Grain chalkiness
The grains affected by chalkiness are characterized by opaqueness and chalky texture because of the interruption of final grain filling. This kind of damage is genetically controlled, other than being favored by high temperature stress during early ripening (Ishimaru et al., 2009; Okada et al., 2009; Lanning et al., 2011), which cause weak kernels, more susceptible to breakage during milling processes (Siebenmorgen et al., 2013).
Chalkiness can be classified in four types based on the grain area affected by the damage as shown in Figure 7.
Figure 7. Types of rice grain chalkiness.
Milky White kernels: this condition is when the rice is entirely opaque due to poorly developed starch granules in the center of the endosperm (Figure 8). In general, this rice is slender with non-uniform shape. It is treated as screenings.
White Core kernels: starch granules in the central cells of the endosperm develop poorly. Although undesirable for table rice, this characteristic is often considered favorable for brewer’s rice (i.e. sake).
White Belly kernels: this is rice with white, opaque areas on the belly or ventral side of the grain. The white area is a result of poorly developed starch granules in the peripheral layers of the endosperm. It is caused by insufficient transport of carbohydrates to the rice grain during ripening. White belly generally does not degrade the quality of the rice.
White Base kernels: the kernels are characterized by an immature and chalky area in the basal region of the endosperm.
White Back kernels: the kernels have a chalky area at the dorsal part of the endosperm
Figure 8. Scanning electron micrographs of amyloplasts in the center part of rice grain. E: control, G: sample exposed to high temperature (Ishimaru et al., 2009).
Currently in the UNIMI.CropQuality component implements models simulating:
Furthermore a model considering the chalkiness degree of rice productions is available.
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