Accumulation of 2-tert-Butyl-1,4-benzoquinone in fried food rich in protein and its conversion in oil during deep-frying

Chicken breast, a food rich in protein, was deep-fried in soybean oil (SBO) at 140, 175 and 190 °C for 20 continuous batches, and the profiles of acid value (AV), peroxide value (PV), 2-tert-Butyl-1,4-dihydrobenzoquinone (TBHQ), and 2-tert-Butyl-1,4-benzoquinone (TBBQ) in SBO and fried chicken breast were determined. The results suggested that frying at 140 °C produced increased conversion of TBHQ to TBBQ and oxidation of the frying oil than at 175 °C, which was close to that found at 190 °C. The highest TBBQ peak concentration of 2.89 ± 0.12 and 13.88 ± 0.27 mg/kg for fried chicken breast and frying oil corresponded to the 7th and 6th frying batch at 140 °C, respectively. The experimental results on determination of the AV, PV, moisture and the content of oxygen in frying oil suggested that more moisture and oxygen were retained in oil when frying at 140 °C than that at 175 °C, which may explain the over-conversion of TBHQ to TBBQ when frying at low temperature. The results on aeration frying and water injection frying experiments indicated that moisture and oxygen had a great impact on the oxidation of TBHQ in frying oil.