Effect of Varying Sources of Milk, Dairy fat levels and stabilizers on physico-chemical characteristics and sensory attributes of Laban (Stirred Yoghurt)

Abstract

The demand of fermented dairy products is gradually increasing in Pakistan. Laban (stirred yoghurt) is a fermented dairy product with nutritional and therapeutic prospects. There is limited data available in context of Pakistan with reference to physical and chemical characteristics of Laban. There is a dire need to optimize the milk type, dairy fat content and use of cost-effective stabilizer for better formulation of Laban at industrial level with its economical acceptability in Pakistan. Optimization of various sources of milk with variable fat levels and use of different stabilizer may improve the physico-chemical quality and overall acceptability of Laban. In first experiment, Whole milk of buffalo, cow and cow buffalo milk blend (50:50) used for the preparation of Laban. After the compositional analysis of whole milk, it was preheated at 65 °C for stabilizer addition and then pasteurized at 85°C with five minutes holding. Pasteurized milk cooled down at 44°C for starter culture inoculation and incubated at same temperature for fermentation in incubator until the curd is formed at 4.6 pH. The prepared yoghurt curd blended to convert it into Laban and stored at 4°C in 250 ml PET bottles during shelf life of 21 days for analysis. Prepared Laban samples analyzed for physico-chemical and sensorial analysis during storage. Fat%, protein%, total solids%, pH, acidity, syneresis, total plate count, coliform count, time of fermentation, viscosity of Laban and sensory characteristics studied at 0, 7, 14 and 21 days of shelf life. In second experiment, milk of different sources (buffalo, cow and cow buffalo blend (50:50) standardized for milk fat contents at 3.5 and 1.5% using cream separator. Standardized milk pasteurized and then incubated with starter culture for fermentation till 4.6 pH. Yoghurt curd broken down into Laban and stored at 4 °C in 250 ml PET up-to 21 days. Prepared Laban with variable milk fat contents analyzed for physico-chemical and sensorial characteristics. Fat %, protein%, total solids %, pH, acidity, syneresis, total plate count, coliform count and sensory characteristics studied at 0, 7, 14 and 21 days of storage intervals. In third experiment, effect of gelatin and carboxy methyl cellulose on physico-chemical and sensory characteristics of Laban were studied. Milk from different sources standardized at 3.5% milk fat for preparation of Laban. Prepared Laban samples stored at 4°C for 21 days. Fat, protein, total solids, pH, acidity, syneresis, total plate count, coliform count and sensory characteristics studied at 0, 7, 14 and 21 days of shelf life. Data analysed using two-way and three-way ANOVA, with PROC GLM through SAS 9.1 software (SAS Institute, Inc. North Carolina USA). Means compared by Duncan’s multiple range Test. P value less than 0.05 considered significant. Stirred yoghurt made from different milk sources showed that buffalo milk contained higher TS contents as compared to cattle and mixed milk, so buffalo milk made stirred yoghurt showed higher acceptability to consumers. it showed less synersis, higher viscosity, higher TPC. While, cattle milk showed less consumer acceptability, higher synersis, less fat and less total solids. But the mixed milk showed better results as compared to the cattle milk. In the case of various level of milk fat, the data showed that higher fat content which was 3.5%, cause to increased total solids contents and makes it more appealing for consumers. In the third case different stabilizers were used to access the textural and sensorial attributes of yoghurt, it revealed that Gelatin showed higher consistency as compared to CMC, while both decrease the fermentation and increase the fermentation time. This study would help to develop cost effective and economical Laban technological processes for dairy industries and small-scale dairy entrepreneurs in Pakistan. This could also assist in improvising and enhancing sensorial attributes and overall acceptability of Laban in Pakistan. The optimization of these controlled processing procedures pave way for better marketability and overall acceptability of Laban under prevailing storage conditions of Pakistan.