Skim milk powder was reconstituted to obtain milk A (with 8.44% TS). Milk sample A was standardized with different amounts of demineralized whey powder (DWP) to obtain milk B (with 9.71% TS) and milk C (with 10.75% TS). Milk samples were heat treated at 85ºC/20 min and 90ºC/10 min, respectively. Untreated milk was used as control. Milk samples were inoculated with 2.5% of commercial yogurt culture (containing Lactobacillus delbrueckii subsp.

The influence of pH (6.5 and 5.8), amount of added CaCl₂ (0, 200 and 400 mg/l)), coagulation temperature (30ºC and 35ºC) and heat treatment of milk (65ºC/30 min and 87ºC/10 min) on the rate of rennet induced milk coagulation (s) were investigated. The time (s) from rennet addition to onset of gelation (as indicated by the first visible floccules) was measured.

Skim milk powder was reconstituted in distilled water to obtain reconstituted milk A (8.44% TS), milk B (9.65% TS) and milk C (10.84% TS). The yogurts were produced from untreated milk and milk heat treated at 85°C/20 and 90°C/10 min, respectively. Milk samples were inoculated with 2.5% commercial yogurt culture and incubated at 43°C until pH 4.6 was reached.

Skim milk with 9.15% DM was heat treated at 85°C/10 min, 90°C/10 min and 95°C/10 min, respectively. Untreated milk was used as control. Milk samples were coagulated by glucono-δ-lactone (GDL) at the temperature of 45°C until pH 4.60 was reached. Untreated milk had the longest time of acidification. Nitrogen matter content in sera obtained from untreated milk was 79.40 mg%.