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Raspberry wheat is flat

I am tying to figure out why a wheat beer that I added raspberries to turned out flat. I followed my standard procedure for priming sugar (4.6oz in this case), bottle conditioning, and capping (12oz bottles) – my other batches all turned out fine on carb. But every bottle of this 5 gal. batch is really undercarbed, many are entirely flat.

The only difference in production was adding 1.5lbs of raspberries to secondary a week or so before bottling.

Is there any reason that the raspberries could get in the way of carbonation in the bottle?

How long have they been in bottles for? What temp are they sitting at to bottle condition?

I assume the beer wasn’t in primary or secondary for several months, right?

Take a couple bottles and turn them upside down and back again a few times to get the sediment back in suspension. Put them where its warmer…75 degrees or so…for a few days.

When you chill, give them at least 2 days in the refrigerator so carbonation can fully absorb back into the beer.

Fresh Raspberries, or something that may have contained “preservatives”?

I used thawed, mashed frozen store-bought raspberries, and there were no preservatives in them that I know about.

The bottles conditioned at around 70.F for 6 weeks. And the primary/second process was about 4 weeks long.

Other than the fruit, this is the same procedure that I’ve used on many other batches and never had a problem with carb. like this – thus, my hypothesis that somehow the raspberries did something to the carbonation process. But I haven’t seen any suggestion from others that this is a systematic problem - thus my curiosity about others’ experience.

The very first bottle I opened (after maybe 2 weeks of bottle conditioning) seemed more carbonated that the bottles that sat longer. I wonder if the caps are leaking… either a problem with my capping or with the caps themselves…

How many have you tried that are under carbed?

My guess is that the priming sugar solution was not mixed well enough into the bottling bucket, which will cause some bottles to be under carbed.

Go to the store and take a look at those packages again. There is no reason high quality frozen fruit should contain preservatives, but they may be there anyway for some other reason, like keeping the color bright. Or they could have been made from fruit that wasn’t at peak and preservatives added to knock the microbial level below some threshold.

The raspberries themselves are very high in acid, and enough of that could knock the pH down to levels that the yeast have trouble with, but you’d need an awful lot of berries to get to that. Unlikely.

Thanks for the thoughts. I will file this batch under ‘things that didn’t work’ and move on to the next…

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