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Postharvest Quality and Safety in Fresh-Cut Vegetables and Fruits

Iwaoka, Wayne
University of Hawaii
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  • 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.
Using various processing treatments to control intentional and unintentional microbial contamination of fresh-cut produce can produce a number of unintended consequences on the fruit themselves, such as accelerated ripening and senescence. For example, cutting and dicing of fresh-cut produce can lead to more rapid softening of the tissue and microbial contamination and growth on the cut surface. Minimal processing and calcium treatment of cut papayas (as an example of a climacteric fruit) will be used to evaluate texture change and microbial growth of a cut (and ready-to-serve) fruit. This study will determine whether or not certain processing treatments can extend the shelf life and sensory characteristics of this fruit.
More information
Non-Technical Summary: Consumption of a wide variety of sufficient fruits and vegetables is being encouraged at a national level to prevent chronic diseases and some types of cancer. Although frequency of fruit and vegetable consumption has changed little from 1994 to 2005, sales of minimally processed fruit and vegetables appear to be increasing. A minimally processed (MP) product is defined as the handling, preparation, packaging and distribution of agricultural commodities in a fresh-like state, and usually involves cutting or/and trimming to provide ready-to-eat forms. However, one of the problems of minimally processed fruits is the physical alteration of the fruit can promote accelerated ripening and softening of the tissue. Other concerns include contamination and growth of microorganisms. By experimenting with various processing techniques, such as treatment of the papaya flesh with calcium compounds to strengthen cell walls and dipping cut fruit in a hot water bath, this study may find a method to delay the ripening process, increase firmness of papaya flesh, and delay microbial growth on the cut surfaces. A successful process would allow papaya farmers and food distributors to have a technique to supply a quality ready-to-eat fruit product to consumers with a reasonable shelf life in stores and supermarkets.

Approach: Papayas will be purchased from a local commercial source, washed, cut into ready-to-eat pieces, treated with various calcium solutions, packed into vacuum pouches, placed in a hot water bath, cooled, and then stored at 4 degrees Centigrade for at least 10 days. Samples will be removed periodically and the papaya texture will be analyzed using a commercial texture analyzer. Total aerobic microorganism growth (total plate count) will be determined. Different firmness measurements will be evaluated using analysis of variance and microbial growth will be plotted against number of days in storage. Efforts for sharing new information will be through scientific publications and working with local food processors providing ready-to-eat foods. Thus far, there are no reports on a combination of heat and calcium treatments on cut papaya pieces. This project will be successful if texture of the fruit is maintained for at least 10 days, microbial counts are low, and there is a minimum of papaya flesh damage during post treatment storage.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens