Extraction Of Main Active Components From The Spent Substrate Of Cordyceps Militaris And Its Application In Fresh Storage Of Cucurbita Pepo L.

As a kind of edible and medicinal fungi of traditional Chinese medicine,Cordyceps militaris has been cultured artificially on a large scale.However,in the solid culture of Cordyceps militaris,when the Cordyceps fruiting body is ripe and harvested,the spent substrate such as stroma and its media residues are usually discarded as waste,causing a lot of waste and pollute the environment.In this paper,the main active ingredients including cordycepin and polysaccharides in Cordyceps militaris waste were studied,including grinding treatment before extraction,extraction process and application of extraction products.(1)The effects of superfine grinding time on the active components,physicochemical and biological activities of Cordyceps militaris spent substrate were studied.The results showed that after 4 hours of superfine grinding,the average particle size of powder decreased to 14.31 μm,the surface tension of solution decreased by 60.06%,the water holding capacity decreased to 3.23 g/g and the solubility increased significantly to 0.25 g/g.With the decrease of particle size,the brightness value of Cordyceps militaris waste powder increased significantly(P < 0.05).Fourier transform infrared spectroscopy showed that superfine grinding leached raw materials.The liquid characteristic absorption peak has little effect.Scanning electron microscopy(SEM)results showed that with the increase of superfine grinding time,the particle size of raw materials decreases first and then aggregates.In addition,the yield of cordycepin and polysaccharides in raw materials increased by 29.47% and 33.89% respectively,when the superfine grinding time reached 4 hours.The scavenging capacity of DPPH,ABTS and hydroxyl radicals increased significantly,and the inhibitory capacity of water extracts of raw materials to Escherichia coli,Staphylococcus aureus and Pseudomonas aeruginosa also increased significantly.(2)The effects of hot water ethanol extraction,acid solvent extraction,ultrasound-assisted acid solvent extraction and ultrasound-assisted microwave extraction on the yield of cordycepin and polysaccharides from Cordyceps militaris spent substrate were studied.The results showed that the extraction rates of cordycepin,polysaccharide.Cordycepin were 2.70 mg/g,2.86 mg/g,3.18 mg/g and 2.94 mg/g,respectively;Polysaccharides were 4.45 g/100 g,4.52 g/100 g,4.93 g/100 g and 4.82 g/100 g,respectively.Comparing the performance of four methods in the yield of active ingredients,extraction time and energy consumption,the results showed that the extraction rate of cordycepin and polysaccharide was the highest by ultrasound-assisted acid-solvent extraction method;the extraction time of ultrasound-assisted microwave extraction method was 8 min and 10 min,respectively,with the shortest time consuming;and the energy consumption of ultrasound-assisted microwave extraction method was the lowest,0.03 kW·h for every 1 mg cordycepin or for every 1 g polysaccharide.(3)The antioxidant activity and bacteriostasis of water extract from Cordyceps militaris spent substrate were studied.The results showed that when the concentration of Cordyceps militaris spent substrate reached 2%,the scavenging rates of DPPH,ABTS and hydroxyl radicals were 90.07 %,63.14% and 66.89%,respectively.Under this concentration,the water extract of Cordyceps militaris spent substrate showed good inhibitory effects on Escherichia coli,Pseudomonas aeruginosa and Staphylococcus aureus.The results showed that the scavenging capacity of ABTS and hydroxyl radicals was significantly improved by the mixed solution.In addition,the bacteriostasis circle results showed that 2% and 3% waste-1% chitosan mixed solution had good inhibitory effects on Escherichia coli,Pseudomonas aeruginosa,Staphylococcus aureus and Streptococcus mutans.(4)1% chitosan coating agent,3% water extract coating agent and 1%,2% and 3% chitosan-1%(all the above percentages are mass fractions)were applied to Cucurbita pepo L.The results showed that the waste-chitosan coating agent could effectively reduce the quality loss,browning,soluble solids and ascorbic acid content during storage,the accumulation of malondialdehyde and the increase of peroxidase and polyphenol oxidase activity caused by oxidative stress and oxidative damage,and inhibit the microbial reproduction during cold storage of zucchini.Based on the principal component analysis of electronic nose response,it was found that there were significant differences in Cucurbita pepo L.flavor among different treatments in the middle and late storage period.Finally,sensory evaluation results showed that water extract-chitosan composite coating could effectively retard the deterioration of color,texture and flavor of zucchini under cold storage.Among them,2% and 3% waste-1% chitosan conbining coating had better effect.After 20 days’ storage,the comprehensive score of 2% and 3% waste-1% chitosan conbining coating treatment group still exceeded 5 points,which was significantly higher than other treatment groups.Therefore,Cordyceps militaris waste extract combined with chitosan coating could maintain the quality of Cucurbita pepo L.during chilled storage,and provide a basis for preservation of fruits and vegetables by natural active ingredients combined with chitosan coating.