Optimization of parboiling conditions and nitrogen fertilization for brown rice quality: textural properties, phytic acid content, and mineral composition

A 5-level, 3-factor central composite rotatable design in response surface methodology (RSM) was used to optimize the effects of parboiling operating parameters (soaking temperature (SoTe, 39.8-90.2°C)and steaming time (StTi, 8.3-16.7 min)) and nitrogen fertilizer (NF, 46.4-113.6 kg ha -1 ) levels on physicomechanical (hardness and ∆E color values) and nutritional properties (zinc (Zn), iron (Fe), calcium (Ca), phytic acid (PA), and PA/Zn) of protein-rich brown rice.Sensory evaluation showed that consumers preferred rice grains with a relatively soft texture and medium hardness.The experimental data fit well to second-order polynomial models (R 2 ≥ 0.976) using multiple regression analysis.The optimum conditions for maximizing mineral content (Zn: 385.0 ppm, Fe: 78.0 ppm, Ca: 33.0 ppm), minimizing PA content (130.91 mg 100 g -1 ), PA/Zn ratio (0.34), achieving a low ∆E value (4.71), and obtaining the desired hardness (17.0 N) were 59.29°C SoTe, 11.18 min StTi, and 90.89 kg ha -1 NF.K e y w o r d s: rice (Oryza sativa L.), parboiling, N fertilizer, antinutritional factor, minerals, process optimization