Characterization of the Residual Pink Color in Cooked Turkey Breast and Pork Loin

The residual redness was characterized in well cooked meat from turkey breast and pork loin. A simple method of scanning thin slices by transmission spectrophotometry was used to evaluate the meat pigments in situ. Absorption bands at 414, 520, and 550 nm of the spectra obtained from cooked meat led to the conclusion that residual pink color was caused by cytochrome c. The method was further modified to study the effect of air contact on meat color after cooking. Other pigments were spontaneously oxidized as soon as meat surface was exposed to air. The concentrations of hemoproteins in turkey and pork were determined and found to be related to cooked meat color.     

Influence of Phospholipids on the Development of Oxidized Off Flavors in Cooked Turkey Rolls

Total lipid and phospholipid (PL) fractions and their fatty acid profiles were analyzed from the interior and exterior portions of cooked turkey breast rolls. Compositional changes during refrigeration were related to oxidative degradation as measured by the TBA test. Breast tissues contained 2% lipid which remained constant over storage. The PLs constituted 0.7% of the meat and only those PLs in the exterior portion degraded during storage. TBA values increased in both roll portions with a concomitant reduction in polyunsaturated fatty acids (PUFAs) having four or more double bonds. These findings suggested that PUFAs were associated with oxidized off-flavors in cooked turkey rolls. Phosphatidylcholine was present in the highest concentration and underwent the greatest oxidative deterioration.     

Flavor Components and Factors Associated with the Development of Off-Flavors in Cooked Turkey Rolls

The influence of storage and roll position on the development of warmed-over flavors in cooked turkey rolls was investigated. Following cooking the rolls were refrigerated for 0, 2 and 4 days and analyzed by headspace gas chromatography/mass spectrometry, TBA numbers, flavor profile analysis, and sensory category scaling. TBA numbers increased significantly by 52 and 165% after 4 days in the interior and exterior portions of the rolls, respectively, and were correlated with flavor deteriorations. Thirty-two compounds were identified, 30 of which are potential products of fatty acid autoxidation. In general, their concentrations were influenced by storage and roll position and correlated to TBA numbers and off-odor and flavor notes.     

Spectra of Pigments Responsible for Pink Color in Pork Roasts Cooked to 65 or 82°C

Undenatured oxymyoglobin and deoxymyoglobin were the pigments responsible for pink color in pork roasts cooked to 65°C. Roasts cooked to 82°C had gray internal color after cooking, but panelists noted development of pink internal color after refrigerated storage. Reflectance spectra of pink slices from roasts cooked to 82°C, then stored for 12 days at 2°C, were characteristic of denatured globin hemo-chromes or related nonnitrosyl hemochromes.     

The Cause of Discoloration of Hard Cooked Egg Rolls

SUMMARY: The brownish discoloration of coagulated albumen in hard cooked egg rolls by ultraviolet (UV) radiation involves the splitting and conformation changes of the peptide chain as suggested by an increase in the amount of nonprotein nitrogen and aromatic amino acids. The presence of water was essential in the development of discoloration, indicating that hydroperoxides and/or peroxides produced from water by the action of UV radiation could cause oxidation of tryptophan. The oxidative type of reaction was confirmed by the development of a similar brown color when coagulated albumen was heated in the presence of oxidizing agents. The discoloration could be prevented by reducing agents, however, once the color has been developed the agents become ineffective. Therefore, a two step mechanism was suggested for the UV discoloration of coagulated albumen: first, the peptide chain is hydrolyzed resulting in an increase in the amount of tryptophan available; second, the tryptophan molecule is oxidized producing a brown color.     

Variations in Internal Color of Cooked Beef Patties

Seventeen commercially prepared patty formulations were cooked to internal temperature 71°C. Pink cooked color occurred in eight of the products and was due to incomplete denaturation of myoglobin. Although there was some relation between pH and cooked color, other factors seemed to be involved. When products were re-analyzed after 1 yr storage at -27°C, sixteen products were red/pink when cooked to 71°C. This increase in redness after frozen storage could not be explained. Cooking to internal temperatures between 81 and 87°C was necessary for complete disappearance of red/pink color. Premature browning, where a product looks well-done at temperatures lower than 71°C, occurred in one formulation.     

Pink Color Development in Turkey Meat as Affected by Nicotinamide, Cooking Temperature, Chilling Rate, and Storage Time

Consumers associate pink color in cooked turkey with undercooking. “Pinking” has been attributed to several factors, but remains a problem in the poultry industry. Effects of temperature, chilling rate, and storage time were investigated relative to pink color intensity of turkey meat cooked in the presence of 2% nicotinamide. As final cook temperature increased, sensory pinkness increased as did CIE a* values. Slower chilling rate resulted in higher CIE a* values and lower CIE b* values. Increased storage time generally increased CIE a* values and decreased b* values while CIE L* values were not affected.     

Lipid Oxidation in Cooked Turkey as Affected by Added Antioxidant Enzymes

Catalase (CAT) and glutathione peroxidase (GSH-Px) were added to turkey which had been cooked (80°C) to provide minimal activity of both enzymes, to determine their effects in development of lipid oxidation. CAT (100–500 U/g muscle) decreased the formation of thiobarbituric acid reactive substances (TBARS) 4–28% during 2 days of storage. GSH-Px (4.0 U/g muscle) decreased TBARS 8–11%. CAT (170 U/g muscle) and GSH-Px (1.3 U/g muscle) in combination decreased TBARS formation 7–14%. Reduced glutathione concentrations in the turkey were unaffected by cooking. These data suggest that heat inactivation of CAT and GSH-Px was not the only factor involved in heat-induced lipid oxidation reactions in turkey thigh muscle.     

Stability of Vacuum Cook-in-Bag Turkey Breast Rolls during Refrigerated Storage

Vacuum packaged, uncured turkey breast rolls prepared commercially in two plants by the cook-in-bag process were evaluated for physicochemical and microbiological stability during 87 days storage at 4°C. Total product weight, drained weight, pH, nonprotein nitrogen and tensile strength of turkey were not significantly affected by storage. Shear strength decreased while thiobarbituric acid numbers increased slightly in the turkey rolls. Hunter a_L color values of turkey slices varied inconsistently during storage. No psychrotrophic aerobic colony forming units were detected. Mesophilic anaerobe counts were higher in the meat core than on the surface, thus precautions should be taken to insure vacuum cook-in-bag poultry products are not temperature abused.     

Oxygen Availability Affects Prooxidant Catalyzed Lipid Oxidation of Cooked Turkey Patties

The catalytic effect of free ionic iron, hemoglobin and/or NaCI, and the effect of total lipid, class of lipid, and fatty acid composition on lipid oxidation of precooked refrigerated meat patties were highly significant only when oxygen was freely accessible to the patties during storage. With limited oxygen contact (cold vacuum-packaging) after cooking, the 2-thiobarbituric acid reactive substances (TBARS) values of patties were much lower than the values for patties with free oxygen contact (loose packaging) and did not increase substantially during storage. However, the TBARS values of cold packaged patties were higher (P<0.05) than those of hot packaged patties which had almost no oxygen contact after cooking. Elimination of oxygen during storage (hot or cold vacuum-packaging after cooking) resulted in prooxidants, fat content, fatty acid composition or the class of lipids having no effect on lipid oxidation.     

Role of Muscle Fibers in Contributing Firmness of Cooked Fish

Cooked muscle tissue of five fish species were observed by optical and scanning electron micrography. Species with firm texture had thin muscle fibers with considerable heat-coagulating material between them; species having soft texture had thick muscle fibers with little heat-coagulating material. When the cooked muscles were compressed by a Texturometer, muscle fibers of the species having firm texture slid or shifted over one another to a lesser extent than those of species with soft texture. The heat-coagulating material seemed to obstruct the displacement of the fibers. The diameter and mobility of muscle fibers are determinative of firmness of fish muscle tissue.     

Endpoint Temperature, Internal Cooked Color, and Expressible Juice Color Relationships in Ground Beef Patties

Ground beef patties from A- and E-maturity carcasses and imported trimmings were cooked to 55 to 77°C. Internal patty color became less red as endpoint temperature increased. However, some patties cooked to lower temperatures turned brown prematurely. Visual evaluation of internal patty color was not an accurate indicator of patty doneness. Raw material source had little effect on internal patty color. Expressible juices from imported trimmings were less red than those from A-and E-maturity carcasses. Expressible juice became less red and more yellow with increasing endpoint temperature; however, expressible juice never “ran clear.” A more appropriate guideline would be “cook until juices lack redness.”     

Sensory Detection and Population Thresholds for Sodium Tripolyphosphate in Cooked Ground Turkey Patties

Sodium tripolyphosphate (STP) at levels of 0.1, 0.2, 0.3, 0.4, and 0.5% by weight was added to ground turkey meat to determine if a flavor difference could be detected when STP was present. Detection thresholds for STP in ground turkey meat were determined for 30 female respondents. Two population thresholds were determined using information from the detection thresholds. Two-thirds of the respondents detected a difference between samples with no STP and those with 0.5% STP or less. STP added at less than 0.3% was undetected by more than 50% of the tested population.     

Sensory Characteristics of Postmortem Papain Injected Turkey Cooked Conventionally or by Microwaves

Sensory characteristics of papain-injected turkey breast muscle cooked in microwave or conventional ovens were evaluated by a panel. Off-flavor and mealiness developed in intact turkey muscles injected with papain, but those levels of papain were not sufficient to tenderize the muscle. Samples cooked in conventional ovens had greater roast turkey flavor and were less juicy than samples cooked in microwave ovens.     

Myoglobin Oxidative State Affects Internal Cooked Color Development in Ground Beef Patties

Ground beef patties known to develop a normal (NRM) or premature brown (PMB) color when cooked to 55°C received no treatment or were reduced or oxidized before cooking. Internal raw appearances were red/ purplish-red for NRM, purplish-red/red for reduced, and brown for PMB and oxidized groups. Cooked colors of NRM-no treatment and reduced, and PMB-reduced were more red (P <0.05) than those of NRM-oxidized and PMB-no treatment and oxidized. Cooked colors of PMB-reduced and NRM-no treatment were similar (P>0.05), and those of NRM-oxidized and PMB-no treatment were similar (P>0.05). Oxidized pigment produced a PMB color, whereas reducing conditions produced NRM cooked color.     

Thermal Inactivation of Escherichia coli O157:H7 in Cooked Turkey Products

Survival of Escherichia coli O157:H7 when heated in commercial-type turkey products was determined. Thermal death times (TDT) were determined at 52–60°C in ground turkey with no additives, 3% fat; ground turkey with no additives, 11% fat; turkey ham batter, 11% fat; turkey frank batter, 17% fat; and turkey sausage batter, 31% fat. Mean D₅₂-values ranged from 44.9 to 116 min; D₅₅-values from 6.63 to 39.4 min; D₅₇-values from 2.20 to 11.7 min; D₆₀-values from 0.68 to 5.86 min. At all temperatures, survival of E. coli O157:H7 was greater in formulated products than in turkey meat with no additives. Greatest survival occurred in the turkey frank batter. Using our z-value data, times to provide a 5 D kill of E. coli O157:H7 in turkey franks cooked at 60°C, 65.6°C, or 71°C would be 26, 3.1, or 0.37 min, respectively.     

Consumer Acceptability of Cooked Stored Ground Turkey Patties with Differing Levels of Phosphate

The acceptability of fresh and stored, cooked, ground turkey patties without added phosphate or with 0.25% or 0.5% added sodium tri-polyphosphate (STP) was determined by 100 consumers. Turkey patties without phosphate were less acceptable than those with 0.5% added STP. Consumers (26) who repeated the study five times indicated that stored samples containing 0.25% and 0.5% STP were liked more and the 0.5% treatment had more meaty flavor than those samples without phosphate. Samples containing 0.5% STP were found less firm and more juicy than the other samples. The consumers scored off-flavor inconsistently.     

Lipid Oxidation and Sensory Analysis of Cooked Pork and Turkey Stored under Modified Atmospheres

Precooked pork and turkey were stored at 4°C for 18 hr and at - 20°C for 3 months in vacuum and in atmospheres of air, carbon dioxide, and nitrogen. For both short-term refrigerated storage and long-term frozen storage, vacuum-packaging of precooked turkey and pork resulted in more meaty and less warmed-over flavor and aroma than the other packaging treatments. Samples stored in carbon dioxide and nitrogen atmospheres were less “oxidized” as indicated by sensory scores and TBA values than those stored in air but were more “oxidized” than vacuum-packaged meat. Warmed-over and rancid flavor and aroma scores correlated highly and consistently with TBA values, but inconsistently with the less sensitive fluorescence method. Vacuum-packaged turkey was darker and redder than other samples after frozen storage.     

Listeria monocytogenes Inactivation in Turkey Rolls and Battered Chicken Nuggets Subjected to Simulated Commercial Cooking

Cured and uncured turkey rolls inoculted with 10⁷Listeria monocytogenes CFU/g were vacuum packaged and cooked to internal temperatures of 68°C and 74°C, respectively, in a steam-injected chamber. Samples were stored up to 15 wk at 4°C. Battered chicken nuggets were also inoculated internally with about 10⁷L. monocytogenes CFU/ g. Nuggets enclosed in bags were cooked under moist heating conditions in a convection oven to an internal temperature of 71°C. Nuggets were flushed with 30% CO₂, 70% N₂ atmosphere and sealed. Chicken nuggets were stored at 4°C up to 30 days. No Listeria monocytogenes were recovered from the cooked products suggesting that similar commercial processes are adequate to reduce populations of L. monocytogenes below detection limits.     

Display Life and Internal Cooked Color of Ground Beef from Vitamin E-Supplemented Steers

The retail display life of fresh ground meat and the internal color of patties cooked to four endpoint temperatures (55, 65, 71, and 77°C) were determined for ground beef (10% fat) from vitamin E-supplemented (500 and 2000 IU) or nonsupplemented steers. Vitamin E supplementation increased (P < 0.05) the retail dissolve life of the meat by 12 and 42 lir for 500 and 2000 IU, respectively Vitamin E did not akect (P > 0.05) internal cooked color or expressible juice color of the patties, and it did not cause premature browning or persistent redness. Increased levels of vitamin E supplementation decreased (P < 0.05) TBA values but had no effect on total reducing activity or oxidation-reduction potential.