An improved ionic gelation method to encapsulate Lactobacillus spp. bacteria: Protection, survival and stability study

Abstract

A high number of viable microorganisms are required to be present in a probiotic formula in order to get its beneficial effects. So, the main objective in this work is to protect probiotic bacteria during its incorporation into a formula and its storage. A modified emulsification – internal gelation procedure has been carried out to encapsulate a lactobacillus strain by reducing the water content traditionally used to obtain the emulsification, which is detrimental to bacterial survival, and replacing it with MRS broth previously innoculated with bacteria. As a result, two different microparticles MM (40 ml bacteria broth/no water) and WMM (20 ml bacteria broth/20 ml water) were obtained. Bacteria encapsulation yields for both microparticles were similar, 100.66 ± 0.58% and 101.73 ± 4.12% respectively. The process of lyophilisation improved the survival of bacteria in each microparticle after 120 days at 4 °C. However, there was no survival for non-encapsulated lactobacillus after this time. Due to its highest survival under these storage conditions, freeze-dried MM microparticles were selected as optimal to study the bacteria survival under several temperatures of storage (−20 °C, 4 °C, 25 °C) and bacteria survival in acid. Results showed that each temperature assured a 100% of bacteria survival after 150 days of storage. Furthermore, MM microparticles conferred bacteria protection in acid pH (1.8–2) with a decrease of 5 log CFU/g beyond 60 min compared to non-encapsulated lactobacillus which did not survive. MM microparticles morphology and size distribution were also studied and discussed.