Internal Premature Browning in Cooked Ground Beef Patties from High-Oxygen Modified-Atmosphere Packaging

ABSTRACT: This study examined the effects of location within a package and display time on the incidence of premature browning in patties made from ground beef packaged in a high-oxygen modified atmosphere (80% oxygen and 20% carbon dioxide) or in vacuum for up to 14 d. On days 3, 5, 8, 10, 12, and 14 of display, patties were formed from both top and bottom portions of tissue exposed to high-oxygen. These patties contained predominantly oxymyoglobin and metmyoglobin at the time of formation and cooking. As display progressed, the percentage of oxymyoglobin decreased ( P < 0.05) and metmyoglobin increased ( P < 0.05) in the patties for both locations, whereas the percentage of deoxymyoglobin remained stable at less than 2%. Samples that were vacuum-packaged contained predominantly deoxymyoglobin. Patties from high-oxygen packages cooked to a temperature of 71.1 °C were prematurely brown ( P < 0.05) compared with vacuum-packaged samples. Patties containing predominantly deoxymyoglobin remained pinker than patties cooked directly from high-oxygen packages (lower visual color score, higher a * value; P < 0.05) on the interior after cooking. Data in this study clearly demonstrate that, regardless of time in display, nearly 100% of patties formed from high-oxygen-packaged ground beef would be prematurely brown when cooked and could pose a food safety problem if not cooked to an endpoint temperature ensuring safety.     

Influence of Cooking Rate, Endpoint Temperature, Post-cook Hold Time, and Myoglobin Redox State on Internal Color Development of Cooked Ground Beef Patties

ABSTRACT: Three experiments investigated cooking rate, endpoint temperature, post-cook holding time, and raw myoglobin redox-state effects on ground beef internal cooked color. In Experiment 1, patties were cooked to endpoint temperatures of 65.6°C, 71.1°C, 76.7°C, 82.2°C, or 87.8°C rapidly (1°C/s), slowly (0.2°C/s), or rapidly with 6-min post-cook holding time at 104°C. Patties cooked slowly to less than 76.7°C were more well done ( P < 0.05) in appearance than those cooked rapidly. Rapidly-cooked patties cooked to less than 82.2°C and held for 6 min after cooking had less pinkness, more myoglobin denaturation, and a more well-done appearance than did rapidly cooked patties with no holding time ( P < 0.05). In Experiment 2, increasing post-cook holding time (1, 3, 6, or 12 min) after rapid cooking to 71.1°C, 76.7°C, or 82.2°C decreased pinkness and increased myoglobin denaturation ( P < 0.05), with no benefit beyond 6 min ( P > 0.05). In Experiment 3, patties cooked rapidly to 71.1°C, 76.7°C, or 82.2°C from a predominantly raw oxymyoglobin state were less pink and had more denatured myoglobin than did those cooked from a predominantly deoxymyoglobin state ( P < 0.05). Prediction equations determined that 80% of myoglobin must be denatured to create a well-done appearance. Using a slow cooking rate, post-cook holding time, or cooking from a highly oxygenated state will increase myoglobin denaturation and foster a well-done appearance.     

Effect of erythorbate, storage and high-oxygen packaging on premature browning in ground beef

Premature browning (PMB) was investigated in ground beef patties with (0.04%, w/w) and without erythorbate. In Experiment 1, patties were stored at 4 °C for 48 h; at -18 °C for 21 days; or at -18 °C for 21 days, thawed at 4 °C for 24 h; and cooked. Bulk ground beef was stored at -18 °C for 24 days, thawed for 24 h at 4 °C, and patties prepared and cooked immediately. In Experiment 2, fresh patties were overwrapped with oxygen-permeable film or packaged in 80% O(2)/20% N(2) (MAP), and stored for 48 h at 4 °C, or at -18 °C for 21 days, and cooked. Total reducing activity and color (L*, a* and b* values) were measured immediately prior to cooking. Patties were cooked to internal temperatures of 60, 66, 71 and 77 °C and internal cooked color was measured. Total reducing activity was higher for the erythorbate treatment than controls for all storage conditions (P<0.05). a* Values of cooked patties were higher for erythorbate than control treatments under all storage and packaging conditions at 60 and 66 °C (P<0.05). The presence of erythorbate in ground beef patties appeared to maintain red color at cooked internal temperatures of 60 and 66 °C. Frozen bulk storage appeared to increase the susceptibility of ground beef to PMB when compared to fresh and frozen patties. Patties cooked directly from frozen state appeared less susceptible to PMB than frozen-thawed and bulk storage. Ground beef appeared predisposed to PMB when stored in high-oxygen MAP at 4 °C for 48 h.     

Effect of muscle source on premature browning in ground beef

Premature browning (PMB) describes cooked beef that may appear done before reaching 71 °C. Ground beef from paired Longissimus lumborum (LL) and Psoas major (PM) muscles was formed into patties. Patties were cooked immediately, and after 48 and 96 h storage at 4 °C. Total reducing activity (TRA) and external color were measured immediately prior to cooking. Patties were cooked to internal end point temperatures of 60, 66, 71 or 77 °C and internal cooked color (L(*), a(*) and b(*) values) was measured. Raw PM patties had greater L(*) values and lesser a(*) values than those from LL (P<0.05). For LL and PM, raw a(*) and b(*) values decreased with storage from 0 h to 96 h (P<0.05). At 0 and 48 h storage, cooked patties prepared from PM had greater a(*) values than those prepared from LL at all internal endpoint temperatures (P<0.05). Internal cooked a(*) values of patties from PM decreased with storage of raw patties, whereas it was stable for LL patties (P<0.05).     

Effects of Endpoint Temperature on the Internal Color of Pork Loin Chops of Different Quality

ABSTRACT: The effects of 5 endpoint temperatures for cooked, internal color were determined for boneless pork longissimus muscle from 4 treatment groups: normal, normal-injected, PSE, and DFD. Visual and instrumental color, myoglobin denaturation, and acid phosphatase (ACP) of raw and cooked samples were evaluated. Visual internal color became (P < 0.05) less pink as endpoint temperature increased; however, DFD chops were more pink (P < 0.05) and PSE chops were less pink (P < 0.05) than other treatments at most endpoint temperatures. Cooked color was similar (P > 0.05) for chops from normal and normal-injected groups. Myoglobin denaturation increased as endpoint temperature increased. ACP activity in raw chops was not affected by treatment group and it was a good indicator of doneness at 71.1 °C.     

Effect of Cooking on Cholesterol Content of Patties Containing Different Amounts of Beef, Textured Soy Protein and Fat

Ground beef patties were prepared to contain 0, 10, 20 or 30% rehydrated textured soy protein (TSP) and 8, 16 or 27% fat. Patties were cooked from the frozen state on a rack in a preheated oven at 177°C to an endpoint internal temperature of 75°C. The cholesterol content of raw ground beef patties decreased as the amount of TSP increased and also decreased as the fat content decreased from 27 to 16 or 8%. At initial fat levels of 8 and 16%, there were no significant differences in cholesterol retention (per-patty basis) during cooking among patties with initial TSP (rehydrated) levels of 0, 10, 20 and 30%; at an initial fat level of 27%, however, patties containing TSP (10, 20 or 30%) retained substantially higher (P < 0.05) amounts of cholesterol when cooked than did those without TSP.     

Cooked Color in High pH Beef Patties as Related to Fat Content and Cooking from the Frozen or Thawed State

Beef patties were processed from high pH (>6.0) beef to contain 5, 10, 15, 20 or 25% fat. Patties were cooked to 71°C from the frozen or thawed state before evaluating color. Neither fat content nor state of patties when cooked exerted any major influence on color, but linear effects (p<0.01) in association with increased fat content included higher L* values and hue angles and lower a* values (15.2% reduction). Higher values for L*, b* (but not for 5% fat patties), and hue angles were observed for patties cooked thawed rather than frozen. The use of high pH beef lessened the effects of increased fat and cooking from the thawed state on increased brown color in cooked patties.     

Thawing Prior to Cooking Affects Sensory, Shear Force, and Cooking Properties of Beef Patties

Patties from 6 commercial formulations were cooked to 71°C from either the frozen state or after thawing for 24 to 27 h at 4 °C to eliminate the pink/red color exhibited when cooked to 71 °C from the frozen state. Thawed patties had shorter cooking times, higher cooking yields, and lower shear force peak load and peak energy values. Patties cooked from the thawed state increased in thickness during cooking, while patties cooked from the frozen state decreased in thickness during cooking. Thawing prior to cooking increased sensory evaluation scores except for patties made with carrageenan. Thawing not only eliminated the problem of pink/red color after cooking but also improved sensory, shear force, and cooking properties of beef patties.     

FACTORS AFFECTING COLOR PROPERTIES OF BEEF PATTIES COOKED ON AN OUTDOOR GAS GRILL

Visual and instrumental color properties were obtained on beef patties cooked on an outdoor gas grill. Factors evaluated as to their influence on color were fat content, (20–28% vs 6–10%) patty handling prior to cooking (fresh, thawed either as patties or bulk ground beef), endpoint in cooking (57, 66, 71C, slit in outer edge of patty during cooking showing brown color), lighting conditions and evaluation time post-cooking. Factors resulting in less pink/red color and more brown color in cooked patties were (1) higher fat content, (2) cooking bulk frozen, thawed, then pattied product, (3) higher endpoint temperature and longer time postcooking before evaluation. Termination of cooking by observing brown color in slits in patties cooked on a gas grill was not synonymous with a safe internal temperature.     

CHEMICAL PROPERTIES OF GROUND BEEF PATTIES EXHIBITING NORMAL AND PREMATURE BROWN INTERNAL COOKED COLOR

Premature browning is a condition in which ground beef looks well-done at lower than expected temperatures. To study this color pattern, chemical properties were measured on raw and cooked patties (55, 65 and 75C) that developed normal (NRM) and premature brown (PMB) color when cooked to 55C. NRM patties were visually and instrumentally redder at all temperatures (P<0.05) than PMB patties. Visual color of PMB patties at 55C and NRM patties at 75C were similar (P>0.05). Heme and nonheme iron, total pigment and pH did not differ (P>0.05) between groups. Nonheme iron increased (P<0.05) as endpoint temperature increased. Patties with NRM color had lower (P<0.05) TBA values and oxidative-reduction potentials and higher (P<0.05) total reducing activity than patties with PMB. No difference (P>0.05) occurred in precipitation of juice extracts from NRM and PMB patties during heating (40 to 75C). Premature browning was related to patty oxidation.     

Variability in temperature distribution and cooking properties of ground pork patties containing different fat level and with/without salt cooked by microwave energy

This study was carried out to evaluate the cooking effects of fat level (10% and 20%) with and without NaCl (1.5%) on the microwave cooking pattern and properties of ground pork patties. Each patty was cooked from a thawed state to 76.7°C in a microwave oven with full power (900W). Cooking rate in patties produced without salt was not affected by fat level, but the addition of salt in pork patties decreased cooking rate, regardless of fat levels. The temperatures at the edges of the patties increased faster than those at the center or the mid-way positions. In the patties with NaCl, the temperature of the center position was higher than that of the mid-way position. Patties containing salt within the same fat level had higher moisture content and lower fat content than those without salt, although no significant differences in compositional properties were observed between the center, midway, or edge positions. Total cooking loss, drip loss, and reduction in diameter and thickness were higher in patties with 20% fat compared to those with 10% fat, but the addition of salt resulted in reduction, regardless of fat level. Also, the addition of salt increased the redness and reduced yellowness of the cooked products.     

RELATIONSHIPS AMONG CHEMICAL, COOKING AND COLOR PROPERTIES OF BEEF PATTIES COOKED TO FOUR INTERNAL TEMPERATURES

A study involving five laboratories and nationwide sampling of ground beef was undertaken to determine cooking and color properties of patties cooked to 52.7, 65.6, 71.1 and 79.4C. The design of the study included purchase location (local, distant) and patty handling prior to cooking Pesh, thawed either as patties or bulk ground beef). Purchase location was not a statistically significant influence on cooking and color properties. Patties processed from bulk thawed product had a higher amount of brown cooked color. A strong relationship existed between visual and instrumental measures of red color in cooked patties. However, correlations among other cooking properties were low. Patties with higher fat content were associated with shorter cooking times, lower cooking yields and more brown cooked color. The low relationships between raw and cooked patty properties limits the use of raw ground beef properties as predictors of food safety in cooked beef patties. This further supports the use of instant read meat thermometers in cooking beef patties to at least 71C.     

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.     

Effect of natural antioxidants on oxidative stability of cooked, refrigerated beef and pork

ABSTRACT:  The effect of grape seed extract (GS; 0.01% and 0.02%), oleoresin rosemary (OR; 0.02%) and water-soluble oregano extract (WS; 0.02%) on oxidative and color stability of cooked beef and pork patties stored at 4 °C for 8 d was determined. Fresh beef or pork lean and trim were ground, mixed (30% fat), and divided into 5 portions. Antioxidants mixed with salt (2%) were added. Patties were formed, cooked to an internal temperature of 71 °C, overwrapped in PVC, and stored at 4 °C. Lipid oxidation, assessed using thiobarbituric acid reactive substances (TBARS) and sensory evaluation, instrumental and visual color, and pH were determined after 0, 2, 4, 6, and 8 d. Based on TBARS values and off-odors associated with lipid oxidation such as rancidity, wet cardboard (for beef patties), and grassy (for beef and pork patties), grape seed extract resulted in the best antioxidant activity in both meat species. It did not change instrumental color measures of redness, yellowness, or color intensity, and appeared to reduce visual green discoloration in beef patties. The higher GS concentration (0.02%) exhibited more antioxidant activity than the lower concentration (0.01%). Therefore, grape seed extract at 0.02% has the potential to reduce oxidative rancidity and improve shelf life of refrigerated cooked beef and pork patties.     

Fat Level, High Temperature Cooking and Degree of Doneness Affect Sensory, Chemical and Physical Properties of Beef Patties

Ground beef patties containing either 4 or 20% fat were cooked by electric grill (G) alone or in combination with overhead broiler unit (BG) to be (visually) either medium or well-done. Patties with 20% fat had higher beef flavor intensity, juiciness and tenderness scores, lower Instron shear and compression values, and lower cooking yields than 4% fat patties. However, 4% fat patties cooked to medium, had similar sensory ratings to 20% fat patties cooked well-done. About 20% of patties cooked to medium did not reach recommended internal temperatures and holding times for food safety.     

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.     

EFFECTS OF INJECTION OF A DILUTE PHOSPHATE-SALT SOLUTION ON PORK CHARACTERISTICS FROM PSE, NORMAL AND DFD CARCASSES

Phosphate-salt pump effects were evaluated on sensory characteristics of pale, soft, exudative (PSE) pork, normal and dark, firm and dry (DFD) pork. Water-holding capacity, instrumental color (L*, a*, b*), pH, and muscle color scores were determined at 24 h postmortem on pork loin pairs (n=21 pairs). Based on color score, paired loins were assigned to PSE, normal or dark, firm, dry groups. PSE muscles were lighter, redder and more yellow than normal or DFD muscles; hue angle indicated that DFD muscles were actually closer to the true red axis of the CIE Lab Color Space. Drip and purge losses were higher (p<0.05) in PSE muscles. Paired loins were pumped with water (controls) or 0.3% tripolyphosphate solution (0.25% salt) to 110% of original weight, vacuum packaged, frozen, cut into chops, and cooked to 70 or 80C. Phosphate-salt pumped loins were juicier and more tender (p<0.05) than water-pumped loins regardless of muscle condition. Loins cooked to 70C were juicier, were more tender (sensory) but required more force to shear than those cooked to 80C.     

Effect of erythorbic acid on cooked color in ground beef

Consumers often use the color of cooked ground beef as an indicator of doneness. For safety reasons, it is recommended that the center of ground beef products be heated to 71°C. In some instances beef may appear done before reaching 71°C, a condition termed premature browning (PMB). Ground beef (15% fat), with added erythorbic acid (ERY) at 0.04 and 0.06% was formed into patties, wrapped in oxygen permeable film, and stored in the dark at 4°C. Patties were stored for either 10 h or 58 h and then cooked to internal end point temperatures of 60, 66, 71 or 77°C. Internal cooked color L(?), a(?) and b(?) values were measured. For beef patties stored 10 h, there was no effect of ERY on internal cooked color. After 58 h storage, ground beef with 0.04 and 0.06% ERY had higher a(?) values than controls at 60°C (P<0.05). Beef with 0.04% ERY cooked to an internal temperature of 66°C had higher a(?) values than 0.06% ERY and controls (P<0.05). There was no effect of ERY on color of beef patties cooked to 71 or 77°C. The presence of 0.04% ERY in ground beef patties stored 58 h appeared to maintain red color at internal temperatures of 60 and 66°C.     

Color and Heat Denaturation of Myoglobin Forms in Ground Beef

To determine the effects of myoglobin forms on internal cooked color in ground beef, patties containing predominantly deoxy-(DMb), oxy-(OMb), or metmyoglobin (MMb) were cooked to 55, 65, or 75 °C. Only patties with DMb appeared red and undercooked at 55 °C, and their color became progressively more brown at 65 and 75 °C. Patties with OMb and MMb were brown at 55 °C and could be mistakenly perceived as being cooked enough to consume. Judging the doneness of ground beef using internal cooked color alone would be valid only if the pigment at time of cooking was predominantly DMb. In model studies, DMb had greater thermal stability than MMb especially at higher pH.     

Final Cooked Temperature Effects of Ground Pork on its Ability to React with Nitrite

ABSTRACT: Fresh ground pork patties from longissimus dorsi muscle were cooked to endpoint temperatures of 54.4 °C, 60.0 °C, 65.6 °C, 71.1 °C, 76.7 °C, or 82.2 °C. After cooking, patties were immersed in a solution of sodium nitrite (125 ppm) and water for 24 h. All patties then were heated again to a final endpoint temperature of 82.2 °C to allow possible formation of nitrosohemochrome. Instrumental color data, spectrophotometric 650/570 nm reflectance ratio, and visual panelists' scores on both exterior and interior surfaces revealed greater redness (pinking) at the lower initial cooked temperature endpoints. Most importantly, this study showed that all patties developed pink color on reheating, regardless of initial endpoint cooked temperature.