Date of Graduation

8-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Food Science (PhD)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Griffiths G. Atungulu

Committee Member

Sammy Sadaka

Second Committee Member

Steven Foley

Third Committee Member

Frank Carbonero

Fourth Committee Member

Andy Mauromoustakos

Keywords

Infrared radiation, Mycotoxigenic fungi, Shelled corn, Aspergillus flavus, Microbes on grain

Abstract

Selective Infrared (IR) heating holds great potential to decontaminate spores of unsafe fungi in corn. The objectives for this study were to investigate the impact of exposing corn to infrared energy at selected peak wavelengths (λ), infrared intensities and treatment durations, followed by tempering for further inactivation of microbes on the grain and explore a method for decontaminating Aspergillus flavus (A. flavus) spores on corn. Freshly harvested corn with initial moisture contents (IMCs) of 16%, 20%, and 24% wet basis (w.b.) were used. The corn samples were treated at different infrared wavelengths (3.2, 4.5, and 5.8 μm) for 20, 40 and 60 s at product-to-emitter gap sizes (PEG) of 110, 275, 440 mm. This was then followed by tempering the grain at 70oC for 4 hrs. Fungal analyses were assessed in terms of colony forming units per gram of treated corn (CFU/g). Internal transcribed spacer (ITS) amplicon sequencing techniques were also used to identify and quantify the magnitudes of surviving fungi following treatments. The mean of the mold count of control samples were 5.95 ± 0.1 Log (CFU/g). Samples treated at wavelength 3.2 µm, PEG of 110 mm (intensity of 15.71 kW/m2) and heating duration of 60 s resulted in the highest microbial load reduction of 3.0, 4.7, 4.9 Log CFU/g of grain for MC 16%, 20%, and 24% (w.b.), respectively. Tempering treatment further reduced the microbial load at each infrared treatment condition. Aspergillus genus was the most abundant mycotoxin producing fungi on the non-tempered corn samples while Penicllium was the most abundant on the tempered samples compared to the population of other fungi. After samples were inoculated with A. flavus, treatments at wavelength of 3.2 µm, product-to-emitter-gap sizes (PEG) of 110 mm and corn MC of 24% wet basis (w.b.) resulted in the greatest A. flavus load reduction of 4 Log CFU/g for non-tempered and tempered samples. This work showed that decontamination of harmful fungi, known to exist on corn, may be enhanced by infrared treatments at selected wavelengths.

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