DEVELOPMENT AND VALIDATION OF A PREDICTIVE MODEL FOR Bacillus licheniformis GROWTH IN PLANT-BASED MILK ALTERNATIVES

In the past few years, the consumers' demand for plant-based milk alternatives (PBMA) has increased and the offer includes today's various innovative drinks made from nuts, cereals and legumes, such as almond, soy, pistachio, oat and pea. Considering that soil constitutes the environmental niche of various facultative thermophilic spore-forming bacteria, these raw materials might be contaminated with Bacillus licheniformis spores. PBMA are usually sterilized by ultra-high temperature (UHT) treatment primarily designed to eliminate spores of Clostridium botulinum. This process is insufficient in eliminating spores of thermophilic bacteria which are extremely heat-resistant. B. licheniformis is included in a group of endospores which are considered as psychrotrophic thermophilic sporoformers (Eijlander et al., 2019). Therefore, the microbial stability of PBMA may be affected by the presence of B. licheniformis spores which survive the heat treatment, evolve in vegetative cells and multiply during storage. Hence, the aim of this study was to assess the effect of temperature increase on the spoilage of non-refrigerated PBMA and re-evaluate their microbiological stability. For this reason, a model for Bacillus licheniformis growth as a function of temperature and pH was developed. In this model, cardinal temperature and pH values, along with the maximum specific growth rates of Bacillus licheniformis DSM 13 were estimated, by studying the temperature and pH ranges between 15 and 57. and 4.8 and 7, respectively. The model was validated, under isothermal conditions, in a pea milk alternative, as a representative of non- refrigerated PBMA. This study is of a great importance since the developed model will contribute to the assessment of the microbiological stability of PBMA, under different temperature scenarios.