美国研究成熟-冷冻顺序对牛肉微观结构、蛋白质降解和物化性质的影响

<正>冷冻处理是目前肉制品工业为延长肉保质期最为常用的手段,但是不恰当的冷冻保藏会使产品的品质受损,从而使冷冻保藏的效果大打折扣。冷冻对肉品的负面影响包括汁液损失增加、氧化稳定性降低、褪色和变黑等,这些变化归因于冷冻过程中因渗透压变化而析出冰晶的影响,冰晶析出和融解会导致机械结构破坏、肌肉结构松弛和随之发生的蛋白质降解和氧化。为分析成熟和冷冻顺序对牛肉微观结构、氧化稳定     

水-冰-水动态变化引起冷冻肉类食品品质变化机理及控制技术研究进展

低温冷冻是最古老、应用最广泛和最经济有效的肉类食品保鲜方法,但肉类食品经过冻结、冻藏和解冻后,其中80%的水分经历水-冰-水两次相变,冰晶的形成以及后续冰晶的融化会破坏肌细胞结构,使肌肉主要成分如蛋白质和脂肪发生氧化,导致冷冻肉类食品保水性降低、颜色变暗、组织软塌和营养价值减少或丧失。因此,本文拟从水-冰-水动态变化角度概述冰晶的形成和生长过程（冰晶的成核、生长和重结晶）;分析不同温度和过饱和度下冰晶的形态、冻融引起肌肉中发生水-冰-水动态变化的过程;重点综述水-冰-水动态变化迫使冷冻肉微观结构、保水性、氧化稳定性（脂肪氧化、蛋白质氧化和构象改变）以及感官品质（质构、色泽和风味）发生劣变的机理;简述目前一些提升冷冻肉类食品品质的新兴冷冻技术（超声波技术、高压技术、电磁场技术以及添加抗冻剂）,为提高冷冻肉类食品品质及工业化生产提供科学理论依据。     

美国和韩国联合研究成熟-冷冻组合和冷冻速率对猪里脊品质和氧化稳定性的影响

正一般认为冻融产品的品质差于未经冷冻的新鲜产品。冻融肉制品主要的质量损害包括冻融过程中水分的过度损失、蛋白质和脂肪氧化加剧、褪色和质构的潜在变化。研究表明,在冻融前进行成熟,生产出的产品具有更高的品质。为分析成熟-冷冻和冷冻速率对冻融猪里脊品质和氧化稳定性的影响,美国和韩国科学家进行相关研究。     

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。     

简述冷冻及缓化对原料肉品质影响的研究进展

阐述了冻融对原料肉品质参数的影响,原料肉在冷冻过程中冰晶的形成,破坏了原料肉中肌细胞结构,导致细胞液析出。细胞液中成分发生一系列的生化反应,从而改变肌细胞结构,影响原料肉的品质。主要包括:水分损失、蛋白质变性、脂质和蛋白质氧化、颜色、pH值、剪切力以及微生物变化的结果。通过此次研究进展的综述,为原料肉品质的改善提供一定的理论依据。     

中国研究超声辅助浸冻对猪最长肌微观结构、品质和水分分布的影响

<正>冷冻能够降低微生物生长速率、降低酶活性、保持产品原有的营养价值和使用特性,是目前进行肉及肉制品长期贮藏最有效的手段之一。但是,冷冻过程中仍会发生蛋白质降解、脂肪氧化等不良反应,使得肉制品食用品质下降,尤其是暴露于空气中的产品。冷冻速率、冷冻方式和贮藏温度等贮藏条件均会对冷冻肉制品的品质产生影响。为分析超声辅助浸冻对猪最长肌微观结构、品质和水分分布     

解冻方法对原料肉品质及蛋白质结构影响的研究进展

解冻是将原料肉中形成的冰晶融化为水并恢复其冷冻前状态的过程。解冻对肉类持水力、色泽、嫩度及质构特性等品质方面产生影响,而品质变化是肌肉蛋白质结构变化的外在表现。本文简述了肉制品加工过程中常用解冻方法的优缺点,通过分析解冻过程中蛋白质结构变化解释解冻方法引起肉类品质变化的机理,为正确选择解冻方法和提高原料肉品质提供理论支持。     

肉和肉制品中脂质氧化的研究进展

肉和肉制品在加工、贮藏和运输的过程中容易发生脂质氧化,影响肉制品的品质。脂质适度氧化可以促进肉制品的风味,但是脂质过度氧化还可能产生有毒有害物质,增加食用风险。脂质氧化反应产生的初级产物及次级产物化学性质不稳定,容易与肉中的其他成分(蛋白质、血红素、抗氧化添加剂等)发生反应从而影响肉制品的品质。因此,调控脂质氧化对肉及肉制品来说非常重要。本文主要综述了脂质的酶促氧化、自动氧化、脂质氧化与蛋白质氧化之间的关系。大量研究表明,脂质氧化过程复杂且受诸多因素和条件的影响,研究氧化过程及氧化机制对调控脂质氧化和提高食品品质的稳定性具有重要意义。     

氧化引起肉及肉制品品质劣变的机理及影响因素

肉及肉制品在加工和贮藏过程中品质会下降,如嫩度降低、褪色、形成腐败味道等,而肉品质的降低与肉中含有的主要成分肌红蛋白、肌原纤维蛋白和脂肪的氧化有关,本文主要讨论三者氧化变化以及关联性,并探讨在加工贮藏过程中可能引起氧化的因素,为生产高质量的肉制品提供一定参考。     

超声波技术在肉及肉制品中的应用研究进展

超声波作为一种新型绿色食品加工技术,具有缩短加工时间、降低生产成本和改善肉及肉制品品质等优势,在肉及肉制品行业中的应用受到广泛关注。本文综述超声波技术对肉及肉制品理化特性（嫩度、持水性、色泽、氧化稳定性和pH值）的影响及其机理,此外,对超声波技术在腌制、冷冻和解冻、杀菌等肉制品加工工艺中的应用和影响机制进行总结,为其在肉及肉制品实际生产中的应用提供理论依据。     

水产品冻结贮藏中冰晶的形成及控制研究进展

冻结贮藏是目前水产品保藏的重要方式,最大程度地保留了水产品的新鲜程度。而冻结贮藏的过程中冰晶的生成会对水产品品质产生破坏,影响风味和质构。冻品再解冻又会导致大量汁液流失。本文对冰晶形成的机理进行探讨,分析影响冰晶生成的因素,并介绍目前控制水产品冰晶形成的一些方法。影响冰晶形成的因素有冻结速率、冻结温度、温度波动等,控制冰晶形成的方法有微冻、压力转移冻结等。     

Synergism effect of low voltage electrostatic field and antifreeze agents on enhancing the qualities of frozen beef steak: Perspectives on water migration and protein aggregation

In this study, a synergistic strategy utilizing low-voltage electrostatic field (LVEF) and antifreeze agents (4% sucrose +4% sorbitol) was proposed to reduce quality deterioration of prepared beef steak during freezing. The effects of the synergistic treatment on the water holding capacity, texture and muscle ultrastructure, myofibrillar protein (MP) aggregation was studied. Results showed that co-treatment significantly reduced thawing losses (about 41%) by preventing the migration of immobilized water to free water and reduced ice crystal size compared to air freezing (AF). In addition, co-treatment positively affected texture properties by shortening the gap between muscle fibers and maintaining the structural integrity of the sarcomeres. Moreover, synergistic treatment inhibited the unfolding of the MP structure and the formation of MP aggregates by strengthening non-covalent interactions. These results seem to demonstrate that LVEF can remarkably enhance the effects of cryoprotectants, which provides a new perspective on food cryoprotection.Industrial relevanceFreezing is the most common method of preserving prepared meat products, however, the formation of large ice crystals and the denaturation of muscle proteins are two major causes of quality deterioration during conventional air-freezing. In this study, a LVEF system was applied to the freezing process of prepared meat products, and a comparative and synergistic study was carried out with the current industry common chemical freezing protection methods (addition of antifreeze). The results showed that the synergistic treatment greatly promoted the nucleation of food products, shortened the phase transition time, reduced the ice crystal size and effectively reduced the thawing losses by approximately 41%. The green freezing system can be easily adapted to scenarios such as cold chain transport and cold storage. And the LVEF intensifies the interaction of antifreeze molecules with protein and water molecules, which seems to open up even more possibilities in cryopreservation.     

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     

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.     

Influence of the pressure shift freezing and thawing on the microstructure of largemouth bass

The objective of this study was to use a new self-cooling laboratory system for carrying out the pressure shift freezing (PSF) and evaluate the influence of PSF at 150 MPa on the microstructural properties of largemouth bass relative to liquid immersion freezing (LIF) and conventional air freezing (CAF). CAF, LIF and PSF showed average total freezing times of 176 ± 7.4, 65.3 ± 6.8 and 23.2 ± 3.1 min, and the cross sectional area of ice crystals in the muscle were 1002 ± 778, 501 ± 248 and 143 ± 50.6 μm², respectively, demonstrating a significant reduction in crystal size to be associated with PSF. It was observed that damage caused by the ice crystals during the freezing to the muscle microstructure was irreversible. The thawing and cooking losses of largemouth bass after the freezing were lower for PSF as compared to the other two freezing methods. PSF reduced the damage to myocytes and resulted in lower drip loss due to reduced microstructure disruption due to their small ice crystals, thereby maintaining the muscle tissue to better retain the fluids. Color and texture properties were less affected by PSF.Industrial relevanceFreezing is the most used preservation method for aquatic products. Rapid freezing results in better texture retention while the slow freezing damages the product texture because of the formation of extracellular large ice crystals developed during the freezing process. Thus, the nature of freezing affects the quality of frozen foods. Successful freezing processes aim at employing rapid freezing conditions which result in the formation of small ice crystals. Pressure shift freezing (PSF) is a novel technique with advantages of high degree of super-cooling, short phase transformation time, and results in very small ice crystals. This study makes use of a laboratory self-cooling system to carryout PSF of largemouth bass. This cooling system overcomes the limitation of previous studies on PSF which are expensive, limited to small size and impractical for commercial exploitations. The cooling system employed in this study can be easily adapted to large-scale production of PSF aquatic products. Test results provide a basis for the commercial exploitation of PSF for largemouth bass and such other aquatic foods for driving the quality advantage.     

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。     

Impact of freezing and thawing on the quality of meat: review

This comprehensive review describes the effects of freezing and thawing on the physical quality parameters of meat. The formation of ice crystals during freezing damages the ultrastructure and concentrates the solutes in the meat which, in turn, leads to alterations in the biochemical reactions that occur at the cellular level and influence the physical quality parameters of the meat. The quality parameters that were evaluated are moisture loss, protein denaturation, lipid and protein oxidation, colour, pH, shear force and microbial spoilage. Additionally mechanisms employed to mitigate the effects of freezing and thawing were also reviewed. These include the use of novel methods of freezing and thawing, ante and post mortem antifreeze protein inclusion and vitamin E supplementation, brine injection and modified atmospheric packaging.     

速冻食品中冰晶的研究进展

速冻技术可有效保持食品的新鲜度,但由速冻带来的"副产物"冰晶会对食品内、外部造成破坏,导致营养物质流失,外观口感变差。针对冰晶产生的机理,检测冰晶的方法,影响冰晶体形成的因素,控制冰晶体生成的方法以及将来发展方向等方面进行了论述。目的在于通过对冰晶的了解,改进现有方法,提高速冻食品的品质。