Troubleshooting

Nearly everything that goes wrong in cheesemaking is a moisture failure or a pH failure, and usually both, because they’re coupled. Start there before hunting for anything exotic.

This page is the diagnostic table. It’s organised by when the problem shows up, because that’s how you actually meet them.

In the vat

Symptom	Almost always	Fix
Milk never sets, or sets weak and mushy	Ultra-pasteurised milk — UHT can’t form a rennet gel at all	Different milk. Check the carton; US organic is often UHT
Weak set from ordinary shop milk	Pasteurisation shifted soluble calcium out	Calcium chloride
Weak set, correct milk	Rennet past it, wrong dose, or chlorine in the dilution water	Fresh rennet; check IMCU against the recipe; unchlorinated water
Fast, brittle set that shatters	Too much rennet	Less — and expect bitterness later from the surplus
Acid stalls partway through the make	🔴 Mesophilic culture in a hot-cooked recipe — you killed your own starter	Match culture to cook temperature
Acidification sluggish from the start	Old or moisture-damaged culture, or under-dosed	Store cultures dry and frozen; check DVI-vs-mother dosing
Whey goes cloudy and white	Curd torn, not cut — or stirred before healing	Sharper knife, single strokes, and wait 3–5 min after cutting
Curd shatters into fines	Cut too early, or no healing pause	Test with flocculation or the clean break, then wait

After pressing

Symptom	Almost always
Wheel won’t knit — visible seams between curd grains	Under-pressed, curd too cool, or too acid at pressing
Dry outside, pasty wet core	Cooked too fast (sealed each cube) or pressed too hard too early
Wheel misshapen or slumped on one face	Not flipped enough, especially early
Cracks appearing during drying	Surface drying too fast — humidity too low
Curd extruding past the follower	Follower fits badly

In the cave

Symptom	Almost always	Fix
Cracked rind, dry paste	Humidity too low	Up to 85–95%; check the numbers
Slimy surface, off smells	Standing water, wet surfaces, no air movement	Gentle breeze; no puddles
Mould where you didn’t want it	Still air, or shelves overdue a clean	Air movement; clean shelves several times a year
Slimy, soft edges after brining	🔴 No calcium in the brine — it pulled calcium out of your cheese	0.25% CaCl₂, brine at pH ~5.0
One flat, never-drying face	No spacing, or not turned often enough	Space wheels; turn them — or automate it
Condensation dripping onto the cheese	Wipe the lid or underside when you turn it
Wheel blowing, lifting or cracking outward	Gas — a heterofermentative culture in a close-textured cheese, or early blowing from contamination
Ammonia smell on a bloomy	Too warm, too wet, or too little air exchange — or simply too far gone
Cheese aging but not developing	Too cold. A fridge is 10–15° below cave temperature
Blue appearing on things that aren’t blue	P. roqueforti spores travel. You brought it in

When you cut it

Symptom	Almost always
Bitter	Excessive or indiscriminate proteolysis — plant or microbial rennet in a long-aged cheese, too much rennet, or over-acidification
Soapy or rancid	Too much lipase, or fat oxidation. Neither is reversible
Metallic, and it looks wrong too	🔴 Aluminium equipment. Cheesemaking acid reacts with it
Flat, dull, no character	Under-ripened, too cold, or skimmed milk — fat is where flavour lives
Sharp and crumbly when you wanted springy	Over-acidified: too much calcium left the network. Consider washing the curd
Rubbery, won’t melt	Too little acid — too much calcium retained. The opposite error
White specks on a cheddar	Not mould. Almost certainly calcium lactate crystals — the cheese is fine
Crunchy pop in a two-year wheel	Tyrosine crystals. Your proteolysis ran properly. This is a good sign
Small openings you didn’t ask for	A gas-producing culture, or early blowing
No eyes in a Swiss	Not usually wheel size. Warm-room stage, missing propionibacteria, too acidic, too salty, or cooked too hot
Won’t stretch (pasta filata)	Outside the pH 5.2–5.4 window — tears above it, grainy below

The four questions to ask first

Before consulting any table, in this order:

1. What was the pH, and when? If you don’t know, that’s the answer — and it’s why the pH is the instruction and the clock is a proxy.

2. What was the moisture? Cut size, cook temperature, press schedule, salt. Almost every texture problem is here.

3. Did the culture survive? Check the cook temperature against the culture type before anything else.

4. What did I actually do? Which is why step 15 of the make is write it down. A problem you can’t correlate with a setting is a problem you can only guess at — and I have spent years guessing.

The three that aren’t your technique

Worth ruling out, because people blame themselves for these:

Ultra-pasteurised milk. The commonest cause of a failed first attempt, and nothing you do will fix it.

Aluminium equipment. Ruins the batch chemically regardless of skill.

Milk that’s simply different. Breed, season and stage of lactation change fat and protein substantially. If the same recipe gives a smaller wheel in October than in May, that may be entirely the milk.

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Next: rind treatment — wax, cloth, natural rind, and what each trades away.