Beef patties (86 and 143 g) formed from high-fat (20 to 29%) and low-fat (6 to 10%) ground beef obtained in eight different selections for both high and low fat content were cooked by either a gas grill or an electric griddle. Patties were cooked to either 66.1 or 68.3°C as determined in the thickest section, and internal temperatures were recorded after cooking at 1-s intervals for 180 s in both thick and thin sections of patties. Time-temperature curves (after cooking) were evaluated for compliance with regulatory requirements for classifying patties as fully cooked. For patties cooked to 66.1°C, the maximum highest temperature in the thickest patty section often did not reach 71.1°C (recommended for cooking of beef patties by consumers). Although thin sections of patties had higher temperatures than thick sections at the termination of cooking, temperature variability was greater and declines in temperature occurred sooner in thin patty sections. Failure to meet fully cooked, time-temperature requirements was greater in thin than thick sections. Thicker (143-g) patties possessed longer post-cooking times before declining in temperature than thinner (86-g) patties. Although many beef patties cooked in this study achieved regulatory time requirements for maintaining 66.1 or 68.3°C (as well as attaining 71.1°C), some patties did not meet these requirements. Because of the considerable temperature variability that can exist within patties at the conclusion of cooking, use of end point temperatures of less than 71.1°C is not recommended for consumers. Consumers should allow several minutes of holding following cooking before consumption to maximize the increases in postcooking temperature. Further research is required to establish cooking procedures that will improve temperature uniformity and eliminate “cold spots” during cooking of beef patties.

An interlaboratory study was undertaken to assess the frequency that cooked color of ground beef patties appeared brown at internal temperatures of 52.7°C (135°F), 65.6°C (150°F), 71.1°C (160°F), and 79.4°C (175°F). In general, as internal cooked temperature of the patties increased, the following results were observed in the patties: (i) more brown meat color, (ii) less pink or red juice color, and (iii) more cooked texture. However, brown meat color occurred prematurely at the two lower internal temperatures (57.2°C/135°F and 65.6°C/150°F) that are insufficient to eliminate foodborne pathogens without holding times. The common consumer practice of freezing bulk ground beef, followed by overnight thawing in a refrigerator, led to substantial premature brown color in patties cooked from this product. In addition, at 71.1°C (160°F), recognized to be the lowest temperature for cooking ground beef safely in the home, meat color, juice color, and texture appearance were not fully apparent as doneness indicators. In fact, at no temperature studied did 100% of the patties appear done when evaluated by the criteria of no red or pink in the meat, no red or pink in the juices, or by texture appearance. Patties in this study were evaluated under a set protocol for forming the products, cooking, and viewing under the same lighting conditions. Other preparation conditions are possible and may produce different results. Thus, temperature to which patties have been cooked cannot be judged by color and appearance. This study provided the evidence to support the message to consumers regarding cooking of beef patties of “use an accurate food thermometer and cook beef patties to 160°F (71.1°C)” in place of messages based on consumer judgment of cooked color.

The growth of spoilage bacteria results in a shorter shelf life of meat, causing economic losses to the meat industry. Based on 23S rDNA sequence data of Pseudomonas aeruginosa , two primers designated as PF (23 bases) and PR (20 bases) were synthesized for use in the polymerase chain reaction. A unique 207-base-pair DNA product from nine different bacteria typically associated with meat spoilage was amplified by the primers. Dot blot analysis with the internal DNA probe specific for the amplified products confirmed that the amplified DNA sequence is specific for the spoilage bacteria studied.

Ground beef patties were processed from boneless beef which was subjected to two different inspection systems for bone and cartilage defects. One system permitted a higher (“high”) level of defects (USDA Food Safety and Inspection Service, Meat and Poultry Inspection Requirements), while the other system (USDA PP-B-2120 Federal Purchasing Specification) permitted only a lower (“low”) level of defects. Before formation into patties, the ground beef was subjected to three processing systems for defect removal (none, Weiler Bone Collector System, Speco Spiral Groove Plate System). A sensory approach (teeth and tongue) for detecting defects with cooked patty samples revealed more bone and cartilage defects in the “high” than the “low” formulation regardless of defect removal system. While the defect removal systems reduced the levels of detected defects in the “high” formulation, neither system produced patties with defect levels achieved through inspection procedures required to produce “low” levels of these defects. However, it appears that much of the bone remaining as a defect in boneless beef is reduced in size during grinding so as to be undetectable by sensory approaches.

Twenty-four dairy cows were slaughtered under commercial conditions, muscles were excised from one side within 3 h of slaughter and from the second side after 24 h chill at 3°C. Surface aerobic bacterial plate counts, (APC 5, 20, and 35°C , that is, plates were incubated at 5, 20 and 35°C, respectively) obtained from the rounds immediately before deboning did not vary significantly between the hot and chilled carcasses. The APC ( 5, 20, and 35°C ) increased (P<.01) during removal of rounds from both hot and chilled carcasses, and the magnitude of the increase was greater than one logarithm. The bacterial count on loins and rounds that were overwrapped and frozen generally was lower than on loins and rounds held at 3°C for 7 and 14 d before being frozen. The APC ( 5, 20, and 35°C ) of fresh ground beef fabricated in 450-kg batches from trimmings of hot cow carcasses were not significantly different from that made from the chilled carcasses. Addition of chilled USDA Choice plates to increase the fat content and lower the temperature of the manufactured ground beef increased (P<.01) APC counts in most instances. The log count of the USDA Choice plates was about 5 to 6/cm 2 ; whereas that of the cow beef was about 2 to 4/cm 2 . The mean counts of coliforms, fecal coliforms and Escherichia coli were usually less than one log, so significant treatment differences, when they did occur, were unimportant. Results of this research indicate that hot boning does not adversely affect the microbial quality of selected primals and ground beef.

Two separate studies were conducted to evaluate variations in the amount of connective tissue remaining in beef muscle on resultant properties of flaked and formed steaks. Use of chucks rather than rounds as raw material produced greater tenderness, less sensory panel determined connective tissue and lower juiciness scores. As a team of trimmers repeated the instructed trimming procedures on round and chuck muscles over a 3-d period, it appeared that over this time more of the connective tissue was being removed from chuck and less from round muscles. For chuck muscles, more of the soluble collagen was being left on the muscles over the 3-d period. However, these differences in total and soluble collagen did not influence the properties measured. In a second study, which consisted of three (high, intermediate, low) levels of connective tissus in raw materials, texture profile panelists found a greater amount of gristle and webbed tissue (form of connective tissue) in steaks made from raw material with high connective tissue. These steaks with high connective tissue levels were also visually rated as more distorted and fibrous following cooking, with greater hardness and cohesiveness during first bite. Samples from the steaks had higher shear force and Newton values.

Ten lamb carcasses were used to evaluate the effects of hot-boning (HB), cooking, freezing and method of reheating upon cooking and palatability attributes of lamb roast. After slaughtering, the leg and loin were removed (30 min post-exsanguination) from the right side and cooked immediately (HB), while the left side was fabricated 5 d later (cold boned, CB) and cooked until the internal temperature reached 68°C. The roasts were frozen and stored for about 45 d. Roasts were thawed (2°C), and pre-cooked roasts were divided into similar portions and assigned to three reheating methods: ( a ) conventional electric oven ( b ) microwave oven and ( c ) a combination method where the first half of the cooking time was by conventional roasting and the second half by microwave oven. Results indicate HB roasts had higher (P<.05) cooking losses, thaw losses and reheating losses (3%) than CB roasts. HB leg roasts required less (P<.05) time to cook than CB, but no difference (P>.05) was found for the loin roasts. Conventional oven reheating resulted in higher thaw and reheating losses, and a longer reheating time than microwave reheating or the combination method. The shear values for HB muscles of the leg were lower, in most instances, than those for CB muscles of the leg. Panel tenderness scores indicated that pre-cooked, conventional reheated HB, semimembranosus (SM) and CB, SM, were more tender than the SM reheated with a microwave oven. All the precooked, reheated products were of acceptable palatability.

Beef livers from freshly slaughtered cattle were inoculated with coagulase-positive Staphylococcus aureus and then placed in frozen storage. After 14 d of frozen storage, one-half of the livers were subjected to 21°C for 24 h followed by a 15-d period of storage at −1°C. The other livers were kept in frozen storage (−29°C) during this 15-d period after which all livers were subjected to either 10 or 21°C temperatures. S. aureus counts did not change during the 15-d storage period at −1°C, whereas aerobic plate counts (APC) increased by over 3 log 10 cycles. The low storage temperature plus the growth of competitor bacteria most likely prevented S. aureus from proliferating. When all livers were subjected to 24 to 144 h of storage at either 10 or 21°C, those that had been subjected to 15 d of slow surface thawing displayed a lower S. aureus count and higher APC than livers subjected to rapid thawing followed by holding at the high temperatures. This may mean that if livers become contaminated with substantial numbers of S. aureus before freezing, then rapid thawing coupled with high storage temperatures (more typical of meat merchandising in less developed countries) could allow for rapid S. aureus growth before competitor organisms increase in numbers.

Thirty beef carcasses were used to evaluate the effects of electrical stimulation and conditioning periods and microwave cooking upon sensory and shear properties of pre-rigor semitendinosus muscle samples. The intact muscle was removed from the right side within 45 min post-exsanguination and was electrically (ES) stimulated [100 impulses (1 s on and 1 s off, A.C., 110V, <5 amps)], while the remaining paired muscle served as the control (NS). After electrical stimulation, the muscle was cross-sectioned into three portions. A 2.54-cm thick sample was removed from the central portions of the ES and NS muscles and cooked immediately in a microwave oven to an internal temperature of 66°C. The remaining two similar sized portions were conditioned at 13°C for 2 h or 4 h before cooking. Three cores (1.27 cm) were removed from each sample parallel to the muscle fiber, and all cores were sheared twice. Samples from the conditioning periods were frozen, thawed, reheated and evaluated for palatability traits by a 10-member trained panel. Results indicate higher sensory panel ratings (P<.05) for tenderness, connective tissue and flavor intensity and lower shear force (WBS and Instron) values and longer sarcomeres from ES. With the conditioning periods used, microwave cooking was too rapid for pre-rigor muscle, as exemplified by the high shear values (6.4 and 7.8 kg/1.27 cm for ES and NS, respectively) which indicates a very tough sample of meat. Cooking yield was highest for muscle samples cooked immediately after slaughter. Roasts conditioned for 4 h before cooking had higher (P<.05) juiciness and flavor intensity scores than roasts held for 2 h, regardless of stimulation treatments.

Ninety each of beef livers, hearts, tongues and kidneys were transported in a refrigerated van from Palestine, Texas to Rungis, France. Product arrived at destination 21 d after departure (24 d after removal from the animal) and was evaluated for color and odor by a four-member experienced USA panel and by variety meat buyers at the Rungis market. Vacuum packaging most successfully protected color and odor of tongues and hearts, kidneys had acceptable color and odor if not wrapped, and livers were most desirable in color and most acceptable in odor if wrapped with polyvinyl chloride film. Buyers on the Rungis, France market paid a premium for those variety meats which were vacuum packaged in relation to comparable USA product that was transported in the frozen state. Beef variety meats can be successfully transported to European markets without freezing.

Shelflife characteristics of lean color, lean surface discoloration and off-odor were evaluated on vacuum-packaged sliced bacon processed under commercial operations in four separate plants. In addition to the normal processing variations at each plant, three formulations with various levels of sodium nitrite and potassium sorbate were used: ( a ) 0 ppm sodium nitrite, ( b ) 40 ppm sodium nitrite-2600 ppm potassium sorbate and ( c ) 120 ppm sodium nitrite. Bacon was evaluated after 0, 2 and 4 d of simulated retail conditions following 10, 30, 50 and 70 d of storage under refrigerated dark conditions. Bacon processed with 0 ppm sodium nitrite underwent more lean surface discoloration than bacon processed with the other two formulations. The amount of lean surface discoloration, presence of undesirable colors and off-odor scores were similar between the 40 ppm sodium nitrite-potassium sorbate formulation and the 120 ppm sodium nitrite formulation except for the plant which employed a low salt-high sugar formulation. In this situation, especially with longer periods of storage and retail display, the 120 ppm sodium nitrite formulation yielded less surface discoloration, a lower frequency of undesirable colors and less off-odor than the 40 ppm sodium nitrite-2600 ppm potassium sorbate formulation. The occurrence of off-odor generally increased uniformly as a function of longer storage time regardless of sodium nitrite-potassium sorbate levels and processing plant variations.

The longissimus, semitendinosus and semimembranosus muscles from 60 U.S. Utility beef carcasses were used to investigate the effects of electrical stimulation (ES), different postmortem boning times, blade tenderization coupled with enzyme dip, and storage conditions on the quality, appearance, cooking and sensory properties of cooked beef muscle. Muscles were removed from stimulated and nonstimulated sides at 1, 3 or 24-h Postmortem, wrapped in PVC film and either immediately frozen at −40°C or stored at 2 to 3 C for 24 h and then frozen at −40°C. Before freezing, part of the muscles was allocated to blade tenderization and/or enzyme dip treatments while the remainder served as controls. Electrical stimulation increased tenderness in muscles excised at 1 h postmortem; however, as boning time increased, the effects of ES on tenderness decreased. It was concluded that electrical stimulation increased tenderness sufficiently to allow boning at 1 or 3-h postmortem. Blade tenderization and/or enzyme dip treatments did not significantly improve tenderness of any of the muscles over the effects of ES. With the exception of the semitendinosus, muscles chilled 24 h before freezing were significantly (P<.05) more tender than those frozen immediately.

The microflora associated with fresh and temperature abused beef livers, kidneys, hearts, tongues and pork livers was identified. Variety meats were obtained from a packing plant and allocated to three packaging treatments, i.e., vacuum packaging, polyvinyl chloride film wrapping and no wrapping (unwrapped). Isolates were characterized from fresh variety meats following frozen storage for three weeks at −29 ± 2 C; and following simulated temperature abuse. Classification of 1555 isolates obtained from aerobic plate counts at 35, 20 and 7 C is provided. Fresh variety meats were found to be contaminated with a variety of bacteria commonly associated with fresh red meats immediately post-mortem, with Micrococcus sp. being the most frequently isolated gram-positive bacterium and Escherichia coli the predominating gram-negative isolate. Frozen variety meats before simulated temperature abuse reflected a higher proportion of gram-positive organisms and fewer Enterobacteriaceae than fresh variety meats. Abused variety meats yielded predominately Pseudomonas strains, except where vacuum packaging was used, in which case isolates were predominately Lactobacillus sp. and Micrococcus .

Effects of various handling, packaging, temperature-abuse and storage conditions were determined on the microbiological characteristics of beef livers and tongues. These organs were evaluated: ( a ) initially following slaughter, ( b ) immediately following the frozen storage period of 2–4 weeks at −29°C and ( c ) following a simulated shipping-temperature abuse of 24 h at 22–28°C followed by 13 days of storage at −1 ± 0.5°C. Initial counts (log/cm 2 ) of coliforms, coagulase-positive Staphylococcus aureus and Clostridium perfringens ranged from 0.19–1.37. Generally, neither freezing nor temperature-abuse had a significant effect on these microorganisms. Vacuum-packaged beef tongues and livers, generally, had lower bacterial counts than did either naked or polyvinyl chloride film-wrapped products. Generally, it was observed that abusive storage temperatures, in conjunction with the naked and film-wrapped packaging systems, appear to present potential microbial spoilage problems when compared with vacuum packaging.

The effects of electrical stimulation on palatability of hot-boned, pre-rigor and cold-boned, post-rigor frozen beef roasts were studied by use of 16 steer carcasses. Both sides of 8 carcasses were electrically stimulated (1.5 amps; 100 - 1 s impulses); sides from the other 8 carcasses served as controls. One side of each carcass was hot-boned and the remaining side was boned following a 48 h chill (2 C). Roasts from the rump portion (anterior one-fourth) of the biceps femoris muscle were vacuum-packaged and frozen (−20 C). Following a 48-h thaw (0 C). roasts were weighed, measured for length, width and depth, seasoned, placed in cooking bags and roasted to 62.5 C. Cooking losses were less (P<0.06) for hot-boned, pre-rigor frozen vs. cold-boned, post-rigor frozen roasts. Raw pH (post-freezing) was lower (P<0.01) for hot-boned than cold-boned roasts. No differences (P>0.05) were noted in shape changes for stimulation or chilling. Using triangle tests, untrained panel members were able to distinguish controls from electrically stimulated roasts and hot-boned from cold-boned roasts when served as thick (1.27 cm) or thin (2 mm) samples. Thick and thin samples of cold-boned roasts were preferred over hot-boned roasts. For roasts from carcasses that were not electrically stimulated, 62.6% preferred cold-boned roasts for thick samples while 61.4% preferred cold-boned roasts for thin samples. Cold-boned roasts from electrically stimulated carcasses were preferred over hot-boned roasts, 56.5% (thick) vs. 51.5% (thin). Warner-Bratzler shear force results indicated that hot-boned, control roasts required 79% more shear force than cold-boned roasts, but roasts from electrically stimulated carcasses required 14% more force to shear hot-boned than cold-boned roasts.

Shelflife characteristics were scored in ground beef manufactured to certain levels of fat (16 ± 1%, 20 ± 1%, 24 ± 1%, 28 ± 1%) from various sources of fat trimmings (Choice flanks, plates, trimmings, brisket and kidney fat). Aerobic Plate Counts (APCs) were determined on the various lean and fat trimmings and the final ground beef (24 and 28% fat levels only). The characteristics were assessed over a 3-day retail display period. Off-odor was rated as stronger in ground beef formulated to 28% fat than to 16% fat. Increases in the duration of retail display were associated with greater darkening and surface discoloration of ground beef. Formulations with kidney and brisket fat had high (10 7 /g) APCs at the start of the shelflife study in one batch. However, the increase in APCs over the 3-day display was less for ground beef containing these two materials than for ground beef with fat from other sources. It would appear that APCs can be as high as 10 7 /g in 4- to 5-day postmortem trimmings under industrial conditions. Surface discoloration was strongly related with APCs (r = 0.82). The presence of 50–75% surface discoloration in ground beef was a good indication of APCs in excess of 10 8 /g.

Various combinations of mechanically deboned beef (MOB) and structured soy protein fiber (SSPF) were used at 15 and 30% levels in formulation of dry fermented salami. Lactic acid, pH and bacterial assessments were conducted at 24-h intervals during the pan-curing stage and at 15-day intervals during the 60-day drying period. The substitution of MDB or SSPF in the 11 separate salami treatments had no effect upon pH, lactic acid content or growth of various bacteria. Bacterial evaluation included determination of total aerobic plate counts, Lactobacillus , Staphylococcus and psychrotrophic bacteria. Lactic acid content and pH values were within ranges typical for dry fermented salami. Lactic acid content increased as a function of increased Lactobacillus numbers resulting in lowered pH values. Total aerobic plate and psychrotrophic numbers paralleled to some degree the Lactobacillus counts over the entire study. A low incidence of non-mannitol fermenting-coagulase positive Staphylococcus was observed. It would appear that MOB and SSPF can be successfully substituted at elevated levels in dry fermented salami from a microbiological standpoint, while not interfering in lactic acid production needed for flavor and preservation.

Several studies were initiated to evaluate factors that exert an influence on bacterial counts, shelf life, and consumer acceptance of commercially processed chopped beef. Bacterial counts in chub packaged (oxygen impermeable film) product underwent only slight increases when evaluated every 4 days over a 20-day storage period. Retail packaging of chopped beef after both 16 and 20 days of chub storage resulted in severely limited shelf life of the retail film wrapped product in terms of bacterial counts, surface discoloration, and flavor. Differences in the anatomical location (chuck, flank, navel, and head) of beef trimmings did not exert a major influence on chopped beef shelf life. However, the use of CO 2 pellets did lower psychrotrophic bacterial numbers in some samples, with subsequently less surface discoloration and improved flavor. Reductions in bacterial counts occurred during the 3-day retail storage in oxygen permeable film only for chopped beef stored in chub form for a total 18 days before the 3-day storage.