Effects Of Varying Worm-infection Degrees On The Nutritional And Flavor Components Of Gomphidius Rutilus Mushrooms And Their Antioxidant Activities In Vitro

Gomphidius rutilus,which belongs to the subphylum Basidiomycotina,is a wild traditional Chinese edible fungus often found beneath pine trees.It has high edible and medicinal value,but cannot be harvested by artificial cultivation.This mushroom is widely distributed in China;it can be found in Hebei,Shanxi,Liaoning,Jilin,Heilongjiang,Hunan,Sichuan,and Tibet.Similar to most ectomycorrhizal fungi,the fruiting bodies of this fungus are usually accompanied by worm infections;however,G.rutilus infected with worms possesses no poisonous effect.Instead,worm infection might relate to the quality,nutritional content,flavor,and antioxidant activity of the mushroom—a question that remains unexplored.Therefore,in the current study,the texture profile,nutrients,and flavor components of G.rutilus without worms（GW）,G.rutilus infected by a small amount of worms（GS;infected area less than 50%）,and G.rutilus infected by a large amount of worms（GL;infected area more than 50%）were explored.Response surface methodology was used to optimize the extraction of polyphenols from the fruiting bodies of G.rutilus.In vitro antioxidant capacity and antioxidant activity of polyphenols were measured.The main results are as follows:（1）The results indicated that the hardness and chewiness of GW were the highest,1.65±0.24N and 3.50±0.85mJ,respectively.GL had the highest moisture content at 819.92±4.03g kg^-1,which was significantly higher than 810.80±3.48g kg^-1 of GW.GS had the lowest fat and highest protein content among the three kinds of mushrooms,the values being2.58±0.16g kg^-1 and 0.64±0.05g kg^-1,respectively.The MSG-like content was higher in GL and GS than in GW.GL displayed the highest amount of MSG-like components at33.37±0.08cg kg^-1,which was 1.72 times that of GW and 1.51 times that of GS.The flavor5’-nucleotide content in GL was the highest at 22.54±1.43cg kg^-1,which was significantly higher than 8.75±0.20cg kg^-11 of GS.The highest EUC value of GL was 9.10mg MSG/g.（2）Effects of varying worm-infection degrees on the fraction and volatile components of G.rutilus mushrooms can be concluded that 5 kinds of chemicals are extracted by simultaneous distillation and extraction（SDE）,and 7 kinds of chemicals are extracted by headspace solid-phase microextraction（HS-SPME）.Compared with SDE,HS-SPME extracted alkanes,aldehydes,and benzenes,but no acid was extracted.The content of alcohols extracted by the two extraction methods was the highest,followed by the ketones,while the esters were few.In the two extraction methods,different samples of G.rutilus contained 1-octen-3-ol,3-hydroxy-2-butanone and 3-octanone,accounting for 49%-87%of relative content.The relative content of 1-octen-3-ol was the highest among all the substances tested.Headspace solid-phase microextraction was used to extract 1-octene-3-ol of GW,GS,and GL,and the relative contents were 80.21%,74.40%and 81.07%,respectively.The contents of 1-octen-3-ol measured by simultaneous distillation and extraction were 38.36%,63.7%,and 54.27%,respectively.（3）The best processing conditions for the extraction of polyphenols from G.rutilus were as follows:ethanol concentration,69%;ratio of liquid to raw material,20mL g^-1;extraction temperature,70℃;extraction time,1.5h;and extraction frequency,3.Under these conditions,the experimental extraction rate of polyphenols was 2.519mg g^-1,which well agreed with the predicted yield.And the polyphenol contents of GW,GS,and GL were192.232mg g^-1,156.109mg g^-1,and 169.916mg g^-1.In addition,the extracts possess ABTS⁺·radical scavenging capacity,Fe³⁺reducing ability（FRAP）,and antioxidant capacity index（ORAC）.Effects of varying worm-infection degrees on the polyphenol antioxidant activity and total antioxidant activity of G.rutilus mushrooms,the antioxidant activity of three kinds of G.rutilus on polyphenols in the ABTS⁺·,FRAP,and ORAC values showed that GL>GW>GS,and for the total the antioxidant activity value showed that GS>GL>GW.（4）Conclusions:the quality of GW is the best from the perspective of texture analysis;the nutritional value of GS is the highest from the nutrition standpoint;the taste of GL is the most desirable from the point of flavor composition;from the perspective of polyphenols and polyphenol antioxidant activity,GL is the best;from the perspective of total antioxidant activity,GS excels.It will provide a theoretical basis for the future study of the mechanism by which worms enhance the properties of these mushrooms and provide scientific evidence for the future study of ectomycorrhizal fungi.