Effect of Lipase Combined with α-Amylase on Retrogradation of Bread

Abstract

The effects of purified lipase and α-amylase were tested for the retrogradation of starch in bread and their impact on some rheological properties. The combined addition of lipase and α-amylase increased significantly the loaf volume compared with the control, and the farinograph data showed that combined addition shortened the arrival time and slightly increased the stability time of dough. The addition of lipase alone increased the gelatinization enthalpy of starch (Δh₁) of dough and the starch-lipid complexes (Δh₂) of dough and bread by DSC. After 5 days storage, the retrogradation rate of bread which was estimated by the change of Δh₁ was slowed to 1.73 fold that of control by addition of 1000 units lipase alone, while the combined addition of lipase and α-amylase (100 units) slowed the retrogradation rate to 2.65 fold. The changes of firmness and moisture content in bread crumbs seemed to correlate with these DSC data. These results suggest that lipase alone retards retrogradation of bread during storage, whereas the combined addition of lipase and α-amylase affects it greatly. The addition of lipase increased the amount of Δh₂, suggesting a retardation effect of retrogradation, but Δh₁ decreased during storage, which suggests that lipase could retard the retrogradation of bread.