Methodology for nondestructive inspection of citrus maturity with machine vision

Non-destructive maturity evaluation of fruits is the key to harvesting and sorting of fruits according to their maturity. In order to explore a methodology for the maturity inspection of citrus with machine vision technology, the surface color information and the ratio of total soluble solid to titratable acid (TSS/TA) were used as maturity indexes of citrus. The spectral reflectance characteristics of different color citrus were determined by use of a UV-240 ultraviolet and visible spectrophotometer. The results stated that at the wavelength of 700 nm, the green surface and saffron surface of citrus were of higher spectral reflection, the difference between them reached the maximum, about 53%, and the image acquired at this wavelength could be of much color information for the maturity inspection. At last, the maturity of 72 citrus was evaluated by the discriminate analysis and covariance matrix. The test results showed that the identification accuracy was 91.67%. It was concluded that the maturity of citrus was related to their surface color information, and it is feasible to nondestructively evaluate the maturity of citrus with the machine vision system.