Time course of the colour of young red wines from Vitis vinifera L. during ageing in bottle

The colour characteristics of red wines from Vitis vinifera L. cv Tempranillo, Graciano and Cabernet Sauvignon (vintage 2000) from Navarra (Spain), was studied during 26 months of ageing in bottle through the evaluation of the wine visible spectrum and of several colorimetric indices (colour intensity, %red, %yellow, %blue, %dA and tint) and CIELAB variables (L*, C*, h, a* and b*). During ageing in bottle, the spectrum of Tempranillo wine (pH 4.3) mainly changed in the absorbance range between 420 and 500 nm, whereas Graciano (pH 3.5) and Cabernet Sauvignon (pH 3.6) wines registered a decrease in absorbance in the interval between 500 and 560 nm. The time course of the different wine colour parameters was found to fit either a second‐order polynomium or a linear model, depending on the grape variety employed. CIELAB variables could be described in terms of their colorimetric index counterparts, showing b* and h relative greater errors. Although the wine total chromatic changes in CIELAB units registered after 26 months of ageing in bottle indicated changes perceivable by the human eye (ΔE* ≥ 2.7) for the three varieties studied, Graciano and Cabernet Sauvignon wines showed a more balanced colour evolution than Tempranillo wine.     

Influence of pH on colour and iron content of peptide fractions obtained from bovine Hb concentrate hydrolysates

The effect of pH on colour and iron content (Fe) of peptide fractions obtained from bovine haemoglobin concentrate (BHC) hydrolysates was studied. Four hydrolysates were obtained using three enzymes: Protex‐6‐L (P), Fungal–Protease–Concetrate (FC) and Flavourzyme (F). BHC and its hydrolysates (P, FC, P + F, FC + F) were fractioned at pH 4.5, 7.0 and 9.5. Solubility and Fe from different fractions were measured. Correlations between CIELAB colour parameters and Fe from different fractions were analysed. The colour from different fractions varied from red to yellow (a* and b* positives). Lightness values (L*) ranged from twenty‐four to seventy. FC4.5 and FC + F4.5 fractions were the clearest and yellow (higher L*, b*, h), while BHC9.5 and P + F9.5 fractions had the lowest values of L*, b* and h. There was an inverse linear relationship between b* and L* parameters and Fe from fractions. This relationship could be associated with the pH of extraction. As pH increases Fe significantly increases and lower b* and L* values were obtained.     

Influence of particle characteristics and E/Z‐isomer ratio on the colour of concentrated β‐carotene dispersions

The influence of particle concentrations (0.02–0.40%), mean particle sizes (0.45–1.5 μm) and all‐E‐isomer ratios (95–30%) on the CIELAB colour coordinates (L*, a*, b*) of concentrated β‐carotene dispersions was investigated. Particle concentration between 0.06% and 0.40% had a slight impact on the colour parameters. However, with decreasing the mean particle size from 1.50 to 0.45 μm, there were increases in ΔL* = 8.0, in Δa* = 2.26 and in Δb* = 13.1. And with decreasing the all‐E‐isomers ratio from 95% to 30%, there were increases in ΔL* = 8.66, in Δb* = 17.51 but decrease in Δa* = 7.42. The experimental results were explained in terms of the scattering and absorption of light by dispersions. These findings have important implications for food industry as they offer a means to control and optimise the colour of food dispersions.     

Effects of dietary humate supplementation to broilers on performance,slaughter, carcass and meat colour

BACKGROUND: This experiment was designed to examine the effect of dietary humate supplementation primarily on pH and colour parameters of carcasses, breast fillets and drumsticks and, secondarily on performance and carcass characteristics in broilers. RESULTS: A total of 240 male broiler chicks (Ross‐308) were randomly allocated to four dietary treatments varying in supplemental humate level (0, 0.1, 0.2 and 0.3% for H₀, H₁, H₂ and H₃). Dietary humate supplementation did not affect performance traits and slaughter, hot carcass weights and yields. Carcass‐related variables (pH, L*, a*, b*, H* and C*) were responsive to the dietary treatments. The L*, a*, b*, and C* values for drumstick muscles were higher than those for breast muscles. Except for the L* value, meat colour parameters changed due to packaging. The a* value was higher and b* value was lower for vacuum packaged breast and drumsticks than for those aerobic packaged. Storage period affected colour parameters; while L*, b*, H* and C* values were higher for drumstick skin than for drumstick meat; the a* value was greater in drumstick meat than in skin. CONCLUSION: pH and colour parameters of carcasses, breast fillets and drumsticks of broilers were improved by dietary humate supplementation. However, responses of broiler performance and slaughter and carcass characteristics were minimal. Copyright © 2008 Society of Chemical Industry     

Browning Inhibition in Fresh-cut'Fuji'Apple Slices by Natural Antibrowning Agents

ABSTRACT Response surface methodology was used to study the effect of antibrowning agents (4‐hexylresorci‐nol, glutathione, N‐acetylcysteine, and ascorbic acid) and storage time (14 d) on the color of minimally processed Fuji apples. The selected color parameters were L*,a*, b*, hue angle (h*), and color difference (ΔE*). Storage time had a significant effect on all the studied color parameters (P± 0.05). 4‐hexylresorcinol showed the most effective individual effect on keeping constant a*values (P± 0.0001). Besides, the interaction of N‐acetylcysteine/ glutathione was found to have a significant effect (P± 0.05) on maintaining a* values over time. On the other hand, individual treatment with N‐acetylcysteine in concentrations higher than 0.75% w/v may be used to preserve a*and h*.According to the F‐test, 4‐hexylresorcinol and N‐acetylcysteine (P± 0.05) displayed a significant individual effect on ΔE*, indicating that ΔE* decreased when increasing the concentration of these antibrowning agents. Nevertheless, color difference went down when 4‐hexylresorcinol concentration increased up to 0.5%, but higher concentrations of this agent led to an increase in ΔE* that indicates browning.     

Pigment composition and color parameters of commercial Spanish red wine samples: linkage to quality perception

Anthocyanins play a crucial role in wine color. Thus, their analysis results essential for evaluating their contribution to perceived color in wines, attribute directly linked to quality judgements. In this context, this study was aimed at: (1) defining the color space of a relative large number of commercial oaked Spanish red wines and (2) establishing a linkage between wine coloring, anthocyanic composition, and quality perception of this set of wines. Therefore, CIELab parameters (a ₁₀*, b ₁₀*, L ₁₀*), monomeric anthocyanin contents analyzed by HPLC with ultraviolet and mass detection, and polymeric pigment content estimated by a protein precipitation assay combined with bisulfite bleaching were evaluated in a total of 58 wine samples. Principal component analysis was performed on color variables, and their correlations were discussed. The results have evidenced the important role played by the pyranoanthocyanic compounds since they seem to be the main contributors to the red color of these aged wines, and they have been demonstrated not to increase their yellow nuances. On the other hand, results highlight that, regardless of the time of aging, wines presenting more red (higher values for a ₁₀* and for low molecular weighted anthocyanins) and lower yellow nuances (lower values for b ₁₀* and T) as well as a darker color (lower in L ₁₀* and higher in CI) are in general evaluated with higher quality scores by wine experts.     

Anthocyanin composition and content in grape berry skin in Vitis germplasm

The composition and content of anthocyanins were surveyed by HPLC–MS for assessing genotypic variation in berry skin of 110 grape cultivars, including 3 species and 5 interspecific hybrids. Twenty-nine anthocyanins were identified. For total anthocyanin content, Vitis vinifera and hybrids of Vitis labrusca and V. vinifera were low, and in general, wild species and rootstock were higher than interspecific hybrids, and wine grapes were higher than table grapes in the same species. As regards the composition of anthocyanins, malvidin-derivatives were the most abundant anthocyanins in the majority of germplasms. All anthocyanins were monoglucoside derivatives in V. vinifera, but all the other Vitis germplasms had both mono- and di-glucoside derivatives. Moreover, peonidin-derivatives and malvidin 3-O-glucoside were, respectively, main anthocyanins in table and wine grapes of V. vinifera. Via principal component analysis, the distribution of the cultivars in a scatter plot depended upon their total anthocyanins content, mono- and di-glucoside derivatives.     

Possibilities of enhancing the colour of egg yolk

BACKGROUND: This study attempts to compare two possibilities of enhancing the colour of egg yolk. One of them is based on the ecological rearing of laying hens on natural green grass whereas the other uses a feeding dose supplemented with natural pigments in laying hens reared in individual cages. Is it possible to distinguish these two technologies using yolk colour determination in the CIELAB system? RESULTS: Yolk colour parameters such as L*, a*, and b* in the group of grazed hens are significantly different (α = 0.001) from those observed in hens reared in cages. The yolk colour shows a darker, redder and more yellow colour. The greatest difference was seen in the red colour parameter, a*, that increased more than twice. Visually, this means a shift towards a more orange colour. Compared to grazing in the meadow (ΔE* = 13.257), the addition of artificial pigments in the feed resulted in a more significant increase in the parameter ΔE* (CIE total colour difference), with the greatest value of ΔE* being observed with the use of both pigments (ΔE* = 24.265). CONCLUSION: Grazing increases the parameter a* whereas the values of the parameter C*_ab remain relatively low. The parameter ΔE* is significantly lower in the case of grazing as compared to the supplementation of the feed with pigments. However, colourity parameters cannot be used as a specific standard to identify a particular grazing technology as their values vary during the laying period. Copyright © 2011 Society of Chemical Industry     

Comparison of Minolta colorimeter and machine vision system in measuring colour of irradiated Atlantic salmon

BACKGROUND: Minolta and machine vision are two different instrumental techniques used for measuring the colour of muscle food products. Between these two techniques, machine vision has many advantages, such as its ability to determine L*, a*, b* values for each pixel of a sample's image and to analyse the entire surface of a food regardless of surface uniformity and colour variation. The objective of this study was to measure the colour of irradiated Atlantic salmon fillets using a hand‐held Minolta colorimeter and a machine vision system and to compare their performance. RESULTS: The L*, a*, b* values of Atlantic salmon fillets subjected to different electron beam doses (0, 1, 1.5, 2 and 3 kGy) were measured using a Minolta CR‐200 Chroma Meter and a machine vision system. For both Minolta and machine vision the L* value increased and the a* and b* values decreased with increasing irradiation dose. However, the machine vision system showed significantly higher readings for L*, a*, b* values than the Minolta colorimeter. Because of this difference, colours that were actually measured by the two instruments were illustrated for visual comparison. Minolta readings resulted in a purplish colour based on average L*, a*, b* values, while machine vision readings resulted in an orange colour, which was expected for Atlantic salmon fillets. CONCLUSION: The Minolta colorimeter and the machine vision system were very close in reading the standard red plate with known L*, a*, b* values. Hence some caution is recommended in reporting colour values measured by Minolta, even when the ‘reference’ tiles are measured correctly. The reason for this discrepancy in colour readings for salmon is not known and needs further investigation. Copyright © 2009 Society of Chemical Industry     

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.     

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.     

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.     

Physical,functional and pasting properties of different maize (Zea mays) cultivars as modified by an increase in γ‐irradiation doses

Physical, functional and pasting properties of six maize (Zea mays) cultivars as modified by an increase in γ‐irradiation doses were investigated. From the L*, a* and b* measured, deltachroma, colour intensity and hue angle were calculated. Functional and physicochemical properties of maize flours were determined using standard methods and Rapid Visco Analyser, respectively. Often, the effect of γ‐irradiation on L*, a* and b* values within each cultivar was almost never significant but pronounced between the yellow and white cultivars. Generally, deltachroma, colour intensity and hue angle decreased with increased γ‐irradiation dose. Mean seed bulk density and 100 kernel weight varied from 0.73–0.77 g cm^?3 and 23.13–35.42 g, respectively. Loose and packed bulk densities, and water (WAC) and oil absorption capacities of the maize flours were not significantly affected by γ‐irradiation. WAC of nonirradiated and γ‐irradiated maize flours ranged from 1.54–1.62 and 1.09–1.70 g g^?1, respectively. Peak, trough, breakdown, final and setback viscosities decreased significantly (P < 0.05) with increased γ‐irradiation dose.     

Changes of colour and pH in fish musculature after ionizing radiation exposure

Irradiation of meat causes sensory changes as do other technological methods. The most significant sensory and quality indicator of meat is colour; therefore, the effect of irradiated pieces of fish was studied in relation to colour changes. Colour was measured at the musculature of Oncorhynchus mykiss. The parameters of colour, L*, a* and b*, were determined with the portable Superchroma S-Spex (Braive) spectrophotometer in the CIELAB system before irradiation (3 h post mortem) and after irradiation (⁶⁰Co source, a dose of 3 kGy and a dose rate of 3.33 kGy h^–1) (5 h post mortem). The change of L* was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh. a* was identical and b* decreased. This effect differs from that of irradiated pork. The decrease of the pH was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh.     

Effect of Oak Chips on Evolution of Phenolic Compounds and Color Attributes of Bog Bilberry Syrup Wine During Bottle‐Aging

This study investigated the evolution of phenolic compounds of bog bilberry syrup wine during a bottle‐aging process, and further estimated the oak chip treatment on the wine color alteration. The wine was macerated with oak chips (2 or 5 g/L under light or medium toasting level) for 20 d and then bottle‐aged for 6 mo. Results showed that the oak chip treatment significantly increased the content of phenolic compounds and enhanced the copigmented anthocyanin level before aging. It also resulted in an increase on a^* and C^* but a decrease on L^*, b^*, and H^* of the wine. During aging process, a content decrease of total phenol and antioxidant capacity of the wine was observed. Phenolic acids, flavonol glycosides, and anthocyanins reduced the content, whereas flavonol increased the content. Free and copigmented anthocyanin levels decreased, whereas polymerized anthocyanins level increased. This process caused an increase on L^*, b^*, and H^*, but a decrease on a^* and C^*. The oak chip treatment delayed the wine color change and its effect was mainly depended on the addition amount. Partial least square regression revealed that flavonol glycosides, phenolic acids, and anthocyanins displayed a positive correlation with L^*, b^*, and H^*, but a negative correlation with a^* and C^*. Quercetin‐3‐O‐glucuronide, myricetin‐3‐O‐galactoside, chlorogenic acid, and quercetin exerted a more important effect on the color alteration in wine.     

Kinetic models of non‐enzymatic browning in apple puree

The effects of thermal treatments on 11 °Brix apple puree were studied at temperatures from 80 to 98 °C. Colour changes (measured by reflectance spectroscopy, colour difference, L*, a* and b* and the evolution of 5‐hydroxymethylfurfural (HMF) and sugars (hexoses and sucrose) were used to evaluate non‐enzymatic browning. A kinetic model based on a two‐stage mechanism was applied to the evolution of colour difference and a*. A first‐order kinetic model was applied to L* evolution, while the evolution of absorbance at 420 nm (A₄₂₀) of the liquid fraction was described using a zero‐order kinetic model. Thermally treated samples became more reddish and suffered a slight loss of yellow hues. The effect of temperature on the kinetic constants was described by an Arrhenius‐type equation. The presence of pulp in the samples led to activation energies for A₄₂₀ and sucrose which were lower than those found previously for clarified juices with the same soluble solids content. © 2000 Society of Chemical Industry     

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     

STUDIES ON THE CLARIFICATION AND CONCENTRATION OF BEETROOT JUICE

Studies on the clarification and subsequent concentration of beetroot juice were carried out. The juice was clarified using enzyme, fining agent (FA), centrifugation and ultrafiltration (UF), while reverse osmosis (RO) and thermovacuum evaporation were used for concentration. The juices were concentrated to 23–25°Brix, and the physicochemical characteristics were evaluated at different stages of processing on the basis of clarity, permeate flux, °Brix, acidity, sugars, pigments and CIE L*, a* and b* (lightness, redness and yellowness, respectively) color values. Average permeate flux during RO was found to be highest (36.08 liters per square meter of membrane per hour [L/m²h]) in the case of enzyme treatment, followed by UF juice, and lowest (30.33 L/m ² h) in the case of enzyme and FA treatments. In terms of clarity of concentrate, the highest value was obtained for juices pretreated with enzyme and UF. Pigment content and L*, a* and b* values showed that pigment loss was higher in the case of RO‐concentrated juice pretreated with enzyme. Comparative evaluation in terms of clarity, color and chemical parameters showed that concentrates obtained using both techniques were comparable.     

Estimation of skin phototypes with optical parameters: an experimental study using newly developed fibre optic detection device

In an experimental study (October 2010 Mannheim Germany) with 99 Caucasian volunteers, the skin colour (L*, a*, b*) and the reflectance spectra of human skin were compared to the Fitzpatrick's sun‐reactive skin photo types (SPT). For this purpose, the skin colour and the reflectance spectra of human skin were determined using non‐invasive method with a newly developed fibre optic detection device. The device, based on reflectance spectroscopy, was designed and optimized using a commercial optical analysis Software. By means of the measured spectra of scattered light, the colour values and the absorption spectra of the skin were calculated. Neither any of the L*, a*, b* colour values nor any of the parameters of the absorbance spectra can be used alone to assess the skin type properly. Therefore, an ordinal logistic regression analysis was performed, using the statistical computing software r , to correlate the skin types with the measured optical parameters. It turned out that the detection device combined with the extended statistical analysis gives a better estimate of skin type in respect of the measured optical parameters than a procedure with only L*, a*, b* colour values. Even with the extended methodology, the procedure gives only a rough estimation of the skin type.