Recently I finished my 6th batch of beer, the first top-fermenting one (wheat beer). The yeast is from a commercial brewery nearby, so I don't know its exact type. Usually my bottle fermentation takes place at cellar or even room temperatures and I put the bottles in the fridge a couple of days before drinking. For bottom-fermenting yeast this worked nicely so far.

The bottle fermentation and storage of the new batch:

Half of the batch (A): 4 weeks at room temperature

Half of the batch (B): one week at room temperature, 3 weeks in the fridge

Half B tastes really good, Half A shows a distinct sour overtone. Is top-fermenting yeast more prone to building undesired byproducts during bottle fermentation than bottom-fermenting yeast? Or could the summer temperatures be the reason? (Cellar: 10°C in the winter, 15°C in the summer, Room: 18°C in the winter, 23°C in the summer)

2 Answers 2


If you have sour overtones, then you likely have either an acetobacter, pedio, lacto or a wild yeast contamination. And, having been at a warmer temperature for longer will have allowed this biological contamination more opportunity to generate sour off flavours to a level above the taste threshold.


Not during bottle conditioning. Both ale and lager strains will behave the same and produce no esters.....

Unless there was oxygen contaminate then the yeast may try a growth phase again producing esters. In this scenario lager strain will produce more esters at warmer temps,than an ale strain will.

As already answered by Mr_road. A sour taste would be from a wild yeast or bacteria contaminate.

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