高频电场进行腐乳催熟的研究

该文研究了将进入发酵后期的瓶装腐乳进行高频电场处理，发现高频电场能催熟腐乳，可以缩短２５％左右的后发酵期。     

高压电场对毛霉蛋白酶活力的影响及应用于腐乳催熟

探讨了高压电场对毛霉蛋白酶酶活的影响,结果表明一定条件下,高压电场有激活毛霉蛋白酶的作用.将高压电场应用于进入发酵后期的瓶装腐乳,发现电场强度300～500 V/cm下作用6 min,可以缩短15%的后发酵期.     

毛霉高产中性蛋白酶发酵培养基的优化

以雅致放射毛霉和五通桥毛霉为实验材料,采用单因素和正交优化实验对两种毛霉高产中性蛋白酶发酵培养基进行优化。结果表明:雅致放射毛霉产中性蛋白酶发酵培养基最佳成分为:蔗糖添加量为10%、黄豆粉添加量为2.5%、KH2PO4添加量为0.4%、CaCl2添加量为0.11%,此条件下中性蛋白酶酶活力达1310.56U/mL;五通桥毛霉产中性蛋白酶发酵培养基最佳成分为:蔗糖添加量为10%、黄豆粉添加量为3.0%、KH2PO4添加量为0.37%、CaCl2添加量为0.07%,此条件下中性蛋白酶酶活力达1306.38U/mL。两种毛霉酶活力提高的百分比分别为60.1%和46.7%,此研究成果为缩短腐乳后酵周期及直装腐乳发酵工艺的后续研究奠定了基础。     

毛霉高产中性蛋白酶发酵培养基的优化

以雅致放射毛霉和五通桥毛霉为实验材料,采用单因素和正交优化实验对两种毛霉高产中性蛋白酶发酵培养基进行优化。结果表明:雅致放射毛霉产中性蛋白酶发酵培养基最佳成分为:蔗糖添加量为10%、黄豆粉添加量为2.5%、KH2PO4添加量为0.4%、CaCl2添加量为0.11%,此条件下中性蛋白酶酶活力达1310.56U/mL;五通桥毛霉产中性蛋白酶发酵培养基最佳成分为:蔗糖添加量为10%、黄豆粉添加量为3.0%、KH2PO4添加量为0.37%、CaCl2添加量为0.07%,此条件下中性蛋白酶酶活力达1306.38U/mL。两种毛霉酶活力提高的百分比分别为60.1%和46.7%,此研究成果为缩短腐乳后酵周期及直装腐乳发酵工艺的后续研究奠定了基础。      

雅致放射毛霉蛋白酶

借助超声波、电泳和高压液相色谱技术对雅致放射毛霉胞外和胞内蛋白酶进行了研究．结果表明：腐乳前期培菌时，雅致放射毛霉同时分泌胞外及胞内蛋白酶，两者酶活力变化趋势基本相同，在培菌45h时，达到最大酶活力；胞外和胞内蛋白酶均为蛋白酶系，相对分子质量组成相同；以大豆蛋白为底物时，主要水解产物相同．     

腐乳毛霉AS3.2778产蛋白酶特性研究

研究了影响腐乳毛霉AS3.2778产蛋白酶的一些因素,包括培养基的组成、发酵温度、pH以及发酵时间等。结果表明,毛霉蛋白酶是一种诱导酶,较合适的发酵条件为温度28℃,pH5～6,发酵时间48h。      

毛霉蛋白酶的特性研究

从毛豆腐中分离出1株毛霉,研究了毛霉分泌产生的蛋白酶的基本性质.结果表明:蛋白酶在pH为4、55℃时,相对酶活力最高;在4℃、pH为5～6时,蛋白酶有着较好的稳定性.一些常见的金属离子对毛霉蛋白酶活性有一定的影响,在5.0mmoL/L的浓度下,Mn2 、Ca2 、Mg2 对蛋白酶有较强的活化作用,而Zn2 、Fe2 、Fe3 对蛋白酶有一定的抑制作用,低浓度的NaCl有激活作用,但在高浓度下产生抑制作用.     

毛霉蛋白酶提取方法的研究

研究了不同浓度的ＮａＣｌ溶液、不同温度条件及不同取方法对腐乳生产菌和睦我霉的蛋白酶的提取效果。４０℃、０．３ｍｏｌ／Ｌ的ＮａＣｌ溶液分次提取可得最大酶活力。     

毛霉蛋白酶的制备及其酶解产物的分析

应用ＨＰＬＣ法分析了毛霉蛋白酶的酶解产物，并应用质谱仪测定了酶解产物的分子量，结果表明：该蛋白酶在４０℃ＰＨ７．３的条件下催化大豆分离蛋白水解５ｈ。     

毛霉蛋白酶的特性研究

从毛豆腐中分离出1株毛霉,研究了毛霉分泌产生的蛋白酶的基本性质。结果表明:蛋白酶在pH为4、55℃时,相对酶活力最高;在4℃、pH为5⁶时,蛋白酶有着较好的稳定性。一些常见的金属离子对毛霉蛋白酶活性有一定的影响,在5.0mmol/L的浓度下,Mn2+、Ca2+、Mg2+对蛋白酶有较强的活化作用,而Zn2+、Fe2+、Fe3+对蛋白酶有一定的抑制作用,低浓度的NaC l有激活作用,但在高浓度下产生抑制作用。      

高压电场对SOD活性的影响及其紫外光谱研究

利用不同电场强度处理超氧化物歧化酶(Superoxide dismutase,SOD),测试高压电场处理前后酶的活性和紫外光谱。结果表明:高压电场可使酶活性降低,其紫外光谱测试表明,不同电场强度可以改变酶的构象。酶活性的降低可能是由酶构象的改变引起。研究结果对解释静电宏观生物效应具有重要意义。     

高压静电场处理对几种呼吸跃变型果实呼吸强度的影响

以苹果等几种呼吸跃变型果实为试材,研究了100kV/m的高压静电场每天处理2h对其呼吸强度变化规律的影响并与相同条件下的对照果进行了比较,发现高压静电场处理能够有效地降低这几种果实呼吸强度的最大值,并不影响它们呼吸高峰出现的时间。     

电场对脂肪酶紫外光谱及其活性的影响

用不同电场强度处理脂肪酶,测试电场处理前后的紫外光谱和酶的活性.结果表明:脂肪酶紫外光谱发生了明显的变化,说明电场可以改变酶的构象;一定电场强度可使酶活性增加,活性的增加可能是由酶构象的改变引起的.研究结果对解释静电宏观生物效应具有重要意义.     

Reduction of protease activity in milk by continuous flow high-intensity pulsed electric field treatments

High-intensity pulsed electric field (HIPEF) is a non-thermal food processing technology that is currently being investigated to inactivate microorganisms and certain enzymes, involving a limited increase of food temperature. Promising results have been obtained on the inactivation of microbial enzymes in milk when suspended in simulated milk ultrafiltrate. The aim of this study was to evaluate the effectiveness of continuous HIPEF equipment on inactivating a protease from Bacillus subtilis inoculated in milk. Samples were subjected to HIPEF treatments of up to 866 micros of squared wave pulses at field strengths from 19.7 to 35.5 kV/cm, using a treatment chamber that consisted of eight colinear chambers connected in series. Moreover, the effects of different parameters such as pulse width (4 and 7 micros), pulse repetition rates (67, 89, and 111 Hz), and milk composition (skim and whole milk) were tested. Protease activity decreased with increased treatment time or field strength and pulse repetition rate. Regarding pulse width, no differences were observed between 4 and 7 micros pulses when total treatment time was considered. On the other hand, it was observed that milk composition affected the results since higher inactivation levels were reached in skim than in whole milk. The maximum inactivation (81%) was attained in skim milk after an 866-micros treatment at 35.5 kV/cm and 111 Hz.     

Effect of pulsed electric field on calpain activity and proteolysis of venison

The present study evaluated the effect of pulsed electric field (PEF) on the calpain activity, proteolytic pattern and myofibrillar protein profile of cold-boned Longissimus dorsi obtained from red deer (Cervus elaphus). PEF treated samples, T₁ (2.5 kV, 50 Hz) and T₂ (10 kV, 90 Hz) and a non-treated control were aged for 21 days at 4 ± 1 °C. The samples were analysed for shear force (N), myofibrillar fragmentation index (MFI), calpain activity, proteolysis of desmin and troponin-T and myofibrillar protein profile (SDS-PAGE). No significant impact of PEF was observed on the shear force and MFI. A slight increase was recorded in the calpain activity and proteolysis of troponin-T, suggesting a tendency of PEF to improve the tenderization process. Collectively, the results from casein zymography, Western blotting and myofibrillar protein profile suggest that PEF did not produce any significant impact on the tenderization process of venison.     

Effect of stress-induced high post-mortem pH on protease activity and tenderness of beef

Forty-four Swiss Brown young bulls were stressed by regrouping unfamiliar animals before slaughter. M. longissimus thoracis (6-9th ribs) of carcasses were analysed for post-mortem pH, protease activities (m- and α-calpain, calpastatin and cathepsin B + L), Warner-Bratzler shear force and sensory tenderness and juiciness. Muscles were classified into three groups, according to ultimate pH values: > 6.3, 6.3-5.8 and < 5.8. The most significant difference related to high pH was a higher activity of m-calpain at 7th day post mortem. It was also found that meat showing the highest pH was significantly more tender and juicy. Sensory tenderness was highly correlated with activity of m-calpain at 7th day post mortem (r = 0.776) and with ultimate pH (r = 0.708). It is concluded that high ultimate pH induced by stress significantly increases m-calpain activity, and this results in a greatly enhanced tenderisation of beef meat.     

Effects of high electric field pulses on enzymes

The application of high electric field pulses (HELP) in food processing offers potential both as a preservation technology, and as an adjunct to other processes, such as drying, extraction. In respect of the use of pulsed electric fields as preservation technology, the impact of this technology on food quality degrading enzymes is of particular interest. This paper presents a detailed literature review on the effects of pulsed electric fields on enzymes, complemented with recent results on the impact of this HELP-technology on enzymes, obtained within EU project ‘High electric field pulses: food safety, quality and critical process parameters’ (contract FAIR-CT97-3044).     

固体发酵制备毛霉蛋白酶的研究

该文研究了毛霉M2产蛋白酶的若干影响因素，包括培养基的成分以及发酵条件等。结果表明：在麸皮与水的合适比例为1：0.8；在基本培养基上添加一定浓度的碳源、氮源及无机盐有利于蛋白酶的合成；菌体较为合适的产酶条件为温度28℃，pH6．0，发酵时间36h。