Evaluation and selection of protective agent combinations for freeze-drying preservation of an autochthonous meat starter culture

Abstract

Freeze-drying is widely used to preserve lactic acid bacteria starter cultures; however, dehydration and storage stresses may reduce cell viability and functionality. This study evaluated different protective agents for freeze-dried Latilactobacillus sakei subsp. sakei ACU-2, an autochthonous starter culture for fermented meat products. Dairy proteins, sugars, amino acids, and plant-derived matrices were screened based on survival after freeze-drying, water activity, storage stability, and retention of acidifying activity after 180 days at 4 °C and 25 °C. Dairy-based matrices provided the highest survival and stability, although acidifying activity decreased at 25 °C. Principal component analysis was applied to integrate the evaluated variables and select combinations of protectants with distinct functional behaviors. Binary formulations showed minor differences at 4 °C but clear effects at 25 °C, indicating greater relevance under thermal stress. The skim milk–glutamate formulation showed the best overall performance, maintaining higher survival, storage stability, and acidifying activity at 25 °C.