The isomerization and decay of β-carotene in thermal oils were monitored using high-performance liquid chromatography and UV–vis spectroscopy (UV). For the first time, the effects of temperature, dissolved oxygen, oil type and antioxidants on the stability of β-carotene were systematically investigated by first-order kinetics. Isomerization of all-trans- to cis-isomer was a dominating reaction in the initial period (about 3 h for 140–180C). Lower temperature and oil with more unsaturated fatty acids gave positive effects on the β-carotene stability, whereas the dissolved oxygen slowed the decay rate at several conditions (150–180C of soybean oil, 140–180C of peanut oil and 140–150C of ODO). The antioxidants significantly protected β-carotene only when the temperature was lower than 150C, and they almost did not affect the β-carotene stability when the dissolved oxygen was removed.

As thermal treatment of β-carotene in oils become popular during food processing, and the stability of β-carotene is most related to its potential health benefits and nutritive value, the study on isomerization and decay kinetics of β-carotene in thermal oils is particularly important. We found that when β-carotene in oil was heated at 140–180C, isomerization was a dominating reaction in the initial period (about 2–4 h). The following decay of β-carotene of most conditions followed first-order kinetics. When β-carotene was dissolved in thermal oils, low temperature and oil with more unsaturated fatty acids gave positive effects on the β-carotene stability. Moreover, β-carotene always became more sensitive to temperature when dissolved oxygen is removed and antioxidants are added. Those positive impacts were effective only below 150C.