Analogous pairs of polar and non-polar antioxidants in rosemary-gallic acid microemulsion system for deep frying application.

The aim of the study was to compare the frying performance of soybean oil using microemulsified rosemary-gallic acid (RG30ME) liquid against non-microemulsified RG30 liquid in deep-fat frying of French fries. Frying trials were conducted for 70 frying cycles. The oil samples were analyzed for induction period at 100°C, peroxide value (PV), p-anisidine value (AV), acid value, % total polar compounds (TPC) and colour parameters after every 10 frying cycles and the results were statistically analyzed. Frying performance of soybean oil in terms of number of extra frying cycles and % improvement offered by microemulsified RG30ME liquid were compared against an untreated control and non-microemulsified RG30 liquid for all quality parameters. Overall, addition of microemulsified RG30ME liquid at 250 and 500 ppm respectively improved the frying performance of soybean oil by 280% and 940% for induction period, 125% and 150% for % total polar compounds and 50% and 70% in TOTOX value respectively in comparison to untreated control. When compared to non-microemulsified RG30 liquid at the same inclusion rate of 500 ppm, improvement by 34% for induction period, 11% for % total polar compounds and 6% in TOTOX value respectively were observed. Microemulsified RG30ME liquid is unique, as it is based on a microemulsion carrier allowing better distribution of the antioxidants combined with a better solubility into oil matrices, resulting in protection against oxidation in deep fat frying application.