Effect of non-protein factors on heat stability of Chilean Sauvignon Blanc wines
Protein denaturation in white wines results into a hazy suspension with precipitate formation, affecting negatively their commercialization. The aim of this study was to identify a number of non-protein factors of wines, which exhibit a modulating effect upon haze formation and interfere with protein precipitation in white wines, applying stepwise multiple regression analysis. The influence of intrinsic non-protein factors, including surface and groundwater quality, on protein haze formation assessed by the heat test was studied. Experiments were performed on 18 Sauvignon Blanc wines from six Chilean valleys. The influence of non-protein factors (pH, electrical conductivity [EC], total and volatile acidity, alcohol, free and total sulfur dioxide, total polyphenols, and chloride, sulfate, K, Na, Ca, Mg, and Fe concentrations) on haze response was evaluated by means of multiple regression analysis. Significant contribution (p < 0.05) of EC, sulfate and Fe concentrations to protein haze was found. Due to multi-collinearity between sulfate and Fe concentrations, the multi-linear model of haze response was reduced to: Haze = -184 + 2.95 x [Protein] - 62.3 x [Fe] + 0.17 x EC (r a = 0.901). Electric conductivities of wine and surface water were correlated (p = 0.037); good correlations were also found between sulfate concentrations in wine and surface water (p = 0.003), and groundwater (p = 0.022). No correlation was detected for Fe. This study elucidates that protein haze formation in white wine is a multi-factorial process. Iron, EC, and sulfate, in addition to protein itself, have to be considered as factors that modulate wine protein hazing.