Light Transmission Properties of Lentil (Lens culinaris Medik.) Seed Coat and Effect of Light Exposure on Cotyledon Quality
Cotyledon color is one of the most important quality criteria in the lentil market because the color may correlate well with other quality attributes. Therefore, cotyledon color is an important quality criterion in lentil breeding programs. The objectives of this work were to investigate the variation in optical properties among lentil seed coat types and to determine the effect of light treatment, seed coat presence, and seed coat type on color loss in lentil cotyledon. Light transmission properties of seed coat types were obtained to find out if they differ in their light-blocking ability and protection of the underlying cotyledon from photodegradation. Light reflectivity was measured to investigate if there are recognizable patterns, which might be useful in market class discrimination, quality prediction and disease detection in the seeds. A fiber-optic spectrometer was used to obtain spectral reflectivity and transmission properties of seed coats of 20 lentil genotypes. The reflectivity (0°\32°) and nadir-aligned transmission spectra were measured in the 250 nm to 850 nm wavelength range. An Analysis of Variance (ANOVA) showed that there were significant (p<0.05) differences in light transmission properties of the major seed coat types. A computer vision system was used to study the influence of light exposure on the cotyledon color of red, green, and yellow lentils. Twenty samples from each of the three cotyledon color classes were subjected to six levels of light treatment, namely ultraviolet, full-spectrum visible, red, green, blue, and control (dark) for seven days, at room temperature. This light exposure had a significant effect on all three cotyledon color classes. The effect size was largest in green lentils, smaller in yellow, and least in red lentils. Having established the light-blocking characteristics of the various seed coats and realizing that light exposure does affect the color of lentil cotyledon, the protective effects of different kinds of seed coat against light-induced cotyledon color change was tested. Results showed that some whole green cotyledon lentils experienced color losses in the underlying cotyledon. Red and yellow lentil classes had high levels of colorfastness, and their seed coats successfully protected the cotyledon from these minimal effects. Thus, breeding for seed coat protection may not improve the cotyledon color of Canadian red lentils (the most de-hulled market class), but it may improve the overall quality of green lentils.
Lentil, Light transmission, reflectivity, optical properties, fiber-optics, spectroscopy, machine learning, light, color, seed coat, cotyledon.
Master of Science (M.Sc.)
Chemical and Biological Engineering