Determination of target compounds in cava quality using liquid chromatography. Application of chemometric tools in data analysis

Abstract

According to the Protected Designation of Origin (PDO), Cava is protected in the quality sparkling wines made by the traditional Champenoise method were the wine realize a second fermentation inside the own bottle1. Geographical and human peculiarities of each bottle are the main way for the final quality2. The aim of this study is to find correlations and which target compounds are the most representative of the quality of two different grape varieties, Pinot Noir and Xarel·lo. The quality of these two types of grapes is being studied for each variety by a previous classification of the vineyard made by the company who provided the samples (qualities A,B,C,D, being A the better one and D the worst one). The target compounds studied are organic acids and polyphenols. The methodology for the determination of organic acids is HPLC-UV/vis and for some of them the enzymatic methodology. For polyphenols is HPLC-UV/vis. Samples of musts, monovarietal wines, stabilized blended wines and cavas with 3 and 7 months of second fermentation are being studied. Data will be treated using boxplots to see the predominant compounds and chemometric tools such as Principal Component Analysis (PCA) to establish correlations and Partial Least Squares (PLS) for predictions between samples. By the moment, results in Pinot Noir grape variety shown that quality A present high levels of tartaric, malic, citric and succinic acids in musts and wines and there is observed a decrease in citric acid and an increase of succinic acid during the second fermentation. The results of Xarel·lo grape variety shown lower levels of tartaric acid than in Pinot Noir grape variety. Nevertheless, quality A present high amounts of this acid. Qualities A and B present similar levels of malic acid but in quality A slightly higher. For citric acid no noticeable changes are observed from must to cava of 7 month. Quality A present higher levels of succinic acid. Lower values of malic acid and higher values of lactic acid are observed in qualities C and D, due to, the malolactic fermentation in both varieties and there is observed a decrease of tartaric acid from wines to cavas, due to, the tartaric stabilization. In conclusion, malic and tartaric acids are the most important compounds in the quality of cavas. This involves that the futures cavas will be able to age more time.