Cereal Chem 64:144-149   |  VIEW ARTICLE

In Vivo and In Vitro Protein Digestibilities of Regular and Mutant Barleys and Their Isolated Protein Fractions.

R. S. Bhatty and J. R. Whitaker. Copyright 1987 by the American Association of Cereal Chemists, Inc. 

Apparent protein digestibility (APD) of three pairs of parent and mutant barleys, Bomi and Riso 1508, Carlsbert II and Riso 86, Carlsberg II and Riso 56 grown under identical environments, mutant ANT-13-13, and Abee (a Canadian feed barley) was determined by in vivo (mouse feeding) and two in vitro procedures. The ANT-13-13 mutant had the highest in vivo APD. The in vivo APD of the mutants was lower, except in the Carlsberg II and Riso 56 pair, than those of the parents and seemed positively correlated with an vitro digestibility. Albumin plus globulin, hordein, and glutelin protein fractions isolated from one pair of parent and mutant barleys (Carlsberg II and Riso 86) and hydrolyzed in vitro with pepsin, trypsin, alpha- chymotrypsin, and peptidase showed the hordein fraction to be more susceptible to the mammalian proteases than the albumin plus globulin or the glutelin protein fractions. Wet heat improved digestibility of the protein fractions by pepsin, but both dry and wet heat reduced protein digestibility by trypsin. Treatment of the protein fractions with alpha-amylase before their hydrolysis improved their in vitro digestibility, particularly that of the glutelin fraction, both by pepsin and trypsin. The three protein fractions were poorly digested by the protozoan, Tetrahymena thermophila, compared to bovine serum albumin. Predigestion of the protein fractions with pronase for 3 hr at 55 C slightly improved their utilization. Under these conditions, the organism grew most on the hordein fraction, least on the glutelin fraction; the albumin plus globulin fraction was intermediate in promoting growth.