The influence of milk dry matter (DM) content (8.20%, 9.27% and 10.28%) and applied heat treatments (untreated milk and milk heat-treated at 90°C/10’) on the viscosity of set-style yogurt and acid casein gel gained by acidification with GDL (glucono-d-lactone) has been investigated. Viscosity was measured during the time of 3 minutes at constant speed of spindle rotation of 20 rpm. The results have shown that yogurt samples produced from untreated milk had higher viscosity values than samples produced from heat-treated milk.

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.

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.