An overview on optical non-destructive detection of bruises in fruit: Technology, method, application, challenge and trend

Abstract

BackgroundBruising is a kind of subcutaneous tissue injury that does not involve the rupture of fresh fruit epidermis. This damage can occur at any stage from picking, storage and transportation, which can result in fruit deterioration and rejection by the market or consumer. It is, however, very challenging to detect bruising due to no or few visual symptoms. A lot of studies have carried out to establish a feasible methodology to achieve rapid, non-destructive and accurate detection of bruised fruit in the commercial real-time grading line.Scope and approach.This review focuses solely on the non-destructive detection for fruit bruising, involving qualitative and quantitative analysis (e.g., degree, time and volume of bruises), and provides a comprehensive summary of the latest advances in 11 optical non-destructive sensing techniques, covering basic principles, system composition, methods/algorithms, applications, challenges and trends.Key findings and conclusions.Optical sensing technologies, especially imaging, are suitable for bruising detection of fruit. HSI can evaluate the bruises with different of degrees and time periods. Both MRI and X-ray CT imaging can reconstruct 3D fruit for the quantitative analysis of bruise volume and the research of bruise mechanism. SIRI shows impressive depth discrimination and enhanced imaging ability for subcutaneous slight bruises. The fusion technology is valuable, but it needs further exploration. The advanced detection algorithms are crucial to the successfully implementation of technology. In practice, MSI, FI, TI, BSI, SIRI and fusion technologies are worth recommending for online bruise detection. In addition, the study about the mechanism of bruising formation and the postharvest behavior of fruit can help to reduce the bruising incidence of fresh fruit after harvest.