3.5.1. Free fatty acids (FFA)
Free fatty acids (FFA) are the main products of oil hydrolytic, enzymatic and thermal hydrolysis that considered as an important marker to measure the rancidity and oxidative deterioration of the food/lipids. In addition to treatment, the effect of storage time on FFA% was also significant (p<0.05 ) as the value of FFA% increased as the storage period increased. Except for day 0 of storage, on the 15th, 30th and 45th day, there was significant difference between the treatments in terms of FFA% (p<0.05 ). The FFA% decreased as the concentration of extract was increased. The highest FFA% contents (5.21%) were observed in control group (T0) (p<0.05 ) on the 45th day while T750 and TTBHQ showed the lowest FFA contents (2.81% and 2.73%, respectively) on the same day of storage. Totally, except T0, FFAs content in cold-pressed sesame oil treatments was lower than Codex Alimentarius standards (Alimentarius, 1999) (Acid value: 4.0 mg KOH/g Oil). These results signify anti-oxidation activity of the Senjed peel aqueous extract.
Results of treatments (Fig. 2), revealed that T750 had better effect on reduction of FFA contents (e.g. 0.91, 1.72 and 2.81% on day 15, 30 and 45) comparing to the FFA% values of the positive reference group (TTBHQ) (0.75, 1.35 and 2.73% on day 10, 20 and 30) respectively.
Totally, except T0, FFAs content in cold-pressed sesame oil treatments was lower than Codex Alimentarius standards (Acid value: 4.0 mg KOH/g Oil), so we deduced that Senjed peel aqueous extract as a potential natural active ingredient, can improve the shelf life of oils and fats. Previously, Hussain et al. (2018); Iqbal & Bhanger (2007); Elaigwu et al. (2019), Jung et al. (2021), and Shahid et al. (2018) also claimed that antioxidant activity of sesame seed extracts, garlic extracts, leaf extracts of Neem, rosemary and garlic, and cinnamon extract exhibited the comparable reduction effect on FFA contents in different oil as compared with synthetic antioxidant.