Research On Flavor Of Domestic Cheddar Cheese

Cheese is the essence of dairy products with high nutritional value and characteristic flavor.Cheese is a traditional food in western countries,applied to people's daily diet,and the consumption is great.At present,cheese market in China is occupied by imported products with less variety and high prices.Due to the spending habits and the expensive equipments,the research in domestic cheese and its flavor is relatively lag.But with the increasing foreign exchanges,the Chinese people's diet structure has changed dramatically,the Chinese government is also laying emphasis on development of new dairy products- cheese.Therefore,in order to reduce blindness in the study of cheese and to speed up the process of domestic cheese,domestic cheddar cheese was chosen as the raw materials and its characteristic aroma components as the main evaluation index in this thesis.Solid-phase micro-extraction,simultaneous distillation extraction,gas chromatography olfactrometry and electronic sesory evalution methods were used for analysising domestic cheese flavor.Main contents and the results were as follows:The extraction methods for volatile components of cheese were optimized and compared in order to choose optimum method and avoid the deviation of different method.For simultaneous distillation extraction(SDE),ether was the optimum solvent and extraction time was 3h . For solid-phase micro-extraction(SPME) , the optimum conditions were: :75μmCAR/PDMS as optimum absorption fibre,absorption time 40min and temperature 40℃,while desorption was 2min at 250℃.Under each optimized condition,65 kinds and 62 kinds of compounds were identified respectively by SDE and SPME methods.The former method provided better results in detecting high boiling-point,low volatile compounds and some acids,aldehydes,ketones,esters with long chain.The SPME method was fit for some alcohols,acids with low boiling-point and sulf-containing components.One hundred cheese flavor compounds were indentified when the three methods were used to complement each other.The characteristic flavor of cheese was investigated in order to establish the quality evaluation index of domestic cheddar cheese.The odor-active components in cheese aroma were indentified and characterized by gas chromatography-olfactometry(GC-O).Aroma extract dilution analysis(AEDA) was used to quantify the contribution of each odor-active component to whole cheese flavor profile.The order according to significance to the cheese was①isobutyric acid = 3-hydroxy-2-butone >②2-nonanone >③2-heptanone =2-undecanone = 2-tridecanone = 2-pentadecanone = octadecanal>④2,3-butanedione = pentanoic acid = acetic acid-1-octene-3-olide = decanoic acid =δ-dodecalactone = glycecol triacetate。 As non-volatile flavor components could directly affect the taste of cheese,and they were also precursor substances of characteristic flavor.The protein hydrolysis and fat hydrolysis during the cheese mature process were studied in order to explore the relationship between characteristics flavor components of cheese and its mature time.The sensory evaluation in cheese flavor at different mature time were studied.The results showed that the flavor change obviously with cheese maturity,and the cream and moldy odor wewe main cheese characteristic flavor;bitter and salty taste were the strongest in taste.HPLC and GC-MS were used for analysing in cheese at different mature time.The results showed that the type and content of free amino acid and free fatty acids had effect on characteristic flavor of cheese.SPME/GC-MS was used for studying flavor components in cheese at different mature time.The results showed that:At 90 day,seven kinds of characteristic flavor components made great contribution to cheese flavor profile , and they were: 2,3-Butanedione, 3-hydroxy-2-butone,2-heptanone,2-nonanone,isobutyric acid,pentanoic acid, decanoic acid.And other characteristic flavor components may be assisted in the latter part of mature cheese.In order to made objective evalution to cheese flavor and to create a flavor model in cheese at different stage of maturity,e-sensory fingerprint analysis (electronic nose and electronic tongue)were used for cheese to determine the odor and taste character at different mature time.The PCA analysis showed that low- maturity was close to middle-maturity in cheese flavor profile;while different from relative high maturity cheese flavor.90 days were the mature time for domestic cheddar cheese,and its main odors were cream and moldy,with bitter and salty in taste.