Shelf-life characteristics of Bambara groundnut (Vigna subterranea (L.)Verdc) probiotic beverage

Abstract

Two Bambara groundnut probiotic beverages (BGNPB), fermented with (1) Lactobacillus bulgaricus and (2) Lactobacillus bulgaricus and Lactobacillus plantarum were assessed for their shelf-life characteristics. During the shelf-life study, sampling of the BGNPB was done at two-days interval for 28 days for pH, total titratable acidity (TTA), microbial load and colour. Shelf-life data was modelled with Mitscherlich’s law of diminishing returns model and used to estimate the shelf-life of the BGNPB. After the 28 days of the storage pH was pH 4.30 and pH 4.25 at 5°C; pH 3.94 and pH 3.72 at 15°C and pH 3.78 and pH 3.45 at 25°C for (1) L. bulgaricus and (2) L. bulgaricus and L. plantarum, respectively. TTA was 1.8% and 2.0% at 5°C; 2.0% and 2.2% at 15°C while at 25°C it was 2.6% and 2.6% for (1) L. bulgaricus and (2) L. bulgaricus and L. plantarum, respectively. Microbial load and colour were significantly affected by the storage temperatures and time. Shelf-life was estimated as 28 days (right censored) for both BGNPB stored at 5°C. The shelf-life of the BGNPB under refrigeration (5°C) was longer when compared to the dairy counterparts with shelf-life of 14 days at 4°C. Therefore, the longer shelf-life of BGNPB makes the beverage a suitable vehicle to transport probiotics to humans.