Digital imaging analysis of size and shape of wheat and pea upon heating under anoxic conditions as a function of the temperature

Abstract

Three types of experiments were carried out. In the first series of experiments emmer wheat grains (Triticum dicoccum Schubl), var. AR, and peas (Pisum sativum L.), var. RE, were heated at temperatures ranging from 130–700 °C under controlled anoxic conditions for a maximum of 120 min. For each temperature a separate experiment was carried out in a pre-heated tube oven. Image acquisition was carried out on a flat bed scanner with a transparency adapter; for the analysis the image program IMAGE J 1.27 was used. Various size and shape factors are discussed and the definitions of the selected size and shape factors are given. The size and shape were measured and the mean calculated from thirty of the untreated specimens and the charred residues heated at each temperature. The results show a change of size and shape as a function of the temperature. The changes for wheat grains and peas are not identical. It is suggested that the presence of the pericarp enclosing the wheat grains causes this difference. In a second series of experiments it was shown that untreated grains of emmer wheat, bread wheat and macaroni wheat can be separated by measuring the shape, but size varies too much within each species, probably the result of different growing conditions, to be useful for separation purposes. As a result of heating at temperatures higher than 290 °C the shape of the three species becomes identical. This implies that the three species can no longer be separated after being heated, solely on the basis of size and shape. Finally, both emmer wheat grains enclosed by chaff and without chaff were heated under similar conditions. After removal of the chaff from the former, the size and shape of the grains were measured. The results show no significant difference in size and shape between both types.