88D-28 |
Changes in appearance and natural microflora on iceberg lettuce treated in warm, chlorinated water and then stored at refrigeration temperature |
Y. LI, Dept. of Food Science & Technology, Univ.of Georgia, Center for Food Safety & Quality Enhancement, 1109 Experiment St., Griffin, GA 30223 and R. E. Brackett, Office of Plant & Dairy Foods & Beverages, U.S. Food & Drug Administration, 200 C St. S.W., Washington, DC 20204. The objective of this study was to determine the effect of warm, chlorinated water on the survival and subsequent growth of naturally occurring microorganisms and visual quality of fresh-cut iceberg lettuce. After dipping cut lettuce leaves in water containing 20 mg/L free chlorine for 90 sec at 50°C, samples were stored at 5 or 15°C for up to 18 or 7 days, respectively. Populations of aerobic mesophiles, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, and yeasts and molds were determined. The visual appearance and development of brown discoloration were monitored. Treatment of lettuce in warm (50°C) chlorinated water delayed browning of lettuce. Shelf life of lettuce stored at 5°C, as determined by subjective evaluation, was about 5 days longer than that of lettuce stored at 15°C. Treatment in warm water, with or without 20 mg/L chlorine, and in chlorinated water at 20°C significantly (ƒÑ=0.05) reduced the initial population of natural microflora. Populations increased, regardless of treatment, as storage time at 5°C and 15°C increased. The same trends were observed in populations of psychrotrophs, except higher numbers were attained in lettuce stored at 5°C compared to 15°C. Yeast populations increased slightly in lettuce stored at 5°C but were consistently about 3 logs lower than mesophilic aerobes. Populations of molds and lactic acid bacteria were less than log10 102 CFU g-1 throughout storage at 5 or 15°C. Results suggest that heat (50°C) treatment may be useful for reducing populations of some groups of microorganisms naturally occurring on iceberg lettuce, thereby extending shelf life.
Session 88D, Food Microbiology: General
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