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New technologies for measuring chalkiness in rice
T. SIEBENMORGEN (1). (1) Univ of Arkansas, Fayetteville, AR, U.S.A.
Chalkiness is a condition in which portions of rice kernels appear opaque, versus a typically-desired translucent appearance. Chalkiness is generally believed to be caused by a disruption in starch synthesis during the kernel-filling period, leading to loosely-packed starch granules. Chalkiness can appear in various kernel locations, or entirely throughout a kernel, with the severity being determined by the timing and level of high-temperature exposure, particularly that of nighttime air temperatures, during kernel filling. These regions of loosely-packed starch not only cause a difference in the way light is refracted through the kernel, but also alter physicochemical properties and resultant processing performance. Thus, it is important to be able to assess the chalkiness level of rice samples. The Federal Grain Inspection Service (FGIS) defines chalky kernels as “whole or broken kernels of rice which are one-half or more chalky” and measures chalk levels using a visual technique of quantifying the mass percentage of kernels in a sample that each have more than 50% of the kernel volume as chalk. New imaging systems offer more rapid means of indicating chalkiness levels. The Winseedle™ (WinSeedle Pro 2005a) and SeedCount (SC5000TR) instruments are two such systems. Once calibrated, the instruments scan a set number of kernels to determine the number of pixels associated with both chalky and non-chalky tissue, and then calculate the percentage of the total-kernel area that is chalky. This presentation describes the use of each instrument and reports the findings of a study in which chalk levels measured on an area-basis, as indicated by both imaging systems, were compared to those measured on a volumetric-basis, as determined by the FGIS standard method, using sets of long- and medium-grain rice lots.
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