Effect of Maitake (Grifola frondosa) Mushroom on the Physical Properties and Protein Profile of Cooked Rice

Abstract

The aim of this work was to study the effect of Maitake proteases on the textural properties of cooked rice. We also investigated alterations in the molecular weight distribution of proteins and levels of free amino acids in rice after soaking in Maitake extract at 50°C. When rice was soaked and heated with Maitake extract, the texture of cooked rice was softer than rice cooked with water both immediately after cooking and post-refrigeration. Our results showed that when the rice grains were soaked in Maitake extract at 50°C for 60 min, Maitake metalloproteases degraded rice glutelin, resulting in an increased level of hydrophobic amino acids such as phenylalanine, valine, and isoleucine. Moreover, we demonstrated that aspartic proteases from Maitake also degraded the rice proteins, without affecting their SDS-PAGE patterns. Finally, when the rice was cooked with Maitake extract, Maitake metalloproteases decomposed the glutelin and contributed to an apparent decrease in rice hardness.