Asoleo

What it is

Asoleo (from Spanish asolear, sunbathe) is the sun-drying process where harvested grapes are laid on straw mats in the open air to concentrate sugars. Mainly applied to Pedro Ximénez and Moscatel in Andalusia, as preparation for sweet sherry production.

The process takes seven to fifteen days depending on weather and target sugar concentration. During that period the grapes shrivel into small raisins, with sugar content rising from ~220 g/l in fresh grapes to 400-500 g/l in dried.

How it works

Step by step:

1. Harvest at full ripeness, usually August-September. PX is picked above 22% sugar (Brix).
2. Lay out on straw or palm-leaf mats in open air, sun-side up
3. Turn daily to ensure even drying
4. Cover at night dew or rain, to prevent spoilage
5. Assess sugar concentration via refractometer and visual check
6. Press when target sugar level is reached (typically day 7-15)
7. Vinification comparable to sherry: fermentation to ~9% alcohol, then fortification

The drying happens mostly in Montilla-Moriles, about 100 km north-east of Jerez. The climate there is warmer and drier, ideal for reliable drying without spoilage risk.

Why Montilla and not Jerez

Three reasons:

1. Climate: Montilla has less maritime influence, drier summers
2. Soil: chalk (Albariza) soils are comparable but less suited to the specific microflora that sun-drying needs
3. Tradition: Pedro Ximénez has held home-grown status in Montilla longer

Many sherry bodegas in Jerez buy Montilla grapes, dry them there, and transport the concentrated must to Jerez for solera ageing. A bottle of “PX from Marco de Jerez” therefore often contains Montilla sun and Jerez ageing.

Where asoleo gets misread

The standard explanation sometimes frames asoleo as “raisin-making”. Half-true: the grapes shrivel into raisin texture, but the goal isn’t raisin production. The dried grapes still get pressed and vinified, not sold as raisins.

Second misconception: asoleo would only be for PX. Moscatel undergoes the same process, and in more limited form Palomino in some vino dulce naturale productions. PX is by far the main end product.

Frequently asked questions

How long does asoleo take?

Seven to fifteen days for PX, five to ten days for Moscatel. Shorter in drier weather, longer in damper. Producers measure Brix daily to determine the target endpoint (~50% sugar content).

Does asoleo exist outside Andalusia?

Comparable techniques exist elsewhere: appassimento in Italy (for Amarone, Vin Santo, Recioto), passito generally, and in limited form in France (Vin de Paille from Jura). Asoleo specifically refers to the Spanish process in Andalusia.

What’s the difference between asoleo and appassimento?

Similar result (sugar concentration through drying), different technique. Asoleo happens outdoors on mats. Appassimento happens more often indoors in ventilated drying rooms (Italy). Asoleo is more intense and faster (1-2 weeks), appassimento is slower (2-4 months) and more controlled.