Effects Of Processing Technology And Storage Factors On Oxidation And Flavor Of Flavored Walnut

At present,there are many kinds of domestic walnut leisure products,but there are relatively few studies on walnut products with added spices.In this paper,we developed a flavored walnut,which is obtained by boiling and adding ingredients to the walnut kernel.We have optimized the processing technology of this product,measured the aroma components of raw walnuts,hot air dried walnuts and roasted walnuts,and exploring the effects of processing on its flavor.The effects of different processing steps on product quality were studied.At the same time,flavored walnuts were packaged and protected by different treatment methods in order to predict the shelf life at room temperature(20?),and provide a theoretical basis for its development.The details are as follows:Development of flavored walnuts.We baked the flavored walnuts under different temperatures and times,then determined the acid value,peroxide value and iodine value of the flavored walnuts.We got that the best baking condition is 100 C hot air drying for 8 h,which have the least degree of fat oxidation and high quality.At the same time,the differences among flavors of raw walnut,hot air dried and roasted walnuts were studied.The content of flavor substances was 19,32 and 44 in the original walnuts,hot air dried walnuts and the roasted walnuts respectly.It proves that processing has a certain positive significance for the emission of its flavor.The effect of processing on flavored walnuts.We measured and analyzed the oil quality index,total phenol content and malondialdehyde content in the process of baking flavored walnuts.The change trend of flavored walnuts quality during processing stages were obtained:The peroxide value,p-anisidine value,total oxidation value,malondialdehyde content and total phenol content of the hot air dried stage changed significantly more than the cooking stage(p<0.05).There was no significant difference in the acid value between the two stages(p>0.05).This indicates that the hot air dried stage has a greater impact on the quality of the flavored walnut product than the cooking stage.Study on shelf life of flavored walnuts.The flavored walnuts with different packaging and added different antioxidants were carried out at 60±2? using Schaal oven for accelerated storage experiments.The oil quality index,total phenol content,MDA content and free radicals during storage were investigated.The change in scavenging capacity revealed that the degree of oxidation showed an increasing trend with the prolonged storage time,but vacuum packaging with addition of antioxidants can reduce the rate of lipid oxidation.The shelf life at 20? was obtained by establishing a first-order reaction kinetic equation and extrapolation based on the Van't Hoff equation.The shelf life for processed flavored walnuts was 142 days.The shelf life of flavored walnuts with 0.08%TBHQ single antioxidant was 150 days,and the composite antioxidant with 0.06%TBHQ and 0.02%citric acid could make the shelf life of flavored walnuts to 193 days.The shelf life of flavored walnuts with antioxidants and deoxidizers was 179 days.Vacuum packaging can effectively reduce oil oxidation and extend the shelf life of flavored walnuts to 230 days.The vacuum packaging with deoxidizer has the best anti-oxidation effect,which can extend the shelf life to 257 days.