FOOD SCIENCE ›› 2019, Vol. 40 ›› Issue (22): 167-176.doi: 10.7506/spkx1002-6630-20190514-148

• Bioengineering • Previous Articles     Next Articles

Comparison of Enzymatic Characteristics of Lactases from Different Sources and Their Application in Lactose-Free Raw Milk Processing

CHENG Kaili, HU Zhihe, ZHANG Qiuyue, JI Yu, WANG Shuai, WU Weijie, ZHAO Xufei, JIA Lingyun   

  1. (Tianjin Key Laboratory of Food and Biotechnology, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, China)
  • Online:2019-11-25 Published:2019-12-02

Abstract: The objective of this work was to research the enzymatic characteristics of three lactases derived from different sources, and their application in the production of lactose-free raw milk. The composition and molecular mass of the lactases were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Lactase activity was detected using o-nitrophenol β-D-galactoside (ONPG). An electronic nose was used for detecting changes in the odor of raw milk during storage. The results showed that the isoelectric points of lactase A was 4.0 and 5.0, the isoelectric point of lactase B was 5.0, and the isoelectric point of lactase C was 3.0. Lactase A had the highest enzymatic activity at 40 ℃ and pH 6.5, B had the highest enzyme activity at 35 ℃ and pH 6.5, and C had the highest activity at 45 ℃ and pH 5.0. The results of electronic nose showed that there was no significant difference in the odor of raw milk stored at 4–10 ℃ for 12 h. In addition, after hydrolysis with 6 000 U/g of lactase A for 5–6 h or lactase B for 8–9 h at 4–6 ℃, the lactose content in raw milk was reduced to less than 0.5%. Therefore, lactases A and B were neutral lactases while lactase C was an acid lactase, and the use of neutral lactase A was more suitable to produce lactose-free raw milk.

Key words: lactase, enzymatic characteristic, lactose-free raw milk, electronic nose

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