Quality evaluation of yogurts produced commercially In Lagos, Nigeria

Yogurt of the natural-stirred and pineapple-stirred varieties manufactured commercially in Lagos, Nigeria were analyzed to evaluate the nutritional quality of the fresh and stored product. The carbohydrate and protein contents were higher in the pineapple than in natural yogurt with an average percent content of 12.7 and 1.2 compared to 7.0 and 0.9 respectively. The fat content was the same, about 1.0 percent of each type. These values decreased with time during storage and the decrease was more rapid at 30oC than at 10oC. Natural yogurt was more acidic with an average pH of 3.8 and 3.0% lactic acid content compared to values of 4.2 and 2.4% respectively for pineapple yogurt. Titratable acidity and moisture content increased with storage time without any marked change in pH. Yogurt spoilage was evident from the yeast odour when yeast counts had reached 106 -108 cfu ml-1. A product shelf life of 6 days at 10oC and 48h at 30oC is recommended and the concentration of milk solids should be increased in order to produce a more nutritious yogurt.