The Montilla–Moriles grape-growing area is located in southern Spain
and according to Hidalgo (1999), it belongs to zone V ofWinkler's classification,
with an sum of effective degree-days exceeding 2597 °C and
maximum day temperatures above 40 °C during the grape ripening period
(López, Moreno, & Medina, 1988). Pedro Ximenez (PX) white grapes
are the predominant variety cultivated in the region and can be harvested
in variable degrees of industrial ripeness from the second half of August
to early October each year. This allows five different types of wines to
be produced from the grapes by using the traditional procedures