Trial productions of freeze-dried Lactobacillus plantarum culture using dairy by-products as cryoprotectants: Viability and characterization of cultures

Abstract

This study is a research on the utilization of dairy industry by-products in the practical production and long-term preservation of industrial microbial cultures. Accordingly, lyophilized cultures were obtained by freeze-drying of Lactobacillus plantarum bacteria in large quantities and for a constant period of time in skimmed milk-based medium containing 5% acid casein, rennet casein, whey and demineralized whey. The cryoprotectants did not have significant protection against freeze-drying process, moreover, the use of rennet casein significantly reduced viability. The efficiency of the preservatives in preserving the viability during storage was very successful compared to the control culture. Casein-enriched cultures had high water activity and moisture, but high viability was maintained during storage. The powder morphologies of the cultures were differentiated by the use of different cryoprotectants. Particle sizes of the cultures were parallel to the moisture content. Particle size and distribution increased with storage. By thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis, it was determined that the addition of casein protein increased the degradation temperature of the cultures. The production of freeze-dried cultures became difficult with the use of casein. However, it was generally concluded that the protective properties of skimmed milk used for the preservation of L. plantarum could be improved by the addition of dairy by-products as a protective agent.