Food Science and Quality Management www.iiste.org ISSN 2222-6088 (Paper) ISSN 2222-0577 (Online) Vol 34, No.X, 2014 1 | Page www.iiste.org Microbiological, chemical and sensory characteristics of yoghurt prepared from blended cow and goat milk Ketut Suriasih 1* , Martini Hartawan 2 , Nyoman Sucipta 3 , Sri Anggreni Lindawati 4 , I.A. Okarini 5 1,2,4,5. Faculty of Animal Husbandry, Udayana University, Denopasar, Indonesia. 3. Faculty of Agricultural Technology, Udayana University, Denpasar, Indonesia. * E-mail of the corresponding author: ketutsuriasih@ymail.com Abstract Chemical composition, microbiological and sensory properties of five different yoghurt prepared from blended cow and goat milk were analyzed. The result of the chemical analysis indicated that, the water percentage, pH of the yoghurt samples were not significantly different (P>0.05). The total acidity of yoghurt samples, however, were significantly different (P<0.05). Microbiological analysis showed that, yoghurt prepared from 75% goat milk had the highest bacterial population of log 8.8692 cfu/g, while yoghurt made of 100% cow milk showed the lowest bacterial load of log 8.3979 cfu/g. The result of sensory analysis showed that, yoghurt made from 100% goat milk obtained the highest score in colour and aroma of 6.9 and 7.0 respectively, though they were not significantly different (P>0.05). Analysis of texture showed that, yoghurt made of blended cow and goat milk were significantly preferable (P<0.05). Taste and overall acceptability of yoghurt made from blended 75% cow and 25% goat milk showed the highest score and were significantly different (P<0.05), compared to yoghurt made from 100% cow milk. Keywords: microbiological, chemical, sensory, yoghurt, cow milk, goat milk 1. Introduction Milk consumption in Indonesia is low (about 12 litres/capita/year), due to low milk production and high price. Only 32 % of that milk, obtained through domestic production, and 68% were imported. Mostly domestic milk production was obtained from cow, though there was some milk obtained from buffalo and goat rising. In Bali, Indonesia, goat population is about 79.817 in 2014 (Ditjennak keswan, 2014), predominated by “Peranakan Etawah (PE)”goat. The PE goat was dual purpose, yield meat and milk. So far, much of the milk obtained from goat rising is not yet consumed due to its unpleasant “goaty” odour. On the other side, goat milk has many benefits to human health, even more than that of cow milk. Goat milk has higher digestibility due to its small fat globule, less allergic reaction ( low αs 1 -casein content), higher calcium and sodium content, more bioavailability of copper, zinc, selenium and iron (Alvarez et al., 2003; Campos et al., 2001; Haenlein, 2004). Processing the milk is an alternative to diversify fresh milk into milk products with better sensory properties, so that increase milk consumption. So far fermented milk product such as yakult and yoghurt are widely marketed in Indonesia and also in Bali. Yoghurt is a fermented milk product which has an acid refreshing taste. Yoghurt obtained from milk or milk product, which undergone lactic acid fermentation by Streptococcus thermophilus and Lactobacillus delbrueckii sbsp. bulgaricus. Streptococcus thermophilus is gram positive, not motile, coccus. These bacteria are homofermentative, facultatively anaerobe, grow optimally at 40-45 o C and pH 6.8. Lactobacillus delbrueckii sbsp. bulgaricus is gram positive, rod, non spore, homofermentative and facultatively anaerobe. This lactobacillus grow optimally at 45-50 o C and pH 6.0 (Pederson, 1971). As starter culture for yoghurt production these bacteria occurred in 1:1 ratio (Vedamuthu, 1982) Reddy et al.(1970) stated that lactic acid bacteria usually used to increase milk quality and to lengthen their shelf life. Furthermore they stated that, lactic acid production by lactic acid bacteria will decrease the pH, so that inhibit growth of spoilage bacteria such as : Clostridium, Staphylococcus, Enterobacteria and psychrophyllic Pseudomonas.