Unwanted Mold on Aging Cheese

Yellow Spots

Q. I currently have a Butterkäse cheese aging and I'm wondering if it's normal to have blue mold growing on the surface along with the Geotrichum Candidum. I wash the cheese with a light brine every couple days but it's very persistent in coming back. 

Also, when I turned the cheese today, I noticed small yellowish spots growing on the surface of the cheese. The spots scrape off easily with the edge of a knife with no discoloration underneath. Is this normal?

I also have those yellow spots and (shiny looking) blue mold on a Havarti I'm aging, along with some light gray-ish colored spots that also scrape off easily. I think the gray ones may mean the humidity is too high, but I was hoping you could provide some guidance.

A. The yellowish spots are likely coryneforms which are common in washed rind cheese, they will grow on any cheese with a lot of moisture. This excessive moisture also encourages the growth of blue and black molds.

Either the cheese body is too moist or the aging space is too humid, perhaps both. It could also be caused by excessive washing and not enough drying time between washes.

Dark Spots

Q. I recently made my first batch of Jack cheese using your instructions. It is in my cave which has a temperature of 52-54F and humidity of 78-85%. Dark spots, which I assume are mold, keep showing up.

I have scraped and cut them off, washed the cheese in a saturated brine and coated it with olive oil, but they return. Is this normal? All equipment was sanitized. The recipe doesn't call for the cheese to be waxed or wrapped. Is this an option for future batches?

A. The best method to keep a clean rind is to make sure you keep the surface clean early in the aging process. We recommend using a cloth dampened in a 6% brine. It's just enough to discourage the mold, but not enough to change the salt % in the cheese.

If you leave the moisture too high going into the form, mold will be a much bigger problem to control. Once the mold begins to form, it is hard to keep ahead of it and it will leave a dark stain even when removed.

Pink Mold

Q. I’m making my first farmhouse cheddar. We live in Hawaii- and I have been super concerned about our high humidity levels. I left the cheese out for a few days to dry at about 70-75 degrees, a little lower at night. It looked okay at first but now has this pink mold and other spots of mold. EVERYTHING molds in hawaii - in the future- I think I’ll get it into the wine fridge sooner. Should I throw this away- or scrape off the surfaces and wax or wrap it? Or leave it and wrap as is?

A. High moisture and warm temperatures are the perfect conditions for mold to grow. 

For post press drying, it is imperative to find a moderate temperature and humidity range; 60-68F and 65-70% would be ideal.
This does not seem too bad according to your pic, we would suggest drying it down a bit, before lightly brushing the mold away. You may need to use a small fan to keep the air moving and help with drying. Waxing would then be best, but look at our details for waxing on the web site.

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