). Polyacrylamide gel electrophoresis revealed one of the forms from each species to contain two protein bands with o-DPOase activity. o-DPOase from D. alata showed activity with catechol, (+)-catechin, (?)-epicatechin and chlorogenic acid, but not with tyrosine, as substrate, o-DPOase from D. rotundata showed activity only with catechol and (+)-catechin. K_m values for D. rotundata enzymes, calculated assuming a two-substrate reaction, were between 0.2 and 0.8 mM for oxygen and 70 and 120 mM for catechol. The enzyme was most active between pH 5.5 and pH 7.0, and showed slight activation after holding for 2 minutes at 40 or 50°C. After heating to above 60°C the enzyme showed evidence of irreversible denaturation. Theo-DPOase activity extracted from ten cultivars of five species of D. alata L., D. bulbifera L., D. cayenensis Lam., D. dumetorum Pax, and D. rotundata Poir. were compared.     

七种日韩梨果泥贮藏稳定性研究

以丰水、华山、南水、大果水晶、圆黄、黄金、新高梨为原料,通过检测梨泥的pH值、还原糖、氨基态氮、5-羟甲基糠醛(5-HMF)、可溶性酚和总色差的含量,对7种日韩梨果泥贮藏稳定性进行研究。结果表明：在贮藏过程中,7种梨泥贮藏稳定性由高到低依次为圆黄、华山、大果水晶、丰水、南水、新高和黄金。圆黄梨泥的还原糖(9.6%～7.2%)和氨基态氮(4.2～3.5mg/100mL)含量较高,5-HMF(0.6～1.1mg/100g)和可溶性酚(3.3～2.1mg/g)含量较少,pH值(3.3～3.4)和色差值(22.7～39.9)较低,贮藏稳定性优于其他品种。     

橙汁储藏期非酶褐变控制与感官评定

橙汁作为世界上销量最大的果汁类饮品,其储藏过程中的褐变一直是研究领域的一大难题.综述了目前抑制橙汁褐变的一些方法,并介绍了橙汁储藏过程中的感官评定方法,为橙汁褐变的研究提供一定的理论基础.