No 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.

4. Summary Indicators and surrogate microorganisms may be used for evaluating safety of fresh or fresh‐cut fruit and vegetable products by assessing or validating the effectiveness of microbial control measures. Although frequently used on an informal basis within a specific company, use of indicators is highly dependent upon microbiological criteria that are in place for the specific produce item or category. All the considerations that must be addressed in establishing microbiological criteria must also be in place if indicators are to be utilized in process verification. Sampling design, stringency, and statistical significance are critical to the evaluation of indicators or surrogates in the assurance of food safety. General ideal qualities of indicators and surrogates are valuable starting points when developing a safety program. The importance of selecting the significant target pathogen for the specific product, its source, handling practices, and distribution practices cannot be overemphasized. The same is true for selection of the indicator or surrogate to represent those pathogens. The extensive lists of considerations and procedures should be helpful when using indicators and surrogates with fresh and fresh‐cut produce. The use and limitations of indicators and surrogates to determine or validate treatment effectiveness have been delineated. Challenges are identified for selection of an indicator or surrogate for the specific situation and conditions of an individual produce item, including growing, harvesting, processing, handling, storage, and packaging.

Bacillus cereus has been implicated as the cause of both diarrheal and emetic forms of food‐borne illness. Spores of eight strains of B. cereus, representing diairheal, emetic and atoxigenic origins, were examined for heat resistance and germination responses. No correlation was observed between heat resistance at 85° or 90°C and origin of the strain. Germination of spores in Trypticase soy broth at 30°C, measured by loss of heat resistance, was more extensive for diarrheal strains than for emetic strains. These data should be useful in evaluating potential hazards from B. cereus in foods.