Optical Methods for Firmness Assessment of Fresh Produce: A Review

Abstract

This chapter is devoted to a review of optical techniques to measure the irmness of fresh produce. Emphasis is placed on the techniques that have a potential for online high-speed grading. Near-infrared spectroscopy (NIRS) and spatially resolved relectance spectroscopy (SRRS) are discussed in detail because of their advantages for online applications. For both techniques, this chapter reviews the fundamental principles as well as the measured performances for measuring the irmness of fresh produce, particularly fruit. For both techniques, there have been studies that show correlations with penetrometer irmness as high as r = 0.8 − 0.9. However, most studies appear to involve bespoke laboratory instruments measuring single produce types under static conditions. Therefore, accurate performance comparison of the two techniques is very diicult. We suggest more studies are now required on a wider variety of produce and particularly comparative studies between the NIRS and SRRS systems on the same samples. Further instrument developments are also likely to be required for the SRRS systems, especially with an online measurement where fruit speed and orientation are likely to be issues, before the technique can be considered advantageous compared to the commonly used NIRS systems.

Sweet Cherry Fruit Firmness Evaluation Using Compression Distance Methods

“…In addition, a high positive correlation of the sweet cherry firmness between the trained panelists with the Firmtech2 device, which by applying 1 mm compression determines the maximum force required to achieve deformation, has been demonstrated [7,8]. Novel technologies for non-destructive measuring of sweet cherries' firmness using color sensors and near-infrared diffuse reflectance spectroscopy have been developed [27,28], but with controversial effectiveness on the prediction of firmness [29]. While the mechanical characteristics of several fruits have been examined [30], there is limited knowledge about the interaction between these traits and the physiological responses of the fruits.…”

Investigation of light propagation in pork tissue applied in multispectral imaging technique by Monte Carlo simulation method

“…The demand for food quality assessment has been increasing in recent years, resulted in the development of food quality assessment techniques, especially non-invasive assessment methods because of the advantages such as fast, wide applicability... [1]. Thereby, optical-based methods offer a great deal of potential for evaluation, which includes two main techniques of "point" measurement and multispectral or hyperspectral methods to be applied over wide parts of the food surface based on Engineering EPiC Series in Engineering the VIS-NIR wavelength range [2]. In this research, the multispectral imaging method is mainly focused.…”