Nondestructive Methods for the Quality Assessment of Fruits and Vegetables Considering Their Physical and Biological Variability

Fruits and vegetables are very important agricultural products in daily life. Evaluating the quality attributes of fresh fruits and vegetables by nondestructive sensing techniques has been an intensive research topic over the past two decades. The research progress on the detection of internal and external quality attributes of fresh fruits and vegetables using various nondestructive spectroscopic and imaging techniques, including visible/near-infrared spectroscopy, time-resolved and space-resolved spectroscopy, machine vision, hyperspectral and multispectral imaging, fluorescence techniques, X-ray imaging, computed tomography scanning, magnetic resonance imaging, and Raman techniques, is presented and discussed in this review. Each kind of fruit or vegetable shows great variability in physical characteristics (including size, shape, color, and temperature) and biological characteristics (including cultivar, season, maturity level, and geographical origin). This physical and biological variability complicates the quality evaluation of fresh fruits and vegetables. To eliminate the influence of variability and improve the inspection accuracy, a lot of attempts, including pre-processing, light intensity transformation, global model, band math, model transfer, etc., have been made in image correction and spectral compensation methods. This review provides a detailed summary of the various methods for solving the problem of physical and biological variability, as well as their advantages and disadvantages. Additionally, the current problems to be solved in spectroscopic and imaging technologies and the research trends of nondestructive measurement of the quality of fresh fruits and vegetables in the future are also revealed.