TECHNOLOGIES FOR QUALITY MEASUREMENT AND GRADING OF FRUITS AND VEGETABLES
Location: Sugarbeet and Bean Research
Title: Peach maturity/quality assessment using hyperspectral imaging-based spatially-resolved technique
Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2011
Publication Date: June 25, 2011
Citation: Cen, H., Lu, R., Mendoza, F., Ariana, D. 2011. Peach maturity/quality assessment using hyperspectral imaging-based spatially-resolved technique. Proceedings of SPIE. April 25-29, 2011. Orlando, Florida. Paper No. 8027-0L, 15 p.
Interpretive Summary: Maturity is an important indicator for determining harvest time and postharvest handling and marketing procedures for horticultural products. Peach maturity is commonly assessed using multiple destructive techniques, including Magness-Taylor penetrometry for firmness, refractometry for soluble solids content, and colorimetry for the color of fruit skin and flesh. This research was aimed at nondestructively assessing multiple maturity parameters of peaches using a newly in-house developed optical property measuring instrument. Five hundred ‘Redstar’ peaches were harvested in 2010 and their optical absorption and scattering properties for the wavelengths of 515-1,000 nm were measured using the optical property measuring instrument. The firmness, soluble solids content, and fruit skin and flesh color of the peaches were measured using standard destructive methods. In addition, the firmness of the peaches was also measured nondestructively using a commercial acoustic and impact firmness sensor. Mathematical models were developed to predict the maturity parameters of peaches using the optical property data. The absorption and scattering properties of peaches changed, in different patterns, with the ripening and development of pigments in the fruit. The measured optical properties were able to predict the firmness, soluble solids content, and skin and flesh color of peaches with values of the correlation coefficient being 0.749, 0.504, 0.898 and 0.741, respectively. The optical firmness prediction compared favorably to acoustic and impact firmness measurement. This research demonstrated that the optical property measuring technique is useful for assessing the maturity or quality of peaches and can also be suitable for other horticultural and food products.
The objective of this research was to measure the absorption and reduced scattering coefficients of peaches, using a hyperspectral imaging-based spatially-resolved method, for their maturity/quality assessment. A newly developed optical property measuring instrument was used for acquiring hyperspectral reflectance images of 500 ‘Redstar’ peaches. Absorption and reduced scattering coefficient spectra for 515-1,000 nm were extracted from the spatially-resolved reflectance profiles using a diffusion model coupled with an inverse algorithm. The absorption spectra of peach fruit were featured by several absorption peaks around 525 nm for anthocyanin, 620 nm for chlorophyll-b, 675 nm for chlorophyll-a, and 970 nm for water, while µs' decreased consistently with the increase of wavelength for most of the tested samples. Both µa and µs' were correlated with peach firmness, soluble solids content (SSC), and skin and flesh color parameters. Better prediction results for partial least squares models were obtained using the combined values of absorption and scattering spectra than using them separately. The results were further improved using least squares support vector machine models with values of the best correlation coefficient for firmness, SSC, skin lightness and flesh lightness being 0.749 (standard error of prediction or SEP = 17.39 N), 0.504 (SEP = 0.92 Brix), 0.898 (SEP = 3.45), and 0.741 (SEP = 3.27), respectively. These results compared favorably to acoustic and impact firmness measurements with the correlation coefficient of 0.639 and 0.631, respectively. Hyperspectral imaging-based spatially-resolved technique is useful for measuring the optical properties of peach fruit, and it also has good potential for assessing fruit maturity/quality attributes.