Effect of Acid Value on TBHQ and BHT Losses in Heating Oils: Identification of the Esterification Products of TBHQ and Free Fatty Acids

Abstract

The loss of phenolic antioxidants is one of the major problems associated with the food frying process. As temperature increases and heating time is prolonged, losses of both tertiary butylhydroquinone (TBHQ) and butylated hydroxytoluene (BHT) are significantly increased. In this work, the effect of different types of free fatty acids (FFA) and the acid value (AV) of soybean oil (SBO) on TBHQ and BHT losses during heating were systematically studied. The results showed that the higher the AV of SBO at 120 or 180°C, the greater the TBHQ loss. The type of FFA also had an observable effect on TBHQ losses at both temperatures, whereas FFA type had no effect on BHT losses. Employing high performance liquid chromatography and liquid chromatography-mass spectra (LC-MS analysis, it was determined that esterification of TBHQ with FFA (C 8:0 , C 18:0 , C 18:1 ) occurred at 120 or 180°C, whereas esterification of BHT with FFA (C 8:0 , C 18:0 , C 18:1 ) in SBO was not observed. Nuclear magnetic resonance analysis showed that esterification occurred at the 4-position of TBHQ.

Thermal Losses of Tertiary Butylhydroquinone (TBHQ) and Its Effect on the Qualities of Palm Oil

“…This indicated that TBHQ itself was the main volatilization product of TBHQ in PO under the heating condition. Similar results were reported by Li et al 20 . Several transformation and decomposition products were also observed in volatilization products.…”

“…The extraction procedure was as followings 20 : 2.00 g of each of melted oil samples was weighed into a 10 mL test tube, and 4 mL of methanol was added. The mixture was agitated for 2 min using a vortex mixer and then centrifuged at 2,000 rpm for 2 min at room temperature.…”

Free fatty acids increase gossypol losses in soybean oil during heating

“…Similar phenomenon occurred about tertiary butylhydroquinone (TBHQ) and butylated hydroxytoluene (BHT) losses [25,26], which were mainly attributable to the volatilization and transformation of TBHQ and BHT during heating [27]. According the previous reports [25,26], we hypothesized that gossypol losses might be due to the volatilization and transformation of gossypol.…”

“…These results suggested that gossypol losses were attributed to the transformation of gossypol. And the effect of volatilization on gossypol losses can be negligible, which were different from that (evaporation) of BHT and TBHQ losses at higher temperatures. These differences might be ascribed to the higher molecular weight (518) and boiling point (707°C) of gossypol than those of BHT (MV, 220; b.p., 265°C) and TBHQ (MV, 166; b.p., 295°C).…”

“…According to our previous report , we hypothesized that the greater losses of gossypol in higher FFAs oil samples might be ascribed to the more transformation of gossypol in the presence of FFAs. To verify the transformation of gossypol in oil samples in the presence of FFAs, SBO samples (5.00% FFAs) containing 200 mg/kg gossypol were heated at 120°C for 8 h. The results of HPLC and LC/MS of SBO samples showed that the transformation products of gossypol were found in the oil samples and the esterification of gossypol with FFAs was not found.…”