Discoloration of Fresh Pork as Related to Muscle and Display Conditions

Pale, soft, exudative (PSE), normal, and dark, firm, dry (DFD) pork was held 7 days at 4°C under light or dark then color was evaluated instrumentally and visually. Change in reflectance (R630-R580) was used to estimate color changes due to oxymyoglobin. PSE pork was lighter (high L*) than normal and DFD pork, but did not change over time. An increase in a* and R630-R580 occurred the first day for normal and DFD, but not for PSE samples. A subsequent increase in hue angle and decrease in R630-R580 (loss of redness) occurred in PSE and normal, but not in DFD samples. Changes in hue angle and R630-R580 were more rapid in PSE than in normal samples. Light exposure accelerated all changes except L*. Visual redness inversely correlated with L* value.     

RELATIONSHIP BETWEEN INSTRUMENTAL AND VISUAL COLOR IN A RAW, FRESH BEEF AND CHICKEN MODEL SYSTEM

A range of meat redness was created by mixing fresh, chilled ground chicken breast and ground beef in predetermined ratios. Samples were scored for visual redness under halogen (incandescent) and cool white fluorescent lighting. Instrumental color characteristics (L*, a*, b*, hue angle, chroma; illuminants A and F) and red color contributed by oxymyoglobin (percentage reflectance at 630 nm versus 580 nm) were determined. Correlation coefficients were determined between visual and instrumental evaluations. The a*, b*, and ΔR (630–580) were highly correlated to visual redness (halogen light: r = 0.99, -0.99, and 0.96, respectively; cool white fluorescent light: 0.98, -0.98, and 0.96, respectively). Regression analysis was conducted to develop equations to predict visual redness using instrumental color measures. In the 20% to 85% beef range, the regression curves were principally linear although the overall relationships (0–100% beef range) were cubic. Among the instrumental color parameters, a*, hue angle, and ΔR (630–580) could be used to predict visual redness for this model system.     

TOCOPHEROL EFFECTS ON FROZEN GROUND PORK COLOR

To assess the effects of α-tocopherol addition on lipid and pigment oxidation of ground pork, 10, 100 or 1000 ppm was added directly in a food grade carrier (2% medium chain triglyceride oil) then pork was overwrapped with polyvinyl-chloride (PVC) film and frozen (-34C) for seven months. Storage time increased extracted deoxymyoglobin percentage, metmyoglobin percentage determined by reflectance spectrophotometry, TBARS, hue angle, and pH, and decreased extracted oxymyoglobin percentage, L*, a* and b* values, and instrumental red color (% reflectance at 630 nm - % reflectance at 580 nm). Extracted metmyoglobin percentage increased through 140 days then decreased through 196 days. Alpha tocopherol increased deoxymyoglobin and decreased oxymyoglobin (extracted) expressed as a percentage of the total pigment, when compared with control samples. Metmyoglobin percentage (reflectance was highest in 10 ppm samples and lowest in 1000 ppm samples. Hue angle and total color were best correlated with other measures of red color.     

CHEMICAL AND COLOR CHARACTERISTICS OF "LOMO EMBUCHADO" DURING SALTING SEASONING

"Lomo embuchado" is a traditional Spanish dry-cured meat product with two principal stages (salting-seasoning and dry-maturation) in its process. The evolution of chemical (moisture, nitrite, pH and lactic acid) and physical parameters: (CIELAB color space, chroma and hue, a*/b*, ΔE* and reflectance ratios R560/R500, R650/R570 and R630/RS80), during the salting-seasoning stage were measured. Three zones in the salted-seasoned loins were identified, and all parameters in each zone were analyzed. ANOVA and regression analyses were conducted. Moisture, pH and residual nitrite decreased with time (P<0.01), and lactic acid increased (P<0.05). Only moisture showed differences between zones (P<0.05). Color parameters changed during the salting-seasoning stage. Lightness (P<0.01), redness (only during the first 24 h (P<0.05)), and a*/b* ratio (P<0.01) increased. Yellowness (P<0.01), hue (P<0.01) and chroma (P<0.05) decreased during the process. The only parameter that was not affected by time and zone was reflectance ratio R630/R580 (P>0.05). Moisture and reflectance ratio R560/R500 were affected by zones (PCO.05). An excellent cured color was obtained during salting and seasoning.     

Effect of high pressure treatment on the color of fresh and processed meats: A review

High pressure (HP) treatment often results in discoloration of beef, lamb, pork, and poultry. The degree of color changes depends on the physical and chemical state of the meat, especially myoglobin, and the atmospheric conditions during and after pressurization. A decreased redness is attributed to a large degree to the oxidation of the bright red oxymyoglobin or the purplish deoxymyoglobin into the brownish metmyoglobin, as well as to the denaturation of myoglobin. Surely, the high myoglobin content makes beef more exposed to this discoloration compared to the white chicken meat. In addition, HP treatment causes denaturation of myofibrillar proteins followed by aggregation, consequently, changing the surface reflectance and increasing lightness. Other intrinsic and extrinsic factors may affect the pressure-induced color changes positively or negatively. In this review, the pressure-induced color changes in meat are discussed in relation to modification of the myoglobin molecule, changes in the meat microstructure, and the impact of the presence of different chemical compounds and physical conditions during processing.     

Effects of Endpoint Temperature on the Internal Color of Pork Patties of Different Myoglobin Form, Initial Cooking State, and Quality

ABSTRACT: :The effects of several parameters on the development of internal cooked color in ground pork were evaluated. Patties were made from normal or pale, soft, and exudative (PSE) pork and the pigment converted to either oxymyoglobin or deoxymyoglobin. Patties from these 4 treatment combinations were cooked from the frozen or thawed states to 5 endpoint temperatures. PSE patties and those containing oxymyoglobin exhibited premature browning as they appeared cooked and were more (P < 0.05) tan at lower temperatures than normal patties or those with deoxymyoglobin which had a slightly pink internal color at 71 °C. Percentage myoglobin denaturation increased as cooking temperatures increased (P < 0.05) for both types of meat and was greater in patties containing deoxymyoglobin than in those with oxymyoglobin. Patties cooked frozen had lower a* values (P < 0.05) than thawed patties at every endpoint temperature.     

Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs

The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed Hampshire, Swedish Landrace and Swedish Yorkshire pigs was studied. The contribution of the pigment content, the myoglobin forms deoxymyoglobin (Mb), oxymyoglobin (MbO) and metmyoglobin (MetMb) and the internal reflectance to the colour of pork of normal meat quality was evaluated using partial least squares regression (PLS). The colour of LD and BF from the Hampshire breed was more red and yellow and more saturated than the colour of the same muscles from the Swedish Landrace and the Swedish Yorkshire breeds. Furthermore, BF from Hampshire was darker than BF from the other two breeds. These differences in colour were related to the lower pH in Hampshire, resulting in more blooming and in higher internal reflectance, and to the higher pigment content. The colour of BF was darker and more red than the colour of LD within each breed. No colour difference was found between gilts and castrates within each breed. Most of the variation (86-90%) in lightness (L* value), redness (a* value) and yellowness (b* value), chroma (saturation) and hue angle of pork of normal meat quality was explained by the pigment content, myoglobin forms and internal reflectance. The L* value, a* value, chroma and hue angle were influenced by both the pigment content and by the myoglobin forms to almost the same extent, while the internal reflectance was of no significance to these colour parameters. The b* value was influenced most by the myoglobin forms, less by the internal reflectance and almost not at all by the pigment content.     

Effect of Packaging on Color and Physical Characteristics of Ground Pork in Long-term Frozen Storage

Ground pork, 30% fat, was packaged in 454g units in Cryovac bags heat scaled under vacuum (V), Saran Wrap? (S), aluminum foil (A), Saran? overwrapped with aluminum foil (SA), and polyvinyl chloride (PVC) and frozen 13, 26, or 39 wk at ? 17°C. TBA values increased over time regardless of packaging. Those materials that excluded oxygen delayed lipid oxidation longest. Red color (CIE a* value and % reflectance difference at 630 and 580 nm) decreased over time; this was greater on exterior than interior of the meat block. Materials that excluded oxygen prevented loss of red color during the first 26 wk storage. Changes in redness and TBA appeared unrelated to pH. Changes in L* and b* values did not appear related to packaging treatment or storage time.     

A second mutant allele (V199I) at the PRKAG3 (RN) locus-II. Effect on colour characteristics of pork loin

Three alleles at the PRKAG3 (RN) locus that influence the glycogen content of pork were found to be segregating in Hampshire×Landrace crossbred pigs, RN(-), rn(+) as well as second mutant allele V 199I (here denoted rn*). The effect of these three alleles on ultimate pH, pigment content, internal reflectance (FOP), surface colour measured by tristimulus colorimetry (L*, a*, b*) and fractions of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) of pork loin was studied. Moreover, the effect of sex, entire male versus female pigs, on these traits was also analysed. The three PRKAG3 alleles affected ultimate pH, internal reflectance, colour and distribution of myoglobin derivatives of pork loin, while the pigment content was not influenced. Ultimate pH values of loins from the three genotypes were found to be in the order RN(-)/- genotypes rn(+)/rn(+) genotype=rn(+)/rn* genotype=rn*/rn* genotype. The RN(-) allele was dominant resulting in higher redness (a* value) and yellowness (b* value), while the rn* allele tended to result in lower redness and yellowness compared with the rn* allele. The RN(-) allele was dominant over the rn* allele in lightness (L* value) giving a lighter colour. Surface colour differences were mainly explained by differences in the distribution of the myoglobin derivatives. Finally, surface lightness was higher and pigment content, redness and fraction of MbO(2) lower in loin from entire males compared with females.     

Factors affecting the colour of lamb meat from the longissimus muscle during display: The influence of muscle weight and muscle oxidative capacity

Spectrophotometric measures were used to determine the redness:browness (R630/R580) of 4238 lamb longissimus muscle after 3 days under simulated display. The results were analysed using linear mixed effects models. Environmental factors represented by effects such as kill group and site of production produced the greatest variation of up to 2.76 units in R630/R580. Isocitrate dehydrogenase activity, reflecting muscle oxidative capacity, reduced R630/R580 by 0.5 units. Selection for high muscling sires increased R630/R580 by 0.27 units, likely due to changes in muscle oxidative capacity. Lamb carcass weight also increased R630/R580 by 0.5 units. Analysis of genotypic factors influencing lamb size and growth rate such as sire type and dam breed further supported that increased growth rate improves meat R630/R580. Our findings suggest that breeding for increased growth rate and increased muscle weight could result in Australian lamb meat retaining its red colour for extended periods whilst on display.     

Analysis of meat pigments with tissue spectrophotometer TS-200

The colour of meat and rice flour pastes containing known amounts of myoglobin and the colour of intact beef and pork samples were analyzed with tissue spectrophotometer TS-200. The differences in the spectra of myoglobin among three types of derivatives were successfully distinguished with this instrument. In addition, there is a close relationship between I_HB value, a parameter for estimating the content of pigments in animal tissues, and myoglobin content in model systems (rice flour paste and meat paste). Especially, the I_HB value is proportional to myoglobin content in intact beef and pork meat whose myoglobin is mostly in the state of oxymyoglobin and/or deoxymyoglobin: Y = 208·26 x + 6·72, where y is the I_HB value, x is the myoglobin content (%) and R = 0·94.     

Influence of dietary inclusion level of manganese on pork quality during retail display

Boneless pork loins (n = 112) were used to test the influence of dietary manganese (Mn) inclusion level on pork quality traits during retail display. Crossbred barrows and gilts were fed diets formulated with 0, 20, 40, 80, 160, or 320 ppm Mn from Availa^®Mn (AvMn; a Mn–amino acid complex) from 23.8 to 106.8 kg live weight. At approximately 48 h postmortem, boneless pork loins were fabricated into longissimus thoracis et lumborum (LM) chops, which were subsequently placed in open-topped, coffin-chest display cases (2.6 °C) under continuous warm-white, fluorescent lighting (1600 lx) for 7 days. Dietary Mn level had no effect on LM pH (P = 0.47), purge volume (P = 0.60) and loss (P = 0.53), or moisture loss (P = 0.95) during retail display. Chops from pigs fed 80 ppm Mn received higher (P < 0.05) American and Japanese color scores than pigs fed 0 and 40 ppm Mn. Even though the LM from pigs fed 80, 160, and 320 ppm Mn tended to be darker (lower L^* values; P = 0.07) than chops from pigs fed 40 ppm Mn, a^* (redness) and b^* (yellowness) values, as well as hue angle and chroma, were not (P  0.19) affected by dietary Mn. On days 0 and 1, the reflectance ratio of 630 nm/580 nm was similar (P > 0.05) among dietary Mn supplementation levels; yet, by day 4 of retail display, chops from pigs fed 80 ppm Mn had higher (P < 0.05) reflectance ratios than chops from pigs fed 0, 20, 40, and 160 ppm, whereas LM chops from pigs fed 40 ppm Mn had lower (P < 0.05) reflectance ratios than all other dietary treatments on day 7 (Mn supplementation level × display day; P = 0.04). Although TBARS were greater (P < 0.001) on day 7 than 0 of retail display, TBARS values did not (P = 0.43) differ among dietary Mn levels. Results indicate that supplementing swine diets with 80 ppm Mn may improve pork color during retail display without increasing the likelihood of lipid oxidation.     

萨拉米模拟发酵过程中猪肉肌红蛋白存在形式影响规律研究

为实现萨拉米色泽的精确控制技术,用480～640nm的扫描图谱分析了萨拉米模拟发酵过程中温度、pH值、亚硝酸钠添加量、异抗坏血酸钠添加量对猪肉肌红蛋白存在形式的影响规律.结果表明,在4h以内,随着发酵温度的上升,氧合肌红蛋白含量显著减少;随着pH值的降低,高铁肌红蛋白显著减少,氧合肌红蛋白含量显著增多,脱氧肌红蛋白显著减少;在同一时间段,随着亚硝酸钠添加量的增加,高铁肌红蛋白显著增加,氧合肌红蛋白显著减少;随着异抗坏血酸钠添加量的增加,肌红蛋白3种形式的比例均无显著变化.     

SODIUM LACTATE/SODIUM POLYPHOSPHATE EFFECTS ON OXIDATION IN PRECOOKED FROZEN PORK PATTIES

The objective of this study was to evaluate sodium lactate (SL; 0, 1, 2 or 3%) and sodium polyphosphate (SP; 0, 0.1, 0.2 or 0.3%) effects on lipid oxidation and color characteristics of precooked pork patties during frozen storage. Ground pork was mixed with SL and/or SP, stuffed, frozen, sliced and cooked from the frozen state, packaged and held frozen for 14 weeks. Samples containing SP had lower TBARS, regardless of SL content. SL decreased pH, a* and b* values and red color (R630–R580). L* value, hue angle, pork flavor, saltiness, and juiciness increased as SL increased. A moderate correlation occurred between SL and TBARS. SP decreased hue angle, cook loss, and rancid flavor and increased pH, b* value, pork flavor, saltiness, and juiciness. Storage time decreased a* value, red color and juiciness, while saltiness, alkalinity, and rancid flavor scores increased. Based on both physical and sensory characteristics, optimum combinations appear to be 3% SL and 0.2–0.3% SP.     

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.     

The impact of lactic acid concentration and sodium chloride on pH, water-holding capacity, and cooked color of injection-enhanced dark-cutting beef

The objectives of this study were to evaluate the effect of enhancement with 0.5%, 1.0%, 1.5%, or 2.0% lactic acid (LA), with or without 0.5% salt (NaCl), on pH, water-holding capacity, and resultant cooked color of dark-cutting (DC) beef. The pH of DC sections treated with LA decreased (P < 0.05), whereas water-holding capacity (WHC) increased (P < 0.05) with increasing concentrations of LA. Sensory panelists noted an increase (P < 0.05) in the degree of doneness (less pink internal color), whereas, a^* and chroma values were lower (P < 0.05), and hue angles were greater (P < 0.05), indicating the internal color of LA-treated DC sections was less red and appeared more well-done. Also, 630:580 nm reflectance ratios were similar (P > 0.05) among DC steaks treated with 0.5% and 1.0% LA and normal pH (NDC) steaks, likely caused by an increase (P < 0.05) in myoglobin denaturation in LA-enhanced DC steaks. These results indicate that the use of LA can reduce postmortem muscle pH and alter the cooked color of DC beef, ultimately resulting in a deletion of the persistent pinking condition.     

Mechanisms of Pink Color Formation in Irradiated Precooked Turkey Breast Meat

ABSTRACT: Precooked turkey breast meat was aerobically packaged or vacuum-packaged and irradiated at 0, 2.5, or 5.0 kGy. CIE color, reflectance, oxidation-reduction potential (ORP), gas production, and lipid oxidation were determined at 0, 7, and 14 d. Irradiation increased redness of vacuum-packaged meat, and the redness was distinct and stable under vacuum. Irradiation decreased ORP and produced carbon monoxide (CO). This indicated that the pink color was caused by the heme pigment-CO complex formation. The reflectance of meat and the absorption spectra of myoglobin solution supported the assumption that denatured CO-myoglobin is the pigment in irradiated precooked turkey breast.     

Electrical Stimulation and Hot Boning: Color Stability of Ground Beef in a Model System

Lean and fat trim of flanks from electrically stimulated, hot boned (ESHB) or conventionally chilled (CC) beef sides were used to fabricate six batches of ground beef with three levels of fat (ESHB 10, 15, or 20% fat; CC 10, 15, or 20% fat). Raw samples were evaluated for color stability in a model system, pH, and microbial counts. After 4 hr exposure to radiant energy, percentage reflectance for 630 – 580 nm, HunterLab spectrophotometer a values, HunterLab a/b ratios, and visual color scores indicated the ESHB samples were more (P < 0.05) sensitive to metmyoglobin formation, had slightly lower pH, and had lower microbial counts than did CC samples.     

Effect of Co2 or vacuum packaging on normal and high pH meat shelf-life

In order to extend meat shelf-life, normal-pH and high-pH beef steaks were packaged under vacuum or in 100% C 0 2 atmosphere. Microbiological, colour (L*, a*, b*)
and reflectance (R630-R580 values) characteristics were measured.
After packaging under vacuum, Enterobacteriaceae, Brochothrix thermosphacta and Pseudomonas numbers were 10- to 100-fold greater on high-pH meat than on
normal-pH meat.
Packaging under C 0 2 improved the shelf-life of meat, particularly that of high-pH meat up to 42 days. For both high- and normal-pH meats, the bacterial flora was
composed only of lactic acid bacteria. Normal-pH meat in C 0 2 atmosphere and vacuum packaging had a purple colour. After C02-pack opening the meat colour
became bright red and R630- R580 measurements were high, whereas after opening of vacuum packaging R630-R580 decreased rapidly with increasing aerobic exposure.
High-pH meat became paler with increasing storage time in C02. Simultaneously R630-R580 values increased and the pH fell. In addition it lost less exudate and
oxidized less in air than the normal-pH meat under the same conditions.     

EFFECTS OF VARIOUS FRESH MEAT STORAGE METHODS ON THE COLOR OF COOKED GROUND PORK

The effects of microbial growth in raw materials on cooked pork color were investigated. In two trials with sow meat held aerobically at 2C for 3 weeks, microbial load reached spoilage levels (10⁷ cfu/g), pH increased to 6.46, and samples cooked to 71C had red exudate, shown by absorption spectroscopy to contain myoglobin and cytochrome c. Samples cooked to 82C also received high panel ratings for red color, due to red, flocculent precipitate in the exudate, but undenatured myoglobin levels were low. In sow meat held frozen or vacuum-packaged at 2C, pH after 3 weeks was 6.03 and 6.18, and plate counts were 10⁴ and 10⁷, respectively, but exudates after cooking were much less red. In five trials with fresh pork legs, total plate counts also reached 10⁷ cfu/g by 3 weeks storage, and pH increased to 6.37, but cooked samples were not red. Higher myoglobin levels in sow meat probably accounted for the red color and level of undenatured myoglobin remaining after cooking of high pH, spoiled samples.