The influence of different heat treatments on the content and distribution of nitrogen matter from milk to sera obtained by aced coagulation of milk with glucono-δ-lactone (GDL)

Abstract

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%. Sera samples obtained from milk heat treated at 85°C/10 min, 90°C/10 min and 95°C/10 min had 47.80 mg%, 45.00 mg% and 43.50 mg% of nitrogen matter, respectively. Distribution of nitrogen matter from untreated milk to milk sera was 12.70%, while distribution of nitrogen matter from milk heat treated at 85°C/10 min, 90°C/10 min and 95°C/10 min to sera samples, were 6.95%, 6.57% and 6.22%, respectively.

Obrano mleko sa 9.15% SM je termički tretirano na 85°C/10 min, 90°C/10 min i 95°C/10 min. Kao kontrolni uzorak korišćeno je termički netretirano mleko. Uzorci mleka su koagulisani pomoću glukono-δ-laktona (GDL) na temperaturi od 45°C do postizanja pH 4.60. Uzorci termički netretiranog mleka su unali najduže vreme acidifikacije pomoću GDL. Kod termički netretiranog mleka sadržaj azota u serumu je u proseku iznosio 79.40 mg%. Kod uzoraka mlečnog seruma dobijenih od mleka tehnički tretiranih na 85°C/10 min, 90°C/10 min i 95°C/10 min, sadržaj azota je bio znatno manji i u proseku je iznosio 47.80 mg%, 45.00 mg% i 43.50 mg%, respektivno. Distribucija azota iz mleka u mlečni serum kod uzoraka dobijenih od termički netretiranog mleka prosečno je iznosila 12.70%, a kod uzoraka dobijenih od mleka termički tretiranih na 85°C/1O min, 90°C/10 min i 95°C/10 min, iznosila je 6.95%, 6.57% i 6.22%, respektivno.