Recent Advances in Food Thawing Technologies

Serious quality deterioration can occur with suboptimal thawing, and thus innovative thawing technologies may have an important role in improving the final quality of frozen foods. In recent years, although several new thawing technologies have been extensively studied, such as ultra‐high pressure assisted thawing, ultrasound‐assisted thawing, high‐voltage electrostatic field thawing, ohmic thawing, and radio frequency thawing, more research is needed to make them more applicable to thawing of food industrially. A better evaluation of the impact of thawing is needed to help move new thawing technologies forward. This review discusses the principles involved, the applications to different types of foods, modeling of the various processes, new evaluation techniques, and patents obtained for the different systems. The benefits and weaknesses of these systems are also discussed to provide a more complete review of these new thawing techniques. This review will, hopefully, encourage additional work that may help reach the goal of having better food thawing systems.     

超高压处理对鸡肉品质影响的研究进展

超高压是超过100MPa的压力,作为一种新型的食品加工技术,超高压具有抑菌、改善肉质、节能等优点。本文综述超高压处理对鸡肉的色泽、嫩度、脂肪氧化、微生物及冻结和解冻等方面的影响。     

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.     

食品的低温高压处理技术及其研究进展

文中介绍了低温高压处理技术的基本原理、应用范围和研究进展。在 0～ 6 32 4MPa范围内 ,高压下水的冻结点均较常压下的低 ,并在低于 0℃的温度下形成一个水的不冻结区域。高压还使水的体积收缩、温度升高。低温高压处理技术可应用于食品杀菌和抑酶、高压冻结和高压解冻、低温高压不冻结贮藏。低温高压具有比常温高压更好的杀菌效果 ;高压冻结和高压解冻可缩短食品冻结和解冻的时间、改善冻藏食品的品质 ;低温高压下的不冻结贮藏能更好地保持食品原有的风味和质地     

物理场技术在水产品冷冻冷链中的应用

在冷链流通过程中, 对新鲜水产品进行冷冻处理能够大大提高其保质期。然而, 传统的冷冻和解冻方法有传热效率低、耗时较长的缺陷, 且难以控制冰晶对食品原料的损伤。所以冷冻水产品经常会面临一系列的质量问题, 如质构劣化、蛋白质变性、持水能力下降等。因此有必要采用高效的冷冻/解冻技术以防止品质劣变。相比于传统方法, 基于物理场(如高压、超声、电场等)的新型冷冻和解冻技术具有高冷冻/解冻速率、低能耗、对产品品质维持更好等优点。本文综述了近年来物理场技术在水产品中的应用, 分析了它们各自的原理、特点、缺陷及未来的发展趋势, 为这些新技术在水产品冷冻冷链中的应用提供相关参考。     

高压电场对生鲜食品保鲜机理研究进展

生鲜食品新鲜程度直接影响市场需求,其产后腐败带来的经济损失也不可估量,因此保鲜技术研究至关重要。高压电场在处理食品时具有无热效应、能耗极小、食品温度上升幅度小、对食品本身品质基本无影响等特点,是目前生鲜保鲜领域应用前景最好的技术之一。本文介绍了高压电场的基本原理,分别从膜电位、酶活性和微观质地等方面系统分析了其在果蔬、水产品和肉类食品中的保鲜作用机理,并进一步对高压电场未来的研究前景进行展望。     

Novel assistive technologies for efficient freezing of pork based on high voltage electric field and static magnetic field: A comparative study

To enhance the freezing rate and thawed product quality of pork tenderloin, an experimental study was conducted using the high voltage electric field and static magnetic field separately during freezing. Pork tenderloin pieces were frozen at −20 °C under several high voltage electric fields (10 kV/m (HVEF1), 30 kV/m (HVEF3), 50 kV/m (HVEF5)) and magnetic fields of 2 mT (MF2), 4 mT (MF4), 6 mT (MF6) and 8 mT (MF8). The effects of different methods on freezing rate, ice crystal size as well as the distribution, and product quality after thawing were investigated. The freezing time of pork tenderloin was reduced by 40.04% and 37.81% respectively, under the optimal electric and magnetic field conditions tested. The thawing loss decreased from 5.7% of conventional freezing to 1.7% of HVEF1 and 2.4% of MF2, respectively. In addition, both high-voltage electric field freezing and magnetic field freezing can better maintain the moisture state in the sample. The results for color and pH confirmed that the thawed product quality using HVEF1 and MF2 was superior to that obtained under other conditions. The myofibrillar protein in the thawed products obtained from HVEF1 and MF2 treatments was also found to be thermally more stable. It is noteworthy that the HVEF1 treated sample has the highest umami signal and the lowest salty signal. Considering the enhanced freezing efficiency and improved quality, application of HVEF1 is recommended as a viable strategy to produce high-quality frozen pork tenderloin.Industrial relevanceThe slow freezing rate of frozen meat products and serious deterioration of product quality are the key problems. Therefore, improving the efficiency of freezing is desirable. This study provides ideas for pork preservation. It caters to the need of industrial production of meat product where better efficiency freezing process is highly desirable, and the findings of this study is beneficial to the meat processing industry.     

超声辅助冷冻技术的作用机制及其对食品品质影响的研究进展

冷冻是一种重要的食品保藏技术,但冻结也会引起食品品质的变化。作为一项高新加工技术,超声辅助冷 冻技术可以加快冷冻速率,减小冰晶的尺寸,进而改善冷冻食品的品质。本文主要论述了超声辅助冷冻技术的作用 机制及对冰结晶形成的影响,同时综述了超声辅助冷冻技术对食品品质的影响及食品冷冻中常用的工艺参数。最 后,展望了超声辅助冷冻技术的发展方向,为超声辅助冷冻技术在食品中的应用提供理论支持。     

Parametric Analysis for Thawing Frozen Spheroidal (Prolate and Oblate) or Finitely Cylindrical Food

A screening analysis was performed to determine the influence of independent parameters (18) on thawing times of frozen spherical (prolate and oblate) and finitely cylindrical foods using a computerized simulation procedure assuming food volume shrinkage from density changes and temperature dependent physical properties. Of 18 independent parameters, 6 were significant for both foods: thawing medium temperature, initial freezing point, Biot number, radiative heat exchange, a parameter for effective specific heat and shape factor (nonsignificant influence of volumetric changes). Predictive regression equations were developed for estimating thawing time as function of significant parameters. Predictive equations were validated experimentally. A sensitivity analysis showed errors in thawing time were influenced most strongly by food dimensions, followed by operational temperatures, thermophysical properties and convective surface heat-transfer coefficient.     

速冻设备流场优化研究进展

速冻是食品保鲜的重要技术之一,冻结速率越快,速冻食品解冻后品质越好。冻品表面风速越高,换热强度越大,冻结速率则越快。若只增加风机转速会导致风机效率降低,流场不均匀度增加,因此需要对流场进行优化。对风机设置锥形口等引导流体设施,可以增加风机效率;在流场中设置导流板,可以消除流场中的涡流;增加冷冻区域流速,可以加强食品表面的对流换热;隔断设备内外的空气交换,可以减少蒸发器结霜,降低设备的冷负荷。文章指出将多种措施结合,减少制造与维护的成本、节省运行费用与提高冻品质量是未来速冻设备优化的方向。     

Radio frequency heating of foods: principles, applications and related properties--a review

Radio frequency (RF) heating is a promising technology for food applications because of the associated rapid and uniform heat distribution, large penetration depth and lower energy consumption. Radio frequency heating has been successfully applied for drying, baking and thawing of frozen meat and in meat processing. However, its use in continuous pasteurization and sterilization of foods is rather limited. During RF heating, heat is generated within the product due to molecular friction resulting from oscillating molecules and ions caused by the applied alternating electric field. RF heating is influenced principally by the dielectric properties of the product when other conditions are kept constant. This review deals with the current status of RF heating applications in food processing, as well as product and system specific factors that influence the RF heating. It is evident that frequency level, temperature and properties of food, such as viscosity, water content and chemical composition affect the dielectric properties and thus the RF heating of foods. Therefore, these parameters should be taken into account when designing a radio frequency heating system for foods.     

新技术在食品冷冻过程中的应用

文中对超声冷冻技术、高压冷冻技术、冰核活性细菌和冰核活性蛋白及抗冻蛋白在食品冷冻过程中的应用作一介绍。     

Post-thawing quality changes of common carp (Cyprinus carpio) cubes treated by high voltage electrostatic field (HVEF) during chilled storage

In recent years, high voltage electrostatic field (HVEF) technology has been demonstrated to be a viable alternative to high-temperature treatments in processing for inhibiting microbial growth and maintaining post-thawing quality of foods. In this study, common carp (Cyprinus carpio) meat cubes were treated with HVEF, and compared to air-thawed and running tap water-thawed controls to investigate how HVEF affects common carp meat quality after thawing and low-temperature storage (4 °C). The results showed that thawing under − 6, − 12 kV HVEF and running tap water significantly decreased the thawing time by 30, 50 and 45 min, respectively, compared to air thawing control. In addition, − 12 kV HVEF treatment also reduced the moisture loss, which the initial drip loss of it was lower by 2.95% than CK. The initial total viable counts, Aeromonas, Pseudomonas, and lactic acid bacteria were 3.58, 3.15 2.88 and 3.25 log CFU/g in CK after thawing, respectively, which were higher than that in the cube thawed by − 12 kV HVEF (3.11, 2.93 2.71 and 2.91 log CFU/g). Additionally, − 12 kV HVEF treatment enhanced adenosine monophosphate deaminase (AMP-deaminase) activity, reduced acid phosphatase (ACP) activity and delayed the degradation of inosine monophosphate (IMP) to hypoxanthine (Hx). These results suggested that HVEF treatment could be useful in the thawing and storage of frozen common carp fish.Industrial relevanceThe study investigated the effects of high voltage electrostatic field (HVEF) thawing on the water-holding capacity, adenosine triphosphate degradation and microbial community changes of frozen common carp (Cyprinus carpio) cubes when stored at 4 °C. HVEF under − 12 kV was found to have positive influence on reducing the thawing time, maintaining water-holding capacity, decreasing the level of microbe, and delaying adenosine triphosphate (ATP) degradation. A potential application for HVEF in the thawing and storage of frozen aquatic product was highlighted in food industry.     

冻结和解冻过程对水产品品质的影响

冻结是水产品保鲜的一种有效的方法,冻结后的水产品一般会进行冻藏。影响冻品质量的因素很多,主要有冻结速率、冻藏温度、解冻速率、冻藏中温度波动、冻结-解冻循环次数等。本文在简要介绍食品的冻结解冻方法的基础上,综述了冻结解冻过程对水产品物理、化学特性的影响。     

A comprehensive review of the principles,key factors,application, and assessment of thawing technologies for muscle foods

For years, various thawing technologies based on pressure, ultrasound, electromagnetic energy, and electric field energy have been actively investigated to minimize the amount of drip and reduce the quality deterioration of muscle foods during thawing. However, existing thawing technologies have limitations in practical applications due to their high costs and technical defects. Therefore, key factors of thawing technologies must be comprehensively analyzed, and their effects must be systematically evaluated by the quality indexes of muscle foods. In this review, the principles and key factors of thawing techniques are discussed, with an emphasis on combinations of thawing technologies. Furthermore, the application effects of thawing technologies in muscle foods are systematically evaluated from the viewpoints of eating quality and microbial and chemical stability. Finally, the disadvantages of the existing thawing technologies and the development prospects of tempering technologies are highlighted. This review can be highly instrumental in achieving more ideal thawing goals.     

Microstructure of high-pressure vs. atmospheric frozen starch gels

The aim of this study was to find out whether the ice crystal size of a starch gel, a model food system, could be reduced by high-pressure freezing compared with freezing at atmospheric pressure. The size and number of pores in thawed gels was determined by light microscopy and image analysis, and was taken as an indirect measure of ice crystals formed during the different freezing processes studied.The pore size and the total area occupied by the pores were clearly reduced by high-pressure freezing at 150–240 MPa compared with freezing at atmospheric pressure at the same cooling rate. The pore size in the high-pressure (nor in the atmospheric) frozen gels did not increase during a storage time of 3 months at − 24 °C (still air) at atmospheric pressure.Industrial relevanceHigh-pressure processing at subzero temperatures is not yet industrially applied. More evidence on the benefits of high-pressure freezing or thawing on the quality of real food materials as well as development of processing equipment is needed for commercialization of the processes. This study demonstrates that the pore size of frozen and thawed starch gels can be reduced by high-pressure freezing compared with freezing at atmospheric pressure. The reduced pore size was assumed to be a result of smaller ice crystals formed in the high-pressure freezing process. Based on this study, no conclusions can be drawn on the possibility of high-pressure freezing to improve the quality of real foods of a more complex composition and structure.     

Effect of high voltage electrostatic field treatment on thawing characteristics and post-thawing quality of frozen pork tenderloin meat

The thawing characteristics and post-thawing quality of frozen pork treated with high voltage electrostatic fields (HVEF) were compared with those of an air-thawed control. A multiple points-to-plate electrode operating at voltages above 6 kV significantly shortened the thawing time. Under electrode voltages 4, 6, 8, and 10 kV, thawing times were 70, 52, 46, and 40 min respectively, versus 64 min in the control. HVEF treatment was particularly effective in the temperature range −5–0 °C. HVEF treatment reduced the total microbial counts in thawed frozen meat by 0.5–1 log CFU/g, without affecting meat quality. During five days of post-thawing storage, the volatile basic nitrogen (VBN) levels increased from 10.64 to 16.38 mg/100 g under 10 kV applied voltage, while the control VBNs increased from 10.66 to 19.87 mg/100 g. This suggests an application potential for HVEF treatment in the thawing and storage of frozen meat.     

Effects of freezing on cell structure of fresh cellular food materials: A review

BackgroundFresh cellular food materials including fruits and vegetables and animal tissues normally consist of fine organized cellular structures. Freezing is a common method to preserve the quality and safety of these cellular foods. However, the formation of ice crystals during food freezing may cause damage to the food microstructure, leading to the deterioration of food quality after thawing.Scope and approachThis review offers current knowledge on freezing damage to cell structure of fresh cellular food materials. Effects of cell structure and water distribution on the texture and sensory properties of fresh cellular foods are presented. Mechanisms of cell structure damages caused by freezing are discussed. Novel methods to control the formation of ice crystals and preserve cell structures are also provided.Key findings and conclusionsThe quality of cellular foods after frozen-thawed is highly correlated with the integrity and viability of tissue cells. The formation of ice crystals, water migration and the inherent characteristics of cell structure are regarded as the main factors affecting the cell structure during freezing. For obtaining better quality of frozen products, further investigation and understanding on freezing damage to cell structure of fresh cellular foods is necessary. It is hoped that the current review will provide more information on improving frozen food quality for the frozen food industry.     

Opportunities and challenges in high pressure processing of foods

Consumers increasingly demand convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives. This demand has triggered the need for the development of a number of nonthermal approaches to food processing, of which high-pressure technology has proven to be very valuable. A number of recent publications have demonstrated novel and diverse uses of this technology. Its novel features, which include destruction of microorganisms at room temperature or lower, have made the technology commercially attractive. Enzymes and even spore forming bacteria can be inactivated by the application of pressure-thermal combinations, This review aims to identify the opportunities and challenges associated with this technology. In addition to discussing the effects of high pressure on food components, this review covers the combined effects of high pressure processing with: gamma irradiation, alternating current, ultrasound, and carbon dioxide or anti-microbial treatment. Further, the applications of this technology in various sectors - fruits and vegetables, dairy, and meat processing - have been dealt with extensively. The integration of high-pressure with other matured processing operations such as blanching, dehydration, osmotic dehydration, rehydration, frying, freezing / thawing and solid-liquid extraction has been shown to open up new processing options. The key challenges identified include: heat transfer problems and resulting non-uniformity in processing, obtaining reliable and reproducible data for process validation, lack of detailed knowledge about the interaction between high pressure, and a number of food constituents, packaging and statutory issues.     

Icy affairs: Understanding recent advancements in the freezing and frozen storage of fish

Freezing methods have evolved over the last 30 years. This review states the effect of various freezing methods on the quality of fish and seafood. Freezing temperatures, freezing, and frozen storage temperatures were also analyzed and reviewed. The changes in the ice crystal, protein, and lipid affect the fish quality and nutritional value during freezing and frozen storage. Freezing methods when combined with various additives or preprocessing approaches help improve the efficacy of freezing and frozen storage. Several experimental or emerging methods also have positive effects on the products' quality. According to the metadata reanalysis of quality markers, freshly frozen fish using different freezing methods may vary much in terms of ice diameter, but not others. High pressure freezing or immersion freezing-derived fish retains the best quality through frozen storage. More data are required on freezing methods (electrical-assisted freezing, microwave-assisted freezing, magnetic-assisted freezing, radiofrequency-assisted freezing, and the commercial's application and investment should be considered in the future. This review sheds light on finding a balanced initial shear force during freezing and the use of certain additives to control freezing-related damages. Focusing on ice diameter alone may be futile (e.g., liquid N₂ freezing). Future optimization of technologies should be in a way that several processes along the farm to fork such as freezing, frozen storage, thawing, thermal processing of fish, and even refabrication of food should mutually complement each other's needs to deliver safe and high-quality fish to the consumer's plate, even after a prolonged shelf-life.