Cloudy after pasteurization - why?

[Pharquart]

I have been making meads and ciders for about 3 years now, and am getting much better with practice. I generally like sweeter (1.010 to 1.020ish) stuff. The original technique was to start with enough honey to reach the yeast's alcohol tolerance so I could back sweeten to the desired level without having to worry about refermentation and bottle bombs. But depending on the yeast, that gets you into the 15% ABV range. I'd prefer something lower both for drinkability (like a session mead at about 8% ABV) and less chance of fusel/hot flavors that take a year to mellow out. I tried bread yeast which has a lower alcohol tolerance, but its flocculation stinks--too hard to avoid all the wispies. Or if I'm making a hard apple cider at 5-7% ABV, you can't find a weak enough yeast. I want a sweet cider or a sweet session mead, so I need to stabilize somehow.

So I started to use chemicals to stabilize the brews. Ferment to dry at desired final ABV, let sit a couple more weeks to clear, rack off the lees, add potassium sorbate (1/2 tsp per gallon) and potassium metabisulfite (about 1/16 tsp per gallon), wait 24 hours, back sweeten, bottle. (I have a keg system, so if I want carbonation I force carbonate and don't need active yeast for bottle carbonation.) Then I had a few batches restart fermentation even after the chemical stabilization. One restarted about 4 months after bottling. I happened to notice one bottle fizz when I opened it and rescued 4 more bottles before they could explode! I have no idea why the chemical stabilization failed.

After consulting with a local meadery owner, I started to try heat pasteurization rather than chemicals. I follow the identical steps as above except I omit the chemicals. I bottle immediately after back sweetening, then pasteurize immediately after that so there's no time for fermentation to begin again. I use an immersion circulator with my bottles in a big pot, starting with room temp water in the pot (same as the temperature of the product in the bottles) and raise the water temp to 145F. I monitor a tester bottle to make sure the internal temperature of the bottles gets at least to 140F and hold 20-25 minutes at that temperature. That gets me 20-25 pasteurization units, which should be enough to be sure to kill the yeast. And the lower temp should reduce the impact to cooked flavors, even at the longer time, compared to 165F or higher used in high temp/short time pasteurization.

As far as I know, the pasteurization works to kill the yeast and prevent refermentation of the back sweetening sugars. All good, except that I've found in two separate batches that I end up with a huge cloud of something at the bottom of the bottles after they cool. The first batch I tried was a cyser (maple syrup and honey mead) that was cloudy even 4 months after bottling, which was normal. (This was the batch that restarted fermentation and I rescued.) After I pasteurized, the product became crystal clear, and there was a mass of cloudiness for about 1" at the bottom of the bottles (see picture). It's not a compact firm cake like yeast lees, but not as wispy as bread yeast lees. But it sticks up enough and floats around enough that it's hard to rack off of the product without either getting some of the cloud or losing a lot of product. The other batch it happened on was an apple cider. It fermented dry and perfectly clear. I racked, added fresh sweet cherries to flavor and sweeten, and then pasteurized it, making sure the internal temp got to 140F for 20 minutes. Here, too, I noticed a cloudy mass at the bottom a couple days later.

I've tried searching but can't find much about pasteurization causing sediment/cloudy mass. While I like the resulting clarity, I don't want lots of junk at the bottom of my finished bottles! Any ideas what this stuff is and why it's forming after pasteurization?

 

[Kyzaboy89]

I've had this happen in past cysers, I think it's just pectin haze. My experience is if it hasn't fully cleared on its own/cold crashing/sparkoloid etc. it can look crystal clear and after bottling the last bit will settle out. Not sure why but I do an extra racking with apple and strawberry meads/ciders and I've found that helps. Not sure why racking causes more to fall out of suspension but even being careful I've seen an inch or two of fine fluff develop in aging. Pasteurization might have something to do with it but I'll let someone who knows/experienced that give their take on it.

 

[CKuhns]

@Chalkyt "Ping" any thoughts?

 

[Pharquart]

One of the few ideas I've read elsewhere suggested pectin as well. It can be clear in normal solution but heat denatures the proteins causing it to cloud up. Makes sense in the cherry apple cider, but not the other one. And now, looking back, I realize I used the wrong brew name. I used "ceyser" (apple juice and honey) when I really meant "acerglyn." I had the "maple syrup and honey" description right, just had a brain lapse on the name. Is there pectin in either honey or maple syrup? I thought pectin only came from fruits.

 

[Kyzaboy89]

Pectin is fruit, I've had protein in honey and maple syrups cause a haze that aged out but again, not sure what the heat pasteurization may do with that.

 

[Chalkyt]

Thanks for bringing this to my attention CKhuns.

I have also sometimes noticed a similar problem but don't know what causes it. It doesn't happen all the time but I have had some clumps of sediment settling in the bottom of heat pasteurised bottles when I am pasteurising at something like 1.008 for a slightly sweet cider.

The clumps can float and be a bit unattractive when it sits in the neck of the bottle (I don't mind, and quite expect a little "powdery" sediment settled in the bottles after time) but does disperse somewhat and settle with a bit of a shake.

I rather suspect that the heating process causes it, even though I only pasteurise around 65C or so. I haven't been too bothered or kept a close watch (we are making "Craft" cider after all) and although it seems to be a bit random, I will now keep an eye on which batches it happens with. Sometimes I bottle and pasteurise "on the way down" which means that there hasn't been a lot of time for sediment to settle out in the secondary fermenter. Other times if fermentation has gone quickly I may let the cider ferment fully, leave it for a while then add sugar for carbonation and sweetness, bottle, then pasteurise at the CO2 volume and SG that I want (I uses a "Grosch" bottle with a pressure gauge to monitor carbonation progress and assume that around 4 gravity points will be consumed by carbonation with the remaining unfermented sugar resulting in the sweetness. (i.e if I bottle at 1.012 and carbonate to 2 volumes I should end up with a stable bottled cider at 1.008 with 20g/L of sugar... about a tsp per glass)

I guess that with the "fully ferment" process, there is less sediment in suspension when transferring to the bottling bucket and hence to the bottles, so at this stage I am wondering if the clumping only happens with the "on the way down" batches which probably have more suspended sediment.

Hmm, something else to take note of.

 

[AzOr]

Hope it’s not too late…
I’ve had ciders and session meads that never fully cleared in the carboy drop crystal clear once pasteurized. Leaving a bit of trub or lees in the bottom of my bottles. Especially apples that were high in tannins (bitters). I don’t know why that happens to hydromels.