Potential of near infrared spectroscopy for non-destructive estimation of soluble solids in growing melons

Non-destructive determination of soluble solids (degreesBrix) in harvested fruits using near infrared (hereafter, NIR) spectroscopy has been reported by many researchers. We have just reported on non-destructive estimation of degreesBrix in harvested melons using a NIRSystems Model 6500 spectrophotometer (Ito et al., 2000). There is a cultivated variety that is difficult to judge harvest time from external appearance. If we can determine degreesBrix in growing fruits non-destructively in the field, immature fruits will not be harvested. A portable NIR spectrophotometer for field use has been just developed by Kubota Corporation. The spectral data of growing melons in a plastic greenhouse were measured by the portable spectrophotometer. A commercial program was used for multiple linear regression analysis. degreesBrix in the growing melons could be estimated by a multiple regression equation calibrated with harvested melons. Absorbances of 906 and 874 nm that are key wavelengths for non-destructive degreesBrix determination were included in the multiple regression equation as the independent variables. Therefore, it was concluded that degreesBrix in growing fruits could be determined non-destructively in the field.