Some Factors Involved in Browning of White Wines

Increasing temoerature, oxygen content, or pH increase the browning rate. Enzymic oxidation does not appear to be a factor. Sulfur dioxide inhibits browning, but does not prevent it. Grape seed tannin decreases the browning rate while tannic acid increases it. Iron increases the browning rate more than copper, with the effect of the two metals additive rather than synergistic. Citric acid decreases the browning rate at all levels of iron content tested. The varietal effect is the predominant factor with all the above factors merely modifying it.