The influence of the storage time of vegetables - raw materials, the influence of fermentation temperature and the influence of the glucose addition about the lactic acid fermentation unfolding has been studied. Fresh carrots and carrots stored five months were pressed to raw juice and heat-treated at 70 degrees C for 20 minutes in the aim of destroy the undesirable microorganisms. Carrot juices were inoculated with lactic acid bacteria isolated from epiphytic microbiota at the concentration of 4x105 UFC/ml and fermented in a thermostat for 96 hours. During the fermentation the following analytical parameters were established: reducing sugars, total acidity, pH, amino acids content, nitrites content, ascorbic acid content. During fermentation the pH of carrot juices decreases from 6,15 to 3,99, while the total acidity increases from 0,06 to 1,62% (as lactic acid). Less than 25% of the initial content of ascorbic acid rests in the juices after 96 hours of fermentation. The amino acids content of juices, expressed as g N2/100g, increase with a middle of 50% in 96 hours, due of the proteins decomposition. The pre-digestion of these compounds improve the nutritional quality of the lactofermented juices. We found that the glucose supplement hasn’t a significant influence about the lactic acid accumulation. Also, at the end of the period of study, we found that the substratum metabolization was difficult in the sample with 1% glucose initial added. The quality of the raw materials, especially concerning the sugars content and the total acidity at the beginning of the fermentation process is important because a rapidly increase of acidity minimizes the influence of spoilage bacteria. To proceed from the results of the sensory analysis and the results of the chemical analysis we recommend stopping the fermentation of these juices after 72 hours.
Amino acids analysis during lactic acid fermentation by single strain cultures of lactobacilli and mixed culture starter made from them