Date of Graduation

5-2016

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Griffiths G. Atungulu

Committee Member

Sammy Sadaka

Second Committee Member

Ruben Morawicki

Third Committee Member

Tanja McKay

Keywords

Biological sciences; Applied sciences; Functional characteristics; Infrared heating; Rice quality; Rough rice; Tempering

Abstract

Rough rice is normally harvested at moisture contents (MCs) higher than that for safe storage. The objective for this study was to investigate the effectiveness of scaled-up infrared (IR) heating followed by tempering steps to dry freshly-harvested rough rice. An industrial type, pilot scale, IR drying equipment, designed to convey rough rice on a vibrating conveyor belt was used in this study. The heating zone of the equipment had catalytic IR emitters powered by natural gas. Freshly-harvested rough rice of long-grain pureline (cv. Cheniere), long-grain hybrid (cv. 6XP 756) and medium-grain (cv. CL 271) cultivars at initial moisture contents (IMCs) of 23%, 23.5% and 24% w.b, respectively were used. Rough rice samples, at loading rate of 1.61 kg m-2 were heated with IR energy for 30, 50, 90 and 180 s followed by tempering at 60C for 4 h; the IR heating intensity was 5.55 kW m-2, at product-to-emitter-gap size of 450 mm, and in one- and two-pass drying operations. The effects of IR treatments followed by tempering on percentage points of moisture removed, head rice yield, energy use, rice color, and pasting characteristics were evaluated. For all the cultivars, percentage point moisture removed increased with increase in IR drying duration. For all rice cultivars, one-pass IR treatments for 180 s resulted in head rice yield significantly lower than that of rice dried using natural air in controlled environment conditions set at 26ºC and 65% relative humidity (p < 0.05). Energy required to dry rice increased with increase in drying duration. Viscosity values of all the experimental samples were significantly greater (p value < 0.05) than that of the control samples for all the cultivars except those IR treated for 180 s. There was a significant difference (p<0.05) in the color index (ΔE) of treated samples and the controls. In conclusion, the study provided information crucial to understanding the effects of scaled-up radiant heating and tempering of rough rice on drying rates and rice quality for long-grain pureline, long-grain hybrid and medium-grain rice cultivars.

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