2007 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.
Use of a bacterial culture to achieve consistent quality for low salt sauerkraut fermentations
Sauerkraut fermentation is carried out commercially by mixing 2 to 2.25% salt with shredded cabbage and relying upon natural lactic acid bacteria on the cabbage to ferment it into sauerkraut. There is a large volume of waste brine with high chloride content generated by this process. In addition, variations in the natural bacteria on the cabbage leads to considerable variation in the quality of the sauerkraut produced. We found that addition of an appropriate culture of Leuconostoc mesenteroides resulted in uniform production of good quality sauerkraut when the salt level in the cabbage was reduced to 1%. This result suggests that the chloride content of sauerkraut waste could be reduced by 50% while at the same time improving the consistency of the sauerkraut fermentation process by the addition of an appropriate bacterial culture to the shredded cabbage. This research addresses National Program 306 problem area 2c (New and Improved Processes and Feedstocks).
Method to determine adequate heat processing to assure safety in aseptic processing of sweetpotato purees using a continuous-flow microwave system.
A process for rapid sterilization and aseptic packaging of sweetpotato purees using a continuous flow microwave system operating at 915 MHz has been successfully developed. For commercialization of this technology, techniques for microbial validation of the process should be available for food processors to demonstrate the product safety. This study aimed to assess the feasibility of using plastic pouches of biological indicators containing spores of Geobacillius stearothermophilus and Bacillus subtilis for evaluating the degree of microbial inactivation achieved in sweetpotato purees processed in this microwave system. Spore survival after processing, as evaluated by use of growth indicator dyes and standard plating methods verified inactivation of the spores in sweetpotato puree. The log reduction results for B. subtilis were equivalent to the pre-designed degrees of sterilization (F0). This study presents the first report demonstrating that bio-indicators can be used to evaluate thermal inactivation efficacy in a continuous flow microwave process. This microbial validation technique will be useful to food processors to obtain the data needed to assure product safety and to obtain FDA approval for commercial processing of products with the new microwave heating system. This research addresses National Program 306 problem area 2a (New Product Technology).
5.Significant Activities that Support Special Target Populations
|Number of non-peer reviewed presentations and proceedings||10|
Makarova, K., Slesarev, A., Wolf, Y., Sorokin, A., Mirkin, B., Koonin, E., Pavlov, A., Pavlova, N., Karamychev, V., Polouchine, N., Shakhova, V., Grigoriev, I., Lou, Y., Rohksar, D., Lucas, S., Huang, K., Goodstein, D.M., Hawkins, T., Plengvidhya, V., Welker, D., Hughes, J., Goh, Y., Benson, A., Baldwin, K., Lee, J.H., Perez Diaz, I.M., Dosti, B., Smeianov, V., Wechter, W.P., Barabote, R., Lorca, G., Altermann, E., Barrangou, R., Ganesan, B., Xie, Y., Rawsthorne, H., Tamir, D., Parker, C., Breidt, F., Broadbent, J., Hutkins, R., O'Sullivan, D., Steele, J., Unlu, G., Saier, M., Klaenhammer, T., Richardson, P., Kozyavkin, S., Weimer, B., Mills, D. 2006. Comparative genomics of the lactic acid bacteria. Proceedings of the National Academy of Sciences. 103(42):15611-15616.
Breidt, Jr., F., McFeeters, R. F., and Diaz-Muniz, I. 2007. Fermented Vegetables. In: Food Microbiology: Fundamentals and Frontiers, 3rd Ed. M. P. Doyle and L. R. Beuchat, eds, ASM Press, Washington, D.C. p. 783-793
Yoon, S., Barrangou-Poueys, R., Breidt, F., Fleming, H.P. 2007. Detection and characterization of a lytic Pediococcus bacteriophage from the fermenting cucumber brine. Journal of Microbiology and Biotechnology. 17(2):262-270.
Johanningsmeier, S.D., McFeeters, R.F., Fleming, H.P., Thompson, R.L. 2007. Effects of Leuconostoc mesenteroides starter culture on fermentation of cabbage with reduced salt concentrations. Journal of Food Science. 72(5):M166-M172.
Teow, C.C., Truong, V., McFeeters, R.F., Thompson, R.L., Pecota, K.V., Yencho, C.G. 2007. Antioxidant activities, phenolic and ß-carotene contents of sweet potato genotypes with varying flesh colours. Food Chemistry. 103:829-838.
Kumar, P., Coronel, P., Simunovic, J., Truong, V., Sandeep, K.P. Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions. Journal of Food Science. 2007. J. Food Sci. 72(4):E177-E183.
Brinley, T.A., Dock, C.N., Truong, V., Coronel, P., Kumar, P., Simunovic, J., Sandeep, K., Cartwright, G.D., Swartzel, K.R., Jaykus, L. 2007. Feasibility of utilizing bio-indicators for testing microbial inactivation in sweetpotato purees processed with a continuous flow microwave system. Journal of Food Science. 72(5):E235-E242.
Truong, V., McFeeters, R.F., Thompson, R.L., Dean, L.L., Shofran, B. 2007. Phenolic acid content and composition in leaves and roots of common commercial sweetpotato (Ipomea batatas L.) cultivars in the United States. Journal of Food Science. 72(6):C343-C349.