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 achieve the quality of raw material of sparkling wine production or to avoid foam problems in fermentation deposits. Grape juices came from the Penedès Region and were obtained at industrial scale in three consecutive years of harvest. Juices with a maturation index [ratio between soluble solids (°Brix) and titratable acidity (grams of tartaric acid per liter of juice)] ranging from 4 to 5.5 had high foamability. Chardonnay juices had the best ripeness characteristics, and as result, these varietal juices showed the best foam capacity. It was also established that foaming properties also depend on several compounds (proteins, sugars, polyphenols, and alcohols) that can decrease the surface tension of the juices and, thus, increase foamability. Foam characteristics of grape juices could be predicted using equations based on simple enological parameters related to ripening and could be adjusted with practices such as SO2 addition and acidity correction. Keywords: Foam capacity; grape juices; surface tension; maturation index; Mosalux