Date of Graduation

12-2011

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Ron Buescher

Abstract

Lactic acid bacteria (LAB) are important industrial microorganisms involved in fermentation of food and beverage products. The strict fermentative growth of LAB has complex requirements of various nutrients including amino acids, vitamins and minerals. Information about the effect of these nutrients on the growth of LAB in cucumber fermentation is not readily available. It is evident, from previous research that certain nutrients like; leucine, isoleucine, tryptophan, valine, biotin, nicotinic acid, pantothenic acid, riboflavin, manganese and magnesium are beneficial for LAB growth, but are not provided in sufficient quantities by the cucumber in the brine. The objective of this study was to determine the efficacy of (1) the above mentioned nutrients (2) the most effective concentrations of biotin, isoleucine and valine alone and (3) combination of biotin, isoleucine and valine with cucumber fermentation brine, on the production of LAB and lactic acid in brine. The yield of LAB was determined from microscopical counts using a hemacytometer, lactic acid concentration, dry weight and the final sugar concentration in the brine was determined. The first three trials established that biotin, valine and isoleucine improved LAB growth. Efficacy of five different concentrations each of biotin, valine and isoleucine in cucumber juice was determined in trial four. Biotin and isoleucine treatments at three different concentrations, in trial four, were equally effective on LAB growth; hence the lowest concentrations of 614 nM of biotin and 0.76 mM of isoleucine were selected; whereas valine treatments showed a relative small increase in the LAB growth with increase in concentration and 1.17 mM of valine was the most effective of all the valine treatments. These optimized concentrations of nutrients were used in trial five, in different combinations. Of these, biotin and valine treatments when used individually or in combination showed a significant increase in LAB growth and the rate of production and concentration of lactic acid in the brine. These results indicated that the addition of biotin and valine potentially increased the number of LAB. Additional research is required using whole cucumbers to develop effective treatments.

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