3.5.2. Peroxide value (PV)
The PV measurement is a good indicator for the evaluation of oil quality in the initial stage of oil oxidation process (Hussain et al., 2018). By increasing the storage time, a gradual increase in peroxide value of all samples was observed (Fig. 2). At all stages, highest PV was observed for negative control sample (T0) followed by T100, T200, T500 and T750 respectively. Senjed peel aqueous extract at all concentrations decreased the peroxide value of the cold-pressed sesame oil which concluded the good antioxidant and stabilizing ability. A regular increase in PV as a function of storage time was observed for all the samples at all intervals, but this increase was very slow for stabilized samples with Senjed peel aqueous extracts. PV of TTBHQ was lower than T750 initially; but became almost equal at the 45th day of storage. Generally, change in peroxide values
were in a concentration-dependent manner and the values for all samples correspond to normal Codex values (Alimentarius, 1999), which recommended a maximum PV of 15 meq O2kg-1. A pattern similar to the results of our study was also observed by Hussain et al. (2018) and Iqbal & Bhanger (2007) that studied the effect of methanolic extract of sesame seed and garlic extracts on the stability of sunflower oil. They suggested that sesame seed extracts (1000 μL/100 ml oil) and garlic extract (1000 ppm) can be considered as BHT alternative.