The grain of wheat is a seed with a structure similar to that of the rice grain. The outer coverings, pericarp and testa, are hard, fibrous and indigestible. Beneath them is the aleurone layer, which is rich in B complex vitamins and proteins. These outer layers form about 12% of the grain.
The distribution of nutrients in the grain is not uniform. The germ and the scutellum are rich in protein, B vitamins and the germ, in vitamin E. The scutellum contains about one half of the thiamin in the grain.
Wheat usually eaten as wheat flour. During milling the outer layers are removed. Usually the germ and the varying proportions of the outer layers are separated from the bran and the white flour obtained is nearly all starch, the outer coverings been removed as bran. The nutritive value of the flour will therefore depend on the proportion of the grain that remains in the flour. The proportion of the grain in the flour is referred to as the "extraction rate". The lower the extraction rate the whiter flour and lower its nutritive value.
Before World War II very few person in Sri Lanka ate bread or other preparations of wheat flour, so that little was imported. All four meals eaten by Sri Lankans were based on rice. The morning meal consisted of preparation of rice flour, such as hoppers, string hoppers, pittu, roti and the midday meal and the night meal consisted of rice and curry. Many persons had an afternoon snack, reported to as "tiffin". The richer folk could afford sandwiches of bread and butter, with an occasional potty as a piece of cake, made of wheat flour. Other had various rice flour preparations such as aluwa, kavum, kokis. The only wheat flour preparation available freely was "hulang -viskothu". Dr. Lucian Nicholls, during dietary surveys conducted indifferent parts of the country, found that 16 to 18 ounces (450 to 500 grams) of rice and rice flour preparations were consumed each day by the common people. When other starchy foods were available in season, rice was supplemented with yams such as jak and breadfruit and roots such as manioc, batala, wel-ala and kiri ala. Always the local production of rice was grossly insufficient, the British was able to import rice from Burma to make adequate quantities available to provide each individual adult more than 450 grams per day.
Such imports were not possible during the war and wheat and wheat flour was brought in mainly from Australia. The little rice available was rationed, so that each person received at least 225 grams per day. This was supplemented with grained such as bajra.
After the war, wheat flour continued to be imported from Australia, Europe and North America. Food aid came in the form of wheat flour. Later, wheat was brought in as grain, to be milled locally. In 1976 a Singaporean firm presented to propose to the government that they be allowed to construct a modern flour mill at Trincomalee and to convert all wheat brought into the country to wheat flour. Flour of 70% extraction would be given to the government, and the 30% of bran would be property of the firm.
In 1977 the Flour Mill constructed by the Prima Co. is a very large eight storied building. Wheat grain brought in ships is sucked to the upper floor and undergoes various changes which convert the grain to 74% extraction flour, as it passes from one floor to the next. At the lowest floor flour is packed into bags which then become the property of the Food Commission. At each stage samples were collected and taken to the laboratory for quality analysis. The mill is kept very clean and mill maintained and the workers are well disciplined. An officer of the Sri Lanka Standards Institute, who spent a few days at the mill, expressed satisfaction of the milling process as well as measures taken for quality control.
The flour remains at 74% of extraction, with very little of the nutrients present in the grain. Very major and expensive change will have to be made in the machinery if the extraction rate is to be increased. Less drastic changes could be effected to fortify this flour with nutrients such as vitamin B complex and iron.