Nondestructive internal disorders detection of ‘Braeburn’ apple fruit by X-ray dark-field imaging and machine learning

• Published in: Postharvest biology and technology 2024-08, Vol.214, p.112981, Article 112981
• Main Authors: He, Jiaqi, Van Doorselaer, Leen, Tempelaere, Astrid, Vignero, Janne, Saeys, Wouter, Bosmans, Hilde, Verboven, Pieter, Nicolai, Bart
• Format: Article
• Language: English
• Subjects: Disorder; Inline sorting; Micro-CT; Microstructure; Porosity; X-ray scattering
• ISSN: 0925-5214; 1873-2356
• DOI: 10.1016/j.postharvbio.2024.112981

'Braeburn' apples are susceptible to internal browning disorders when stored under controlled atmosphere (CA) conditions with unfavorable gas compositions. The progression of CA-related disorders in apple tissues is dynamic, noting a decrease in porosity during early storage due to cellular breakdown and pore flooding, and an increase in porosity in later stages due to structural collapse and cavity formation. Utilizing grating-based X-ray dark-field radiography, which leverages X-ray small-angle scattering to detect microstructural changes below the pixel scale, this study assesses the technique's efficacy in identifying internal disorders in 'Braeburn' apples at both early and later stages. A machine learning approach was applied to compare the diagnostic capabilities of dark-field imaging with those of X-ray absorption radiography at identical image resolutions. Results indicate that for early-stage disordered fruit detection, X-ray dark field radiography is 10 % more accurate than absorption radiography, regardless of the machine learning classifiers that were applied. In the later stage of browning, dark-field imaging performs similarly to absorption imaging. High-resolution micro-computed tomography scans suggested that the distinct detection performance of dark-field imaging may be attributed to the more pronounced microstructural differences between healthy and early-stage defective tissues than those between healthy and later-stage defective tissues. The insights from this work will guide the application of X-ray dark-field systems in fruit quality assurance, particularly in detecting internal disorders. •X-ray dark-field radiography is more suited for detecting low-porosity defects.•X-ray absorption radiography is more effective for identifying high-porosity defects.•Changes in X-ray dark-field image are closely linked with microstructural changes.