Page 260 - Natural Antioxidants, Applications in Foods of Animal Origin

Methods and Their Applications for Measuring 239
VetBooks.ir 6.2.6 OXIDATION REDUCTION POTENTIAL (ORP) METHOD

ORP can be an important method for measuring the general oxidative status
of meat products. The ORP method does not measure specific products of
oxidation. It can be used for evaluating oxidation inhibitors (Fig. 6.26).

Platinum REDOX electrode

Meat homogenate
(buffered)
FIGURE 6.26 Oxidation reduction potentials (ORPs) can be used to broadly measure the
oxidative status of meat products. Negative values for ORPs indicate reducing (favorable)
environment. Diagram by Tom Jones.

The ORP method is a direct measurement of the all the oxidized and
non-oxidized compounds in the meat sample (Vahabzadeh, 1986). The elec-
trical potential measured is related to the concentration of oxidized and non-
oxidized species through the Nernst equation.

0.059
E = E + n log 10 [ oxidized and nonoxidized species ] (6.15)
o

where E is the reading taken at the potentiometer in mV,
E is reference electrode in mV,
o
0.059 is a constant calculated by mathematically combining the universal
gas constant, temperature (K), Faraday’s constant,

n is the number of electrons (unknown) involved in the oxidation reduction
process, since meat systems have dilute ionic concentrations (or activities)
n can be ignored.