Part IV of the Cuatrogatos Wine Club Didactic Selection is upon us, bringing with it the oxygen action of oxidation.

One of the things that is so striking about the wines of Jerez and Sanlucar (and indeed a number of other regions around Spain) is the coexistence of three distinct forms of ageing: biological ageing under the flor (Parts II and III), oxidative or “traditional” ageing where there is no flor (today) and not forgetting wine without flor or oxidation (Part I).

Each form of ageing brings about different effects. In biological ageing, the living flor protects the wine from the oxygen in the air and steadily eats away at the alcohol, sugar and glycerine, reducing the volatile acids and leaving behind the hay bale acetaldehydes. The result are wines that are literally “fino”, potent and with bready, nutty, herbal and floral flavours and aromas.

In “traditional” ageing, these gears go into reverse. Residual alcohol, glycerine and sugar all increase as evaporation (the angels taking their share) does its work, and colour and volatile acids increase due to the interaction of the wine with air and barrel. Now the result is oloroso, a fragrant (oloroso literally means “aromatic”), acidic, caramel flavoured wine, or, where the wine has also had biological ageing, an amontillado, which can combine the characteristics of both to make some of the most sought after wines of all. And here we have two such wines, both from the boys at Callejuela.

First up for didactic reasons is El Cerro oloroso. A really beautiful, elegant old oloroso, and a perfect exponent of the qualities that oxidative ageing can bring out. A dark brown in colour as you can see (I love the clear bottle presentation) and on the nose the aromas are all burned sweetness: fruits and nuts singed to an inch of their life. Then on the palate it has that sharpness of acidity and then a big density of flavour, again half burned sugary raisins and walnuts, with a turn to the bitter but not too much. Real solidity to the middle part of the palate and then a remarkably clean finish. No astringency or bitterness as it hangs around the palate. Lovely.

And then that is a nice contrast to an amontillado from la Callejuela, the “Origen Calificada”. Now here maybe the contrast is forced and the comparison between categories isn’t quite fair – el Cerro has a fair bit more age than the Origen and a better comparison would probably have been La Casilla amontillado.

But the point here is to compare the effect of that biological ageing compared to the oxidation and that comes across really nicely in this wine, maybe better than it would in a much older amontillado. On the nose and amongst the roasted almonds and hazelnuts you get church furniture, and the palate is that touch finer and fresher at the start, and almost comes across as grassy fresh at the finish.

And here endeth the Didactic Selection, as they say.

But “what of the “other” category, the “palo cortados”?” you may ask, as you suddenly smell a rat and suspect Sharquillo’s selection is one bottle short. Worry not: it really isn’t so. “Palo cortado” has become a very successful category commercially but really is not a uniquely different category of wine. Without wanting to burst anyone’s bubble the wines available as palo cortados would, in days gone by, have simply been sold as olorosos. In fact, some leading bodegas have even told me that their bottlings of palo cortados are brought about by identifying and selecting the finer butts of their olorosos. This isn’t to knock their quality – a finer oloroso is a wonderful thing. Indeed, on that score, El Cerro could easily pass as a palo cortado if sales ever dip below the tiny production that it has.

And besides, there is a limit to the number of bottles you can fit in a case, and once you have started there could be no stopping. I hope these few posts are just the start of a long voyage for someone, and I would encourage anyone who has got this far to thing far outside and beyond this box, and to search out all the many, many styles and makers and explore the wines of Jerez. I did and I have never looked back.