Vol 61, No 3 August 2008 International Journal of Dairy Technology ORIGINAL RESEARCH *Author for correspondence. E-mail: ibakirci@atauni.edu.tr © 2008 Society of Dairy Technology 270 Blackwell Publishing Ltd Oxford, UK IDT International Journal of Dairy Technology 1364-727X 1364-0307 Society of Dairy Technology 2008 XXX ORIGINAL RESEARCH ORIGINAL RESEARCH An investigation of some properties of banana yogurts made with commercial ABT-2 starter culture during storage IHSAN BAKIRCI* and ARZU KAVAZ Department of Food Engineering, Faculty of Agriculture, Atatürk University, 25240 Erzurum, Turkey Five yogurt batches were prepared with banana puree and sugar combinations and ABT-2 (Streptococcus salivarius ssp. thermophilus, Lactobaccilus acidophilus and Bifidobacterium spp.) as starter culture. The addition of fruit influenced (P < 0.05) the syneresis, titratable acidity and pH, whereas the viscosity value, and S. salivarius ssp. thermophilus, L. acidophilus and Bifidobacterium spp. counts were found to be insignificant. Storage time significantly (P < 0.05) affected the syneresis, titratable acidity, pH value, and S. salivarius ssp. thermophilus counts, while the viscosity value and L. acidophilus and Bifidobacterium spp. counts were not affected. The sensory evaluations showed that the sample B was most preferred by panellists. Keywords ABT starter culture, Banana puree, Probiotics, Storage, Yogurt. *Author for correspondence. E-mail:ibakirci@atauni.edu.tr INTRODUCTION Probiotics are usually defined as live microbial food supplements that exert beneficial effects for the host by improving its intestinal microbial balance (Ziemer and Gibson 1998; Saarela et al. 2000; Lourens-Hattingh and Viljoen 2001; Isolauri et al. 2004; Bergamini et al. 2005). Also, fermented milks containing probiotic micro-organisms are generally categorized as functional foods, and along with prebiotics represent the largest segment of the functional foods market worldwide, especially Europe, Japan and Australia (Lucas et al. 2004; Ross et al. 2005). Some health benefits of probiotic foods have been attributed to fermented dairy products, such as reduction in serum cholesterol, alleviation of lactose intolerance, reduction of diarrhoea, preven- tion and suppression of colon cancer and stimula- tion of the immune system (Gilliland et al. 1985; Marteau et al. 1993; Sanders 1994; Perdigon et al. 1995; Dubey and Mistry 1996; Salminen et al. 1998; Kasper 1998; Ouwenhand and Salminen 1998; Saarela et al. 2000; Lourens-Hattingh and Viljoen 2001; Saarela et al. 2002; Itsaranuwat et al. 2003; Donkor et al. 2006). The strains with beneficial properties mostly belong to the genera Bifidobac- terium and Lactobacillus; and the products made with these bacteria are classified as bio-yogurt, containing Lactobacillus acidophilus and Bifidobac- terium bifidum (AB-yogurt) or ABT (L. acidophilus, bifidobacteria, Streptococcus salivarius ssp. ther- mophilus) starter culture (Lourens-Hatting and Viljoen 2001; Isolari et al. 2004). However, to achieve an optimal potential therapeutic effect, the number of these organisms in a probiotic product should meet a suggested minimum of > 10 6 colony- forming units per millilitre (cfu/mL) (Kurmann and Rasic 1991). According to Tamime et al. (1995), regular consumption of 400–500 g/week of AB- yogurt, containing 10 6 viable cells per mL, would provide these numbers. The composition of product, the presence of preservatives as a result of added fruits and nuts, and the availability of growth factors are also reported to affect the growth and viability of yogurt and probiotic bacteria (Dave and Shah 1998). Inulin and fructo-oligosaccharides are probably the most commonly used prebiotics, and are nondigestible carbohydrates used increasingly in food preparations for human consumption (Rao 2001; Holzapfel and Schillinger 2002). Fructo-oligosaccharides are widely found in plants and vegetables, including banana, plum, onion, shallot, chicory and artichoke (L’homme et al. 2003). The aim of this study was to investigate the changes in some physicochemical, microbiological and sensory properties in banana yogurts made with a commercial probiotic culture (ABT-2) during storage. MATERIALS AND METHODS Materials Raw cow’s milk used in the manufacture of yogurt was obtained from the dairy farm of Atatürk University. Skim milk powder (SMP), starch and banana were purchased from local shops in Erzurum. A commercial probiotic starter culture (ABT-2)