Stanley D W
Department of Food Science, University of Guelph, Ontario, Canada.
Crit Rev Food Sci Nutr. 1991;30(5):487-553. doi: 10.1080/10408399109527554.
Biological membranes are rarely considered by food scientists when the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yet, membranes and their deterioration play a major but underestimated role in food losses, and recent biochemical information indicates that at least some of these reactions can be controlled by procedures suited to food materials. Much of the present information available on membrane degradation in food systems is incomplete and speculative. It is known, however, that in order to accomplish their many indispensable functions in cells, membranes are constituted mainly of phospholipids, protein, and some carbohydrates arranged in thin, bimolecular sheet-like structures that serve to compartmentalize cells and their organelles. Membranes have embedded in their asymmetric surfaces complements of catalytic and cytoskeletal proteins that serve permeability and structural functions. Membrane surfaces exhibit fluidity, due partially to the continuous lateral diffusion of lipids and some proteins. Two important consequences of fluidity are the ability of membrane phospholipids to exist in different interconvertible conformational phase structures and the formation of heterogenous lipid domains on the membrane surface. Cellular death leads unavoidably to the initiation of membrane deterioration. While the time course of this series of reactions differs in animal and plant tissue, they are damaged by generally similar mechanisms. These include an initial peroxidative attack on polyunsaturated fatty acids, with the concomitant production of free radicals. Many biological agents can act as accelerating agents in these reactions, including transition metal ions, heme compounds, radiation, illuminated chlorophyll, calcium, and ethylene. Once formed, free radicals catalyze further reactions that can affect all aspects of membrane function and cellular metabolism, and lead ultimately to significant losses in food quality through defects such as chilling injury and cold shortening. These are aggravated by many food-processing steps, especially those that involve tissue disruption. Control of membrane breakdown by exogenous chemical intervention has been practiced, but, at best, this only slows the rate of these reactions. Newer approaches to this problem include dietary treatment of meat animals, modified storage and packaging conditions, and genetic interventions. This review advances the proposition that membrane deterioration can be considered a "universal mechanism" that leads to significant quality losses in food. Perhaps because the study of biological membranes and the biochemical and physiological properties has only begun recently, not much progress has been made in finding practical control mechanisms for these reactions in food systems.(ABSTRACT TRUNCATED AT 400 WORDS)
在研究食品组织加工或储存过程中发生的变质反应时，食品科学家很少考虑生物膜。然而，膜及其变质在食品损失中起着主要但被低估的作用，最近的生化信息表明，其中至少一些反应可以通过适合食品材料的程序来控制。目前关于食品系统中膜降解的许多现有信息是不完整且具有推测性的。然而，众所周知，为了在细胞中完成其许多不可或缺的功能，膜主要由磷脂、蛋白质和一些碳水化合物组成，它们排列成薄的双分子片状结构，用于分隔细胞及其细胞器。膜在其不对称表面嵌入了具有催化和细胞骨架功能的蛋白质，这些蛋白质具有通透性和结构功能。膜表面表现出流动性，部分原因是脂质和一些蛋白质的持续横向扩散。流动性的两个重要结果是膜磷脂能够以不同的可相互转化的构象相结构存在，以及在膜表面形成异质脂质域。细胞死亡不可避免地导致膜变质的开始。虽然这一系列反应的时间进程在动物和植物组织中有所不同，但它们受到的损伤机制通常相似。这些机制包括对多不饱和脂肪酸的初始过氧化攻击，同时产生自由基。许多生物因子可以在这些反应中充当促进剂，包括过渡金属离子、血红素化合物、辐射、光照叶绿素、钙和乙烯。一旦形成，自由基会催化进一步的反应，这些反应会影响膜功能和细胞代谢的各个方面，并最终通过诸如冷害和冷收缩等缺陷导致食品质量显著下降。许多食品加工步骤会加剧这些问题，尤其是那些涉及组织破坏的步骤。通过外源化学干预来控制膜的分解已经得到应用，但充其量只能减缓这些反应的速度。解决这个问题的新方法包括对肉用动物进行饮食处理、改变储存和包装条件以及基因干预。这篇综述提出了一个观点，即膜变质可以被视为导致食品质量显著损失的“普遍机制”。也许是因为对生物膜及其生化和生理特性的研究直到最近才开始，在寻找食品系统中这些反应的实际控制机制方面进展不大。（摘要截选至400字）
