Air classification of pea flour–analytical studies

The pea‐milling and subsequent air classification of whole peas was investigated on laboratory scale equipment. Two approximately linear but divergent calibration graphs were constructed for the air classifier based on two different definitions of particle size cut‐point. At high classifying speed (11 000 rev min −1 ) a fine fraction or protein concentrate was produced containing 55.1% protein (cf. 22% in original flour) although this represented only 29% of the total protein. The yield of protein in the fine fraction could be increased by using a three‐stage milling and classifying procedure, although the actual protein content of the concentrate remained more or less the same. This procedure also had the effect of reducing protein contamination of the starch (coarse) fraction. Other effects of air classifying observed included the concentration of the lipid component into the fine fraction and the rough fractionation of the fibre constituent between the coarse (testa) and fine (cell wall material) fractions. Various aspects and problems associated with the use of air classification for the preparation of pea protein concentrates are discussed.