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United States Department of Agriculture

Agricultural Research Service


Location: Food Science Research

2008 Annual Report

1a.Objectives (from AD-416)
Our objectives are to: (1) develop reduced salt fermentation procedures for cucumbers and cabbage that will consistently produce vegetables with firm texture and appropriate flavor; (2) preserve non-fermented cucumbers and peppers in acidified, low-salt, or salt-free solutions so they can be stored and used as process-ready ingredients for food products; (3) develop processing technologies to convert sweetpotatoes into shelf-stable ingredients, such as puree and dehydrated powder, with physical, chemical, and sensory properties suitable for use as ingredients in restructured and formulated food products; (4) increase nutrients and beneficial phytochemicals in sweetpotato products by selection of cultivars with increased concentrations of target components and by optimization of processing conditions to minimize losses. Additional funds in support of project plan objectives 1,2,5: (1) to determine the metabolic changes that lead to the death of vegetable fermentation bacteria in response to acid and to develop approaches to assure growth of desirable fermentative organisms; (2) to understand and prevent degradation of the cell wall structure that results in softening of fermented and acidified vegetabes stored in low salt without thermal treatments.

1b.Approach (from AD-416)
New or improved processing methods will be developed for cucumbers, cabbage, peppers and sweetpotatoes that will increase utilization of these vegetables. Research will be done both to solve problems that limit utilization and to create opportunities to broaden uses for these vegetables as ingredients in formulated foods. Problems to be addressed include excessive generation of processing wastes, loss of quality attributes, and inadequate commercial shelf-life. Opportunities include development of new convenient-to-use ingredient forms for these vegetables and enhancement of the nutrient and beneficial phytochemical levels in products produced from these vegetables. Control of texture is a major quality issue that must be addressed in the development of improved processing methods. Therefore, the basic mechanisms which accelerate and inhibit softening of cucumbers, peppers, and cabbage will be investigated, as well as the factors that modify the rheology of sweetpotato puree. A recent development by this unit of an experimental technique to experimentally separate the effects of hydrogen ions from the effects of protonated acids on killing bacteria will be exploited to further our understanding of the physiology of acid tolerance in fermentative bacteria.

3.Progress Report
Began a second year of pilot scale salt-free cucumber fermentations at a commercial processing location to evaluate the commercial feasibility of brining cucumbers with calcium chloride to maintain firmness of the stored pickles. Evaluated the ability of bacteria isolated from anaerobic spoilage of commercially fermented cucumbers to carry out the spoilage under controlled conditions in the laboratory. Carried out laboratory fermentor experiments to determine the effects of aerobic and anaerobic conditions on changes in the redox potential of cucumber fermentations. Investigated adaptation of a recently developed microwave heating, aseptic filling technology developed for producing orange sweetpotato puree to purple sweetpotato cultivars that have high dry matter and anthocyanin contents. Carried out identification and analysis of major and minor anthocyanins and other phenolic compounds in purple sweetpotato cultivars. Continued development of methods to analyze normal and spoilage vegetable fermentations by two dimensional gas chromatography-mass spectrometry. Completed development of a method to measure volatile components of fermentations. Initiated research to analyze non-volatile fermentation metabolites by doing a derivatization procedure to make these metabolites volatile so they may be analyzed by gas chromatography.

This research addresses National Program 306 (Quality and Utilization of Agricultural Products), Component 1 (Quality, Characterization, Preservation and Enhancement), problem areas 1c (Factors and Processes that Affect Quality) and 1d (Preservation and/or Enhancement of Quality and Marketability) and Component 2 (New Processes, New Uses, and Value-Added Foods and Biobased Products), problem areas 2a (New Product Technology) and 2c (New and Improved Processes and Feedstocks).

1. Title: Bulk preservation of cucumbers without fermentation.

This accomplishment addresses National Program 306 (Quality and Utilization of Agricultural Products), Component 2 (New Processes, New Uses, and Value-Added Foods and Biobased Products) problem area 2C (New and improved Processes and Feedstocks). Developed guidelines for microbiological preservation of cucumbers without fermentation or application of a thermal process. Preservation is achieved by holding cucumbers in a solution containing acetic acid, sodium benzoate, and calcium chloride to maintain the firmness of the cucumbers. The stored cucumbers may then be further processed into edible pickle products. Preservation of cucumbers in bulk allows them to be shipped and be stored until there is demand for the product. This approach to preservation would reduce the generation of waste and the time and labor required to convert the stored cucumbers into consumer products.

2. Title: Use of unique genes to identify important bacterial species.

This accomplishment addresses National Program 306 (Quality and Utilization of Agricultural Products), Component 1 (Quality, Characterization, Preservation and Enhancement), problem area Problem Area 1b (Methods to Evaluate and Predict Quality).

Demonstrated the concept that a specific probe for a bacterial species can be found by comparing the genome of the target species to all bacterial genomes currently available. If the target bacterial species contains a unique gene, a DNA probe for that gene can be constructed so that any bacterial isolate can be readily checked to see if it the target bacterium. This approach to bacterial identification was successfully demonstrated for Lactobacillus plantarum, the organism that commonly ferments cucumbers to pickles. The approach used could be applied to any bacterial species for which the complete genome sequence has been determined.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of Other Technology Transfer1

Review Publications
Perez Diaz, I.M., Kelling, R., Hale, S., Breidt, F., McFeeters, R.F. 2007. Lactobacilli and tartrazine as causative agents of a red colored spoilage in cucumber pickle products. Journal of Food Science. 72(7):M240-M245.

Kim, J., Breidt, F. 2007. Development of preservation prediction chart for long term storage of fermented cucumber. Korean Journal of Life Sciences. 17(12):1616-1621.

Plengvidhya, V., Breidt, F., Lu, Z., Fleming, H.P. 2007. DNA fingerprinting of lactic acid bacteria in sauerkraut fermentations. Applied and Environmental Microbiology. 73(23):7697-7702.

Perez Diaz, I.M., McFeeters, R.F. 2008. Microbiological preservation of cucumbers for bulk storage by the use of acetic acid and food preservatives. Journal of Food Science. 73(6):M287-M291.

Grabowski, J.A., Truong, V., Daubert, C.R. 2007. Nutritional and rheological characterization of spray dried sweetpotato powder. Lebensmittel Wissenschaft und Technologie. 41:206-216.

Brinely, T.A., Truong, V., Coronel, P., Simunovic, J., Sandeep, K.P. 2008. Dielectric properties of sweetpotato purees at 915 MHz as affected by temperature and chemical composition. International Journal of Food Properties. 11:158-172.

Steed, L.E., Truong, V. 2008. Anthocyanin content, antioxidant activity and selected physical properties of flowable purple-fleshed sweetpotato purees. Journal of Food Science. 73(5):S215-S221.

Kumar, P., Coronel, P., Truong, V., Simunovic, J., Swartzel, K.R., Sandeep, K.P., Cartwright, G.D. 2008. Overcoming issues associated with the scale-up of a continuous flow microwave system for aseptic processing of vegetable purees. Food Research International. 41(5):454-461.

Last Modified: 7/23/2014
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