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Mohammadi, Xanyar

University of British Columbia

Sulfur dioxide (SO₂) is a widely used wine preservative that can protect the wine from oxidation and microbial spoilage. However, in the last two decades, the wine industry has been investigating possible alternatives to reduce or even replace it due to its adverse effects on sulfite-sensitive individuals. In this study, the possibility of using a continuous Pulsed Light (PL) system for the inactivation of spoilage microorganisms to reduce the use of SO₂ in red wine and its effects on anthocyanin condensation reaction was investigated. Model wine solutions containing malvidin, cyanidin, and delphinidin-3-O-glucoside were prepared with the presence of (-)-epicatechin and acetaldehyde. The solutions were subjected to PL treatment with 2, 4, and 8 J/cm² energy and stored at 10 °C. The loss of anthocyanin during the treatment and the aging period fitted the first-order reaction model. Delphinidin-3-O-glucoside suffered the highest loss, while malvidin-3-O-glucoside showed the lowest loss. Furthermore, the PL treatment significantly influenced the kinetics of anthocyanin loss during the aging period. PL treatment led to the formation of new isomers of anthocyanin ethyl-linked (-)-epicatechin in the treated samples that were not detected in the control samples. The color characteristics of the model solutions were affected by the PL treatment and the formation of ethyl-linked products. Red wine samples with 0, 25, and 50 mg/L free SO₂ were subjected to PL treatment with 0, 2, and 4 J/cm² fluences. Physicochemical properties and microbial count were monitored for four months. The results showed that PL treatment could significantly reduce the number of LAB and yeast. After the aging time, the samples with no SO₂ added showed a higher pH, lower acidity, TPC, and anthocyanins. In addition, the total color changes were low and could not be detected by human eyes. According to the findings in this study, the PL treatment could significantly inactivate wine spoilage microorganisms with no noticeable effects on the color. As a result, the use of SO₂ can be limited. However, to prevent the oxidation of anthocyanins and maintain the quality of wine, there is still a need to use a reduced amount of SO₂.

Text

2023-01-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/80467

Food Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/