Abstract
Reliable information about degree of red coloration in fruit flesh is essential for grading and sorting of red-fleshed apples. We propose a spatially resolved interactance spectroscopy approach as a new rapid and non-destructive technique to estimate degree of red coloration in the flesh of a red-fleshed apple cultivar ‘Kurenainoyume’. A novel measurement system was developed to obtain spatially resolved interactance spectra (190–1070 nm) for apple fruits at eight different light source-detector separation (SDS) distances on fruit surface. Anthocyanins in apple were extracted using a solvent extraction technique, and their contents were quantified with a spectrophotometer. Partial least squares (PLS) regression analyses were performed to develop estimation models for anthocyanin content from spatially resolved interactance spectra. Results showed that the PLS models based on interactance spectra obtained at different SDS distances achieved different predictive accuracy. Further, the system demonstrated the possibility to detect the degree of red coloration in the flesh at specific depths by identifying an optimal SDS distance. This might contribute to provide a detailed profile of the red coloration (anthocyanins) that is unevenly distributed among different depths of the flesh. This new approach may be potentially applied to grading and sorting systems for red-fleshed apples in fruit industry.
Highlights
Reliable information about degree of red coloration in fruit flesh is essential for grading and sorting of red-fleshed apples
The degree of red coloration in the skin and flesh showed a large variation among different fruit samples (Fig. 2)
This study demonstrated the possibility of estimating the anthocyanin content in apple flesh from the interactance data obtained with our novel spatially resolved interactance spectroscopy system
Summary
Reliable information about degree of red coloration in fruit flesh is essential for grading and sorting of red-fleshed apples. We propose a spatially resolved interactance spectroscopy approach as a new rapid and non-destructive technique to estimate degree of red coloration in the flesh of a red-fleshed apple cultivar ‘Kurenainoyume’. Most of the equipment used in practice as well as the prototypes developed in recent studies focused on the assessment of s weetness11,12, ripeness[13,14], the detection of b ruise[15,16] and hollow heart or c avity[17,18] in the inner parts (internal quality), and the appearance color of fruit skin (external quality)[19,20], which are the commonly used parameters for fruit sorting and grading These techniques sort and grade the fruits based on the estimated values of the property parameters, which are selected as criteria for fruit sorting and grading. The interactance spectroscopic approach has been used to replace the reflectance and transmittance approaches to determine the contents of particular compounds in various samples[25,26,27]
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