Progress 08/01/02 to 08/01/07
Outputs
Progress Report Objectives (from AD-416) The objective of this cooperative research project is to develop improved processing technologies for cucumbers, peppers, cabbage, and sweetpotatoes that will benefit growers and processors in the U.S. Specific areas of interest will be: (1) to determine procedures to assure microbiological stability of new processing techniques for extending shelf life of vegetables and (2) to determine the effects of processing and storage on the flavor and textural quality of vegetables. Approach (from AD-416) We will utilize commercial cultivars of these commodities that are currently grown in North Carolina and materials from breeding and evaluation programs at NC State University. The vegetables will be preserved and stored using acidification, fermentation, and/or refrigeration, along with appropriate pre-treatments, to improve the efficiency of processing and the quality attributes of vegetables. Sensory and instrumental evaluation of flavor and textural processed vegetables will be carried out. Pilot-scale or commercial trials to evaluate the potential for scale-up of laboratory results will be done either at NCSU facilities or at commercial processing facilities in the state. Significant Activities that Support Special Target Populations This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41000-005-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. Progress was monitored by meeting and reviewing results with principle investigator and scientists carrying out research. The cucumber pickling industry has sporadically experienced spoilage outbreaks in pickled cucumber products characterized by development of red color on the surface of the cucumbers. Lactobacillus casei and Lactobacillus paracasei were isolated from two outbreaks of this spoilage which occurred about fifteen years apart during the last three decades. Both organisms were shown to produce this spoilage when inoculated into pickled cucumbers while concomitantly degrading the azo dye tartrazine (FD&C yellow no. 5). This food dye is used as a yellow coloring in the brine cover solutions of commercial pickled cucumber products. The red color does not occur in the absence of tartrazine, nor when turmeric is used as a yellow coloring in the pickles. Addition of sodium benzoate to the brine cover solutions of a pickled cucumber product, more specifically hamburger dill pickles, prevented growth of these lactic acid bacteria and the development of the red spoilage.
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-004-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. The biofilm behavior of Listeria monocytogenes in an experimental ecosystem to simulate biofilm formation on machinery in vegetable processing operations was investigated. Biofilms were initially formed on stainless steel and Teflon coupons using a five- strain mixture of L. monocytogenes. The coupons were then subjected to repeated 24-h daily cycles. Each cycle consisted of three sequential steps: (i) a brief (60 sec.) exposure of the coupons to a sanitizing agent; (ii) drying and storage of the coupons in plastic tubes for 15 h; (iii) incubation of the
coupons in diluted medium for 8 h. This regimen was repeated daily for up to three weeks. The survival of bacteria was determined during the repeated sanitizing cycles. The data suggest that the treated biofilms as a whole, but not the individual cells in the biofilm, developed enhanced resistance to sanitizers, possibly due to attributes in the biofilm structure.
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-004-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. Fresh-pack dill pickles were made from pickling cucumbers and packed in glass containers. Oxygen and turmeric were added to the pickles, then volatile aldehydes were analyzed as a function of time using purge and trap, and gas chromatography-mass spectrometry. Commercial pickle products were also analyzed. Hexanal was the major oxidative aldehyde formed. It was used as an indicator of oxidative off- flavor formation. Hexanal formation increased as the amount of oxygen in the container increased. Turmeric was found to retard formation of hexanal and other aldehydes with
increasing effectiveness as the concentration increased from 16 to 250 ppm. Turmeric was found to be an effective antioxidant at concentrations appropriate for coloring in pickles. Freeze-dried powders of five sweetpotato cultivars with varying flesh colors were extracted with hexane and acidified methanol, and the antioxidant activity was measured by three different methods. Total phenolics and beta-carotene were also measured. A purple-fleshed sweetpotato cultivar had the highest antioxidant activity and a white- fleshed variety had the lowest activity. Commercial orange-fleshed cultivars with high beta-carotene content were intermediate in antioxidant activity. The different methods for measuring antioxidant activity were highly correlated suggesting that they have similar predictive capability for estimating the antioxidant activity of sweetpotatoes.
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Progress 10/01/03 to 09/30/04
Outputs
4. What were the most significant accomplishments this past year? This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-003-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. DNA fingerprinting methods were used to follow the progress of unmarked starter cultures in laboratory sauerkraut fermentations. Random prime PCR (RAPD-PCR) was used for strain-specific identification of Leuconostoc mesenteroides cultures. This technique was used to show that added starter cultures dominated the early stages of sauerkraut fermentations. Research is being conducted to evaluate the effectiveness of ascorbic acid and turmeric as antioxidants to prevent the formation in oxidative off-flavors in cucumber pickles.
Procedures were developed to add oxygen to pasteurized pickles in order to consistently form sufficient quantities of oxidative aldehydes such that the antioxidant compounds can be properly evaluated. Annotation of the genome of Leuconostoc mesenteroides was carried out to identify all of the genes present in this organism that match current databases. This is the primary organism that carries out the early stages of sauerkraut fermentations.
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