What acid level am I generally shooting for?

Acidity and pH
The acidity is controlled more by the variety of fruit than the climate. Acidity has two aspects - total acid and pH - and both are useful to know. The total acid relates well to our perception of acid flavour, while the pH relates better to various aspects of fermentation biochemistry. These two are connected but not in a simple way, although the acidity always goes up as the pH goes down and vice-versa. In terms of total titratable acid (as malic), we should be looking for 0.3 - 0.5% in a cider juice. If the total acid is too low, the pH will be too high and the fermentation will be susceptible to bacterial infections. If the total acid is too high, the pH will be low enough to safeguard against infection but the final cider will be unacceptably sharp to the palate and may never be pleasant to drink. Acidity can be measured by titration - details will be found in any good wine-making book. Kits for measuring titratable acidity are available.

Measurement of pH has to be done by a dedicated 'pH meter'. These used to be very expensive, costing several hundred pounds, but modern 'chip technology' has now brought them down to the range of £30 or so. However, beware the very cheap pH meters which are sold in garden centres for soil testing - these are not accurate enough for cidermaking because we need to measure to at least the nearest 0.1 pH unit or it is not worth making the measurement at all! Narrow range 'pH papers' (e.g. pH 2.8 to 4.2) are now available cheaply from some home brewing suppliers and are a good substitute. A desirable juice pH range for cider-making is say 3.2 - 3.8. At higher pH the fermentation will be subject to microbial infection and at pH 4.0 or above this can lead to serious flavour problems. Many traditional bittersweet cider apples tend to be high in pH which is why they need blending with more acid fruit, preferably before fermentation. That is one reason why bittersharp apples, such as 'Kingston Black', have been regarded as near perfection in terms of their composition for single-variety cider making.

If you cannot measure the acidity or the pH, taste the juice instead. Trying to ignore the sweetness and the tannin, judge whether the juice is insipid, balanced or sharp. If insipid, and you have no other juice for blending, malic acid may have to be added in steps of 1 gram per litre (0.1%) until the balance is improved. If the juice is too acid, and you cannot blend it out, you may have to encourage a malo-lactic fermentation to reduce it (see later), or you can add a little calcium carbonate to neutralise it, in 1 gram per litre steps.

Other juice parameters, such as tannin, are difficult to measure, but only people using a high proportion of bittersweet fruit are likely to suffer from excessive tannin and this can usually be detected by taste although the juice sugar does tend to mask it. Deficiencies here can be corrected after fermentation, however. The purpose of blending before fermentation is to give a juice as close in composition to the 'ideal' which was described in the previous article. Although this may not always be possible, it is always worth the attempt at least in terms of sugar and acid levels. Blending after fermentation is a worthy and useful art but it cannot correct a gross biochemical imbalance beforehand!

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