Viability of encapsulated and non-encapsulated lactic acid bacteria under dairy manufacturing conditions

The primary objective of this research was to examine the survival of five cultures of encapsulated lactic acid bacteria (LAB) ( Lactobacillus plantarum ATCC14917, Lactobacillus casei NCAIM B01137, Lactobacillus rhamnosus ISO7, Bifidobacterium breve ISO8, and Leuconostoc mesenteroides subsp. mesenteroides DSM 20343) under dairy manufacturing conditions. Kappa (k)-carrageenan and sodium alginate (Na-alginate) were utilized to formulate the capsules. The LAB encapsulated in alginate and carrageenan demonstrated higher resistance to scalding temperatures compared to free cells. All tested LAB strains-maintained counts within or above the recommended range needed for probiotic effect (≥ 106 CFU/ml) at various scalding temperatures. However, all tested LAB strains exhibited a significant loss in viability when exposed to high temperatures; at 72°C, the bacterial count was reduced by five Log CFU g ^-1 . Both non-encapsulated and encapsulated cells decreased by six to seven Log CFU g ^-1 at 85°C. The LAB encapsulated in alginate or carrageenan showed greater heat resistance than non-encapsulated cells. The survival of both non-encapsulated and encapsulated cells at room temperature (25°C) ranged from 2.30 to 10.59 Log CFU g ^-1 after one day. A decline in viability was noted after five days of incubation, continuing until the end of the storage period. At refrigerator temperature (~ 5°C), both non-encapsulated and encapsulated cells revealed lower counts by the end of the storage period. The cell load within all encapsulating agents decreased throughout the storage period at -10°C. The pH values of all LAB strains in skimmed milk decreased during the incubation period. The scanning electron microscope (SEM) images of the microcapsules loaded with Lb. casei plus Na-alginate were solid and regular in shape of Na-alginate. While the produced k-carrageenan capsules were irregular and soft.