The Effect of Ethanol, SO₂, and Transition Metals on Browning Kinetics in Low‐ and No‐Alcohol Model Wine

Abstract

The study delved into the rate of browning (A420 nm) within a model wine solution, aiming to elucidate mechanisms impacting real product scenarios, including low‐ and no‐alcohol wines. The model wine solutions were prepared by adding tartaric acid, caffeic acid, and catechin into an aqueous ethanol solution containing transition metals (iron [Fe] and copper [Cu]) along with sulfur dioxide (SO2). The results indicated that the model wines without ethanol exhibited the highest browning rates both in the presence (k = 0.0022 day−1) and absence (k = 0.0035 day−1) of SO2. Notably, ethanol concentration showed a negative correlation with kinetic rates in both scenarios: with SO2 (r = −0.9317) and without SO2 (r = −0.9667). The addition of Fe and Cu separately led to a slight elevation in browning, particularly evident with Fe, while adding only Cu exhibited nonsignificant impact. However, their combined addition revealed a marked synergistic effect, rendering the rate notably sensitive to Cu concentration.