caps popping like crazy in new pasteuriser

[Wayne Bush]

I have been using smaller pasteurisers until now, but today I used for the first time a vigo bath pasteuriser.  While heating the cider to 64 degrees C, I blew the caps off a quarter of the bottles in the pasteuriser!  In the past it wasn't unusual to blow a cap or two out of a large batch, but I've never experienced anything like this.   The cider and bottles I was pasteurising are the same as I've always used (bottle fermented with 13 grams per litre of sugar in 750 ml bottles and backsweetened prior to pasteurising).  The caps were also from a new supplier but I can't detect anything wrong with them although the interior silicone liner is slightly thinner than the caps I used previously.  I used the same grifo capper I've always used.  The fill level of the bottles hasn't changed.  Only thing I can think of that has changed about the process, other than the caps, is the speed at which the pasteuriser works.  The vigo model seems to heat faster than the small pasteurisers I used previously, increasing the heat of the bath about 1 degree C per minute.  Could the speed at which the bottles are heated to the desired temperature cause a difference/increase in the pressure in the bottle as opposed to slower heating, and cause so many caps to blow?  I guess it is theoretically possible there was more dissolved CO2 in the base cider I used that has resulted in greater pressure in the bottles, but I don't know any reason why that would be the case.  Any ideas/suggestions welcome.  I've stopped using it until I can figure out what is happening--can't really throw out a quarter of my production.  Thanks, Wayne

[rhand...@rockisland.com]

Interesting, how did the other bottles do, did you check for leaky bottles i.e. bottles with tiny bubbles coming up? The only other things might be the carbonation levels and fill, have you calibrated the fill to match the stated volume?

 

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[Wayne Bush]

Richard thanks for your reply.  It is interesting that with my previous caps I often saw a little fizz around the caps.  With the new caps, I didn't see any fizz at all around the caps of the bottles that didn't blow off.  So maybe the previous caps released a bit of pressure before blowing off, and then effectively resealed as the bottles cooled.  I can only hypothesize.  I am ordering some of my previous caps to do a side by side test so I can either eliminate or confirm the caps as the cause, and if its not the caps I'll keep looking for other possible causes.  

[Richard Torrens (lists)]

In article <96fdbb90-6771-454f...@googlegroups.com>,

Wayne Bush <butter...@hotmail.com> wrote:
> I have been using smaller pasteurisers until now, but today I used for
> the first time a vigo bath pasteuriser. While heating the cider to 64
> degrees C, I blew the caps off a quarter of the bottles in the
> pasteuriser!

Are you leaving a small air gap in the bottle? Liquids are virtually
incompressible so if over-filled heat expansion would have nowhere to go.
That might be enough to account for the difference between different caps.

--
Richard Torrens, South Perrott, Dorset, UK.

[Wayne Bush]

Yes--filling to the absolute minimum for 75 cl bottle.  Tried today in old pasteuriser that heats more slowly with same result; more convinced the caps are the problem.

[Terry Chalk]

To me, your numbers seem about right (i.e. 13g/L should be about SG 1.005 or about 2.5 vols when converted to CO2). The reason for replying is that I did a trial some years ago to see if I could find the pressure limits of commonly recycled 12oz/330ml bottles. With bottles carbonated to 2.5 vols, I was able to get the temperature up above 90C (I am at 1000M, so getting the waterbath temperature much higher than this means trying to defeat the laws of physics).

Anyhow, all the bottles survived this, except one which blew its cap at around 90C. According to Andrew Lea's Carbonation Table, the pressure would have been around 13 bar or 190psi at 90C. At 65C pasteurising temperature, you would get about the same pressure if carbonated to a bit over 4 volumes of CO2. The popped cap may have been poor capping on my part or it may be the sort of pressure where caps fail.

So, I just throw this out there. Have you opened any of the "good" bottles to see if the carbonation seems to be around 2.5 vols as overcarbonation could be another explanation..

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[Marcus Wiebe]

Hey Wayne,

We had similar issues and it was a new box of caps.  It was the same manufacturer however the caps were made a different country and they seemed to not seal as well as our other ones. 

Hope this helps,

Marcus