Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Traditionally, dairy products are the major and most popular probiotic carriers. At present, there is a growing demand for non-dairy probiotic products. Both fermented and non-fermented non-dairy plant-based food products are becoming highly appealing to both dairy and non-dairy consumers worldwide. Non-dairy plant-based food matrices such as fruits, vegetables, plant-based milk, cereals, and legumes have been used successfully in producing probiotic products with the minimum recommended viable probiotic numbers at the time of consumption. However, due to the exclusion of dairy, whether these food matrices can enhance the functional properties of probiotics such as gastrointestinal survival and immune-enhancing effects needs a thorough investigation. Hence, this review focuses on some of the popular non-dairy plant-based probiotic food products and their microbiological quality characteristics in terms of maintaining probiotic viability during product storage. Their gastrointestinal tolerance in these products, other functional properties, and product qualities have also been briefly discussed.

Maintaining the overall quality and shelf life of plant-based food and beverages is particularly important yet challenging to the food industry. Demand for natural preservation techniques has increased with the rising concerns over food safety and consumer awareness, e.g., health consciousness and food trends such as veganism and the demand for clean, labelled foods. Thus, a technique such as biopreservation has the potential to enhance food safety while fostering the quality, originality and naturalness of food. The application of probiotic microorganisms to foods and beverages provides various health benefits in addition to improved shelf life, stability and microbial safety of the food. The provision of probiotics is known to deliver various health benefits for the host’s gut health. Therefore, this review aims to investigate the importance of biopreservation and the role of probiotics in the food industry. An attempt was made to explore the various possibilities of shelf-life enhancement through the use of probiotic microorganisms as biopreservatives. Noticeable improvements in the shelf life of plant-based foods and beverages were observed due to the antimicrobial effects exerted by probiotics and potential probiotic strains which make them useful alternatives to artificially synthesized chemical preservatives.

The angiotensin-I converting enzyme (ACE) inhibitory activity of the milk fermented with Lactococcus lactis subsp. lactis NBRC 12007 and Saccharomyces cerevisiae K7 in monoculture and co-culture was evaluated. Bovine full-fat milk was fermented with each strain in monoculture and co-culture at 30 ºC for 72 h, and the in vitro ACE inhibitory activity (%) of each milk sample was determined by a fluorogenic assay using H-(2)Abz-Acp(6)-Ala-Phe(4-NO 2)-Leu-OH as the substrate. The ACE inhibitory percentages of the milk samples fermented with L. lactis subsp. lactis NBRC 12007 and S. cerevisiae K7 monocultures and the co-culture was 33, 27 and 25 %, respectively, which varied significantly (p < 0.05). Each milk sample was fractionated by semi-preparative HPLC analysis and the ACE inhibitory activity (%) of each fraction was determined using the same substrate, which varied from 20-47 %, 16-37 % and 16-31 % in the milk fermented with L. lactis subsp. lactis NBRC 12007, S. cerevisiae K7 and the co-culture, respectively. The highest ACE-inhibitory activity (47 %) was observed in fraction-2 of the milk fermented with L. lactis subsp. lactis NBRC 12007. The results concluded that the two strains tested were able to hydrolyze milk proteins into ACE-inhibitory peptides in order to produce fermented milk products with ACE-inhibitory activity, both in monoculture and co-culture. Therefore, it can be suggested that these strains can be successfully utilized in the dairy industry in manufacturing fermented milk products with ACE-inhibitory activity as a dietary supplement and/or as an alternative approach for antihypertensive medication.