Determination of Lactulose Content

Lactulose is an important product of the heat treatment of milk and is used as an indicator of heat treatment. Lifeasible offers services to help determine the lactulose content in milk to help determine the situation of heat treatment.

Lactulose is a disaccharide that consists of fructose and galactose molecules. Lactulose is not present in raw milk. To ensure the microbiological safety of the milk, the raw milk is subjected to different heat treatments, such as pasteurization and ultra-high temperature sterilization. During heat treatment, lactose is isomerized to form lactulose. The amount of lactulose produced is closely linked to the pH, time, and temperature of the heat treatment. Therefore, lactulose is used as an indicator of the heat treatment of milk. Lifeasible offers services to help determine the lactulose content of milk to help determine whether the milk product has undergone a reasonable heat treatment.

Fig. 1 Heat treatment equipment for milk.

Our Services

We offer an enzymatic method and a high-performance anion exchange chromatographic method for determining lactulose in milk. Here we focus on the services based on enzymatic methods.

The advantage of the enzymatic method is that multiple samples can be measured simultaneously. This method requires precipitation to remove fat and protein from the milk using zinc sulfate and potassium hexacyanoferrate (II) solution. Subsequently, lactose and lactulose in the filtered sample are hydrolyzed using the enzyme β-D-galactosidase (β-gal). The amount of fructose obtained by hydrolysis is related to the amount of lactulose. Later, the interference of the glucose produced by hydrolysis is gradually removed, and then the fructose content is determined. To determine the original fructose present in the sample, the method also requires a blank determination, which omits the addition of the β-gal step to determine the fructose content.

Operation flow:

Main reference standard:
ISO 11285:2004

Lifeasible has professional operators who are trained to efficiently exclude fructose and lactose interferences in enzymatic determination and to determine lactulose content accurately. In addition, we also offer a high-performance anion exchange chromatographic method for the determination of lactulose. Please contact us for professional lactulose determination services.