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Mechanical damage of fresh fruit occurs throughout the postharvest supply chain leading to poor consumer acceptance and marketability. In this review, the mechanisms of damage development are discussed first. Mathematical modeling provides advanced ways to describe and predict the deformation of fruit with arbitrary geometry, which is important to understand their mechanical responses to external forces. Also, the effects of damage at the cellular and molecular levels are discussed as this provides insight into fruit physiological responses to damage. Next, direct measurement methods for damage including manual evaluation, optical detection, magnetic resonance imaging, and X-ray computed tomography are examined, as well as indirect methods based on physiochemical indexes. Also, methods to measure fruit susceptibility to mechanical damage based on the bruise threshold and the amount of damage per unit of impact energy are reviewed. Further, commonly used external and interior packaging and their applications in reducing damage are summarized, and a recent biomimetic approach for designing novel lightweight packaging inspired by the fruit pericarp. Finally, future research directions are provided.HIGHLIGHTSMathematical modeling has been increasingly used to calculate damage to fruit.Cell and molecular mechanisms response to fruit damage is an under-explored area.Susceptibility measurement of different mechanical forces has received attention.Customized design of reusable and biodegradable packaging is a hot topic of research.

We review nondestructive techniques for measuring internal and external quality attributes of fruit and vegetables, such as color, size and shape, flavor, texture, and absence of defects. The different techniques are organized according to their physical measurement principle. We first describe each technique and then list some examples. As many of these techniques rely on mathematical models and particular data processing methods, we discuss these where needed. We pay particular attention to techniques that can be implemented online in grading lines.

• Reflectance, Transmittance, Fluorescence, Raman and integrated imaging is covered. • Instrumentation is discussed with special attention for real-time imaging. • The major steps in hyperspectral data analysis are discussed. • Overview of applications in external and internal quality evaluation. • Review of applications in food safety detection. In the past 20 years, hyperspectral imaging has been widely investigated as an emerging, promising technology for evaluating quality and safety of horticultural products. This technology has originated from remote sensing and joins the domains of machine vision and point spectroscopy to provide superior image segmentation for the detection of defects and contaminations, and to map the chemical composition. Thanks to the advancements in instrumentation and data analysis in the past two decades, hyperspectral imaging technology has evolved into a powerful nondestructive inspection tool and the scope of applications in postharvest quality and safety evaluation has expanded tremendously. In this article, different imaging modes (reflectance, transmittance, fluorescence and Raman) and their combinations, and the potential for real-time acquisition of hyperspectral images at industry relevant speeds are first discussed in terms of their advantages and disadvantages. Next reviewed are different data processing/analysis methods and associated steps from data pre-processing over the spectral and spatial domains to the actual model building and performance evaluation. An overview is then given of hyperspectral imaging applications for external quality and defect evaluation, internal quality and maturity assessment, and food safety detection of horticultural products. Finally, a brief discussion is presented on the challenges and opportunities in future development and application of hyperspectral imaging technology in food quality and safety evaluation of horticultural products. [ABSTRACT FROM AUTHOR]

• Bulk optical properties of tissue layers were measured for Satsuma mandarin. • The pigment related μ a and the μ s in juice vesicles increased along harvest time. • Color change was presented in the μ a of flavedo along harvest time. • Influence from fruit size was related to the development stage. • The difference in the μ s of flavedo among cultivars enhanced during maturation. As Satsuma mandarin is a multi-layered fruit, the optical properties of the different tissue layers influence the performance of spectroscopy-based quality detection models. Therefore, the variation in the bulk optical properties (BOP) of the inner (juice vesicles) and outer (flavedo) tissue layer of Satsuma mandarin was investigated for different harvest times, fruit sizes and cultivars. Satsuma mandarin fruit from three different cultivars (Iwasaki, Okitsu and Goku Wase) were harvested at three different times around the recommended harvest date and the BOP of the inner and outer tissue layers were estimated from double integrating spheres measurements. Along the harvest time, the absorption peak related to carotenoids in the bulk absorption coefficient (μ a) spectrum increased in both tissue layers, while the values attributed to chlorophylls decreased in the flavedo. Moreover, a slightly increasing trend over the harvest time was observed in the bulk scattering coefficient (μ s) spectra of juice vesicles, especially at the early stage. The μ a values of both tissue layers and the μ s values of juice vesicles deviated among different fruit sizes, which can be related to the development stage. Smaller fruit presented a higher carotenoids concentration in juice vesicles, an advanced color change in flavedo throughout the maturation stages and higher μ s values in juice vesicles at earlier maturation stages. The μ a differences in pigment absorption among different cultivars were related to the maturation order. Earlier maturing cultivars possessed higher μ a values related to carotenoids absorption in juice vesicles and advanced color changes in flavedo. The μ s values of the flavedo differed among the cultivars and these differences were enhanced during maturation. These insights in the sources of variation in the bulk optical properties of Satsuma mandarin tissues can be used for simulation-based optimal design of an optical measurement configuration and interpretation of the acquired signals in spectroscopy-based quality detection and monitoring. [ABSTRACT FROM AUTHOR]

• Provides an overview of the principles and theory of light transfer in biological materials. • Presents instrumentation and data analysis procedures for emerging optical techniques. • Reviews applications of optical properties for fruit and vegetable quality evaluation. • Discusses issues, challenges and future research needs. This paper provides an overview of the principles and theory of measuring optical properties of biological materials. It then presents the instrumentation and data analysis procedures for implementing several emerging optical techniques, including spatially resolved, time-resolved, and spatial-frequency domain, along with the standard integrating sphere method. Applications of these techniques for optical property measurement, maturity and quality assessment, and defect detection of fruits and vegetables are then reviewed, followed with discussions on issues and challenges that still need to be addressed for these emerging optical techniques. While these optical techniques are overall more sophisticated in instrumentation and computation, they are based on radiative transfer theory or simplified diffusion approximation theory. Hence, measurement of optical absorption and scattering properties has the potential of providing more useful information for quality evaluation of horticultural products. At present, these techniques are still slow in measurement, and prone to errors due to modeling and instrumentation deficiencies. Further research is therefore needed in using a better mathematical modeling approach, improving data acquisition accuracy and speed, and developing more robust inverse algorithms for optical property estimations. [ABSTRACT FROM AUTHOR]

Hypoxia-related disorders in apple and pears such as browning have been associated with insufficient transport of respiratory gasses inside the fruit during controlled atmosphere (CA) storage. Tissue porosity affects gas exchange and, hence, fruit respiration. It might, therefore, be interesting to adapt the storage conditions to the porosity of the fruit, especially in the case of low-porosity fruit like pears, which are highly susceptible to browning disorders. To improve the current CA storage strategies in that direction, fast, non-destructive measurement of fruit porosity is required. To this end, X-ray CT-based porosity maps and spatially resolved spectroscopy (SRS) were used to characterize respectively the porosity and optical properties of intact pear cultivars (Pyrus communis L.), including 'Thimo', 'Cepuna', and 'Conference'. Thereafter, the link between the fruit porosity and light-scattering properties was investigated. The porosity of the tissue region from the fruit surface down to 3 mm deep as well as the spatially averaged porosity of intact pears from 3 cultivars were found to be linearly correlated to the reduced scattering coefficient (µ s') at 760 nm and 835 nm calculated from SRS measurements. Both 'Cepuna' and 'Conference' pears showed similar porosities and scattering levels, which were slightly higher than those observed for 'Thimo' pears. The presented results suggest the possible application of laser scatter imaging at 760 nm and 835 nm for fast, contactless and non-destructive assessment of pear porosity. • X-ray CT-based porosity mapping of intact pear. • Characterization of BOP of intact pear using SRS. • Relationship between scattering and microstructural properties of pear. • Porosity of intact pear linearly correlated to the µ s ' at 760 nm (R2 =0.66). [ABSTRACT FROM AUTHOR]

A non-destructive methodology was developed to automatically detect and quantify bruise volumes in the equatorial region of apples, using X-ray CT images. Grey level threshold values were calculated to segment bruises in ‘Jonagold’, ‘Joly Red’ and ‘Kanzi’ apple fruit using the multi-level Otsu’s threshold method. Comparisons were made between the CT-based bruise volume estimates and bruise volume estimates that were based on destructive measurements in combination with simple geometric assumptions. Visualisation of the bruises in both 2 and 3D showed that bruises, resulting from a pendulum impact with a spherical impactor, can be highly irregularly shaped which implies that the bruise volume estimations based on simple geometric assumptions cannot deliver accurate results. [ABSTRACT FROM AUTHOR]

Abstract: The effect of cultivar, season, shelf-life and origin on the accuracy of near infrared (NIR) calibration models for the soluble solids content (SSC) and firmness of apple was studied based on a large spectral data set based on approximately 6000 apple fruit from different cultivars, origins, shelf-life exposure time and seasons. To interpret the variance in the spectra with respect to biological variability, functional analysis of variance (FANOVA) was used. From the FANOVA analysis it was concluded that the effects of cultivar, origin and shelf-life exposure time on the NIR spectra were all significant. The largest differences in the spectra were found around the water absorption peaks (970, 1170 and 1450nm). External validations using independent data sets showed that the accuracy of the models increased considerably when more variability was included in the calibration data set. In general the RMSEP for predictions of the SSC were in the range 0.6–0.8°Brix, while for Magness Taylor firmness it was 5.9–8.8N, depending on the cultivar. It was shown that atypical data can lead to large validation errors. It is, therefore, important to collect a calibration data set which is sufficiently representative for future samples to be analyzed with the developed calibration models and to develop simple procedures for model adaptation during practical use. [Copyright &y& Elsevier]

Abstract: The potential of near infrared (NIR) reflectance spectroscopy over the range 780–1690nm was investigated to measure the soluble solids content (SSC) and firmness of bell pepper fruit. Partial least squares (PLS) calibration models were constructed based on a calibration dataset which included data from two cultivars (Solution and Ferrari) and two harvest times (2005 and 2006). The effect of Savitzky–Golay second derivative preprocessing and extended multiplicative signal correction (EMSC) on the accuracy of the calibration models was investigated and the best results were obtained with the former. The SECV were equal to 5.9N and 0.59°Brix for firmness and SSC, respectively. When the model was applied to an external data set including data from cv. Solution and a different harvest season, the satisfactory SEP values of 4.49N and 0.7°Brix were obtained, but for firmness a bias of 5.6N was observed. From these results it can be concluded that NIR spectroscopy can be used as a non-destructive technique for measuring the SSC in bell pepper, but that further research is needed to make it robust for firmness prediction. [Copyright &y& Elsevier]

Abstract: An overview is given of near infrared (NIR) spectroscopy for use in measuring quality attributes of horticultural produce. Different spectrophotometer designs and measurement principles are compared, and novel techniques, such as time and spatially resolved spectroscopy for the estimation of light absorption and scattering properties of vegetable tissue, as well as NIR multi- and hyperspectral imaging techniques are reviewed. Special attention is paid to recent developments in portable systems. Chemometrics is an essential part of NIR spectroscopy, and the available preprocessing and regression techniques, including nonlinear ones, such as kernel-based methods, are discussed. Robustness issues due to orchard and species effects and fluctuating temperatures are addressed. The problem of calibration transfer from one spectrophotometer to another is introduced, as well as techniques for calibration transfer. Most applications of NIR spectroscopy have focussed on the nondestructive measurement of soluble solids content of fruit where typically a root mean square error of prediction of 1° Brix can be achieved, but also other applications involving texture, dry matter, acidity or disorders of fruit and vegetables have been reported. Areas where more research is required are identified. [Copyright &y& Elsevier]

• GASMAS for pome fruit respiration measurement. • Fruit mimicking model system for GASMAS oxygen sensor validation. • Influence of skin and additional surface coating on gas exchange rate. Pome fruit stored under a controlled atmosphere (CA) often suffers hypoxia due to the mismatch of O 2 level in the storage rooms and the fruit's O 2 consumption. Fruit response-based O 2 sensing and control could be an efficient approach to reduce the hypoxia-related physiological disorders and therefore increase the shelf life of stored fruit. This research aims to validate and evaluate the application of nondestructive gas in scattering media absorption spectroscopy (GASMAS) O 2 sensing in fruit post-harvest. In the first stage, the GASMAS O 2 sensor was validated on a fruit mimicking multilayer model system where a high correlation was observed between the measured and reference O 2 partial pressures (r2 ≥ 0.9). Later, the GASMAS sensor was evaluated on two apple cultivars (Malus x domestica 'Golden delicious', Malus x domestica 'Nicoter') and one pear cultivar (Pyrus communis 'Conference'). The observed GASMAS signal from the 'Golden delicious' apples were nearly 2 times higher than the signal from 'Nicoter' apples and 5 times higher than from the 'Conference' pears. In the next stage, GASMAS measurements were taken on water submerged 'Golden delicious' apple and 'Conference' pear to investigate the difference in O 2 consumption in those fruit. The calculated relative O 2 changes during respiration and evolution of the O 2 partial pressure after nitrogen treatment for both the fruit were found different. It was hypothesized that these findings may be attributed to variations in fruit porosity. And finally, the influence of skin and additional surface coating on the gas exchange was studied by immersing unpeeled, peeled and coated samples in the gaseous nitrogen for 2 h before measurement. The coating was found to reduce the gas exchange compared to the unpeeled samples which already exhibited a lower exchange rate than the peeled samples. [ABSTRACT FROM AUTHOR]