Pasteurisation bottles

[The_italian_cider_maker]

Hi all!
I've bottled last week my cider batch at about 1,010 sg. When the sg will be at 1.005 I would pasteurize them.
The question is... How to do it?

I would prepare a box where heat the water till 65°C and then I'd submerge the bottles (their temperature is around 10°C) into it and count 15 minutes. Is it correct? Or should I put the bottles in cold bath and then heat to the temperature target? How many PUs will be obtained with the first mode? My target is to obtain at least 40/50PUs (i remember a post made by @Chalkyt talking about an ideal PUs of max50) to be sure the yeast will be killed.

And then... Could I repeat the procedure waiting the bath heated again?

Thank you all!

 

[Chalkyt]

What you are proposing sounds pretty much on the money.

FYI I have attached a paper that I posted some time ago. It goes into a lot of detail but should answer any questions that you have. Also, trawl through Pappers' sticky at the top pf the forum, and have a look at Jim Rausch's "Cooler Method" (16 April 2018) and Bembel's post on Pasteurisation Time and Temperature for Cider (May 11 2016).

I use a souse-vide heater in a 10 litre bucket to hold the temperature at a constant 65C and do five 12 oz (330ml) bottles at a time (i.e. I just do three pasteurisation "sessions" of 5 bottles each since I get 15 bottles from a 5 litre batch of cider) so that too much time isn't spent getting bottles in and out at the right time). There is nothing special about the bucket and batch sizes. It simply suits my working space.

I monitor bottle temperature using a bottle of water with a cooking thermometer in it by noting its temperature at each minute which I find a bit easier than Bembel's approach of noting the time at certain temperature points, but both methods work pretty much the same and let you calculate PUs achieved in each time period.

I have a simple spreadsheet to do this, just as a check to make sure adequate pasteurisation has been achieved (an example is attached). However, as a general rule, 10 minutes in the bath does the job as heating up accounts for about half the PUs then the residual heat when the bottles are removed and cool down accounts for the rest. The elapsed heating and cooling time per batch is around 20 minutes. Your 10C bottles may well need the 15 minutes in the hot water bath that you suggest, but monitoring the bottle temperature is worth doing just to make sure.

My bottles are normally at room temperature (about 20C) and I have found that pre-heating them in hot water from the tap (as Jim Rausch suggests) gets them to a starting temperature of around 40C, which simply speeds up the process as 60C (where pasteurisation starts) is reached in only a few minutes after I put them in the bucket. The bucket water temperature drops a few degrees but it quickly recovers. Heating on a stove top would work just as well.

 

[The_italian_cider_maker]

Thank you @Chalkyt, clear and helpful as usual!
You're great!