Deep-fried keropok lekors Increase Oxidative Instability in Cooking Oils

Background: This study was performed to compare the oxidative quality of repeatedly heated palm and soybean oils, which were used to fry keropok lekors and potato chips.
Method: A kilogramme of keropok lekors or potato chips was fried in 2.5 L of palm or soybean oil at 180 °C for 10 minutes. The frying process was repeated once and four times to obtain twice-heated and five-times-heated oils. The peroxide value and fatty acid composition of the oils were measured.
Results: Frequent heating significantly increased the peroxide values in both oils, with the five-times-heated oils having the highest peroxide values [five-times-heated palm: 14.26 ± 0.41 and 11.29 ± 0.58 meq/kg vs fresh: 2.13 ± 0.00, F (3,12) = 346.80, P < 0.001; five-times-heated soybean: 16.95 ± 0.39 and 12.90 ± 0.21 meq/kg vs fresh: 2.53 ± 0.00 oils, F (3,12) = 1755, P < 0.001, when used to fry keropok lekors and potato chips, respectively]. Overall, both oils showed significantly higher peroxide values when keropok lekors were fried in them compared with when potato chips were fried. In general, the heated soybean oil had significantly higher peroxide values than the heated palm oil. Fatty acid composition in the oils remained mostly unaltered by the heating frequency.
Conclusion: keropok lekors, when used as the frying material, increased the peroxide values of the palm and soybean oils. Fatty acid composition was not much affected by the frequency of frying or the fried item used.