Dump or blend and the business call on a bad batch
A flawed batch is a technical problem and a money problem at the same time. Blending can rescue some beers and spread others into the whole range. Here is how we would make the call.
Name the fault before you decide anything
The first job is diagnosis, not economics. Taste the beer with at least two people, check gravity and pH and compare it with the brew sheet. The common faults fall into groups that behave very differently:
- Diacetyl or acetaldehyde from an early crash. Often fixable with time, a warm rest or fresh actively fermenting yeast.
- Missed gravity or colour. A spec problem, not a flavour fault. Often sellable under a different name.
- Oxidation, papery or stale notes. Cannot be reversed.
- Infection. Sour, buttery or phenolic notes that keep developing. Cannot be fixed.
Our guide to beer off flavours helps put a name on what you are tasting.
Never blend an infection
This is the one hard rule. If the beer has a bacterial or wild yeast infection, blending it into good beer gives you more infected beer. Lactobacillus, Pediococcus and diastatic yeast keep working in the package. A blended keg that tasted fine on day one can be sour or gushing a month later in a bar's cold room.
Dump it. Then clean and sanitise every vessel, hose and fitting it touched before the next beer goes through them. The dump is cheaper than a recall or a bar that stops buying from you.
When blending genuinely works
Blending suits beers that are sound but off target. A pale ale that came out too bitter can go into a less hoppy batch. A slightly thin lager can be blended with a fuller one. A mild diacetyl note can drop below the level most drinkers notice when one part of flawed beer meets several parts of clean beer.
Trial it first. Mix the blend in a measuring jug at a few ratios, say 1 to 3, 1 to 5 and 1 to 9. Taste each one blind against the clean beer. If the panel cannot pick the blend at a given ratio, that is your ceiling. Then check that you have the tank space and the excise paperwork to do it. Blending changes batch records, so check how your state wants it recorded.
Put a number on each option
Once you know what is technically possible, the choice is about money. Work out three numbers for the batch:
- Cost already spent. Malt, hops, yeast, energy and labour. This is gone whatever you do, so it should not drive the decision.
- Margin you would earn selling it. Litres you can sell multiplied by margin per litre.
- Cost of the fix. Tank days, extra yeast, staff time and the good beer it ties up.
A fix only makes sense when the margin recovered beats the cost of the fix, with room for risk. Remember tank time. A 1,000 litre fermenter holding a doubtful beer for three extra weeks is a fermenter not making a beer you know will sell.
Selling it as something else
Some flawed beers are not faulty at all. They are simply not the beer on the label. A lager that finished at 4.4% instead of 5% ABV, or a pale ale that came out darker than planned, can be clean and enjoyable. The honest route is to sell it under a different name as a one off or a seasonal special, priced and described for what it is.
Check two things first. The ABV on the tap list or label must match what is in the glass. Some states also need label or brand approval for each beer name before sale. Our guide to label approval from the excise department covers that process. Never rename a beer with a real fault to sneak it out. Drinkers can taste the difference between a new beer and a disguised mistake.
The cost nobody puts in the spreadsheet
The biggest number is the one you cannot see: what a flawed beer does to your name. A bar that pours a sour lager from you once will remember it longer than any discount you offer. A taproom regular who gets a papery IPA may simply not come back.
So add a rule for anything leaving the building. If the head brewer would not drink a pint of it, it does not go out. That rule costs money in the short term. It saves more over a year. Our guide to keeping a risk register shows how to log a quality failure so it does not repeat.
Write the decision rule before the next bad batch
Bad batch decisions made at 7 pm on a Friday with a full taproom tend to be bad decisions. Write the rules now: who tastes, who decides, what gets dumped without debate and what gets a blending trial. Record every dumped or blended batch with the fault, the cause and the cost.
After a year that log tells you what bad batches really cost the business. It also shows which faults keep coming back. Linking quality decisions to the profit and loss account is the part of brewery management that most brewers are never taught.
Common questions
Can you blend an infected beer to save it?
No. Blending spreads the infection into the good beer. It keeps developing in the package. Dump it and clean everything it touched.
Can diacetyl in a batch be fixed?
Often yes. A warm diacetyl rest, more time on healthy yeast or adding actively fermenting beer can reduce it before packaging.
How do you decide the right blending ratio?
Mix small trial blends at several ratios and taste them blind against clean beer. The highest ratio the panel cannot pick out is your limit.
