Pasteurising thermometer help.

[charlottetraynor]

Can anyone suggest a thermometer suitable for use when pasteurising.

I had bought a bog standard alarmed digital model but have found it is
already reading some odd room temperature results (about 10*c too
high). I realise the acidity on the probe is quite damaging but as we
are selling the juice I am getting very concerned about its accuracy
at 75*c.

If not a specific model is there some terminology I could be looking
out for?

Many thanks,

[Andrew Lea]

I have used professional K-type food probes and also regular domestic
digital thermometers from kitchen shops. These are intended for food use
so should be quite OK. I have never seen acid corrosion of the probe.
But I would steer clear of units not intended for food.

I suggest you check / replace your batteries or at least check the
contacts are in good order. You should check also that boiling water
shows 100C. Probes can fail and if it's still dodgy you'll need to buy a
new one.

Andrew

--
Wittenham Hill Cider Page
http://www.cider.org.uk

[Orchard eye]

Hi

re temperature,

I was told that it was 70*c , is 75*c the temp that it shouldn't go
over.

I've just pasteurized some dry cider with Dabinet apple juice (with
help of apple juice maker ) and we did it at 70*c

Neil

PS, I'm trying to get away from sacharrin sweetened cider. Also, check
out the colour of this apple juice on my blog
http://theorchardgroup.wordpress.com/

[Andrew Lea]

On 19/09/2010 17:14, Orchard eye wrote:
> Hi
>
> re temperature,
>
> I was told that it was 70*c , is 75*c the temp that it shouldn't go
> over.
>
> I've just pasteurized some dry cider with Dabinet apple juice (with
> help of apple juice maker ) and we did it at 70*c

Cider is not juice! There is a greater antimicrobial 'hurdle effect' of
alcohol so when you pasteurise a cider you don't have to be quite so
hot. Typical values are 75C for juice and 66C for sugar sweetened cider.
For juice sweetened cider you would need a bit more because of the extra
yeast associated with juice. The temperatures given are minima to
ensure safety, not maxima.

Also bear in mind that all these temps are 'rule of thumb'. You can also
pasteurise at a lower temp for a longer time but then you will get a
more cooked result. Conversely HTST pasteurisation temp for tetrapacks
is up in the 90's but only for a few seconds.

Andrew

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

[Dave]

I think what you really need is a calibrated thermometer. I can't
claim that I have always used one, but they do give some piece of
mind, plus the fact that the FSA like to see them being used.
I seem to get through quite a few of them, mostly through damaging the
wire to the probe, never through any acid attack from the juice. Maybe
one calibrated one and a couple of non calibrated ones would be the
answer. Use the calibrated one purely for checking the other two
rather than full time use.
The supply that I was using have changed thermometers due to the wire
faults, but the replacement isn't as good. The alarm has to be reset
every time, the old ones kept the setting.
These are the latest ones, but need resetting every time.
http://www.thermometersdirect.co.uk/acatalog/Dig_Calibrated_Waterproof_Thermometer.html
Which as far as i can tell are exactly the same as
http://www.thermometersdirect.co.uk/acatalog/Dig_Black_Waterproof_Thermometer.html
but come with a certificate. No doubt they just check a batch of them
and the accurate ones get a certificate, I would also guess the
"inaccurate" ones are a degree or so out, not the 10 degree you
mention, and not variable. ie. always read 73 degrees when it is
really 70 degrees.
I have also used the programable oven thermometers on this page
http://www.thermometersuk.com/acatalog/Digital_Thermometers.html. The
probe is very handy to leave in the top of a bottle in the
pasteuriser. I do this with the others, but I have had to make a hole
in the lid of the pasteuriser to do so.
With the thermometer in the first link, I have made a hole in a
plastic bottle lid and sit the whole thing onto a bottle in the
pasteuriser, it does make a difference if the probe is central in the
juice or if it is resting against the glass. There is a temp
difference inside the bottle.
I pasteurise by heating to 70C and holding it for 20 minutes. Andrew
assures me that I can heat to 75C and take straight out, but I have
yet to be brave enough to try this. I don't doubt him, but it is a
very expensive risk for me.
No offense Andrew but I am talking of a £40k "gamble" so I will be
doing a test batch this season just to satisfy myself.

[charlotte traynor]

We are currently using this

http://www.janitorialdirect.co.uk/product/?pid=3373

and like it. reasonable length on the cord and good alarm which it
remembers ^_^ but after what must be about the 200th pasteurisation
batch its reading room temperature way higher than before and higher
than it can be. needless to say this makes us uncomfortable.

i will check the batteries and contacts (assuming you mean where the
batteries connect)

thank you for the links - that site is quite interesting and has
'brewing' thermometers too. i've tried to do a search but can't find
out what data/temperature hold means and when they would be used for.
some of the brewing ones look really interesting but don't specify an
alarm which would be a must. for instance
http://www.thermometersdirect.co.uk/acatalog/Brew_Comark_DT400_Waterproof_Thermometer.html

otherwise the http://www.thermometersdirect.co.uk/acatalog/Brew_Black_Waterproof_Thermometer.html
looks good but wonder whether our problem has been damage to the probe
lead which gets held between water boiler case & lid.

working with a calibrated control thermometer is a good idea. am i
right in think the more traditional glass thermometers are more
reliable and would be better as a control thermometer?

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[Dave]

All the problems I have ever had with thermometers reading wrong have
been due to the lead getting damaged by the pasteuriser lid.
Data/temperature hold is a nasty function that when pressed
accidentally, makes you think the juice isn't heating up. It reads the
temp when you press the button and doesn't change until it is pressed
again. Nightmare!