Research On The Main Flavor Components Of Litchi Wine

The main flavor components of litchi wine were analyzed systematically in view of the problem of unclear flavor components in litchi wine. Firstly, the detection method included HLPC and GC-MS of organic acids, amino acids, aroma components in litchi wine were determined and the species and content of organic acid, amino acid and aroma components in different kinds of litchi wine were detected and analyzed. Then the main flavor components of litchi wine were further explored through principal component analysis and other methods. The changes of flavor composition in the process of brewing were dynamic monitored finally.The main results are as follows:(1) The detection method of organic acids, amino acids and aroma components were determined. Organic acids and amino acids were determined by HPLC, whose recovery rate were82.88%～104.82%and90.91%～103.80%respectively. And aroma components were determined through solid-phase microextraction and gas chromatography-mass spectrometry, and the recovery rate could get more than90%under the particular condition.(2) Through the methods mentioned above, some indexes of correlation were concluded. Among the15kinds of Litchi wine, the alcoholic content was between9.5%and16.0%; the pH was between3.5and4.2; the total acid content was between3.864g/L and53.480g/L; the average content of tannin was0.446g/L; the soft index value was5.864; the sensory evaluation score was69.89which showed poor flavour of litchi wine; softness index and sensory evaluation score were positive correlation, and the correlation coefficient was0.896. As a whole, the flavor and taste of litchi wine were generally mellow, but there were still problems of poor flavor and taste. The total content of10kinds of organic acid in litchi wine was from4326.47mg/L to8111.93mg/L. Among these organic acid, malic acid had the highest average amount which was1918.89mg/L; citric acid had the biggest difference, and its coefficient of variation was82.19%; oxalic acid had the lowest average amount which was178.69mg/L. And malic acid, acetic acid, lactic acid, succinic acid and tartaric acid were the main organic acids which had the most important influence on taste of wine by the analysis of flavor intensity Fu value. Through the analysis of four essential factors, it was concluded that the cumulative contribution rate reached84.48%and the computational formula of comprehensive evaluation of organic acid in litchi wine was Y=0.404238Y1+0.25367Y2+0.213542Y3+0.128551Y4.During brewing process of litchi wine, malic acid had a little change in processing. One part of tartaric acid came from fruit juice, and another part came from the fermentation and clarification process. Succinic acid was produced during the destroy enzyme process and consumed in the fermentation process. Acetic acid mainly came from fruit juice, and its content in litchi wine depended on the enzyme process mostly. Citric acid came from fruit juice and was consumed in processing, therefore its content in finished wine is much lower than fruit juice.(3) The total content of16kinds of amino acids in litchi wine was from553.12mg/L to1278.23mg/L.Wherein, the content of alanine and valine were highest with252.04mg/L and272.91mg/L respectively; the content of aspartic acid content was the lowest. Among these amino acids, the content of essential amino acids was between326.85mg/L and690.40mg/L, accounting for37.17%～80.17%. In category, sweet and bitter amino acids were the main component of amino acids, accounting for63.59%and34.86%respectively. The total content of amino acids was in accordance with normal distribution, and the regression equation was established as follows:Y=0.488206Y1+0.185381Y2+0.156003Y3+0.091031Y4+0.079379Y5.During brewing process of litchi wine, methionine, aspartic acid, serine and isoleucine as the main nitrogen source were quickly consumed and almost used up. Alanine, glutamic acid, tyrosine, phenylalanine, lysine, leucine, valine, threonine and arginine were used partly. Histidine, cysteine and glycine in the fermentation process were not used by Saccharomyces cerevisiae.(4)There were138kinds of aroma components determined in litchi wine, including27kinds of alcohol,9kinds of acids,5kinds of aldehydes and10kinds of terpenes. Among them, benzyl alcohol, isoamyl alcohol,2,3-butylene glycol, acetic acid, ethyl acetate, isoamyl acetate, butyl acetate, ethyl lactate, succinate two n-amyl alcohol and octanoic acid were the main aroma components of litchi wine. The ten essential factors were analyzed in the principal component whose cumulative contribution rate reached84.23%, and the computational formula of comprehensive evaluation of aroma components in litchi wine was as follows: Y=0.189543Y1+0.118203Y2+0.113506Y3+0.10781Y4+0.093735Y5+0.088848Y6+0.081854Y7+0.073293Y8+0.068819Y9+0.064388Y10Aldehydes and alcohols were the main aroma components in litchi juice. During brewing process of litchi wine, the category and content of esters and alcohols increased significantly. While aldehydes were significantly reduced and even disappeared, which resulted in the loss of natural aroma and disharmony of aroma of litchi wine.