High pressure treatments largely avoid/revert decrease of cooked sorghum protein digestibility when applied before/after cooking

Abstract

The results obtained in this work showed that high pressure treatments avoid/revert, to a large extent, cooking deleterious effects that decrease sorghum proteins digestibility, when pressure is applied before/after cooking. The best results were obtained when pressure is applied before the cooking process. Digestibility of cooked sorghum proteins increased from 16.1% to 35.3/25.4% when pressure at the level of 300 MPa was applied during 15 min before/after cooking, respectively (the value for uncooked sorghum was 42.1%). When 300 MPa were applied for 5 min before cooking, similar results were obtained for digestibility (36.0%). Analysis of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of sorghum prolamins, revealed that high molecular weight aggregates and a 45 kDa dimer, which usually increase with cooking and are related to protein digestibility decrease, did not significantly change when high pressure is applied. A relationship between Infra-red (IR) spectra and protein digestibility by means of a Partial Least Square (PLS1) regression was assessed, showing changes in proteins and also on lipids and starch. It can be concluded that pressurization of sorghum flour, before or after cooking, particularly the former, is a suitable process to greatly improve cooked sorghum protein digestibility.