Practical Implications of Injured Microorganisms in Food

Abstract

Recognition of sublethally impaired microorganisms is essential to practical interpretations of data in food microbiology. Sublethal injury induced by exposure to environmental stress often is demonstrated as a loss by the microorganism of one or more abilities to function characteristically under conditions that are satisfactory for untreated cells. Various treatments related to food processing such as heat; cold; freezing-thawing; freeze-drying; moisture reduction; irradiation; and exposure to food environments, sanitizers. or preservatives may induce sublethal damage in cells or spores. Many cellular modifications may be observed in injured cells. Included are susceptibility to selective agents and antimicrobials, leakage of intracellular material, and modified metabolic activities. Injury is characterized by the capability of the microorganism to return to normalcy during a resuscitation process in which the damaged essential components are repaired. Sublethal damage in spores must be considered specially because of the complexity of the spore entity and its characteristic high resistance to stress. Extent of sublethal damage and mechanisms of injury and repair are varied and related to conditions of stress and resuscitation. Knowledge of sublethal injury is indispensable in evaluating laboratory data, in developing or modifying food processes, and in preservating culture activity.