Effect of soaking and single/two cycle high pressure treatment on water absorption, color, morphology and cooked texture of brown rice.

Water absorption, color, morphology and cooked texture of brown rice were evaluated after selected soaking (30-50 °C, 30 min) and high pressure treatment (HPT) (100-500 MPa; single or two cycle; total holding time 10 min). Water absorption ratio and lightness values of brown rice were increased by soaking and HPT. Hardness and gumminess values of cooked brown rice were reduced while springiness and cohesiveness were elevated by HPT. Scanning electron microscopy indicated that HPT improved the texture of brown rice by disrupting the structure of rice bran layer, which allowed easier water penetration into the rice grain during cooking. Moreover, the two cycle HPT resulted in lighter color and softer texture for cooked brown rice than single cycle HPT primarily caused by the more severe structural disruption of bran layer. Overall, two cycle HPT after soaking could potentially improve the quality of brown rice, taking about the same time as the single cycle HPT. Further, the quality improvements with the two cycle HPT were facilitated at lower pressure levels thereby providing better commercial processing opportunities.