Materials and Articles in Contact with Food
The first is the Materials and Articles in Contact with Food legislation EC 1935/2004. It stipulates that materials which may come into contact with food "must not transfer their constituents to that food in quantities which could endanger human health, bring about an unacceptable change in the composition of the food, or cause a deterioration in its organoleptic characteristics" (its smell or taste).
In terms of 'endangering human health' the maximum amounts of each constituent element which a material is allowed to release into food have been set by the World Health Organisation according to the accepted 'severity of consequence' of their release: so, for instance, the limit for iron is 40 mg/kg of food but for lead the limit is only 0,004 mg/kg of food.
It is reassuring that whenever stainless steels are tested for constituent release to the procedures laid down by the European Directorate for the Quality of Medicines and Healthcare, it is almost always found that the amounts of iron, chromium, nickel, etc. released are below the Levels of Detection of even today's sensitive test equipment.
Machinery Directive
The second regulation is the Machinery Directive, which requires food-processing equipment to be designed to be hygienic. But hygienic design is not an end in itself ─ it is a means to achieving the cleanliness of food-processing equipment easily, reliably and consistently. Equipment must be 'designed and constructed in such a way as to avoid any risk of infection, sickness or contagion'. And 'hygienic' does not just mean that the equipment is always clean and shiny on the outside but that it is designed to resist the build-up of process soils and biofilms on the inside and is easy to clean.
Internally, it must be smooth and have neither ridges nor crevices which could harbour organic materials. Bacteria are small ─ typically only about one-fiftieth of the diameter of a human hair ─ and they can hide even in scratches on the internal surfaces of food-processing equipment. From there, they can be difficult to scavenge even with a hot, concentrated, turbulent detergent. And this means that precision engineering is needed to combat the advance of these tiny, but harmful, micro-organisms, something to which stainless steels are ideally suited.