Vegetable salad ingredients (lettuce, tomatoes, broccoli, and cauliflower) purchased from three grocery-store deli operations were analyzed for total plate count, coliforms, yeasts, and molds. The temperature of the vegetable ingredients was measured at the time of purchase and the pH was measured on all samples within one-half hour after purchase. In the second phase, fresh broccoli was processed into florets, inoculated with E. coli ATCC 23742, and subjected to three washing treatments.
The temperature of the salad ingredients ranged from 5.1°C to 18.9°C. The pH ranges for the vegetables were broccoli, 5.46 to 6.39; cauliflower, 5.82 to 6.65; lettuce, 4.92 to 6.38; and tomatoes, 3.30 to 4.47. The total aerobic count for the vegetables ranged from 5.51 to 6.63 log CFU/g. Coliforms on the vegetables ranged from 4.89 to 6.30 log CFU/g. Yeasts and molds were found on all vegetables. The results of the study indicate that the temperature conditions and pH ranges for the broccoli, cauliflower, and lettuce could support microbial growth. The pH range of the tomatoes was below 4.6, but if contaminated and added to low acid foods, the tomatoes may also act as a vehicle for microbial contamination.
When a chlorine wash solution was used, it slightly reduced the aerobic microbial load on previously inoculated broccoli and reduced the coliform population of the broccoli by approximately one log unit.
† This manuscript has been assigned Journal Series no. 10597, Agricultural Research Division, University of Nebraska and is based on research conducted under project NEB91-033.