우유의 열처리 및 저장 조건에 따른 Lactulose 의 함량 변화

The aim of this work to determine the formation of lactulose during heat treatment process as a contribution to the estabilishment of limits of chemical indicators for different types of heat processed milk and analyze of lactulose for the reconstituted milk added samples. The HTST(75℃/15s) and UHT(130℃/2∼3s) treatment realized with a pilot plant and heat-treated samples were stroed at 4, 10, 30℃ for 4 weeks. Changes in lactulose was evaluated at 7 days intervals. The other heat treatment was sealed in glass tube and heated at 75℃ for 10 to 120s and heated at 130℃ for 2 to 60s in a thermostatically controlled constant temperature bath of glycerol. The reconstituted milk was made with full fat dry milk that reconstituted with deionized water to 10% total solid, and was added to milk at 10, 20, 30% respectively. The samples processed with a HTST pilot plant showed that lactulose was contained at 1.47∼1.52㎎/100ml and 8.19∼8.32㎎/100ml for UHT-treated samples. Changes in the lactulose content of heat-treated samples during storage at 4 and 10℃ for 4 weeks caused a slight increase, however a noticeable increase was observed at 30℃ for 4 week. The glass tube samples showed that high correlations between relative increase in content of lactulose and increasing processing times(75℃: r=0.986, 130℃: r=0.987, respectively). Added with reconstituted milk would cause a increase of the lactulose content linear with increasing addition amount(r=0.982). This results observed for lactulose in commercial milk samples would applied to the detection of chemical changes during heat treatment and illegal use of reconstituted milk.