This may be off topic, but I just brewed a batch that is sour and citrusy like grapefruit juice.

After searching around I found the distinctive grapefruit flavor compared to other citrus is the result of a sulfur containing terpene, mercaptan. I've been trying to figure out what may have caused it to develop in this batch, but not others brewed with the same yeast.

What source would you reccomend for trying to trace back flavors to the metabolic processes in the yeast?