I tasted a sample of my current batch during the bottling run last weekend. It had an unexpected element to it - a "cask" ale taste. This was the first batch where I'd used a new fermentation bucket, and I think the cause of this was a poor seal around the airlock in the lid due to my shoddy drilling. The main element I picked up was the faint "sherry" like flavour you get when melanoidins oxidise. I did use a small quantity of melanoidin malt in this batch. Has anyone else experienced something similar?