Aus River Cottage - Curing & Smoking von Steven Lamb:
Moulds
Just as there are good and bad bacteria, there are desirable and undesirable moulds. However, moulds are a slightly less scary subject because they are mostly benign (there is little or no risk that the wrong mould will kill you), and they are visible to the naked eye. Also, moulds grow at a much slower rate than bacteria (which, in the right conditions, can multiply into the millions from a standing start in under 10 hours).
With moulds, there is a greater element of control. They are only ever present on the surface of foods because they are aerobic (require oxygen) and so they cannot hide unnoticed in the middle of a salami. In extreme cases, you can get moulds that release poisonous ‘mycotoxins’ – but these tend to affect only grains or vegetables.
In most curing, the desired mould is a very distinct chalky-white variety known as Penicillium. This is similar to the blue mould you find in some cheeses (which is deliberately placed there by the cheesemaker). Not only does it contribute to the overall flavour of the cured product, it also performs three very important functions. Firstly, once the mould is present on the surface, it will grow to cover the entire surface, thereby inhibiting any harmful bacteria from getting a foothold. Secondly, it consumes oxygen and thereby reduces the process of oxidation in the cured product itself. Oxidation discolours and causes ‘off flavours’. Lastly, it forms a barrier between the
surface of the cured product and the natural light which can turn fat rancid. Quite often, you’ll come across other moulds on your cured foods – green, orange or black – and sometimes in fuzzy long fronds. These undesirable moulds are due mostly to an absence of air movement around the curing meat or too much warmth. Stagnant air generally causes the wrong moulds because the humidity levels are too high. Perfect air-drying humidity levels are between 60 and 80%, where the benevolent Penicillium moulds prosper.
However, these unwelcome moulds do not indicate that the meat is off (not unless it is actually black and dripping, with a rancid smell!). You can clean off unwanted moulds with a cloth or nail brush dampened in malt vinegar. This has anti-microbial qualities and will also increase the acidity on the surface of the food, which tends to promote the Penicillium mould that you want. If you don’t find the right mould growing on your cured meats, you can put it there yourself. You can buy a commercial culture, dissolve it in distilled water then apply the solution to the meat, or simply dip the meat into it. These cultures are available online from butcher’s sundries websites .
Alternatively, you can hang inexpensive shop-bought salami next to one of your own curing salami and the mould will simply travel from the finished product to your own. What’s more, the beneficial microflora will then always be present in the area that you have designated as your air-drying spot for curing, which is a very good thing. I have seen moulds of all types on cured food – both home-made and commercial products. My inbox is full of pictures of mouldy meat from all over the world! The rule of thumb should be to use the vinegar technique to clean off any mould that doesn’t look powdery and white, check temperatures and humidity levels regularly and wait for the mould to come back in the desirable form. This will not harm the curing process – it just means that the flavour won’t be as mature until the mould is present.
