cooler pasteurization

[tlc]

After reading other posts about bottle bombs (scares me) I decided to make me a cooler just for pasteurizing. I bought me a cooler and filled the lid with spray foam and then I drilled a 2.5" hole in the lid, glued in a 2"pvc coupling (perfect fit for the sous vide diameter, so I could add my sous vide to it so I could maintain a constant temp. I then cut the lid in two pieces so I will be able to add the bottles without removing the sous vide. It's a pretty sweet set up and it didn't take that long to make if anyone is interested I will take some pics. Now after all that I have a couple of questions on the process for low heat cooler pasteurization. I plan on getting the bottle temp to 150 deg for 10 min (Chalkyt's advice on a recent post and I might add this man is an excellent resource of informaton). I've never actually used a sous vide so I will tell you my plan and if anyone sees any flaws or a better way of doing please let me know.
OK...Here is the plan. I will heat the water in the cooler to 125 deg and then add (12) 12 oz bottles and set the heat on the sous vide to 155 deg (accounting for bottle insulation) to get the cider to 150 deg. Once thermometer in open bottle reads 150 deg I will start the timer and leave them in the cooler for 10 min. After that I will turn off the sous vide and remove the bottles from the cooler and let them cool back down to room temp and then while they are cooling back down I will add another 12 bottles to the cooler and start the process again. A question I have is since the cooler water will be around 150 deg for the 2nd batch should I remove some water and cool it back down or will adding the bottles in at 150 deg be an issue since the room temp bottles should cool the water bath down some. Another option would be to leave water at 150 deg and pre heat bottles in sink to 125 deg before adding.

 

[Chalkyt]

That should work fine. At 150F you will be generating about 5 PUs per minute (i.e. 10 minutes will give you 50 PUs plus whatever you get during cooldown). However from 140F upwards you will also be generating some PUs so you will end up with more than 50, but it doesn't really matter since I haven't found that "overpasteurising" at these low temperatures has any effect on taste.

Pre-heating the bottles really is optional. It will speed the process up a bit if time is an issue and you have any concerns about thermal shock, but I would be happy just putting the second batch at room temperature (say 65F) straight into the cooler (at 150F) as this is what I do.

I don't pre heat my bottles and find that it only takes 4-5 minutes for them to get up to 140F which is where pasteurisation starts then only another 2-3 minutes to get to 150F. It is a slow leisurely process that sometimes involves tasting for quality control purposes! (I do five bottles at a time in 15 litres of hot water so I am dealing with smaller volumes and so less heating load than you).

You may find that the sous vide struggles a bit to get your larger volume of cooler water back up to temperature quickly when subsequent bottle batches are put in (sous vides are usually about 1000-1500W and designed to cook a bit of fish or steak etc in a relatively small water bath), but that shouldn't be a problem as you will be monitoring when the 150F is reached and work from there.

Anyhow there is now plenty of evidence that even 30 PUs is enough for cider. If you take the bottles out as soon as they reach 150F, they will have accumulated about 20 PUs then during cooldown at least another 20 PUs or so. The ten minute dwell time really is just to have a margin of safety to generate plenty of PUs at 150F in what is a fairly imprecise process.

It might be worth doing a bit of monitoring as per Bembel's process (see post May 11, 2016) just to see what level of pasteurisation you are achieving. (i.e. use del Veccio's formula to calculate what PUs are generated each minute or at each temperature point).

 

[tlc]

I did a test run yesterday to see about heat up and cool down time and heat up time was roughly 1 deg per minute from 140f to 150f with my 1200w sous vide. I think with the 150f at 10 min after I get to 150f I'll have generated over 50 pu's so I feel good about that. I can do 16 bottles in my cooler set up so I will just get the water to 150f for the other batches and not pre heat them since I will be at room temp to begin with. I left my thermometer in the water after the sous vide shut off and after 20 min it was still at 145f so I will just remove them and set them on the counter so they will cool down faster. I feel pretty good that this set up will be both safe and effective for getting the pu's without bottle bombs...Thanks and have a great day.

 

[Chalkyt]

Yep, all sounds good!

 

[tlc]

Chalkyt...I did the PU calculation according to your chart and it looks like I can get 66.1 not including cool down which is probably even 10 more. Could you please check my math when you have time and make sure I did it right. With the sous vide set at 151f, It took 10 min to get from 140f to 151f( temp was increasing 1 deg per minute) and then I held the temp at 151 for 5 min. After 5 min I removed the bottles and set them on the counter and they slowly came back down to temp. I didn't monitor how long it took them on cool down since I had already achieved 66.1 pu's if I did my calculation right. I was able to do 12 bottles at a time in my cooler set up which is nice.
Thanks

 

[Rick Stephens]

I would bet money that once your internal temps hit 150, if you pulled the bottles and set aside to start another run you would have plenty of PUs to accomplish your task. Sitting at 150 for an additional 10 minutes is, IMHO, all extra, and unnecessary time.

 

[tlc]

I would bet you are correct to so I actually took it down to 5 min and i'm pretty sure I'm still over doing it according to the calculations.
Thanks for the advice

 

[Chalkyt]

Yep, Rick is correct. I have attached a file that I posted on 1 Feb. It is an update of an earlier post and refers to some useful websites. If you look at Figs 9, 10, 11, they will be similar to what you are doing but without the extra five minutes of soaking time. You will see that a satisfactory level of pasteurisation is achieved without the extra time at 150F (i.e. just heat up, remove and cool down). In particular, as far as pasteurisation levels needed, have a look at a link to a recent Washington State University paper that was posted by Jaypkk on 4 December.

 

[tlc]

You guys are a great source of information...Thanks