3.5.3. Peroxide value
Peroxides are the foremost initial reaction products of lipid oxidation, which are responsible for primary oxidation. Oil, initially forms hydroperoxide compounds, which are a good indicator of lipid oxidation under normal condition. However,
at high temperatures, it breaks and forms secondary oxidation products during cooling. The peroxide value of fresh RBO
was 1.63meqO2/kg. After heating and frying for 1–6 cycles, the peroxide value was found to increase from 2.2meqO2/kg to 3.6 and 3.0 to 4.0meqO2/kg in case of heating and frying, respectively (Fig. 3b). The oil showed a comparatively higher degree of degradation during frying as compared to oil subjected to heating only.
Peroxide value is useful as an indicator of oxidation at the initial stages, however, it is not related to the frying duration,
but with the formation and breakdown of oxidation products. Peroxides are unstable and decompose at frying temperature. Peroxides may even increase after the sample is taken from the fryer. Hence it is generally not a very reliable parameter to determine deterioration of frying oil quality (Che-Man and Wan-Hussin, 1998; Sulieman et al., 2006).