Microbial Flora and Storage Quality of Partially Processed Lettuce

Storage of partially processed lettuce resulted in an increase in microbial population, pH, and change in package atmosphere composition (increasing CO 2 and decreasing O 2 ). Microbial populations varied in size with variations in processing and packaging. Typical initial log 10 counts per g were: bacteria 3.4–5.1, yeasts 2.5–3.2; molds were infrequent. Commercial packaging inhibited bacterial growth and retarded browning. Although Gram‐negative bacteria were numerically dominant, a large yeast population was also found. Species in the genera Pseudomonas, Erwinia , and Serratia were the most frequently isolated bacteria. Cryptococcus, Pichia, Torulaspora and Trichosporon spp. were the most common yeasts.