肉类嫩化技术研究进展

近年来,肉类嫩化技术一直是肉品学科中的热点之一。了解肉的嫩化机理可以更好地加速肉嫩化的过程。本文主要对肉类产品宰后嫩化技术的种类及影响肉类嫩度的因素进行了综述。     

肉类嫩化的理论、方法及前景

近十多年来,肉类嫩化理论及加工工艺研究一直是肉品学科中的热点之一。了解肉的嫩化机理可以更好地加速肉嫩化的过程。嫩化技术为宰后嫩化技术和宰前嫩化技术。牲畜宰前肉的嫩化如适龄牲畜在出栏前,日粮中适当加入VD3、VE,或使牲畜适当运动。综述了电刺激、钙处理、外源酶处理、机械嫩化、pH处理、高压处理、冲击波处理等影响肉类嫩度与品质的因素及嫩化的技术理论和方法。     

宰后僵直温度对肉嫩度的影响

肉的嫩度差和不一致性是肉类屠宰加工工业面临的两大难题。宰后24 h内的胴体/肌肉的温度决定肉嫩度的水平。研究论述了宰后僵直温度对肌肉收缩与成熟过程内源蛋白酶的影响,探讨了宰后温度对肉嫩度影响的机制,进而讨论了p H-温度窗口,以期为屠宰加工企业优化胴体冷却温度提供参考。     

嫩肉粉对猪肉、牛肉的水解消化作用

测定了嫩肉粉在对猪肉、牛肉消化过程中，温度，ＰＨ值、用量、时间等因素对肉类水解消化率的影响，并探讨了嫩肉粉对肉类的嫩化机理。     

牛肉嫩化技术的研究进展

肉品嫩度是肉的首要食用品质,它是消费者评判肉质优劣的最常用指标。肉嫩度的改善,多年来一直是国内外肉品科学研究的热点之一。宰后肉类的后期成熟和嫩化处理,是改善肉品嫩度的关键环节。对影响肉嫩度的宰前和宰后因素、目前嫩化方法及嫩化机制进行综述,最后对肉的嫩化趋势作出展望。     

宰后肉的嫩化机制及其影响因素

宰后肉类的后期成熟和嫩化处理,是改善肉品质（嫩度）的关键环节。本实验阐述了影响宰后肉嫩度的因素（pH值、胶原蛋白和钙激活酶）和相关嫩化机理（有机酸、电刺激、盐类、外源酶和内源酶、超声波、高压和吊挂拉伸的嫩化机理）。     

畜禽宰后肌肉嫩化相关酶研究进展

目前普遍认为参与宰后肌肉嫩化的相关蛋白酶主要有溶酶体组织蛋白酶、蛋白酶体、钙激活蛋白酶、钙激活酶抑制蛋白和半胱天冬酶5 种,然而对于成熟过程中肉的嫩化程度及机理颇具有争议。大量的研究表明,上述5 种嫩化酶在参与肉嫩化过程中其自身生理生化特性在宰后也发生变化。本文综述5 种参与宰后肉嫩化酶的分子质量、存在部位、作用底物、作用位点、激活条件、最适pH值以及对其活性具有一定影响的抑制剂,并就其影响宰后肉嫩度的作用机理及其自身状态的变化进行分析与阐述,旨在为后续研究嫩化酶在宰后改善肉嫩度方面的应用条件提供参考。     

Bcl-2蛋白介导Caspases级联反应对牛肉嫩化的作用机制

为探讨宰后成熟过程中牛肉嫩化是否依赖抗凋亡蛋白(Bcl-2),不同部位牛肉嫩度是否存在显著差异,本文通过测定在牛肉宰后成熟过程中,Bcl-2、促凋亡蛋白(Bax)和细胞凋亡酶表达量等指标,并分析其与牛肉剪切力值的关系,最终确定Bcl-2和Bax相对含量对牛肉嫩化的作用机制。在宰后2~12 h,前躯肱三头肌(TB)、中躯背最长肌(ML)和后躯半膜肌(SM)的Bax/Bcl-2相对含量以及细胞凋亡酶(Caspase-3、Caspase-8、Caspase-9)活力均显著上升(p<0.05),宰后6~48 h,剪切力下降极显著(p<0.01)。研究表明,牛肉宰后嫩化依赖于线粒体途径和死亡受体途径,Bcl-2蛋白通过介导Caspases级联反应对牛肉嫩度进行调控。Bax/Bcl-2相对含量的升高导致Cyt-C从线粒体释放到细胞质,启动Caspase级联反应,激活Caspase-3,水解肌原纤维蛋白引发细胞凋亡,最终导致在宰后48 h内牛肉嫩度不断提高,且ML嫩度优于TB和SM。     

宰前及宰后处理改良畜禽肉品质的研究进展

肉品质是人们对肉类多种质量特性的综合评价。畜禽肉品质的改良是一项复杂的系统工程,必须从多方面全盘考虑。宰前及宰后处理是生产中改良肉品质的重要途径。畜禽在宰前进行短期特殊饲养并改善驱赶、转运和运输的方法,可以大幅度降低宰前动物的应激反应,提高肉的品质;宰后电刺激胴体、注射品质改良剂、合理冷却降温、适当的成熟过程以及特殊嫩化处理等多种技术也能使肉品质得到有效的改善。     

肌内结缔组织与肉嫩度的关联机制及相关肉嫩化技术的研究进展

肌内结缔组织（intramuscular connective tissue,IMCT）是肌肉组织的重要组成部分,对肉的质地和品质具有重要作用,特别是在宰后成熟、烹饪过程中其结构组分会发生变化,在很大程度上影响了肉的嫩度,其中肌束膜和肌内膜中胶原蛋白的变化起关键作用。本文从IMCT中胶原蛋白的特性入手,综述了IMCT与肉嫩度的相关性,分析了IMCT在肉的宰后成熟、烹饪过程中的变化,总结了新兴的肉类嫩化技术（电刺激、外源酶解、脉冲电场、超声波等）对IMCT的影响及与之相关的肉嫩度变化情况,为合理调控IMCT从而有效提升肉的嫩度提供技术支持和理论依据。     

肉类嫩化研究现状与发展趋势

肉的嫩度严重影响肉的消费,使肉嫩化的研究很有必要。本文主要综述了肉类嫩化的机理、影响肉嫩度的因素和肉嫩化的方法。同时还简单提及了肉类嫩化的发展趋势。     

肉的嫩化与番木瓜蛋白酶

本文主要介绍了番木瓜蛋白酶在肉类嫩化中的应用方法.     

Physical Interventions to Manipulate Texture and Tenderness of Fresh Meat: A Review

Meat tenderness is a major eating quality attribute that ensures consumer satisfaction and repeat purchase of red meat. The variability in meat tenderness is related to several factors that are spread across the production chain (biological, on farm, processing, and consumer factors), which can lead to inconsistent tenderness in fresh red meat products. The tenderization process is dictated by physical and biochemical factors, which appear to affect the proteases involved in protein degradation and, consequently, they regulate the rate and extend of tenderization in meat. Several physical, chemical, and biochemical interventions have been investigated to improve the tenderness of meat. The present review discusses the physical interventions used to manipulate the texture of meat and their mechanism of action, optimal tenderizing conditions, and their effects on other meat quality attributes (colour stability, lipid oxidation, and water holding capacity). Attention should be paid to other quality attributes for full evaluation of the differing interventions.     

Prospects for new technology of meat processing in Japan

This review starts by introducing the history and underlying culture of meat production and consumption in Japan since early times, and the effects of social change on these parameters. Meat processing in Japan is described, and certain other related papers are also introduced. Automatic machines for meat cutting have been developed by the Japanese food industry and are currently being used throughout the world, particularly in Europe. Soft meat products specially produced for the elderly, along with diet meat products low in salt and calorie content for middle aged persons have recently gone into production. The intensification of color formation of meat using naturally occurring materials, and tenderization of sausage casing are discussed.     

Exogenous Proteases for Meat Tenderization

The use of exogenous proteases to improve meat tenderness has attracted much interest recently, with a view to consistent production of tender meat and added value to lower grade meat cuts. This review discusses the sources, characteristics, and use of exogenous proteases in meat tenderization to highlight the specificity of the proteases toward meat proteins and their impact on meat quality. Plant enzymes (such as papain, bromelain, and ficin) have been extensively investigated as meat tenderizers. New plant proteases (actinidin and zingibain) and microbial enzyme preparations have been of recent interest due to controlled meat tenderization and other advantages. Successful use of these enzymes in fresh meat requires their enzymatic kinetics and characteristics to be determined, together with an understanding of the impact of the surrounding environmental conditions of the meat (pH, temperature) on enzyme function. This enables the optimal conditions for tenderizing fresh meat to be established, and the elimination or reduction of any negative impacts on other quality attributes.

[Supplementary materials are available for this article. Go to the publisher's online edition of Critical Reviews in Food Science and Nutrition for the following free supplemental files: Additional text, tables, and figures.]     

Contribution of postmortem muscle biochemistry to the delivery of consistent meat quality with particular focus on the calpain system

Tenderness has been repeatedly reported as the most important quality aspect of meat. However, a number of studies have shown that a significant portion of retail meat can be considered tough. As a consequence, a significant consumer segment is willing to pay a premium for guaranteed tender meat. However, apart from measuring the shear force, there is no reliable method to predict tenderness. Most of the branded meat programs therefore attempt to ensure eating quality by controlling some of the factors that affect tenderness. Meat tenderness is determined by the amount and solubility of connective tissue, sarcomere shortening during rigor development, and postmortem proteolysis of myofibrillar and myofibrillar-associated proteins. Given the effect of postmortem proteolysis on the muscle ultrastructure, titin and desmin are likely key substrates that determine meat tenderness. A large number of studies have shown that the calpain proteolytic system plays a central role in postmortem proteolysis and tenderization. In skeletal muscle, the calpain system consists of at least three proteases, μ-calpain, m-calpain and calpain 3, and an inhibitor of μ- and m-calpain, calpastatin. When activated by calcium, the calpains not only degrade subtrates, but also autolyze, leading to loss of activity. m-Calpain does not autolyze in postmortem muscle and is therefore not involved in postmortem tenderization. Results from a number of studies, including a study on calpain 3 knockout mice, have shown that calpain 3 is also not involved in postmortem proteolysis. However, a large number of studies, including a study on μ-calpain knockout mice, have shown that μ-calpain is largely, if not solely, responsible for postmortem tenderization. Research efforts in this area should, therefore, focus on elucidation of regulation of μ-calpain activity in postmortem muscle. Discovering the mechanisms of μ-calpain activity regulation and methods to promote μ-calpain activity should have a dramatic effect on the ability of researchers to develop reliable methods to predict meat tenderness and on the meat industry to produce a consistently tender product.     

Tenderization effect of cold-adapted collagenolytic protease MCP-01 on beef meat at low temperature and its mechanism

The enzymes currently used to increase meat tenderness are all mesophilic or thermophilic proteases. This study provides insight into the tenderization effect and the mechanism of a cold-adapted collagenolytic enzyme MCP-01 on beef meat at low temperatures. MCP-01 (10 U of caseinolytic activity) reduced the meat shear force by 23% and increased the relative myofibrillar fragmentation index of the meat by 91.7% at 4 °C, and it also kept the fresh colour and moisture of the meat. Compared to the commercially used tenderizers papain and bromelain, MCP-01 showed a unique tenderization mechanism. MCP-01 had a strong selectivity for degrading collagen at 4 °C, showed a distinct digestion pattern on the myofibrillar proteins, and had a different disruption pattern on the muscle fibres under scanning electron micrograph. These results suggest that the cold-adapted collagenolytic protease MCP-01 may be promising for use as a meat tenderizer at low and moderate temperatures.     

Characterisation of kiwifruit and asparagus enzyme extracts,and their activities toward meat proteins

Two plant enzyme extracts from kiwifruit and asparagus were evaluated for their ability to hydrolyse commercially available substrates and proteins present in both beef connective tissue and topside myofibrillar extracts. The results show significant differences in protease activity depending on the assay used. Protease assays with connective tissue and meat myofibrillar extracts provide a more realistic evaluation of the potential of the enzymes for application in meat tenderization. Overall, the kiwifruit protease extract was found to be more effective at hydrolysing myofibrillar and collagen proteins than the asparagus protease extract. The two protease extracts appeared to target meat myofibrillar and collagen proteins differently, suggesting the potential of a synergistic effect of these proteases in improving the tenderness of specific cuts of meat, based on their intrinsic protein composition.     

超声波技术嫩化机理及其在肉制品中应用效果的研究进展

嫩度是评估肉制品品质的重要指标,提高嫩度有利于吸引消费者二次购买.传统物理嫩化技术虽广泛应用于肉及肉制品的嫩化加工,但在线应用差这一缺陷导致消费者接受度较低,因此推进了新兴物理嫩化技术的研究.其中,超声波作为一种高效节能、绿色环保、穿透力强的非热加工技术广泛用于肉制品的嫩化.本文综述了肉制品嫩化理论、嫩度主要影响因素以...     

Calpain and cathepsin activities in post mortem fish and meat muscles

Post mortem tenderization is one of the most unfavourable quality changes in fish muscle and this contrasts with muscle of mammalian meats. The tenderization can be partly attributed to the acid lysosomal cathepsins and cytosolic neutral calcium-activated calpains. In this study, these proteases from fish and bovine muscles were quantified and compared. The cathepsin B and L activities were in more important amounts in sea bass white muscle than in bovine muscle. On the other hand, cathepsin D activity was 1.4 times higher in meat that in fish muscle, while cathepsin H was negligible in both muscles. Calpain activities were similar in both types of muscle. Moreover, calpastatin (calpain endogenous inhibitor) level is 3.9 times higher in sea bass white muscle. These differential activities are considered in relation to their probable involvement in post mortem degradation of muscle.