Yogurt Production

Yoghurt is a cultured dairy product which is made from the mixing of standardized milk with the activity of a symbiotic blend of Streptoccoccus thermophilus and Lactobacillus delbruekii subsp.Bulgaris (LB) cultures. Usually, the making of yoghurt involved the pretreatment of milk follow by the homogenization, heat treatment, cooling to incubation temperature, inoculation with starter, fermentation , cooling, post fermentation treatment, chilling and lastly packaging for commercial yogurt production. In this experiment, the making of yoghurt followed the batch process. The 1000ml of UHT milk is mixed with some milk powder to increase the content of milk solid non fat in the milk in order to improve the texture with the help of protein functionality. The equipment used for mixing is sterilized so that the contamination of products with phage and spoilage microbes is reduced to minimum. The mixture of milk is then double boil in boiling water to provide a sterile environment for the starter culture to grow while denature whey protein to from a stable gel that disallow the occurrence of syneresis. The heating of the milk is also done to break down the milk constituents to provide nutrients and reducing condition for the starter culture. One of the constituent is Sulphydral compounds which are the nutrients and reducing condition for this starter culture. In addition, heating process also remove air from the medium to aid the anaerobic process that is going to occur during fermentation. When the heated milk reach the desire temperature, it is cooled down in ice water bath. Then two spoon of fresh yoghurt which contained both Streptoccoccus thermophilus and Lactobacillus delbruekii subsp.Bulgaris (LB) cultures are added to the cooled milk. The mixture undergoes fermentation when placed in the incubator.
Based on the result obtained from this experiment, the pH value of the milk at 0 hour before incubation is pH 6.08 which near neutral while the result for the mixture