冰晶生长对冷冻水产品品质影响及新型冷冻方式研究进展

冷冻技术在水产品保鲜方面应用广泛,但水产品在冻结过程中受冰晶形成、晶体生长与冰晶重结晶的影响,易造成细胞结构的破损,导致水产品品质下降。为深入分析冰晶生长与水产品品质变化间的关系,该文总结了冰晶生长对水产品的蛋白质变性、脂肪氧化、持水力、质构及感官特性影响,综述了物理场辅助冻结及添加抗冻剂、重结晶抑制剂等减小冰晶尺寸的新方法,为控制冰晶生长及提高冷冻水产品品质提供了理论参考     

糖类食品抗冻剂研究进展

冷冻储藏延长了食品的货架期,也会降低冻藏食品的品质。食品在冷冻过程中的不良反应和品质劣变主要包括冰晶生长、汁液流失、脂肪和蛋白质氧化、蛋白质变性等。添加抗冻剂是延缓冷冻食品劣变、保持食品品质的有效手段。糖类因其良好的抗冻效果,在冷冻食品中广泛作为抗冻剂应用。糖类添加剂在食品中的作用主要有保水、增稠、增筋、乳化和抗氧化等。近年来,新的抗冻糖类不断涌现,对糖类物质抗冻机理的研究也不断深入。该文对这些新发现、新理论进行总结,旨在为抗冻糖类的研究应用提供参考     

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。     

影响肉类食品冷冻质量的因素

冷冻肉类食品在不同的冷冻条件下会有不同的品质变化。食品的冻结温度,冻结曲线,最大冰晶生成带速度,及冷冻中的玻璃化转变及转变温度,都对食品组织结构,对蛋白质的冻结变性,对食品的外观,风味,营养等都构成了直接的影响。     

几种冷冻新技术对食品冻结过程中冰晶形成的影响

冷冻技术在现代食品加工工业中起着十分重要的作用,水结晶是冷冻过程的关键步骤。文章介绍几种冷冻新技术对食品冻结过程中水结晶的影响的研究进展,包括高压冷冻、超声波冷冻、渗透脱水冷冻、抗冻蛋白、冰核活性蛋白以及其它冷冻新技术。并阐述这些新技术对冰晶的影响机制,旨在能够更好地了解、预测及控制水结晶的过程,并进一步改进冷冻过程和提高冷冻食品的品质。     

数值模拟多冰晶的生长形貌

为研究食品速冻保鲜过程中多冰晶的微观生长特性,基于KOBAYASHI模型,采用单相场方程同时控制多个冰晶的生长,模拟了多冰晶晶核随时间步长和各向异性强度增加时的形貌变化。结果表明：随着模拟冷冻时间步长的增加,各冰晶的生长形貌逐渐变大,相邻冰晶由自由生长逐渐变为竞向生长,生长速率受到了抑制,冰晶形貌不再具有典型的六重对称性;在其他模拟参数不变的情况下,随着各向异性强度的增加,冰晶的大小及主枝相貌均变大,各冰晶间的相互影响逐渐增强。在食品的速冻保鲜过程中,防止大冰晶破坏细胞壁降低食品品质,应合理地控制冷冻时间和各向异性强度。     

抗冻蛋白与冰-水界面层相互作用的理论机制研究进展

抗冻蛋白（antifreeze proteins,AFPs）具有热滞活性和重结晶抑制活性,在冷冻食品品质调控、细菌低温保护、植物霜冻保护等领域具有广泛的应用价值。本文围绕种类和结构复杂的AFPs在低温冷冻环境下如何通过调控冰-水界面层结构、与冰晶结合或相互作用从而实现其抑制冰晶生长、产生热滞活性和重结晶抑制活性的理论问题,系统综述了吸附-抑制模型、偶极子-偶极子模型、晶格匹配与占有模型、刚体能量模型、包合物锚定模型、亲和相互作用偶联团聚模型等理论模型原理和特点,揭示了AFPs通过调控冰-水界面层结构产生结合或相互作用的原理及其驱动力作用特点,为解析AFPs抗冻活性机理及其筛选、食品工业应用提供理论参考。     

冷冻与解冻对肉类品质影响的研究进展

研究了冻结和解冻对肉类品质的综合影响。肉类在冻结过程中,易形成冰晶破坏其肌纤维结构,同时肉中可溶性蛋白等溶质浓度提高,继而导致一系列生化反应,最终使肉类品质下降,适口度和商业价值降低。在此过程中,肉类持水性降低、蛋白质变性、脂肪氧化,同时色泽、嫩度和菌落总数等方面都发生较大变化。同时,还介绍了改善冷冻肉品质的一些新技术。     

提高冷冻水产品品质的新型速冻技术研究进展

水产品因营养价值高,风味口感好,受到人们广泛的喜爱。然而水产品易腐败变质,需要采取一定的措施进行保藏。冷冻保藏技术是水产品最常用的保藏技术,传统的冷冻技术常因冷冻速度慢,形成大的冰晶而导致食品品质下降。近年来,研究者发现一些新兴的速冻技术可以抑制冷冻食品的品质下降。该文对水产品保藏技术中的一些新兴冷冻技术（磁场冷冻技术、电场冷冻技术、超声冷冻技术、高压冷冻技术）的原理,及其在水产品冷冻保藏中的应用进行综述,为人们了解水产品冷冻新技术提供参考。     

冷冻解冻对生鲜肉品质的影响及其新技术研究进展

冷冻是生鲜肉类贮藏和运输过程中常用的保鲜手段,但冷冻、解冻及反复冻融会加速肉中的脂质氧化及蛋白质氧化等,进而对肉品的色泽、嫩度、保水性等品质造成影响。本文分析了冷冻解冻及反复冻融对生鲜肉品质的影响,探讨了其影响机制,并对国内外冷冻解冻的新兴技术进行了总结,以期对我国肉类产业的冷冻解冻技术提供指导,并为冷冻产品品质控制及新型冷冻、解冻技术的开发提供理论参考和研究方向。     

Freezing of meat and aquatic food: Underlying mechanisms and implications on protein oxidation

Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice–water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.     

冻结方式对凡纳滨对虾贮藏中组织冰晶及品质的影响

新鲜凡纳滨对虾采用液氮、平板及冰柜冻结结合-20 ℃贮藏,研究不同贮藏时间内其组织冰晶形态与品质变化,以评价出最优的冻结方式。结果显示,随着贮藏时间的延长,平板及冰箱冻结的盐溶性蛋白含量、持水性、感官评分显著降低(p<0.05);而液氮冻结形成的冰晶直径比平板速冻小1/3,比冰箱小1/2;冻结后贮藏180 d其挥发性盐基氮(TVB-N值)≤25 mg/100 g,硫代巴比妥酸值(TBA)仅为0.72 mg/100 g,有效抑制了虾肉肌原纤维蛋白变性及脂肪氧化,能较好维持肌肉组织形态和品质,从而使虾肉的货架期延长至180 d以上。     

Size and location of ice crystals in pork frozen by high-pressure-assisted freezing as compared to classical methods

In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to - 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared to those obtained by air-blast and liquid N(2). Samples from the surface and centre of the frozen muscle were histologically analysed using an indirect technique (isothermal-freeze fixation). Air-blast and cryogenic fluid freezing, having thermal gradients, showed non-uniform ice crystal distributions. High-pressure-assisted frozen samples, both at the surface and at the central zones, showed similar, small-sized ice crystals. This technique is particularly useful for freezing large pieces of food when uniform ice crystal sizes are required.     

冻藏及解冻过程对水产品品质的影响

水产品中含有丰富蛋白质、脂肪酸、水分等,具有很高的营养价值。随着人类生活水平的提高,对高品质水产品的需求也越来越高。本文综述了水产品冷冻贮藏及解冻方式的原理及其特点,比较不同解冻方式的优劣势;并具体从营养成分指标,微生物指标以及感官指标等方面具体分析了冻藏及解冻过程对水产品品质的影响。其中营养成分指标包括蛋白质变性二级结构的变化、脂肪氧化产生挥发性物质、冰晶对肌肉细胞造成机械损伤等,微生物指标包括水产品中常见的细菌菌落的控制,感官指标包括水产品色泽方面氧合肌红蛋白的变化,质构方面包括剪切力、粘度、硬度等。本文详细总结了冻藏解冻过程中相关指标的变化和影响,旨在为未来冻藏及解冻技术及工艺的研发提供依据。     

Effect of freezing temperature on the color of frozen salmon

New freezing methods developed with the purpose of improved product quality after thawing can sometimes be difficult to get accepted in the market. The reason for this is the formation of ice crystals that can give the product a temporary color loss and make it less appealing. We have here used microscopy to study ice crystal size as a function of freezing temperature by investigating the voids in the cell tissue left by the ice crystals. We have also investigated how freezing temperature affects the color and the visible absorption spectra of frozen salmon. Freezing temperatures previously determined to be the best for quality after thawing (-40 to -60 °C) were found to cause a substantial loss in perceived color intensity during frozen state. This illustrated the conflict between optimal freezing temperatures with respect to quality after thawing against visual appearance during frozen state. Low freezing temperatures gave many small ice crystals, increased light scattering and an increased absorption level for all wavelengths in the visible region. Increased astaxanthin concentration on the other hand would give higher absorption at 490 nm. The results showed a clear potential of using visible interactance spectroscopy to differentiate between poor product coloration due to lack of pigmentation and temporary color loss due to light scattering by ice crystal. This type of measurements could be a useful tool in the development of new freezing methods and to monitor ice crystal growth during frozen storage. It could also potentially be used by the industry to prove good product quality. PRACTICAL APPLICATION: In this article we have shown that freezing food products at intermediate to low temperatures (-40 to -80 °C) can result in paler color during frozen state, which could affect consumer acceptance. We have also presented a spectroscopic method that can separate between poor product color and temporary color loss due to freezing.     

蓄冷材料对风冷冰箱中猪肉品质的影响

通过在风冷冰箱冷冻室中配置蓄冷材料,分别测定了实验组（添加蓄冷材料）和对照组（未添加蓄冷材料）冷冻室中温度的变化和冷冻肉块的干耗率、解冻汁液流失率、色差、质构、剪切力、微观结构、孔隙率等指标,分析了蓄冷材料对冷冻肉品质的影响。结果显示,相比对照组,实验组风冷冰箱冷冻室内温度波动明显减小（±0.36 ℃）,通过最大冰晶生长带的时间缩短61 min,冻存肉块的干耗率、解冻汁液流失率明显减小,咀嚼性更优;肌间冰晶重结晶减弱,冰晶分布均匀,对肉块内部的机械损伤减弱,肌纤维的完整性得以更好的保持。结果证明,蓄冷材料对维持冷冻肉的品质具有可行性,为更好地优化风冷冰箱性能提供了依据。     

Freezing rate simulation as an aid to reducing crystallization damage in foods

In food freezing processes the presence of large ice crystals is a serious drawback when a good final quality of the product is desired. To study the size and distribution of those crystals, a large piece of pork muscle has been frozen by liquid nitrogen evaporation. A mathematical model to simulate different cooling rates at the surface of the product was solved using a finite element method; this model satisfactorily fitted experimental data and predicted local freezing rates at different locations in the meat tissue. The model was applied to find the freezing rates that led to a good quality product, related to an optimum distribution of small ice crystals located inside and outside the tissue fibres.     

Ice morphology in frozen beef

A histological study was made of pieces of meat which had been frozen from one side, in conditions where the direction of the heat flux was approximately unidirectional and perpendicular to the muscle fibres. The morphology of the ice crystals in tissue frozen under various conditions was studied, and the range of freezing velocities over which no intracellular ice existed, was established. The average diameter D , of ice crystals, measured in different experiments and at different levels in the same piece of meat was related to the characteristic freezing time t _c, by the equation:
D = a + b log t _c     

水产品中冰晶重结晶机理及控制方法的研究进展

冷冻处理已被广泛用于延长水产品的货架期,但是冰晶重结晶会不可避免地降低水产品品质。冰晶重结晶会影响冰晶尺寸和分布,加剧水分流失、蛋白质和脂质氧化、颜色变化和质构劣变。为了深入阐述水产品中冰晶重结晶的机理,本文首先总结了驱动冰晶重结晶的积聚、迁移和表面等渗的机制,介绍了冰晶重结晶对水产品品质的影响及其变化原因,分析了抑制冰晶重结晶的措施及其机制,包括添加糖类、抗冻蛋白、抗冻肽和具有冰重结晶抑制活性的聚合物,并对其在冷冻水产品中应用前景进行了展望,以期为优化冷冻水产品品质提供理论依据。