Evaluation of effect of passion fruit (Passiflora edulis) leaf extract on oxidative stability of palm oil during heating

The growing need for natural alternatives to synthetic antioxidants in edible oils has driven extensive research into plant-derived extracts for enhancing oil stability during thermal processing. This study was carried out to evaluate the effect of continuous heating on the quality of the palm oil and adding passion fruit leaf extract as an antioxidant to improve oxidative stability of palm oil during continuous heating. Acetone was used as the solvent for extraction of the antioxidant components from fresh leaves. Negative control (oil samples without any added antioxidants), positive control (oil samples added with 200 ppm of Butylated Hydroxytoluene (BHT) and test samples (oil samples added with 1000 ppm of leaf extract) were prepared. All oil samples were evaluated for their stability during continuous heating by heating the oil at 170±5 °C. Continuous heating was carried out up to 24 h (30 mins heating followed by 30 mins cooling), that is 24 heating cycles. Sampling was done at 2 h interval (after every 2 heating cycles). The levels of oxidation of the samples were determined by evaluation of peroxide value, p-anisidine value, TOTOX value, free fatty acid content, total polar compounds and fatty acid composition and conjugated diene (CD) and conjugated triene (CT) values. All parameters measured were increased in all three samples, however, free fatty acid content, peroxide value, p-anisidine value and CD and CT values were significantly less in the test samples than positive control and negative control. The average rate of formation of polar compounds (percent increase per heating cycle) was significantly less in the test sample (1.29) and positive control (1.27) than negative control (1.68). These results indicate that sample added with passion fruit leaf extract showed higher thermal stability than both controls and fresh leaf extract (1000 ppm) can more effectively control thermal oxidation of palm oil than BHT during continuous heating.