Date of Graduation

8-2017

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Siebenmorgen, Terry J.

Committee Member

Atungulu, Griffiths G.

Second Committee Member

Mauromoustakos, Andronikos T.

Keywords

Fissures; Rice Drying; Rice Quality; X-ray Imaging

Abstract

Fissured rice kernels break during milling, leading to head rice yield (HRY) reductions. Conventional fissure detection instruments cannot be used to observe fissures in rough rice kernels, the form in which rice in normally dried and stored. X-rays can penetrate hulls allowing visualization of the internal structure of a rough rice kernel. This study evaluated the capability of X-ray imaging to adequately detect fissures in rough rice and established a correlation between HRY and the fissured kernel percentage (FKP) in a rough rice sample. Fifteen long-grain rice cultivars, harvested in Arkansas in 2015 and 2016 were dried using heated air at 60ºC, 10% relative humidity (RH) for various combinations of drying durations and post-drying treatments that resulted in varying degrees of fissuring and HRYs. Fissure detection was conducted using an X-ray system with rough rice and compared to that of a grainscope, a conventional fissure detection instrument, with brown rice. A strong correlation (R^2 = 0.95) was shown to exist between sample HRY and the FKP of the rough rice sample after drying, resulting in a regression equation that could be used to estimate HRY. Having confirmed the impact of fissured kernels on HRY, the X-ray system, with an augmented drying apparatus, was used to evaluate the impact of kernel thickness and moisture content (MC) on rice fissuring. Two long-grain rice cultivars were harvested in Arkansas in 2016, each at two MC levels (high and low), and fractionated into three thickness fraction sub-lots (thin, medium, and thick). The fissuring susceptibility of kernels from each sub-lot was evaluated during drying. Generally, with increase in kernel thickness, the FKP increased for high-MC lots. In regards to MC, high-MC had greater FKPs than the low-MC lots. Overall, these findings show the importance of kernel fissuring to the rice industry, and highlights the role of kernel properties on fissuring during drying.

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