Optimisation of bambara groundnut water extract and skim milk composition as cryoprotectant for increasing cell viability of Lactobacillus spp. using response surface methodology

Abstract

Summary Four legume water extracts, that is bambara groundnut, soya bean, red kidney bean and black bean as well as skim milk, were examined for their effectiveness in protecting Lactobacillus rhamnosus GG and Lactobacillus fermentum SK5 during the freeze‐drying and storage. Bambara groundnut water extract (BGWE) showed promising cryoprotective activity that was comparable to skim milk. BGWE and skim milk at 2–10% w/v and 5–20% w/v individually produced survival rates for both strains of 87–88%. To further optimise the synergistic cryoprotective medium, response surface methodology was employed. The optimal combination was 4.93% w/v BGWE and 11.68% w/v skim milk for L. rhamnosus GG and 5.17% w/v BGWE and 11.36% w/v skim milk for L. fermentum SK5 with survival rates of 95.17% and 94.36%, respectively. The storage life of freeze‐dried cells of both probiotics at 4 °C and 30 °C for 6 months was markedly improved when they were produced with these optimal combinations.

Short communication: Effect of different kefir grains on the attributes of kefir produced with milk from Costa Rica

“…Bacteria had a higher survival rate after freezing compared with yeasts. This could have been because the recovery of bacteria cells when milk is used as a means of preservation in freezing is more significant, because milk has specific characteristics that make it an efficient cryoprotectant (the substance that is used to protect the cell against freezing damage ;Kaewiad et al, 2016). Other reports in the literature have also indicated that lactic acid bacteria survive the freezing process better than fungi and yeasts; although the latter can survive freezing, the survival rate is much lower than that observed for bacteria (Bolla et al, 2011).…”