Browning susceptibility of commercial monovarietal white wines under accelerated oxidation conditions: correlation with compositional data and effect on total phenol content and radical scavenging activity

Abstract

A set of seven commercial white wine samples (W1–7) produced from the cultivar Malagousia and obtained directly from the cellar 4 months after winemaking were subjected to accelerated oxidation (55 °C, 11 days). The correlation of browning susceptibility with compositional data, as well as the effect on phenolic content using simple assays, and the radical scavenging activity (DPPH·, ABTS·+) were examined. Calculated browning rate constants (k) varied by 1.03–2.66-fold among pairs of samples. Thus, despite the fact that samples originated from the same cultivar, differences were significant in some cases. No correlation was observed between browning and total or free sulfur dioxide, total iron, copper or other compositional parameters (total phenol, total hydroxycinnamates, total flavanol, catechin, epicatechin content, etc.), except for the grape reaction product/caftaric acid ratio (0.802, p = 0.017). The later suggested that wine must elaboration might be important for white wine oxidative stability, and its contact with oxygen should be avoided or minimized. Addition of ascorbic acid at the maximum level detected in the tested wines (70 mg/L), to one of the samples free of ascorbic acid but containing the highest level of total (100 mg/L) and free SO2 (30 mg/L) among these, had a negative effect. However, one of the samples containing ascorbic acid (33 mg/L) was resistant to oxidation. The molar ratio of free SO2 to that of ascorbic may affect browning susceptibility; therefore, the use of ascorbic acid should be made with caution. Chemometrics could be useful to provide prediction of browning susceptibility in relation to compositional data. The radical scavenging activity decreased with a significant correlation between the loss in DPPH· scavenging and ascorbic acid content (r = 0.845, p = 0.008). The changes in total flavanols did not follow a clear trend, whereas the spectrophotometric monitoring of total hydroxycinnamate was not informative due to interferences with browning products. Present findings are expected to be useful for those involved in white wine production.