Abstract:
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 palm oil and to assess its oxidative stability during heating by adding passion fruit leaf extract
as an antioxidant. Acetone was used as the solvent to extract antioxidant components from fresh
leaves with a sample to solvent ratio of 1:10 (w/v). Negative control (oil samples without any
added antioxidants), positive control (oil sam-ples 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 stability under continuous heating at 170±5 °C.
Continuous heating was carried out for up to 24 h (30 min heating followed by 30 min cooling),
that is, 24 heating cycles. Sampling was done at 2 h intervals (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, fatty acid composition and
conju-gated 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 in the positive control and
negative control. The average rate of total polar compound formation, expressed as the
percentage increase per heating cycle, was significantly lower in extract-treated (1.29% per
cycle) and positive control (1.27% per cycle) samples than in the negative control (1.68% per
cycle). These results indicate that the sample supplemented with passion fruit leaf extract
exhibited higher thermal stability than both controls, and that fresh leaf extract (1000 ppm) more
effectively controls the thermal oxidation of palm oil than BHT during continuous heating.
