Culture of Five Commonly Used Acid-Producing Bacteria on Banana Pulp

A significant fraction of the bananas and plantains produced in the humid tropics are wasted due to rapid spoilage. The use of acid-producing, anaerobic fermentation may be a safe and economical way to preserve the fruit in both large- and small-scale applications. The abilities of five commonly used, acid-producing bacteria to ferment media containing ripe or green bananas were examined. Three homofermentative bacteria, Lactobacillus bulgaricus, Streptococcus thermophilus, and Streptococcus faecalis, typically reduced the pH of a puree of ripe bananas from 4.8 to about 3.5 to 3.6 in 7 days at 37°C. Action on green bananas was similar, but the drop in pH was less pronounced. Very little gas evolved. Lactobacillus fermentum (formerly Lactobacillus fermenti) and Leuconostoc mesenteroides showed active gas evolution and a significant drop in pH. About twice as much gas evolved from ripe banana medium as from green bananas. The fermented purees were spongy, soft solids floating in a clear liquor. The color was medium to light creamy brown, and the odor was pleasant. Fermented products stored at room temperature retained good appearance and aroma throughout a 1-month storage test.