Oxidationreduction potential h

The oxidation-reduction (redox) potential (Eh) is a measure of the ability of a chemical/biochemical system to lose (oxidation) or gain (reduction) electrons. An oxidised or reduced state is indicated by a positive or negative redox potential respectively. The Eh of milk is about +150 mV, while that of cheese is about —250 mV. While the mechanism of Eh reduction in cheese is not fully established, it is most probably related to fermentation of lactic acid by the starter during growth, and the reduction of O2 in the milk to H2O. As a consequence of these reactions, the cheese interior is essentially an anaerobic system, which can only support the growth of obligatory or facultatively anaerobic microbes and thus Eh is a major factor in determining what organisms will grow in cheese. In some cheese types, such as Danish Blue and Roquefort, the cheesemaker deliberately alters the cheese Eh to facilitate growth of Penicillium roquforti in the cheese interior.

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