The influence of GDL concentration on milk pH change during acid coagulation

PKB IMLEK, Padinska Skela, Belgrade (1)
Department of Food Technology and Biochemistry, Faculty of Agriculture, Belgrade-Zemun (2,3,4)


Skim milk powder was reconstituted to obtain milk A (with 8.01% TS). Milk A was standardized with 3% of skim milk powder and 3% of demineralized whey powder (DWP), respectively, to obtain milk B (with 11.15% TS) and milk C (with 11.10% TS). Milk samples were heat treated at 85ºC/10 min, 90ºC/10 min and 95ºC/10 min, respectively. Untreated milk was used as control. Acidification was carried out at 25ºC, 35ºC and 45ºC during 240 min with GDL (glucono-d-lactone), namely with the amount of 0.5%, 0.75%, 1.0%, 1.25% 1.5%, 1.75%, 2.0% and 3.0% of GDL, respectively. The results showed that all investigated factors, explicitly GDL concentration, acidification temperature and applied heat treatment of milk as well as added DWP influence the change of pH during acidification. Milk samples standardized with DWP had smaller buffer capacity and faster change of pH than samples standardized with skim milk powder. Only at acidification temperature of 25ºC, added DWP did not influence the change of milk buffer capacity regardless of the change of casein:whey protein ratio. Under this acidification condition, both milk samples standardized with skim milk powder and DWP had similar final pH values.

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