Protein isolation from jet milled rye flours differing in particle size

A commercial rye flour (R) was solubilised by mixing at different ratios with three solvents, namely ΝaOH solutions, HCl solution and deionised water. The highest protein extracted content (74.27%) was reported for a flour: 0.02 M NaOH solution ratio of 1:14. After solubilisation at the defined optimum condition, precipitation was performed at different pH values (3-7). The best performance on the basis of protein recovery was found at pH 5.5. The optimum conditions for both solubilization and precipitation of rye flour proteins were applied to rye flours (R1, R1A and R1B) differing in their particle size. Flours R1A and R1B resulted from pulverizing flour R1 by a jet mill at a feed rate of 3.35 and 1.17 kg/h, respectively. In contradiction to the expected in terms of smaller particle size, greater protein recovery percentage was achieved for both R1 and R1B flours. As the formation of aggregates seem possible, the duration of the isolation procedure as well as the duration and the speed of the centrifugation seem to be important for the explanation of our findings.