Technological strategies ensuring the safe arrival of beneficial microorganisms to the gut: From food processing and storage to their passage through the gastrointestinal tract.

The development of functional foods containing probiotics has experienced a great boom in the last years, reflected by the increasing number of novel products available at the market, as well as by the well-documented extensive research, going beyond the traditional fermented dairy foods. However, to safe arrive to their target, the gut, microorganisms contained in food products have to overcome different barriers, both technological and physiological. Food processing might cause different types of damages on beneficial bacteria, which finally lead to a decrease of viability. In addition, once ingested, and before arriving to the gut, microorganisms are exposed to other food constituents, low pH and digestive juices, all of them constituting detrimental environments that can decrease their viability. For this reason, this review offers an updated state of the art on the microorganisms' response to the factors affecting their survival during drying techniques, storage and rehydration. Current strategies to overcome detrimental processing effects on bacterial viability are also reviewed, as well as the effect of food matrices on bacterial protection during food manufacturing and storage. The effect of probiotic microorganisms on the gut, and in particular on the intestinal microbiota is an issue of increasing interest in the last decades, and thus, special emphasis was put it on.