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ARS Home » Research » Publications at this Location » Publication #105385
Title: BIOLUMINESCENCE ATP ASSAY FOR ESTIMATING TOTAL PLATE COUNTS OF SURFACE MICROFLORA OF WHOLE CANTALOUPE AND DETERMINING EFFICACY OF WASHING TREATMENTS

Author
item Ukuku, Dike
item PILZOTA, VLASTA - VISITING SCIENTIST
item Sapers, Gerald

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2000
Publication Date: 12/29/2000
Citation: N/A

Interpretive Summary: Minimal processing of fruits and vegetables includes handling, preparation, and packaging of agricultural commodities in a fresh-like state, and may include processes such as dicing, trimming and low level irradiation. The main selling attributes of minimally processed fruits and vegetables are convenience and fresh-like quality. In today's fast-paced life style such commodities are becoming an important component of the food supply thereby increasing the chances of outbreaks of human diseases associated with the consumption of raw fruits and vegetables. Time is a major factor when analyzing highly perishable foods before release to the public. Therefore, methods for analyzing food microbial loads within minutes are needed. A bioluminescence ATP assay was used to estimate the level of microflora on cantaloupe surfaces before and after washing treatments. Results were obtained within minutes and were in agreement with conventional plate count tmethods which requires 2 to 3 days incubation. Chlorine or hydrogen peroxide wash treatments caused a reduction of surface microflora of cantaloupes as determined by the plate count method. Reduction of total ATP as determined by the bioluminescence ATP assay after the washing treatment showed the same trend as seen in the plate count method. The results suggest that the bioluminescence ATP assay may be used by the produce industry as a quick alternative in estimating surface microbial load of fruits and vegetables. This method is fast, sensitive and cost effective and can be used to help the produce industries in designing and implementing good manufacturing practices.

Technical Abstract: The surface microflora of cantaloupe were estimated using a bioluminescence ATP assay, and results were compared to plate count data. Cantaloupes were treated as follows: water-washed, dipped in sodium hypochlorite (1000 ppm), or dipped in 5% hydrogen peroxide for 5 min. Bioluminescence ATP assay results showed differences in ATP level/square centimeter of cantaloupes dipped in chlorine or hydrogen peroxide solution. ATP levels in chlorine or peroxide-dipped samples were less than controls suggesting antimicrobial action of the treatments in reducing microbial population on the cantaloupe's surfaces. The results of the microbial estimation by the bio- luminescence ATP assay and the aerobic plate counts were highly correlated (0.9380). Microbial counts of water-washed samples were not significantly different from the unwashed samples. Dipping in chlorine or hydrogen peroxide caused a significant (alpha less than 0.05) reduction in the aerobic plate count, and in the count of other plant-associated organisms that can not grow well at temperatures >30 degrees C. The yeast and mold count on the cantaloupe surfaces were reduce significantly.