Journal of the Science of Food and Agriculture J Sci Food Agric 85:2134–2141 (2005) DOI: 10.1002/jsfa.2223 Application of pure and mixed probiotic lactic acid bacteria and yeast cultures for oat fermentation Angel Angelov, 1∗ Velitchka Gotcheva, 1 Tsonka Hristozova 2 and Stoyanka Gargova 1 1 Department of Biotechnology, University of Food Technologies, 26 Maritza Blvd, 4002 Plovdiv, Bulgaria 2 Institute of Microbiology, Bulgarian Academy of Sciences, 26 Maritza Blvd, 4002 Plovdiv, Bulgaria Abstract: Fermentation of a prebiotic containing oat substrate with probiotic lactic acid bacteria and yeast strains is an intriguing approach for the development of new synbiotic functional products. This approach was applied in the present work by using pure and mixed microbial cultures to ferment a heat-treated oat mash. Results show that the strains studied were appropriate for oat fermentation and the process could be completed for 6–10 h depending on the strain. The viable cell counts achieved within this time were above the required levels of 10 6 –10 7 cfu ml -1 for probiotic products. Both single lactic acid bacteria strains and mixed cultures of the same strains with yeast were found suitable for oat fermentation. However, the pure LAB cultures attributed better flavour and shelf life of the oat drinks. The content of the prebiotic oat component beta-glucan remained within 0.30–0.36% during fermentation and storage of the drinks obtained with each of the strains used. Thus, these products would contribute diet with the valuable functional properties of beta-glucan. Also, the viability of pure and mixed cultures in the oat products was good: levels of cell counts remained above the required numbers for probiotic products throughout the estimated shelf-life period.  2005 Society of Chemical Industry Keywords: oat fermentation; probiotics; beta-glucan; lactic acid bacteria; yeasts Abbreviations LAB lactic acid bacteria GIT gastro-intestinal tract TA titratable acidity LDL low-density lipoprotein cfu colony forming units v/v volume/volume w/v weight/volume L Lactobacillus C Candida INTRODUCTION The application of probiotic microbial strains for fermentation of cereal substrates is a rational approach for the development of functional foods, which, as part of the daily food intake, contribute to enhancing and maintaining consumers’ health and to improv- ing their quality of life. The beneficial effects of foods containing probiotic bacteria on human health include improved food digestibility and bioavail- ability of vitamins and minerals, improved lactose metabolism, control of gastro-intestinal infections, reduction of some liver and kidney catabolic products, cancer suppression, reduction of serum cholesterol levels and immune stimulation. 1–6 For the efficacy of probiotic foods, high levels of viable microor- ganisms are recommended: 10 6 –10 7 cfu ml −1 (g). Technological challenges associated with the intro- duction and maintenance of high numbers of probiotic microorganisms in foods include the form of the probiotic inoculant, ability of the probiotic culture to retain viability in the environment of the food matrix, and maintenance of the probiotic charac- teristics in the food product through the time of consumption. 7 Given that most probiotics worldwide are applied in dairy products, many of them are unsuitable to grow in cereal-based media. A number of studies have shown that the survival of probiotic strains under the gastro- intestinal conditions is strongly effected by the nature of the food carrier: its buffering capacity, pH, chemical and physical characteristics. 8,9 Cereals have proved to be appropriate substrates for lactic acid fermentation, and the use of probiotic strains as starter cultures could result into probiotic products, which are suitable for vegetarians, avoid lactose-intolerance problems and are a ‘tasty’ contribution to the functional food family. ∗ Correspondence to: Associate Professor Dr Angel Angelov, Department of Biotechnology, University of Food Technologies, 26 Maritza Blvd, 4002 Plovdiv, Bulgaria E-mail: angelov@uft-bio.com Contract/grant sponsor: Bulgarian Ministry of Education and Science; contract/grant number: CC 1004/2000 (Received 13 July 2004; revised version received 7 December 2004; accepted 27 January 2005) Published online 7 June 2005  2005 Society of Chemical Industry. J Sci Food Agric 0022–5142/2005/$30.00 2134