Pear Juice - WARNING!
David Llewellyn
This is just a warning I feel I should put out there to anybody thinking of making pear juice.
I have just had a nasty experience, which by swift action and good luck turned out to be not nearly as nasty as it could have been.
In early October we pressed and bottled quite a lot of juice from Conference Pears, our first time doing this. The juice was deliciously smooth, rich and sweet – too sweet probably for a lot of people. 2 to 3 weeks later, the bottles started exploding. Naturally we assumed it was yeast action due to inadequate pasteurisation, and we then assumed that because of the low acidity perhaps higher temperatures were needed. To cut a long story short, after 36 hours of frenzied internet searching and corresponding, it seemed we found the answer! Namely, that it was not yeast at all, but rather a particular bacteria – Clostridium acetobutyricum/acetobutylicum/butyricum (don’t know which exact spelling).
Thanks to the expertise of Keith Goverd, he identified this as the problem, which is characterised by an odour of ‘vomit’ from the affected fermenting bottles, which was what we had. Apparently this bacteria can only thrive at high pH – The pear juice had a titratable acidity of 1.35g/l malic equivalent, and had a pH of, we estimated, about 4.7. Keith’s recommendation was to decant all the juice, disgard any fermenting bottles, bring the acidity of the ‘good’ juice up to 3.5g/l malic equivalent using a mix of malic and citric acid, and rebottle and re-pasteurise. We did this, and now we’ll hope for the best.
I’m not assuming just yet that we’re out of the woods – I wont sell the juice just yet til some time has elapsed and it seems the bacteria is no longer active. Rather than posting about the story at a later stage when I feel the problem has safely been put behind us, I decided to post now, just in case there may still be somebody considering making pear juice.
In the end we lost about 10% of the juice to the bacteria. My guess is that probably the whole batch would eventually have succumbed to the activity of the bacteria, but we were fortunate in catching it at an early stage. This was helped by the fact that the 750ml bottles we used were the light-weight, quite weak bottles, and I believe that if the juice had been filled into stronger bottles we may not have had our first exploders until a greater proportion of the bottles had developed the problem.
In the end, nobody poisoned, no injuries, no recalls! So if this remains so, it’s a happy ending as far as I’m concerned, and it’s a lesson learned!
David Llewellyn
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Andrew Lea
>
> Namely, that it was
> acetobutyricum/acetobutylicum/butyricum (don�t know which exact spelling).
>
> Thanks to the expertise of Keith Goverd, he identified this as the
> fermenting bottles, which was what we had. Apparently this bacteria can
> 1.35g/l malic equivalent, and had a pH of, we estimated, about 4.7.
> fermenting bottles, bring the acidity of the �good� juice up to 3.5g/l
> malic equivalent using a mix of malic and citric acid, and rebottle and
A disturbing tale! In case anyone is wondering why the pasteurisation
failed to stop it, the answer is that pasteurisation of juice as we
normally do it is designed just to knock out fermenting yeasts and
lactic acid bacteria. It does not kill mould spores and more critically
as here it does not kill the spores of Clostridia which are very heat
resistant (typically you need several minutes boiling, or retorting
under pressure, to do that). But the fundamental reason the spores could
germinate is that the pH was too high in this case.
This is a common story for tomato juice and puree which typically run at
pH 4.5. It is usually assumed that fruit juices of pH < 4 are 'safe',
though since David told me this story I have been doing some digging and
found a report of pear juice at pH 3.9 being affected. I have never
heard of it happening in apple, and it took me by surprise that it could
happen in pear. Thanks to Keith (an ex Long Ashton colleague of mine)
for identifying it and to David for making it more widely known. The
message might be to check that all juices (pear and apple) are at pH <4
and maybe even pH <3.8
Andrew
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michael
fermenting from an initial pH of 3.9,and the above discussion has me
somewhat worried.I have added the appropiate amount of sulphite for a
natural yeast fermentation,and with the help of some heat to stop
night time temperatures falling below 50F,they all seem to be
fermenting slowly,though one batch of perry is extremely slow.This
year,I have not had enough latish acidic apples,such as Dymock Red and
Browns Apple to reduce the pH down from 3.9,and I have not yet quite
felt the need to add malic acid.
Is there any advantage in pasteurisation over sulphiting,apart from
some makers aversion to any addition of sulphite?
Michael
On Nov 16, 1:36 pm, Andrew Lea <y...@cider.org.uk> wrote:
> On 16/11/2010 09:23, David Llewellyn wrote:
>
>
>
> > Namely, that it was
> > acetobutyricum/acetobutylicum/butyricum (don t know which exact spelling).
> > Thanks to the expertise of Keith Goverd, he identified this as the
> > fermenting bottles, bring the acidity of the good juice up to 3.5g/l
David Llewellyn
fermentation in itself takes care of this bacteria
David L.
--
Andrew Lea
making where as David says the alcohol takes care of such things.
Andrew
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Daniel Print
I posted back in September details of an experimental Williams Pear 'perry', and I thought I'd reply to this thread with details of its initial success, then failure...
It went a wonderful creamy milky colour as it fermented (using an ale yeast) giving off a pleasant peary, sweet smell, which boded well I thought. The fermentation slowed and it started to clear from the top of the demijohn, I then noticed that the lower half of the gallon, wasn't just cloudy, but was a clumpy white, jelly like precipitate. I tried to rack off the juice last night and was glad I didn't taste too much, as it not only smelled like vomit, it had the consistency of it too.
Reading the warning below, I'm now reassured that I am not the only person running a side line in vomit-flavoured drinks. I don't check ph in my cider making, as I normally use a high proportion of Bramleys to give lots of acidity, going by the rule of thumb that if it's tart, its good.
So, my Perry experiment for 2010 is not a keeper. Maybe I could boost the acidity in the juice in future, or stick to just using the pears as an ingredient in my early windfall scrumpy
Dan
--- On Tue, 16/11/10, michael <michael....@yahoo.co.uk> wrote:
> From: michael <michael....@yahoo.co.uk>
> Subject: [Cider Workshop] Re: Pear Juice - WARNING!
Cheshire Matt
I've had to chuck 2 batches from last year due to opalesence, which I've read is due to an extending film yeast issues. One batch this year is very pear drop, which I hope will soften. Another of last year's batches I've racked to an oak barrel to try and do something (I don't know what exactly) to it.
On the plus side, another 2 batches this year have dropped totally clear within a week or so. Weird fruit :)