The main purpose of the present study is creation of optical standard scale and quality evaluation parameters when studying of lemon fruits (Citrus aurantifolia) at different maturity stages. The lemon fruits were classified into six stages of maturity according to their color graduation from green to yellow color. The physical, mechanical and chemical properties of lemon fruit were measured. A laser light source with wavelength 543.5 nm with power 4 mW was used, to measure the optical properties of lemon fruits. Each sample was imaged with CCD camera, these images were chromatically analyzed with RGB scale by software program. The results showed that: 1- The main dimensions, mass and volume of lemon fruits were gradually increased. Meanwhile, the peel thickness and the density were gradually decreased with lemon maturity stages, 2- The friction angle of lemon fruits was gradually increased, meanwhile the required force to penetrate the lemon fruits and the firmness were gradually decreased with lemon maturity stages, 3- The juice percentage, total soluble solids (TSS), total sugars and the percentage of acidity were gradually increased, meanwhile the pH value of the lemon fruits was gradually decreased, with lemon maturity stages, 4- The light reflectivity was decreased, meanwhile the light absorptivity intensity was increased as the fruit gradually matured from stage one to stage six., 5- By decreased density of light reflection from fruit surface, the juice, total soluble solid, total sugar and the acidity percentages were increased, pH value was decreased, On the other hand, in the case of density of light absorption percentage was increased and 6- The color analysis (RGB) of fruits color images showed that the red color component was gradually increased, meanwhile each of green and blue color components were gradually decreased as fruits matured from stage 1 to 6.
Therefore, there is potential for use of laser light to determine the maturity stage of lemon fruits and color analysis of fruits images to distinguish the maturity stage of lemon fruits