The Improved Chemical, Mechanical, Rheological, and Pasting Characteristics of Protein-Rich Brown Rice by Parboiling Process Integrated with Nitrogen Fertilization

Abstract

The effects of nitrogen fertilization (NF, 60-100 kg ha-1) and parboiling operation (soaking temperature (SoT, 50-80°C) and steaming time (StT, 10-15 min)) on the protein content (PC), amylose content (AC), gelatinization temperature (GT), hardness value (HV), peak viscosity (PV), trough viscosity (TV), final viscosity (FV), breakdown (BD), setback (SB) point, peak time (PTi), and pasting temperature (PTe) of brown rice were evaluated. Results showed that the GT, HV, FV, and TV were significantly increased by increasing the NF, SoT, and StT levels. An increase in the SoT and StT levels led to a significant reduction in PC, AC, BD, and TV values. The AC (17.13-16.83%) and PV (1605-1588 cP) values were decreased by increasing the NF level, while the PC (8.78-9.46%) and BD (226.9-247.7 cP) values were increased. Rheological parameters of BD (336.4 cP), FV (3608.5 cP), and SB (1843.5 cP) were notably increased using the combined treatment of 100 kg ha-1 NF and of 80°C SoT. The best triple treatments for the improved GT (5.0 °C), HV (19.37 N), as well as FV (3923 cP), and SB (1949 cP) were 60 kg ha-1 NF+80°C SoT+15 min StT, 100 kg ha-1 NF+80°C SoT+15 min StT, and 100 kg ha-1 NF+80°C SoT+10 min StT, respectively.