Membrana biologica

Critical Reviews in Food Science and Nutrtition. 30(5):487-553 (1991)

Biological Membrane Deterioration and Associated Quality Losses in Food Tissues
D. W. StanJey
Department of Food Science, University of Guelph, Guelph, Ontario, Canada
Referee: Kirk L. Parkln, Dept. of Food Science, Unlversity of Wlsconsin,
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Madison, WI.

ABSTRACT: Biological membranes are rarely considered byfood scientists. whcn the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yel:íTIe'ñibranesand their deterioration . playa major but underestimated role in food losses, and recent biochemical information indicates that at least ~ some of these reactions can be controlled Qy procedures suíted to food máterials. Much of the present information~il~ble {ln membrane degradation in food systems is incomplete and _ ..,.-...-. . • ....,........J,'lo.,. speculative. It is known, 1:J!ny~, that in order to accomplish their many indispensable functions in cells, membranes are constituted IT¡ainlyof phospholipids, protein, and some carbohydrates arranged in thin, bimolecular sheet-like structures that serve to compartmentalize cells and theirorganelles. 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 ex'ist in different interconvertibleconformational 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 inelude an initial peroxidative attack on polyunsaturated fatty acids, withthe concomitant production of free radicals. Many biological agents can act as accelerating agents in these reactions, ineluding transition metal ions, heme compounds, radiation, illuminated chlorophyll, calcium, and ethylene. Once formed, free radical s catalyze further reactions that can affect all aspects of membrane function and cellular metabolism, and lead ultimately to significant losses infood 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 inelude dietary treatment of meat animals,modified storage and packaging conditions, and genetic interventions. This review advances the proposition that membr~llf;,de~erioration can be considered a "universal mechanism" that leads to significant quality losses in food. Perháp8"Ybecausethe study of biological membranes and the biochemical and physiological properties has only begun recently, not much progress has been made in finding practicalcontrol mechanisms for these reactions in food systems. However, as more basic work is done, it would seem obligatory for food scientists to find application for these principies in food systems.

KEY WORDS: biological membranes, membrane degradation, fluidity, food quality, free radicals, control mechanisms.

1. INTRODUCTION Initially, the most obvious feature about biological membranes to afood scientist is their negligible contribution to the total quality of edi-

ble tissue. Membranes are thought to be insignificant to the nutritional value of food; are difficult to visualize, even using electron optics; and, thus, are rarely investigated by food researchers or considered in food science courses.

1040-8398/91/$.50 © 1991 by CRC Press, Inc.

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