Pasteurisation and PU's

[Andrew Lea]

Following Charlotte's posts (and since it's such a rainy day!), I
thought it might be helpful to explain the way in which the
'pasteurisation unit' PU concept can apply to ciders and juices.

You can read the definition of PU in many places but here is as good as
anywhere http://www.redpostltd.com/support/science#PU so I don't need to
repeat it.

Empirically, for fermented beers, ciders or the like, the PU requirement
has been determined many times to be in the region of 50 PU. So,
supposing you were pasteurising in a tank at 67C, the values in the
equation would be PU = 50 and the expression 10^((67-60)/7) conveniently
reduces to just 10^1 or simply 10. So the time required is 50/10 or 5
minutes. In practice, since there is a finite heating time and a cooling
time, and any temperature above 60C contributes to the lethal effect,
you would easily have put in enough PU's if you just take the bottle
contents up to 67C and let it cool naturally. But you could hold it at
67C for 5 minutes if you wanted to be 'belt and braces'.

If you were lucky enough to have a flash pasteuriser and chiller
operating at 81C, then the relevant expression becomes 10^((81-60)/7)
which conveniently reduces to 10^3 or 1000. Hence the holding time
required becomes just 50/1000 = 0.05 minutes or just 3 seconds. This
clearly shows the exponential relationship between temperature and
microbial death.

Now, consider a juice. Empirically it has been shown that a cloudy apple
juice requires a PU value of around 500 - 1000 (a clear juice might
require less). This is much higher than a cider because there is a
higher yeast load and the lack of alcohol means that the yeast is not at
all stressed but is 'raring to go'. So, if you tank pasteurise up to
74C, PU is say 500 and the relevant expression is 10^((74-60)/7) which
again conveniently reduces to 10^2 or 100. So the holding time required
is 500/100 or 5 minutes. Again, because of the contribution of any
heating and cooling time which is above 60C, you will get plenty of PU's
if you bring the juice up to that temperature and allow it to cool
naturally. But again you could hold it at 74C for 5 minutes if you
wanted to be 'belt and braces'.

Again, suppose you had a flash pasteuriser operating at 81C as in the
cider example. The holding time then becomes 500/1000 or half a minute
which is actually a typical value for that type of operation. At 88C it
becomes 500/10000 or back to 3 seconds again.

Now, at root of all this are empirical values which have been determined
by many years of practical experience. But they are consistent with a
little bit of theory and the PU concept which allows you to rationalise
the effect that different pasteurisation temperatures will have and the
time you need to get comparable effects.

I hope this helps some people.

Andrew

--
Wittenham Hill Cider Portal
www.cider.org.uk

[Alexander Peckham]

Very helpfully. Thanks Anrew.

[Charlotte Traynor]

Thanks Andrew,

Once again above and beyond the call of duty! Much appreciated; I'm sure it'll take awhile to fully comprehend it all, but yet another rainy day so it's back to school!

Charlotte

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[Jason Mitchell (Ashridge Cider)]

Hi Charlotte and Andrew. Isn't the "standard"pasteurisation temp and time for apple juice 20 mins at 70 degrees C? This presumably means the core temp in the middle of the bottle too.
I know all the pasteurisers Vigo sell have this programmed in to their electrical control unit.
I am always keen to do the minimum heating for obvious reasons.
So if the figures you quote Andrew are correct, then lots of apple juice is being well over cooked!
Cheers, Jason

[Michael Cobb]

I have a pasteuriser from VIGO bought about 8 years ago so may not be the
current model. It is basically a timed thermostatic water bath for
bottled cider/juice. It does not measure the temperature in the bottle so
it may be that the time alllows the temperature
to pass through the bottle into the liquid. I have had a few failures in
recent years and have found that the thermostat has failed so I now use a
temperature probe in bottle which from what Andrew says will allow shorter
total times by allowing for the rise and fall times.

Michael Cobb

>
> On 08/06/2012 14:40, Jason Mitchell (Ashridge Cider) wrote:
>> Hi Charlotte and Andrew. Isn't the "standard"pasteurisation temp and
>> time for apple juice 20 mins at 70 degrees C? This presumably means the
>> core temp in the middle of the bottle too.
>> I know all the pasteurisers Vigo sell have this programmed in to their
>> electrical control unit.
>> I am always keen to do the minimum heating for obvious reasons.
>> So if the figures you quote Andrew are correct, then lots of apple juice
>> is being well over cooked!
>> Cheers, Jason
>

> Well now this was the whole point of me posting about PU's yesterday, so
> that you could work it out for yourself!
>
> If you plug 70C for 20 minutes into the equation, it goes like this:
>
> PU = 20 * 10^((70-60)/7)
>
> If you calculate that expression it gives 537 PU's. Which lies in the
> range 500 - 1000, just as I said a typical cloudy juice needs (I gave a
> worked example for 500 PU's to keep the maths nice and simple).
>
> QED.

[Andrew Lea]

On 08/06/2012 14:40, Jason Mitchell (Ashridge Cider) wrote:

> Hi Charlotte and Andrew. Isn't the "standard"pasteurisation temp and time for apple juice 20 mins at 70 degrees C? This presumably means the core temp in the middle of the bottle too.
> I know all the pasteurisers Vigo sell have this programmed in to their electrical control unit.
> I am always keen to do the minimum heating for obvious reasons.
> So if the figures you quote Andrew are correct, then lots of apple juice is being well over cooked!
> Cheers, Jason

Well now this was the whole point of me posting about PU's yesterday, so
that you could work it out for yourself!

If you plug 70C for 20 minutes into the equation, it goes like this:

PU = 20 * 10^((70-60)/7)

If you calculate that expression it gives 537 PU's. Which lies in the
range 500 - 1000, just as I said a typical cloudy juice needs (I gave a
worked example for 500 PU's to keep the maths nice and simple).

QED.

[Andrew Lea]

On 08/06/2012 14:57, Andrew Lea wrote:

>
> If you plug 70C for 20 minutes into the equation, it goes like this:
>
> PU = 20 * 10^((70-60)/7)
>
> If you calculate that expression it gives 537 PU's. Which lies in the
> range 500 - 1000, just as I said a typical cloudy juice needs (I
> gave a worked example for 500 PU's to keep the maths nice and
> simple).

I have been playing a bit more (since it's still raining here!), with
the effect of 'come-up' and 'cool-down' times (as mentioned by Michael).
It's easy enough to do if you set the equations up on Excel and tabulate
everything for 1 minute increments.

So, for example, assume there is a 10 minute lag in a pasteuriser while
it's heating, between the water bath temperature and the internal juice
temperature. To make it easier, consider only the times for temperatures
above 60C (below that the pasteurising effect on juice will be minimal).

Then it turns out that:

For t=0 at 60C to t=10 at 70C you accumulate 93 PU's
For t=10 at 70C and a 10 minute hold at 70C you are up to 361 PU's
From t=20 at 70C cooling down to 60C at t=40 you end up with a total of
506 PU's.

So, making some reasonable assumptions about heating and cooling lag
times, you still come in at over 500 PU's which is about right for
cloudy juice.

[Wes Cherry]

In my experience, pulling the bottles when they get to 64C gives plenty of PUs -- typically 90 or so. This is with a bath temperature of ~68C and 750mL bottles. The cider in the bottles continues to heat due to the thermal energy in the glass still keeping the cider warm.

I have a little pasteurization computer which integrates the pasteurization equation. I typically pull the bottles from the hot bath when I get to 25 PUs which happens around 64C. Here's an Excel plot of it's output.

[Andrew Lea]

On 08/06/2012 17:17, Wes Cherry wrote:
> In my experience, pulling the bottles when they get to 64C gives
> plenty of PUs -- typically 90 or so. This is with a bath
> temperature of ~68C and 750mL bottles. The cider in the bottles
> continues to heat due to the thermal energy in the glass still
> keeping the cider warm.

Yes that's good for cider. You need more for juice (which I typically
pull at 74C rather than hold at 70C).

>
> I have a little pasteurization computer which integrates the
> pasteurization equation. I typically pull the bottles from the hot
> bath when I get to 25 PUs which happens around 64C. Here's an
> Excel plot of it's output.

Can you explain a bit more about this device? Presumably it's some form
of data logger attached to a digital thermometer, and you can then
download it to a PC? I know these are used professionally, but what
price do they come in at for the amateur / small scale user? Does it
compete with a thermometer and a stopwatch ;-)

[Andrew Lea]

On 08/06/2012 16:57, Andrew Lea wrote:

> Then it turns out that:
>
> For t=0 at 60C to t=10 at 70C you accumulate 93 PU's
> For t=10 at 70C and a 10 minute hold at 70C you are up to 361 PU's
> From t=20 at 70C cooling down to 60C at t=40 you end up with a total of
> 506 PU's.
>
> So, making some reasonable assumptions about heating and cooling lag
> times, you still come in at over 500 PU's which is about right for
> cloudy juice.

Here is a calculated plot of my juice example. To compare and contrast
with Wes's actual recorded plot of his cider example! The general
pattern is much the same though of course the figures differ.

[Wes Cherry]

Can you explain a bit more about this device? 

It's a unit I built using an Arduino.   Arduinos are a little single board computer that can be purchased for $29, but requires user programming.   There is a very large user community with lots of contributed code and libraries and add-on hardware so putting together an Arduino system is much easier than doing it from scratch.   The display was another $25 and the 3 temperature sensors $10 each or a total price of < $100.   I still need to package it up in an enclosure, add connectors for the sensors, etc, bringing total costs to maybe $130.

The three temperature sensors measure the incoming hot water, the bath temperature and the cider temperature in the bottle.   Each second it integrates the pasteurization equation

delta PU = 1/60 * 10 ^ ((T-60)/7) and adds it to the running total displayed on the lower left.   The display turns from blue to green to yellow to red for each stage of the process (blue for under temperature, green when pasteurization units are accumulating, yellow when to pull from the bath and red when total PUs are reached.  

It doesn't have any logging capability yet, though it could easily write the outputs to the USB port and log on a PC/Mac.   In the case of the graph posted earlier I sat and recorded values in a notebook thru the cycle.

I intend to add heater control and maybe logging to a SD card in the future.

I plan on open sourcing the hardware and software for others to make their own.

-'//es Cherry

w...@dragonsheadcider.com

Vashon WA, USA

[Andrew Lea]

On 08/06/2012 18:18, Wes Cherry wrote:
>> Can you explain a bit more about this device?
>

> It's a unit I built using an Arduino ......

>
> The three temperature sensors measure the incoming hot water, the bath
> temperature and the cider temperature in the bottle. Each second it
> integrates the pasteurization equation
> delta PU = 1/60 * 10 ^ ((T-60)/7) and adds it to the running total
> displayed on the lower left. The display turns from blue to green to
> yellow to red for each stage of the process (blue for under temperature,
> green when pasteurization units are accumulating, yellow when to pull
> from the bath and red when total PUs are reached.

That is very neat Wes. Thank you for the information. I am glad there
are people on this list already measuring PU's! In practice I confess I
never have and have just stuck to the 'rules of thumb' that have been
handed down for years! Until the last few stormy days here which have
kept many of us in the UK indoors (and prompted by Charlotte's
question), I had never really thought about calculating them for a
home-based operation. But if you have a thermometer and a clock and
access to Excel (or even just a scientific calculator and pen and paper)
it's not so hard to do.

It seems to me the greatest value is in the 'setting up' phase, since
once you have a 'system' working presumably all the variables stay
pretty much the same from batch to batch (do you find that?). But at
least by taking the measurements initially you can see exactly how many
PU's you are accumulating, and whether your procedure is likely to be
under or over pasteurising.

Incidentally for UK and European readers I did mention a while back the
tale of a pasteuriser I had bought at Lidl (very similar to the cheaper
Vigo ones) when they were on offer a couple of years ago. It had become
faulty and tripped my household RCD's every time it got up to
temperature! I have finally had a warranty replacement sent to me by
Lidl's agents - though some persistence is required to find out how to
do that and it took about 6 weeks! So next time I use it I may be
calculating PU's out of interest for myself.

[Wes Cherry]

Thanks Andrew,

Yes this whole pasteurization monitor is really not all that necessary (except maybe for some litigious reason here in the US!).  I have found each run to be pretty much like the previous one.  I'm sure the bath temp and the ambient temp play into it a bit in terms of the slope of the PU accumulation in bath and out. 

Before I made the controller I sat reading the cider temp every minute and calculating the PUs manually on a calculator and adding them up.     So for every minute I calculated the PU contribution as 10^((T-60)/7).  

 What surprised me was the amount of latent heat in the bottle and how much pasteurization occurred after I pulled the bottles from the bath. 

And a question for you, Andrew.  the Z value (7 in the equation above) seems to be experimentally derived.   I have used 7C, but I'm not entirely clear that is correct.   From 

 http://books.google.com/books?id=6ROLbW8klRsC&pg=PA207&lpg=PA207&dq=pasteurization+units+z+value&source=bl&ots=-21h8HWkTo&sig=Byt_HC9ciQSLaUIAD5vLAIoeYbc&hl=en&sa=X&ei=hADTT_LyG8Tg2QWh2bGDDw&ved=0CE8Q6AEwAA#v=onepage&q=pasteurization%20units%20z%20value&f=false

they state the beer industry uses 6.9C.   Beer has a higher pH and so maybe a lower Z value is appropriate for cider.

It also appears that the Z value is kind of fudgy and even depends upon your pasteurization temperature.   Has any work been done for cider (or sweetened wines) to determine a good Z value?   Same with total PUs desired for cider.    I found this link (without references, from the pretty wonky pasteurizers.info site):

http://www.pasteurizers.info/2009/07/typical-pasteurization-pu-values-for.html

and then this paper suggests that only 3 PUs are required to kill yeast cells in Chenin Blanc white whine to undetectable limits.   

http://onlinelibrary.wiley.com/doi/10.1111/j.1745-4549.1991.tb00151.x/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+on+9+June+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance

It also says 100,000 PUs are required for any perceptible taste difference.    I disagree with this assessment, at least for cider -- I can taste a small but perceptible difference between cider with ~100PU vs unpasteurized in A-B tests.  

-'//es Cherry

w...@dragonsheadcider.com

Vashon WA, USA

[Mike Beck]

It seems that pasteurization is popular choice to stabilize cider. Is there
a reason why few are using sterile filtration as way to stabilize cider? I
have not found a single document that says it strips(filtration) color or
flavors from cider. Outside of the cost of filter media(pennies per gallon)
I cannot find a reason to invest in a "cider cooker". Is there something I
am missing? I notice with many pasteurized ciders that there is a "carmel"
note that goes with them. Not necessarily a fault, but may be getting in
the way of what the fruit is trying to express itself as. We are small
cidery (<30,000L) so there is not a lot of exposure in the Marketplace for
me to worry of blown bottles. Which has never happened in a bottle suitable
for carbonated product.
Mike Beck
Michigan, USA

-----Original Message-----
From: cider-w...@googlegroups.com
[mailto:cider-w...@googlegroups.com] On Behalf Of Alexander Peckham
Sent: Thursday, June 07, 2012 3:33 PM
To: Cider Workshop
Subject: [Cider Workshop] Re: Pasteurisation and PU's

Very helpfully. Thanks Anrew.

[scott h]

Mike,
I am a new, very small producer, and I can only speak for myself when
I say that I am taking the word of Peter Mitchell, whose classes I
attended, who thinks that sterile filtration has more of an effect on
flavor than pasteurization. And sterile filtration isn't really
"sterile" unless everything after the filter is sterilized and
aseptic. In your experience this hasn't been a problem? Also, I think
that bottles exploding are bad business, no matter if you are a large
or small producer!

I propose a blind taste test at the next large cider event and
competition, where pasteurized ciders are tasted next to unpasteurized
and the judges are tasked with picking out the pasteurized samples.
The judges would have to be familiar with cider but not *too*
familiar. (ie, able to recognize a particular commercial cider simply
from the taste, and thus potentially know whether or not it had been
pasteurized regardless of flavor)

To everyone else who pasteurizes, a couple questions: Do you have a
particular procedure for cool-down? Water bath, fans, etc.? And how
about water spots on the bottles, as they dry in a flash once they
come out? Does anyone add anything to the water to prevent this from
happening?
Thanks!

Scott Heath
Tilted Shed Ciderworks
Forestville, CA, USA

> our rules, and principles. Please seehttp://www.ciderworkshop.com/resources_principles.html

[Nat West]

Mike - 

We are small
cidery (<30,000L) so there is not a lot of exposure in the Marketplace for
me to worry of blown bottles.  Which has never happened in a bottle suitable
for carbonated product.

Your last sentence makes me wonder if you're not sterile filtering nor pasteurizing your sweetened products. Clarification?

I
have not found a single document that says it strips(filtration) color or
flavors from cider. 

I am pasteurizing two ciders now. One has bits of ginger in it, fresh-pressed. I want the sludge in the bottle so can't and don't filter. The other had cherry puree added at fermentation and is done with beer yeasts so I like a bit of cloudiness. It's about the presentation in the bottle. I don't want a crystal-clear cider and unless *I* am missing something, you can't easily make a sterile filtered cloudy product. I put an inline sight glass on the input and output of my lenticular filter and based on sight alone, they are very very different products on the in and out.

-Nat West

Reverend Nat's Hard Cider

Portland, Oregon 

[Mike Beck]

Scott,
This article I think tells both sides of the story.
http://www.winesandvines.com/template.cfm?section=columns_article&content=58
981&columns_id=24

> the word of Peter Mitchell, whose classes I attended, who thinks
that sterile filtration has more of an >effect on flavor than
pasteurization.

I am sorry but I could not disagree more with that statement. There is no
flavor or color compounds I am aware that would not slip through the filter,
cider anyways. I (my nose/palette) get a caramel note from pasteurized
ciders. As a grower, I do have a place for apples that get cooked. It is
called a bakery, fantastic process for pies and pastry. My cider will rarely
ever get above 65f until somebody buys it, throws it in their car trunk for
the weekend and lets it bake it the hot sun.

>And sterile filtration isn't really "sterile" unless everything
after the filter is sterilized and aseptic.

I find I can use any number of sterile processes to treat hoses and tanks
prior to filtration. i.e. steam, ozone, favorite chemical sanitizer, etc. A
process that may burn up 20 minutes of your time. I have not had issues
with stability with this process. I have not had an incidence in our almost
9 years at this. (that I was told about anyway)
I have not had the pleasure of taking any of Mr. Mitchells courses, (Not
available in Michigan anyway) is he a grower or cidery owner? I get how
some people want to sell a cloudy cider, fine, do it, not my schtick. I
personally have never been able to get a cider to stay cloudy, tank or
bottle.

OK, I may be slightly slanted against pasteurization. I worked very hard to
not have that process forced on us through government and be forced to apply
it to fresh apple juice. Fresh juice is a popular item here. I think the
pasteurization process negatively affects juice, I think it has the same
impact on cider. IMHO.
Mike Beck
St.John's, Michigan

[Dick Dunn]

replying to both Beck and Scott Heath...
On Tue, Jun 12, 2012 at 03:23:50PM -0400, Mike Beck wrote:

> ...There is no

> flavor or color compounds I am aware that would not slip through the filter,

> cider anyways...

Mike, I think you're right in terms of the compounds _per_se_, but I wonder
what flavor/color might be carried on small particles which are filtered
out. The idea that serious (sub-micron) filtration strips flavor/color is
widespread, but anecdotal as far as I can see. That means it's not a
strong case, since it would be easy to A-B: cider going into a filter vs
cider going out. IOW, one can make a case for why it should be so, but
actual experimental evidence is lacking. Since you've got the filtration
setup, could you give it some serious testing?

>...I (my nose/palette) get a caramel note from pasteurized ciders...

Yes. No question.

>...As a grower, I do have a place for apples that get cooked. It is
> called a bakery, fantastic process for pies and pastry...

(!:-)

>...I get how

> some people want to sell a cloudy cider, fine, do it, not my schtick. I
> personally have never been able to get a cider to stay cloudy, tank or
> bottle.

Would somebody please nudge the gentleman from Berkshire? I believe this
is his cue.

The truth is that cloudy ciders do happen once in a great while (and cloudy
perry, somewhat more often). Plus, a mega-producer wouldn't sell a cloudy
cider except if it were deliberately cloudy (eg, Old Rosie). But there's
this bozotic idea in a few backwaters that a cloudy cider is somehow "more
genuine". I dunno...do pimples make a more authentic teen-ager?

Beck, if all your ciders clear, you've got good process.

Scott Heath wrote (in the article to which Beck replied):

> I am a new, very small producer, and I can only speak for myself when I say
> that I am taking the word of Peter Mitchell, whose classes I attended, who
> thinks that sterile filtration has more of an effect on flavor than

> pasteurization...

OK, Peter has a reasonable rep, but he's a scientist, so he should have
experimental evidence (as opposed to "thinks that..."). Can you find
background references on the topic, maybe in course notes?

> I propose a blind taste test at the next large cider event and competition,
> where pasteurized ciders are tasted next to unpasteurized and the judges are
> tasked with picking out the pasteurized samples.

We've "been there, done that." Every significant judging/tasting I've
done, there have been ciders which have had "cooked" character because of
pasteurization, and I've marked them down. Not to say that proper, careful
processing can't keep it to a minimum, even below perception...but that
over-processing is way too common. And I know I'm not the only judge who
has found this.

Now I think back, Andrew's "Harp Hill" some years back was sweetened and
pasteurized, but I can't recall any cooked, applesauce, etc., character
to it. OTOH, I remember a US producer who had somehow developed a very
paranoid attitude toward contamination in-bottle, so he pasteurized his
cider beyond any reasonable level of PU's...and every time I tasted it,
that fault over-rode any merits it had.

I think my conclusion is that pasteurization -can- be done right...but,
more often than not, it isn't.
--
Dick Dunn rc...@talisman.com Hygiene, Colorado USA

[Jez Howat]

If I may, I'd like to take Mikes argument one step further. I neither
pasteurize or filter. Cider *should* drop to a fairly light haze - not
crystal clear but nor 'cloudy'. I do agree that if you want a cloudy cider
you have to add it in or else try for it. I have seen one cloudy cider this
year where the producer deliberately added some pear juice (which is much
more prone to haze).

For dry or sweetened (with artificial sweeteners) ciders I cannot see the
benefit of either asides from aesthetics. For sugar or juice sweetened
ciders, I cannot see how filtration alone would be sufficient to stabilise.
For highly carbonated ciders, I can see how a bit of yeast at the bottom may
cause a problem once opened due to high action of Co2... so in that regard
filtration would be good (or disgorging the yeast).

I would also like to add to Dick's comment about so many ciders being 'over
pasteurised'. In the UK, there is an increasing number of ciders that have
been 'over' filtered too. Whether the evidence is anecdotal or not, I can
say from my experience of drinking the stuff that it is just as easy to spot
a cider that has been filtered to within an inch of its life as a cider
pasteurised to a crisp. I find over filtered ciders to be degrees of one
dimensional and lacking in body.

Hope this contribution is of some use!

All the best

Jez

[Andrew Lea]

On 13/06/2012 09:21, Jez Howat wrote:
>
>
> For sugar or juice sweetened
> ciders, I cannot see how filtration alone would be sufficient to stabilise.
>

True sterile filtration will do this. Membrane of < 0.2 micron and
*everything* downstream including the bottling must be done in
completely aseptic and 'clean room' conditions. Bottles themselves must
be truly sterile too (eg with peracetic acid treatment and sterile air
blow-off). In the right hands (mostly large operations) it can work
well. I have heard of some spectacular failures though!

[scott h]

Dick,

you say:

We've "been there, done that."  Every significant judging/tasting I've 
done, there have been ciders which have had "cooked" character because of 
pasteurization, and I've marked them down.

Yes, but how many of those ciders in which you didn't detect an off note were actually pasteurized?  That is my point, as others have agreed, and as you say, that it CAN be done well, just isn't always.  I myself am going to set aside unpasteurized bottles and do my own blind test on my ciders...Quality Assurance

BTW I'm still welcoming answers to my questions:

To everyone else who pasteurizes, a couple questions: Do you have a 
particular procedure for cool-down?  Water bath, fans, etc.?  And how 
about water spots on the bottles, as they dry in a flash once they 
come out?  Does anyone add anything to the water to prevent this from 
happening?

Scott 

[Wes Cherry]

Yes, I get water spots, and even an occasional bit of flash rust on the caps.  Both wipe off easily. 

I wonder if some dishwasher rinse aid in the pasteurizer bath would help with the spotting on the bottles.  I have heard vinegar can substitute for rinse aid so that may work as well.

I am bottling tomorrow and will try and report.

I just let my bottles cool naturally.   It takes a bit of experimenting to determine the right time to pull from the bath - at least 1/2 the PUs accumulate on the cool down.

As for pasteurization cooking cider, I think that accurate monitoring of pasteurization temps is essential to prevent over doing it and enabling the Maillard reaction.  When first getting my setup going I overshot and hit 100 PUs and 67c max juice temp on a batch.  Friends with whom i shared this cider in an A-B test could taste a small difference in flavor.  No cooked apple flavors, but the pasteurized cider seemed slighly less "bright" and fresh.  No one felt it was significant though. 

I haven't run A-B tests on my normal 50 PU, ~63c max cider.

-'//es

Sent using the 4S

--

[Dick Dunn]

On Wed, Jun 13, 2012 at 04:26:07PM -0700, scott h wrote:
> Dick,
> you say:
>
> > We've "been there, done that." Every significant judging/tasting I've
> > done, there have been ciders which have had "cooked" character because of
> > pasteurization, and I've marked them down.
> >
>
> Yes, but how many of those ciders in which you didn't detect an off note
> were actually pasteurized? That is my point, as others have agreed, and as

> you say, that it CAN be done well, just isn't always...

I take your point. Yet I say that over-pasteurization is common, in fact
way too common, because I've encountered it too often.

On the other side, how often have I said (in a judging/tasting), "this
cider is thin, lacks life" [or "guts"]? Rarely, and this is why I think
pasteurization is -more- of a problem in commercial ciders.

If I judge (say) 20 commercial ciders, and I get cooked tastes in 5 or
more, then Houston we have a problem, because 20% fault for just one
reason is simply unacceptable. It's the common fault.

[Mike Beck]

Andrew Wrote:
>>>True sterile filtration will do this. Membrane of < 0.2 micron and
*everything* downstream including the bottling must be done in
completely aseptic and 'clean room' conditions. Bottles themselves must
be truly sterile too (eg with peracetic acid treatment and sterile air
blow-off). In the right hands (mostly large operations) it can work
well. I have heard of some spectacular failures though!<<<

My process is a little different....
We use a <.45 micron membrane filter. We sterilize the downstream after
filter and the Bottling line and hoses prior to filling. Our room is clean,
certainly not aseptic. Andrew, you have been here and have seen the rooms.
Clean enough, but no place to do surgery either. Bottles are rinsed with
simple cool well water to remove possible cardboard dust. That water has
living coliform organisms among a couple other benign organisms. (tested
bi-annually) We figure the glass blowing process is pretty aseptic so I
cannot for the life of me think of a reason to sterilize a bottle prior.
Glass containers come well wrapped and clean.
I took my lead from the white wine makers around our peninsulas. Pretty
much the same process much of the Riesling, Chardonnay's, & white blends
use. Scott, your cidery sounds like it is wine country. Is there many folk
in either valley pasteurizing wine?

Dick Dunn wrote...

>>>Since you've got the filtration
setup, could you give it some serious testing?<<<

Here is what I can say without presenting scientific evidence. Cider is no
doubt different pre and post filtering...stripped tasting, maybe a little,
or is it that you have mixed the tank enough, or added a little more oxygen
or whatever. When I come back to that cider 48+/- hrs. later... It seems to
taste like I remembered prior to the process.

I understand wanting to feel secure about the product your selling out the
front or back door. The fruit just seems too fragile to me to subject it to
the heat. I think either process is all about removing layers of risk.
There is really no silver bullet out there. So for the amount of risk I
think is there, I have been hedging my bets with sterile filtration. If I
was a large player out there... I am sure the QA dept. would say we need to
be doing better. Whatever, but for our not even statewide wide operation,
filtration so far has worked out to be economical and feasible. For what
its worth.

Mike beck
St. John's MI-USA

[greg l.]

Mike, do you test for free so2 before bottling, or what addition do
you make?

Greg

[Mike Beck]

Greg,
I do test so2.... I shoot for around 35ppm free so2 depending on pH at
bottling.
Mike

-----Original Message-----
From: cider-w...@googlegroups.com
[mailto:cider-w...@googlegroups.com] On Behalf Of greg l.
Sent: Thursday, June 14, 2012 9:30 PM
To: Cider Workshop

[Andrew Lea]

On 15/06/2012 01:31, Mike Beck wrote:
> Andrew Wrote:
>>>> True sterile filtration will do this. Membrane of< 0.2 micron
>>>> and
> *everything* downstream including the bottling must be done in
> completely aseptic and 'clean room' conditions. Bottles themselves
> must be truly sterile too (eg with peracetic acid treatment and
> sterile air blow-off). In the right hands (mostly large operations)
> it can work well. I have heard of some spectacular failures
> though!<<<
>
> My process is a little different.... We use a<.45 micron membrane
> filter. We sterilize the downstream after filter and the Bottling
> line and hoses prior to filling. Our room is clean, certainly not
> aseptic. Andrew, you have been here and have seen the rooms. Clean
> enough, but no place to do surgery either.

Well maybe I over emphasised the 'aseptic' aspect, though technically
that is the ideal! Trouble is I have seen and heard of far too many
people who have got hold of the 'sterile filtration' buzzword but have
not thought through all its real-life implications and the discipline
required for success. And I have seen some of them later with egg on
their face (not to mention exploding bottles!). If you get a nasty
spoilage yeast like Z baillii (quite common with ciders), then even one
cell per bottle is one cell too many! I would suggest that you have to
be even more careful sterile bottling cider than wine (where it has
become more the norm); at only half the alcohol there is a much lower
'hurdle' for microbial growth.

Yes Mike I have seen your operation and very nice it is too. It is your
attention to detail that makes the difference, and the fact it's been
designed in to what you do, not just some bolt-on afterthought. I also
believe you keep on top of it with microbiological monitoring. The
advantage of pasteurisation is that there are less points of weakness
and can be done pretty much 'by rote' and I honestly think it's
much 'safer' for small scale hobby and hobby+ operations, which are what
many of the people here are doing. Your 30,000L is a good 4 times
greater in volume than many people in the UK who are working to the 7000
litres duty exempt limit. Your scale makes it worthwhile to invest in
good sterile bottling routines; at a smaller scale I doubt it. I have
nothing against sterile bottling at all, and there are many very good
operations and many of the large companies here do it, but I think it's
'horses for courses'.

Picking up a couple more points from a few days back ...

Dick wrote

>> Now I think back, Andrew's "Harp Hill" some years back was
> sweetened and
>> pasteurized, but I can't recall any cooked, applesauce, etc.,
>> character to it.

That is fair comment although on an A/B comparison the pasteurisation is
detectable to me (but more as a flavour rounding which I can live with -
even welcome? - than any overt cooked notes). I have it done on contract
at Pershore College which is a very standard 'batch tank' operation.
Some years ago I did some kitchen experiments tank pasteurising +/- SO2
and I am convinced that free SO2 present when pasteurising is very
valuable at mitigating the generation of cooked flavours (for which
there are sound theoretical reasons too due to trapping of Maillard
precursors), so that is what i endeavour to do also.

Wes wrote

> And a question for you, Andrew. the Z value (7 in the equation
> above) seems to be experimentally derived. I have used 7C, but I'm

> not entirely clear that is correct. It also appears that the Z value

> is kind of fudgy and even depends upon your pasteurization
> temperature.

Z is definitely experimentally derived and is definitely kind of fudgy,
Values determined in the literature range from 5 to 11 depending on the
organisms (or enzymes) concerned and whether or not you are worried
about spores (which are much more heat resistant). Will also depend on
pH and alcohol levels. The oft-used value of 7C (or 6.9) comes direct
from the original brewing work in the 1950's I think. Despite all that,
the theory is useful in allowing you to decide how to shoot for a
particular target (even if you don't know exactly what that target
should be). We talk about 30 - 50 PU as a 'standard' which may have been
true 50 years ago but sometimes you will find as low as 10 PU being
talked about for a filtered beer with a low microbial load.

> Has any work been done for cider (or sweetened wines) to determine a
> good Z value? Same with total PUs desired for cider.

I don't know / can't find any cider data in the public domain. I would
stress the z-value will vary with the organism of interest and the
environment. I would imagine that large companies almost certainly have
or had PU trial data of their own derived in conjunction with
microbiological monitoring, but nowadays most of them will be using
sterile filtration / bottling so it is yesterday's technology for them!

As far as I know all large companies will be working on a 'positive
release' basis - that is, they will quarantine all production after
bottling, take samples for micro testing and only release the batch once
they have proof that it's microbiologically stable. This is standard
food industry practice. It may not prevent the odd rogue bottle slipping
through but it will catch any wholesale batch failure.

There are a handful of literature references about pasteurising / hot
bottling wine. I can let you have them off list. The PU values quoted
range from 0.5 to 20 or so (but beware, some of them are expressed to a
base value of 50C not 60!). This textbook
http://www.amazon.com/dp/0824705904 has quite a good review of the topic
starting at page 425 and by using the 'look inside' facility you can
read much of it. Also has some useful comments on cold sterile bottling!
Remember that cider is a low alcohol wine so is more demanding both for
hot and cold fill than a regular grape wine.

>>
>> and then this paper suggests that only 3 PUs are required to kill
>> yeast cells in Chenin Blanc white whine to undetectable limits.

> It also says 100,000 PUs are required for any perceptible taste
> difference. I disagree with this assessment, at least for cider --
> I can taste a small but perceptible difference between cider with
> ~100PU vs unpasteurized in A-B tests.

I agree with you. However that work seems to be about pasteurising juice
before it's fermented (and the wine later assessed) so it isn't the same
as what we're talking about here.

[Michael Thierfelder]

Wes,

Sorry to resurrect yet another old post but still very relevant I think and warrants just a final retouch on some procedural details.  I am building the macrobin pasteurization bath that both Nat and yourself made.  I think I have it all dialed in except one thing.  I am using the Eemax EX190TC (240V sanitization model) that comes preset at 185F for the output.  This is assuming input from a tank water heater to around 120F.  

My question is, assuming bottles of cider need to get to ~145F, and are starting at room temp of say ~60F.  How does the procedure go?  My guess is that putting room temp bottles in a 185F bath would cause temperature shock failure in the glass no?  If a gentle warm cycle is the method, how are subsequent batches handled? remove hot water and re-warm?

If you could shed some light on the subject and steps you take, I'd greatly appreciate it.

Thanks,

Mike

[Wes Cherry]

Mike, 

You want to recirculate the water in the tank via a pump through the water heater.   The EEMAX units constrict flow quite a bit and require quite a bit of flow/pressure to turn on, so the a simple recirc pump typically used for radiant heat systems won’t work.

I use a 1/2 HP centrifugal pump that I got on ebay.   https://www.dultmeier.com/products/0.851.863.1818.2472/1120  A 3/4 HP would work better.

If you elevate your pasteurization tank by a few feet, it *might* work with a recirc pump (they require a certain suction head pressure to work well)

As long as you use good quality champagne bottles, breakage shouldn’t be a problem.   Immerse the bottles quickly so you don’t get a differential temperature along the bottle.  We blew the bottoms off the bottles a few times that way.

We wait until the bath temperature is ~75C before dunking the bottles.   Bath temp drops to ~50C and then slowly climbs as heat is transferred to the bottles.   By the time we pull, the bath temp is back to ~75C and the next batch can be immediately loaded.

Some people use two or even three baths, with one being heated.   For the two bath situation, the flow is like this:  

Tank A is heated with the EEMAX

Tank B is a warmup/quench tank, initially filled with warm water.

New bottles go into Tank B.   That cools the water and heats the bottles.   They then go into Tank A until enough PUs are accumulated.  Then the bottles go back to Tank B and give heat back to the water, cooling the bottles.    Repeat.  This is obviously more energy efficient, but requires more steps.    With the three bath situation, it’s similar except the warm and cool tanks alternate roles and you can pipeline the process a bit more.    Hope this makes sense.  :)

One more thing - add a Y strainer (or similar) on the input to the water heater.   The EEMAX coils get munged up with random bits and could fail.

-Wes

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[michael thierfelder]

Wes,

Great, that helps a lot, it’s all becoming clear to me now!  

I have a 1 HP Thomsen #4 centrifugal pump I got for transferring and CIP, so hopefully that will do the trick.

I had planned on using 22oz bottles, but have not gotten that far in the production model yet, have not ordered bottles.  I’m assuming I’ll get myself into a jam with your typical crown cap using this system?  Although I know Nat is using swing caps, maybe they are thicker glass? Still trying to put pieces together so please forgive my lack of knowledge.

I like the A/B system, and the Y strainer, Nat mentioned a 30-micron whole-house filter to catch dirt, broken bits of glass, etc.  

Have you ever used output from the water heater to act as hot water sanitizer for CIP?  question I guess there would be is a spray down with 185F water sufficient for sanitization in SS tanks and HDPE IBC’s?  The heater states that it is used for commercial sanitization but wanted to see what you would say to that point as well.

Cheers,

Mike

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[Richard Anderson]

Wes has a pretty good feel for what is required. I would add that you might change your monitoring to two sensors in the test bottle rather than the arrangement you suggest. We do this regularly using 750 beer bottles of German manufacture with no problems. The bottles enter the 75 C bath at about 13 C, while there is occasional breakage That I think is due to a flaw in the bottle not the temperature difference. Like Wes, I think good circulation is essential and wish I was enough of a thermal engineer to design an optimal bath system in terms of time and energy using instant water heater(s).

[Patrick Mann]

Hi Wes
Did you ever get around to posting the schematics and software for your PU monitor? I would love to build something like it.

Patrick

[Chimchim Racer]

Hi Wes,

I second Patrick's request from 5/7/19. Did you ever get around to posting the schematics and software for your PU monitor? It sounds like a really fun project.

Thanks,

Eric

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[Adam]

I have been considering grabbing one of these guys to get a tighter grip on our pasteurizing process, looks pretty slick, records data AND is water resistant:

https://shop.craftmetrics.ca/products/pastuerization-computer

I don't have any affiliation with the company, is just the only reasonably priced professional PU meter I've come across 🤪

[Brendan Kearns]

I've used one for a year, good customer support and computer! 

Brendan

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[Chris Schmidt]

I have one as well, and its terrific. Great support from that team too.

Chris Schmidt

Tod Creek Craft Cider

273 Prospect Lake Rd, Victoria

Crafted on a farm...not in a factory.

Visit our tasting room: Wed to Sat, 10am - 5pm

250-882-1061

Sent from my iPhone 

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[Vince Wakefield]

That’s a lot of money,

must get on with my one, looks like I could make a killing.

Vince

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