BACKGROUND: The thermal stability of corn oil flavoured with thyme flowers was determined and compared with that of the original refined corn oil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep-frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K(232) and K(270)), colour and chlorophyll, carotenoid and total phenol contents were monitored. RESULTS: The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K(232) and K(270) than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep-frying test showed the accelerated deterioration of both oils in the presence of French fries. CONCLUSION: Compared with the control oil, the thyme-flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance.
BACKGROUND: The thermal stability of cornoil flavoured with thyme flowers was determined and compared with that of the original refined cornoil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep-frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K(232) and K(270)), colour and chlorophyll, carotenoid and total phenol contents were monitored. RESULTS: The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K(232) and K(270) than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep-frying test showed the accelerated deterioration of both oils in the presence of French fries. CONCLUSION: Compared with the control oil, the thyme-flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance.
Authors: Yusof Kamisah; Suhaimi Shamil; Mohd Jadi Nabillah; Sin Yee Kong; Nazurah Alfian Sulai Hamizah; Hj Mohd Saad Qodriyah; Mohd Fahami Nur Azlina; Abdullah Azman; Kamsiah Jaarin Journal: Malays J Med Sci Date: 2012-10