Effects Of Vitamin E Microcapsules On Oxidative Stability Of Different Types Of Fatty Acids During Frying

Edible oils are inseparable from human,which not only bring specific flavor,but also provide unsaturated lipids.Unsaturated lipids are essential nutrients for human body,while unsaturated lipids are easily oxidized and extremely unstable under high temperature conditions such as frying,owing to the existence of double bonds.The addition of vitamin E to edible oils is generally considered as an effective strategy for relieving the oxidation of unsaturated fatty acids.However,vitamin E is unstable under high temperature conditions,which prevents the use of vitamin E in edible oils.Microcapsule is an excellent strategy to improve the stability of heat sensitive materials and increase sustained release capacity,which has been widely used as a kind of food additive and ingredient.In the present study,vitamin E was microencapsulated to improve thermal stability,and oxidation of unsaturated fatty acids at high temperatures was delayed due to the microencapsulation.First of all,the microencapsulation process of vitamin E was optimized with an oxidation induction time as an evaluation indicator.The results had shown that the core material in which the ratio of vitamin E to unsaturated fatty acids was 2:1(w/w)could bring the highest oxidative stability when emulsified with SPG emulsion film.After curing with transglutaminase,tannic acid or glutaraldehyde,the oxidation stability of the microcapsules was significantly improved,among of them,tannic acid had the best effect.The curing agent was further compounded to investigate the curing effect on the wall material.The results showed that the best curing effect was founded in the group of adding tannic acid first and transglutaminase followed,and the curing effect of the compounded curing agent was significantly better than that of the single curing agent.The vitamin E microcapsules with the best curing effect were further freeze-dried,spray-dried and organic solvent-substituted dried.The results showed that the microcapsules prepared by organic solvent-substituted dried had the highest oxidation stability.Then,the verification of the oxidation kinetics formula of ln[(1-Y)/Y]=kt+ln[(1-Y₀)/Y₀]showed that this formula could be consistent with the oxidation behavior of methyl oleate and methyl linoleate even at high temperatures of frying.The half-period of methyl oleate was increased by 52%after adding 12.0%(w/w)?-tocopherol microcapsules,at which point the actual addition of?-tocopherol was equivalent to 4.0%(w/w).Through experimental comparison,the addition of 4.0%?-tocopherol directly or in the form of microcapsules had substantially the same effect on the oxidation stability of methyl oleate.Correspondingly,the half-period of methyl linoleate was increased by 26%after adding 8%(w/w)?-tocopherol microcapsules,at which point the actual addition of?-tocopherol was equivalent to2.6%(w/w).However,the oxidation kinetics calculated by k value at this time were reduced by 29%compared to the case of directly adding 2.6%(w/w)?-tocopherol,which was basically consistent with the effect of directly adding 8.0%(w/w)?-tocopherol,which proved that microencapsulation of?-tocopherol effectively delayed the oxidation of methyl linoleate at high temperature condition.Subsequently,the effects of microcapsules prepared by different curing agents or drying methods on the oxidative stability of mono-and polyunsaturated fatty acids were investigated.The results showed that the addition of microcapsules cured by transglutaminase and followed by freeze drying had the most significant retardation effect on the oxidation of methyl oleate.Nevertheless,the?-tocopherol microcapsules prepared by the combination of tannic acid and transglutaminase and dried by organic solvent replacement have the best effect of delaying the oxidation of methyl linoleate.The structure of microcapsules prepared by various methods was investigated.The results had shown that the?-tocopherol microcapsules which were cured by tannic acid and transglutaminase and freeze-dried had poor ability to inhibit the oxidation of unsaturated fatty acids possibly due to the?-tocopherol microcapsules prepared by the above method had too much density.The effect of?-tocopherol microcapsules prepared by tannic acid and transglutaminase and organic solvent-substituted dried on the delayed oxidation was based on the type of unsaturated fatty acids.The force between the wall material and methyl oleate was weak.After drying,the microcapsules with the methyl oleate as core material had more obvious pores,resulting in the loss of the core material.In contrast,the wall structure of the microcapsule was relatively complete when the core material was methyl linoleate.The manufacturing process of vitamin E microcapsules directly affected the physical and chemical properties of final products.The addition of vitamin E microcapsules to unsaturated fatty acids could effectively inhibit the oxidation of unsaturated fatty acids at high temperatures,and the effects were different due to the various core materials and the different preparation methods of microcapsules.