Analysis And Separation Of The Flavor Components In Neoboletus Brunneissimus

The wild edible mushrooms are delicious and abundant of nutrition such as proteins,vitamins and mineral elements,and have the ability to enhance the immune system,reduce blood lipids as well as regulate endocrine.The flavor components of wild edible mushrooms consist of volatile and non-volatile flavor compounds,the former one,including the alcohols,esters and acids,is the cause of the mushroom's unique and cheerful smell,while the latter one,most of which are amino acids,nucleotides and small molecule flavor peptides,forms the specific taste of the wild mushrooms.Neoboletus brunneissimus is one of numerous Yunnan wild edible mushrooms and very popular among the customers because of its unique smell and delicious taste.However,it is difficult to store it due to the effect of the season and environment such as temperature and humidity.The aroma components of the N.brunneissimus haven't been studied yet.Nowadays,the flavor peptides are the key flavor components exist in food and found in many animals and plants.Except the amino acids and nucleotides,the small molecule flavor peptides also contribute to the flavor of the wild mushrooms.So far,there are few studies towards to the peptides in mushrooms,and in this study we focus on the effect of different processing methods on the non-volatile flavor components of the N.brunneissimus,as well as the preparing,separation,purification and identification of the flavor peptides from N.brunneissimus in order to expound the composition of the volatile and non-volatile flavor compounds and their contributions to the flavor,and we hope it will be helpful to the processing and the by-products' developing.The main research contents and results in this paper are as follows:1.Effect of different drying methods and enzymolysis on the volatile flavor compounds in N.brunneissimusOn the basis of the pre-experiments,we treat N.brunneissimus with fresh,vacuum dying,freeze dying,microwave dying,hot air dying and enzymolysis,and use ultrasonic solvent extraction method combined with the GC-MS to extract,identify,compare and analysis the volatile flavor compounds,which consist of 57 volatile compounds,including acids(10),hydrocarbons(29),esters(5),alcohols(4),nitrogen compounds(7)and others(2).The results showed that a total of 51,47,49,19,18 and 44 compounds were detected under different drying methods and enzymolysis.Found that these compounds make huge contribution to the aroma of the N.brunneissimus by cluster analysis and principal component analysis,and reflect the similarity of volatile flavor components of the N.brunneissimus by different drying methods and enzymolysis.Alcohol,acids,esters,and hydrocarbon were changed remarkably after four dehydrations and enzymolysis.The contents of alcohol were reduced,except those processed with freeze drying.The contents of acids were increased,other than those after enzymolysis.The contents of esters were reduced,except enzymolysis and microwave drying.The numbers and contents of hydrocarbon were reduced,except for those treated with freeze drying.The special aroma of N.brunneissimus were increased by microwave drying and enzymolysis,and freeze drying method can protect the volatile flavor components of N.brunneissimus better.2.Study of preparing flavor peptide base from N.brunneissimusUsing enzymolysis to prepare the flavor peptide base,which choose peptide content and sensory evaluation as the index to select the enzyme,namely the flavourzyme and alcalase.The results of single factor test,orthogonal test and compound enzymolysis indicate that the optimum conditions are adding two enzymes simultaneously at the amount of 3000 and 1500 U/g,starting pH 7,reaction temperature 50 ? for 1 h.Under these conditions,peptide content was 9.27 mg/mL and had obvious smell of mushroom and of good umami and sweet taste,and its sensory evaluation was 7.14.The results indicate the way to make flavor peptides base and provide the experimental basis for the separation and purification from the N.brunneissimus.3.The separation,purification identification and taste characteristics of the flavor peptides in N.brunneissimusFractions of two flavor peptides form N.brunneissimus were obtained by gel filtration chromatography,RP-HPLC chromatography combining with the taste dilution analysis and sensory evaluation screening and identified by UPLC-MS/MS.The peptide with the sequence of Ser-Gly-Leu has umami and sweet taste and its taste threshold is 0.78 mmol/L but has no umami enhancement,while the other peptide with the sequence of Lys-Val has bitter and sour taste with the taste threshold of 1.03 mmol/L and has umami enhancement of a threshold of 1.12 mmol/L.It can enhance umami taste when the synthetic peptide concentration is less than 4 g/L while it inhibit umami taste when more than this concentration.It can be considered as two of the flavor compounds which present umami and sweet taste and contribute to the flavor.The research of the volatile and non-volatile compounds in N.brunneissimus improves the database of the flavor of wild mushrooms and are of great importance in seasoning development and China's wile fungus by-products.