Think of items made of stainless steel and the likelihood is that, not too far down your list, will be at least one of the following: cutlery, catering equipment and surgical instruments.
And there is one good reason why all three product types make such extensive use of this material: hygiene.
Stainless steel is inherently clean. It is flat and smooth, so there are no crevices or holes in which dirt can hide. It is impervious, so it will not absorb bacteria, odours or flavours. And its hardness not only makes it long-lasting but also means that it can be cleaned and sterilised by a whole range of methods involving heat, scrubbing, high pressure sprays and even chemicals.
And while all these benefits are equally applicable to the food industry, there are two additional qualities, the durability and thermal properties of the material, that make steel - and specifically, the steel belt - the ideal processing medium.
A steel belt can be employed in processes involving temperatures as widely varied as -80°C and 750°C; in dry, damp or even corrosive conditions; and with liquid, solid or sticky products. And it is for all these reasons that steel is now being used in preference to other belt materials in applications as wide ranging as meat cutting, poultry handling, fish freezing, coffee freezing, vegetable drying, tobacco drying, chocolate cooling, candy mass cooling, pizza baking, sponge cake baking, biscuit baking and more.
Sandvik Process Systems, the company responsible for developing the world's first steel belt in 1901, has created a complete processing solution around the technical properties of the stainless steel belt in the form of a system called Rotoform.
The heart of this operation is the steel belt but the brain is the Rotoformer itself, a device that deposits molten product onto a continually running belt in the form of droplets. As the belt runs it is sprayed from the underside with water and the heat is transferred from the product to the water via the steel belt. As a result, the product is converted from its heated liquid form into a solid form, creating pastilles that are easy to handle, to store, to transport and to reprocess.
Typical applications for this process include chocolate, gum base, fat, emulsifiers and food additives, but it can be used to solidify any hot-melt product.
Another area in which the thermal properties of steel are of major benefit is baking, where carbon steel belts have been widely used for many years. A steel-based bake oven belt also has the advantage of reduced downtime through fast, easy cleaning and the elimination of the accidental fires caused by residues. And by using a perforated belt rather than a solid one, air circulation within the oven can be improved, heating costs can be reduced and, perhaps most important of all, a better quality end product can be produced.
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- Staffan Karlsson is with AB Sandvik Process Systems in Sandviken, Sweden. www.processsystems.sandvik.com.
