Pasteurizing With Sous Vide

Every thread I’ve seen on stovetop pasteurizing bottles to kill yeast/stop bottle bombs has involved temperatures of 180-190 F. This seems to have come from cribbing the temperature scheme from milk or apple juice pasteurization, with a fudge factor for poor temperature control.

I work in the food processing industry, and have seen a lot of different methods for pasteurizing beverages (I don’t design them though, just help them run). The literature that is usually quoted for milk/apple juice is assuming flash pasteurization I think- raw product comes into a big heat exchanger, is heated up very quickly, and pasteurized product flows out the other side. This is great for people that have a very high degree of control over that process, and who are packaging said product in plastic, which isn’t suitable for pasteurizing in bottles.

However, home pasteurizing bottles more closely simulates batch or tunnel pasteurizing- this is what is most commonly done in the beer industry (and many others who are using glass or metal packages). Pasteurizing in bottles presents a new set of concerns: bottle cracking from temperature shocks, and exploding carbonated beverages. Both of these issues can be lessened by lowering the pasteurization temperature.

Pasteurization kills microorganisms through a function of temps of 140 F + and time. Why do we always see temps of 180-190 F in milk/juice pasteurization? That’s because they’re using the High Temperature/Short Time (HTST) type of pasteurization. The alternative to this, which is what is of interest to me here, is a Low Temperature/Long Time (LTLT) process. Equal results can be had with lower temperatures held for a longer time, with the benefit of cracking fewer bottles and possibility avoiding some taste changes in your brew.

(For further reading on how exactly the time/temp function is calculated, look up Pasteurization Units. This page (http://sizes.com/units/pasteurization_unit.htm) is a good start.)

The Method: Pasteurization via Immersion Circulator

Immersion circulators, or sous vide cookers, are becoming more mass produced and cheaper recently. I’ve seen them used for mashing on the beer side of things, but I think they are a dream implement for doing LTLT pasteurization at home. They do exactly what you’d want a pasteurizer to do- hold a set temperature with a high degree of precision, circulate the water to prevent cold spots, and have an indirect heat source to avoid shattering bottles.

I just did my first trial run of this setup with a batch of Skeeter Pee that I am too impatient to let sit for two weeks to check for signs of refermentation. It went pretty well- I started with heating 4 gallons of water to 140 F on the stove, to reduce the time it took to get the bottles up to temp. Then I took it off the burner, added my bottles and Anova One, and let them sit at 141 F for 15 minutes (clock started after the water temp recovered). The time was based on there being very little yeast left in the clear Pee, so I aimed for about 12 PUs.

Lessons learned: for Pete’s sake, still wear safety glasses. Closed glass bottles and heat will always pose a risk to your eyeballs. Be careful how you arrange the bottles next to your sous vide unit- I had one that nestled itself right up against the heat source, and it overheated and shattered when I tried to pick it up with tongs.

Overall though, I was encouraged by my low-risk no-carbonation test batch. I’m going to do an experiment with a cheapo batch of cider next, to see if I can narrow down how much time is required to kill an active yeast population, and see if I can spot a taste difference between bottles cooked at 140 F and 180 F.

Anyone else tried this yet? Thoughts?

Great idea! Many of us use our brewing systems to sous vide food. I've essentially got a 15.5g temp-controlled sous vide cooker. And you're right, that would be perfect for pastuerizing. Hope to see some more comments on using low temps and time to safely pastuerize beer/et.al.

This chart might be useful:

Well... assuming we're talking about cider here, and the purpose of pasteurization is to halt an active fermentation to allow for a sweet carbonated beverage -

In the experiments that I've done with stovetop pasteurization I discovered that as the cider heats up the yeast seems to go into hyper drive and pump out a lot of CO2 in a short time. The carbonation level after exposure to heat was considerably higher than when I started.

This makes it even more difficult to judge exactly when to begin the process to achieve the end result you're looking for. Heating the cider slowly will give the yeast more time to carbonate, which will add to the pressure level in the bottle, up to the point where they finally "die".

I agree with your idea that temperature shock would stress the glass bottles more than a slow heat would. That's why the current accepted method is to do two stages, first in hot water from your sink (130° or so), then into the hot pot.

In the end though, it comes down to a risk either way and how good your bottles are.

Edit: This is the thread I made about my experiments:

https://www.homebrewtalk.com/showthread.php?t=513435

Great thread, Maylar, I'd missed that in my research because I was searching for various versions of "pasteurize" in the header.

I will keep an eye out for permanently increased carbonation after heat processing- I'm surprised yeast could go that fast, but I can't think of any other explanation for what you observed.

I wish there was an easier way to get a gauge on a glass bottle because I'd love to have objective measurements on how the carbonation changes in each of the experiments I'm thinking of. I'm curious if my 140-F vs time method would allow you to push the cider more towards 2.4 volumes without risking overpressurizing the bottle.

My experiment would look something like this:

Cider backsweetened with something fermentable. Bottled fairly cloudy/young so there is still a lot of yeast to fight against. Let carb in in bottles, then split the batch and process as follows:

1. Control- put bottles into fridge
2. 141 F for 15 minutes- ~15-17 PUs
3. 141 F for 45 minutes- ~50 PUs
4. 180 F for 10 minutes- ~bazillion PUs

I'd taste and test the bottles against each other over time, for evidence of flavor changes, differences in relative carbonation, and increasing carbonation over time (aka inadequate PUs).

Sample size will be too small to really determine anything about bottle safety, but I think it'll give me a decent answer to the questions of A) is 15 PUs enough to kill a strong yeast population and B) does time/temp noticeably affect flavor?

Regarding sudden increase in carbonation, are you sure you're just not seeing the effects of heating up the liquid and CO2 gas? I also noticed that when I pasteurize, the liquid level in the bottle increases a bit because the density of the liquid decreases (so I actually don't fill it all the way, to prevent catastrophe). I would be skeptical of yeast being able to create so much carbonation a few minutes before death.

I recently opened a bottle of still cider in a swing-top bottle that I pasteurized and didn't experience any "pop!". This is all just observed experience, a potentially bad memory, and no measurements, and I haven't taken a chemistry class since high school, so take it all with a grain of salt.


Thanks for the chart! If I'm reading it correctly, does that mean, even for short pasteurization times around 10 minutes, we don't really need to get the temp above roughly 160*F (140*F + 20*F of fudge room, since the liquid has to heat up when you first put it into the bath), so long as the water is well-circulated? I'd really like to push the temperature as low as feasible to make the process safer.

I use my wife's gigantic water bath canning pot... it comes with a metal frame that keeps the bottles from touching the bottom and lets me fully submerge my 750mL bottles.

My data is admittedly based on a small sample size, but the results were fairly consistent. After the bottles returned to room temperature the pressure in them was higher then when I started. I would very much like for someone to continue that experiment and tell us if it's BS or not. I'm good, but I have been known to be wrong before...

Earplugs, I would suggest letting the cider clear and go dry before doing your tests. Taste changes are likely to be subtle, I wouldn't want to use cider that's still fermenting as the control sample. And I would encourage you to acquire the gage setup that I showed in my thread - having real scientific data is a lot more meaningful than "the bottle fizzed when I opened it".

I've been debating on getting one of those Sous Vide gizmos for the kitchen anyway (steaks cooked perfectly, oh yeah). If they are a viable means of pasteurizing too it'd make the cost less painful.

Maylar said:

My data is admittedly based on a small sample size, but the results were fairly consistent. After the bottles returned to room temperature the pressure in them was higher then when I started. I would very much like for someone to continue that experiment and tell us if it's BS or not. I'm good, but I have been known to be wrong before...

Earplugs, I would suggest letting the cider clear and go dry before doing your tests. Taste changes are likely to be subtle, I wouldn't want to use cider that's still fermenting as the control sample. And I would encourage you to acquire the gage setup that I showed in my thread - having real scientific data is a lot more meaningful than "the bottle fizzed when I opened it".

I've been debating on getting one of those Sous Vide gizmos for the kitchen anyway (steaks cooked perfectly, oh yeah). If they are a viable means of pasteurizing too it'd make the cost less painful.

Click to expand...

Great minds think alike Pressure gauge mounted in bottle cap

I think many of the electric brewers (e.g., me) have used their systems to cook food sous vide. An electric HLT is perfect for it (though probably a bit oversized for the task). But my 15.5g keggle could hold a lot of bottles.

Do you guys think there's any reason the bottles couldn't be submerged? I would think it would result in the least stress to the glass.

So I'm new to brewing, but I'm starting with hard cider. I'm on my secondary fermentation and I'm thinking about bottling. I want a sweeter cider, so I'm looking at options to kill off all the yeast and backsweeten. I ended up getting a nice kegging setup on craigslist for pretty cheap, so I plan to use that to force carbonate instead of using conditioning tablets/whatever.

I'm looking at two different ways to kill off the yeast; pasteurization and a potassium sorbate / campden tablet combination.
I am reading that the chemical way to kill off yeast and prevent it from refermenting is less reliable than pasteurization.

This is where I get into my questions.
I was thinking of using a sous vide setup to pastuerize, but have two questions
ONE: If I backsweeten and use force carbonation, then fill my bottles, can I still pasteurize? I've only seen instances of pasteurization when people let the yeast create carbonation. I've not seen an instance of people force carbonating then doing it.
TWO: Can i just pasteurize the liquid before I force carbonate it? As in a whole batch of still hard cider I bring up to pasteurization temperature, then lower, put in a keg, sweeten it and force carbonate, then bottle.
Would that damage my hard cider or mead or whatever I'm doing?

Im going to post this question in newbies forum too, but I figured the sous vide thread might work since that was what I'm thinking on using.. Just stick it in my cider and let it heat it up?

Thanks for your time
Collin

I recently got an electric set up for my beer brewing, so I am going to try filling it with 120F tap water, and then setting it to heat to 150F, with carbonated sweetened cider that i just bottled to empty a keg. I will update.

Edit: at 137 Fahrenheit, a bottle cracked. It was fully submerged in water so there was no dangerous shrapnel or anything. I also had a lid over the kettle just in case.
Edit: i think two more blew are 142. Turning off the heat for a hour...

andrewmaixner said:

I recently got an electric set up for my beer brewing, so I am going to try filling it with 120F tap water, and then setting it to heat to 150F, with carbonated sweetened cider that i just bottled to empty a keg. I will update.

Edit: at 137 Fahrenheit, a bottle cracked. It was fully submerged in water so there was no dangerous shrapnel or anything. I also had a lid over the kettle just in case.
Edit: i think two more blew are 142. Turning off the heat for a hour...

Click to expand...

Do you have the bottles resting on the bottom of the pot? Maybe too much direct heat from element?? Possibly try a small cooling rack in bottom of pot to keep the bottles off the bottom. Not sure if that will help or not but don't think it could hurt either.

GilSwillBasementBrews said:

Do you have the bottles resting on the bottom of the pot? Maybe too much direct heat from element?? Possibly try a small cooling rack in bottom of pot to keep the bottles off the bottom. Not sure if that will help or not but don't think it could hurt either.

Click to expand...

That's an excellent point, the water near the bottom, where the element is, gets the hottest until convection slowly disperses it. If you have a pump you could recirculate to keep the water temps more homogenous.

Some bottles are stronger than others.

I'm looking into doing something similar by adding fruit puree to a finished sour, to be more like a Lindeman's, just to have around.

GilSwillBasementBrews said:

Do you have the bottles resting on the bottom of the pot? Maybe too much direct heat from element?? Possibly try a small cooling rack in bottom of pot to keep the bottles off the bottom. Not sure if that will help or not but don't think it could hurt either.

Click to expand...

This is a good eBIAB rig with a mesh false bottom.

Results, of 15 bottles total:
13 mixed 12oz beer bottles: 2 exploded, 11 intact.

2 clear "Acqua Panna Still Mineral Water" clear glass with beer-style caps: both intact, one had the top pop off so it was a loss.

Cider was carbed at standard beer levels, about 10PSI@40F.

No apparent relation between fill level (2" of gas space vs .5") and explosions. The exploders had no brewers markings whatsoever on them. The bottles that blew were not the ones closest to the element. (The Sam Adams and New Belgium bottles were intact, though this wasn't a controlled experiment, so don't read too much into that)

I filled with about 10Gal of 128F water, with the temperature showing 110F at equilibrium.
Waited a couple minutes, then set my controller to 150, with recirculation on to avoid hot spots.
Next time, I would probably only run the element at 20%, as 5500W might have brought the temperature up too fast. Or, I might use my 1000W sous vide heater in a 5gal bucket, as broken glass cleanup is a lot easier in that.

Another possibility would be to buy champaign or Belgian bottles, as they can hold a lot more pressure.

Great thread here, Late to the piece, but I'd appreciate any feedback here.
I'm about to give this ago but I have a step in the middle which I'd like to ask about.
I'm wanting to achieve an end result of medium sweetness by back blending juice to taste, and then lightly prime for carbonation.

Question: Sulphur...
I use potassium metabisulfite (don't judge) in the lowest measure (PPM) post fermentation when my Gravity is between 12-15 Down from the 50's.
Within 2-3 hours all bubbles stop and the brew relaxes to a halt.

I've tested cold crashing the brew (for clarity) but after the addition of sulphur I leave the airlock in so it completely stops and the excess sulfur dioxide and co2 bubbles can be released from the container.

The question is, what happens when I go to raise the temperature of the whole 5L glass jar boy, with the brew (yeast at bottom) to @60c for 10mins in a water bath with my Anova unit?

There is no oxygen, so heating this won't have the increased (catalyst) effect on fermentation as everyone has discussed.
The pressure and thickness of the glass is apparently rated to handle sterilisation at a way higher temperature, I'll still test carefully and report back.

Don't have any experience with trying to pasteurise a whole carboy but have a look at my post of 1 Feb 2021. There is some information on results of different pasteurisation methods, times, and temperatures using sealed bottles plus reference to some recent work out of Washington State University on PUs needed for effective pasteurisation. Also there is a reference to a CFD study on temperature profile in the bottles over time. I don't know if this can be applied directly to larger containers like carboys, but overall a rough "rule of thumb" of 10 minutes over 140 degrees followed by 10 minutes cooling down just about guarantees effective cider pasteurisation.

So I read through this post and tried my hand at pasteurizing a batch of cider with my Sous Vide since it seems like the safest way to do this at home. I sweetened the whole batch before bottling and since I prefer non-sparkling I pasteurized right after bottling. Here’s what I did:

I had two pots going. I put in about 6 or 7 bottles depending on their size and what would fit into the pots with nothing touching each other. Then I added a single bottle of the same size with room temperature water and put an electric meat thermometer in that bottle doing my best to keep the thermometer from touching the sides of the bottle. After that I added warm tap water to the pot being careful not to get any in the open bottle of water. I filled it to about the level of the cider in the bottles. I then turned on the sous vide at 145F. It took about 35 minutes to reach 140, after which I turned down the sous vide to 141 and started a 10 minute timer. After the ten minutes were up, I turned off the sous vide and transferred it to the second pot. I left the bottles in the first pot to cool down a bit while the second heated up. Once the second pot got to 140, I took the bottles out of the first pot and replaced with the next set of bottles replacing the water filled bottle as well. I continued this process until I was done all bottles.

Seemed to work pretty well although it took a long time. But I’d rather it take longer then to have broken bottles.

If anyone sees any issues with my process please let me know.

Well done. The process sounds pretty much the same as mine, except I go a bit higher with the temperature (65C/150F) and put the bottles straight into the hot water bath then take them out after 10 minutes as they will continue pasteurising for another 10 minutes or so until they cool down to 60C/140F.

I understand the need for caution when first doing this (it is a bit scary, especially if you get a bottle bomb). However at your 140F/141F you are only generating about 1 PU per minute so the level of pasteurisation isn't accumulating very quickly and nothing is happening in the 35 minutes while the whole lot (bottles and bath) get up to 141F, so your process does take some time.

I haven't had any thermal shock issues from putting room temperature bottles straight into hot water so far, but I am aware that others pre heat the bottles in hot tap water in order to avoid this potential issue.

As you aren't carbonating the cider, lets assume that inherently it might have 1.0 volume of CO2. According to Andrew Lea's Carbonation Table, the bottle pressure at 140F/60C would be 30 psi and at 150F/65C it would be 35 psi. i.e not much increase in pressure for the potential reduction in time the bottles need to be in the water bath together with a bit more certainty that your pasteurisation is complete. Also, most soda and beer is carbonated to 2.5 volumes of CO2 which is around 30 psi at room temperature. Bottles are generally rated (and tested) to well over 100psi. Even with 1.5 volumes of CO2, the pressure at 150F/65C would only be 60 psi.

I know we can easily get hung up on calculations etc, but this really isn't rocket science. As long as the cider is hot enough for long enough you will get the result that you want. So, go with whatever method you are comfortable with.

Just for fun, it might be worthwhile logging the bottle temperature and times then do the del Veccio formula calculations to get an idea of the level of pasteurisation being achieved. Certainly there is good evidence that less than 50 PUs is fine for cider.

Thanks Chalkyt,

It was my understanding that pasteurization starts at around 120F so even though I only held the temperature to 140F for 10 minutes, I also have a good 20 minutes before and after at lower temperatures that are still adding to the job. I expect I’ll know if it didn’t work in the next couple weeks as I open bottles that have been sitting. I can also look for sediment. To be safe, I may increase to 145F next time though.

You are right, it is generally acknowledged that temperatures over 120F will cause some yeast cells to die, depending on the strain of yeast. But above 140F (60C) is the "magic number" commonly quoted to ensure that all yeast dies after reasonably short exposure to this temperature. Have a look at the chart in Passedpawn's post above which demonstrates that 100 minutes at 120F are needed to create a lethal environment for a mixed population of yeasts and brewery bacteria.

Having said that, I would expect that your method has achieved complete pasteurisation so if you are happy, stick with it.