Effect Of Nano-Packaging Mediated Perforation On Postharvest Quality And Flavor Components Of Volvariella Volvacea During Storage

Straw mushroom(Volvariella volvacea)has unique flavor and is one of the most popular mushrooms among people.V.volvacea is not only rich in nutrients,but also contains functional components which process pharmaceutical value such as anti-tumor and antioxidant.V.volvacea,however,is a typical tropical edible fungus whose postharvest respiration rate is very high and postharvest ripening effect is particularly strong,thereby losing market value soon after harvest in 1-2 day.Moreover,conventional cold storage is not appropriate to preserve V.volvacea whose fruiting body is easy autolyze and liquefy.Therefore,V.volvacea is a kind of edible fungus that is difficult to preserve.The objective of this study was to evaluate the fresh-keeping effect of perforation mediated nanocomposite polyethylene packaging on the preservation quality and flavor components of V.volvacea during storage.The main results were shown as follows:1.The effect of perforation mediated two different kinds of packing was studied on the quality of Volvariella volvacea during storage.Volvariella volvacea was treated by nano-packaging or polyethylene(PE)packaging mediated perforating method at(15±1)C and relative humidity of(85±5)%for 6 days.Meanwhile,straw mushroom with no-packaging treatment was served as control.Weight loss rate,browning degree,L value,firmness,total soluble sugar,protein contents and total soluble solids of Volvariella volvacea were measured everyday.Results showed that the two perforation mediated packing can extend the shelf life of Volvariella volvacea for 2 d compared with the control.In addition,the mushrooms treated with nano-packaging showed the best quality.After 6 days of storage,weight loss rate,browning degree of Volvariella volvacea treated with nano-packaging were 4.47%and 3.29,which were lower than those of polyethylene packaging.And L value(80.63)and firmness(517.2g)were higher than that.While the contents of total soluble sugar and protein,total soluble solids of nano-packaging were 13.15 mg/g,6.21 mg/g and 5.23%,and the retention rate of this two were higher by 13.85%,6.50%and 6.1%as compared with polyethylene packaging.The cell ultrastructure of mushrooms from different stages of storage was observed by electron microscope,and it found that nano-packaging can better maintain the cell wall and membrane.Perforation mediated nano-packaging can effectively inhibit the sensory quality degenerating of Volvariella volvacea,maintain a higher nutritional value,and extending preservation time.2.Volvariella volvacea was treated by nano-packaging or polyethylene(PE)packaging mediated perforating method at(15±1)C for 6 days,and their effects on the physiological and biochemical changes of Volvariella volvacea were studied.Respiration rate,superoxide anion(O2·-)production rate,hydrogen peroxide(H2O2)content,malondialdehyde(MDA)content,superoxide dismutase(SOD),catalase(CAT),polyphenol oxidase(PPO)activity and peroxidase(POD)activity were measured.Results showed that the trend of the change of respiration rate of nano-packaging mushrooms was relatively stable as compared with the other two groups.Significant differences(P<0.05)were observed between nano-packaging mushrooms and the other two groups at day 1,3 and 4.After 6 days of storage,superoxide anion(O2·-)production rate,hydrogen peroxide(H2O2)content and malondialdehyde(MDA)content of Volvariella volvacea treated with nano-packaging were 2.22 mmol/kg·min,51.88 mmol/kg and 8.17 μmol/kg,which were lower than those of polyethylene packaging.The PPO(246.67 U/g-min)and POD(8.02 U/g·min)activity were reduced by 9.7%and 23.3%after 6 days of storage.While antioxidant enzyme including SOD(353.49 U/mgprot)and CAT(43.20 U/mgprot)of nano-packaging were higher than the others.The present date indicated that the perforation mediated nano-packaging treatment could inhibit respiration,reduce lipid peroxidation level of Volvariella volvacea and induce protective enzymes,thus delay the process of mushroom senescence.3.By using high performance liquid chromatography(HPLC),the kind and amount of non-volatile components in Volvariella volvacea during storage including soluble sugar and polyols,organic acids,5’-nucletides and free-amino acid were determined and analyzed.The results showed that trehalose,succinic acid,5’-GMP and phenylalanine were higher in content,which proved that they were the main non-volatile flavor substances for Volvariella volvacea.As storage time advanced,the content of soluble sugar,organic acid and free amino acid were all reduced,except the flavor nucleotide.In addition,the content of the four kinds of non volatile flavor components in nano-packing group were higher than that of normal packaging group.4.In order to ascertain the flavor characteristics of Volvariella volvacea during storage,its volatile compounds were evaluated by head-space solid phase micro-extraction(HS-SPME)and capillary gas chromatography-mass spectrometry(GC-MS).The results showed that the volatile compounds of fresh straw mushrooms mainly consisted of aldehydes and ketones,of which 3-ketone and benzene acetaldehyde were higher in content.With the extension of storage time,the sort of volatile flavour compounds of straw mushrooms was increasing.The content of 3-ketone,the main flavor components gradually increased,while the benzene acetaldehyde content declined.This might be caused by oxidative Browning.At the end of storage,the excitant odour of 3-methyl indole and benzene acetonitrile appeared.The rise of ketones and the decrease of aldehydes in nano-packaging mushrooms were lower than those of normal packaging,and it detected less excitant odour substances.All of the results indicated that perforation mediated nanocomposite polyethylene packaging could reduce the oxidative metabolism of straw mushroom and inhibit the formation of harmful substance.