| Castanea henryi is a nutrient-rich nut with high consumer acceptance,and it becomes soft and waxy with a unique flavor after thermal treatment.Fresh Chestnut has high water content and intolerance to storage,so its shelf life and marketing duration is short.Processing could help to guarantee the annual market supply of Castanea henryi products.The color,nutrition and flavor of Castanea henryi changed during cooking and baking,and these changes are closely related with Mail lard reaction.In this paper,nutritive components of fresh Castanea henryi and its changes during heat treatment(60?100?)were measured and analyzed.The aroma components of Castanea henryi under different heat treatment conditions were studied.The effects of amino acids and reducing sugars on the aroma formation were studied by simulated Maillard reaction.In this study,the variation of Castanea henryi aroma was obtained,which provides the technical guidance for product development and quality control of Castanea henryi,and the theoretical basis for the development of Castanea fragrans.The main research contents and results are as follows:1.The C.henryi grown in Qingyuan County of Zhejiang Province were chosen as the raw material.The change of water-soluble protein,reducing sugar,amino acid,starch and other essential nutrients in fresh chestnuts was determined.The results showed that:moisture content 50%;Based on the dry weight,fat content 1.97%;total protein content 8.45%;soluble sugar content 4.41%;soluble protein content 1.4%and the total starch content 63.53%.The soluble sugar in fresh chestnuts is mainly composed by fructose,glucose and sucrose.19 kinds of amino acids were detected in fresh Castanea henryi,in which aspartic acid,glutamic acid,asparagine,arginine,lysine,leucine are the main components.The content of soluble reducing sugar,starch,protein and amino acid of Castanea henryi were significantly changed during the heat treatment.In all of the reducing sugar,the change of the maltose content was the highest.Amino acid content showed dynamic changes,in which,the contents of asparagine,aspartic acid,glutamic acid and arginine,which with high initial content in raw C.henryi changed greatly.The above reducing sugar and amino acids are believed to be mainly involved in Maillard reaction2.Volatile components of Castanea henryi in different heat treatment conditions were determined by GC-MS;The primary aroma components of Castanea henryi were determined by ROAV;The generation rules of aroma intermediates was characterized by product reducibility,fluorescence spectrum and ultraviolet absorption spectrum;The degree of Maillard reaction was characterized by the browning index.The results showed that:the primary aroma components of fresh Castanea henryi include 2-nonenal,3-methyl butyraldehyde,acetaldehyde,ethyl acetate,nonylaldehyde,2-methyl butyraldehyde and 2-pentylfuran;The primary aroma components of heated C.henryi include Decanal,3-penten-2-one,nonanal,ethyl acetate,2,3-pentanedione,octanal,hexanal,ethyl 3-methylbutanoate,heptaldehyde,benzaldehyde,2,5-dihydro-3,5-dimethy 1-2-furanone.The effects of different heat treatments on aroma of Castanea henryi are as follows:The content of aldehydes,ketones,acids,esters and hydrocarbons increased after heat treatment,and the content of aldehydes,ketones,acids and furans increased with the raising of heat treatment temperature.Heat treatment in the low temperature or short time is beneficial to the formation of ethyl acetate.The pH value had a significant effect on the aroma composition of the heat-treated Castanea henryi,which was favorable for the formation of 5-hydroxymethylfurfural under acidic conditions and favorable for the formation of esters under alkaline condition.The ester was mainly 2-methyl crotonate which showing fruit flavor.The types of sugars has significant effect on the composition and content of volatile components in heat treatment of Castanea henryi.By adding fructose,glucose can increase the content of aldehydes(mainly hexanal,octanal,nonanal),hydrocarbons,esters(mainly 2-maleic acid methyl ester).By adding maltose can significantly increase the content of alcohols,ketones,esters,aromatic acids.2-furan methanol?2,4-bis(1,1-dimethylethyl)phenol and maltol were newly generated.The effect of adding sucrose on the aroma of Castanea henryi was not significant.Analysis of Maillard reaction of Castanea henryi by heat treatment showed:Raw Castanea henryi contains more furan,ketones,aldehydes,involved in Maillard reaction under heat treating which is consumed.Heat treatment can produce more heterocyclic small molecular intermediates,and alkaline conditions can increase the rate of Maillard reaction so that conducive to the production of small molecules intermediates.The addition of different reducing sugars can increase the rate of Maillard reaction and the effect of adding monosaccharides is greater than two monosaccharides.3.To study the effects of amino acids and reducing sugars on formation of Castanea henryi aroma,this experiment used 7 kinds of amino acid and maltose to simulate the Maillard reaction,and analysised by comparing with Castanea henryi actual system.(1)The raction of simulation were detected 75 kinds of flavor substances,including hydrocarbons(28 kinds),alcohols(15kinds),heterocyclic compounds(10 kinds),aldehydes(8 kinds)and so non.Compared with the actual system of Castanea henryi,there were much more aromatic,pyrazines,furans and other heterocyclic compounds except acids and ether substances.And decanal,acetaldehyde,octanal,nonanal,acetone,ethyl acetate,methanol,2-furanmethanol,D-limonene,decane,eleven alkanes,twelve alkanes,fourteen alkanes,4-methyl-octane(total 13 kinds)were detected both in simulation and actual system of Castanea henryi.Among which,decanal,acetaldehyde,octanal,nonanal,ethyl acetate is the primary volatile compounds of Castanea henryi.(2)Effects of different heat treatments on volatile components formed in the Maillard simulation system:With the increase of thermal Heat treatment time or temperature.the content of alcohols(mainly 2-furanmethanol),ketones(mainly acetone and irritant)increased obviously.Ester(ethyl acetate)content decreased.Alkaline conditions,aldehydes(acetaldehyde,nonylaldehyde)content increased.The type of carbohydrate has a great influence on the composition of the volatile matter formed by the Maillard reaction.Compared with the real system of Castanea henryi,the change of ethyl acetate was the same.(3)Analysis of Maillard reaction in simulated system:The effect of temperature and time on Maillard reaction was different from that of Castanea henryi,which can be indicated by the increase in the UV absorption and fluorescence intensity.The effect of pH and reducing sugars on Maillard reaction was almost the same as that of Castanea henryi. |
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