61C-15 |
Microbiological survey of sweet potato roots during storage |
A. C. BOVELL-BENJAMIN1, E. Bromfield2, A. Dessai2, R. D. Pace2, and B. Wang2. (1) Dept of Food and Nutritional Sciences, Tuskegee University, 300-A Campbell Hall, Tuskegee, AL 36088, (2) Food and Nutritional Sciences, Tuskegee University, 100 Campbell Hall, Tuskegee, AL 36088 Sweet potatoes (Ipomoea batatas) are capable of supporting the growth of most microorganisms due to their high water activity (aw). The sweet potato is of interest because of its high β-carotene, vitamin C, fiber and carbohydrate contents, and it is baselined to be grown in space. The peel of the sweet potato serves as a physical barrier against potentially pathogenic microbes, but heat can destroy the barrier, and degrade complex carbohydrates into forms more usable by microorganisms, thus creating a food safety problem. The microbiological quality of field and hydroponically grown sweet potatoes stored at 13°C and 21°C was evaluated. Samples of TU-82-155 hydroponic sweet potatoes (HSP) and Beauregard field sweet potatoes (FSP) were stored in palletized crates at 13°C, 21°C and 85% RH for five weeks, randomly withdrawn at weekly intervals, and placed in sterile bags for microbiological analyses. Whole, unpeeled sweetpotatoes were washed, shaken in 1 % peptone water, and then ten fold serial dilutions made. The dilutions were plated on TSA for bacterial count, and on PDA for fungi and yeasts counts, and then incubated at 38°C for 12h and 48h, respectively. Plate counts were done to determine the frequency and types of colony growth, and then colonies were isolated and characterized by Biolog. The plate counts at both temperatures ranged from 3.75x 104 CFU/ml to 1.5x 108 CFU/ml, and 6.23x 105 to 2.11x 108 CFU/ml for HSP and FSP, respectively. The microbial genera on the HSP included Aurobacterium, Bacillus, and Rahnella. Staphylococcus genus was present on HSP and FSP. Absidia, Cryptococcus, Fusarium and Alternaria spp. were found on the HSP and FSP. Most bacteria found on the sweet potatoes were not of public health significance, however, storage temperature management should receive more attention in terms of identifying and controlling microbiological hazards on fresh sweet potatoes.
Session 61C, Food Microbiology: General I
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