通电加热技术的特点及其在肉制品加工中的应用

通电加热技术与传统加热技术和微波加热技术相比在食品加工方面具有明显的优势，在食品的加热处理和解冻方面有着很大的发展潜力。本文介绍了通电加热技术的基本原理和主要特点，阐述了在对内的乳状液进行加热处理和对冷冻内进行解冻方面的应用并对其作了分析，提出了存在的问题，展望了其发展前景。     

通电加热技术的特点及其在肉制品加工中的应用

通电加热技术与传统加热技术和微波加热技术相比在食品加工方面具有明显的优势，在食品的加热处理和解冻方面有着很大的发展潜力。介绍了通电加热技术的基本原理和主要特点，阐述了在对肉的乳状液进行加热处理和对冷冻肉进行解冻方面的应用，并对其作了分析，提出了存在的问题，展望了其发展前景。     

不同加热温度加热卷烟抽吸过程中烟芯段气溶胶的动态分布

为研究加热温度对加热卷烟烟芯段气溶胶动态分布的影响,将加热卷烟样品与不同加热温度的同一加热器具配套使用,采用气溶胶原位表征系统对加热卷烟烟芯段各测试点的气溶胶进行原位取样和在线测试,考察了300、330和360℃3个加热温度条件下加热卷烟抽吸过程中烟芯段气溶胶主要物理特性的动态分布;进一步采用热电偶法对不同加热温度加热卷烟烟芯段的温度场进行表征,阐明温度分布对气溶胶分布的影响。结果表明：(1)不同加热温度条件下,烟芯段释放至空腔段的气溶胶粒径均呈现近似正态对数分布,随加热温度的升高,气溶胶的粒径和粒数浓度均增大。(2)不同加热温度条件下,烟芯段气溶胶的粒数中值粒径、粒数浓度和体积浓度均呈现相似的分布趋势,较大的粒数中值粒径、较高的粒数浓度和体积浓度主要分布于靠近加热片的中前段。(3)随加热温度的升高,烟芯段气溶胶的较大粒数中值粒径、较高粒数浓度和体积浓度分布区域呈明显的增加趋势。(4)加热卷烟烟芯段的温度分布与气溶胶分布直接相关,高温区域由于高浓度蒸汽成分的存在而有利于气溶胶的形成。     

微波加热预处理大豆对磷脂和豆粕品质的影响

应用频率2450MHz、功率650W之微波炉对整粒大豆进行预处理加热试验。在不同的加热时间条件下,对其提取的油脂与豆粕质量指标(水化脱胶油中NHP含量、PDI指数等)进行分析与测定。其结果初步表明:应用微波加热新技术,对钝化酶,提高豆粕蛋白质与油脂的品质行之有效。与传统热传导加热处理方式(蒸汽、热空气、导热油等)相比,微波加热具有时间短、选择性好的特点。并指出:本实验条件之最佳热处理时间为1 1/3min至2.5min。为兼顾豆粕与油脂品质的最优化,笔者提出:适当延长微波加热恒温阶段的时间、采用必要的低温处理作为工艺依据。相应的技术措施有如:调节水分、料层厚度与操作压力以及采取气流干热与微波真空干热预处理相结合的节能工艺等。     

不同加热处理对牦牛肉风味组成和质构特性的影响

取西藏种萨牦牛肉,研究不同热处理方式(微波加热、高压炖煮和常温水煮)对牛肉风味和质构特性的影响。结果表明：这3种热处理得到的牦牛肉产品风味化合物主要包括脂肪烃、脂环烃、脂肪醛、脂肪酮、芳香烃、含硫化合物和脂肪醇6大类,其中醛类化合物(己醛、壬醛和辛醛等)为熟牦牛肉的特征风味。微波加热形成的风味种类最高,达137种,高压炖煮次之(133种),常温水煮最差(128种),微波加热形成的醛类化合物达10种,高压炖煮形成的醛类化合物为5种,而常温水煮形成醛类化合物为4种。对微波加热、高压炖煮和常温水煮3种加热方式形成的牛肉进行质地剖面分析,表明微波加热形成的牛肉硬度低、弹性高等最佳质感效果。综合风味指标、质构指标和感官评价指标,确认微波加热牦牛肉品质最优。     

射频解冻过程中食品加热均匀性影响因素的研究进展

射频加热(radio frequency, RF)技术作为一种新兴加热技术，是一种高效、低能耗的可替代传统加热的热处理方法。该方法在提高工业效率的同时又可保证食品的质量安全性及品质，可满足食品工业中的解冻以及其他加工需求，在食品工业中具有越来越大的应用潜力和发展前景。但解冻过程中存在的“边缘效应”等加热不均匀问题仍是制约该技术的一个瓶颈。本研究对射频解冻及其原理进行了介绍，并总结了影响解冻过程中加热均匀性等问题的因素，包括电磁场、射频功率、电极电压及间隙、食品的介电特性等，以期为射频解冻技术的研究及改善加热均匀性等未来研究发展方向提供参考。     

电物理加热技术及其在食品工业中的应用

电物理加热作为一种新型加热技术,正逐渐在食品工业中得到应用.介绍了微波加热、欧姆加热、远红外线加热、射频加热等电物理加热技术,并对其在食品工业中的应用进行了讨论.     

感应加热技术的发展及应用

感应加热是一种清洁高效的热处理方法。简要介绍感应加热的原理和工艺,并结合国内外感应热处理的研究现状展望感应加热新技术的发展趋势。     

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。     

梳理机用齿条感应加热电源频率跟踪的控制策略

利用感应加热技术对梳理机用齿条进行在线退火热处理,可以显著提高其生产效率和产品质量.由于梳理机用齿条在加热过程因参数变化会导致感应加热电源的谐振频率变化,致使电源的利用率降低.为提高电源的利用效率和功率因数,要求电源的输出电压与谐振电流的频率、相位严格保持一致.根据梳理机用齿条热处理工艺的要求,采用积分分离法与DPLL(数字锁相环)相结合的频率跟踪策略,设计了一台100kHz/5 kW的高频感应加热电源,对齿条进行在线退火处理.该电源采用Buck斩波实现功率控制;采用负载串联谐振式逆变桥进行频率控制,实现对负载谐振频率的跟踪和软开关.电源的功率调节范围为1%～99%,输出功率因数达到99%,与传统技术相比,该高频感应加热电源具有调功范围大、结构简单、抗干扰能力强、节能显著、加热温度均匀等优点.     

Oxidation of chlorinated ethenes by heat-activated persulfate: kinetics and products

In situ chemical oxidation (ISCO) and in situ thermal remediation (ISTR) are applicable to treatment of groundwater contaminated with chlorinated ethenes. ISCO with persulfate (S2O8(2-)) requires activation, and this can be achieved with the heat from ISTR, so there may be advantages to combining these technologies. To explore this possibility, we determined the kinetics and products of chlorinated ethene oxidation with heat-activated persulfate and compared them to the temperature dependence of other degradation pathways. The kinetics of chlorinated ethene disappearance were pseudo-first-order for 1-2 half-lives, and the resulting rate constants-measured from 30 to 70 degrees C--fit the Arrhenius equation, yielding apparent activation energies of 101 +/- 4 kJ mol(-1) for tetrachloroethene (PCE), 108 +/- 3 kJ mol(-1) for trichloroethene (TCE), 144 +/- 5 kJ mol(-1) for cis-1,2-dichloroethene (cis-DCE), and 141 +/- 2 kJ mol(-1) for trans-1,2-dichloroethene (trans-DCE). Chlorinated byproducts were observed, but most of the parent material was completely dechlorinated. Arrhenius parameters for hydrolysis and oxidation by persulfate or permanganate were used to calculate rates of chlorinated ethene degradation by these processes over the range of temperatures relevant to ISTR and the range of oxidant concentrations and pH relevant to ISCO.     

Thermal pretreatments of carrot pieces using different heating techniques: Effect on quality related aspects

During fruit and vegetable processing, different thermal processes (blanching, pasteurization, sterilization) based on different heating techniques can be used. In this context, it is important to evaluate the impact of blanching on quality related parameters.This paper describes a case study on carrot pieces, studying the effect of thermal pretreatments (high temperature blanching, low temperature blanching and low temperature blanching in combination with Ca²⁺-soaking) on enzyme activity (peroxidase (POD), pectinmethylesterase (PME)), structural properties (degree of methoxylation (DM), texture) and nutritional aspects (β-carotene content). The thermal pretreatments were carried out by conventional heating as well as by microwave heating and ohmic heating, since these new heating methods can become important new technologies in food industry.It has been shown that, depending on the application, selecting the right pretreatment conditions can help to control the enzyme activity. To obtain a firm carrot texture after thermal processing, low temperature blanching seems to be the most appropriate pretreatment condition. This was supported by the micrographs and the analysis of the degree of methoxylation. Furthermore almost no influence of the pretreatments on the β-carotene content of the samples could be noticed. For all quality parameters studied, no unambiguous effect of the heating technique could be detected. Thus, the time/temperature conditions of the thermal pretreatments determine the quality related aspects, independent of the heating technique used.

Industrial relevance

With regard to consumer acceptance, a good quality control of fruit and vegetables is important. Food quality covers a wide range of parameters, including enzyme content, structural properties, nutritional properties, sensorial characteristics etc. This study gives an overview of the effect of blanching, which is a common preprocessing step in food processing, on quality related parameters in carrots. The data deliver integrated information on structural level as well as on nutritional level and on enzyme content. Moreover, novel thermal process technologies (microwave heating, ohmic heating), which gain more and more attention in food industry, are being considered as alternatives for conventional blanching.     

连作条件下植烟土壤保育与修复

针对山地烟区连作问题持续存在的现状,对典型烟区和烟农进行了广泛深入调查分析,围绕连作条件下土壤酸碱度调控,团粒结构改善,有益微生物群落恢复等方面开展了大量研究工作,形成了冬耕冻土、绿肥还田、施用有机肥、硝酸钾部分替代硫酸钾、施用陪嫁土和生石灰等土壤保育与修复的相关技术措施。通过大面积推广与应用,取得了良好成效,可为开展土壤生态保护工作提供有益参考。     

微波与远红外线加热在食品加工中的应用

不同的加热处理方法是实现高品质加工食品的关键。本文概述了现今国内外食品加工工业中普遍采用的两种加热技术 :微波加热、远红外线加热技术 ;并详细阐述了这两种加热技术各自的特征、加热原理及其在食品加工过程中的广泛应用。     

制冷与制热空调服的研究进展

针对人体在高温或高寒环境中长时间工作可能导致中暑、热痉挛、低体温症等疾病的问题,在介绍人体体温调节基本原理和换热机制的基础上,着重介绍了利用制冷或制热空调服对人体体温进行主动调节的基本原理,同时归纳和总结了现阶段各类制冷制热空调服的工作原理,并比较了其优缺点。在制冷空调服领域,着重介绍了空气冷却、相变冷却、冰袋冷却、液体冷却等主被动降温方法;在制热空调服领域,着重介绍了电热、相变制热、化学制热等方法。在空调服未来的发展方向上,伴随可穿戴技术的发展,提出了可穿戴技术与空调服结合应用的新构想,对同时具有生命体征监测和体温调节功能的新型空调服进行了展望。     

钢丝的感应加热(待续)

对比内热式、外热式钢丝加热方式的特点,指出采用感应加热技术应当满足的技术条件;利用一系列公式介绍感应加热系统的参数计算方法,从加热工件的电磁能、电流穿透层、感应器的结构参数等方面介绍了钢丝的感应加热系统;分析细钢丝感应加热面临的2个技术难题,讨论钢丝感应加热温度均匀化及稳定化处理生产线的保温问题。     

Mild processing of seafood—A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.     

加热方式和加热时间对鱼类明胶理化性质的影响

为探究加热方式和加热时间对鱼类明胶理化性质的影响,对加热明胶溶液的蛋白组成、粘度、流变性质和热稳定性,以及明胶凝胶的强度、质构（texture profile analysis,TPA）参数和微观结构进行分析和比较。结果显示,鱼类明胶溶液的粘度、流变性质及热稳定性随加热时间的增加而明显降低,但间歇加热明胶中这些性质的变化幅度均低于连续加热明胶。连续加热明胶至48 h时电泳图谱中β条带消失,96 h时α₁和α₂亚基明显降解,而当间歇加热明胶至96 h时β条带才消失。鱼类明胶形成的凝胶其强度和TPA参数随热处理时间的延长逐渐减小,但间歇加热明胶的凝胶形成能力优于连续加热明胶。扫描电子显微镜结果显示,连续加热的凝胶表面光滑平整,而间歇加热凝胶的结构更加粗糙且多孔隙。研究结果表明,间歇加热及加热时间小于12 h有利于减少明胶热降解。     

Thermal performance of a flat ohmic cell under non-fouling and whey protein fouling conditions

Temperature gradients, between electrode surfaces and bulk, in a continuous flat ohmic cell under whey protein fouling were studied. The temperature profiles in non-fouled cell were studied using two Newtonian fluids (water and an aqueous solution of sucrose at 55 g/100 g) and a pseudoplastic fluid (an aqueous solution of xanthan gum at 0.2 g/100 g). The temperature gradients were studied using two fouling fluids: an aqueous solution of β-lactoglobulin and an aqueous solution of β-lactoglobulin-xanthan gum mixture. Obtained result shows the existence of a temperature difference between electrode surfaces and the bulk when heating non-fouling fluids. The value and the shape of these gradients depend on the Reynolds number and the rheological behavior of the fluid. Under fouling conditions, the temperature gradient obtained at different Reynolds number exhibit a different trend. These differences could be explained by the effect of differential electrical conductivities between the bulk and the deposit, and the balance between heat generation by electrical power dissipation and thermal loss by convection (with the fluid) and conduction (with the electrode surfaces).

Significance for the science community and food industry

Food industry and in particularly the dairy industry, are faced with a severe problem due to equipment fouling during processing. Therefore, the development of alternative technologies for fouling limitation is of scientist and industrial relevance. Ohmic heating is one of these technologies, where the theoretical volume heating aspect should provide a considerable advantage to limit fouling phenomena. The present study evaluates the capability of a rectangular ohmic unit to provide a homogenous heat treatment of complexes dairy fluid (fluid rheology, flow rate and fouling presence).     

升温方式对鲢鱼肌球蛋白结构和理化性质的影响

为探究升温方式对肌球蛋白结构和性质的影响,本实验比较和分析了不同升温条件（空白（传统水浴二段加热,即水浴40 ℃加热30 min,90 ℃加热20 min）;低温段和高温段分别采用水浴升温（water bath heating,WH）、微波升温（microwave heating,MH）或微波辅助水浴升温（microwave assistant water bath heating,MWH）3 种方式升温至40 ℃或90 ℃,到达此温度后再置于水浴锅中加热）对鲢鱼（Hypophthalmichthys molitrix）肌球蛋白的结构和理化性质（总巯基含量、表面疏水性、浊度、溶解度、二级结构、三级结构和热稳定性）的影响。结果表明：MH和MWH与WH相比显著缩短了升温时间,提高了加热效率;低温段MWH促进肌球蛋白展开,WH的肌球蛋白变性程度大,高温段MH的肌球蛋白变性程度高,二级和三级结构对微波敏感,暴露更多的氨基酸残基。MWH在提高升温速率的同时避免了升温速率过快,低温段采取MH或MWH有利于凝胶化,高温段采取WH能够促进肌球蛋白聚集。