126 Port anD the Douro
In the weeks prior to the harvest, winemakers representing the major Port shippers
will tour the region, visiting farmers, doing deals and taking samples of grapes from
different plots to monitor development. Baumé (a measure of sugar concentration in
the grapes which roughly corresponds with potential alcohol), pH and total acidity are
crucial readings, but tasting grapes or juice is increasingly gaining ground as a method
of determining optimum ripeness. All grapes destined for the production of Port should
legally be above 11 degrees Baumé, although in a poor vintage I have come across grapes
from the altos (high vineyards) and Baixo Corgo with readings as low as 9 degrees Baumé,
similar to the neighbouring Vinho Verde region. In the Cima Corgo and Douro Superior
potential alcohol levels are usually between 12 and 14% by volume but can occasionally
be much higher. In excessively hot years, the shrivelling or raisining of grapes as they
hang on the vine can be a problem, especially with heat-sensitive varieties like Tinta
Barroca. which can reach 20 degrees Baumé or more. In these warm conditions, levels
of natural acidity are usually low, although an excessively hot, dry summer can cause the
vines to close down and produce unbalanced wines with a ‘green’, under-ripe character.
Depending on the source of the grapes total acidity may be as low as 5 grams per litre,
and pH levels sometimes exceed 4.0. This will warrant correction once the grapes have
reached the winery.
Given the terrain, it almost goes without saying that picking in the Douro is carried
out entirely by hand. Grapes were traditionally cut into large, coarse woven baskets (cestos
da vindima) with a capacity of up to 75 kilos. These would then be carried to the adega
by a regimented line of pickers, egged-on by a small band of musicians. Although cestos
are still used by some smaller growers, nowadays they are usually loaded on to trailers
and towed to the adega by tractor. Following the centralisation of Port production in the
1960s, the majority of grapes have been transported to the winery or adega in 1,000-
kilo steel bins known as dornas. These are usually emblazoned with the name of the
owner (co-operative or shipper) and lent out to growers during vintage. They are far from
Cestos, old and new