John Downie

Jim Streeton reflects on the compostion of juices from different apple varieties and the consequences if these are fermented into cider.

There is a wonderful diversity amongst apples and, since juice is the major part of the fruit, there must be great variations in that too. Within the juice, there is fructose, some sucrose, acid, tannin and other things beyond my knowledge which make up the soluble matter, and which in general parlance get lumped together and called 'sugar'.
 
So, for a start, how much sugar is there in the juice? A hydrometer suspended in the juice of ripe Bramley apples will generally read in the region of 1040 - 1045, though many factors may affect this. 1040 might be better expressed complete with its decimal point, thus, 1.040; and it means that a given volume of juice weighs 4% more than a similar volume of water at a certain temperature - often 15C⁰, 59F⁰. The temperature aspect need not concern us. The hydrometer is not an easy instrument to read accurately. You are supposed to look at it with your eye in the same horizontal plane as the surface of the liquid being tested - easier said than done - and the instrument is usually calibrated in stages of 0.002. So, unless you are very careful, you will be dealing in approximations anyway, and a few degrees either side of the specified temperature will make little difference.
 
Returning to the Bramley juice, if it shows 1.040 on the hydrometer, a gallon of it would weigh just over 166oz. (A gallon of water weighs 10 lb - 160oz, then add 4%.) The difference is a mere 6oz but, in actual fact, our gallon contains more than 1 lb of sugar; the reason being that when a pound of sugar in dissolved in water it displaces 10 fluid oz of liquid before it adds 16 oz of weight. To be very exact about it, one pound of sugar dissolved in water to a total volume of one gallon will produce a reading of 1.0375.
 
In the course of many years of making cider I have never come across apples with an original gravity (og) of materially less than 1.040. But there are some - and not necessarily those you might expect - that are very much higher. So far as I am aware, the highest that Thomas Andrew Knight found was Golden Harvey at 1.085. But I have found higher myself. On 1st Oct 2001, I gathered 24lb of the ornamental crab, John Downie from a tree in Rotherhithe, London, the og of which was at least 1.090. Again, on 15th Sept 2004, I collected 29 lb from the same tree and once more the og was 1.090. Unfortunately, the tree is no longer there. It used to be in a sheltered and sunny garden and it was immediately next to a paved car park, and perhaps this resulted in a more than usually concentrated juice. I cannot give a list of varieties and the og of their juices as many of the apples that come my way are wildings, but the og's of what I do see - wildings and varieties - are frequently in the 1.050s, above 1.060 is not uncommon and occasionally one comes across something over 1.070. All this implies that a gallon of apple juice contains at least a pound of soluble matter, quite possibly two, and sometimes more than that.
 
As to variation within this soluble matter, I am not qualified to say beyond the obvious - there is great variation in flavour, and there are considerable differences in the processes of fermentation.
 
On the latter point, to take an example, my neighbour's Brownlees Russet juice had an og of 1.060. When this was allowed to ferment on its own yeast it went down to 1.002, a difference of 58 points, and all one has to do to calculate the approximate percentage of alcohol present by volume is to divide that difference by 7.5. Answer, 7.7%, so we shall have to be careful when we drink it. That might be regarded as typical of a high gravity dessert apple, but very different results might be obtained by going to an extreme. Juice of ripe, wild crab-apples - Malus sylvestris - might have an og 1.050 and if allowed to ferment, apparently stop at 1.015.  This alone demonstrates what a difference there is in the composition of the juice without even bothering to taste the stuff. Cider made from M. sylvestris alone is all but undrinkable - though some crab-apples in a mix of other apples can be desirable.
 
This brings us to another matter. There is frequently more sugar in cider than is apparent at first sight.And if this is augmented by granular sugar to produce sparkle it is not difficult to go over the top and cause bottles to explode. To get an idea of how much soluble matter can remain in the finished product, there is a clear example if we look at grapes and dry wine. The grape juice might have an og of 1.070 and, at the end of all perceptible fermentation, the wine might have a gravity of 0.995 - 75 points the difference which suggests 10% alcohol.
 
Now let us consider a mixture of 90% water and 10% alcohol. Firstly, we need to know that pure alcohol has an og of 0.800 - that is to say its weight is 80% of that of water So, if we have a litre of the mixture, there will be 900ml of water which will weigh (rather obviously) of 900mg, and 100ml of alcohol with a weight of 80mg. Add the two together, answer 980mg or 98%of the weight of water, which is, of course, the same as a hydrometer reading of 0.980.
 
The finished wine was 0.995 so there is a difference of 0.015. Whatever this is in the wine, it is almost certainly not fermentable and will cause no trouble following bottling. However, if these 15 points were comprised of some sort of sugar it would imply there was more than 6 ounces to each gallon - enough to blast any bottle to eternity. There is always a residue of unfermentable material in apple juice so that fermentation may stop at around 1.015 or anywhere below that figure, and the cider may be absolutely stable - but then again it may not. Usually there is some secondary fermentation in the bottle so that it is generally unwise to bottle at much above 1.010 unless you are certain the cider is stable. The effervescence of champagne is produced by permitting the fermentation of the equivalent of 4oz of sugar per gallon in the bottle, and this can produce a pressure of 90 lb per square inch - and this, if I may say so, is much more than the home cider-maker should go for.

Jim Streeton