Probiotics viability in frozen food products

Improving gastrointestinal flora with probiotics is a promising method of treating and preventing many diseases. However, in food industry, introduction of probiotics is limited by the shelf life of products, as well as by the reduction of bacterial viability during storage. Thus, introduction of probiotics into foods to be frozen is a promising method to extend the shelf life of probiotic products. However, the storage of living cells in frozen products involves their damage during freezing and subsequent storage at temperatures below 0 °C. Therefore, some technological solutions are required to protect probiotics during storage at sub-zero. Today, encapsulation, addition of cryoprotectants and prebiotics, as well as adaptation of microorganisms are widely used techniques of protecting probiotics. The combination of various protection methods is a promising way to improve the viability of probiotics during storage. Studies aimed at investigating various combinations of hurdle methods and their effect on bacterial survival are of great interest. This review compiles the most common methods of preserving probiotics in frozen foods, describing their effects, variety of approaches, and effectiveness. The main mechanisms of bacterial cell damage by freezing are described. Further trends in probiotic protection in frozen foods are also discussed.