Studies on banana fruit quality and maturity stages using hyperspectral imaging

Banana fruit quality and maturity stages were studied at three different temperatures, viz., 20, 25, and 30 °C by using hyperspectral imaging technique in the visible and near infrared (400-1000 nm) regions. The quality parameters like moisture content, firmness and total soluble solids were determined and correlated with the spectral data. The spectral data were analyzed using the partial least square analysis. The optimal wavelengths were selected using predicted residual error sum of squares. The principal component analysis was also used to test the variability of the observed data. By using multiple linear regressions (MLR), models were established based on the optimal wave lengths to predict the quality attributes. The coefficient of determination was found to be 0.85, 0.87, and 0.91 for total soluble solids, moisture and firmness of the banana fruits, respectively. The change in TSS and firmness of banana fruits stored at different temperatures, viz., 20, 25, and 30 °C during the ripening process followed the polynomial relationships and the change in moisture content followed a linear relationship at different maturity stages.     

Real-time multispectral imaging system for online poultry fecal inspection using unified modeling language

A prototype real-time multispectral imaging system for fecal and ingesta contaminant detection on broiler carcasses has been developed. The prototype system includes a common aperture camera with three optical trim filters (517, 565 and 802-nm wavelength), which were selected by visible/NIR spectroscopy and validated by a hyperspectral imaging system with decision tree algorithm. The on-line testing results showed that the multispectral imaging technique can be used effectively for detecting feces (from duodenum, ceca, and colon) and ingesta on the surface of poultry carcasses with a processing speed of 140 birds per minute. This paper demonstrated both multispectral imaging hardware and real-time image processing software. For the software development, the Unified Modeling Language (UML) design approach was used for on-line application. The UML models included class, object, activity, sequence, and collaboration diagram. User interface model included 17 inputs and 6 outputs. A window-based real-time image processing software composed of 11 components, which represented class, architecture, and activity. Both hardware and software for a real-time fecal detection were tested at the pilot-scale poultry processing plant. The run-time of the software including online calibration was fast enough to inspect carcasses on-line with an industry requirement. Based on the preliminary test at the pilot-scale processing line, the system was able to acquire poultry images in real-time. According to the test results, the imaging system is reliable for the harsh environments and UML-based image processing software is flexible and easy to be updated when additional parameters are needed for in-plant trials. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Comparison of multispectral indexes extracted from hyperspectral images for the assessment of fruit ripening

The present research is focused on the application of artificial vision to assess the ripening of red skinned soft-flesh peach (‘Richlady’). Artificial vision allows a spatially detailed determination of the ripening stage of the fruit. The considered optical indexes (Ind₁ and Ind₂, proposed in the present research, and Ind₃ and I_AD, proposed by other authors) are based on the combination of wavelengths close to the chlorophyll absorption peak at 680 nm. Ind₁ corresponds approximately to the depth of the absorption peak, and Ind₂ corresponds to the relative absorption peak. An artificial image of each index was obtained by computing the corresponding reflectance images, which were acquired with a hyperspectral camera. All indexes were able to correct convexity (except for the just-harvested peaches and for Ind₁). Ind₂ is the preferred index; it showed the highest discriminating power between ripening stages and no influence of convexity. Ind₂ also allowed the differentiation of ripening regions within the fruits, and it showed the evolution of those regions during ripening.     

Hyperspectral and multispectral imaging for evaluating food safety and quality

Spectral imaging technologies have been developed rapidly during the past decade. This paper presents hyperspectral and multispectral imaging technologies in the area of food safety and quality evaluation, with an introduction, demonstration, and summarization of current spectral imaging techniques available to the food industry for practical commercial use. The main topics include methods for acquiring spectral images, components for building spectral imaging systems, methods for calibrating spectral imaging systems, and techniques for analyzing spectral images. The applications for evaluating food and agricultural products are presented to reflect common practices of the spectral imaging techniques. Future development of hyperspectral and multispectral imaging is also discussed.     

Effects of pomegranate sauce on quality of marinated anchovy during refrigerated storage

Effects of pomegranate sauce on the quality of marinated anchovy during storage at 4 °C were investigated. Anchovy were marinated with 30 g/L acetic acid and 150 g/L salt, put into glass jars, filled with either sunflower oil or pomegranate sauce and stored at 4 °C. Total volatile basic nitrogen (TVB-N) and trimethylamine (TMA-N) values increased during the storage. Higher values for free fatty acid (FFA), conjugated diens (k-dien) and para-anisidine (p-Av) were found in samples with sunflower oil than those with pomegranate sauce. Samples in pomegranate sauce showed better oxidative stability. Higher taste and flavour and lower appearance scores were found for samples in pomegranate sauce than those samples in sunflower oil. It was found that pomegranate sauce was as least effective as the traditional sunflower oil to keep quality. Pomegranate sauce also produced desirable taste and flavour but the coloration should be studied in further studies.     

A multispectral imaging technique to determine concentration profiles of myoglobin derivatives during meat oxygenation

We have designed a multispectral imaging acquisition system to measure the relative concentration values of myoglobin forms inside meat during oxygenation. Images at 474, 525, 572 and 610 nm are used to compute the concentration of reduced myoglobin, oxymyoglobin and metmyoglobin with a spatial resolution of 0.0125 mm/pixel. From these images, pigment concentration profiles as a function of oxygenation time and depth beneath the surface were obtained. A model describing the diffusion of oxygen and the consumption of reduced myoglobin is numerically tested versus the measured concentration profiles. The model accurately fits the data with a Mean Root Squared Error equal to 0.253%. Precise definitions for position and width of pigment layers based in concentration profiles are given. The results suggest that multispectral imaging techniques combined with precise control and measurement of sample temperature and oxygen partial pressure will permit detailed studies of the myoglobin chemistry during oxygenation.     

Improving the keeping quality of pomegranate fruit by intermittent warming

 Mollar pomegranates (Punica granatum, Punicaceae) were stored at 0  °C or 5  °C and 95% relative humidity (RH) for 80 days. Intermittent warming (IW) cycles of 1 day at 20  °C every 6 days, during which time the fruit had been stored at 0  °C or 5  °C, followed by a shelf-life period of 7 days at 15  °C and 70% RH were applied. IW during storage at 0  °C was the best treatment for maintaining the red skin colour as at harvest. However the red colour of the arils (hue angle) was kept better under warming at 5  °C. Although significant changes in the individual anthocyanins were observed in all treatments, particularly after the shelf-life period, the total anthocyanin content of the juice at harvest was maintained. While storage at 0  °C avoided decay although increased the risk of chilling injuries such us pitting and husk scald, 5  °C-storage reduced these injuries but fungal attacks were not inhibited. After the shelf-life period, IW alleviated chilling injuries without any incidence of decay. Warming treatments gave very good results with respect to storage and the keeping quality of pomegranates, particularly when applied during storage at 0  °C. Received: 10 February 1998 / Revised version: 24 April 1998     

Development of a two-band spectral imaging system for real-time citrus canker detection

Inspection of citrus canker is crucial due to its fast spread, high damage potential, and massive impact on export and domestic trade. This research was aimed to develop a prototype for real-time citrus canker detection. An inspection module was developed on a one-line commercial fruit sorting machine. Twenty tungsten halogen spotlights coupled with an aluminum dome painted with white diffuse paint provided reflectance illumination to the fruits in the detection chamber. The camera unit was a two-band spectral imaging system, which mainly consisted of a beamsplitter, two bandpass filters with central wavelengths at 730 and 830 nm, and two identical monochrome cameras. Using an exposure time of 10 ms, the imaging system can capture narrowband images without blurring from samples moving at a speed of 5 fruits/s. Spatial resolution of the acquired images was 2.3 pixels/mm. Real-time image processing and classification algorithms were developed based on a two-band ratio approach (i.e., R830/R730). The system was tested using 360 grapefruits with normal surface, canker lesions, and other peel diseases and defects. The overall classification accuracy was 95.3%, demonstrating that the methodology as well as the hardware and the software are effective and suitable for real-time citrus canker detection. Greasy spot, melanose, and sooty mold could generate false positive errors for the fruits without canker. The current system setup was limited to a single perspective view of the fruits. Future work will be conducted with an emphasis on whole surface inspection of each fruit.     

Non-destructive evaluation of maturity and quality parameters of pomegranate fruit by visible/near infrared spectroscopy

In this study, the potential of visible and near infrared spectroscopy was investigated to classify the maturity stage and to predict the quality attributes of pomegranate variety “Ashraf” such as total soluble solids content, pH, and titratable acidity during four distinct maturity stages between 88 and 143 days after full bloom. Principal component analysis was used to distinguish among different maturities. The prediction models of internal quality attributes of the pomegranate were developed by partial least squares regression. The transmission spectra of pomegranate were obtained in the wavelength range from 400 to 1100 nm. In this research several preprocessing methods were utilized including centering, smoothing (Savitzky–Golay algorithm, median filter), normalization (multiplicative scatter correction and standard normal variate) and differentiation (first derivative and second derivative). It concluded that different preprocessing techniques had effects on the classification performance of the model using the principal component analysis method. In general, standard normal variate and multiplicative scatter correction gave better results than the other pretreatments. The correlation coefficients (r), root mean square error of calibration and ratio performance deviation for the calibration models were calculated: r = 0.93, root mean square error of calibration = 0.22 °Brix and ratio performance deviation = 6.4 °Brix for total soluble solids; r = 0.84, root mean square error of calibration = 0.064 and ratio performance deviation = 4.95 for pH; r = 0.94, root mean square error of calibration = 0.25 and ratio performance deviation = 5.35 for titratable acidity.     

1-甲基环丙烯结合茉莉酸甲酯雾化熏蒸对石榴采后品质的影响

目的 探究1-甲基环丙烯(1-methylcycloproene,1-MCP)和茉莉酸甲酯(methyl jasmonate,MeJA)联合处理对石榴贮藏过程生理代谢和病害的协同调控作用。方法 以和田石榴为对象,采用1-MCP结合MeJA雾化熏蒸处理,研究其对冷藏条件下果实品质的影响。结果 1-MCP结合MeJA雾化熏蒸处理有效延缓了石榴果实在冷藏过程中的果皮褐变,较好保持了果实色泽,降低了果实腐烂率,保持了果实可溶性固形物、可滴定酸和总酚含量,抑制多酚氧化酶活性,减缓过氧化物酶、过氧化氢酶和超氧化物歧化酶活性的下降,同时保持较低的丙二醛含量和细胞膜透性。此外,结合处理还能维持较高的果实可溶性蛋白含量并保持良好的果皮微观结构。结论 1-MCP结合100μmol/L MeJA雾化熏蒸处理的石榴贮藏品质最佳,为石榴采后商品化处理提供了依据。     

Design and calibration of a dual-band imaging system

A prototype portable multispectral imaging system, in terms of design, fabrication, compactness, and cost effectiveness was developed for real-time contaminant detection in poultry processing plants. The prototype system developed in this research was a dual-band spectral imaging system that acquired two different spectral images simultaneously. This was accomplished by using a two-port imaging system that consisted of two identical monochrome cameras, optical components, and two interchangeable optical filters. Spectral reflectance from an object was collimated by lenses and split identically in two directions by a beamsplitter. Focusing lenses behind a beamsplitter projected each image on its respective sensor. Two optical bandpass filters determined the spectral characteristics of each image and are easily interchangeable. In order to co-register two-band images, a system-specific calibration algorithm was developed that corrected lens distortions and lens-sensor geometric misalignments. The prototype imaging system and the system calibration algorithm were tested for image registration accuracy. The imaging system acquired two-band images of 3D object with less than 8.1 μm error in terms of the position of the sensor. The prototype system was able to effectively detect feces (duodenum, cecum, colon) and ingesta on the surface of poultry carcasses. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Challenges and solutions of optical-based nondestructive quality inspection for robotic fruit and vegetable grading systems: A technical review

BackgroundOptical techniques, including computer vision, spectral imaging, near-infrared technology and other emerging imaging and spectroscopy techniques, have been rapidly developing and widely applied in fruit and vegetable grading systems for nondestructive quality inspecting and grading over the past decades. However, automatic detection of quality and grading is still difficult due to some still existing challenges, which are the key of blocking their commercialization in robotic fruit and vegetable grading systems. The challenges include the following aspects: the influence of physical and biological variability, whole surface detection, discrimination between defects and stems/calyxes, unobvious defect detection, robustness of the features and algorithms, as well as rapid optical detection system development. These challenges can reduce the fruit or vegetable quality inspection accuracy, thus greatly reducing automatic level of the quality inspecting and grading machines.Scope and approachAs agricultural engineers with about eight years of technical experience in fruit grading systems, we believe the ultimate goal of each scientific research should seek its task in serving the engineering. So, we have made many attempts to solve the challenges and increase the automation of the grading machines.Key findings and conclusionsThe review gives a detailed summary about the challenges and solutions of optical-based nondestructive quality inspection for fruit or vegetable grading systems from the perspective of engineering. Particular attention has been paid to the techniques that can improve the automation degree of the grading robot in this review. The advantages and disadvantages of the solutions are compared and discussed. Additionally, the remaining engineering challenges and future trends are also discussed.     

Potential use of physical measurements including ultrasound for a better mango fruit quality characterization

The potential use of ultrasound measurements, combined with other physical measurements, has been investigated. The good relationship between soluble solids content (SSC) and ultrasonic wave velocity reported in the literature being confirmed by our study, our main goal was to evaluate the added value of ultrasound measurements around 25 MHz for the determination of biochemical compounds responsible of organoleptic quality of mangoes. Among the main sugar constituents of mango juice, only sucrose content prediction was improved by combining SSC and ultrasonic waves velocity using a PLS model (R² = 0.81, RMSECV = 12.3, bias = 0.10, RPD = 2.3) when compared to the linear model with SSC only (R² = 0.75, SEP = 14.05, bias = 0.08). The same conclusion was obtained for titratable acidity PLS model using whole fruit hardness, SSC and ultrasonic wave velocity (R² = 0.82, RMSECV = 1.84, bias = 0.02, RPD = 2.4) compared to the linear model with fruit hardness only (R² = 0.78, SEP = 2.07, bias = 0.02). However, the added value of ultrasound measurements was not always found to be significant (P = 0.05) when a Wilcoxon statistical tests was conducted on the residuals of the linear and PLS models for both sucrose and titratable acidity.     

Machine vision system for online inspection of freshly slaughtered chickens

A machine vision system was developed and evaluated for the automation of online inspection to differentiate freshly slaughtered wholesome chickens from systemically diseased chickens. The system consisted of an electron-multiplying charge-coupled-device (EMCCD) camera used with an imaging spectrograph and controlled by a computer to obtain line-scan images quickly on a chicken processing line of a commercial poultry plant. The system scanned chicken carcasses on an eviscerating line operating at a speed of 140 chickens per minute. An algorithm was implemented in the system to automatically recognize individual carcasses entering and exiting the field of view, to locate the region of interest (ROI) of each chicken, to extract useful spectra from the ROI as inputs to the differentiation method, and to determine the condition for each carcass as being wholesome or systemically diseased. The system can acquire either hyperspectral or multispectral images without any cross-system calibration. The essential spectral features were selected from hyperspectral images of chicken samples. The differentiation of chickens on the processing line was then carried out using multispectral imaging. The high accuracy obtained from the evaluation results showed that the machine vision system can be applied successfully to automatic online inspection for chicken processing. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply endorsement or recommendation by the USDA.     

Non-destructive assessment of apricot fruit quality by portable visible-near infrared spectroscopy

The ability of portable Near Infrared Spectroscopy to determine apricot fruit quality has been studied. Calibration models allowing the determination of soluble solids content (SSC), total acidity (TA) and firmness (Fi) of apricots were carried out with variable precisions. Models were built for each variety and global models combining different varieties were attempted. SSC was determined with a root mean square error of cross-validation (RMSECV) comprised between 0.67 and 1.1 °Brix and R-values between 0.88 and 0.96. Concerning Fi, the accuracy of the prediction was variety dependant. These predictions were correct for the varieties Kioto and Harostar with RMSECV-values between 6.2% and 13% (R-values between 0.85 and 0.92) and unsatisfactory for Bergarouge (RMSECV = 24%). TA was predicted with RMSECV-values between 0.79 and 2.61 g 100 ml⁻¹ and R-values between 0.73 and 0.97. In a second application, near infrared spectra were used to classify apricot fruits according to their variety and colour intensity with correct efficiency. The results obtained in the present study showed that NIRS technology could be applicable to apricot quality and that such portable devices could help to obtain a complete follow-up of the fruits in orchards and during post-harvest.     

Hyperspectral imaging to classify and monitor quality of agricultural materials

Hyperspectral imaging has been acknowledged as an emerging technology for monitoring quality parameters and improving grading of agricultural materials, such as field crops (e.g., cereals, pulses, oil seeds) and horticultural crops (e.g., apples, strawberries). It has become a popular research tool that facilitates thorough non-destructive analyses by simultaneous acquisition of both spectral and spatial information of agricultural samples. The technique is an extension of multispectral imaging, which provides a large data set by applying conventional imaging, radiometry, and spectroscopic principles when acquiring images. Hyperspectral imaging was initially used for remote sensing applications, but now has been developed to facilitate complete and reliable analyses of intrinsic properties and external characteristics of samples. This paper reviews applications of using hyperspectral imaging for routine grain industry operations such as grading, classification, and chemometric analyses of major constituents of agricultural materials.     

Multispectral line-scan imaging system for simultaneous fluorescence and reflectance measurements of apples: multitask apple inspection system

In this methodology paper, a recently developed line-scan imaging system, capable of simultaneously acquiring a combination of multispectral reflectance and fluorescence from rapidly moving objects, is presented. The system can potentially provide multitask inspections for quality and safety attributes of apples due to its dynamic selectivity in multispectral bands, each with independent spectral bandwidth in the fluorescence and reflectance domains. Mounted on a commercial apple-sorting machine, the system was evaluated to determine the image pixel (spatial) resolution for apples at a sorting line speed of three to four apples per second. Apples loaded on the sorting machine were spaced approximately 15 cm apart. With these parameters, the resulting images showed approximately 40 line-scan images per apple, for a horizontal spatial resolution of 2 mm per pixel. In the vertical direction, with 1,002 pixels available for each line-scan image, the spatial resolution of the system can be as high as approximately 0.2 mm per pixel depending on the choice of binning. The combined spatial resolution is comparable to that in our previous studies and is adequate for image-based online inspection of defects and fecal contamination on apples. Company and product names are used for clarity and do not imply any endorsement by USDA to the exclusion of other comparable products.     

Optimisation of a process for production of pomegranate pulp and flaxseed powder fortified probiotic Greek dahi

Fortified probiotic Greek dahi was formulated with pomegranate pulp (PP) and flaxseed powder (FP). The product variables, viz. PP, FP and incubation time, were optimised based on chemical, sensory and textural attributes. The study revealed that PP significantly affected the acidity and antioxidant content, while FP influenced the sensory and textural properties of the product. The optimum conditions were 15% PP, 2% FP and 12‐h incubation time. The developed fortified probiotic Greek dahi is a potential synbiotic food.     

Development of a total quality scoring system based on consumer preference weightings and sensory profiles: application to fruit dates (Tamr)

A scoring system for evaluating the total quality of a food product (Tamr) based on consumer preferences was developed and tested for validity. The development process started with a survey among adult date consumers in the United Arab Emirates to identify their perception of characterizing total quality of date fruit among specified attributes. The consumer subjective ranking of eleven specified attributes was used to derive a quantitative weighted factor for each attribute. Based on the weighted factor a quantitative scoring guide was developed. A panel evaluation of five date varieties (Khlas, Barhee, Boumaan, Fard and Ruzeiz) was conducted as an application of the developed scoring system. Panel evaluation results and consumer ranking and preference data of the same varieties compared well. In both panel evaluation and consumer ranking, Khlas variety was perceived to have the best quality by far among the tested varieties. Barhee and Boumaan varieties showed no significant variation between them in both panel evaluation and consumer ranking, and both were in the second order of preference. Variety Ruzeiz was in the lowest order of preference in both panel evaluation and consumer ranking. Testing of the method indicated its appropriateness in predicting total quality of a food product as would be perceived by consumers.