Effect of Low-Frequency Ultrasonication on Red Wine Astringency

Abstract

Wine tastes better with age because of a complex chemical reaction among sugars, acids, and phenolic compounds. This study investigates if applying ultrasonic waves to wine would significantly reduce its perceived astringency levels. Ultrasonic (US) waves were applied to samples of a young Cabernet Sauvignon using a 24 kHz ultrasonic processor and sonotrode probe by varying time,, and amplitude at three levels. To objectively assess the relationship between the US waves and astringency, physical and chemical analysis was carried out that confirmed the underlying assumptions. While the pH of the treated samples decreased slightly, there was no change in color (Hunter CIE Color L*a*b*). Total Phenolic Content (TPC), Total Anthocyanin Content (TAC), and Tannin Concentration (TC) were significantly different (p ≤ .05) among all samples, indicating the impact of sonication on astringency causing components. Additionally, Fourier Transform Near Infrared (FT-NIR) spectroscopy confirmed that there were notable changes in the spectra, attributed to tannins, of wine after the application of sonication in comparison to untreated wine samples. The perception of astringent flavor was evaluated by (i) expert wine tasters and (ii) untrained panelists (n = 60) who were able to clearly distinguish between treated and untreated samples (p ≤ .05) and preferred sonicated samples (180 sec, 100% amplitude) over the control samples, supporting the hypothesis that sonication reduces the astringency of red wine.