Browning of White Wines and an Accelerated Test for Browning Capacity

A standardized test for the browning capacity of white wines was developed. A portion of the wine is treated with 1 g of bentonite per 100 ml under nitrogen so that the developed brown pigment will stay in solution. Portions of the treated wine are incubated in sealed tubes with 25% or more headspace well sparged with oxygen and separately with nitrogen for 5 days at 55°C. The absorbance at 420 nm remains nearly unchanged for the N2-sparged samples and under oxygen measures wines9 relative capacity to brown oxidatively. Evidence is presented that a wine well protected from oxidation is largely prevented from browning whereas a wine treated by adding d-catechin is considerably increased in its capacity to brown by this test.