Ten batches of yoghurt were made from cow's milk. Control yoghurt (CI)
was made from cow's milk fortified with 3.0% non-fat dry milk (the total equal eleven
batches). Another five batches were made from cow's milk fortified with non-fat dry
milk at the rate of 1.5% and 0.0,0.3,0.35,0.40 and 0.45% gelatin (C2. T₁• T2. T3 and
T₄), respectively. The other five batches were made from cow's milk fortified with
0.0, 0.45, 0.50, 0.55 and 0.60% gelatin (C3, T5, TIS, T7 and T_e), respectively. All
yoghurt treatments were sampled at " 3, 6, 9 and 12 days of storage period for
chemical, rheological and sensory evaluation. The results showed that reduction of
non-fat dry milk caused a significant decrease in total solids, total protein. ash,
lactose and acetaldehyde contents of yoghurt as well as scores of organol~ptjc
properties. While it did not affect the fat content of yoghurt. Addition of gel~tin to
yoghurt milk improved the organoleptic properties and increased acetaldehyde
conlenl and titratable acidity, while decreased pH values. Adding of gelatin did not
affect significantly total solids. total protein, fat, ash and lactose contents of yoghurt
for each t~pe of milk. Total solids, ash and titratable acidity increased as storage
period progressed, while total protein, lactose and pH values decreased. Scores of
organoleptic properties did not change as storage pertod a.dvan~d up to the sixth
day, thereafter, decreased up to the end of storage period. ~ynelesis. of whey
decreased up to' the sixth day 'of storage. then it increased as storage,.perjod
progressed. Total bacterial. streptococci and lactobacilli counts increased during j)'le
first three days of storage period. then decreased up '0 the end of storage period. v ,