Effect of ascorbyl palmitate on the preservation of α-tocopherol in sunflower oil, alone and with herbs and spices

Ascorbyl palmitate (AP) (200 ppm) preserved α-tocopherol in sunflower oil at 95°C and delayed the onset of rancidity. Both effects increased with AP concentration (r2 = 0.96 and 0.97 respectively) but levelled off near ∼700 ppm. The improved anti-rancidity effect was due to the increased preservation (P<0.01). Synergism was observed for both effects for AP combined with sage, turmeric, oregano and marjoram. Clove and thyme gave a smaller synergistic effect whereas basil inhibited. Neither bay nor cumin had any effect. Both the preservative (PFp) and anti-rancidity effects (PFr) were directly related to the thyme concentration (0–2000 ppm). Again, the decreased rancidity was due to the increased preservation (P<0.01). The optimum AP concentration (0–1000 ppm) was around 250 ppm (P<0.01) with thyme present (at 500 ppm) (r2=0.99). The increased delay in rancidity was due to the improved preservation of α-tocopherol (r=1, r2 = 0.99, P<0.01). Both the logarithm of the induction time and the preservative effect for the mixture of thyme and AP was directly related to the temperature (80–105°C). The mode of action of AP is also discussed.