PHYSICAL PROPERTIES OF MILK 44 1PH
Figure 11.1 Effect of pH on the oxidation-reduction potential of various systems (from
Sherbon, 1988).aldehyde group of lactose can be oxidized to a carboxylic acid (lactobionic
acid) at alkaline pH but this system contributes little to the redox properties
of milk at pH 6.6.
The E, of milk is influenced by exposure to light and by a number of
processing operations, including those which cause changes in the concen-
tration of 0, in the milk. Addition of metal ions (particularly CuZf) also
influences the redox potential. Heating of milk causes a decrease in its E,,