Cytotoxicity of Used Frying Oil Recovered by Different Adsorbents

Abstract

Adsorbents have been used as fi ltration aids for the effective recovery of repeatedly used oil, particularly in terms of physical characters such as color and odor. Effi cacy in the reduction of the cytotoxicity of the used oil, however, remains to be confi rmed. Palm oil was heated at 180 °C for chicken nugget deep-frying for 10 repeated frying cycles, with each cycle involving 4 hr of continuous batch frying with 8 min per batch. Three different fi ltration methods were applied at the end of each cycle and the recovered oils were examined for their cytotoxic effect on Mardin-Darbi canine kidney cell culture. The methods comprised fi ltration through fi lter paper without adsorbent aids (the control) and fi ltration with the aid of magnesol and bentonite adsorbent as treatment groups, respectively. The recovered oil samples from each group were classifi ed into three levels according to the total polar material (TPM) contents (TPM < 20%, 20% ≤ TPM ≤ 25% and TPM > 25%). Cell proliferation was examined for cytotoxicity effects using apoptotic and clastogenic assays, with Hoechst 33342 and Giemsa staining, respectively. Based on the proliferation assay, the magnesol-treated group appeared to be less cytotoxic compared to the bentonite-treated and control groups with TPM contents of 20–25% (P < 0.05). No signifi cant differences among treatment means were detected at TPM < 20%. The TPM contents of the magnesol-treated group, unlike those of the bentonite-treated and control groups, did not exceed 25% in the course of this study. Nuclear fragmentation as an apoptotic characteristic was observed while chromosomal aberration was not found. Active fi ltration with magnesol aids could be suggested as a potential refreshing means for extending the lifespan of used frying oil.