Estimating the time of frying oils have been used for French fries based on profile changes of fatty acids derived from heated oil model systems

Time of use for frying oils recovered from French fries was estimated based on ratios of fatty acids and values of conjugated dienoic acid (CDA) and/or p-anisidine (p-AV) derived from oxidation data of oils heated to 180°C in model systems. Changes in CDA and p-AV values in oils occurred faster than changes in ratios of fatty acids (oleic to linoleic acids, O/L) and saturated to unsaturated fatty acids (SFAs/UFAs). Oil use times estimated by O/L SFAs/UFAs ratios, and on CDA and p-AV values in oil recovered from French fries were 1.38, 1.42, 0.36, and 0.22 h, respectively. The actual oil use time was 1.5 h. Although oxidation parameters from heated oil models may not accurately reflect changes in oils during deep-fat frying of French fries, ratios of fatty acids in oils may be more useful for predicting the use time of frying oils than CDA and p-AV values.