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.