Effectiveness of organic acid, ozonated water and chlorine dippings on microbial reduction and storage quality of fresh-cut iceberg lettuce

BACKGROUND: The comparative effects of organic (citric and lactic) acids, ozone and chlorine on the microbiological population and quality parameters of fresh-cut lettuce during storage were evaluated. RESULTS: Dipping of lettuce in 100mg L-1 chlorine solution reduced the numbers of mesophilic and psychrotrophic bacteria and Enterobacteriaceae by 1.7, 2.0 and 1.6 log(10) colony-forming units (CFU) g(-1) respectively. Treatment of lettuce with citric (5 g L-1) and lactic (5 mL L-1) acid solutions and ozonated water (4 mg L-1) reduced the populations of mesophilic and psychrotrophic bacteria by 1.7 and 1.5 log(10) CFU g(-1) respectively. Organic acid dippings resulted in lower mesophilic and psychrotrophic counts than ozonated water and chlorine dippings during 12 days of storage. Lactic acid dipping effectively reduced (by 2.2 log(10) CFU g(-1)) and maintained low populations of Enterobacteriaceae on lettuce for the first 6 days of storage. No significant (P > 0.05) changes were observed in the texture and moisture content of lettuce samples dipped in chlorine, organic acids and ozonated water during storage. Colour, beta-carotene and vitamin C values of fresh-cut iceberg lettuce did not change significantly (P > 0.05) until day 8. CONCLUSION: Lactic and citric acid and ozonated water dippings could be alternative treatments to chlorine dipping to prolong the shelf life of fresh-cut iceberg lettuce. (c) 2007 Society of Chemical Industry.