a. Pea Protein Concentrate and Isolate
Peas can be fractionated into constituents of protein, fibre and starch. Pea protein concentrate (PPC) is derived from the air classification of ground peas; pea protein isolate is produced either by ultrafiltration or acid precipitation of solubilized pea protein (Le Guen et al. 1993 {1340}). Both products contain higher crude protein than raw peas. Pea protein isolate is devoid of carbohydrates and antinutritive factors whereas the simpler process of air classification has no apparent effect on either. Pea protein isolate may contain as much as 90% globulins with albumins reduced to 10%. This results in a lower sulfur amino acid content but more digestible product as globulins have a higher digestibility than albumins (Fan and Sauer 1994 {1292}). For example, nitrogen ileal digestibility increased for pea protein isolates produced from spring pea Finale (69.1 to 83.7%) and winter pea Frijaune (69.5 to 85.4%) (Le Guen et al. 1993 {1340}).
When fed to 21 day old piglets ( 5 kg) PPC fed animals
grew more slowly due to a significantly lower feed intake (262g
d-1 as compared to 448g d-1 on the soybean
meal diet). Although PPC generally contributes to pellet hardness,
in this case the PPC pellets were more friable making the feed
powdery and unappealing. Poor digestion of the PPC may have also
resulted from the concentration of oligosaccharides or other ANF.
The recommendation by the authors was that PPC should be restricted
to 10% or less of the total diet for weanling pigs (Christison
and Solano 1982 {1469}).