This article discusses air drying which entails drying the freshly formed cheese ia evaporation to air to remove excess moisture from the surface and thereby form a dehydrated rind that can better withstand unwanted molds and yeasts. Note, pressed cheeses include those that are pressed with an external weight or if large via their own internal weight, also some such as washed curd Gouda types are brined after pressing before being air-dried.
For hobby and small commercial cheese makers, air drying is performed by placing the young cheese(s) on a mat at room temperature typically for 2-3 days such that moisture is evaporated into the air is enable and the cheese is periodically turned to maintain it’s shape and enable even drying of all sides. Commercially, this phase is accelerated by cold air being blown on the young cheeses.
Note, removal of a small amount of water from the cheese naturally results in similar small amount of shrinkage.
Air Drying Method
The primary problem is to obtain the right speed and amount of drying, the variables being cheese size and moisture content, and air humidity, movement and temperature.
Not enough evaporation and the cheese’s surface will stay moist and be a base for molds and yeasts. Conversely too fast will result in uneven moisture content across the cheese, the outer rind will dehydrate rapidly resulting in shrinkage while the middle stays moist and does not shrink. This results in tension stress around the surface and compression in the middle of the cheese, somewhat similar to a football but on a much smaller stress scale.
The problem here is that cheese has very poor tensile strength and if this stress is excessive, dried too quickly, then the cheese will split in one or several places to relieve the stress. This splits will often result in deep fissure type defects as the moister middle of the cheese has even less tensile strength than the dehydrated surface. An example common environment causing this problem is air drying in household kitchen cold and low humidity fridge, even if in a higher humidity vegetable or cheese drawer. Solutions to this splitting are discussed in the Wiki: Defects articles.
Air Drying Base
A second common problem is how to enable the base or bottom side of cheese to dry.
Placing cheeses on an impermeable surface such as plastic or china plates is the worst as the bottom will stay completely wet and whey as it is expelled will puddle, resulting in a severe location for molds and yeasts to start.
At the other extreme, drying cheeses on widely spaced metal racks will result in the best circulation of air and thus drying of the bottom of the cheese, but depending on cheese hardness and wire spacing will often result in less aesthetically pleasing deep deformation “dent” lines in the young soft cheese.
In between these two extremes are cloth and mats. Cloth and closely spaced mats also do not work well, while they let the cheese breath, capillary forces will often hold water in the mesh, a location for molds and yeast. Mats if close spaced weave will also do the same, see samples in picture at right where only the right widely spaced “thread count” mat avoids this problem and is recommended, but only when placed on a wire rack to allow good air flow beneath it. Placing a cheese on any mat on an impermeable plate will still pool whey.
Air Drying Time & Temperature
Air drying is completed when the whey completely stops draining and the cheese’s surface is dry. At what length of time and temperature is a more difficult discussion given the range of sizes and moisture contents of cheese, and range of air temperatures and humidity levels.
That said, normal recipe air drying time before aging to obtain a good dry rind is 1-3 days at average house temperatures of 72°F/21°C and ~70-75% humidity, assuming minimal air movement, i.e. not in front of an open window or fan.
Temperatures above and below that will require less or more air drying time than the recipe. If room temperatures are significantly above that (ie summer or if in tropics) then best to air dry in fridge but then have to be very sensitive to rapid drying of rind from low humidity and cracking of rind, ie turn twice per day and inspect for cracks.
Higher humidity levels significantly above 75% will require longer time, below 60% may result in cracking as described above and thus the cheese should be partially enclosed to obtain an optimum humidity level, such as by covering the cheese with a loose fitting bowl.