YUMA, AZThe convenience of fresh-cut produce, which includes packaged lettuces, has greatly increased sales despite multiple foodborne outbreaks associated with these products. To reduce these risks, strict hygiene programs and sanitizers are used for decontamination once the food is harvested. Preventing microbial contamination in the fields is equally important. Researchers from three institutions (Rutgers University, University of California, Davis and University of Arizona), lead by Jorge M. Fonseca at the University of Arizona's Yuma Agricultural Center, experimented with the use of harpin, a substance known to boost plants' resistance to disease, prior to harvest. Their findings, published in the Journal of the American Society for Horticultural Science, support the need to treat produce.
The study was conducted in three states (California, New Jersey, and Arizona) using 'Sniper', 'Desert Queen', and 'Sahara' varieties of head lettuce. Three different strengths of harpin were applied to groups at each site 5 days before harvest. A control group at each site was treated only with tap water. Immediately after harvest, six lettuce heads from each group were stored in coolers for 3 hours before being cut into pieces and stored in sealed plastic bags.
The quality of the lettuce was evaluated based on eight points: overall visual quality (OVQ), browning edges, color, decay/breakdown/sliminess, aroma, crispness, off odor, and total aerobic plate count, which determines microbial load. Evaluations were conducted every 5 days for 20 days, and subjective criteria were based on the opinions of three judges.
Results varied by location. California's crops with the two lowest harpin levels had higher OVQ and lower microbial populations than the control. No difference in microbial population was noted in New Jersey, which may be attributed to the wet conditions following treatment and during harvest. Micro-organisms increase in inner a
|Contact: Michael W. Neff|
American Society for Horticultural Science