Changes Of Nuts Chemical Component Under Different Packing Materials And Storage Condition

It is easy to be oxidized and deteriorated in melon seeds and walnut products during storage and transportation.Thus,there is important value for prolonging the shelf life of nuts by studying different packing material and keeping condition.Rancidity of oil can be prevented by using suitable packing materials and keeping conditions.Baked melon seeds and walnuts which were vacuum-packed by aluminum foil bag((polyethylene/polypropylene/aluminum foil),PVDC(polyvinylidene chloride two),and composite bags(polyethylene/nylon/PP)respectively were stored in a condition with constant temperature(39?)and humidity(91%-93%RH),normal temperature(7-25?),light(18-22?),individually.Water activity,peroxide value,acid value,carbonyl value and TBA of the sample were detected regularly during the storage,and the sensory evaluation were discussed in this paper.The results show as follow:(1)Hydrolysis and oxidative rancidity of the products occurred simultaneously during the storage.Rate of the reaction in melon seeds and walnuts could be promoted by increasing temperature and humidity as well as sunlight,which can inhibited by the high barrier packaging materials.(2)The acid value,peroxide value.TBA and carbonyl value of the sample all increased during the preservation process.The date shows the peroxide value,carbonyl value and TBA increased faster,however the acid value increased slowly,relatively.(3)The study on the changes of chemical components of baked melon seeds which were stored in different package and condition shows that the peroxide value was easy to exceed the standard.In constant temperature and humidity condition the peroxide value of seeds with PVDC and aluminum foil bag as well as composite bags were above the standard after 35d,56d and 21d,respectively.In normal temperature condition,the peroxide value of seeds with PVDC,aluminum foil bag and composite bags were above the standard after 220d,280d and 140d,respectively.However in the sunlight all sample were not excess standard.At the same time.the acid value of melon seeds was fully justified by GB 19300-2014.(4)The study on the changes of chemical components of walnuts which were stored in different package and condition shows that the peroxide value was easy to exceed the standard.In constant temperature and humidity condition the peroxide value of seeds with PVDC and aluminum foil bag as well as composite bags were above the standard after 21d,28d and 42d,respectively.In normal temperature condition,the peroxide value of seeds with PVDC,aluminum foil bag and composite bags were above the standard after 180d,220d and 120d,respectively.However in the sunlight all sample were not excess standard.At the same time,the acid value and carbonyl value of melon seeds was fully justified by GB 19300-2014.The srudy shows that the preservation effect of there kinds of different packaging materials was aluminum foil bag>PVDC>composite bag.Though the tenacity and preservation effect of PVDC is similar to aluminum foil bag,think about the price and the possibility for air leak of vacuum-packed,the PVDC was chosen to package melon seeds and walnuts in the process of production.