| Vegetable oil is the main source of edible oil.Oxidation of vegetable oil has important influence on food safety and human health.Due to the influence of the environment and its constituent factors,the oxidation reaction will occur in the process of vegetable oilstorage and frying,and then produce a series of harmful substances.Antioxidants can prevent oxidation reactions from occurring by stopping the formation of free radicals,scavenging free radicals,or promoting their breakdown.At present,there are two main types of antioxidants that prevent lipid oxidation,namely synthetic antioxidants and natural antioxidants.However,numerous studies have shown that synthetic antioxidants can be potentially toxic.Since consumers are concerned about health,it is of great significance to study antioxidants that can inhibit the oxidation of vegetable oiland the formation of potential risk factor.This paper studied the oxidation stability of four natural antioxidants(tea polyphenols,phytic acid,carnosic acid and vitamin E),screened the best combination and concentration of complex antioxidants,and took fresh cut potato chips as the research object to study the effects of complex antioxidants on the oxidation characteristics of frying oil during the processing of potato chips.At the same time,inhibition effects of compound antioxidants on potential risk factors in hot processing--Acrylamide(AA)and Esters of monochloropropanediol(MCPD)were investigated.The main research contents and results of this paper are as follows:(1)Schaal oven method was used to accelerate grease oxidation to study the antioxidant capacity of four natural antioxidants,with Acid value(AV)and Peroxide value(POV)as evaluation indexes.The results showed that the optimal concentrations of tea polyphenols,carnosic acid,phytic acid and vitamin E were 0.3 g/kg,0.5 g/kg,0.12 g/kg and 4 g/kg at 60℃.The combination of phytic acid and carnosic acid had the best effect,and the combination of tea polyphenols and vitamin E had the worst effect.The antioxidant capacity of phytic acid and carnosic acid was significantly higher than that of single antioxidant.Response surface optimization method was used to design the experiment and screen out the optimal concentration of phytic acid and carnosic acid.The results showed that the antioxidant effect was significantly better than that of single phytic acid and carnosic acid when phytic acid concentration was 0.05 g/kg and carnosic acid concentration was 0.2 g/kg.(2)The effects of phytic acid and carnosic acid at different concentrations on lipid oxidation at high temperature were studied,with AV and POV as evaluation indexes.The optimal antioxidant concentration of phytic acid was 0.16 g/kg and that of carnosic acid was 0.4 g/kg at 180℃ for 30 min.According to the response surface optimization method,the experiment was designed and the variance analysis of the data and the response surface diagram showed that AV and POV reached the lowest when phytic acid concentration was 0.06 g/kg and carnosic acid concentration was 0.2 g/kg,and the antioxidant effect of lipid was the best.Compared with single antioxidant,compound antioxidant greatly improved the antioxidant ability of high temperature lipid.(3)The effects of compound antioxidants on oxidation of frying oil,AA,3-MCPD ester and 2-MCPD ester at different temperatures(160～200℃)were studied.The results showed that the compound antioxidants showed good advantages in improving the frying stability of palm oil,and could effectively delay the deterioration of frying oil quality.With the increase of frying temperature,the content of AA in potato chips increased,and the 3-MCPD ester and 2-MCPD ester in frying oil showed a trend of increasing first and then decreasing with the extension of frying time.The addition of complex antioxidants could well inhibit the formation of AA in potato chips,with the highest inhibition rate of 80.5%.The inhibition rate of 3-MCPD ester was 49.20%,and the inhibition rate of 2-MCPD ester was not significant.(4)The effects of palm oil supplemented with complex antioxidants at 180℃ on oil and potato chip quality were studied.Compared with blank group,the texture,a*value and b* value of potato chips prepared with palm oil supplemented with complex antioxidants were not significantly different,the oil content and water content of potato chips were significantly lower than that of blank group,and the L* value decreased slightly.After adding complex antioxidants,the darkening degree of oil was reduced and the reduction range of polyunsaturated fatty acid content was reduced.In conclusion,0.05 g/kg phytic acid and 0.2 g/kg carnosic acid compound antioxidants have better antioxidant effects on low temperature storage of palm oil.Under high temperature,the compound antioxidant composed of 0.06 g/kg phytic acid and 0.2 g/kg carnosic acid can not only inhibit the oxidation of oil,but also inhibit the production of 3-MCPD ester in potato chips and frying oil,and improve the quality of potato chips and frying oil. |
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