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With the growing interest in whole grain, not only among researchers and health authorities but also among the consumers and the food industries, an exact and strict definition of whole grain is urgently needed (Frølich and Åman 2010).

The scientific community has for many years been involved in the discussions regarding an international common definition, including issues such as the types and parts of grains that should be included in such a definition. Important aspects in finding an applicable definition is different for target groups: the consumers to facilitate their choice of healthy food alternatives; the scientific community to establish uniform food frequency questioners and standardized dietary factors to study in relation to health; the authorities to be able to make recommendations; and the food industries to produce a variety of new whole grain products. A common international definition of whole grain would certainly benefit all these interests. However, for a definition to be useful in a long‐term perspective for all these groups, it must be grounded on evidence‐based nutritional aspects rather than simply classification of food items. In addition to short definitions launched some decades ago, more recent compressive definitions have been developed in several countries. In these definitions, lists of cereals and pseudocereals are included as well as specifications of the processes allowed to be used (van der Kamp and Lupton 2013).

Cereals are members of the grass family (Poaceae or previously Gramineae) and produce dry one‐seeded fruits (caryopsis) that are commonly called a kernel or grain (Delcour and Hoseney 2010). All cereals consist of a fruit coat (pericarp) surrounding the seed. The seed contains an embryo (germ) and an endosperm surrounded by a nucellar epidermis and a seed coat (testa). In general, all cereals have broadly similar proportions of these botanical structures. However, it is not possible to specify a standard ratio for the different botanical structures since these vary within and between cereals. In addition, some cereals such as rice, oats and barley retain their husk during threshing and this must be removed to produce acceptable foods for humans. Bran is a technical fraction from the milling industry. It generally comprises the fruit wall, seed wall, aleurone layer, germ and smaller amounts of the starchy endosperm. The composition of a bran fraction is highly dependent on the milling technology and type of grain used (Kamal‐Eldin et al. 2009).

Pseudocereals such as amaranth, quinoa and buckwheat are not members of the grass family, but because of the high starch content in their seeds and their use in cereal‐like products, it has been suggested that they should be classified as whole grain together with the cereals in the grass family (Frølich and Åman 2010). These seeds contain no gluten and are therefore suitable alternatives for people with celiac disease. Certain pulses or grain legumes are other seeds with a high content of starch that can be used in different types of cereal‐like products. Because of the characteristics of these, it could be argued if they should also be included in the definition of whole grain; however, they are generally not regarded as such.