Fermentation and off smells

[tomash1]

We have been brewing double batches over the last couple years for efficiency. Once the wort is chilled we split the batches into two fermenting buckets (20 litres each) make sure there is plenty aeration then pitch the yeast SAFEALE- US-05 and clip the lid shut. We ferment at a consistent temperature of 20 degrees for about 12-14 days then bottle.

Our bottling procedure is as follows;

1 - We thoroughly sanitise our boiler to use as the bottling bucket.
2 - We boil 120g of brewers priming sugar and add to the boiling bucket.
3 - We transfer the contents from one of the fermenters into the bottling bucket making sure not to create aeration.
4 - We then use the ball valve to fill each individual bottle.
5 - Once the bottling bucket is empty we re-sanitise then repeat the process above with the second fermenter.

Issues

Almost always, apart from once, one batch always has an off smell and funny taste and we have absolutely no idea how this has come about.

We believe its not the fermentation process as both fermenters are sitting side by side in the same conditions. All bottles are put in the dishwasher at high temperatures on brew day then sanitised immediately afterwards using star san so we don't believe it is that either.

The boiler (bottling bucket) is also sanitised before and in between bottling the two batches.

The off smell/taste is always the same and its always occurs on one batch only.

Has anyone experienced this before or know what the issue may be?

Many thanks
Tom

 

[ESBrewer]

Do you use a single kettle for boiling and how do you transfer the boiled wort from kettle to fermenter? During my first brews I noticed that in the boil kettle the taste is quite different on top of the kettle vs the bottom. I read (from here I think) that the oily compounds may come to the top and at the bottom there will always be some fine coagulated stuff (trub) that ends more or less to the fermenter. So if you first take from the top (or the bottom) of the kettle the composition will be somewhat different in the first fermenter than the second?

 

[tomash1]

Do you use a single kettle for boiling and how do you transfer the boiled wort from kettle to fermenter? During my first brews I noticed that in the boil kettle the taste is quite different on top of the kettle vs the bottom. I read (from here I think) that the oily compounds may come to the top and at the bottom there will always be some fine coagulated stuff (trub) that ends more or less to the fermenter. So if you first take from the top (or the bottom) of the kettle the composition will be somewhat different in the first fermenter than the second?

Yes we use a single kettle for boiling. We then chill the entire double batch to the desired temperature and transfer by just opening the ball valve on the boiler. We alternate filling the fermenters every 5 litres so its mixed well. Before pitching the yeast we take the reading and have a taste of wort from each fermenter and cant tell the difference as both seem fine. Its only after tasting once the bottles are conditioned that the off taste is detected.

 

[ESBrewer]

Next time I would probably try to split the first and last 5 liters so that you alternate more frequently between the fermenters. In the middle of the kettle the wort composition is likely to be more uniform and 5 liters could be fine. You could also transfer some between the fermenters after they are filled. It could be that you don't taste the difference in the samples if they are drained from the bottom(or top) and the difference lies on the top(or bottom). This is just my 0.02$.

 

[tomash1]

Next time I would probably try to split the first and last 5 liters so that you alternate more frequently between the fermenters. In the middle of the kettle the wort composition is likely to be more uniform and 5 liters could be fine.

We also try to extract almost everything out of the boiler, would you recommend leaving the last 5 litres in the boiler and discarding?

 

[ESBrewer]

Frankly, I don't have enough experience on that (or how the flow from the kettle takes place). In general it seems that people don't see so much negative effects if the trub material ends up in the fermenter. You can leave some wort in the kettle but I think it's most important that you get equal distribution of flavor/aroma compounds between the two fermenters.