- Li, Yong
- University of Hawaii
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- End date
- Standardize methods for recovering pathogenic and spoilage microorganisms from intact and fresh-cut produce including tree nuts.
- Evaluate and control unintentional and intentional microbial contamination of intact and fresh-cut produce.
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- NON-TECHNICAL SUMMARY: Fresh fruits and vegetables represent an essential part of our daily diet. The U.S. consumption of fresh-cut produce has increased at an annual rate of approximately 10% since 1995. Unfortunately, a number of food-borne outbreaks have been associated with contaminated fruits and vegetables. Little is known about the fate of pathogenic bacteria on fresh-cut pineapple and papaya. This research will evaluate intervention technologies to enhance the microbial safety and extend the shelf life of these fresh-cut fruits.
APPROACH: Microorganisms involved in the spoilage of fresh-cut pineapple and papaya will be isolated and identified by culture-based methods. Pathogenic bacteria, such as Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes, will be inoculated on the fresh-cut fruits. Survival and growth characteristics of these pathogens will be investigated over time. To reduce contamination of the fresh-cut fruits, the effectiveness of various food-grade sanitizers will be assessed for eliminating spoilage and pathogenic microorganisms on the skin surface of pineapple and papaya.
PROGRESS: 2007/10 TO 2008/09
OUTPUTS: A total of 61 produce samples were collected from local farmers' market. The tested varieties included tomato, cucumber, pea sprouts, braising greens, kale, lettuce, mizuna, broccoli raab, spinach, Swiss chard, tatsoi, arugula, curly cress, and sumida watercress. The samples were homogenized in sterile peptone water, serially diluted, and plated on E. coli/coliforms Petrifilms (3M).
PARTICIPANTS: Hongfei He, Graduate Research Assistant, Department of Human Nutrition, Food and Animal Science, University of Hawaii at Manoa
TARGET AUDIENCES: Farmers, consumers
IMPACT: 2007/10 TO 2008/09
Coliforms were detected in 80% of the samples, ranging from 0 to 5.4 log10CFU/g. Three spinach samples and one cucumber sample were positive in E. coli test. Coliforms are naturally occurring on plants. E. coli is not part of the normal microflora of fresh produce; therefore, their presence could be related to fecal contamination. This study yielded baseline microbiological indicator data for local produce.
PROGRESS: 2006/10/01 TO 2007/09/30
OUTPUTS: Fresh-cut pineapple and papaya were stored aerobically in the refrigerator. The microbial counts and pH of the fruits were determined at a 2-day interval for up to 12 days. The samples were homogenized in sterile peptone water, serially diluted, and plated on plate count agar (PCA) and potato dextrose agar acidified with tartaric acid (PDA). During refrigerated storage, the pH of pineapple ranged from 3.81 to 3.99. The pH of papaya was much higher, spanning from 4.95 to 5.61. Yeast and mold were dominant microorganisms in fresh-cut pineapple, with the PDA counts (3.5-4.4 log CFU/g) higher than or comparable to the PCA counts (3.2-4.2 log CFU/g). In fresh-cut papaya, however, the PDA counts remained low (2.6-3.6 log CFU/g) while the PCA counts ranged from 4.1 to 5.4 log CFU/g.
PARTICIPANTS: Dr. Jin Dong, Junior Researcher, Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa
TARGET AUDIENCES: Fresh-cut fruit industry and consumers
IMPACT: 2006/10/01 TO 2007/09/30
These results suggest the microbial populations differ in fresh-cut pineapple and papaya during refrigerated storage. pH may affect the relative levels of bacteria and fungi in the fruits. This lays the groundwork for future research on developing control strategies to extend the shelf-life of the fresh-cut fruits.
- Funding Source
- Nat'l. Inst. of Food and Agriculture
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- Bacterial Pathogens
- Escherichia coli