Date of Graduation

12-2012

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Wang, Ya-Jane

Committee Member

Siebenmorgen, Terry J.

Second Committee Member

Mauromoustakos, Andronikos T.

Keywords

Biological sciences; Accelerating of aging; Heat treatments in rice; Physicochemical properties; Rice aging; Rice change during storage; Rice properties

Abstract

During storage, the milling and physicochemical properties and eating quality of rice change, which is generally termed `aging'. Aged rice is preferred by processors, and there are attempts to develop accelerated aging process using various heat sources. In this study, the effects of various heat treatments and their influence on the milling, pasting, thermal, and cooking properties of two long-grain rice cultivars during storage were investigated using a full-factorial experimental design. Two long-grain rice cultivars, Wells and XP723, was treated with 8 different heat treatments including one control and stored at room temperature for 180 days. Heat treatments included 2 levels of UV irradiation, 2 levels of autoclaving and 3 levels of convection oven. The heat treatments significantly influenced head rice yield and thermal properties. The surface lipid content and cooked rice hardness and stickiness were impacted by cultivars, heat treatments and storage with different extent showing 3-way interactions. Severe autoclaving resulted in different protein composition from the other treatments. Peak pasting viscosity significantly increased at the first 3 months and gradually leveled off regardless of cultivar and heat treatments. Leached solid contents were decreased gradually during storage. Autoclaving (especially severe autoclaving) samples showed more distinct characteristics on HRY, leached solids and cooking properties. Although different heat treatments had different impacts on their properties, the results show that the various heat treatments employed in this

study slightly accelerated rice aging by stabilizing rice properties during storage.

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