Surveys were made of commercial processing lines used to prepare fresh-cut vegetables such as chopped salad ingredients, carrot sticks, and cauliflower florets. Washing and chlorinated water dips only partially removed the microorganisms that were intrinsic to the vegetables. Major sources of in-plant contamination were the shredders used to prepare chopped lettuce and coleslaw. Gram-negative rods were the predominant microflora with species of Pseudomonas being most numerous; many were psychrotrophic. Only low numbers of lactic acid bacteria and fungi were recovered.

The objective was to determine the effect of cider composition on the heat resistance of Escherichia coli O157:H7. The average D52 value in a model Empire apple juice was 18 min with a z value of 4.8 degrees C. Increasing the Brix from 11.8 to 16.5 degrees had no effect on thermal resistance, while increasing L-malic acid from 0.2 to 0.8%, or reducing the pH from 4.4 to 3.6 sensitized the cells to heat. The greatest effect on heat resistance was afforded by the preservatives benzoic and sorbic acids: D50 values in ciders containing 1,000 mg/l were 5.2 min in the presence of sorbic acid and only 0.64 min in the presence of benzoic acid. Commercial apple juice concentrates yielded lower numbers of survivors than single-strength juices even though their higher sugar concentrations of about 46 degrees Brix increased heat resistance.

A comparison between the heat resistant ascospores of Byssochlurnys fulva and Aspergilfus sp. WRl revealed both similarities and differences. Similarities included a requirement for heat to break spore dormancy, the stimulation of heat activation by grape juice and other solutions, a nonlogarithmic order of death, and increased heat resistance in sugar solutions. A major difference was their response to organic acids: The survival of the Aspergillus in various acids was comparable to that in distilled water indicating no effect of the acids on heat resistance. With B. fulva, higher survivals were obtained in malic, tartaric, and citric acids. A major reduction in heat resistance of B. fulvu was observed in the presence of fumaric, lactic, succinic and acetic acids.