| Phytosterols have the function of reducing the levels of cholesterol,preventing cardiovascular disease and other clear health effects as the new functional food additive.In recent years,It has been widely concerned and applied at home and abroad.Natural plant sterols are safe but they are susceptible to be oxidized to generate a variety of toxic sterol oxides if they are exposure to light,heat,oxygen and other exogenous conditions.The oxidative stability,migration and the formation of sterol oxides in the application of phytosterols are important issues which related to the safety of functional sterols.In this study,the migration rule of sterols at high temperature in oil and multifood system was studied.The stability and migration rule of sterols,the generation and migration of sterol oxides,the changes of the quality of oil added sterols in multi-food systems under frying conditions were studied.The effects of lipid matrix,sterol structure,temperature and other factors on the migration of sterols and sterol oxides were analyzed.The main results are as follows:(1)The effects of oil and multi-food systems,frying time,temperature,the content of sterols and the structure of sterol on the stability of sterol oxidation were studied.Selecting the starch and protein matrix,Using fries and chicken legs as thefrying material to study the oxidative stability of sterol under frying.The results showed that with the increase of frying temperature and the prolongation of frying time,the retention rate of sterol were gradually decreased,when the stability of sterols is better at 140?,nearly half of sterol were lost at 200?when frying 8 h.The order of the influence of lipid matrix on the stability of sterol oxidation was palm oil> tea seed oil> rapeseed oil> sunflower oil.With the increase of the content of sterol,the stability of sterol oxidation was decreased.The order of effect of sterol structure on the stability of sterol oxidation was Vegetable oil sterol > ?-sitosterol> stigmasterol.(2)Analysis the migration rule of sterols in different food matrix under frying conditions.Using the mobility of sterols as index,chosing 140? as thefrying temperature,selecting the starch and protein matrix,Using the fries and chicken legs as representative frying materials to track the mobility of sterol from lipid matrix to the fried materials.The effects of lipid matrix,the content of sterol and sterol structure on the migration were studied.The results showed that sterols were more easier to migrate from lipid matrix tofries,and with the increase of frying batches,the activity of sterol gradually decreased.The effect of sterol structure on the migration of sterol was influenced by lipid matrix and multi-food system.Frying fries and chicken legs were found that with the content increase of sterol,the mobility of sterols was decreased.(3)Analysis of the formation of sterol oxides in different food systems.The effects of sterol addition,lipid matrix and frying time and temperature on the production of sterol oxides were studied by using fries and chicken legs asfrying materials which presented mastarch and protein matrix.The results show that sterols are oxidized during the frying process to generate sterol oxides.The main types of sterol oxides are 7?-hydroxy compounds,7?-hydroxy compounds,3-hydroxy compounds,5?,6?-epoxy compounds,6?-epoxy compounds,7-keto compounds and sterol esters.The order of effects of different food systems on sterol oxides was chicken legs(protein matrix)> direct heating >fries(starch matrix).When the amount of sterol is less than 0.9%,with the increase of the amount of sterol,the content of the sterol oxide were increased.When the amount of the sterol is more than 0.9%,with the increase of the amount of sterol,the total amount of sterol oxide increased slowly and stabilized,0.9% could be used as the node for the addition of sterol.Under frying chicken legs,the node for the addition of sterol was 1.2%.The order of the effect of the lipid matrix on the stability of the sterol oxide is palm oil> rapeseed oil> tea seed oil> sunflower oil.With the temperat-ure increased,the sterol oxides were increased.(4)Analysis the migration of sterol oxides in oils and food systems.Taking the sterol oxide as the index,the starch and protein matrix were selected,the fries and chicken legs were used as the representative frying materials to track the migration of the steroid oxide from the oil matrix to the fried materials.Studied the effect of the frying batches,sterol addition,lipid matrix and frying temperature on the migration rule.The results showed that with the increase of frying batches,the migration of sterol oxides showed a tendency to increase first and then decrease.Compared with chicken legs,sterol oxides were more likely to migrate intofries.With the increase of the amount of sterol,the migration of the sterol oxide tends to decrease slowly,with the increase of the amount of sterol the sterol oxide tends to increase slowly.The order of the effects of different lipid substrates on sterol oxides were sunflower oil> rapeseed oil> tea seed oil> palm oil.With the increase of temperature,the migration of sterol oxides were increased.(5)Analysis of the changes of physicochemical properties of fuselant oil rich in frying conditions.The effects of different food systems on the acid value,the value of anisidine,the carbonyl value,the peroxide value and the fatty acid were studied.The results showed that the initial acid value of high sterol oil decreased with the increase of sterol content,and gradually increased with the increase of frying time.The acid value of the same frying time decreased with the increase of the amount of sterol The order of effects of different food systems on acid value is chicken(protein matrix)> direct heating>fries(starch matrix).The carbonyl value increases with the frying time,increases gradually with the increase of the amount of sterol,and the order of the effects of different food systems on the carbonyl value.Chicken legume(protein matrix)>fries(starch matrix)> Direct heating at high temperature.The order of effects of different food systems on frying oil peroxidation is chicken(protein matrix)> direct heating>fries(starch matrix).The order of effects of different food systems on the stability of saturated fatty acids,monounsaturated fatty acids,and polyunsaturated fatty acids in frying oils is different.High temperature direct heating and friedfries,the critical point of changes in fatty acids is the amount of sterol added 0.9%,while the fried chicken,the critical point is changed to 1.2%. |
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