In a groundbreaking patented process outlined by Chiu et al. (1998), starch undergoes a transformative journey through controlled heating. Maintaining moisture levels below 15%, this method exposes starch to temperatures ranging from 100°C to the onset of thermal degradation. The result? Products boasting acid, shear, and temperature tolerances comparable to chemically cross-linked starches. Notably, a low-moisture environment and alkalinity play pivotal roles in facilitating this remarkable transformation.
Exploring Fluidized Bed Heating
Introducing a novel approach, the use of a fluidized bed emerges as an intriguing method for heating starch. However, it’s essential to note that this process has primarily been explored with amaranth flour, as investigated by Gonza´lez et al. (2007a,b).
Microwaves: A Spectrum of Innovation
Understanding Dielectric Heating:
Microwaves, a form of electromagnetic radiation, operate within wavelengths of 1 mm to 1 m and frequencies from 300 MHz to 300 GHz. Dielectric heating, a key phenomenon, occurs when microwave energy is absorbed by water. As succinctly described by BeMiller and Huber (2015), microwave irradiation proves transformative only when starches lack sufficient water content for gelatinization and pasting.
Microwave Radiation Treatment Insights:
In a comprehensive review by Brasoveanu and Nemtanu (2014), fourteen papers on microwave radiation treatment of starches were scrutinized. Notably, one paper within this corpus delved into starches with less than 15% moisture, making it a standout in exploring conditions divergent from high-moisture treatment (HMT).
Distinguishing Microwave from Conventional Heating:
Crucially differentiating from conventional methods, microwave heating occurs in open settings, impacting moisture content during treatment. Szepes et al. (2005) demonstrated this by irradiating maize and potato starches, showcasing moisture content reductions to 0.00% and 0.07%, respectively, within 15 minutes.
Effects on Crystallinity and Properties:
Szepes et al. (2005) illustrated intriguing shifts in crystallinity and properties due to microwave irradiation. For potato starch, crystallinity rose from 55% to 66%, accompanied by a shift in crystal packing. Meanwhile, maize starch saw a decrease from 85% to 30% in crystallinity.
Microwave Magic on Cassava Starch
In a separate study by Colman et al. (2014), microwave irradiation of cassava starch with less than 18% moisture yielded intriguing results. Peak viscosity witnessed a slight increase after a 5-minute treatment, followed by a considerable decrease in 10- and 15-minute treatments.
Conclusion: Microwaves Paving the Way
The utilization of microwaves in starch treatment unveils a spectrum of possibilities, from patented heat processes to fluidized bed heating and beyond. As researchers continue to push boundaries, microwave innovations promise transformative outcomes in the realm of starch modification.