Lactoperoxidase (LP)

It is one of the most heat-stable enzymes in milk, and its inactivation is commonly used as an index of the intensity of pasteurization (Shakeel-ur-Rehman & Farkye, 2003). It presents antimicrobial activity in conjunction with hydrogen peroxide (H2O2) and thiocyanate (SCNK): The oxidation of thiocyanate by H2O2 generates intermediate products (e.g., hypothiocyanate ion, OSCN-), which inhibits microbial growth. This enzymatic system has been approved by WHO as a method for preservation of raw milk in warm, tropical climates where cooling facilities are not available (IDF, 1988).

The LP system is effective against a variety of microorganisms, including both Grampositive and -negative bacteria, fungi, and viruses. It allows shelf-life extension of pasteurized milk held at 10°C by more than 20 days (Kamau et al., 1991). In cheese making, in spite of possible reduction of the starter activity, LP system has been successfully tested for prolonging the shelf life of yogurt, buffalo mozzarella, cottage cheese, and other fresh cheeses (Seifu et al., 2005). A further recent application is discoloration of fluid whey, in particular when deriving from cheese milk fortified with annatto. The strong oxidizing capacity allows OSCN- to react with carotenoids, leading to destruction of conjugation and subsequent color loss of the main apocarotenoid pigment nor- bixin (Campbell et al., 2012).

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