Study On Physicochemical Characteristics Of The Quality Of Dry Red Wines From Wine Regions In The Northwest Of China

The northwestern part of China is located in arid and semi-arid regions.It belongs to the temperate continental climate and is an important high-quality wine region in China.Xinjiang,Ningxia Helan Mountain,and Wuhai wine regions consist of the most important wine regions in the Northwest of China.At present,the evaluation of the quality characteristics of wines mostly uses sensory evaluation by professionals.However,due to the lack of a system for evaluating wine quality and the lack of research for wine characteristics,these regions haven’t showed regional advantages and haven’t had famous wine brands compared with famous wine brands in abroad,which limits the development of these wine regions.In order to provide a resolution to these questions,this study analysed physicochemical indices,flavor-related physicochemical indices,flavour compounds,and sensory characteristics of 27 wine samples from Xinjiang,Ningxia Helan Mountain,and Wuhai wine regions.Using the multivariate statistical methods including ANOVA,Principal component analysis(PCA),Pearson correlation analysis and cluster analysis to find the indicative physicochemical indices of the characteristics of dry red wine in Northwest China,and establish a physicochemical characterization technology system to evaluate the quality characteristics of wine,thus serving the northwest region.The research on the technical standards of wine quality monitoring lays the foundation.The main results are as following:(1)In order to analyze the effect of conventional physiochemical indices on wine quality characteristics,this study examined the total acidity(TA),volatile acidity(VA),total SO2(TS),free SO2(FS),residual sugar(RS),alcohol content(AC),total soluble solids(TSS),and pH.The results showed that VA(0.45 g/L),TS(67 mg/L),FS(30 mg/L),RS(3.68 g/L),and TSS(32.99 g/L)in Xinjiang wines were the highest whereas Ningxia Helan wines had the highest level of TA(7.17 g/L)and lowest level of AC,TSS,and pH.Wuhai wines showed the lowest level of TS(46 mg/L)and FS(16 mg/L)whereas had the highest pH value(3.84).The PCA showed that the conventional physiochemical indices were not ideal for distinguishing wine samples and could not reflect the quality characteristics of wine.(2)In order to analyze the effect of color-related indicators on the color characteristics of wine,this study used the UV spectrophotometer to determine the color-related indicators.Helan wines showed high level of C*ab,which means that wines from this region have better colour saturation.Meanwhile,a*and b*values of Helan wines are also the highest and the colour of wine samples shows cherry red with pale straw colour.Xinjiang wines have the lowest C*ab and h*ab,and wine samples present rouge red.Wuhai wines show the highest h*ab whereas lowest a*and monomeric anthocyanins,which in accordance to the pale red colour with pale straw of the wine samples.Ningxia Helan wines have highest total anthocyanin,which is followed by Wuhai wines and Xinjiang wines.However,Wuhai wines and Xinjiang wines have higher level of co-anthocyanin than those of the Helan wines.The PC A showed that the color-related indicators can reflect the color difference of wine samples in different wine regions,and can describe the characteristics of wine color and have better evaluation of color characteristics.(3)In order to analyze the effect of wine taste characteristics on the taste index,this study used the ultraviolet spectrophotometer to determine the taste related indicators.The total phenol and HCl indices in Xinjiang wines are the highest,which indicates the ageing potential of wines from this region.Flavonol are highest in Helan wines followed by Wuhai and Xinjiang wines.Flavanol,tannin concentrations,and ethanol indices in Wuhai wines are higher than those in the other two wine regions,which indicates the soft tannin and mouth-feel.The PCA showed that the taste-related indicators can reflect the difference in taste of wine samples from different regions,and have a better distinguishing effect on wine samples and wine regions,and can be used to characterize the taste quality characteristics of wines to a certain extent.(4)In order to analyze the effect of aroma-related indicators on wine aroma characteristics,this study examined the sensory tastes and aroma components of the wine aroma characteristics in Xinjiang,Ningxia Helan Shandong and Wuhai wine regions.Compared with Wuhai and Ningxia Helan wine regions,Xinjiang wines have better spicy and roast characteristics whereas sweet fruity and flower notes are relatively weak.Helan wines have better sweet fruity,sour fruity,and flower but have weak green aroma note.Wuhai wines present green,sweet fruity,sour fruity,and flower aroma notes.Through Pearson analysis,it was found that tartaric acid ester and total acid,fruit aroma,floral aroma characteristics and esters such as acetate and fatty acid ethyl ester were positively correlated,and the tartrate and fruity sweet fruit were positively correlated positively,and Total acid and acetate were positively correlated positively,indicating that the flavor-related physical and chemical indicators represented by tartrate and total acid can reflect the characteristics of wine aroma to a certain extent,and have a good effect on evaluating the characteristics of wine aroma.(5)The physicochemical characterization technology system for the quality characteristics of dry red wines in the northwestern region was initially formed.In this study,the wine quality physicochemical characterization technology system based on color-relatedindicators,taste-related indicators and aroma-related indicators can basically reflect the overall style characteristics of wines,and through color-related indicators,taste-related indicators and aroma-related indicators.The aroma components were clustered and analyzed.The wine samples from the three producing areas were successfully divided into three categories.The clustering effect was good,and the correct rate was 90%.The color-related physical and chemical indicators,taste-related physical and chemical indicators and aroma were reflected from the side.Relevant physicochemical indicators can be used as a physicochemical characterization technology system to describe the quality characteristics of wine.