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Old 02-12-2017, 08:17 PM   #1
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Default Another stuck fermentation thread

Hi all,

Sorry another stuck fermentation thread.

Did a grain brew a week ago but mashed a bit high at 70-72 (trying to get a full body beer but overdid it.)

SG was 1043 when I pitched.

The yeast head fell in after 2 days so I took a gravity reading = 1027. That's 2% abv.

But a week on its stuck at 1027.

I had used an old wherry yeast, cos I like that style. But I know wherry yeasts sometimes stick.

I know high mash temperature sometimes strip out the fermentable sugars, so that could be a factor too.

So. Today I have roused the yeast, increased the temperature setting from 19 to 21, and I've added a safale 05 yeast.

OK here's my question to you folks.....

I will wait 48hrs but if that doesn't work I am tempted to add 500g of spraymalt in case lack of fermentables is the problem. Is that wise, and if so, do I just sprinkle it in or melt in water then add? Thanks all.
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Old 02-12-2017, 09:35 PM   #2
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What has happened here is that you have denatured your Beta amylase enzyme in the mash, leaving only alpha amylase to break down the starch in your grain. Alpha amylase breaks chains into sugars at random points in the starch chain, where beta amylase acts on last 2 and 3 glucose in the starch chain, making simpler sugars for yeast to consume. As there was no Beta amylase making simple sugars the yeast has done as much as it can to consume the more complex sugars (dextrines) left by the alpha amylase. Adding more fermentables at this point will not help, your yeast will consume them and leave the sugars they can't consume as they are.



Rousing the yeast and raising the temperature may help, and the US05 might be more able to ferment some of these complex sugars and reduce your FG. So all is good so far.

Another option is to add some dry hops. This may sound odd, but hops contain Diastase. Diastase are a group of enzymes that will break down the complex sugars into glucose (alpha and beta amylase are part of this group).

You don't really need this next link, although it is a paper from 1941 that explains that Diastase in hops has been known since the 19th century. Here.
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Old 02-12-2017, 10:04 PM   #3
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What has happened here is that you have denatured your Beta amylase enzyme in the mash, leaving only alpha amylase to break down the starch in your grain. Alpha amylase breaks chains into sugars at random points in the starch chain, where beta amylase acts on last 2 and 3 glucose in the starch chain, making simpler sugars for yeast to consume. As there was no Beta amylase making simple sugars the yeast has done as much as it can to consume the more complex sugars (dextrines) left by the alpha amylase. Adding more fermentables at this point will not help, your yeast will consume them and leave the sugars they can't consume as they are.



Rousing the yeast and raising the temperature may help, and the US05 might be more able to ferment some of these complex sugars and reduce your FG. So all is good so far.

Another option is to add some dry hops. This may sound odd, but hops contain Diastase. Diastase are a group of enzymes that will break down the complex sugars into glucose (alpha and beta amylase are part of this group).

You don't really need this next link, although it is a paper from 1941 that explains that Diastase in hops has been known since the 19th century. Here.
Thanks very much for all the info. If my beer is at 2.5%,will the added fermentables raise this?
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Old 02-12-2017, 10:13 PM   #4
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Thanks very much for all the info. If my beer is at 2.5%,will the added fermentables raise this?
It will, however it will be really sweet from the unfermented sugar already in it. Adding sugar to raise the ABV would be better as it would not add any further sweetness. Ideally you want to get it fermenting again before adding anything more.

What style of beer is it? What IBUs?



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Old 02-12-2017, 10:26 PM   #5
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Sadfield can I ask you if you mash at 65c, the finish off with a 75c mash out, how come it does not effect the fermentability of your wort?
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Old 02-12-2017, 10:29 PM   #6
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I mashed a porter at 69c on Tuesday, OG 1055. Yesterday it was at 1016. CML Real Ale yeast. Wherry yeast, you say? The elephant is in the room.
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Old 02-12-2017, 10:30 PM   #7
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Sadfield can I ask you if you mash at 65c, the finish off with a 75c mash out, how come it does not effect the fermentability of your wort?
Because wort is fermentable before mash out. Mash out denatures enzymes and stops the wort being even more fermentable.

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Old 02-12-2017, 10:30 PM   #8
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They sell enzyme additions. I’ve never added it to the FV so I don’t know what will happen. But finally I got a forum buddy that is as geeky as I am on amylase!
To me, it looks like a bunch of un fermentables but also could be a lack of oxygen. You really got to shake it up for a few minutes to get enough oxygen in the wort so the yeast will start it’s growth. Boil a long spoon for a few minutes then gently take of the lid. This is so anything that is setting up shop on your lid doesn’t get kicked up in the air and settle down into your wort. Wild yeasts can eat un fermentable sugars WAY better than brewers yeast. So you don’t wan those dudes in there.
Now stir wildly for a minute or two. Hopefully the addition of oxygen will set the yeast back on track.
But I think Sadfield said s-05 yeast is a better yeast and can attack more complex sugars.
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Old 02-12-2017, 10:34 PM   #9
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If it doesn't drop enough you would be better off adding sugar to up the abv, as this will help dry it out. If you add spray malt then you will add both fermentable and non-fermentable sugars and you already have too many non-fermentables.

I remember reading about a brewery that did what you did and ended up bottling it sweet. The thing is, the yeast was still working on the complex sugars but only very slowly. Over time the pressure built up and they were over carbonated. If I were you I'd hold back a bit on the priming sugar.
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Old 02-12-2017, 10:34 PM   #10
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Sadfield can I ask you if you mash at 65c, the finish off with a 75c mash out, how come it does not effect the fermentability of your wort?
It’s the length of time that is important. Step mashing can really control the enzymes and I would recommend it to brewers who want to up their game on brewing. Starting out at 62 for 15 to 20 minutes then up to 65 for another 20 minutes then up to 68 for the remainder of the mash the ramp it up to 75. From 68 to 75 takes time so your adding the full body to it. But you still have to be critical on your yeast.
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