Microbial succession in naturally fermented sliced carrots

Natural fermentation of shredded carrots using two types of carrots (red and crimson coloured) was carried out with 3% salt and 4% mustard powder. The viable number of microorganisms was determined at various time intervals on four different types of media viz. De Man Rogosa Sharpe (MRS), Nutrient agar, Yeast extract peptone dextrose agar (YEPDA) and Acetobacter medium. The viable number of cells initially increased on four media and then came to steady state. Some Pseudomonas and Bacillus types of microorganism appeared at the beginning of fermentation. However, these microorganisms did not multiply and survive later on. In crimson coloured carrot, some yeast colonies were also observed but these could not be detected later on. As the fermentation of carrots in brine preceded the amount of total sugars (160μg/ml and 200μg/ml) and reducing sugars (90μg/ml and 96μg/ml) first increased in red and crimson coloured carrots at 3 day and then decreased. The maximum development of 0.03 to 0.9% of total acidity and pH of brine dropped from 6.97 to 3.2 after 15 days of fermentation. From the cultural, morphological and physiological characteristics it was found that three different types of lactic acid bacteria viz. Lactobacillus species, Leuconostoc species and Pediococcus species were present during fermentation. However, fermentation was conducted by heterofermenter Leuconostoc species only as is evident from the production of alcohol and volatile acids. Volatile acids were also produced by the action of Gluconobacter species after 4 day of fermentation. It was concluded that the fermentation of red and crimson coloured carrots is mainly the function of Leuconostoc mesenteroides and Leuconostoc dextronicum, since these microorganisms were present and proliferated throughout the fermentation.