Volume Loss

 "I've got a bone to pick with you!", she said. 

This sounded ominous but I waited for the details. It turned out that my friend had followed my simple wine method to the letter.

"I used four 1-litre cartons of juice and the sugar syrup addition was made up to exactly a litre too. The fermentation went fine, but when I went to bottle it I only got four full litres and one about three quarters full. I thought I was making five litres of wine. Where did the rest go?"

OK. This is normal. To a first approximation, unfermented wine is just sugar dissolved in water. There's a popular misconception that when you dissolve sugar in water the volume doesn't increase. The truth is that the volume does increase, but not by as much as the volume of added sugar. The sugar molecules occupy the spaces between the water molecules. It's a neat exercise in packing but it's not perfect and the total volume does increase.

Fermentation breaks down the dissolved sugar producing CO₂ and ethanol. Some CO₂ stays in solution but most escapes as bubbles. This reduces the total liquid volume, but the effect is masked while the bubbles are present, because they take up some space, so the surface level stays artificially high. This is why volume loss appears to happen quickly, towards the end of fermentation when the bubbling stops. 

Another cause of volume loss is yeast growth. The initial yeast addition is less than a teaspoonful. But the final sediment is many times greater and largely comprises dead yeast cells. Where do they come from? Well, they are organisms and so are made of carbon, hydrogen, oxygen (which come from the sugar) and also nitrogen from the fruit juice. It follows that if you remove dissolved molecules into a sediment, the volume must decrease. Again, this is masked, because the sediment also takes up space.

All of which explains that volume loss is to be expected. Now, what to do about it? Rather than top up to get that fifth litre, I prefer to capture four full litres and one 75cl bottle either for immediate drinking or, if a bit cloudy, for cooking. Waste not, want not

Racking wine for stability and quality

Most ex-pat plonk is drunk young, often within a week of it falling clear at the end of fermentation. Some even before that, when it is still bubbling and full of suspended yeast. Extremely young wine doesn't do you any harm, by the way. In some parts of Poland, cloudy fermenting wine is even served on tap, in the bars. I tried it when last there, and wasn't especially impressed. The yeasty taste was almost acceptable but the visual resemblance to calamine lotion was a definite turn-off. No. Received wisdom correctly says that finished wine should be matured for a time before drinking. But even if you don't have time to mature your wine properly, at the very least you should separate it from its sediment at the end of fermentation. This process is called racking.

Most books on winemaking advocate siphoning the wine from the fermenting vessel into the storage vessel. This is best practice if the fermenter is bigger than 10 litres and heavy to lift. (Though better still is to ferment in a plastic barrel with a fitted tap). But if the fermenter is 10 litres or less, simply pouring it carefully into the new vessel has several advantages:

• It is much quicker, reducing the risk of oxidation
• The pouring action helps release dissolved CO₂
• Dissolved CO₂ can form bubbles in a siphon tube and stop the flow
• There is less equipment to sterilise and to wash up
• Performed carefully, the waste is no more than with a siphon.

After racking, always top up the storage vessel before sealing it. Use wine from a previous batch if you have some available (and if it is sound). Alternatively, use cool boiled water, though this obviously dilutes the wine reducing its ABV. Don't use fruit juice as this can restart fermentation, preventing clearing and pressurising the bottle.

Blending wines for balance and quality

Last year, I made close to 50 litres of red wine in two batches using my semi-pulp method. The first batch was made with black cherries and the second with brambles (blackberries). It would have been nice to use a blend of fruits in the fermentation but not possible because cherries are a summer fruit and brambles come ripe in autumn. By Christmas time, both wines were coming along nicely. Both were 14% ABV, dry and clear. Both still young and fruity of course, especially the bramble.  

Now, here's the interesting thing- the cherry tasted and smelt like cherries and the bramble like brambles. Who'd have thunk it!? In each case, the fresh fruit completely dominated the supermarket grape juice, as you might expect. Also, the bramble was brasher, with more acid and tannin than the cherry. More than was good for it, if I'm honest. The obvious solution was to blend the wines together for further maturing. After a few experiments, I settled on a 60:40 cherry to bramble mix which is now sealed for maturing in several 5-litre bottles. 

Next Christmas, I'll offer it around in the hope that someone says- I'm getting hints of Black Forest gateau and maybe some fruits of the forest too. And steel, of course. Never forget the steel.