Application Of β-Galactosidase In Liquid Milk

There are many people in our country who are unable to completely digest lactose, due to the decreasing in intestinal lactase activity. To promote the production and consumption of milk, it is necessary to produce and popularize low lactose milk.In the paper, hydrolysis characteristics of several commercial β -galactosidases were investigated. An optimum β -galactosidase used in the study was determined, and the dosage, hydrolysis condition and process to product lactose milk was determined. 5-HMF is one of the indictors for Maillard reaction. It was also discussed the effects of the sterilized conditions and inhibitors on the concentration of 5-HMF. The hydrogen breath test (HBT) was used in the study to analyze the lactose intolerance in primary school students, and the effects were detected after absorption of low lactose milk.The results indicated that(1) the activity of the galactosidase decreased significantly when heat treatment temperature was above 45℃. The sterilized conditions of milk production can inactive the β -galactosidase.To 3 -galactosidase, the optimum pH value was 6.5-7.5. When milk was treated with G enzyme at 8 to 10℃ for 15hours, or 37 to 40℃for 2hours, with dosage of 0.2%., the degree of hydrolysis for lactose can reached 70%.(2) 5-HMF concentration was measured by using HPLC with UV detection at 280nm, with recovery of 91.7%. The 5-HMF concentration in UHT low lactose milk reached to 4.75μg/ml, which were 18 times higher than that in pasteurized milk, 9 times higher than that in UHT milk and 6.3 times higher than that in pasteurized low lactose milk, respectively.(3) The 5-HMF concentration in UHT low lactose milk was affected significantly by several factors, such as hydrolysis degree of lactose, the combination of temperature and time when sterilization, and stored conditions. If optimum hydrolysis degree is used, cooling rapidly after sterilization, and stored at a lower temperature, 5-HMF concentration and browning can be controlled effectively. When using inhibitors both C1 and B2, 5-HMF concentration was lowered more than 50% than without inhibitors.(4) The relationship between the concentration of 5-HMF and color can be described by ΔL*, Δa* and Δb*. When the concentration of 5-HMF rise, ΔL* of low-lactose milk reduce, and Δa* and Δb* rise.(5) There was about 80.2% occurrence of lactose intolerance in children of age 10 to 11 years. The absorption of low lactose milk can lower the occurrence effectively.