Background. Fiber from fruit, vegetables and other sources of fiber can increase gut microbiota diversity and show anti-inflammatory activity. The use of fiber in the manufacture of probiotic fermented milk has excellent potential, as it can offer several benefits for both consumers and producers. In addition to its well-known physiological benefits, dietary fiber may reduce the risk of diseases of civilization. Consumers expect that current foods are health-promoting. Consumer awareness is increasing through an expanding variety of products and advertising campaigns favoring health-promoting foods, a trend that food manufacturers are also taking advantage of. The aim of the study was to determine the effect of psyllium fiber and chokeberry fiber addition in combination with probiotic cultures Bifidobacterium animalis ssp. lactis BB-12 and Lacticaseibacillus casei 431 on the quality of fermented milk. To investigate the effect of fiber on fermented milk quality, acidity, texture properties, syneresis and colorcolor were measured, moreover, an organoleptic evaluation and microbiological analysis were performed.
Results and conclusion. Natural additives such as chokeberry fiber and psyllium fiber can be used in the production of milk fermented by Bifidobacterium BB-12 and L.casei. Psyllium fiber can be recommended for its syneresis-reducing properties. Whereas chokeberry fiber, due to its high polyphenol content, can be used as a natural colorcolorant and taste-enhancing additive. Adding fiber as chokeberry or psyllium positively stimulated the growth and survival of Bifidobacterium BB-12 and L. casei bacteria during storage. The hardness of the milk gel fermented by Bifidobacterium BB-12 or L. casei was significantly improved by adding psyllium fiber, increasing it by as much as about 2.5 N, and this trend was also maintained after 28 days of storage.  Studies on using various fibers in fermented milk production should be continued to determine their health-promoting and technological potential.