For the specific, rapid and sensitive measurement of lactulose in milk and milk-based samples. Reagents included in this kit may also be prepared for use in the procedure described by ISO Method 11285:2004.
INTRODUCTION:
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.
KITS:
Kits suitable for performing 50 assays are available from Megazyme.
The kits contain the full assay method plus:
Bottle 1: β-Galactosidase suspension (3 mL).
Stable for > 2 years at 4°C.
Bottle 2: Glucose oxidase and catalase, lyophilised powder.
Stable for > 2 years at -20°C.
Bottle 3: Buffer (6 mL, pH 7.6) plus sodium azide (0.02% w/v)
as a preservative.
Stable for > 2 years at 4°C.
Bottle 4: NADP+ plus ATP.
Stable for > 2 years at 4°C.
Bottle 5: Hexokinase plus glucose-6-phosphate dehydrogenase
suspension, 2.2 mL.
Stable for > 2 years at 4°C.
Bottle 6: 6-Phosphogluconate dehydrogenase suspension
(2.2 mL).
Stable for > 2 years at 4°C.
Bottle 7: Phosphoglucose isomerase suspension (2.2 mL).
Stable for > 2 years at 4°C.
Bottle 8: Lactulose (0.1 mg/mL) plus D-fructose (0.05 mg/mL)
standard solution (5 mL).
Stable for > 2 years at 4°C.