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Title: DIFFERENTIAL GLUCOSE AND FRUCTOSE UTILIZATION DURING CUCUMBER JUICE FERMENTATION

Author
item LU, Z - NCSU
item Fleming, Henry
item McFeeters, Roger

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2000
Publication Date: 1/1/2001
Citation: Lu, Z., Fleming, H.P., McFeeters, R.F. 2001. Differential glucose and fructose utilization during cucumber juice fermentation. J. Food Sci. 66:162-166.

Interpretive Summary: About 40% of the pickling cucumber crop is temporarily preserved by fermentation in brine. The type of microorganisms involved in the fermentation and the compounds they produce are very influential to the quality and value of the brine-stock cucumbers. In this paper we report the rate and extent of fermentation of the natural sugars of cucumbers to lactic acid by a special culture of lactic acid-producing bacterium. The basic knowledge gained on fermentation characteristics of this culture will be useful in our continuing efforts to develop a controlled fermentation procedure for brined cucumbers at minimum salt concentration and waste generation. Farmers, processors and consumers of pickled vegetables may benefit from the improved quality and reduced environmental concerns offered by the controlled fermentation procedure envisioned.

Technical Abstract: Growth, substrate utilization, and product formation by a malolactic- deficient strain of Lactobacillus plantarum were studied in cucumber juice fermentation. Glucose and fructose were degraded simultaneously by the starter culture, but at different rates and to different extents. Glucose depletion was slightly more rapid than fructose during the exponential growth phase, but slower thereafter, and finally stopped. Only 23 mM glucose was utilized by the starter culture. In contrast, fructose degradation continued until all naturally present fructose (36 mM) was exhausted. When cucumber juice broth was supplemented with fructose and/or glucose, the starter culture continued to ferment fructose, but not glucose, until a total of 50 mM fructose was fermented, resulting in an increase in lactic acid production and a decrease in terminal pH. Fructose utilization was not affected by the presence of glucose, but the presence of fructose reduced glucose utilization. These data strongly suggested that different mechanisms regulate the transport and/or the metabolisms of glucose and fructose during cucumber fermentation. The findings have practical relevance in efforts to design a controlled fermentation system to assure complete sugar utilization of vegetables by the lactic starter culture.