The effect of ionising radiation on the colour of leg and breast of poultry meat

The effect of irradiation (0 and 5 kGy) of chicken, goose and turkey breast and leg muscles and subsequent storage at 4°C was studied in relation to colour changes. The colour of the outside surface was measured on the breast on each day of storage for up to 7 days post irradiation and for breast and leg and day 7. The colour of a freshly cut interior surface of both breast and leg was measured after 7 days storage. L* values of control and irradiated chicken, goose and turkey breast muscles changed little during storage post irradiation. The a* values for unirradiated goose breast were significantly higher than irradiated goose breast but declined to values similar to irradiated goose breast after 7 days of storage. The b* values for irradiated turkey breast were significantly higher than unirradiated turkey breast at all times post irradiation treatment. Analysis of variance was performed on the day 7 CIELAB values of breast muscle for the effects of species, surface and irradiation and their interactions. After 7 days storage a* values of poultry breast were higher on the freshly cut surface due to irradiation in all species, with decreases in hue angle due to irradiation. The a* values of leg of all species at 7 day post irradiation was significantly higher in the irradiated treatment than the controls. The results for the turkey leg indicate that this effect may be mainly due to higher a* values of the freshly cut surface. The possible role of carboxy form of the haem pigments as the irradiated pigment form is discussed.     

The use of discriminant analysis for the interpretation of the reflectance spectra of irradiated porcine M. longissimus dorsi

Slices of porcine M. longissimus dorsi were packed in overwrap packs and subjected to irradiation (0 and 5 kGy) and then stored for 7 days at 4°C. Reflectance spectra were measured on the outside surface and a freshly cut surface at 7 days post irradiation. The reflectance spectra were transformed to reflex attenuance, k/s and first and second difference spectra and subjected to discriminant analysis. Using discriminant analysis it was possible to establish a calibration equation to discriminate between the spectra of irradiated and unirradiated pork for both the outside and the inside surface. When the calibration model was used to predict the classification of new samples a 100% correct grouping was obtained for the freshly cut surface, however, for the outside surface the classification ranged from 87 to 100% correct depending on the mathematical transformation of the reflectance spectra. This shows the potential of colour measurements as a possible rapid initial screening test for the identification of irradiated pork. Evaluation of the first difference spectra to identify peak positions showed significant differences in peak positions between irradiated and unirradiated pork. The position of the peaks in the irradiated sample is discussed as lending support to the hypothesis of the carboxyhaem form as the irradiated pigment.     

The effect of ionising radiation on the colour of beef, pork and lamb

The effect of irradiation (0 and 5 kGy) of beef, pork and lamb portions in retail overwrap packs and subsequent storage at 4°C was studied in relation to colour changes. The colour of the exterior surface of beef and pork was measured on the same samples on each day of storage for up to 7 days post irradiation. On day 7 the colour of a freshly cut surface was measured. The colour of both the exterior and a freshly cut surface of lamb, in similar retail overwrap packs was measured at 2, 5 and 7 days, post irradiation, different samples being used on each day of measurement. L* values of irradiated beef increased significantly with storage and a* values for unirradiated samples decreased significantly with storage. For lamb there was a general increase in L* and h(o) values and a decrease in a*, b* and C* values with storage. Analyses of the day 7 data showed statistically significant effects for species on all CIELAB parameters. Irradiation resulted in significantly higher hue angle (h(o)) values and the a*, b* and C* values were significantly higher on the exterior than freshly cut surface. There were a number of statistically significant 2 factor and 3 factor interactions. The role of formation of a carboxyhaem pigment in the colour of irradiated meat is discussed. The problem of interpretation of pigment changes from CIELAB values is highlighted.     

Effect of gamma irradiation on the texture and microstructure of chicken breast meat

This study investigated the textural and microstructural properties of chicken breast meat exposed to gamma irradiation ((60)Cobalt) and stored at 4?°C. Textural properties of the irradiated (n=27) and unirradiated chicken breasts (control) were determined by measuring shear force and cooking loss at day 0 and at 2-day intervals for a 14-day refrigerated storage period. In addition, microstructural changes of the irradiated and unirradiated chicken breasts were compared. Irradiated chicken breasts had more cooking loss and higher (P<0.0001) shear force than unirradiated chicken breasts. Transmission electron microscopy showed significant differences (P<0.0001) in size of myofibril units (sarcomeres) between irradiated and unirradiated breast. Shrinkage in sarcomere width (myofibril diameter) and disruption of myofibrils in irradiated breast meat were also noticed when compared with unirradiated breast meat.     

Color Characteristics of Irradiated Aerobically Packaged Pork, Beef, and Turkey

Color changes in irradiated meat were species-dependent. Irradiated pork and beef became less red as a result of irradiation and display time. The redness values of turkey increased after irradiation but decreased during display time. The yellowness of the irradiated samples, for all species, increased as a result of irradiation and display. Visual evaluation of irradiated pork and beef indicated an increase in brownness, whereas turkey increased in redness as dose increased. The surface color of irradiated pork became less uniform than unirradiated pork. Reflectance spectra indicated that irradiation induced a metmyoglobin-like pigment in pork and beef, whereas the pigment in turkey was unchanged.     

Beef colour evolution as a function of ultimate pH

Colour in CIELAB space was assessed in 31 yearling entire male cattle from their reflectance spectra (400-700 nm) at six different times (0 min, 15 min, 5 h, 48 h, 6 days and 9 days). Cluster analysis applied to all the colour co-ordinates divided the samples into two groups according to their ultimate pH (pHu): pH<6.1 and pH?6.1. pH ranged between 5.17 and 7.10. Colour development in pH?6.1 group was less visually appreciable than in pH<6.1 group. This difference was also observed in the reflectance spectra. The application of discriminant analysis to these groups established that b* and h* CIELAB co-ordinates are the most discriminant variables. Meat pigment evolution was assessed by the spectrophotometric indexes. R (∞)(632)- R (∞)(614); K S (614)- K S (632) and the K S (630)- K S (580) indexes were found to be the most significant to represent the difference between the two groups.     

Colour evaluation of chorizo de Pamplona, a Spanish dry fermented sausage: Comparison between the CIE L(∗)a(∗)b(∗) and the Hunter lab systems with illuminants D65 and C

Objective colour evaluation was determined for 33 samples of “chorizo de Pamplona” using the CIE L^*a^*b^* and the Hunter system with two illuminants (D65 and C). Highly significant differences between the measures obtained with the two illuminants were found for the three colour co-ordinates (L^*a^*b^* and Lab) in both systems. The highest coefficient of variation in b was with the Hunter system and in a was with the CIE L^*a^*b^* system, suggesting that the CIE system is better for separating samples according to yellowness, while the Hunter system is better for separating samples according to redness. Correlations with sensory evaluation were similar for both systems and illuminants, the lowest values being for yellowness.     

Color Characteristics of Irradiated Vacuum-Packaged Pork, Beef, and Turkey

Changes in color of irradiated meat were observed to be species-dependent. Irradiated pork and turkey became redder due to irradiation but irradiated beef a* values decreased and yellowness increased with dose and storage time. The extent of color change was irradiation dose-dependent and was not related to myoglobin concentration. Visual evaluation indicated pork and turkey increased in red ness whereas beef decreased in redness as dose levels increased. Reflectance spectra showed that irradiation induced an oxymyoglobin-like pigment in pork and that both oxymyoglobin and metmyoglobin developed in beef as a result of irradiation.     

Color, Oxidation-Reduction Potential, and Gas Production of Irradiated Meats from Different Animal Species

ABSTRACT: Turkey breasts, pork loins, and beef loins were aerobically or vacuum-packaged and electron beamirradiated at 3 kGy. Irradiation increased the redness of turkey breast regardless of packaging or storage. Irradiation drastically decreased the redness of aerobically packaged beef loin. Irradiated meats produced higher amounts of CO and CH₄ than nonirradiated. The oxidation-reduction potential (ORP) of meats decreased after irradiation, but increased during the storage. Little differences in CO and ORP values among the irradiated meats from different species were detected. This indicated that CO and ORP were not the only factors involved in the color changes of beef loin by irradiation.     

Some physical changes in Bajo Aragón extra virgin olive oil during the frying process

Changes of viscosity, transmittance spectra and colour of Bajo Aragón extra virgin olive oil, during the frying process, were studied, comparing them to the changes that occur during the frying process of high oleic sunflower oil. The studied oil was obtained from Empeltre variety olives. These changes, due to the deterioration of the oil during this process, were monitored by polar compounds measurement. Polar compounds content increased linearly with the frying cycle in both types of oil; however, the increase was faster in high oleic sunflower oil. The olive oil’s transmittance spectra, after the frying process, proved that, not only do the peaks corresponding to the carotenoids and the chlorophyll disappear but also that transformation of the chlorophyll occured. In high oleic sunflower oil spectra there were no changes. L* and b* colour parameters, measured on the CIELAB colour scale, showed the following behaviour: L* values increased for olive oil after frying while the opposite happened for high oleic sunflower oil. In the case of the b* parameter, the result was the same in both cases: when fried, more green and yellow colours appeared. The viscosity of both oils showed a non-linear increase with number of frying operations, which may correspond to a polynomial relationship. Despite their similar contents of oleic acid, olive oil was more stable to oxidation and there were some physical differences between the two types of oil.     

Strawberry juice colour: A study of the quantitative and qualitative pigment composition of juices from 39 genotypes

The juices from 39 strawberry genotypes were analysed for anthocyanin composition and colour characteristics. No single cultivar or breeding line possessed the innate pigment characteristics thought to confer greater colour stability on strawberry juices but the anthocyanin patterns were far more complex than hitherto reported in strawberries. Thirteen different peaks were observed during high-performance liquid chromatography of the juices and tentative identifications are proposed for two previously unidentified strawberry anthocyanins. The occurrence of pelargonidin 3-rutinoside was confirmed. Colour quality measurements derived from CIELAB L*a*b* values are reported for the fresh juices.     

The measurement of hair colour

The colour of the hair of 65 subjects was measured using a Minolta Chromameter model CR200. Readings were taken by holding the unit against the back of the subject's head, and recorded using the L*a*b* system of colour co-ordinates.
All subjects had hair in which yellow and red (rather than blue or green) dominated. The lightness (L*) of all hair fell in the range 17–67, the redness (a*) in the range 0–6 and the yellowness (b*) 0–20. These limits can be seen as effectively outlining the range of colours which can be said to be natural.
The chromameter gave rapid and reproducible results on hair in situ and was easy to use. The method should be of use to those who wish to quantify the effects brought about by bleaching or dyeing formulations.     

Quality characteristics of irradiated chicken breast rolls from broilers fed different levels of conjugated linoleic acid

Dietary conjugated linoleic acid (CLA) treatment reduced color a*- and b*-values of cooked chicken breast rolls. Sensory panels rated the color of cooked chicken rolls with CLA treatments darker than the control. The production of carbon monoxide (CO) in cooked chicken rolls increased dramatically after irradiation and was correlated with the increased redness of cooked chicken rolls after irradiation. Consumer test indicated that the color of cooked chicken rolls after irradiation was preferred to the nonirradiated, but no preference for the color among the three CLA treatments was found. Irradiation greatly increased volatile production and induced a metallic off-flavor in chicken rolls. Sensory evaluation indicated that the hardness of chicken rolls increased and juiciness decreased as the dietary level of CLA increased.     

CHEMICAL AND COLOR CHARACTERISTICS OF SPANISH DRY-CURED HAM AT THE END OF THE AGING PROCESS

Chemical and color (CIELAB) attributes were measured in three muscles of dry-cured hams: Semimembranosus (SM) , Semitendinosus (ST) and Biceps femoris (BF), at the end of the aging step, which represents the last month of the dry-curing process. SM muscles showed the lowest values for all the chemical and color parameters except the a*/b* ratio while the BF muscles had the highest values except for the same a*/b* ratio. Differences were found in the moisture content, salt concentration, water activity, lightness, chroma, and the a*/b* ratio between the three muscles analysed. BF and ST muscles showed no differences for redness, yellowness and hue. Lightness was highly correlated with moisture and water activity values.     

Inhibitory effect of oxalic acid on bacterial spoilage of raw chilled chicken

Oxalic acid was evaluated as a treatment for reducing populations of naturally occurring microorganisms on raw chicken. Raw chicken breasts were dipped in solutions of oxalic acid (0, 0.5, 1.0, 1.5, and 2.0%, wt/vol) for 10, 20, and 30 min, individually packed in oxygen-permeable polyethylene bags, and stored at 4 degrees C. Total plate counts of aerobic bacteria and populations of Pseudomonas spp. and Enterobacteriaceae on breasts were determined before treatment and after storage for 1, 3, 7, 10, and 14 days. The pH and Hunter L, a, and b values of the breast surface were measured. Total plate counts were ca. 1.5 and 4.0 log CFU/g higher on untreated chicken breasts after storage for 7 and 14 days, respectively, than on breasts treated with 0.5% oxalic acid, regardless of dip time. Differences in counts on chicken breasts treated with water and 1.0 to 2.0% of oxalic acid were greater. Populations of Pseudomonas spp. on chicken breasts treated with 0.5 to 2.0% oxalic acid and stored at 4 degrees C for 1 day were less than 2 log CFU/g (detection limit), compared with 5.14 log CFU/g on untreated breasts. Pseudomonas grew on chicken breasts treated with 0.5% oxalic acid to reach counts not exceeding 3.88 log CFU/g after storage for 14 days. Counts on untreated chicken exceeded 8.83 log CFU/g at 14 days. Treatment with oxalic acid caused similar reductions in Enterobacteriaceae counts. Kocuria rhizophila was the predominant bacterium isolated from treated chicken. Other common bacteria included Escherichia coli and Empedobacter brevis. Treatment with oxalic acid caused a slight darkening in color (decreased Hunter L value), retention of redness (increased Hunter a value), and increase in yellowness (increased Hunter b value). Oxalic acid has potential for use as a sanitizer to reduce populations of spoilage microorganisms naturally occurring on raw chicken, thereby extending chicken shelf life.     

Colour changes during manufacture of Galician chorizo sausage

 Galician chorizo sausage is a smoked-meat product containing chilli pepper. This study investigated changes in its colour (CIE colour coordinates L*, a* and b*, together with redness index, hue, chroma and perceived colour) during the curing process. Samples were obtained from three manufacturers (A, B and C) whose smoking and curing procedures differ markedly. Most of the colour measurement showed clear changes during curing. All measurement except external L* varied significantly among samples obtained from the different manufacturers. Pairwise comparisons indicated that in most cases there were significant differences between samples from manufacturer A (who smokes the product for only 6 h) and manufacturers B and C (who smoke the product for a longer period), but not between samples from manufacturers B and C. The pH, water activity and moisture content were also monitored; again, these variables differed significantly between A and B and between A and C, but not between B and C. Received: 8 October 1997 / Revised version: 19 January 1998     

Assessment of relative content of myoglobin, oxymyoglobin and metmyoglobin at the surface of beef

A method of calculating the relative content of myoglobin, metmyoglobin and oxymyoglobin at the surface of beef is described. It is based on measurements of reflex attenuance of incident light at the isobestic points 572, 525, 473 and 730 nm. The latter value corresponds to the achromatic attenuance of light at the meat surface and can be used as an objective measure of its lightness. It was shown that the colour image of the meat surface, and the relative amounts of these three myoglobin derivatives, are influenced by the opacity of the surface layer. A variability in the light diffusing properties of the meat surface may be considered to be the primary factor in creating differences of colour perception of meat derived from animals of the same species and of the same approximate age.     

Colour changes during manufacture of Galician chorizo sausage

 Galician chorizo sausage is a smoked-meat product containing chilli pepper. This study investigated changes in its colour (CIE colour coordinates L*, a* and b*, together with redness index, hue, chroma and perceived colour) during the curing process. Samples were obtained from three manufacturers (A, B and C) whose smoking and curing procedures differ markedly. Most of the colour measurement showed clear changes during curing. All measurement except external L* varied significantly among samples obtained from the different manufacturers. Pairwise comparisons indicated that in most cases there were significant differences between samples from manufacturer A (who smokes the product for only 6 h) and manufacturers B and C (who smoke the product for a longer period), but not between samples from manufacturers B and C. The pH, water activity and moisture content were also monitored; again, these variables differed significantly between A and B and between A and C, but not between B and C. Received: 8 October 1997 / Revised version: 19 January 1998     

Effect of the addition of corn flour and colorants on the colour of fried, battered squid rings

The effect that the addition of corn flour and colorants to batter doughs has on the final colour of fried squid rings was studied. As the quantity of corn flour increased, the values of the parameters a* (redness), YI (yellowness index) and (E* (total colour difference) increased. The samples that had been prefried and frozen before final frying showed a more brownish colour, probably due to dehydration effects. The addition of tartrazine and riboflavin to the batter dough in order to give initial colour to the frozen, prefried product produced a slight increase in the values of all the colour parameters studied in the final fried products.