Production of Kefir and Kefir-like Beverages: Fundamental Aspects, Advances, and Future Challenges

Nowadays, consumer demand for functional foods with health benefits has grown significantly. In response to this trend, a variety of potentially probiotic foods have been developed—most notably kefir and kefir-like beverages, which are highly appreciated for their tangy flavor and health-promoting properties. Traditionally, kefir is made by fermenting cow’s milk with milk kefir grains, although milk from other animals—such as goats, ewes, buffalo, camels, and mares—is also used. Additionally, non-dairy versions are made by fermenting plant-based milks (such as coconut, almond, soy, rice, and oat) with the same type of grains, or by fermenting fruit and vegetable juices (e.g., apple, carrot, fennel, grape, tomato, prickly pear, onion, kiwifruit, strawberry, quince, pomegranate) with water kefir grains. Despite their popularity, many aspects of kefir production remain poorly understood. These include alternative production methods beyond traditional batch fermentation, kinetic studies of the process, and the influence of key cultivation variables—such as temperature, initial pH, and the type and concentration of nutrients—on biomass production and fermentation metabolites. A deeper understanding of the fermentation process can enable the production of kefir beverages tailored to meet diverse consumer preferences.