The Effects of Milk Components on Lactoperoxidase Activity

Abstract

This study examined the effects of storage conditions (in particular temperature and media
composition) and changes in composition of each milk fraction, and of individual components on
lactoperoxidase (LP) activity. The enzyme demonstrated a pulsing characteristic especially in
samples stored at 5 °C, however, temperature and media composition did not have great effects on
the pulsing behaviour of the enzyme. The results also indicated small but statistically significant
variations (P ≤ 0.05) in LP activity between whole milk (control) and acid whey, rennet whey and
cream and non-significant variations (P > 0.05) between the control and skimmed milk, and
between skimmed milk and acid whey. The variations in activities were attributed to the presence
or absence of casein. Though the results demonstrated that LP activity is a function of the
interactive effects of all milk components, casein and Ca were the most influential milk
components on LP activity. However, their net effects relied on the interactive effects of each
other and other milk components. The promotive effect of Ca2+ on LP activity was shown to be
indirect and reliant on pH changes and its influence on LP activity is within certain limits of its
concentrations and under the control of casein.

Keywords: Lactoperoxidase; milk components; milk fractions; activity