Assessment of heat treatment of various types of milk

Raw milk (RM), reconstituted condensed milk (CM) and three types of reconstituted milk powders (SMPs) were heated indirectly at 80–140 °C for 4 s. Native β-lactoglobulin after 90 °C treatment of RM was 1132 ± 167 mg/L but no reliable quantities were estimated at temperatures >100 °C, whereas 218 ± 43 mg/L residual α-lactalbumin were found at 130 °C. Average lactulose contents from 51 to 1549 mg/L were detected at ⩾100 °C; average furosine was 1.9 and 126.5 mg/L in raw and 140 °C treated milks respectively. The behaviour of heated CM was similar to that of heated RM except for higher furosine concentration. Reconstituted SMPs contained high quantities of lactulose and furosine, the ratio of which was lower than in similarly treated RM. Among the market milks analysed, the group of high-pasteurised milks was highly variable; i.e. native β-lactoglobulin was 69–2831 mg/L, lactulose 0–824 mg/L and furosine 3.3–68.8 mg/L.