Surachet Suanjan

Fine soy protein isolate (SPI) powders exhibit poor handling and reconstitution properties, while excessive liquid loading can destabilize fluidized-bed agglomeration. This study evaluated an outlet-air relative humidity (RH)-triggered binder-diversion strategy during pulsed fluidized-bed agglomeration of SPI. Atomization pressure (0.5, 1.0, and 1.5 bar), nominal binder pump setting (3.8, 4.7, and 5.6 mL·min⁻¹), and operating mode (continuous spraying or RH-triggered control at a 70% set point) were investigated. Under continuous spraying, outlet RH showed an overall increase throughout the 30 min process. RH-triggered operation maintained outlet RH near the set point after threshold attainment by reducing the spray duty cycle to 0.67–0.96. This corresponded to 102.6–131.0 mL of sprayed water per run, approximately 4–33% less than continuous spraying at the same nominal pump setting. Compared with continuous spraying, RH-triggered operation produced a lower mean final moisture content in all nine conditions, a higher mean process yield in seven conditions, higher D₅₀ values in all conditions, and a lower mean particle size span in seven conditions. Agglomeration reduced the packing-derived CI and HR and shortened wetting time relative to raw SPI, whereas the effects of RH-triggered operation on flow indices, wetting time, and dispersibility depended on atomization pressure and effective binder delivery. Because the feedback action changed both cumulative binder addition and spray history, the observed product differences represent the performance of the complete RH-triggered control strategy rather than an independent effect of RH stabilization. The findings demonstrate the feasibility of outlet-RH-based adaptive binder delivery during pulsed fluidized-bed agglomeration of SPI.

This research introduced an energy-efficient drying method combining hot-air drying with stepwise microwave heating for producing quick-cooking red beans. Crucial parameters such as the effective diffusivity coefficient (D_e), and specific energy consumption (SEC) were examined across varying conditions with the aim of optimizing the drying condition. The results showed that D_e and SEC varied in a range of 0.53 × 10⁻⁹–3.18 × 10⁻⁹ m²·s⁻¹ and 16.58–68.06 MJ·(kg·h⁻¹)⁻¹, respectively. The findings from the response surface methodology indicated that optimal drying conditions for cooked red beans are achieved at a hot air temperature of 90 °C, a microwave power of 450 W (corresponding to an initial intensity of 2.25 W·g⁻¹), and a rotational speed of 0.2 Hz. These conditions lead to the maximum effective diffusivity coefficient and the lowest specific energy consumption. Further investigations into step-up (150–300 W to 300–450 W) and step-down (300–450 W to 150–300 W) microwave heating modes were conducted to refine the drying process for enhanced energy efficiency. The synthetic evaluation index revealed that step-down microwave heating strategies of 450 W-to-150 W and 300 W-to-150 W, applied at a temperature of 90 °C and a rotational speed of 0.2 Hz, were notably effective. These methods successfully minimized energy use while preserving the quality attributes of the final product, which were comparable to those of traditionally cooked and freeze-dried red beans. The combined approach of hot-air drying with step-down microwave heating presents a promising, energy-saving technique for producing quick-cooking beans that retain their rehydration qualities and texture.