温度和pH值对耐高温α-淀粉酶活力的影响

本文系统的研究了温度、pH值和底物浓度对地衣芽孢杆菌HM-3产生的耐高温α-淀粉酶酶活力的影响。研究结果表明：地衣芽孢杆菌HM-3N耐高温α-淀粉酶的最适酶促反应温度为：75％-85℃之间，最适作用的pH值为：6．1-7．0之间，该酶用于玉米淀粉的液化其最适底物浓度是20％～25％。     

耐高温α-淀粉酶的研究进展

耐高温α-淀粉酶是一种重要的工业用酶制剂。本文概述了耐高温α-淀粉酶的酶学性质、产生茵及其高产菌株的选育,介绍了发酵生产以及分离纯化方法方面的研究进展。     

耐高温α-淀粉酶的酶学性质研究

耐高温α-淀粉酶是淀粉生产麦芽糖的关键酶。本文对两种耐高温α-淀粉酶的酶学性质进行了对比研究。结果表明：两种酶的耐高温能力差别较大,酶活差别明显;最适pH值均为7．0,耐酸性较差：当Ca^2＋浓度在7～9mmol／L时,酶活提高明显。     

耐高温α-淀粉酶基因改造研究进展

耐高温α-淀粉酶是重要的工业用酶制剂之一,主要介绍耐高温α-淀粉酶的基因改造研究进展.     

耐高温α-淀粉酶特性的研究

耐高温α-淀粉酶是在高温下具有最适反应温度的α-淀粉酶。本文对地衣芽孢杆菌所产耐高温α-淀粉酶的最适反应温度、热稳定性、最通反应 pH 以及 pH 稳定性等进行了系统的研究,为该酶的广泛应用提供了理论基础。     

耐高温α-淀粉酶发酵培养基和工艺的优化

通过一系列摇瓶实验,对耐高温α-淀粉酶发酵培养基和发酵工艺进行了优化,在50L全自动发酵罐中进行验证,发酵活力达到14900u/mL,比优化前增加了14%。优化后的培养基和工艺为:白糊精12%,(NH4)2SO40.5%,豆粕粉2%,磷酸盐0.8%;DE20～30,初始pH6.0～6.5。     

耐高温α-淀粉酶的研究进展

耐高温α-淀粉酶是重要的工业用酶制剂之一,本文介绍了耐高温α-淀粉酶的分子结构特点和催化机理及其研究进展。     

耐高温α-淀粉酶在酒精生产中的应用

耐高温α－淀粉酶在酒精生产中的应用中,中温蒸煮较高温蒸煮用汽量减少30％左右,糖化酶减少20－30u/g,发醇质量在酒度,酸度,挥发酸,还原糖,总糖等方面的均好于高温蒸煮,甲醇含量低,原料出酒率,淀粉出酒率提高,吨酒精成本降低58．2元。（孙悟）     

添加耐高温α-淀粉酶对马铃薯糊化的影响

马铃薯粉的糊化起始温度为65.5℃;马铃薯粉糊化醪最高粘度高达21Pa·s,糊化过程中须添加耐高温α-淀粉酶;耐高温α-淀粉酶对马铃薯粉的最佳作用条件为60U/g的加酶量,处理温度85℃,处理时间30min。      

添加耐高温α-淀粉酶对马铃薯糊化的影响

马铃薯粉的糊化起始温度为65.5℃;马铃薯粉糊化醪最高粘度高达21Pa·s,糊化过程中须添加耐高温α-淀粉酶;耐高温α-淀粉酶对马铃薯粉的最佳作用条件为60U/g的加酶量,处理温度85℃,处理时间30min。     

酶法水解香/芭蕉根部球茎粉浆研究及动力学分析

考察香/ 芭蕉根部球茎粉浆酶法水解液化过程,采用液态高温α- 淀粉酶,在高温条件下作用于香/ 芭蕉根部球茎粉浆,通过单因素和正交试验,分别检测水解液中还原糖含量,以考察其作用情况。结果表明：液化温度85℃、粉浆pH6.4、香/ 芭蕉根部球茎粉浆质量浓度30mg/mL、加酶量0.064mL/g,酶法水解液化效果最佳,Vm 为0.708mg/(mL·min),Km 为27.410mg/mL,水解液的DE 值达到37.61%。     

荠菜过氧化物酶热失活动力学的研究

目的 研究热烫处理引起荠菜过氧化酶(POD)失活的速率常数和动力学规律。方法 对荠菜在80～100℃的热水处理一定时间条件,对荠菜过氧化酶的残余活性进行测定,并用一级动力学模型对过氧化物酶失活动力学进行拟合,分析失活速率常数。结果 热烫处理钝化新鲜荠菜POD活性效果明显,在80～100℃处理范围内,随着处理温度的上升,荠菜POD 失活速率常数k 值从0.01702增加到0.14260,反应活化能为114 kJ/mol。一级动力学模型拟合决定系数R²＞0.99。结论 荠菜POD 的热失活动力学符合一级动力学模型。     

不同介质中甲型副伤寒沙门氏菌的热失活特性

研究甲型副伤寒沙门氏菌在不同介质中热失活规律,对接种10~8 CFU/g甲型副伤寒沙门氏菌的不同介质进行55、63、72℃热处理,测定处理后样品中甲型副伤寒沙门氏菌的菌体浓度。应用Dose Resp模型拟合在3种温度下志贺氏菌的动力学模型,用D值(decimal reduction time)表示甲型副伤寒沙门氏菌在不同介质中的耐热情况。结果表明:甲型副伤寒沙门氏菌的热失活曲线运用Dose Resp模型拟合较好,相关系数均在0.97以上。甲型副伤寒沙门氏菌在不同介质中的D值不同,在蛋白质和脂肪含量较高的灌肠肥瘦肉1∶1(m/m)中D值较大,相对耐热。55℃条件下热处理25.0 min,63℃热处理2.03 min,72℃热处理0.31 min后,一般肉制品中甲型副伤寒沙门氏菌均能被杀死。     

Analysis of the kinetic patterns of horseradish peroxidase thermal inactivation in sodium phosphate buffer solutions of different ionic strength

The thermal inactivation of horseradish peroxidase was studied in sodium phosphate buffer solutions and in pure water at pH 7 in the temperature range of 70–95°C. The sodium phosphate ions concentration affected both the thermostability and the kinetic patterns and had a stabilizing effect. The gradual change observed at low concentrations made a series-type mechanism theoretically more coherent with the experimental observations than the conventionally applied two-fraction model. In water the kinetics is apparently First order at high temperatures, while the results obtained at 25°C support the occurrence of a series-type inactivation mechanism. The pH and enzyme concentration also affect the inactivation proFile, supporting the conclusion that the thermal inactivation is not a monomolecular process with respect to protein concentration.     

Enzyme Inactivation in Food Processing using High Pressure Carbon Dioxide Technology

High pressure carbon dioxide (HPCD) is an effective non-thermal processing technique for inactivating deleterious enzymes in liquid and solid food systems. This processing method avoids high temperatures and exerts a minimal impact on the nutritional and sensory properties of foods, but extends shelf life by inhibiting or killing microorganisms and enzymes. Indigenous enzymes in food such as polyphenol oxidase (PPO), pectin methylesterase (PME), and lypoxygenase (LOX) may cause undesirable chemical changes in food attributes, showing the loss in color, texture, and flavor. For more than two decades, HPCD has proved its effectiveness in inactivating these enzymes. The HPCD-induced inactivation of some microbial enzymes responsible for microbial metabolism is also included. This review presents a survey of the published knowledge regarding the use of HPCD for the inactivation of these enzymes, and analyzes the factors controlling the efficiency of HPCD and speculates on the underlying mechanism that leads to enzyme inactivation.     

Thermal inactivation of polyphenoloxidase and peroxidase in green coconut (Cocos nucifera) water

Coconut water is an isotonic beverage naturally obtained from the green coconut. After extracted and exposed to air, it is rapidly degraded by enzymes peroxidase (POD) and polyphenoloxidase (PPO). To study the effect of thermal processing on coconut water enzymatic activity, batch process was conducted at three different temperatures, and at eight holding times. The residual activity values suggest the presence of two isoenzymes with different thermal resistances, at least, and a two‐component first‐order model was considered to model the enzymatic inactivation parameters. The decimal reduction time at 86.9 ^°C (D_{86.9 °C}) determined were 6.0 s and 11.3 min for PPO heat labile and heat resistant fractions, respectively, with average z‐value = 5.6 °C (temperature difference required for tenfold change in D). For POD, D_{86.9 °C} = 8.6 s (z = 3.4 °C) for the heat labile fraction was obtained and D_{86.9 °C} = 26.3 min (z = 6.7 °C) for the heat resistant one.     

Bacterial spore inactivation induced by cold plasma

ABSTRACT

Cold plasma has emerged as a non-thermal technology for microbial inactivation in the food industry over the last decade. Spore-forming microorganisms pose challenges for microbiological safety and for the prevention of food spoilage. Inactivation of spores induced by cold plasma has been reported by several studies. However, the exact mechanism of spore deactivation by cold plasma is poorly understood; therefore, it is difficult to control this process and to optimize cold plasma processing for efficient spore inactivation. In this review, we summarize the factors that affect the resistance of spores to cold plasma, including processing parameters, environmental elements, and spore properties. We then describe possible inactivation targets in spore cells (e.g., outer structure, DNA, and metabolic proteins) that associated with inactivation by cold plasma according to previous studies. Kinetic models of the sporicidal activity of cold plasma have also been described here. A better understanding of the interaction between spores and cold plasma is essential for the development and optimization of cold plasma technology in food the industry.