This study investigated the effects of broadband and selected infrared (IR) wavelength treatments of rough rice on microbial inactivation. Rough rice was treated at different IR wavelengths and product‐to‐emitter distances (110, 275, and 440 mm) followed by tempering at 60°C for 4 hr. The total mold and aerobic plate counts (APC) on non‐treated and treated samples were determined. Significant total mold reductions of 1.14 and 3.11 log CFU/g were obtained after IR heating using broadband and selected wavelengths, respectively (p < .05). The most significant reduction of APC using selected IR wavelength was 1.09 log CFU/g; the broadband IR wavelength had no effect on the mean APC. The IR treatments followed by tempering step resulted in greater reductions of total mold counts and APC (4.03 and 3.50 log CFU/g) in comparison to IR treatments without tempering (3.11 and 1.09 log CFU/g). Overall, bacteria showed more resistance to IR treatments than molds.

Mycotoxigenic fungal contamination of corn poses significant health-related risks to consumers (Shad and Atungulu, 2017; Atungulu et al., 2018). The most prevalent mycotoxins that contaminate corn in the United States include aflatoxins, fumonisins, and deoxynivalenol (Abbas et al., 2002; Mohammadi Shad et al., 2019b; Robens & Cardwell, 2003; Wu et al., 2011). Chauhan et al. (2016) conducted a study on fungal infection, and aflatoxin contamination in corn collected from the Gedeo zone in Ethiopia and found that Aspergillus (75%), Fusarium (11%), Penicillium (8%), and Trichoderma (6%) were the predominant genera of fungi that contaminated the corn grains. Aflatoxins (produced by Aspergillus), deoxynivalenol, and fumonisins (produced by Fusarium) were also found in locally grown corn in 18 African nations during 2007 and 2008 (Probst et al., 2014). Lane et al. (2018) also found that Fusarium was the most abundant genus after exploring the fungal microbiome of corn during hermetic storage in the United States and Kenya.

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Commercial application of infrared (IR) heat has been hampered by a lack of readily available data adaptable to high‐throughput (HT) drying requirements in the grain processing industry. This study evaluated the effectiveness of a continuous flow IR heating system to simultaneously dry and decontaminate corn over various drying bed thicknesses (1.5, 2.7, and 4.5 cm). Additionally, impacts of intermediate tempering treatment and variation of IR emitter angle (zero [E‐0] and 30 [E‐30] degrees) on drying and decontamination of the corn were determined. Although IR heating was able to dry and decontaminate corn at the initial moisture content (MC) of ≈21% wet basis (w.b.), moisture removal was most effective at the least bed thickness (1.5 cm). At 1.5 cm bed thickness, a safe storage MC (<14%) was achieved after 15 min of IR heating. At all the bed thicknesses, IR heating with intermediate tempering resulted in higher fungal inactivation than IR heating without tempering. Infrared heating of corn at 1.5 cm bed thickness plus tempering resulted in a total fungal count (TFC) reduction of 3.1 and 4.6 log CFU/g using IR emitters at E‐30 and E‐0° angles, respectively. However, increasing the bed thickness to 2.7 cm resulted in a TFC reduction of 4.8 and 4.6 log CFU/g using E‐30 and E‐0, respectively. Infrared heating using E‐0, compared to using E‐30, accelerated TFC reduction when corn samples were dried at 1.5 cm bed thickness. These results could help guide the design of HT corn drying and decontamination systems.

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