A cider-maker had concerns about the high level of acidity in his cider. He had measured the pH and got a result of 3.1, which is low for this style of drink. He said he thought it tasted “a bit acidic” as well. He couldn’t think why the acid would be high (and the pH low) and wanted to get a sterility test done as he figured this would tell him what was going on.
We discussed the production process: it was a normal ferment although no preservatives such as sulfur dioxide had been added. Typically his ciders were pasteurised at the end of fermentation; this one had finished fermentation a couple of weeks prior to us seeing the sample and was to be pasteurised once this problem was sorted.
We suggested that it would also be good for us to check the pH result he got, plus test the acidity and the concentration of both malic and acetic acids. Upon receiving the sample and tasting it, we got a whiff of acetic acid. We tested for that and it was high – well over 1 g/L. The sterility tests also showed a large presence of acetobacter, the likely cause of the high acetic acid (volatile acidity).
It seemed the lack of any antibacterial preservatives and low alcohol content were enough to give the ubiquitous acetobacter a chance to get going in a very short time and to cause some havoc. And obviously the cider-maker had an issue with his pH meter. His result of 3.1 was way out – we got 3.64. So his concern of low pH was actually not the issue. And of course, at this actual higher pH of around 3.6, bacteria can grow more readily than at 3.1. This was part of the real issue.
Of all the other non-wine fermented beverages, cider is the most like wine, although with some obvious differences in composition. This implies that the types of problems that arise in winemaking can also cause problems in cider. One major difference between wine and cider is the alcohol content. A high level of alcohol (typically from say 12% to 16% in wine) does inhibit microbial spoilage to some degree, although few winemakers leave out sulfur dioxide as a preservative due to its beneficial action against bacteria and anti-oxidation properties. The alcohol level in cider is more typically around 4% to 6% which is far less inhibitory for the types of microbes that can be found in fermented beverages.
As this cider-maker usually pasteurises his ciders as soon as ferment is over, he hadn’t come across this problem before. He vowed and declared he wouldn’t let his cider sit around between end of ferment and pasteurising ever again!
We also recommended he get a new pH electrode or meter.