Now that the grapes are coming in non-stop during the day, our 3 robotic treading lagares are in constant use. One of the key steps in the winemaking process for us is adding the brandy that arrests fermentation resulting in the higher sugar levels that give Port its characteristic richness. When and how much brandy to add is one of the critical decisions that I have to take on quite a regular basis.
We estimate the yield of must (juice) we will get from the grapes in order to determine how much brandy, we call it AD, to add to that volume. We traditionally work with volumes based on the pipe measure of 550L (a pipe is the term for a standard size wood barrel used for ageing Port). As a rule of thumb, 750Kg of grapes yields 550L of grape juice.
However, this year as the yields are below normal (low yields generally equate to greater concentration) and with considerably greater sugar in the grapes, extra care has to be taken in order not to add too much AD at fortification.
Indeed greater sugar concentration requires a longer fermentation time to arrive at the required sweetness (at which to fortify), implying a greater level of fermented sugar and corresponding alcohol. This greater level of fermented alcohol therefore means less AD is needed in order to achieve the required alcoholic strength of 19%v/v.
Apart from the lower AD requirement, which occurs from a greater proportion of fermented alcohol, the lower yields (and therefore less juice) also result in less AD being required at fortification.
In light of the two factores above, I will put in slightly less brandy than would normally be indicated by my charts. Better to put in less now and correct later, because if you put in too much you’re stuffed!
This year’s berry concentration, together with the longer associated fermentation time (>fermentation aromas) results in greater all round Port concentration, and can be an indication of wines with excellent potential, although reduced quantity.