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Physical and Functional Characteristics of Broken Rice Kernels Caused by Moisture-Adsorption Fissuring

Mukhopadhyay, Sangeeta, Siebenmorgen, Terry J.
Cereal chemistry 2017 v.94 no.3 pp. 539-545
adsorption, brown rice, cultivars, functional properties, milling, rice flour, seeds, viscosity, water content
Fissuring caused by rapid moisture adsorption generates broken kernels upon milling; brokens are often ground to flour. The recent increase in demand for rice flour has promoted interest in brokens. This study investigated the physical and functional characteristics of brokens resulting from milling lots with various levels of moisture adsorption-induced fissuring. Two long-grain (LG) cultivars and one medium-grain (MG) cultivar were conditioned to five initial moisture contents (IMCs), rewetted, and then reconditioned to 12% moisture content. Brown rice fissure enumeration and milling analyses as well as size distribution and functionality analyses of brokens were conducted. As IMC decreased, the percentage of fissured kernels increased and, consequently, the amount of brokens generated increased. Although the number of fissures/kernel also increased with decreasing IMC, the mass distribution of the resultant brokens was not affected by IMC. Across all IMC levels, the mass percentage of the medium-sized brokens was greatest for the LG cultivars, whereas that of the large-sized brokens was greatest for the MG cultivar. Regardless of IMC, peak, setback, and final viscosities were greatest for head rice and decreased significantly with decreasing size of brokens. Thus, brokens of different sizes have different functional properties and, hence, may be fractionated for different end-use applications.