Date of Graduation

5-2020

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Food Science

Advisor/Mentor

Atungulu, Griffiths

Committee Member/Reader

Howard, Luke

Committee Member/Second Reader

Sadaka, Sammy

Abstract

Formation of harmful microbes and their associated mycotoxins on rough rice during storage present negative socioeconomic impacts to producers and consumers. The objective for this study was to investigate the impact of treating rough rice with selected infrared (IR) wavelengths at different IR intensities and heating durations, followed by a tempering step for further inactivation of microbes (mold and bacteria) on the grain. Freshly-harvested long-grain, hybrid, rough rice (XL 745) with initial moisture content (IMC) of 18.4% wet basis (w.b.) was used. Two-hundred grams (200 g) of the samples were treated at different IR wavelengths (λ) which were 3.2, 4.5, and 5.8 μm for 10, 20 and 30 seconds (s) at product-to-emitter gaps of 110, 275, 440 mm. This was then followed by tempering the grain; putting them in air-tight jars and held at a constant temperature of 60 oC for 4 hours (h). The inoculated Petrifilm plates for mold and bacterial analyses were incubated at 25oC for 120 h and 35oC for 48 h respectively. . The samples treated at wavelength 3.2 μm (product-to-emitter gap 110 mm) for 30 s showed the highest reduction in mold and bacterial load; approximately 3.11 and 1.09 log reduction in the mold and bacterial loads, respectively. Tempering treatment further reduced the microbial load at each IR treatment condition. Molds showed more susceptibility to the IR decontamination than bacteria population. This study provides useful information on the effectiveness of IR heating and tempering on microbial inactivation on rough rice.

Keywords

Wavelength; intensity; infrared; rough rice; microbes

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