Robustness-by-design for Probiotic Foods: Mechanisms, Non-thermal Stress Conditioning, and Engineered Microenvironments.

The incorporation of probiotic dairy and non-dairy foods is often limited by the loss of bioactivity caused by stresses to which microorganisms are subjected during processing, storage, and digestion. This frequently results in probiotic counts below the minimum level required to exert their probiotic function (10⁷ CFU/g) at the time of consumption. Maintaining cell viability remains a challenge for probiotic food manufacturers. The omics technologies have enabled the identification of stress response pathways in microorganisms; however, their application to the design of reproducible and scalable processes remains limited. This review integrates microbial stress physiology with bioprocesses and food matrix engineering to support the design of robust probiotic products. Biological mechanisms underlying increased tolerance to environmental stresses are analyzed and preadaptation strategies based on sublethal exposure to heat, acid and bile, ultrasound, pulsed electric fields, and high-pressure processing are discussed. Encapsulation systems are considered protective structures that reduce stress during food processing, storage, and digestion. To enhance the bioactivity of probiotics, a robustness-by-design approach is proposed. This begins with selecting the probiotic strain and the food. After selecting the probiotic strain, it is subjected to sublethal stress treatments to induce adaptive responses. The conditioned probiotic is incorporated into the food. The proposed scheme integrates survival kinetics and biomarkers to support process design. Biosafety aspects associated with sublethal stress are considered critical for the development of stable and safe probiotic foods on an industrial scale.