Is filtration enough to allow for backsweetening?

I am planning to do a fruit beer with a bunch of fruit concentrate. I want to ferment half of it out and then backsweeten with the other half of the fruit. I can filter down to .5 micron (although I already have a 1 micron so it would be nice to use that). So I would like to just filter out the yeast and then add the second half of the fruit back as a sweetener. I have filtered and backsweetened with a mead before and it seemed to work pretty well but it hasn't been in the bottle that long either so I am not sure how stable it will be.

So what are your opinions? Is filtering enough to remove all of the yeast or am I going to have to add some preservatives?

According to Midwest Supplies, a 0.5 micron filter will remove MOST of the yeast. I take this to mean that there is still some left and that it would continue to ferment if more sugar was added. Personally, I would not trust a filter to remove enough yeast to guarantee that it would not ferment again.

That said, try it. Filter it into a sanitized carboy, sweeten it, squirt some co2 on top to prevent oxidation and let it sit. See if it ferments out the added sugar.

If you want to sweeten without filtering or chemicals, you can use a non-fermentable sugar substitute.

My 2c.

I'm assuming that you'll be force carbing.

I would think that several things will help. First, cold crash to get the yeast dormant, or at least slowed down. Then filter with a .5 micron. If you keep the beer cold after adding fermentables, then it shouldn't restart fermentation even without the filtering.

But if there's still some yeast in the bottle with fermentable sugar (fruit), letting the bottles warm up at any time could cause a bottle bomb.

bsay said:

If you want to sweeten without filtering or chemicals, you can use a non-fermentable sugar substitute.

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Splenda is the generally preferred product.

Or you can get some potasium sorbate to kill the yeast. You can find it at cheesemaking suppliers.

TrojanMan said:

Splenda is the generally preferred product.

Or you can get some potasium sorbate to kill the yeast. You can find it at cheesemaking suppliers.

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Just be aware of allergies to Potassium Sorbate. I have ran into some people who get headaches when they eat/drink anything containing potassium sorbate.

First of all I will be kegging, so carbonation is no issue. Second, the whole point of the backsweetening is to add more of the fruit concentrate back, so artificial sweeteners are out. Third I would like to give some of this away so keeping it cold the whole time is less than ideal.

I really don't mind using preservatives, I just never have before so I wanted to see if it is necessary. Based on the responses here you guys seem to think filtration alone probably won't cut it. So do any of you wine experts have a recommendation for how to go about it adding preservatives?

What about pasteurization? I am cloning a commercial beer and they achieve backsweetening through pasteurization, but I hadn't really though about it before. What if I heated the entire (vented) keg in a big ol pot of water?

Is there any reason I couldn't just do the potassium sorbate and campden tablet treatment that wine makers use? If so how long do I need to leave it in the secondary after racking it onto them?

TrojanMan said:

Or you can get some potasium sorbate to kill the yeast. You can find it at cheesemaking suppliers.

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Or your local brew store...wine is stabilized with potassium sorbate and metabisulfate.