3.1. Chemical composition of Senjed (Elaeagnus angustifolia L.)
The proximate chemical composition of Senjed (Elaeagnus angustifolia L.) fruits and cold-pressed sesame oil are presented in Table 1.
The yield of the Senjed peel aqueous extract was 9.55 ± 0.35%. The yield of ethanolic, methanolic and aqueous sesame seed extracts was in the range of 13.37–29.48%. Methanol had the highest yield (29.48%), and the lowest yield was detected in water extracts (13.37%) (Hussain et al., 2018). Percent yield of potato peels extract obtained with different organic solvents was as follow: Ethanol 10.20%, Methanol 14.75%, Acetone 5.88%, Hexane 13.00%, Petroleum ether 21.00% and Diethyl ether 15.25% (Zia-Ur-Rehman et al., 2004). Soluble sugars (47.73%), crude fibre (21.05%), moisture (19.48%) and titrable acidity (7.53%) were the most common constituents of Senjed fruit, respectively. Considering the positive correlation between the titrable acidic level with total organic acid and phenolic acid (Wang & Fordham, 2007), Ayaz & Bertoft (2001), reported that among determined seven phenolic acids in Elaeagnus angustifolia L., 4-hydroxybenzoic acid (45.8 mg/100 g dry wt) and cafeic acid (32 mg/100 g dry wt) were the most abundant, whereas ferulic acid (2.3 mg/100 g dry wt) and benzoic acid (11.6 mg/100 g dry wt) were least abundant. Crude fibre content of Senjed fruit in this study (21.05%) was in the range of total dietary fibre content of flours from peeled and unpeeled oleaster (Elaeagnus angustifolia L.) (20.67% to 30.65%) that reported by Sahan et al. (2015).
The mean fat content of the Senjed fruits in this study was 0.47 %. Russian olive (Elaeagnus angustifolia L.) fruit samples had low fat content (0.49%), and according to the reports of, oleic acid, linoleic acid and linolenic acid, including up to 92.8 % of the fruit lipid content (Kusova & Luk’yanchikov, 1990). An abundance of palmitoleic acid in fruit peel oil and a high amount of linoleic acid and palmitic acid in seeds oil of E. angustifolia L. was reported (Sahan et al., 2015).
The FFA%, peroxide value, iodine value, and saponification value of the prepared cold-pressed sesame oil was 0.643%, 1.17\(\text{meq}_{O2}\)/\(\text{Kg}_{\text{Oil}}\), 111.81 (\(g_{I}\)/\({100g}_{\text{oil}}\)), and 193.15 (\(\text{mg}_{\text{KOH}}\)/\(g_{\text{oil}}\)) that was below the maximum allowable norm of Codex (Alimentarius, 1999) for cold-pressed oils. The FFA%, peroxide value, and iodine value of the sesame seed cold-pressed oil of several African countries has been reported in the range of 0.9-1.8%, 0.06-6.9 meq O2/kg, and 105-117 (\(g_{I}\)/\({100g}_{\text{oil}}\)), respectively (Gharby et al., 2017; Khalid Sabahelkhier et al., 2008; Nzikou et al., 2009; Ogbonna & Ukaan, 2013). The high iodine value of the sesame oil samples confirmed the high levels of unsaturated fatty acids (UFAs) in their fatty acid profile, which is desirable from a nutritional perspective, but makes them sensitive to autoxidation. Oil oxidative index (OSI) of cold-pressed sesame oil in this study was 8.93 ± 0.53 h that was lower than national reference for frying (13 hours) and blend oils (12 hours) at the temperature of 110°C. Assessment of oil oxidative index (OSI) in 8 cold-pressed sesame oil samples in Zanjan province of Iran showed that the induction periods was within the range of 7.53 ± 0.1 - 9.48 ± 0.1 hours in the cold-pressed sesame oil samples and 18.96 ± 0.26-20.91 ± 0.01 hours in the refined samples (Zanjani et al., 2020). Farmani et al. (2019) reported that OSI of sesame oil from local extraction stores in Mazandaran province of Iran was 8.14 ± 1.14 h.