2006 Annual Report 1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? For the pickled and acidified vegetable industry to remain competitive in national and international markets with value-added products from these minor crops, sustained research is needed to improve product quality and develop better processing methods that generate less waste, particularly chlorides from salt. The sweetpotato is also a relatively minor vegetable crop in the U.S. Despite the fact that it is a highly nutritious vegetable, consumption of sweetpotatoes has declined slowly. To increase utilization in the U.S. diet, technologies are needed to convert sweetpotatoes into new forms, such as purees or dehydrated flakes, to be used as ingredients for convenient, value-added products. To assure that sweetpotato products will deliver the high nutritional value that is expected, new cultivars that are introduced need to maintain or increase the levels of carotenoids (orange sweetpotatoes), anthocyanins (purple sweetpotatoes), and phenolic compounds in currently grown cultivars. Processing methods for all of these vegetables need to be developed that minimize losses of components which are beneficial to human health. Major objectives for this project are: (1) to develop reduced salt fermentation procedures for cucumbers and cabbage; (2) to preserve non-fermented cucumbers and peppers in acidified low salt solutions so they can be stored and used as process-ready ingredients for food products; (3) to develop processing technologies to convert sweetpotatoes into high quality, shelf-stable ingredients, such as purees or dehydrated powders; (4) to increase the content of nutrients and beneficial phytochemicals delivered in vegetable products by cultivar selection and optimization of processing methods. Customers for this research are farmers who produce vegetables for commercial processing and food processors that develop and manufacture products from cucumbers, cabbage, sweetpotatoes, and peppers. Specific customers include Pickle Packers International, Inc. (a trade association that represents most of the major processors for fermented and acidified vegetables in the United States), The Sweetpotato Council of the United States, and The North Carolina SweetPotato Commission. While commercial food production is the focus of this Unit, through extension programs the results are transferable to home preservation and processing of these vegetables. The research findings benefit the scientific community with new information on the biochemistry of processed vegetables, development of techniques for food fermentations, and analytical techniques for chemical components of vegetables and microorganisms related to processed vegetable products. 2.List by year the currently approved milestones (indicators of research progress) FY 2005 1. Determine characteristics of enzymatic and non-enzymatic softening in low salt cucumber fermentations (1). 2. Determine the effect of sodium chloride reduction on texture, flavor, and color of sauerkraut (12). 3. Determine the effect of culture addition on low-salt sauerkraut fermentation (14). 4. Determine the effects of oxygen radicals on softening of peppers and cucumbers (21). 5. Determine microbiological and sensory stability of fresh-cut, refrigerated sweetpotato pieces (24). 6. Determine the dielectric properties and predictive equations for microwave heating of sweetpotato puree (25). 7. Develop predictive equations for microwave heating of sweetpotato puree (26). 8. Evaluate the technical feasibility of microwave sweetpotato puree sterilization with a small-scale microwave processing unit (27). 9. Scale-up microwave processing with pilot-scale microwave unit and evaluate aseptic packaging of microwave-heated puree (28). 10. Determine pre-treatments of sweetpotato purees required to make spray-dried sweetpotato powder (33). 11. Establish appropriate drying parameters for production of spray-dried sweetpotato powder (34). 12. Develop extraction methods for carotenoids, phenolic compounds, and anthocyanins in sweetpotatoes suitable for analysis of several hundred breeding lines each year (39). 13. Determine the survival of Escherichia coli exposed to different food acids (44). 14. Develop mechanistic models to describe the killing effects of acids on acid-tolerant pathogens (46). FY 2006 1. Evaluate the effect of salt reduction on texture, flavor, and stability of fermented cucumbers (2). 2. Determine the effect of sodium chloride reduction on texture, flavor, and color of sauerkraut (12). 3. Determine the effect of addition of calcium, potassium, and magnesium salts on texture retention, flavor, and color of sauerkraut (13). 4. Isolation and identification of organisms causing low salt spoilage of cucumbers 5. Characterization of the molecular ecology of spoilage fermentations 6. Determine the effect of low or no added sodium chloride on firmness of preserved small cucumbers (17). 7. Determine optimum combinations of calcium, potassium, magnesium, and alum salts for preservation of firmness in cucumbers and peppers during storage (18). 8. Determine concentrations of sulfite, benzoate, and sorbate required to assure microbial stability in acidified, non-fermented cucumbers and peppers (19). 9. Verify the delivery of a sufficient heat process to all locations in the heating volume of the microwave unit to assure destruction of Clostridium botulinum spores (29). 10. Determine retention of texture, color, flavor, nutrients, and beneficial phytochemicals during storage of microwave-sterilized sweetpotato puree (30). 11. Develop extraction methods for carotenoids, phenolic compounds, and anthocyanins in sweetpotatoes suitable for analysis of several hundred breeding lines each year (39). 12. Develop analytical methods to separate, identify, and quantitate carotenoids, phenolic compounds, and anthocyanins in sweetpotato breeding lines and for evaluation of changes during processing and storage (40). FY 2007 1. Evaluate modifications of brining conditions on the dominance of fermentation cultures added to cucumber fermentations (4). 2. Isolate organisms responsible for low-salt spoilage of fermented cucumbers (5). 3. Biochemical and genetic characterization of low-salt spoilage organisms in cucumber fermentations (6). 4. Identify species-specific DNA probes; functional trials of 16S microarrays to detect microbial species in cucumber fermentations (9). 5. Evaluate the microbial ecology of added and natural fermentation microorganisms in laboratory sauerkraut fermentations (15). 6. Determine conditions of low-salt acidified storage which will assure killing of acid-tolerant pathogens in stored cucumbers and peppers (20). 7. Determine the functional performance of microwave-sterilized sweetpotato puree in model food systems (31). 8. Evaluate the quality characteristics of spray-dried sweetpotato powders produced with selected drying conditions (36). 9. Develop analytical methods to separate, identify, and quantitate carotenoids, phenolic compounds, and anthocyanins in sweetpotato breeding lines and for evaluation of changes during processing and storage (40). 10. Determine the effects of processing operations, including peeling, sterilization heating, and spray drying, on the retention of carotenoids, phenolic compounds, and anthocyanins in commercial sweetpotato cultivars (42). FY 2008 1. Evaluate the effects of the addition of calcium, potassium, magnesium, and alum salts on texture, flavor, and stability of fermented cucumbers (3). 2. Determine conditions that prevent growth of low salt spoilage organisms in fermented cucumbers (7). 3. Determine the ecology of laboratory cucumber fermentations (10). 4. Determine changes in cell walls that occur during oxygen-mediated softening of peppers (22). 5. Evaluate the utilization of sterilized sweetpotato puree in selected processed foods (32). 6. Determine the functionality of spray-dried sweetpotato powders in model food systems (37). 7. Evaluate the incorporation of spray-dried sweetpotato powder in selected processed foods (38). 8. Develop models to describe changes in phytochemicals during processing and storage of sweetpotatoes (43). FY 2009 1. Fermentation challenge evaluations in low-salt cucumber fermentations (8). 2. Determine the ecology of cucumber fermentations under commercial conditions (11). 3. Determine the microbial ecology of low-salt sauerkraut fermentations under commercial fermentation conditions (16). 4. Determine changes in cell walls that occur during oxygen-mediated softening of peppers (22). 4a.List the single most significant research accomplishment during FY 2006. A new understanding of the chemistry of acids that cause sour taste, one of the basic human taste perceptions. This project was conducted under a USDA-CSREES-NRICGP grant no. 2003-01479 to ARS and in cooperation with North Carolina State University. This accomplishment addresses Problem area 1a, ‘Definition and Basis for Quality’. The objective was to test the our recent hypothesis that perceived sourness intensity in acid solutions or foods is a linear function of the molar concentration of all organic acid species with at least one protonated carboxyl group plus the molar concentration free hydrogen ions. Results of the project confirmed this hypothesis both in water solutions of acids and in a fresh pack dill pickle product. This outcome provides significant new insights about sour taste. Implications of these results are that (a) common organic acids in foods are all equally sour on a molar basis, (b) that all species of an organic acid with one or more protonated carboxyl groups are equally sour, (c) that the hydrogen ion is about equal in sour intensity to a protonated organic acid molecule. It was also found that within the pH range of most acid or acidified foods (pH 3.0 to 4.6) the hydrogen ion itself will have very little direct contribution to the total sour taste of a solution or a food. It was also observed that in a pickle product the sour intensity of the acids is substantially suppressed compared to their sour intensity in simple water solutions. The chemistry of this taste suppression effect is not yet understood. Since there is a linear relationship between sour flavor intensity and the molar concentrations or all organic species in a particular type of food, it will be possible to predict changes in sour intensity that result from substituting different acids in the product or from changing the pH of the product. However, because the sour suppression effects of different food components are not known, it is not yet possible to create a general model for predicting sour flavor intensity in foods. These results provide new understanding of the acid chemistry that elicits sourness as a basic human taste perception. 4b.List other significant research accomplishment(s), if any. Turmeric, used as a yellow coloring in some pickle products, was shown have strong antioxidant activity that prevented formation of compounds that cause oxidative off-flavors. This accomplishment area addresses Problem area 1c, ‘Factors and Processes that Affect Quality’. Pickle products are increasingly packaged in plastic containers for customer convenience, to avoid breakage, and to reduce shipping weight. However, products in plastic containers typically have a shorter shelf-life than comparable products packaged in glass jars. One of the reasons for reduced shelf life is that the oxygen in air migrates into plastic containers during storage and causes development of off-odors. This project identified and measured compounds formed in fresh-pack dill pickles that may be responsible for off-odors. Turmeric was shown to also be an effective antioxidant and to prevent the formation of off-odor compounds when oxygen was intentionally injected into pickle products. This result suggests that turmeric may help extend the shelf life of pickle products in plastic packages. Spray drying to make a functional sweetpotato powder for use as a food ingredient. This accomplishment addresses problem area 2a ‘New Product Technology’. It is difficult to make a spray dried powder from sweetpotato puree due to its high viscosity. The effects of pretreatment with amylase to reduce viscosity, addition of maltodextrin to assist drying, and variation in the inlet temperature were tested for their effect on the characteristics of the spray dried powder. Evaluation of moisture content, color, water absorption, particle size, and powder density showed that good quality sweetpotato powders can be produced by spray drying that have potential applications in food and nutraceutical products. 4c.List significant activities that support special target populations. None 5.Describe the major accomplishments to date and their predicted or actual impact. Continuous microwave sterilization and aseptic packaging of sweetpotato puree. This is the first report of an aseptically packaged vegetable puree processed by a continuous-flow, microwave heating system. A patent application was filed November 12, 2004. Further studies are in progress to validate the process for microbial safety, as well as to expand its application to other fruit and vegetable purees. This technology provides a new process to convert sweetpotatoes and other highly nutritious fruits and vegetables into shelf-stable functional ingredients suitable for use in a variety of formulated food products. Expansion of the market for sweetpotato puree would provide farmers with a market for 40% of the sweetpotato crop, which currently is left in the field because of small size or poor shape that makes them unsuitable for sale. A new understanding of the chemistry of acids that cause sour taste, one of the basic human taste perceptions. This project was conducted under a USDA-CSREES-NRICGP grant no. 2003-01479 to ARS and in cooperation with North Carolina State University. This accomplishment addresses Problem area 1a, ‘Definition and Basis for Quality’. The objective was to test the our recent hypothesis that perceived sourness intensity in acid solutions or foods is a linear function of the molar concentration of all organic acid species with at least one protonated carboxyl group plus the molar concentration free hydrogen ions. Results of the project confirmed this hypothesis both in water solutions of acids and in a fresh pack dill pickle product. This outcome provides significant new insights about sour taste. Implications of these results are that (a) common organic acids in foods are all equally sour on a molar basis, (b) that all species of an organic acid with one or more protonated carboxyl groups are equally sour, (c) that the hydrogen ion is about equal in sour intensity to a protonated organic acid molecule. It was also found that within the pH range of most acid or acidified foods (pH 3.0 to 4.6) the hydrogen ion itself will have very little direct contribution to the total sour taste of a solution or a food. It was also observed that in a pickle product the sour intensity of the acids is substantially suppressed compared to their sour intensity in simple water solutions. The chemistry of this taste suppression effect is not yet understood. Since there is a linear relationship between sour flavor intensity and the molar concentrations or all organic species in a particular type of food, it will be possible to predict changes in sour intensity that result from substituting different acids in the product or from changing the pH of the product. However, because the sour suppression effects of different food components are not known, it is not yet possible to create a general model for predicting sour flavor intensity in foods. These results provide new understanding of the acid chemistry that elicits sourness as a basic human taste perception. 6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? Our results on sour taste perception have been presented to scientific and industry meetings. Since they address a basic taste perception, there is the potential to have a broad impact in food product development. An editor of Scientific American called and asked that he be contacted about this topic when the final results are published in a peer reviewed journal. Information on the use of turmeric as an antioxidant in acidified vegetables has been communicated at scientific and industry meetings. Approaches to using this information in specific applications have been discussed with individual processors. 7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below). Breidt, F. 2006. Modeling bacterial populations undergoing acid stress. Society for Industrial and Applied Mathematics. Raleigh, NC Grabowski, J.A., Truong, V.D., Daubert, C.R. 2006. Nutritional and rheological characterization of spray-dried sweetpotato powder. IFT Coronel, P., Truong, V.D., Kumar, P., Simunovic, J., Swartzel, K.R., Cartwright, G. 2006. Microwave-assisted aseptic processing of vegetable purees: cross-sectional temperature profiles during heating and sterilization. IFT. Coronel, P., Truong, V.D., Kumar, P., Simunovic, J., Swartzel, K.R., Sandeep, K.P. 2006. Microwave-assisted aseptic processing: dielectric properties of vegetable purees under static and continuous flow conditions. IFT. Teow, C.C., Truong, V.D., Thompson, R.L., McFeeters, R.F., Yencho, C.G. 2006. Antioxidant activity and anthocyanin content of raw and steamed purple-fleshed sweetpotatoes. IFT. McFeeters, R.F. 2006. Food Acids and the Intensity of Sour Flavor. Pickle Packers International, Spring meeting. Da Conceicao Neta, E., Johanningsmeier, S., Drake, M.A. and McFeeters, R.F. 2006. A Chemical Basis for Sour Taste Perception. CREES-NRI Improving Food Quality and Value Project Director’s meeting. Review Publications Coronel, P., Truong, V-D., Simunovic, J., Sandeep, K.P., Cartwright, G.D. 2005. Aseptic processing of sweetpotato purees using a continuous flow microwave system. Journal of Food Science. 70:E531-E537. Cleary, K.A., McFeeters, R.F. 2006. Effects of oxygen and turmeric on the formation of oxidative aldehydes in fresh-pack dill pickles. Journal of Agricultural and Food Chemistry. 54:3421-3427. Chin, H.S., Breidt, F., Fleming, H.P., Shin, W., Yoon, S. 2006. Identifications of predominant bacterial isolates from the fermenting kimchi using ITS-PCR and partial 16S rDNA sequence analyses. Journal of Microbiology and Biotechnology. 16:68-76. Mudgal, P., Breidt, F., Lubkin, S., Sandeep, K.P. 2006. Quantifying the significance of phage attack on starter cultures: a mechanistic model for population dynamics of phage and their hosts isolated from fermenting sauerkraut. Applied and Environmental Microbiology. 72:3908-3195. Grabowski, J.A., Truong, V.-D., Daubert, C.R. 2006. Spray-drying of amylase hyrolyzed sweetpotato puree and physicochemical properties of powder. Journal of Food Science. 71:E209-E217. Dougherty, D.P., Da Conceicao Neta, E.R., McFeeters, R.F., Lubkin, S.R., Breidt, F. 2006. Semi-mechanistic, partial buffer approach to modeling pH, the buffer properties, and the distribution of ionic species in complex solutions. Journal of Agricultural and Food Chemistry. 54:6021-6029. Shih, F.F., Daigle, K.W., Truong, V. 2006. Physicochemical properties of gluten-free pancakes from rice and sweet potato flours. Journal of Food Quality. 29:97-107.