Gastronorms
The gastronorm system originated in Switzerland and was adopted in the early 1970s by the British Standards Institution. Strictly speaking, a gastronorm measures the capacity of containers. These can be solid metal, such as in roasting trays, perforated metal for steaming, toughened glass, composite plastic materials or disposable materials such as aluminium foil. The abbreviation GN is widely used as shorthand for gastronorm.
The gastronorm system started as a method of maximising oven or fridge capacity by using containers that are compatible in size with the oven cavity, so that no corners are left unused. For those who make kitchen equipment and those who manufacture oven and fridge containers, it gives a uniform sizing structure to maximise capacity efficiency.
Yet the gastronorm system has now spread beyond its first concept and is used as a pan sizing system for bains-marie, refrigerated preparation tables, microwave ovens - in fact most items of kitchen equipment that involve the use of cooking or storage containers.
A full-size gastronorm container is referred to as a gastronorm 1/1 and measures 530mm long x 325mm wide. All other sizes are fractions or multiples of this size: so a 1/3 container is standard width (325mm) but just a third as long (176mm); a 2/1 is twice as big and measures 530mm long x 650mm wide.
The full range of sizes is 2/1, 1/1, 2/3, 1/2, 1/3, 1/4, 1/6 and 1/9. There is also a 2/4 (a "long half" measuring 530 x 162mm) and 2/8 (a "long quarter" at 325 x 132mm). The standard gastronorm depths are 10mm, 20mm, 40mm, 65mm, 100mm, 150mm and 200mm. The depth measurements should always be taken into consideration when considering oven capacity. A manufacturer might claim that an oven can take 10 1/1 gastronorms, but at what depth? For example, an oven rated to take six pans of 40mm depth holds less food than one rated to hold six pans of 65mm depth.
As well as the basic sizes derived from the 530mm x 325mm module, the gastronorm system stipulates sizes for cut-outs and grids into which container flanges fit on a servery or bain-marie.
Being a non-metric nation, the USA uses its own sizing system for ovens and containers. In practice, however, this is only slightly larger than the gastronorm and it is common for US-built ovens to have full-width racks sitting on the shelving supports, similar to those found in a domestic oven, allowing gastronorm pans to be used in them.
EURONORM v GASTRONORM
A second measuring system, called the Euronorm, uses the same principle of proportionality as the gastronorm, but is based on a 1/1 measurement of 600mm x 400mm. The oven cavity has to be wider to accommodate the larger trays, but Euronorm ovens often come with a racking accessory that will take the slightly smaller gastronorm pans as well as Euronorms.
The most common use for the Euronorm in the UK is in bakery, either for bread-making or finishing off part-baked goods. While 600mm x 400mm is the basis of the Euronorm, it also happens to be the same size as the standard British baking tray. The benefit of the Euronorm system for baking is that, with small items such as bread rolls or croissants, which are baked in large quantities, a greater number can be produced in the oven.
