食品冷冻理论和技术的进展

冷冻贮藏对食品保藏和运输具有重要意义,冷冻食品加工行业发展势头良好,与食品冷冻相关的理论与技术也有长足的进展。本文介绍了与食品冷冻过程相关的传递、玻璃化转变和冰结晶理论的现状和进展,指出由食品物料及其在冷冻过程变化的特殊性所引起的建立系统的食品冷冻理论的复杂性;综述了超声强化冷冻、高压冷冻、冷冻蛋白技术、CAS冻结系统和冰温技术的简要原理,及其在食品行业的应用进展。      

食品冷冻技术研究现状及进展

冷冻是一种食品加工与贮藏方式,早在公元前便已经被人们所利用.随着现代科学技术的发展,越来越多的新技术被应用于食品冷冻领域.本文对近些年来新出现的食品冷冻技术以及其原理和应用进行介绍,并简要阐述了当今国内外食品冷冻技术的发展趋势,并对我国食品冷冻技术未来的发展做出了展望.     

冷冻食品技术

中国经济发展迅速,出口及本士市场都要求高质产品,对于先进食品加工及处理设备的需求也与日俱增。     

冷冻食品和微波炉食品包装技术

冷冻食品在世界各国市场上销路畅旺,日本1987年消费总量已突破100万吨大关,预计1988年仍将增加约15%,达到120万吨左右。冷冻食品除冷冻油炸食品,冷冻汉堡包之外,品种已达1000多种。其中速冻食品占70%,而在加工食品中调理冷冻食品的普及率已达73.1%,今后可能增加到85.5%。     

冷冻技术在烘焙食品中的应用

对烘焙食品中冷冻面团技术生产方法及其技术要点作了较详介绍。     

冷冻食品的冰结技术与应用

本文对冻结装置的原理与特点、国外新兴冻结技术作了介绍，提供冻结装置在工程配套（设计）中的选用原则。     

肉类冷冻理论与冷冻新技术

介绍了肉类冷冻的主要理论,包括传递理论、玻璃化转变理论和冰结晶理论;对目前出现的冷冻新技术如高压冷冻技术、超声冷冻技术、冰核细菌冷冻蛋白技术、CAS冻结系统和减压冷冻技术进行了综述。     

冷冻食品的生产和品质管理

冷冻食品生产技术：原料选定，调理制造，冻结保存，卫生管理，包装处理。冷冻食品品质管理：规格整齐，符合卫生要求。     

食品添加剂在冷冻面团技术中的应用

文章简单阐述了冷冻对烘焙食品品质的影响及影响其品质的物理因素,并对食品添加剂在冷冻面团技术中的最新研究与应用进行了重点综述.     

冷冻工艺对豆腐品质的影响研究

冻豆腐具有特殊的口感和丰富的营养,深受消费者的喜爱。本文主要研究了冷冻工艺对豆腐品质的影响,并对其进行优化,最后得出的最佳工艺条件为:–0℃下冷冻3.5 h,–3℃下熟化21 d。     

Prediction of frozen food properties during freezing using product composition

ABSTRACT:  Frozen water fraction (FWF), as a function of temperature, is an important parameter for use in the design of food freezing processes. An FWF-prediction model, based on concentrations and molecular weights of specific product components, has been developed. Published food composition data were used to determine the identity and composition of key components. The model proposed in this investigation had been verified using published experimental FWF data and initial freezing temperature data, and by comparison to outputs from previously published models. It was found that specific food components with significant influence on freezing temperature depression of food products included low molecular weight water-soluble compounds with molality of 50 μmol per 100 g food or higher. Based on an analysis of 200 high-moisture food products, nearly 45% of the experimental initial freezing temperature data were within an absolute difference (AD) of ± 0.15 °C and standard error (SE) of ± 0.65 °C when compared to values predicted by the proposed model. The predicted relationship between temperature and FWF for all analyzed food products provided close agreements with experimental data (± 0.06 SE). The proposed model provided similar prediction capability for high- and intermediate-moisture food products. In addition, the proposed model provided statistically better prediction of initial freezing temperature and FWF than previous published models.     

Recent developments in smart freezing technology applied to fresh foods

Due to the increased awareness of consumers in sensorial and nutritional quality of frozen foods, the freezing technology has to seek new and innovative technologies for better retaining the fresh like quality of foods. In this article, we review the recent developments in smart freezing technology applied to fresh foods. The application of these intelligent technologies and the associated underpinning concepts have greatly improved the quality of frozen foods and the freezing efficiency. These technologies are able to automatically collect the information in-line during freezing and help control the freezing process better. Smart freezing technology includes new and intelligent technologies and concepts applied to the pretreatment of the frozen product, freezing processes, cold chain logistics as well as warehouse management. These technologies enable real-time monitoring of quality during the freezing process and help improve product quality and freezing efficiency. We also provide a brief overview of several sensing technologies used to achieve automatic control of individual steps of freezing process. These sensing technologies include computer vision, electronic nose, electronic tongue, digital simulation, confocal laser, near infrared spectroscopy, nuclear magnetic resonance technology and ultrasound. Understanding of the mechanism of these new technologies will be helpful for applying them to improve the quality of frozen foods.     

电导率仪测定食品冰点方法的研究

通过观测多种液态和固态食品物料的温度和电导率的关系,发现当温度降至食品物料冰点时,电导率就急剧下降。本试验测定出王老吉凉茶、可口可乐、玉米浓浆的冰点分别为-1.8,-2.0,-2.2℃;新鲜罗非鱼片、南美白对虾、黄冠梨的冰点分别为-1.3,-1.5,-1.2℃。     

杨梅液浸式超速冻藏保鲜工艺的研究

杨梅贮藏是公认难题,长时间贮藏更难。以浙江红杨梅作为实验原材料,首次利用液浸式超速冷冻技术进行速冻保鲜,研究了杨梅液浸式超速冷冻技术的最佳工艺,分析了不同成熟度的杨梅果实其品质比较,以及不同速冻温度下杨梅果实的冻结规律曲线、感官品质、汁液流失率、可溶性固形物、相对电导率、△E值、质构特性等各项指标的变化规律。结果表明:选择九成熟的浙江红杨梅作为原材料,采后立即预冷,用0.07mm的PVC保鲜袋进行真空包装后,在-45℃下进行液浸式超速冷冻12min,于-18℃冰箱中冻藏90d之后,杨梅果实感官品质良好,说明该技术便于产业化。研究不仅对杨梅较长期保鲜具有重要意义,而且对浆果型果蔬保鲜具有重要理论意义和参考价值。      

数值模拟在食品冻结过程中的应用

文章主要通过综述冻结过程的数值模型、求解微分方程、预测冻结时间及分析送风速度、温度和送风方式等,讨论数值模拟技术在食品冻结过程中的应用现状;总结了国内外研究者针对不同冻结对象所采用的数值模拟方法,为今后数值模拟方法在食品传热过程中进一步发挥作用提供理论参考。     

红外技术在食品工业中的应用

介绍了红外技术在食品工业应用及其原理，着重讲述了近红外的检测技术应用和远红外加热和杀菌技术应用，并分析了光波炉的工作原理、干燥原理以及近红外技术的特点。并给出了一些比较实例，指出了红外技术应用的发展趋势。     

Effects of blanching and freezing on the structure of carrots cells and their implications for food processing

Blanching and freezing effects are focused on the microscopic structure, whether the softening of frozen vegetables (carrots) is related to changes in pectic substances or to firmness. Under light and electron microscopy, in the frozen raw samples, some cells were disrupted, producing cavities. The cytoplasm was destroyed and enclosed in a very thin layer inside the cell, and the organelles attached to the plasmalemma had almost disappeared. The formation of a transparent region close to the plasmalemma was observed, as a result of the extraction of some altered materials (hemicellulose, cellulose, pectin). The cell walls in the blanched samples appeared quite different from those in the frozen samples. They did not display tissue disruption as in the frozen samples, but the organelles in the cytoplasm were also altered. We also report substantial vesicle formation (swollen walls) in the cell wall, and a dark granular material inside. When the blanched samples were also frozen, compartmentalization of the material inside was observed. The pectin content was higher in the frozen and frozen blanched samples than in the raw and blanched samples. The semithin and ultrathin structure was in accordance with the objective values obtained by Kramer/Shear cell, where the greatest damage occurred to the samples in the freezing process. © 1998 SCI.     

用于食品冷冻温度控制的模糊控制系统设计

目的:提高食品进入冷冻隧道的速度控制回路和温度控制回路的设定值调整能力。方法:对传送带速度和温度控制回路进行了单独处理,设计用于食品冷冻温度控制的模糊控制系统。该控制系统包括用于食品传送带滚子转速的比例—积分—微分控制器、用于冷冻隧道温度调节的比例—积分控制器,并采用Takagi-Sugeno模糊控制器来设定温度调节比例—积分控制器的温度设定点。结果:待冷冻食品的质量流量从650 kg/h增加到700 kg/h、驱动辊的转速从1.62 r/min增加到1.75 r/min时,最终食品温度可快速恢复到约-18℃;食品入口发生+5℃的温度干扰时,模糊控制器动作,从而将食品的出口温度保持在预期值-18℃附近。结论:所设计的控制系统通过选择允许快速响应和相对较低超调的系统参数,可实现输出变量的值不会在设定值附近出现大幅波动。     

冷冻速率对面团发酵和烘焙性质的影响

研究了冷冻速率对冷冻面团体系中酵母发酵(包括酵母产气力、酵母存活率)和面团微结构的影响;以及对冷冻面团烘焙性质的影响(包括面包比容,面包评分和面包保质期).结果显示冷冻速率同时影响酵母活力和面团的超微结构,进而影响面包的品质和体积,综合考虑,确定面团在-32℃下快速冷冻至-18℃(冷冻速率约-5℃/min),并在-18℃下冻藏,较适合冷冻面团的生产.