Assessment of the applicability of coconut and skim milk powder as a carrier for lactic acid bacteria on their performance during production of Ting

Abstract

The demand for dried starter cultures that are specific to indigenous fermented food products is increasing. In most cases, skim milk (SM) powder is used as a cryoprotectant for microbial cell protection during the preparation of starter cultures. However, the extent of cell protection during freeze-drying and the fermentation efficacy of dried cultures are dependent on the type of microbial strain and carrier media, hence the need to investigate the protective effects of alternative carrier media. This study evaluated the fermentation potential of lactic acid bacteria (LAB) preserved in coconut (CCN) powder and SM powder during ting (traditional fermented sorghum) production. Ting was fermented with single and mixed strains of Lactobacillus plantarum and Lactobacillus brevis. The pH, total titratable acidity (TTA), functional groups (Fourier transform infrared spectroscopy [FTIR]), microbial quality, and consumer acceptability were monitored during fermentation. Ting prepared with LAB strains preserved in SM had a more rapid reduction (p > 0.05) in pH and lower final pH than ting prepared with LAB preserved in CCN. Mixed LAB strains showed a rapid reduction in pH of ting compared to single LAB strains and ting prepared with spontaneous fermentation. The highest TTA (3.57%) was observed with mixed LAB after 48 h on both SM and CCN ting. FTIR showed similar functional groups corresponding to O-H and phenolic compounds for both SM and CCN ting. The highest increase in LAB counts (up to 10 log CFU/mL) occurred in ting prepared with mixed strains of both CCN and SM, while the least increase occurred with spontaneously fermented ting. Enterobacteriaceae, yeasts, and molds were not detected in all the fermented samples. With consumer acceptability, CCN ting was the most preferred sample with the highest overall score (6.95), followed by the SM ting sample (5.67). In conclusion, this work indicates that the LAB strains preserved in CCN result in comparable fermentation performance to that of SM and produce ting that is preferred by consumers. Therefore, CCN should be considered as a carrier medium for the development of ting starter cultures.