A blog and review on all things Sherry. It is about tasting, enjoyment and learning more about the World’s Finest Wine. "Sherry is a thoroughbred" as Javier Hidalgo rightly puts it. Included are the amazing local Brandies and the remarkably good table wines also produced in the province of Cádiz.
These are incredibly
useful gadgets which can measure the health of the grapes at the point of reception at the
bodega. A common problem at harvest time is Botrytis (Greek = grape disease).
This fungus can spread quickly in wet or humid conditions and produces
unsightly grey mould on the grapes which can cause various problems during fermentation.
Botrytis affected grapes: no good for Sherry
A key marker for Botrytis is an increased level
of gluconic acid (GA) caused by oxidation of the glucose metabolism, and a
concentration of over 0.5 g/l of GA can put the must at risk. Biosensors can
measure levels of not only glucose (in degrees Beaumé) but also GA - in
seconds. The biosensors can also measure malic acid, lactic acid, histamine and sucrose in the must. Selected enzymes react to other substances and a transducer converts this to an electrical signal. In 2011
the Consejo Regulador imposed a limit of 1 g/l of GA in the regulations as it
was becoming a problem due to less care in the vineyards as growers struggled
with profitability, and the advent of harvesting machines which cannot detect
Botrytis - yet. Deductions can be made from the sensors’ results, for instance
a grower might not have used sufficient fungicide spray.
Developed by Spanish company Biolán, the
biosensors are not cheap, costing 6,000 euros plus the cost of someone to
operate them, but eventually pay for themselves with higher quality musts. The
arriving grapes must pass a sensor which will spot GA and pass the information
to measuring devices. On detection of excess GA unsuitable grapes can be
removed. In the past the only way of checking for Botrytis was complex and time
consuming laboratory work or an equally time consuming visual inspection.
Biolan Biosensor monitor
It should briefly be pointed out that Botrytis
is used to advantage for certain other wines. The great sweet wines of
Sauternes, Côteaux du Layon or Sélection de Grains Nobles in France, the
Beerenauslesen and Trockenbeerenauslesen of Germany and Tokaji Aszú from
Hungary are at their best with a healthy dose, but not if you want dry wine.