|ZHU, QIBING - Jiangnan University|
|HE, CHUNLIU - Jiangnan University|
|MENDOZA, FERNANDO - Michigan State University|
|CEN, HAIYAN - Michigan State University|
Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2015
Publication Date: 3/1/2015
Citation: Zhu, Q., He, C., Lu, R., Mendoza, F., Cen, H. 2015. Ripeness of 'Sun Bright' tomato using the optical absorption and scattering properties. Postharvest Biology and Technology. 103:27-34.
Interpretive Summary: Maturity is critical in determining the optimal harvest time, appropriate use of harvested tomatoes, and how tomatoes should be handled after harvest. The current standard method for tomato maturity grading is based on visual evaluation of the color of fruit skin, which is subjective and imprecise. A nondestructive, objective method for evaluating the maturity of tomato is thus needed. Light absorption and scattering in the plant tissue are related to its composition, cellular structure and physiological activity. Hence measurement and characterization of light absorption and scattering properties could provide useful information about the maturity and quality of plant products like tomato. This research was therefore intended to evaluate the feasibility of using light absorption and scattering properties to assess and grade the maturity of tomatoes. Two hundred and eighty one ‘Sun Bright’ tomatoes of different maturity stages were harvested from a Michigan State University’s research farm in Holt, MI in 2013. The light absorption and scattering properties of the fruit for the spectral range of 500-950 nm were measured, using an in-housed developed optical property measuring instrument. Significant changes in the absorption and scattering properties were observed as the tomato fruit were maturing from the ‘Green’ stage through the final ‘Red’ stage. These changes were directly related to the composition of, and physiological activities in, the tomato fruit. Mathematical models were developed, using the light absorption and scattering data, to classify the tomatoes into six and three maturity grades, respectively. Overall classification accuracies of up to 88.4% were obtained when the tomatoes were classified into six maturity grades. Higher accuracies of up to 92.3% were achieved for classification of tomatoes into three grades. This research demonstrated that light absorption and scattering properties can be effective for assessment and classification of tomato maturity.
Technical Abstract: Maturity is one of the most important factors in determining the processing and eating quality of tomato. The objective of this research was to test the suitability of optical absorption and scattering properties for evaluating the maturity of tomatoes. Optical absorption and reduced scattering coefficients over the spectral region of 500- 950 nm were measured, using a hyperspectral imaging-based spatially-resolved instrument, for 281 ‘Sun Bright’ tomatoes harvested at different stages of maturity. Absorption around 675 nm decreased successively with the increasing level of maturity, while the reduced scattering spectra monotonically decreased with the increasing wavelength. Partial least squares discriminant analysis (PLS-DA) models yielded 86.0% and 80.2% classification accuracies for six maturity grades, when using the full spectra (500-950 nm) of absorption and reduced scattering coefficients, respectively. PLS-DA models based on the combined absorption and scattering parameters and the effective attenuation coefficient improved prediction results by 0.35% and 7.61%, and 2.79% and 9.50%, respectively, compared with the single optical parameters. Moreover, better classification accuracies of 92.3% and 92.1% were obtained using the combined absorption and scattering parameters and the effective attenuation coefficient, respectively, when tomatoes were classified into three maturity grades. The research demonstrated that optical absorption and scattering spectra can provide an effective means for assessing and grading the maturity of tomatoes.