pH of cider in maturation

[HEW]

I have heard the rule of thumb that fully fermented ciders with a pH >3.8 should be acidified by blending with higher-acid batches so as to make sure the pH is <3.8 during months-long maturation in bulk storage. 

I tested a small batch of excellent cider that has been ageing without any acidification and found it to be excellent. Its pH is 4.1. It has received 50 ppm SO2 before fermentation and 50 ppm SO2 after fermentation. It had aged on its lees for more than 6 months. Is it stable? Is my assumption that ciders with pH >3.8 are not stable for bulk maturation incorrect?

[Mark Venton]

Sometimes it will. Sometimes it wont. There are so many variables. The safe assumption is that it needs to be between 3.2 and 3.8. A lot is down to what it is stored in too. EG Air contact - stabilty of temperature etc

[Richard Reeves]

Your 100 ppm total so2 will have virtually no antiseptic/antioxidative/protective value at that pH. You would need a free so2 number in the range of your total add to achieve anything close to microbial stability which would put your total so2 number required to achieve said ~100 ppm free somewhere north of the stratosphere. Perhaps this is why ciders at pH 4.1 and their ilk are described as "Not stable for bulk maturation", i.e. the amount of total so2 required to protect such a cider would be perhaps toxic and probably illegal, depending on your jurisdiction/circumstances. On the bright side, ~100 ppm total so2 might (maybe) prevent a post-bottling malolactic ferment, but I wouldn't count on it, certainly not in perpetuity, and certainly not at that pH. However at that pH and given the low initial so2 addition (a.k.a. no none nada free so2)  it's likely already gone through the ML ferment. Storage temperature would play an important role with that.

Please forgive me for asking, but I'm curious about your description of a cider reading 4.1 pH as "excellent". Having made a few of those myself (my orchard is in such a hot dry climate, 105 degrees just today for instance, that I rarely get a must below 4.0 pH with the bittersweets, 4.2-4.3 is my usual), I have found them to be uniformly unpalatable post-primary fermentation but prior to acid adjustment ( I actually no longer do this, but for a few vintages I wanted to "see what Mother Nature was giving me"). I of course realize one man's "unpalatable" is another man's "excellent", put is it possible that the method by which you measure pH is flawed, and your true pH is somewhat or even significantly lower than you believe?

I suppose it's possible that you are dealing with fruit this both high acid and high pH, which would lend it palatability. I've heard of that happening, I've just never seen it here (read "Provincial").

Best, Richard