Influence of nitrogen supply on colorimetric parameters of Lugana wines

Abstract

Color is one of the main qualitative parameters of a wine. As a matter of fact, immediately after having opened a bottle of wine, color, even before aroma and taste, is the first sensorial parameter to be evaluated by the consumer It can change according to various factors depending on the characteristics of the grapes or on the different production and storage processes. This study aims to evaluate the color differences on Lugana wines that are fermented with different yeast and nitrogen supply. Lugana wines were produced with 2021 vintage grapes. Wines were produced with a standard protocol with two different yeasts: Zymaflore Delta e Zymaflore X5 (Laffort, France). Winemaking was carried out in triplicate. During alcoholic fermentation of the must, when H2S appeared, additions of various nitrogen supply were made. Four different nitrogen nutrients have been added: inorganic nitrogen, organic nitrogen, a mix of inorganic and organic nitrogen and organic nitrogen with an addition of pure methionine. Subsequently the wines were subjected to accelerated aging at 40°C for 30 days. Color parameters of wines were evaluated thanks Color P100 (Nomasense) colorimeter and expressed in CIELab coordinates. Colorimetric differences were expressed through ∆E parameter. We found significant differences among wines fermented with same yeast and supplemented with different nitrogen supply. No significant difference was attributed to yeast strain. Colorimetric analysis showed that the addition of inorganic nitrogen produced the greatest colorimetric difference with the control wine. The ΔE values of the samples which included the addition of inorganic nitrogen even with the addition of methionine, are significantly different from the control samples which did not foresee any addition of nitrogen to the musts. Furthermore, despite an impact of accelerated aging treatment on colour, relative differences among samples remained constant. This study provided a first insight into the influence of the different nitrogen supply on the color of Lugana wines. The CIELab colorimetric analyzes carried out showed that inorganic nitrogen nutrition leads to Lugana wines of different colors with higher ΔE values.  Further studies should investigate whether these interesting differences should be attributed to nitrogen nutrition alone or other enological variables and extend the tests to other white and red wines. The present work was supported Laffort, France.