Scanner-based color measurement in L * a * b * format with artificial neural networks (ANN)

A computerized inspection system (CIS) that uses a flat-bed scanner, a computer, and an algorithm and graphical user interface coded and designed in Matlab^® 7.0 was developed to determine food color based on CIE L ^* a ^* b ^*, a color format. The USA Federal Color Standard printouts (SP) comprised of 456 different colors were used to train and test the artificial neural network (ANN) integrated CIS. Strong correlations were found between the results estimated from ANN-integrated CIS and those obtained from spectrophotometer (R ², 0.991, 0.989, and 0.995 for L ^*, a ^*, and b ^*, respectively) for test images data set. Various food samples were also evaluated to test the performance of the CIS. A good agreement, R ², 0.958, 0.938, and 0.962 for L ^*, a ^*, and b ^*, respectively, was found between color measurement with CIS and a spectrophotometer. CIS with a mean error of 0.60% and 2.34% for test and various food samples, respectively, has an ability to imitate the results obtained from a spectrophotometer. CIS allows users to store the captured picture for further use and estimate the overall color or the color of selected region of the samples either heterogeneous in color or amorphous in shape.     

Color of Salmon Fillets By Computer Vision and Sensory Panel

A computer vision method was developed and used to assign color score in salmon fillet according to SalmonFan™ card. The methodology was based on the transformation of RGB to L*a*b* color space. In the algorithm, RGB values assigned directly to each pixel by the camera in the salmon fillet image, were transformed to L*a*b* values, and then matched with other L*a*b* values that represent a SalmonFan score (between 20 and 34). Colors were measured by a computer vision system (CVS) and a sensorial panel (eight panelists) under the same illumination conditions in ten independent sets of experiments. Errors from transformation of RGB to L*a*b* values by the CVS were 2.7%, 1%, and 1.7%, respectively, with a general error range of 1.83%. The coefficient of correlation between the SalmonFan score assigned by computer vision and the sensory panel was 0.95. Statistical analysis using t test was performed and showed that there were no differences in the measurements of the SalmonFan score between both methods (t _c = 1.65 ≤ t = 1.96 at α = 0.05%). The methodology presented in this paper is very versatile and can potentially be used by computer-based vision systems in order to qualify salmon fillets based on color according to the SalmonFan card.     

KINETIC MODELINGS OF BROCCOLI COLOR CHANGES DURING CHILLED STORAGE

This work studied the kinetic models of broccoli color changes during storage. The Commission Internationale d'Eclairage ([CIE] International Commission on Illumination)‐L*a*b* color system parameters a*, b*, H°, total color difference (TCD), chlorophyll content and yellowness degree were used to determine the color changes under the storage conditions at 0, 5 and 10C. The broccoli ball was packed with high‐density polyethylene film. The experimental results showed that the package greatly promoted the activation energy of b* value in broccoli while delaying the respiration peak. The nonlinear regression analysis showed that the rate constants of color parameters b* and TCD were following a first‐order Arrhenius‐type reaction depending on temperature, and the polynomial model was suitable for the changes of a* and H° value. The observed results demonstrated that the variation of color parameters was in accordance with chlorophyll content and yellowness degree in stored broccoli, suggesting the possibility of a computer‐vision system application on the color grading of broccoli.     

Description of the kinetic enzymatic browning in banana (Musa cavendish) slices using non-uniform color information from digital images

A novel methodology “fractal browning indicator” (FBI) is presented, that describes the enzymatic browning kinetic based on the use of irregular color patterns from banana slice images. It uses the fractal Fourier texture image value in a selected area, to calculate a fractal dimension (FD), which represents the complexity of color distribution. During the procedure, colors from digital images were first transformed to L^*a^*b^* space color using a transformation function (quadratic model), in order to derivate three color channels, lightness (L^*), redness (a^*), and yellowness (b^*). In the results, lightness and yellowness parameters decreased during the browning kinetic, when their respective FD values increased, indicating major color distribution complexity in a selected area analyzed during the kinetic. The redness color (a^*) did not show any statistical variation. The empirical power law model was suitable to correlate enzymatic browning kinetic data both for FBI and for the traditional method (when an L^* mean was used). However, enzymatic browning rates using the FBI method, were between 8.5 and 35 times higher than rates calculated with the traditional method.     

CIELAB coordinates in response to berry skin anthocyanins and their composition in Vitis

Abstract: Berry skin color OIV index, anthocyanin composition, and content of 78 grape cultivars were surveyed using a CIELAB system and high‐performance liquid chromatography (HPLC)‐mass spectrometry (MS) coupled with photodiode array detection. There were high correlations between L*, b*, and color, while a* was not a representative parameter. L* and b* values declined as berry skin color OIV became darker, and a* increased as berry skin color OIV became darker in pink and red grape cultivars only. The composition and content of anthocyanins varied widely among the cultivars. Total anthocyanins and types of anthocyanins were significantly correlated with color OIV parameters. Through multiple linear regression analysis, cyanidin derivatives had a positive effect on values of L* and b*. Delphinidin derivatives had positive effects on the value of a*. The CIELAB system gave good results for differentiation of grape berry skin color OIV.     

均匀色空间下红葡萄酒颜色量化分级研究

以宁夏贺兰山东麓产区2012年和2013年瓶储陈酿的13个红葡萄酒样品为材料,采用紫外可见分光光度法和国际照明委员会推荐的CIE L*a*b*均匀色空间参数,来量化葡萄酒的颜色指数,初步研究均匀色空间下红葡萄酒颜色的量化分级。数据量化结果表明:在标准光源D65下,所测试的红葡萄酒色相分为3级,紫红、胭脂红、宝石红;彩度分为5级,灰、淡、中、浓、鲜艳;明度分为5级,中等、稍亮、较亮、亮、明亮。建立CIE L*a*b*下的模型:Ry CX(1-5)LX(1-5)、Rz CX(1-5)LX(1-5)、Rb CX(1-5)LX(1-5),试验表明13种酒样分布在Ry C5+L2+、Ry C4+L3+、Rz C4+L2+、Rz C3+L3+、Rz C3+L4+、Rz C2+L4+、Rb C2+L4+、Rb C+L5+以上8级。     

Effects of agricultural practices on instrumental colour,mineral content,carotenoid composition,and sensory quality of mandarin orange juice,cv. Hernandina

BACKGROUND: Frequent consumption of fruits and vegetables is associated with a lowered risk of cancer, hypertension and heart disease, due, among other factors such as modulation of gene expression and improvement of gap junctional communication, to the presence of various forms of antioxidants present in the foods as carotenoids. Otherwise, consumers demand organic products which they believe have more flavour and are of greater benefit to the environment and human health. The effects of organic farming on CIE L*a*b* colour, mineral content, carotenoid composition and sensory quality of Hernandina mandarin juices were studied. RESULTS: Organic farming of mandarin oranges resulted in juices with higher contents of minerals and carotenoids, and of better sensory quality. For instance, organic juice contained a total concentration of carotenoids of 14.4 mg L^?1 compared to 10.2 mg L^?1 of conventional juice. CONCLUSION: Mandarin orange juices can be considered as a good source of some important nutrients, such as potassium and antioxidant chemicals, e.g. β‐cryptoxanthin. Copyright © 2008 Society of Chemical Industry     

Development of smart clothing for military applications using thermochromic colorants

In this study, we have developed color changeable (chameleon-type) printings on cotton fabrics using thermochromic colorants for defense applications. Different colored coatings such as light green, dark green, black, brown, and sandal have been developed using blue and orange thermochromic colorants in combination with turmeric (a natural dye) and graphite. The printed color pattern mimics jungle motif design (classic green and brown camouflage) which transforms to desert color motif on application of heat from external sources (using hot air oven or electrical power). The response time and temperature for each color change and recovery were evaluated in case of direct heating. Further, their performance was also tested by providing heat using different electrical power. The CIE L*a*b* values of the colors were measured using spectrophotometer before and after heating. The printed fabrics’ physical properties such as tensile strength, elongation at break, flexural rigidity, and tear strength were also tested before and after printing. The wash property of printed fabrics shows reasonably good fixation of colors to the fabric surface. The chameleon-type camouflage printing described in this work shows promise to use the same fabric for camouflaging at different terrains which essentially reduces the time for shifting troops to different locations.     

Digital image analysis of diverse Mexican rice cultivars

BACKGROUND: Digital image analysis has an important role in geographical provenance of grains, as it can provide parameters of size, shape and color, which are important quality parameters for the design of engineering processes such as drying and milling of grains. In this study, digital image analysis was used to classify nine rice cultivars based on different morphometric parameters using the three sides of the grain (lateral, ventral and axial), Feret diameter, and 10 different form factors and color parameters (CIE L*, a* and b*). RESULTS: Result of principal component analyisis was an equation with seven variables (area, perimeter, length, width, thickness, sphericity and color), which was useful for distinguishing between nine different cultivars. The morphometric and color parameters for the Mor A‐98 and Mor A‐92 varieties showed they had 88% similarity. The variability was expressed with a confidence of 95%. CONCLUSION: Multivariate analysis indicated that the lateral side is the most sensitive for the classification of Mexican rice grains because of its color and morphometric characteristics. These results showed the application of image analysis for the future classifications of grains. Copyright © 2012 Society of Chemical Industry     

Antioxidant activity,color characteristics,total phenol content and general HPLC fingerprints of six Polish unifloral honey types

Total phenolic content, antioxidant activity (two assays: 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP)), and color coordinates (CIE (Commission Internationale de l'Eclairage) L*a*b*) for six Polish unifloral honeys (black locust, rapeseed, lime, goldenrod, heather and buckwheat) were assessed for several batches of the same honey type and statistically evaluated. Total phenolic content (121.6–1173.8 mg GAE/kg) was similar to the values previously reported for other European honeys and it was also correlated with the color parameters as well as antioxidant activity. The honeys' color ranged from pale yellow to dark amber. Dark buckwheat honey with much higher phenolic content (1113.0 mg GAE/kg) exhibited higher antioxidant activity (5.7 mmol Fe²⁺/kg and 1.2 mmol TEAC/kg). CIE L*a*b* color coordinates can be helpful for identifying and distinguishing between several honey types, such as heather and buckwheat, but almost no differences were found among very light honeys (rapeseed, goldenrod, black locust and lime). High-performance liquid chromatographic (HPLC) analysis revealed general characteristic fingerprints of Polish unifloral honeys with significant differences among the samples of other honey types.     

Assessment of Color and Sensory Evaluation of Frozen Fillets from Pangasius Catfish and Nile Tilapia Imported to European Countries

The current study was designed to assess the color and sensory evaluation of frozen fillets of Pangasius catfish and Nile tilapia imported to Poland, Germany, and Ukraine in order to evaluate the possible impact of negative media image of these fish fillets on the sensory expectations of the consumers. The study used two trials of sensory evaluation: Blind and informed, on a group of untrained respondents and additional color analysis using the Commission Internationale de l’Éclairage (CIE) L*a*b* scale. The lowest grades during sensory evaluation in all measured parameters were given to Pangasius imported to Ukraine and Poland. The grades of Pangasius and tilapia imported to Germany were similar and significantly higher than of other Pangasius groups. Generally tilapia fillets were marked as better than Pangasius fillets. Moreover the present study found that there was considerable percentage of customers which are susceptible to various commercial frauds since they marked Pangasius higher when they thought they are consuming turbot. This study also showed that the negative image of Pangasius presented through various mass-media might have a negative impact on consumer’s perspective of Pangasius consumption.     

Colour of rapeseed (Brassica napus) surface and contamination by fungi during storage of dry and wet seeds

The aim of this study was to determine the effect of seed size and cultivation location on the diversity of colour of rapeseed surface and the level of fungi infection of sound, dry rapeseed and the correlation between colour attributes and fungal growth during storage of wet seeds. It has been reported that the colour, mouldiness degree and genera differentiation on the surface of sound seeds depend on both the seed size and the seed cultivation location. The storage of wet rapeseed led to a colour shift to a green‐yellowish hue with higher lightness and to about a 1000‐fold increase in colony‐forming units (CFUs) per seed mass. During the first 15 days, fungal growth was undetectable both by human eye inspection and by digital image analysis (DIA). The onset of fungal growth was associated with slight increase in G (of RGB) and a* and b* (of CIE L*a*b*) colour attributes.     

Effects of ascorbic acid retention on juice color and pigment stability in blood orange (Citrus sinensis) juice during refrigerated storage

Blood orange juice samples with two different levels of ascorbic acid content were placed in HDPE plastic bottles, pasteurized, and stored at 4.5 °C. The influence of ascorbic acid retention on color stability of blood orange juice was investigated using CIE L*a*b*, hue, chroma, polymeric color, and browning index during the storage period. Changes in monomeric anthocyanin pigments, total carotenoid contents, cyanidin-3-glucoside, and ascorbic acid were also measured. Ascorbic acid degradation was highly correlated (r>0.93) to anthocyanin pigment degradation. Ascorbic acid content also showed linear correlation with red color intensity (CIE a*, and chroma) in the juice. Polymeric color and browning index increased with storage time and were more pronounced for juice fortified with ascorbic acid.     

High pressure effect on the color of minced cured restructured ham at different levels of drying, pH, and NaCl

Color changes of minced cured restructured ham was studied considering the effects of high pressure (HP) treatment (600 MPa, 13 °C, 5 min), raw meat pH₂₄ (low, normal, high), salt content (15, 30 g/kg), and drying (20%, 50% weight loss). Raw hams were selected based on pH₂₄ in Semimembranosus, mixed with additives, frozen, sliced, and dried using the Quick-Dry-Slice® process. Meat color (CIE 1976 L*a*b*) and reflectance spectra were measured before and after HP treatment. HP significantly increased L*, decreased a*, and decreased b* for restructured ham dried to 20% weight loss, regardless of salt content and pH₂₄. L* and a* were best preserved in high pH/high salt restructured ham. HP had no effect on the color of restructured ham dried to 50% weight loss. HP had no effect on the shape of reflectance curves, indicating that the pigment responsible for minced cured restructured ham color did not change due to HP.     

Development of a colour scale for colour evaluation of beef carcasses at 60 min post mortem

The pectoralis profundus muscles of 200 selected beef carcasses were measured to develop a standard colour scale for evaluating beef carcasses at the time of classification (approximately 60 min post mortem). Five lightness (L*) values were chosen ranging from 22 to 42 with intervals of five L* units. Corresponding a* and b* values were calculated. Based on regressions between the actual reflection spectra and the L*, a* and b* values, spectra of the five chosen colours for the colour scale were predicted. The L*, a* and b* values accurately predicted the reflection spectra. A paint company imitated the five reflection spectra. Spectra could not be matched exactly, without metamerism occuring. Therefore, the colour scale should be used with specific light sources. The scale is recommended in The Netherlands to classify the colour of beef, as a supplement of SEUROP‐system for conformation and fatness. © 1999 Society of Chemical Industry     

Exit of seed weevil and its parasitoid changed testa color but not phenolic and tannin contents in faba beans

Seeds of eight faba bean accessions, grown under field conditions, were subjected to L*a*b* (L*, lightness; a* redness; b* blueness) scale examination and phenolic and tannin determination after classification as intacts, bruchid- and parasitoid-damaged. Accessions differed in testa color and phenolic and tannin contents. L* and b* were negatively correlated with phenolics and tannins while a* was positively correlated with phenolics. Bruchid- and parasitoid-damaged seeds had increased a* indicating a shift of testa color tο red but phenolics and tannins did not differ between seed classes. Thus, testa discoloration in insect-damaged seeds was not the result of oxidation of phenolics but possibly due to Maillard reaction indicating accelerating aging of seeds.     

Search for predictors of cooking quality of marrowfat pea (Pisum sativum L) cultivars

The grain from 116 marrowfat pea breeding lines was assessed subjectively using current visual methods and then analysed objectively for L*a*b* colour, hydration capacity and cooking quality. The data show that the current method of selecting genotypes by subjective methods is not able to select marrowfat peas for specific processing uses. However, an objective measure, the ?a* value of the dry grain, was a very good predictor (p < 0.001) for the hydrated and cooked green colour. Cultivars which have a high hydration coefficient may be more suitable for canning and deep frying because they hydrate to a larger size, while cultivars with a high bulk density and a darker green grain are more suitable for use as extrusion products. © 2001 Society of Chemical Industry     

Modelling the biological variance of the yellow aspect of Granny Smith apple colour

BACKGROUND: The yellow aspect of colour is usually not considered for produce with a green‐to‐red or a green‐to‐yellow transition upon ripening. The magnitude of change is simply too small and, additionally, masked by a large variation. The colour of ‘Granny Smith’ apples, harvested from three orchards at two stages of maturity, was measured individually using the CIE L*a*b* system during storage in a regular atmosphere at three temperatures: 1, 4 and 10 °C. A model was developed based on a simplified mechanism, consisting of two consecutive reactions, to describe the development of the apple colour expressed as b* and L* values during storage. RESULTS: Monitoring individual apples made it possible to include and describe the biological variance of colour in batches of apples and to extract information on chilling injury, as a process active at 1 °C. All variations could be attributed to a single source related to the amount of yellowing compounds at the moment of harvest, indicating differences in state of maturity between individual apples. The obtained explained part (R²_adj), using nonlinear mixed effects regression analysis was well over 90% for all data combined over more than 3000 observations. CONCLUSION: Orchard location had a slight effect on the mean initial colour value, indicating differences in development stage, most probably due to differences in assessing the harvest date. The magnitude of the variation in these colour values was, however, the same for all three orchards. The behaviour of the green colour aspect (a* value) has been reported separately, as this represents the major change in perceived colour. The changes in b* and L* values are rather small, while the biological variation between the individual fruit is at least of the same magnitude. The model presented here is, as far as known, the first model on b* and L* values for green‐coloured products. Analysing b* and L* data using this model provides additional information with respect to the stage of maturity at harvest in a batch or for an orchard of Granny Smith apples. All the variation in the yellow colour aspects could be attributed exclusively to the initial level of yellow compounds. Copyright © 2010 Society of Chemical Industry     

基于一维最优Gabor滤波器的帘子布疵点检测算法

传统的二维Gabor滤波器用于帘子布疵点检测非常有效,但计算量巨大,为此提出一种快速自动检测帘子布疵点的方法。通过一维环形投影变换把一幅二维灰度图像压缩成一维形式,然后使用一维最优Gabor滤波器检测嵌入在帘子布均匀纹理中的疵点。采用粒子群优化算法进行一维Gabor滤波器最优参数的求解。假设图像大小为N×N,滤波器窗口为W×W,计算的复杂度可以显著地从二维Gabor空间的O(W2N2)到一维Gabor空间的O(WN2),并用实验验证了该方法的有效性。     

Rapid Colorimetric Determination of Yellow Seed Content in Red Pepper (Capsicum annuum L.) Powder

When the color reflectance of red pepper powders and their yellow seeds were measured using a colorimeter, the mean lightness (L*), redness (a*), and yellowness (b*) values differed considerably between the pepper powders and seeds. On the basis of this difference, we determined the seed content in the red pepper powders by using the correlated reflectance values. As the seed content of the powders increased, both L* and b* increased, while a* decreased. The polynomial regression curve equation, Y( seed content, % ) = 3.51 ×L * - 1.10 ×a * - 1.34 ×b * - 72.74 Y\left( {{\hbox{seed content}},{ }\% } \right) = 3.51 \times L * - 1.10 \times a * - 1.34 \times b * - 72.74 , was obtained from the tristimulus data (L*, a*, and b*) of all the samples used. This is an easy method for the determination of the seed content in red pepper powders and it can be applied to a similar system.