pH rise in fermentation.

[Bob Honey]

We pressed a batch of Browns 2 weeks ago, a bit past their best but
worth a go. SG 1.042 pH 3.1. At that pH I did not use SO2.
The juice has fermented enthusiastically on wild, or our cider barn
yeast and is now SG 1.004, but pH has risen to 3.5/3.6. I have tried
to find reference to rising pH in Andrew's books, but cannot find it
for these circumstances, although I am useless at finding things!
The taste is perfectly clean, though acidic. No off flavours at this
stage.
We intend to blend it with our Dabinett juice (pH 4.2) but are nervous
to do so in case anything untoward is happening. This might have
happened in past pressings but if it has we have never noticed.
I am inclined to add SO2 now, as fermentation is nearly complete.
Any observations or advise gratefully received!

Bob

[Andrew Lea]

On 29/10/2014 12:24, Bob Honey wrote:
> We pressed a batch of Browns 2 weeks ago, a bit past their best but
> worth a go. SG 1.042 pH 3.1. At that pH I did not use SO2.
> The juice has fermented enthusiastically on wild, or our cider barn
> yeast and is now SG 1.004, but pH has risen to 3.5/3.6. I have tried to
> find reference to rising pH in Andrew's books, but cannot find it for
> these circumstances, although I am useless at finding things!

I don't think I mention it. Some yeasts generate acid during
fermentation, some metabolise it. So pH can go down or up. In your case
it seems like the latter. An alternative possibility in this mild
weather is a co-occurring malo-lactic bacterial ferment but 2 weeks is a
rather short time for that to have an effect.

Either way I wouldn't worry about it.

> I am inclined to add SO2 now, as fermentation is nearly complete.

SG 1.004 is too early. Wait until fermentation is fully complete and the
yeast is settling. Otherwise the SO2 will be bound by excess
acetaldehyde and it will just be wasted. SO2 should be added before or
after fermentation. Never during.

Andrew


--
near Oxford, UK
Wittenham Hill Cider Portal
www.cider.org.uk

[Bob Honey]

Thankyou Andrew.
Bob

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