Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 4/28/2009
Publication Date: 6/21/2009
Citation: Lu, R., Cen, H., Huang, M., Ariana, D.P. 2009. Optical Properties of Bruised Apple Tissue. ASABE Annual International Meeting. Paper No. 096998. Interpretive Summary: Apple bruising frequently occurs during harvest, postharvest handling, transport and retailing, and it is of great concern because bruised apples can be downgraded or even rejected by consumers, which would result in economic loss to growers, packers, shippers or retailers. Hence preventing or minimizing bruise occurrence at various harvest and postharvest operations is utmost important. Moreover, it is also critical to have an effective inspection system to segregate those apples with pre-existing quality-degrading bruises from premium quality ones during sorting and grading. Research was conducted on using a hyperspectral imaging-based spatially resolved technique, a new technique recently developed in our lab, to determine the optical absorption and scattering properties of bruised tissues in 'Golden Delicious' and 'Red Delicious' apples and quantify their changes over a period of three weeks. Results showed that absorption for normal, unbruised tissues was generally lower than that for bruised tissues in the visible region of 500-700 nm, while an opposite trend was observed for the spectral region of 700-1000 nm. In contrast, scattering properties for normal, unbruised tissues were significantly higher in value than those for bruised tissues for the wavelengths of 500-1000 nm; scattering in the bruised tissues decreased consistently over time. Bruising had more impact on scattering than on absorption. This finding suggests that an optical inspection system that can enhance scattering features would improve the detection of bruises on apples. This research provided new knowledge of optical properties for normal and bruised apples, which has not been available previously. This knowledge would be valuable to researchers and engineers in development of methods/techniques to reduce and detect apple bruises.
Technical Abstract: Understanding the optical properties of apple tissue, especially bruised tissue, can help us prevent or mitigate bruise occurrence during harvest and postharvest operations, and develop an effective method for detecting bruises during sorting and grading. This research was aimed at determining the optical properties of bruised apple tissue over 500-1000 nm and quantifying their changes over time. Spectral absorption and reduced scattering coefficients were determined from normal, unbruised tissues for ‘Golden Delicious’ and ‘Red Delicious’ apples and then from the bruised tissues at different time intervals after bruising, using a hyperspectral imaging-based spatially resolved technique. Absorption for normal, unbruised tissues was generally lower than that for the bruised tissues in the visible region of 500-700 nm, while an opposite trend was observed for the spectral region of 700-1000 nm. In contrast, the reduced scattering coefficient for normal, unbruised tissues was significantly higher than that for bruised tissues for the wavelengths of 500-1000nm; its value decreased consistently over time. Bruising had more significant impact on scattering than on absorption. Hence an optical system that can enhance scattering features would be better suited for bruise detection.