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ARS Home » Southeast Area » Raleigh, North Carolina » Food Science Research » Research » Research Project #428731

Research Project: Improved Processes for the Preservation and Utilization of Vegetables, Including Cucumber, Sweetpotato, Cabbage, and Peppers to Produce Safe, High Quality Products with Reduced Energy Use and Waste

Location: Food Science Research

2015 Annual Report

Objective 1. Enable the commercialization of reduced NaCl fermentation technology by identifying suitable starter cultures, optimizing processing parameters to prevent freezing of the fruits; and develop a shelf-life model that allows processors to rapidly and accurately predict end-use quality. Subobjective 1a: Develop starter cultures for cucumber fermentations brined with calcium chloride. Subobjective 1b: Identify parameters for long term storage of fermented cucumbers brined with calcium chloride so that freezing damage of the fruits can be prevented and removal of goods from tanks is facilitated during the winter season. Subobjective 1c: Develop an accelerated shelf-life model for fermented cucumber pickles. Objective 2. Determine the factors that maximize survival of probiotic bacteria and retention or production of healthful components in pickled vegetables to facilitate the commercialization of new cucumber pickling methods for delivery of live, probiotic, lactic acid bacteria to consumers. Subobjective 2a: Determine the acid resistance and growth characteristics of probiotic lactic acid bacteria that influence their survival in acidified and fermented cucumbers. Subobjective 2b: Identify suitable methods for the incorporation of probiotic lactic acid bacteria in refrigerated cucumber pickles. Subobjective 2c: Evaluate production and/or retention of bioactive peptides in fermented cucumbers. Objective 3. Enable new commercial methods for process-ready-fermentation or acidification to convert surplus vegetables at grocery stores and farmers' markets into value-added products with enhanced probiotic content. Objective 4. Integrate sweetpotato genotypes intended for commercial processing with their potential for increased levels of bioactive compounds and high quality food products.

Consumer interest in vegetable products with enhanced health benefits will drive future developments in the fermented and acidified vegetable industry. One major limitation for expansion is the generation of chloride waste and excess water use from traditional preservation technologies that rely on high sodium chloride (NaCl) concentrations. Cucumber fermentation in calcium chloride (CaCl2) brine was developed and transferred to commercial processors as an alternative to reduce chlorides in waste waters. Long-term adoption of this reduced NaCl preservation technology requires: a) defining conditions for bulk storage in outdoor tanks to prevent freezing damage in cold climates; b) understanding the microbial ecology of low salt vegetable fermentations so that appropriate starter cultures can be defined; and c) developing a shelf-life model to accurately predict end-use quality. The ability to deliver probiotic bacteria in pickles and to adapt acidification and fermentation technologies to preserve a wide range of surplus vegetables from farms and retail markets will provide new knowledge and technology for processors to engage the growing consumer market interested in healthy eating. For sweetpotatoes, consumer demands for readily available processed products have increased in recent years. Development of new cultivars that are bred for desirable processing characteristics, low acrylamide formation and high bioactive compound content, will benefit sweetpotato processors and farmers and boost the contribution of this nutritious vegetable in the U.S. diet. The proposed research will support developments that broaden the markets for sweetpotatoes, acidified and fermented vegetables and will reduce food and processing wastes.

Progress Report
This new 5 year project was implemented in May 2015 to take the place of the expired project 6070-41000-007-00D. Pilot testing of cucumber fermentation brined with calcium chloride instead of sodium chloride is continued at commercial facilities of pickle companies in the Midwest. The efforts aim to develop methods to prevent freezing damage of the fruits in low salt brines during the winter season. Potential strains of starter culture suitable for low salt fermentations were isolated from various samples collected from geographically distant locations of commercial cucumber fermentations for identification by gene sequencing and characterization of their ability to rapidly decrease the pH in cucumber juice media and inhibit spoilage bacteria. Ten probiotic lactic acid bacteria cultures were characterized to determine suitability for use in an acidified refrigerated cucumber product. Characterization included determination of acid resistance to lactic and acetic acids, which are present in pickled vegetables. The results showed that two of the 10 strains tested, a Lactobacillus acidophilus strain and a Lactobacillus casei strain, may be the most suitable strains for further testing of their long term survival in refrigerated pickles. Progress has been made to adapt the current knowledge of acidification and fermentation of cucumbers and cabbage to a wider range of vegetables to enable commercial development of these technologies for preservation of surplus vegetables at famers’ markets and grocery stores. For sweetpotatoes, over 130 genotypes from the breeding program were tested on browning color of fried chips and formation of acrylamide, a known neurotoxin and potential carcinogen. Samples are being analyzed for contents of sugars, asparagine and acrylamide for correlation among these variables and development of methods using near-infrared spectroscopy to quantify these compounds.