Thermal treatment of milk is an essential process in the dairy industry. Various heating regimens can be employed, and thus in some cases it becomes necessary to determine thermal history accurately. This can be achieved by quantitative measurement of lactulose, a disaccharide comprising D-galactose and D-fructose that is only produced from the common milk sugar lactose at elevated temperatures. In raw milk the level of lactulose is very low. However, as heat treatment increases this sugar can eventually reach ~ 2 g/L (in the case of UHT milk for example).
This kit (K-LACTUL) is suitable for the measurement of lactulose in milk-based products such as fresh milk, UHT milk, evaporated milk and powdered milk. However, this kit is unsuitable for the measurement of lactulose in samples that have been artificially sweetened, such as condensed milk, where the “free fructose” to lactulose ratio is extremely high.
Reagents included in this kit can be prepared for use in the measurement of lactulose using the procedure as described by ISO Method 11285:2004. However, the slightly modified advanced format K-LACTUL (Rapid Method) developed by Megazyme, that is both more sensitive and rapid, features an additional enzyme, 6-phosphogluconate dehydrogenase, which results in the sensitivity of the method being improved 2-fold. Additionally, optimised selection and use of highly purified enzymes results in a method that can easily be performed within one working day.