FOAMING IN GRAPE JUICES OF WHITE VARIETIES

The foam capacity of grape juice of white varieties (Macabeo, Xarel.lo , Parellada, and Chardonnay) was related to juice characteristics to a chieve the quality of raw material of sparkling wine production or to avoid foam problems in fermentation deposits. Grape juices came from t he Penedes Region and were obtained at industrial scale in three conse cutive years of harvest. Juices with a maturation index [ratio between soluble solids ((d)egrees Brix) and titratable acidity (grams of tart aric acid per liter of juice)] ranging from 4 to 5.5 had high foamabil ity. Chardonnay juices had the best ripeness characteristics, and as r esult, these varietal juices showed the best foam capacity. It was als o established that foaming properties also depend on several compounds (proteins, sugars, polyphenols, and alcohols) that can decrease the s urface tension of the juices and, thus, increase foamability. Foam cha racteristics of grape juices could be predicted using equations based on simple enological parameters related to ripening and could be adjus ted with practices such as SO2 addition and acidity correction.