Study Of Antioxidant Activity And The Heat Loss Rules Of δ-Tocopherol In Oil And Multispectroscopic Studies On The Interaction Of δ-Tocopherol With Protein

In this paper the antioxidant capacity of ?-tocopherol in different oil or fat systems were evaluated by Rancimat method combined with induction period add value(PA) and the oxidation kinetics model. During heating the different fators influencing the loss of ?-tocopherol and the loss way of ?-tocopherol were studied by heating experiment in the oven. The interaction of ?-tocopherol and its transformation with protein by spectroscopic methods were studied.By Rancimat method combined with induction period add value(PA) and the oxidation kinetics model, the antioxidant capacity of ?-tocopherol in different oil or fat systems(soybean oil, palm oil, teaseed oil, sunflower oil, linseed oil, lard)were evaluated,the results showed in the same oil or fat, as follows as heating temperature increased, PA was decreased, and increased by 10℃, PA was reduced by about 2 times. Under the same temperature and δ-tocopherol dosage, PA in the teaseed oil was the largest, followed by palm oil and lard, finally was the sunflower oil, soybean oil, linseed oil, namely the antioxidant capacity of ?-tocopherol in high content of monounsaturated fatty acids of oils or fats was better. Under different temperature(100~140℃), in the teaseed oil, sunflower oil, linseed oil, lard, as follows as the δ-tocopherol dosage(0~1000 mg/kg) increased, PA was increased, kinetic rate constant(k) was decreased, the antioxidant capacity of ?-tocopherol was increased. Under 100℃ and 110℃, in the palm oil the δ-tocopherol dosage ?600mg/kg, as follows as the δ-tocopherol dosage(0~1000mg/kg) increased, PA was increased, k was decreased. When >600mg/kg, PA was decreased, k was increased, δ-tocopherol showed prooxidants. In addition to the lard, the δ-tocopherol dosage has no obvious effect on activation energy(Ea), this may be due to the Ea value was influenced by the degree of polyunsaturation present in oil or fat, the correlation coefficient |r|=0.608. Within a certain range(0~600mg/kg in palm oil, 0~800mg/kg in other oils), as follows as the δ-tocopherol dosage increased, the 25℃ shelf life was increased. Under certain conditions, when the δ-tocopherol dosage was 200mg/kg in teaseed oil, in palm oil, lard, linseed oil was 400mg/kg, in sunflower oil and soybean oil was 600mg/kg, δ-tocopherol can replace synthetic antioxidant BHT.During heating(120~180℃) the different fators influencing the loss of ?-tocopherol and the loss way of ?-tocopherol were studied by heating experiment in the oven, the results showed as follows as heating temperature increased and heating time was prolonged, the losses of ?-tocopherol was significantly increased. The ?-tocopherol content in the oil have no significantly effect on ?-tocopherol losses. But the initial ?-tocopherol content is higher, after heating, the ?-tocopherol absolute surplus quantity is higher. Synthetic antioxidant TBHQ can delay the loss of the ?-tocopherol. The higher the acid value and peroxide value, the greater the ?-tocopherol loss. The different types of free fatty acid have an observable effect on ?-tocopherol loss: Stearic acid > Oleic acid > Bitterness. The ?-tocopherol loss may be affected by trace composition, oil saturation, the oil quality. Under heating conditions, the ?-tocopherol loss mainly have two forms: volatilization and transformation, and transformation is complementary. Employing GC-MS, the transformations may were 5,6-epoxy-?-tocopherolquinone and 2,3-epoxy-?-tocopherol--quinone.At pH=7.40 condition, the interaction of ?-tocopherol and its transformation with protein by spectroscopic methods were studied, the results showed the quenching mechanism of BSA by ?-tocopherol and ?-tocopherol was a static procedure, while its transformation was a dynamic-static procedure. There was one binding site between ?-tocopherol, its transformation and ?-tocopherol and BSA. The hydrophobic and hydrogen bonding interactions play major roles in the binding of ?-tocopherol, its transformation and ?-tocopherol with BSA and the process was spontaneous. ?-tocopherol, its transformation and ?-tocopherol had an effect on BSA conformation, While the transformation of ?-tocopherol had the greatest influence, followed by a-tocopherol, finally for ?-tocopherol.