Off-flavours are the fastest way to lose a regular. The good news is that most of them have well-understood causes and practical fixes. Here are the ones we encounter most often during brewery audits.
Diacetyl (butter, butterscotch)
Cause: a natural by-product of fermentation that yeast normally reabsorbs. It lingers when fermentation is rushed, yeast is unhealthy, or beer is crashed cold too early. Bacterial infection can also produce it.
Fix: allow a proper diacetyl rest, check for it before chilling, pitch enough healthy yeast, and audit cleaning of lines and tanks.
DMS (cooked corn, cabbage)
Cause: compounds from pale malts that are not driven off during the boil, or that form while hot wort sits too long before chilling.
Fix: a vigorous, uncovered boil of adequate length, and cooling wort promptly after whirlpool.
Acetaldehyde (green apple)
Cause: beer packaged or served before yeast has finished cleaning up, often to free tank space.
Fix: give fermentation enough time, keep yeast healthy, and plan tank capacity so beer is not pulled early.
Oxidation (wet cardboard, sherry, dull hops)
Cause: oxygen picked up after fermentation during transfers, dry hopping or packaging.
Fix: purge tanks and hoses with CO2, minimise transfers and monitor dissolved oxygen.
Sourness, haze and phenolic flavours from infection
Cause: wild yeast or bacteria in poorly cleaned equipment, hoses, heat exchangers or draft lines.
Fix: review cleaning and sanitising procedures, replace worn gaskets and hoses, and clean beer lines on a strict schedule.
Solvent and hot alcohol notes
Cause: fermentation temperatures that are too high, which is common in warm climates when glycol capacity is short.
Fix: control fermentation temperature tightly and make sure the chiller is sized for peak summer loads.
Building a quality system
Fixing one batch is not enough. A good quality program includes sensory panels, standard operating procedures, basic lab checks and records that make problems traceable. Our brewing operations consultancy puts these systems in place, and our brewery revival service is designed for breweries where quality has slipped. We work with breweries across India from our base in Bangalore.