Submitted to: Journal of Food Safety
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/26/2002
Publication Date: 8/26/2002
Citation: UKUKU, D.O., FETT, W.F. EFFECTIVENESS OF CHLORINE AND NISIN-EDTA TREATMENTS OF WHOLE MELONS AND FRESH-CUT PIECES FOR REDUCING NATIVE MICROFLORA AND EXTENDING SHELF LIFE. JOURNAL OF FOOD SAFETY. 2002. V. 22. P. 231-353. Interpretive Summary: Prepared fresh-cut melon (cantaloupe and honeydew) in the supermarket is becoming very popular with the U.S. consumer due to the benefits of a diet rich in fruits and vegetables and the convenience as no in-home preparation is required. To date, fresh-cut melon is prepared in the supermarket or by regional distributors. National distribution is difficult due to quality and safety concerns. In order to improve the microbial quality of fresh-cut melon, we studied the use of a combination of nisin (a natural bacterial product) with a compound (EDTA) which facilitates entry of nisin into bacteria with chlorine for reducing native microflora of whole melons and extending shelf life of fresh-cut pieces. Whole cantaloupe and fresh-cut pieces were washed with chlorine or nisin plus EDTA. The cut pieces were placed in bags and stored at 5 C for up 15 days. Microbial quality and changes in appearance, odor and overall acceptability of the fresh-cut melons were evaluated every 3 days. Both treatments substantially reduced the population of native microflora on whole cantaloupe and those transferred to fresh-cut pieces. Odor, appearance, and overall acceptability ratings for cantaloupe and honeydew fresh-cut pieces treated with nisin plus EDTA or chlorine were similarly improved compared to the controls for the fresh-cut pieces. The results of this study indicate that treatments with nisin plus EDTA before and after fresh-cut processing would improve the microbial quality and extend the shelf life of fresh-cut melon.
Technical Abstract: Efficacy of nisin-EDTA treatments as a sanitizing treatment for reducing native microflora of whole melons and extending shelf life of fresh-cut pieces was compared to chlorine treatments. Whole cantaloupe and honeydew melons were washed with water, nisin (10 g/ml)-EDTA (0.02 m), or 200 ppm chlorine for 5 min at ~ 20 C before fresh-cut preparation and storage at 5 C for 15 days with periodic microbiological sampling. In addition, some fresh-cut pieces were washed with 10 g/ml nisin-EDTA or 50 ppm chlorine for 1 min before storage. Changes in appearance, odor, overall acceptability and the shelf life of the minimally processed fresh-cut melons were investigated. Preliminary studies indicated that water washes, EDTA (0.002 to 0.2 M) or nisin (5 to 10 g/ml) were not effective in reducing the microflora of whole melon when used individually. Nisin-EDTA and chlorine treatments were significantly (p<0.05) more effective in reducing native microflora than water washes. Nisin-EDTA treatments were significantly (p<0.05) more effective than chlorine in reducing populations of yeast and mold and Pseudomonas spp. on whole melon surfaces but were not as effective as chlorine treatments for reducing aerobic mesophilic bacteria, lactic acid bacteria and total gram-negative bacteria. Microbial contaminants on fresh-cut pieces washed with 50 ppm chlorine or nisin-EDTA were further reduced. However, microbial populations increased throughout refrigerated storage irrespective of treatments. Odor, appearance, and overall acceptability ratings for cantaloupe and honeydew fresh-cut pieces treated with nisin-EDTA or chlorine were not significantly (p>0.05) different from each other throughout the storage period (15 to 21 days). However, both treatments led to significantly (p<0.05) improved ratings compared to the controls for the fresh-cut pieces at 9 to 12 days of storage and thereafter. The results of this study suggest that treatments with nisin-EDTA before and after fresh-cut processing would improve the quality and extend the shelf life of fresh-cut melon.