Surface yeast defects of cheese are normally cheese type dependent. Yeasts are common micro-organisms and some are intentionally used in cheese making for their effect on texture and flavour such as smear ripened cheeses. This article is not for those but for yeasts on the surface of cheeses which result in unwanted textures or flavours, their common causes and solutions, sorted by root problem.
- Typical excessive yeast smell is like rising uncooked bread or fermenting beer or wine and taste can be bread flavour.
- Yeasts are common in the wild and in raw milk.
- Most unwanted yeasts on surface cheeses are caused by air born wild yeasts fermenting on an excessively moist surface of a cheese.
- One common location of excessively moist cheese surface is the bottom or the side against the mat or board. The cause is normally not turning the cheese frequently enough allowing excess moisture to build on the bottom or not providing a breathable mat or board, for example drying a cheese directly on an impermeable plate versus on well ventilating mats or breathable wooden boards.
- A second common location of excessively moist cheese surfaces is all over the cheese if the cheese is in a sealed closed container without airflow and 100% humidity which also invites unwanted molds but enables yeasts to dominate as molds need oxygen to grow. The solution is correct humidity during aging.
- Yeasts are remarkably resilient and once established, their removal is difficult, washing with vinegar will not remove them as it can only lower the pH to ~3.
- Recommended treatment is to:
- Remove yeast contaminated curd with brush.
- Wipe the rind with vinegar then dry the surface of the cheese.
- Wipe rind with distillers alcohol then dry the surface of the cheese.
- Rub rind with salt then remove excess dry rind.
- Oil the rind.