Colour of normal and high pH beef heated to different temperatures as related to oxygenation

The effects of oxygenation and thermal treatment (internal temperature, T_i: 45, 60, 75°C) on the colour and some colour related physical and biochemical properties of beef longissimus dorsi (LD) muscle, both normal (pH_u5.6) and DFD (pH_u>6.6), were studied. The colour components (L^*, a^*, b^* values) for the raw and heated LD, both before and after oxygenation, were instrumentally and sensorily evaluated. The colour of raw and heated (60°C) DFD beef before and after oxygenation differed significantly from the normal meat and contained more native muscle pigment (TMP). pH also influenced the depth of the oxygenated layer, specific activity of cytochrome c oxidase (SACCO) and the amount of oxygen consumed. An increase in internal temperature was usually accompanied by a lower SACCO and a significant decrease of TMP, as well as a change of all colour parameters. Oxygenation of the raw and heated slices (except at 75°C) of both types of meat led to higher L^*, a^* and b^* values.     

Effect of transport time and ageing on aspects of beef quality

Forty-eight bulls were transported by road in groups of eight for approximately 30 min, 3 or 6 h in two replicates. After slaughter, steaks from the longissimus dorsi thoracis of all transported animals were analysed in terms of pH, water-holding capacity, myoglobin concentration, texture at 7 and 14 days of ageing (compression and Warner-Bratzler analyses) and colour of the same surface of meat cut at 24 h post-mortem and allowed to bloom for 24 h and 7 d (L^*a^*b^*, chroma and hue). The myofibrillar resistance of the meat from animals transported 30 min was significantly greater at 20% compression (P<0.05). The maximum load and a^*b^* and chroma were all lower for meat aged 14 days.     

Use of digital images to estimate CIE color coordinates of beef

The objective of this study was to evaluate the use of digital images (DI) to estimate CIE L^*a^*b^*, hue angle and chroma of beef, as compared to a colorimeter (CM). Loin samples from 21 steers finished with high-grain diets were displayed under retail-simulated conditions. Color readings were obtained from 63 cores covering the full spectrum of discoloration in beef. CIE L^*, a^*, and b^* were measured with a surface-reflectance CM. Red, green and blue (RGB) values were obtained from DI and sequentially transformed to XYZ and CIE L^*a^*b^* color space. Hue angle and chroma were calculated from a^* and b^* values. Regressions of CM on DI for a^*, hue angle and chroma had R² values of 0.93 and above. Average color difference () between the predicted and the actual CM L^*, a^*, and b^* values for 13 samples that were not included in the regressions was 1.57, below reported thresholds of detection for 50% of observers. Color readings from DI could be used to accurately predict color coordinates measured by CM, especially a^*, hue angle and chroma. Use of digital imaging could become a practical tool to detect changes in beef color and other muscle foods.     

The influence of goat genotype on the production of Capretto and Chevon carcasses. 2. Meat quality

The effect of five goat genotypes, Boer×Angora (BA), Boer×Saanen (BS), Feral×Feral (FF), Saanen x Angora (SA) and Saanen x Feral (SF) on the meat quality of Capretto and Chevon carcasses obtained from 50 buck kids, was assessed. Genotype had an influence on cooking loss and longissimus thoracis muscle colour coordinates (CIE L^*, a^*, b^* values). BS kids from the Capretto group had paler muscle colour compared to other genotypes; pale muscle colour being required for Capretto carcasses. Total pigment concentration, fat colour, shear force values and sensory scores for flavour, tenderness, juiciness and overall acceptability did not differ significantly between genotypes. Muscle colour became darker and fat colour became more yellow with increasing animal age. Tenderness decreased with animal age as indicated by higher shear force values. Age had no significant influence on cooking loss and sensory scores.     

Effect of different stunning systems on meat quality of light lamb

The present study was proposed to compare the effect that different types of stunning (TS) had on the quality of refrigerated meat from light lambs of the Spanish Manchega breed at 24 h and 7 days post-mortem. Lambs were electrically stunned (ESL; n = 10), using CO₂ (GSL; n = 10) or slaughtered without previous stunning (USL; n = 10). Measurements on meat quality were carried out by evaluating pH, colour coordinates (L^*, a^*, b^*), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, no significant differences were found in any of the variables studied. However, at 7 days post-mortem, meat quality was affected by the different TS: pH, CL and DL were lower (P < 0.001) in the USL group and GSL obtained the lowest a^* (redness) and b^* (yellowness) values (P < 0.01) than in the other groups. Ageing of meat affected SF in the ESL group (P < 0.01), although there were no significant differences due to treatments at any of the ageing times.     

Diverse lamb genotypes-2. Meat pH, colour and tenderness

The effect of genotype on meat ultimate pH, colour and tenderness was studied in 3 experiments involving 436 lambs. The lambs were sired by a selection of Texel (T), Poll Dorset (PD), Border Leicester (BL) and Merino (M) rams, crossed with Border Leicester × Merino (BLM) and Merino (M) ewes giving 6 genotypes (T × BLM, PD × BLM, T × M, PD × M, BLM and M × M). In experiment 1, pH data were obtained for 4 muscles (M. Semimembranosus (SM), M. Biceps femoris M. Semitendinosus and M. Longissimius thoracis et lumborum (LL)) from 198 carcasses representing two sexes (104 cryptorchid males, 94 ewes). There were significant differences for pH between genotypes in both sex groups. BL × M and M × M lambs tended to have higher pH values than the other genotypes.

In experiment 2, meat pH, colour using a chromameter, and tenderness data were obtained for 186 lambs representing two sexes (101 cryptorchid males, 85 ewes). There were few significant differences between genotypes for the various meat quality traits amongst the ewes. The PD × BLM ewes had a significantly lower (p < 0.05) pH than the BL × M ewes for the LL and SM muscles.

The BL × M crypt orchids had a higher LL muscle pH (p < 0.05) than the PD × BLM cryptorchids with other genotypes being intermediate. There were no significant differences between the genotypes for muscle shear force values. Within experiment 2, LL samples were taken from an additional 52 cryptorchid carcasses these being from 3 specific Poll Dorset sires (experiment 3). One of these sires (sire 3) was suspected of carrying a gene for increased muscling. Sire had a significant effect (p < 0.05) on shear force values, cooking loss and L^* colour values, but not a^* or b^* colour values or pH. Sire 3 progeny had significantly (p < 0.001) tougher LL muscles than those from the other 2 sires. Sire 3 also had the lowest L^* values, but was intermediate for cooking loss. There was no significant sire effect on LL area at the same carcass weight, but boneless loins from the progeny of Sire 3 were significantly (p < 0.05) heavier.

In a fourth experiment, meat colour was measured at three sites (LL, diaphragm and M. Obliquus externus abdominis) on 86 cryptorchid carcasses 24 hr post-mortem. There was little association between L^*, a^* and b^* values measured at the different sites.     

Effect of season on color of Hanwoo (Korean native cattle) beef

A total of 1278 head of Hanwoo (Korean native cattle) slaughtered over four seasons were used to evaluate the effect of season on color characteristics of beef longissimus dorsi (LD) muscle. CIE L^*, a^*, b^*, C^* values and hue angle were significantly lower (P<0.05) in cattle slaughtered in the winter season. Meat color was darker in the winter than in the spring and autumn seasons. The L^* values among three average daily temperature (T_a) categories were different (P<0.05) in order of: [5 °CT_a<25 °C] > [T_a25 °C] > [T_a<5 °C], indicating that the meat color of cattle slaughtered at T_a<5 °C was darker. The a^*, b^*, C^* values and hue angle were significantly lower (P<0.05) in cattle slaughtered at T_a<5 °C. Season at slaughter is of great importance for meat color. Namely, meat color of Hanwoo beef was influenced by environmental temperature. Overall, cattle slaughtered in the winter season of T_a<5 °C produced beef with more undesirable meat color properties.     

The colour of the adductor muscle as a predictor of pork quality in the loin

The relation between measurements of colour made in the m. adductor (AD) at 45 min or 20 h post mortem and the quality, assessed subjectively in terms of colour and waterholding capacity, of the m. longissimus (LD) in the loin was examined. The study used data from 100 pig carcasses exhibiting a wide range of meat quality from extreme PSE (pale, soft and exudative) to extreme DFD (dark, firm and dry). The subjective assessments were confirmed by objective measures of paleness (reflectance) and waterholding capacity (drip loss in storage) in the LD. Lightness (L^*) measured at 20 h post mortem in the AD was the best potential predictor of loin muscle quality, explaining 59% of the variation in subjective and objective quality measures. Comparable measurements at 45 min post mortem explained between 21% and 44% of the variation. The equation that described the relation between AD Lightness (L^*) and subjectively assessed LD quality was derived. This could be used to transpose the AD L^* values from a population of slaughtered pigs into nominal subjective scores for the LD, allowing the frequency of the five subjective quality groups (extremely DFD, slightly DFD, normal, slightly PSE, and extremely PSE) in the population of carcasses to be defined.     

Chemical, instrumental and sensory characteristics of cooked pork ham

Instrumental, chemical and sensory parameters of cooked pork ham were evaluated. Principal component analysis was carried out on the basis of the instrumental variables related to colour and texture. The four PCs account for almost 94% of the total variance in the data set. The PCA only separated 3 hams with a^* > 10. Hardness was correlated with non-collagen muscle protein (P  0.01), gumminess (P  0.01) and ash (P  0.05). Sensory evaluated tenderness showed positive significant correlation with L^* (P  0.01). The most important colour parameter seems to be a^*, which was negatively correlated with sensory evaluated parameter colour (P  0.01). The PCA performed on all parameters (sensory, chemical and textural) discriminated two groups of hams differing in non-collagen muscle protein content and hardness.     

Development of a computer vision system to measure the color of potato chips

The objective of this research was to design and implement an inexpensive computer vision system for measuring the color of a highly heterogeneous food material not only in shape as well in color such as potato chips in L^*a^*b^* units from RGB images. The system was composed of (i) a digital color camera for acquiring the images in a digital format, (ii) a computer for storage the images, (c) image analysis routines integrated into a software programmed in Matlab that converts the color RGB of the food image into L^*a^*b^* units. In this way the color of potato chips can be calculated in L^*a^*b^* units over representative areas and in a reproducible way. The kinetics of color changes in potato slices during frying at four temperatures was followed using the implemented computer vision system (CVS). Color values in L^*a^*b^* units were recorded at different sampling times during frying at the four oil temperatures using the total color change parameter (ΔE). Chips fried at higher temperatures get darker as expected and showed by the CVS. The implemented computer vision system can be used to study as well foods different from potato chips by selecting their proper settings for image acquisition and digital image processing.     

Effects of age on composition and quality of muscle Longissimus thoracis of the Omani Arabian camel (Camelus dromedaries)

The aim of this study was to determine the effects of age on chemical composition and quality characteristics of the Arabian one-humped camel’s meat. Samples of longissimus thoracis (between the 10th and the 13th rib of the left side) were randomly collected from 21 Omani intact male camels of three different age groups: group 1 (1–3 years), group 2 (3–5 years) and group 3 (6–8 years). Samples were chilled (1–3 °C) for 48 h. Moisture, crude protein, fat and ash were determined on freeze dried ground muscle. Mineral contents were determined using an Inductively coupled plasma emission spectrometer (ICP). Meat quality including ultimate muscle pH, Warner–Bratzler shear force, sarcomere length, myofibrillar fragmentation index, expressed juice, cooking loss percent, and colour L^*, a^*, b^* were measured using standard methods.

The moisture, protein, fat and ash ranged from 64.4% to 76.7%; 18.6% to 25.0%, 1.1% to 10.5% and 1.0% to 1.4% on dry matter basis, respectively. The Ca, Mg, Na, K, P, Cad, Cr, Ni, Pb, Co, Mo, Be and V ranged from, 9.2 to 46.6, 24.7 to 57.3, 104.7 to 257.0, 471.4 to 1053.0, 249.9 to 584.0, 0.005 to 0.024, 0.020 to 0.410, 0.016 to 0.187, 0.010 to 0.299, 0.010 to 0.018, 0.050 to 0.470, 0.005 to 0.030 and 0.013 to 0.141 mg/100 g on dry matter basis, respectively. The percentage of protein decreased and that of fat increased with increasing camel age. The ultimate pH, shear force, sarcomere length, fragmentation index, expressed juice, cooking loss, lightness (L^*), redness (a^*) and yellowness (b^*) ranged from 5.46 to 6.64, 4.25 to 17.82, 0.96 to 2.50, 55.91 to 94.81,19.50 to 33.63, 13.18 to 29.88, 27.86 to 43.21, 10.46 to 22.81, and 4.63 to 10.11, respectively. Muscles of younger camels (group 1) had significantly (P < 0.05) lower shear force value, ultimate pH and higher sarcomere length, fragmentation index, expressed juice, cooking loss, and lightness color (L^*) by 48%, 3.4%, 43%, 25%, 28%, 14%, and 16% than those collected from older camels (group 3), respectively. Values of middle age camels (group 2) camels were in-between. This study confirmed that camel meat is healthy and nutritious as it contains low fat as well as being a good source of minerals. Age is an important factor in determining meat quality and composition.     

烤烟色差参数与其表面细胞形态指标的关系

为分析初烤烟叶色差参数与其表面细胞形态指标的关系,利用色差计、扫描电镜、Photoshop软件测定初烤烟叶10个区位的色差参数及表面细胞形态指标（细胞面积、细胞周长、细胞形状因子、细胞密度）,并对色差参数与细胞形态指标进行Pearson相关性分析和回归分析。结果表明：①对于云烟87 C3F初烤烟叶,明度值L^*及表面细胞密度呈叶基和叶尖高,叶中部低的变化趋势;红度值a^*、黄度值b^*、总色差值ΔE及表面细胞面积、周长、形状因子呈叶基和叶尖低,叶中部高的变化趋势。②L^*值与细胞面积、周长、形状因子显著负线性相关,与细胞密度显著正线性相关;a^*、b^*、ΔE值与细胞面积、周长、形状因子显著正线性相关,与细胞密度显著负线性相关。烟叶色差参数与表面细胞形态指标存在较强的相关性,为应用色差法评价烟叶表面的细胞形态提供了技术依据。     

Meat quality characteristics of springbok (Antidorcas marsupialis). 1: Physical meat attributes as influenced by age, gender and production region

Springbok is the most extensively cropped game species in South Africa. The effects of age (adult, sub-adult, lamb), gender and production region on the physical attributes (pH₂₄, cooking and drip loss, Warner Bratzler shear force and colour) were determined using samples of the M. longissimus dorsi (LD) muscles of 166 springbok. Stressed animals had a higher (P < 0.05) pH₂₄ (6.3 ± 0.07), as observed in the meat originating from the Caledon region. This meat had lower (P < 0.05) cooking loss (27.2 ± 0.62%) and drip loss (1.8 ± 0.08%) values in comparison to meat originating from the other regions. Inverse correlations were noted between pH₂₄ and drip loss (r = −0.26, P < 0.01) and cooking loss (r = −0.42, P < 0.001). Shear force values (kg/1.27 cm diameter) correlated positively (r = 0.25, P < 0.01) with pH₂₄. Age-related effects on tenderness were small in comparison with pH₂₄ effects. CIELab colorimetric values were typical of game meat and venison (L^* < 40, high a^* and low b^* values). It was noted that pH₂₄ correlated negatively (r = −0.51, P < 0.001) and positively (r = 0.33, P < 0.001) with the hue-angle and the chroma value of colour, respectively. Springbok originating from Caledon had a significantly (P < 0.05) higher a^* value, indicating meat to be more red with higher colour saturation.     

The effect of supplementation with expanded sunflower seed on carcass and meat quality of lambs raised on pasture

The use of conventional concentrates in the supplementation of grass-based fed lambs may induce improvements in growth performance and/or carcass quality but may be disadvantageous in fatty acid profile of tissues, with a negative impact in some nutritional indexes. The objective of this trial was to evaluate the effects on growth performance, carcass and meat quality of using unprotected, unsaturated fat as a supplement for grass-fed based lambs. Twenty-four Merino Branco ram lambs raised on pasture, were supplemented with corn whole grain plus sunflower meal or corn whole grain plus expanded sunflower seed, from 20 to 30 kg live weight. The supplement had no effects on growth performance, carcass quality traits, or meat pH, colour estimates (L^*, a^*, b^*), water-holding capacity, shear force and sensorial attributes. However, lambs supplemented with expanded sunflower seed showed higher proportions of cis-9, trans-11 octadecadienoic acid and trans-vaccenic acid in intramuscular and subcutaneous fat, showing that the inclusion of unprotected lipids in lambs diet was effective in preventing the reduction of rumenic acid (C18:2 cis-9, trans-11) that occurs when conventional concentrates are used as a supplement.     

Physicochemical and sensory properties of chicken nuggets with washed mechanically deboned chicken meat: Research note

The effects of different proportions (0%, 10%, 20%, 30%, 40%) of washed mechanically deboned chicken meat (WM) as a substitute for hand deboned chicken meat, on the physicochemical and sensory characteristics of chicken nuggets were evaluated. The addition of WM increased fat content, but it was only significant (P < 0.05) when 40% of WM was added, whereas the protein content was significantly (P < 0.05) reduced as from 20%. Significant differences (P < 0.05) were found in L^*, a^* and b^* values with different proportions of WM, however, these differences were evidently not discerned as shown by the no significant differences (P > 0.05) in ΔE^* color scores. The addition of WM did not affect (P > 0.05) sensory attributes of chicken nuggets. From a technical viewpoint, up to 40% WM could be incorporated into nugget formulation instead of hand deboned chicken meat without affecting sensory attributes of the product. Minor changes in composition were observed but they were probably not detrimental to the product.     

Color evaluation of carbon monoxide treated porcine blood

The stability of liquid porcine blood, treated with carbon monoxide (CO) at different pH values (7.40, 6.70, and 6.00) up to its complete saturation, was studied. Lowering the pH from 7.40 to 6.70 resulted in a decrease in the amount of CO necessary to obtain 100% carboxyhemoglobin. Further pH lowering to 6.00 did not result in additional reduction in the amount of gas. During 4 days of refrigerated storage CO treated liquid blood maintained, at every pH, a more stable and attractive red color than fresh blood, which was a result of an increase (P<0.05) of a^* (redness) and b^* (yellowness) values and no variation (P>0.05) on L^* (lightness) value. Hue (h^*) and chroma (C^*) decreased in the untreated blood but not in the CO-treated blood. The results indicate that blood saturation with CO yields a product having greater potential for use in meat products without compromising its visual appearance.     

The effects of electrical stunning and percussive captive bolt stunning on meat quality of cattle processed by Turkish slaughter procedures

The effects of electrical and percussive captive bolt stunning both on initial and up to 14 days post mortem meat quality of Friesian young bulls were studied. The first group (NS; n=10) were slaughtered without stunning under Turkish slaughter procedure (these animals were slaughtered under conditions acceptable to the appropriate ethics committee) in a modern abattoir. In the second group (ES; n=10) animals were electrically stunned. In the third group (PS; n=10) animals were stunned with percussive captive bolt. Meat quality was assessed by examining muscle glycogen concentration, pH and WHC. Also cooking loss, texture parameters and consumer sensory properties were assessed at 24 h, 4, 7 and 14 days post mortem. Meat colour as L^*, a^*, b^*, C^*, h^* values were evaluated at 0, 48 h, 3, 5, 7, 9 and 14 days post mortem. Pre-slaughter handling affected muscle glycogen concentration (P<0.05). Animals in electrical and percussive captive bolt stunned groups had higher muscle glycogen concentrations compared to animals in the non-stunned group (P<0.05). Although pre-slaughter handling did not affect significantly pH_{24 h} and WHC, differences were significant for cooking loss, colour coordinates and texture parameters at some storage times. For all sensory attributes (odour, flavour, tenderness and overall acceptability) at all ageing periods (24 h, 4, 7 and 14 days) the percussive stunned (PS) group was significantly superior to the non-stunned (NS) group. The electrically-stunned (ES) group also tended to be superior to the NS group although not all differences were statistically significant. These results indicate that percussive captive bolt stunning of cattle improved meat quality compared with cattle electrically stunned using head only tongs and those non stunned under approved Turkish slaughter procedure.     

High voltage electrical stimulation enhances muscle tenderness, increases aging response, and improves muscle color from cabrito carcasses

Our study examined high and low voltage electrical stimulation and postmortem storage as strategies to improve tenderness and lean color in cabrito carcasses. Boer cross (n=60) kids were assigned to either high (550 V), low (20 V), or no electrical stimulation treatments. No differences in muscle temperature were observed between treatments at any time measured. Muscle pH declined fastest in high voltage treated carcasses. High voltage electrical stimulation slightly increased (P<0.05) b^* and a^* in the M. gluteus medius and tended to increase L^* and b^* (P=0.06 and 0.11, respectively) values in the M. longissimus thoracis. Electrical stimulation had no effect on myofibril fragmentation at 1-, 3-, or 14-d postmortem or sarcomere length. High voltage electrical stimulation increased (P<0.05) tenderness at 1- and 3-d postmortem, but not at 14-d postmortem. Aging for 3 d did not affect tenderness regardless of stimulation treatment, but aging time for 14 d improved (P<0.05) tenderness. These data indicate that high voltage electrical stimulation and 14 d aging were effective in improving the tenderness of meat from cabrito carcasses.     

Effect of carbon monoxide in modified atmosphere packaging, storage time and endpoint cooking temperature on the internal color of enhanced pork

The objective of this research was to evaluate the effects of gas atmosphere, refrigerated storage time, and endpoint temperature on internal cooked color of injection-enhanced pork chops. Enhanced chops were packaged in 0.36% CO/20.34% CO₂ (CO-MAP), 80% O₂/20% CO₂ (HO-MAP), or PVC-overwrapped (PVC-OW; controls), stored at 4 °C for 0, 12, 19 or 26 days, displayed for 2 days then cooked to six endpoint temperatures (54, 60, 63, 71, 77, and 82 °C). L^*, a^*, and b^* values, hue angle and chroma were determined on the internal cut surface of cooked chops. Chops packaged in CO-MAP had the highest a^* values; a^* value began increasing on day 14. The lowest hue angles occurred in chops cooked to lower endpoint temperatures. Chops in CO-MAP had lower hue angles and higher chroma than those in HO-MAP and PVC-OW. Above 71 °C, hue angle and chroma increased. Overall, CO-MAP packaged chops stored for longer time periods then cooked to lower endpoint temperatures appeared reddest. HO-MAP packaged chops were less red, did not change over time, and appeared more well done at lower endpoint temperatures than those in other gas atmospheres. CO-MAP packaged chops retained redness even after cooking at 82 °C.     

Color measurement in Lab units from RGB digital images

The superficial appearance and color of food are the first parameters of quality evaluated by consumers, and are thus critical factors for acceptance of the food item by the consumer. Although there are different color spaces, the most used of these in the measuring of color in food is the L^*a^*b^* color space due to the uniform distribution of colors, and because it is very close to human perception of color. In order to carry out a digital image analysis in food, it is necessary to know the color measure of each pixel on the surface of the food item. However, there are at present no commercial L^*a^*b^* color measures in pixels available because the existing commercial colorimeters generally measure small, non-representative areas of a few square centimeters. Given that RGB digital cameras obtain information in pixels, this article presents a computational solution that allows the obtaining of digital images in L^*a^*b^* color units for each pixel of the digital RGB image. This investigation presents five models for the RGB → L^*a^*b^* conversion and these are: linear, quadratic, gamma, direct, and neural network. Additionally, a method is suggested for estimating the parameters of the models based on a minimization of the mean absolute error between the color measurements obtained by the models, and by a commercial colorimeter for uniform and homogenous surfaces. In the evaluation of the performance of the models, the neural network model stands out with an error of only 0.93%. On the basis of the construction of these models, it is possible to find a L^*a^*b^* color measuring system that is appropriate for an accurate, exacting and detailed characterization of a food item, thus improving quality control and providing a highly useful tool for the food industry based on a color digital camera.