Study On Characteristic Flavor Identification And Flavor Quality Optimization Of Yunnan Goat Milk Cake

Milk cake is a kind of traditional acid-curd cheese,which is rich in nutrition,unique in flavor and elegant in practice.It has a large audience in Yunnan region of China and has regional consumption characteristics.However,at present,most of the traditional acid-curd cheese-milk cake is still made by hand,and there are few researches on its sensory quality and characteristic flavor compounds,which greatly limits the further development and production of goat milk cake.Based on this,the sensory characteristics of milk cake were evaluated by sensory acceptability test,check-all-that-apply method(CATA)and descriptive sensory evaluation.Then,the key aroma compounds of milk cake were analyzed and identified by flavor omics method.The aroma addition experiment,threshold measurement and S-curve method were used to study the aroma interaction among the key aroma compounds.In order to provide some reference for the industrial production of traditional acid-curd cheese in our country,the flavor quality of milk cake was further optimized through screening of aroma-producing bacteria and mixing of starter.The main conclusions are as follows:(1)Firstly,the sensory acceptance test,CATA and descriptive analysis were used to systematically evaluate the sensory characteristics of milk cake.The evaluation results showed that the aroma acceptance level of milk cake samples from different regions of Yunnan province was significantly different,especially in rancid,animalic(goat)odor,milk,sour and fruity odor properties of the samples.Principal component analysis(PCA)and correspondence analysis(CA)were used to analyze the results of CATA to obtain the main sensory characteristics of milky cakes.Among them,milky flavor,fruit flavor and nutty flavor of milky cakes were more acceptable to sensory panelists,while sour and animalic(goat)odor were more difficult to be accepted.(2)The key aroma compounds in the pactone were analyzed by gas chromatography-mass spectrometry(GC-MS),gas chromatography-olfactory(GC-O),odor activity values(OAV),aroma recombination and omission tests.Fifty-five aroma compounds were identified in combination with GC-MS analysis,combined with aroma active compounds(OAV)and GCO screened 27 aroma-active compounds;corrected models by partial least squares correlation analysis(PLSR)of aroma active compound and sensory characteristics;furthermore,the key aroma compounds of milk cake were identified as ethyl butyrate,isoamyl acetate,ethyl caproate,3-methylbutanal,benzaldehyde,3-methyl-1-butanol,phenylethanol,2-heptanone,2-octanone,butanoic acid,hexanoic acid,octanoic acid,decanoic acid,4-methyloctanoic acid and 4-ethyloctanoic acid by aroma recombination and omission tests.(3)The effects of key aroma components on the intensity of aroma properties of milk cake were investigated by aroma addition experiment.Furthermore,the threshold values of single compound and binary mixture were determined for the screened key aroma compounds.The sensory interactions among aroma compounds in milk cake were investigated by S-curve method and σ-τ method.The results of aroma addition experiment showed that the above 8aroma compounds had different effects on the aroma intensity of different sensory properties of milk cake,which might be caused by sensory interaction between different aroma compounds.Furthermore,the interaction between the four fatty acids was analyzed by S-curve,and the synergistic effect of aroma was found among the four fatty acids.Among the 16 groups of mixtures composed of four fatty acids and 2-heptanone,benzaldehyde,ethyl butyrate and iso-amyl alcohol,8 groups had aroma masking effect.In particular,2-heptanone and benzaldehyde have a strong role in masking the fatty acid components that showed the animalic(goat)odor.These results are helpful to further understand and improve the aroma quality of milk cake.(4)Based on the sensory evaluation and key aroma compounds,the aroma-producing and animalic(goat)odor-inhibiting lactic acid bacteria were screened from traditional fermented dairy products.They were identified as Lactococcus lactis subsp.lactis,Pediococcus acidilactici and Lactobacillus plantarum,respectively.The above lactic acid bacteria were orthogonally compounded and milk cakes were prepared.Through analysis,it was found that different bacterial species ratios had a significant impact on the sensory quality of milk cakes.The samples with high sensory acceptability and good flavor quality contained a higher proportion of fruit,nutty,milky flavor and other aroma compounds(such as 2-heptanone,benzaldehyde,ethyl butyrate,isoamyl alcohol);at the same time,combined with the study of the interaction between the animalic(goat)-odor and its key aroma compounds,the combination and proportion of compounds containing 2-heptanone/octanoic acid,benzaldehyde/hexanoic acid,ethyl butyrate/ hexanoic acid in the samples with better aroma quality was closer to the masking ratio,that was,it had an inhibitory effect on the animalic(goat)-odor.It was finally determined that when Lactococcus lactis subsp.lactis: Pediococcus acidilactici: Lactobacillus plantarum = 3:3:1,the animalic(goat)-odor of the compound fermented milk cake can be effectively masked or inhibited.At this time,the overall sensory acceptability of the milk cake was higher,and the flavor quality was the best.