However, peroxides products formed are still unstable, decomposes under frying conditions, giving rise to secondary products such as carbonyl and aldehydic compounds. The oil deterioration continues, but the peroxides formed are no longer assayed. This therefore results in a decrease of PV. This explanation confirms the phenomenon observed in control oil in the last three days of heat treatment. It should be noticed that the nature of foods frying seems to have an influence on the PV. In fact, Manral et al.reported that, in the case of frying fish in sunflower oil, the PV can rise from 0.1 meq oxygen/kg to 28.98 meq oxygen/kg after 12 h of frying.