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Chapter 36 : Fermented Vegetables
Category: Applied and Industrial Microbiology; Food Microbiology
Vegetable fermentation by lactic acid bacteria (LAB) in a salt brine began as a way to preserve foods for out-of-season use and for long journeys, especially by sea. Prior to the 1920s, research in the United States on pickled vegetables was primarily focused on product surveys and descriptions of brining methods. Reports on the microbiology and biochemistry of vegetable fermentations appeared in the literature between 1918 and 1920. Current research on pickled vegetables includes the genomics of LAB, mathematical modeling of bacterial growth and competition, the molecular ecology of vegetable fermentations, closed-tank fermentation technology to reduce salt waste, the use of clays to filter brines for recycling, sensory perception of pickled vegetable products, and the safety of acidified foods. There is continuing research interest in fermentation and storage of vegetables, particularly cucumbers, with reduced salt. The most notable effect of fermentation on cucumber volatiles was the inhibition of production of (E, Z)-2,6-nonadienal and 2-nonenal, the two most important odor impact compounds in fresh cucumbers. Among Lactococcus lactis genome sequences are those belonging to the predominant bacteria present in fermented vegetables, Lactobacillus plantarum, Lactobacillus mesenteroides, Pediococcus pentosaceus, and Lactobacillus brevis. As expected, none of the predominant LAB in fermented vegetables have predicted genes for a complete citric acid cycle. The development of low-salt fermentations and storage of fermented vegetables for commercial use present significant technological hurdles, including the potential need for starter cultures (and the impact of bacteriophage on starter cultures) and for new product handling equipment.
Distribution of ORFs among COG functional categories a
Pyruvic-acid-dissipating enzymes present in the predominant LAB in fermented vegetables a