Investigating the stability of chemical and physical characteristics of non-fat set yoghurt containing textured milk during the storage time

The aim of this study was to compare the stability of chemical and physical characteristics of non-fat set yoghurt containing textured milk to those of non-fat and full fat set yoghurt during 14 days storage at 4±1 °C. In order to produce non-fat yoghurt containing textured milk، the temperature of heated skim milk (85-90 °C for 30-35 minutes) was reduced to 42-43 °C and it was combined with 0، 10، 20، 30، 40 and 50 percent of textured milk. The chemical (pH، titratable acidity، protein، fat and total solid) and physical (colorimetrics، syneresis and water holding capacity) experiments were carried on non fat yoghurt containing textured milk، non-fat and full fat yoghurt during the first، seventh and fourteenth day of storage time in refrigerator. The results revealed that textured milk had no effect on the pH، titratable acidity، protein and fat content of yoghurts، but the storage time affected these factors (p<0. 05)، textured milk and storage time affected the amount of total solid in samples. Textured milk improved colorimetrics، syneresis and water holding capacity of yoghurts compared to non-fat yoghurt and this was observed during storage time too. The sample containing 30% of textured milk was the most similar one to the full fat yoghurt، so this yoghurt formulation is recommended to gain appropriate physical and chemical characteristics.