欧姆加热的电参数对杀菌效果的影响

采用欧姆加热杀菌与水浴加热杀菌对比的方法。以豆浆的总菌数为试验菌群,通过改变电源的电压和频率,得出电源的电压和频率与杀菌效果的关系。对比水浴加热杀菌的效果可知:当电压超过60V时,欧姆加热方法的杀菌效果明显好于水浴加热方法的杀菌效果,残菌率随处理电压的增加以指数规律减少;随着频率的增加,欧姆加热的杀菌好,但当频率超过一定值时杀菌效果降低;频率在30～300Hz时其杀菌效果明显优于水浴加热方法的杀菌。     

番茄酱欧姆加热杀菌工艺参数的研究

采用欧姆加热技术对番茄酱的杀菌工艺进行初步研究。选取处理电压、加热温度和保温时间为主要工艺参数,应用三元二次回归正交旋转试验和响应面分析方法并经SPSS11.5和Matlab7.1软件的分析,建立并分析番茄酱杀菌条件的数学模型。结果表明,3个因素对番茄酱杀菌效果的影响大小次序为:处理电压X1>加热温度X2>保温时间X3;最优组合为处理电压60.6V、加热温度60.2℃、保温时间123.5s,此时酵母菌残菌率为0.02%,所得回归方程显著,拟合情况良好。     

欧姆加热对豆浆风味物质的影响

为研究欧姆加热对豆浆挥发性物质的影响,采用顶空固相微萃取结合气相色谱-质谱联用技术,对豆浆的风味物质进行分析,利用内标法对各风味物质成分定量分析。通过对比50/30?μm二乙基苯/碳分子筛/聚二甲基硅氧烷（divinylbenzene/carboxen/polydimethylsiloxane,DVB/CAR/PDMS）、100?μm PDMS、65?μm PDMS/DVB 3 种萃取头对豆浆风味物质的萃取效果,筛选出最佳的萃取头,并在最适条件下分析豆浆的风味物质成分,为排除热效应对实验结果的影响,2?种热处理历程尽可能保持一致。结果表明：65?μm PDMS/DVB纤维萃取头较100?μm PDMS和50/30?μm DVB/CAR/PDMS纤维萃取头更适宜豆浆风味物质的测定;从豆浆样品中共检测到35?种挥发性物质,其中醛类物质16?种,醇类物质5?种,酮类物质3?种,酯类物质1?种,杂环烃类物质10?种,主要包括己醛、（E）-2-庚烯醛、1-辛烯-3-醇等,这些物质共同组成豆浆的特征香气;不同加热处理对豆浆风味物质种类的影响不大,但是对特征香气含量有显著影响（P＜0.05）;欧姆加热处理组样品中己醛、1-辛烯-3-醇、（E）-2-辛烯醛的含量分别比传统加热处理组约低45.55%、58.60%、25.56%,且在欧姆加热处理样品组中未检测到（E）-2-己烯醛和正己醇,而这些物质是豆腥味的主要组成成分。因此,利用欧姆加热方式加热豆浆可以显著降低豆浆的豆腥味。本研究可以为欧姆加热技术在豆浆加工业中的应用提供理论依据。     

食品的欧姆加热技术

本文介绍欧姆加热技术的基本原理及其在食品工业中的应用。     

欧姆加热技术在肉品工业中的应用

欧姆加热作为一种新型的食品加工技术,具有加热速度快、加热均匀、消耗能量少等优点,成为近几年研究的热点。目前,欧姆加热主要运用于加工液态和颗粒流体食品,肉品的欧姆加热还处于起步阶段。本文介绍了欧姆加热的原理、肉品欧姆加热的研究热点问题及欧姆加热在食品中的其它应用。     

欧姆加热及其在食品中的应用

欧姆加热是一种新型的加热方式，具有物料升温快、加热均匀、无污染、易操作、加工食品质量好等优点，文章综述欧姆加热的原理，加热特点及其在食品中的应用。     

欧姆加热技术对肉块品质的影响

自主设计的欧姆加热装置被用来进行研究。研究了不同电场强度(3、6、9V/cm),不同保温时间(7、9、11min)欧姆加热处理对肉块品质(加热程度值,微生物杀灭效果,质构)的影响,并与改进的水浴加热方式处理的肉块进行了品质上的比较。     

荸荠汁欧姆加热特性及欧姆加热对其澄清度的影响

荸荠汁是重要的荸荠加工制品,但其澄清度不佳的问题显著影响了产品品质。本研究使用自制欧姆加热装置处理荸荠汁,以期获得荸荠汁的欧姆加热特性,并探索欧姆加热对荸荠汁澄清度的影响。结果表明:荸荠汁的电导率随着温度和电场频率的增加而增加;低频低电场强度下荸荠汁的温度随时间呈线性关系,高频高电场强度下则呈指数关系。同一电场强度下,荸荠汁的电导率随加热频率的增加而增加,其中在200和400 Hz时电导率约为50 Hz时的两倍。荸荠汁的容抗值主要是在-5~0 Ω之间波动,电场强度对其影响不显著(p>0.05)。欧姆加热后电位值下降到原值的50%左右,颗粒稳定性下降,更加易于荸荠汁的澄清。综合来看,欧姆加热对荸荠汁澄清度有一定改善作用。     

欧姆加热对大豆酱杀菌效果及其营养成分的影响

研究了欧姆加热对大豆酱杀菌效果及营养成分的影响,结果表明,随着电压、保温时间和加热温度的增大,酵母菌残菌率下降,铵盐含量和还原糖损失率增大,氨基酸态氮含量先增加后下降;经正交试验确定最佳杀菌条件为35V、65℃、150s;在此条件下,能全部杀灭大豆酱中的酵母菌,铵盐含量增加了286％,氨基酸态氮损失率为1．95％,还原糖损失率为4．006％,电能消耗功率为157J／s。     

苹果汁的欧姆加热研究

研究了苹果汁的欧姆加热规律及其对果汁品质的影响,考察了温度(T)和可溶性固形物(SS)含量对电导率!的影响,以及电场强度(E)、可溶性固形物(SS)和加热体积(液高h)对加热速率的影响,同时考察了欧姆加热对果汁糖度、pH、透光率等的影响。结果表明,苹果汁的电导率随温度的升高而增大,且呈线性关系,随着可溶性固形物含量的增加,苹果汁的电导率和加热速率都是先增大然后减小,在26°Bx左右时最大。苹果汁的加热速率随电场强度的增加而增大,而在相同电场强度下,液高对加热速率没有影响。并且,欧姆加热对果汁品质影响很小,因此极具开发前景。      

Effect of Ohmic Heating of Soymilk on Urease Inactivation and Kinetic Analysis in Holding Time

To verify the effect of the ohmic heating on the urease activity in the soymilk, the ohmic heating methods with the different electrical field conditions (the frequency and the voltage ranging from 50 to 10 kHz and from 160 to 220 V, respectively) were employed. The results showed that if the value of the urease activity measured with the quantitative spectrophotometry method was lower than 16.8 IU, the urease activity measured with the qualitative method was negative. The urease activity of the sample ohmically heated was significantly lower than that of the sample conventionally heated (P < 0.01) at the same target temperature. It was concluded that the electrical field enhanced the urease inactivation. In addition, the inactivation kinetics of the urease in the soymilk could be described with a biphasic model during holding time at a target temperature. Thus, it was concluded that the urease in the soymilk would contain 2 isoenzymes, one is the thermolabile fraction, the other the thermostable fraction, and that the thermostable isoenzyme could not be completely inactivated when the holding time increased, whether the soymilk was cooked with the conventional method or with the ohmic heating method. Therefore, the electric field had no effect on the inactivation of the thermostable isoenzyme of the urease.     

通电加热快餐粥的研制

研究了通电加热快餐粥的配方和生产工艺,对其进行了感官评分及营养素含量和耗电量测定,并与普通电炉加热快餐粥进行了比较。实验结果表明,通电加热快餐粥的感官评分和营养素含量明显高于电炉加热快餐粥,而耗电量低于电炉加热快餐粥。     

通电加热过程中食品物料电导率的研究进展

介绍了通电加热的基本原理及其特点 ,重点分析和探讨了通电加热过程中食品物料电导率的研究现状 ,展望了食品物料电导率的研究方向     

胡萝卜、油菜的通电加热烫漂研究

研究了通电加热烫漂对胡萝卜、油菜中维生素含量的影响,并与普通电炉加热进行了比较;研究了胡萝卜、油菜通电加热烫漂的最佳工艺条件。实验证明,随着烫漂时间的延长,胡萝卜中的β-胡萝卜素含量明显降低,油菜中VC的含量也明显降低;通电加热烫漂后的维生素含量明显高于电炉加热;而胡萝卜通电加热的最佳烫漂工艺为,烫漂时间3 min,颗粒尺寸10 mm,料液比(g:mL)1∶4,电压220 V;油菜通电加热烫漂的适宜工艺条件为料液比(g:mL)1∶4,烫漂时间0.5 min,电压220 V。     

Comparative Effects of Ohmic,Induction Cooker,and Electric Stove Heating on Soymilk Trypsin Inhibitor Inactivation

During thermal treatment of soymilk, a rapid incorporation of Kunitz trypsin inhibitor (KTI) into protein aggregates by covalent (disulfide bond, SS) and/or noncovalent interactions with other proteins is responsible for its fast inactivation of trypsin inhibitor activity (TIA). In contrast, the slow cleavage of a single Bowman–Birk inhibitor (BBI) peptide bond is responsible for its slow inactivation of TIA and chymotrypsin inhibitor activity (CIA). In this study, the effects of Ohmic heating (220 V, 50 Hz) on soymilk TIA and CIA inactivation were examined and compared to induction cooker and electric stove heating with similar thermal histories. It was found that: (1) TIA and CIA inactivation was slower from 0 to 3 min, and faster after 3 min as compared to induction cooker and electric stove. (2) The thiol (SH) loss rate was slower from 0 to 3 min, and similar to induction cooker and electric stove after 3 min. (3) Ohmic heating slightly increased protein aggregate formation. (4) In addition to the cleavage of one BBI peptide bond, an additional reaction might occur to enhance BBI inactivation. (5) Ohmic heating was more energy‐efficient for TIA and CIA inactivation. (6) TIA and CIA inactivation was accelerated with increasing electric voltage (110, 165, and 220 V) of Ohmic heating. It is likely that the enhanced inactivation of TIA by Ohmic heating is due to its combined electrochemical and thermal effects.     

Does Electroporation Occur During the Ohmic Heating of Food?

ABSTRACT: The effect of temperature on electroporation of plant tissues during the pulsed electric field (PEF) or alternative current (AC) treatment was studied. The characteristic damage time t, which determines effectiveness of the electroporation mechanism in plant tissue damage, was estimated for potatoes tissues in the range of electric field strengths E = 40 to 500 V/cm and at temperatures T = 22°C and T = 49 °C in PEF treatment experiments. Experimental results of the AC ohmic heating of potato and apple tissues are evidence of the importance of the electroporation mechanism of tissue damage at moderate electric fields (MEF), when the electric field strength E is under 100 V/cm, and show that effectiveness of this mechanism increases with temperature increase.