The quality of cold-smoked Atlantic salmon (Salmo salar) as affected by salting method, time and temperature

The effects of temperature (4 and 10–12 °C) and time (6, 12 and 24 h) on colorimetric parameters (Commission International de l'Eclairage (CIE) L*a*b*), carotenoid concentration, salt content and yield were investigated in brine (saturated or 50% saturation) and dry salted fillets of cold‐smoked Atlantic salmon (Salmo salar). Lightness (L*), yellowness (b*), hue (H_ab) and chroma (C*) values were lower at 10 than 4 °C (P < 0.01), whereas redness (a*) was unaffected. L* increased (P < 0.05) and a*, b*, H_ab and C* values dropped when salting time was increased (P < 0.001). Astaxanthin concentration of brine‐salted fillets decreased with increasing salting time (P < 0.05), but was unaffected by salting temperature. Increasing salting time affected colour negatively. The salt content of dry salted fillets increased with temperature and salting time. The process yield was unaffected by temperature and decreased with salting time. In conclusion, the cold smoking process is more important for variation in quality parameters than the salting process.     

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.     

Comparative effect of red yeast rice (Monascus purpureus), red beet root (Beta vulgaris) and betanin (E‐162) on colour and consumer acceptability of fresh pork sausages packaged in a modified atmosphere

Fresh pork sausages containing natural colorants, red yeast rice powder (Monascus purpureus; Frame^®) or a crude red beet root (Beta vulgaris) juice or commercial betanin (E‐162), at different concentrations, were packaged in an atmosphere containing 80% O₂ and 20% CO₂ and stored in the dark for 20 days. The following parameters were measured at 4 day intervals: instrumental colour (CIE L*, a*, b*, a*/b*, C* and h*), reflectance spectra, sensory discoloration (trained panel) and acceptability and willingness to purchase (habitual and non‐habitual consumer panels) under two different lighting displays (standard fluorescent and Promolux^® lamp). The use of colorants improved the colour properties of fresh pork sausages. Sausages with red yeast rice, red beet root juice and betanin had lower L* and h* and higher a* and a*/b* values than control samples. The colour properties of sausages with red beet root were the closest to control sausages, while sausages with red yeast rice had significantly lower b* values. Both natural colorants and betanin protected sausages from discoloration and extended acceptability and willingness to purchase by about 4 days, according to evaluation by habitual consumers under two different types of lighting display. Therefore, red beet root juice may be envisaged as the most suitable natural colorant for use in fresh pork sausages. Copyright © 2005 Society of Chemical Industry     

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     

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     

Colour differences in paprika pepper varieties (Capsicum annuumL) cultivated in a greenhouse and in the open air

The quality of six paprika pepper varieties, cultivated in a greenhouse and in the open air, has been studied. There were differences in their paprika colours with regard to the total content of pigments (ASTA unities) and the quotient of the absorbance spectra values for red and yellow pigments (tint). Using colorimetric measurements, directly carried out on the surface of the ripe fruits, the varieties are clearly separated in the CIELAB space colour, depending on their growing conditions. The colorimetric coordinates a* and b* and quotient a*/b* of the ripe fruits, cultivated in greenhouse, allow to predict the total pigments concentration of the resulting paprika. For the cultivations in the open air, the fruit brightness (L*) and the chromatic quotient 2000×a*/L*×b* are the parameters which show best the correlation with the total content of the paprika pigments. The fruit colour change, from green to red, coincides in both growing conditions with the moment when the chlorophyll b concentration surpasses the a one. © 1998 SCI.     

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.     

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     

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.     

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.     

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.     

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.     

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.     

Non-enzymatic browning in peach puree during heating

Non-enzymatic browning in peach puree (11° Brix) due to extended thermal treatment was investigated. Absorbance at 420 nm, colorimetric parameters (CIE L*, a*, b* and ΔE*), content in sugars (fructose, glucose and sucrose) and hydroxymethylfurfural were used to estimate the extent of nonenzymatic browning during heating at high temperatures (80, 85, 90, 95 and 98°C) for 480 min. Zero and first order kinetics were applied to describe evolution of relative absorbance at 420 nm. Relative luminosity and sucrose content follow a first order kinetic. Colour difference was successfully adjusted to a model including two stages: the first one includes the colour formation and it follows a kinetic of order zero and the second includes the colour destruction and it follows a first order kinetic model. Both first and autocatalytical models can describe HMF formation. Parameter b* was significantly reduced with heating time, especially at higher temperatures, on the contrary parameter a* increases during heating. The Arrhenius model described well the temperature dependence of the reaction rate constant for all the parameters considered.     

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.     

The effect of pumpkin fibre on quality and storage stability of reduced‐fat set‐type yogurt

In this study, the effect of pumpkin fibre (PF) on physicochemical, microbiological, rheological and microstructural characteristics of reduced‐fat yogurt samples was investigated during storage. PF was added at three different concentrations (0.5%, 1.0% and 1.5%) to standardised (1.55% fat ratio) cow's milk. Plain yogurt (PF‐free) was used for comparison. The addition of PF significantly affected total solid content, synaeresis, water‐holding capacity, apparent viscosity and colour parameters (L*, a*, b*) of yogurt samples for all sampling time. The addition of PF caused a reduction in L* values (from 94.89 to 88.67), but caused an increase in a* (from ?2.10 to +4.22) and b* (from 10.79 to 25.88) values. Yogurts with PF exhibited lower synaeresis and more viscous structure than PF‐free sample during storage. SEM images showed that distinctive microstructure profile was present between samples with or without PF. More filamentous structures and denser network were observed in the SEM images and these increased with increasing level of PF. Yogurt containing 1.0% PF showed a higher storage (G′) (3687.87 at 21 day) and loss (G″) (543.10 at 21 day) moduli in comparison with other samples. In conclusion, the results revealed that PF improved the physical quality and contributed textural properties of half‐fat yogurt.     

Relating raw rice colour and composition to cooked rice colour

BACKGROUND: The whiter the rice, the more it is preferred by consumers and the more value it has in the market place. The first objective of this study was to determine the interrelationships of raw colour, cooked colour, amylose content and protein content in rice. The second objective was to assess whether or not the colour of cooked rice can be predicted from raw rice colour in conjunction with amylose and protein contents. RESULTS: Protein and amylose contents were not significantly correlated with the colour measurements for raw rice. Protein and amylose showed moderate, significant associations with L* and a* and a*, b* and C* respectively for cooked rice. Only the colour variable a* of cooked rice could be predicted using protein, amylose and raw rice colour with high enough precision to be useful, and this was only for modelling using samples cooked in the same manner (rice cooker). Cooking method (rice cooker versus excess water) affected the colour of cooked rice. CONCLUSION: Being able to predict a* in cooked rice is likely of limited value. Only the model that used samples where postharvest handling conditions were controlled (US‐grown rice) was able to predict C*, a more useful measure, and then with only moderate ability. L*, a measure of brightness/whiteness, was not predicted well by any of the models. Copyright © 2011 Society of Chemical Industry     

Colour values of cooked top-round beef juices as affected by endpoint temperatures,frozen storage of cooked samples and storage of expressed juices

Juices from beef semimembranosus/adductor tissue, cooked to endpoint temperatures (EPTs) of 76, 78, 80, 82 and 84°C in a model heat-treating system, were evaluated for changes in CIELAB L*a*b*, chroma (C) and hue angle (H) values before and after storage of the cooked meat at -20°C for 3 weeks and after storage of the expressed juices under N₂ at 3°C for 72 h. Increases in EPTs altered all colour values of the juices. Lightness (L*) increased while yellowness (b*) decreased; redness (a*) and C decreased progressively while H increased toward the vertical axis. Storage of the expressed juices at 3°C under N₂ did not inhibit changes in a*, b*, C and H values. Regression coefficients of changes in relation to EPTs and time of storage of the expressed juices under N₂ were established. Storage of the cooked meats for 3 weeks at -20°C did not change any of the colour values of the juices. These data indicate that evaluations of cooked beef for doneness by colour of expressed juices must be performed immediately after expression of the juices before oxidation of the myoglobin pigments occurs. Storage of cooked meat at -20°C does not alter the colour of the juices, therefore, valid assays for doneness of meat in relation to juice colour can be made after frozen storage. © 1997 This article is a US Government work and, as such, is in the public domain in the United States of America     

Colour of post-harvest ripened and vine ripened tomatoes (Lycopersicon esculentum Mill.) as related to total antioxidant capacity and chemical composition

Greenhouse grown tomatoes (cvs ‘Durinta’, ‘Favorita’ and ‘Liberto’) were harvested green and vine ripe. Colour measurements and chemical analyses were performed on green, post‐harvest red and vine‐ripe fruits. Partial least square (PLS) regression was applied to predict the ferric reducing ability of plasma (FRAP) by means of colour measurements (L*, a* and b*). The PLS showed that 78% of the variation in colour were able to predict 74% of the variation in FRAP value. Chemical variables and colour variables together were able to predict 88% of the variation in FRAP by means of PLS regression. Linear regression showed a high negative correlation between high values of L*, b* and FRAP, and a high positive correlation between titratable acidity, a*, hue, a*/b*, soluble solids, vitamin C, dry matter and FRAP values. Thus, colour measurements of intact tomatoes can be used as a non‐destructive method to assess total antioxidant capacity of tomatoes.     

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