Final Internal Temperature Research Articles

The effect of muscle, cooking method and final internal temperature on quality parameters of beef roast

The aim of the study was to evaluate the influence of cooking conditions (dry air and steam) and final internal temperature (75, 85, 95°C) on the physico-chemical properties of beef infraspinatus (INF) and semimembranosus (SEM) muscles as well as their tenderness and juiciness. Cooking method and temperature influenced moisture, total collagen content in cooked meat and cooking loss, whereas muscle type affected fat, total collagen content and cooking loss. Warner–Bratzler shear force values were affected by cooking method, which also influenced juiciness of roasts. Temperature affected tenderness and juiciness, whereas muscle type influenced juiciness. The most desirable tenderness had INF heated in steam and dry air to 95°C. Processing SEM in dry air to 85 and 95°C lowered the juiciness of the roasts. There were significant correlations between physico-chemical, sensorial and image attributes, however high accuracy of prediction (r2>0.8) was achieved only for SEM muscle.

Temperature and Bacterial Profile of Post Chill Poultry Carcasses Stored in Processing Combo Held at Room Temperature

Post chill whole poultry carcasses from a commercial processing plant were stored in a processing combo at room temperature (70 °F/21 °C) for 54 h to mimic the scenario of temperature abuse before further processing. Temperature data were collected in 1-min intervals and averaged each hour by 9 temperature data loggers. Two linear regressions were developed for the combo and internal breast temperature and slopes were nearly identical. Microbial data was collected by performing whole bird carcass rinses that were enumerated for aerobic plate count (APC), Enterobacteriaceae, Escherichia coli, and total coliform. Samples were collected from the chiller chute at time zero for initial bacterial counts. Carcass sampling continued once the internal breast temperature achieved 45 °F (7 °C 10 h) and continued every 2 h until the final internal breast temperature was 63 °F (17 °C 54 h). Linear regressions were developed for the first 26 h, which exhibited no statistically significant growth except for Enterobacteriaceae. A 2nd linear regression (28 to 54 h) exhibited significant growth for all analyses. Overall, APC increased from a log(10) colony forming unit (CFU)/mL count of 2.86 to 7.02, Enterobacteriaceae increased from 0.66 to 6.64, coliform increased from 0.72 to 4.81, and E. coli increased from 0.53 to 4.45. Denaturing gradient gel electrophoresis was performed to detect changes in the bacterial populations, which indicated 95% similarity within sampled groups, but the overall percent similarity among samples collected over 54 h was 8%. From the data, microbial growth demonstrates a period of 26 h for minimal growth; therefore, the product could be further processed rather than designated as waste.

Integrity of nuclear genomic deoxyribonucleic acid in cooked meat: Implications for food traceability

It is essential to isolate high-quality DNA from muscle tissue for PCR-based applications in traceability of animal origin. We wished to examine the impact of cooking meat to a range of core temperatures on the quality and quantity of subsequently isolated genomic (specifically, nuclear) DNA. Triplicate steak samples were cooked in a water bath (100 degrees C) until their final internal temperature was 75, 80, 85, 90, 95, or 100 degrees C, and DNA was extracted. Deoxyribonucleic acid quantity was significantly reduced in cooked meat samples compared with raw (6.5 vs. 56.6 ng/microL; P < 0.001), but there was no relationship with cooking temperature. Quality (A(260)/A(280), i.e., absorbance at 260 and 280 nm) was also affected by cooking (P < 0.001). For all 3 genes, large PCR amplicons (product size >800 bp) were observed only when using DNA from raw meat and steak cooked to lower core temperatures. Small amplicons (<200 bp) were present for all core temperatures. Cooking meat to high temperatures thus resulted in a reduced overall yield and probable fragmentation of DNA to sizes less than 800 bp. Although nuclear DNA is preferable to mitochondrial DNA for food authentication, it is less abundant, and results suggest that analyses should be designed to use small amplicon sizes for meat cooked to high core temperatures.

Effects of ageing and low internal temperature of grilling on the formation of heterocyclic amines in beef Longissimus dorsi muscle

The mutagenic heterocyclic amines (HAs) originate in processed proteinaceous food. The effects of ageing (non-aged – i.e. 24 h post mortem vs. 14 and 28 days post mortem kept at 1 °C) and final internal temperature on cooking ( T i, 65 and 80 °C) on the content of HAs in grilled steaks (two-plated grill, temperature of 220 °C) were studied. HA precursors (creatine, creatinine, and free amino acids) and ageing indicators, such as instrumentally measured colour values, pH ultimate values and length of myofibrilar fragments on raw and cutting values on grilled beef Longissimus dorsi muscles were determined. The muscles originated from eight commercially slaughtered Simmental bulls, 19–20 months old. The content of HAs was determined by a solid-phase extraction procedure. Meat ageing is accompanied by large changes in the chemical composition and structure of muscle tissues. In general, all the ageing indicators and precursors of HAs were influenced by ageing time at the 5% level or less. Creatine content declined significantly (non-aged: 6.00 mg g −1, 14 days: 5.82 mg g −1, and 28 days: 5.55 mg g −1) and creatinine increased with days of ageing (non-aged: 0.19 mg g −1, 14 days: 0.24 mg g −1, and 28 days: 0.26 mg g −1). Higher contents of total free amino acids were determined after 14 and 28 days of storage (28.18 μmol g −1 and 37.59 μmol g −1) than in non-aged beef (19.00 μmol g −1). In this study, two HAs were determined: MeIQx (2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline) and PhIP (2—amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine). The content of HAs increases with ageing. At lower T i, more MeIQx was formed; at higher T i, more PhIP was formed. MeIQx was present in all samples while PhIP was found only in samples grilled to higher T i. Samples treated to T i = 80 °C generally contained less HAs (non-aged meat: 0.20 ng g −1, 14 days: 0.26 ng g −1, and 28 days: 0.28 ng g −1) than samples treated to T i = 65 °C (non-aged meat: 0.19 ng g −1, 14 days: 0.36 ng g −1, and 28 days: 0.39 ng g −1) on account of MeIQx thermolability.

A 2‐Step Cooking Method of Searing and Hot Water Pasteurization to Maximize the Safety of Refrigerated, Vacuum Packaged, Chicken Breast Meat

Americans consume almost 40 kg per capita of chicken each year. Increasing consumption of chicken surpassed pork in 1982 and beef in 1992. The objectives of this study were to examine the effectiveness of a novel, 2-step cooking method of grilling, slicing, vacuum packaging, and hot water pasteurization to inhibit the growth of Listeria monocytogenes in chicken breast meat. Because this study required the use of pilot plant scale pasteurization equipment, Listeria innocua M1, a nonpathogen with slightly greater heat resistance than L. monocytogenes, was used as a surrogate. We first examined the lethal effects of grilling on a boneless skinless chicken breast to mimic cross-contaminated, surface-inoculated Listeria. Searing produced a mean reduction of 2.5 log CFU/g of Listeria and a moisture loss of only 7% (w/w). A 2nd experiment studied the lethal effect of pasteurization of the sliced seared chicken breast. L. innocua M1 inoculated between the slices mimicked contamination in deep muscle. Pasteurization in a 71 degrees C bath (final internal temperature of 66 degrees C) gave an additional 2.3 log CFU/g reduction. L. innocua M1 did not show significant regrowth during a wk of refrigerated storage. The combined 2-step cooking method of searing and pasteurization gave a combined 4.8 log reduction in LI M1. In parallel tests a non-Listeria indicator, Corynebacterium glutamicum, inoculated between sliced, seared chicken, showed a 3 log reduction after pasteurization for 10 min in a 71 degrees C bath compared to 2.3 log reduction of Listeria. Corynebacterium regrowth occurred much faster than did L. innocua M1.

The effect of whey protein concentrates and hydrocolloids on the texture and colour characteristics of chicken sausages

SummaryThe effects of fat reduction by increasing water content and the addition of whey protein and hydrocolloids on the instrumental texture profile, microstructure and water holding capacity of low‐fat chicken sausages were analysed. Low‐fat sausages were prepared with fresh breast chicken meat; in all formulations, a 3:7 ratio guar/xanthan gum was used. A factorial design with three levels of added fat (0%, 1.98% and 4.96%), two levels of whey protein concentrate (0.64% and 1.94%), and two levels of the hydrocolloids (0.13% and 0.32%) was applied. Samples were heat‐processed (73 °C final internal temperature) and, after cooling, chemical composition of the sausages was determined and scanning electron microscopic images were obtained. Colour was measured with a tristimulus reflectance colorimeter. Texture profile analysis of sausages was performed and the results were related to sample formulations. Extra‐lean products with a fat content lower than 0.5 g/100 g product showed very good quality attributes determined by a sensory panel.

Color of cooked ground beef patties is affected by cooking rate and post-cooking holding time (2006)

Two experiments investigated the effects of cooking rate and post-cooking holding time on the internal cooked color of ground beef patties. In Experiment 1, patties were cooked rapidly (1.8ºF/second) or slowly (0.4ºF/second). At temperatures below 180ºF, rapidly cooked patties were redder and appeared less well done than those cooked slowly. All slowly cooked patties appeared well done, even at unsafe final internal temperatures. In Experiment 2, patties were cooked rapidly and held for 1, 3, 6, or 12 minutes after cooking. Increasing the post-cooking holding time to 6 minutes after rapid cooking decreased pinkness and maximized well-done appearance. This allowed ground beef patties to be cooked to a lower temperature, likely preserving juiciness and flavor. Employing either a slow cooking rate or rapid cooking with a post-cooking holding time will foster a well-done appearance. Internal cooked color is not an adequate indicator of ground beef doneness. Only strict temperature control and monitoring can ensure product safety.

Storage stability of low-fat chicken sausages

Storage stability of low-fat chicken sausages formulated with fresh breast chicken meat with 0%, 2%, and 5% of added beef tallow was examined during 50-day refrigerated storage. The formulations also contained whey protein, guar and xanthan gums, NaCl, NaNO 2, ascorbic acid and sodium tripolyphosphate. Samples were heat-processed until a final internal temperature of 74 °C was reached, cooled, vacuum packaged and stored at 4 °C. Formulations showed good thermal stability, with process yields ranging between 94% and 97%, and purge losses less than 9.7% at the end of the study. Water activity slightly decreased during the first 28 days of storage and remained constant afterwards for all the tested samples, while pH and color parameters remained constant. As fat content increased a harder, more gummy and cohesive product was obtained, with higher chewiness and lower springiness and resilience values. Neither coliforms nor sulfite-reducing Clostridium were detected during the storage of the samples. Psychrotrophic lactic acid bacteria was the dominant microflora reaching levels lower than 7 log CFU/g after 50 days of storage at 4 °C. Formulated low-fat chicken sausages had acceptable sensory scores independently of the added fat. Extra lean products with very good stability and quality attributes were obtained.

Heat Stress From Enclosed Vehicles: Moderate Ambient Temperatures Cause Significant Temperature Rise in Enclosed Vehicles

Each year, children die from heat stroke after being left unattended in motor vehicles. In 2003, the total was 42, up from a national average of 29 for the past 5 years. Previous studies found that on days when ambient temperatures exceeded 86 degrees F, the internal temperatures of the vehicle quickly reached 134 to 154 degrees F. We were interested to know whether similarly high temperatures occurred on clear sunny days with more moderate temperatures. The objective of this study was to evaluate the degree of temperature rise and rate of rise in similar and lower ambient temperatures. In addition, we evaluated the effect of having windows "cracked" open. In this observational study, temperature rise was measured continuously over a 60-minute period in a dark sedan on 16 different clear sunny days with ambient temperatures ranging from 72 to 96 degrees F. On 2 of these days, additional measurements were made with the windows opened 1.5 inches. Analysis of variance was used to compare how quickly the internal vehicle temperature rose and to compare temperature rise when windows were cracked open 1.5 inches. Regardless of the outside ambient temperature, the rate of temperature rise inside the vehicle was not significantly different. The average mean increase was 3.2 degrees F per 5-minute interval, with 80% of the temperature rise occurring during the first 30 minutes. The final temperature of the vehicle depended on the starting ambient temperature, but even at the coolest ambient temperature, internal temperatures reached 117 degrees F. On average, there was an approximately 40 degrees F increase in internal temperature for ambient temperatures spanning 72 to 96 degrees F. Cracking windows open did not decrease the rate of temperature rise in the vehicle (closed: 3.4 degrees F per 5 minutes; opened: 3.1 degrees F per 5 minutes or the final maximum internal temperature. Even at relatively cool ambient temperatures, the temperature rise in vehicles is significant on clear, sunny days and puts infants at risk for hyperthermia. Vehicles heat up rapidly, with the majority of the temperature rise occurring within the first 15 to 30 minutes. Leaving the windows opened slightly does not significantly slow the heating process or decrease the maximum temperature attained. Increased public awareness and parental education of heat rise in motor vehicles may reduce the incidence of hyperthermia death and improve child passenger safety.

Cooking temperature effects on the forms of iron and levels of several other compounds in beef semitendinosus muscle

The influence of final cooked temperature on the form of iron present and on the concentration of taurine, carnosine, coenzyme Q 10 and creatine was investigated in surface and inner parts of 30-mm thick steaks from beef semitendinosus muscle ( n=6). The use of a fast, dry-heat cooking method with a Silex clam cooker (set at 200 °C) led to cooking times ranging from 5.6 to 8.6 min for final internal temperatures of 60 and 85 °C, respectively. The proportion of iron as soluble haem iron decreased from 65% in uncooked meat to 22% when cooked to 60 °C and then decreased more gradually with increases in final cooked temperature. The proportion of insoluble haem iron increased in a reciprocal manner, while changes in the proportions of soluble and insoluble non-haem iron were relatively small, but increases in the percentage of insoluble non-haem iron with increasing final temperature were significant ( P<0.01). Changes in the forms of iron with cooking generally took place more rapidly in surface samples than inner samples. On a dry-matter basis, concentrations of taurine, carnosine, coenzyme Q 10, and creatine all decreased with cooking, but the decreases were greatest for taurine and creatine. Losses of creatine were at least partly due to conversion to creatinine, and, along with the other compounds, probably included some loss in cooking juices. It is concluded that despite these changes with cooking, beef semitendinosus muscle remains a good source of iron and a useful source of the potentially bioactive compounds taurine, carnosine, coenzyme Q 10 and creatine.

Experimental Investigation of Drying Behavior of Carrots in a Fluidized Bed with Energy Carrier

AbstractA pilot scale fluidized bed dryer with inert particles as energy carrier was used to investigate the drying characteristics of carrot in this type of dryer. Glass beads, hollow steel balls and pieces of dry carrot were used as inert materials. The effects of sample diameter, inert material type, inert material diameter, amount of inert material, air velocity and temperature on the rate of drying were studied. It was found that the presence of inert particles enhances the rate of drying. The results of this study also revealed that, although the rate of drying increased with decreasing sample diameter, increasing of inert material thermal conductivity, and increasing of air temperature, but the inert material diameter and air velocity did not have any significant effect on the rate of drying. The independence of the rate of drying on air velocity in well fluidized systems, indicates that external diffusion is not the controlling step in this process. It was also found that the presence of inert materials caused the drying material to reach its final internal temperature more rapidly. The internal temperature of the drying material, also increased with increasing diameter and thermal conductivity of the inert materials.

Experimental and Theoretical Investigation of Drying of Carrots in a Fluidized Bed with Energy Carrier

A pilot scale fluidized bed dryer with an inert energy carrier (steel, glass beads ranging from 2.7 to 6.5 mm) was used to investigate the drying of carrots. The effects of sample diameter, inert material type, inert material diameter, amount of inert material, air velocity, and temperature on the rate of drying were studied. A mathematical model was proposed for predicting the drying rate and temperature of drying material. It was found that presence of inert particles enhance the rate of drying. The results of this study also revealed that, although the rate of drying increases with decreasing sample diameter, increasing the inert material thermal conductivity, and increasing air temperature, but the inert material diameter and air velocity have no significant effects on the rate of drying. The independence of rate of drying on air velocity especially in well-fluidized systems indicates that external diffusion is not a controlling step in this process. Also the presence of inert materials causes the drying material to reach more rapidly to its final internal temperature.

Influence of the formulation, cooking time and final internal temperature of beef hamburgers on the destruction of Listeria monocytogenes

The influence of the formulation, cooking time and final internal temperature of beef hamburgers on the destruction of Listeria monocytogenes was evaluated. Four hamburger formulations: 10% fat (F1), 20% fat (F2), 10% fat and 1.5% sodium chloride (F3) and 10% fat and 10.5% hydrated texturized soy protein (F4) were inoculated with a mixture of five strains of L. monocytogenes. Frozen hamburgers were cooked on a preheated electric griddle for 2, 4, 6, 8 and 10 min. Following removal from the griddle, hamburgers were held at room temperature for 1 min to simulate the time elapsed between cooking and consumption in commercial establishments, or they were immediately cooled. The results showed that the addition of 10.5% hydrated texturized protein had no effect on the lethality of the cooking process. However, the addition of 1.5% NaCl protected the bacterial cell against heat destruction. No conclusion could be made with respect to the effect of the increase in fat content (10–20%) in the meat. It was also shown that the increase in heating time and the additional “1-min period” at room temperature increased the lethality of the cooking process. Moreover, the results revealed a wide variability in the internal temperature of beef hamburgers at the end of cooking. These results revealed that control of the cooking process by the final internal temperature of hamburgers can be insufficient to ensure a safe product.

Effects of supplemental vitamin D3 on feed intake, carcass characteristics, tenderness, and muscle properties of beef steers.

Research was conducted to determine the effects of supplemental dietary vitamin D3 on DMI, carcass traits, Warner Bratzler shear (WBS) force, calpastatin activity, plasma minerals, pH (0, 3, 12, and 24 h after slaughter), water-holding capacity (WHC), and sensory characteristics of three muscles. Pre-slaughter vitamin D3 treatments included no supplemental vitamin D3, 6 x 106 IU (MIU) of vitamin D3 for 4 d, or 6 MIU of vitamin D3 for 6 d. Cattle were slaughtered and carcasses were chilled for 48 h before removal of steaks from the longissimus, gluteus medius, and biceps femoris muscles. Steaks were aged at 2 degrees C for 7, 14, or 21 d before cooking to a final internal temperature of 70 degrees C for WBS and sensory panel analysis. Dry matter intake was lower for steers supplemented with vitamin D3 for 4 or 6 d. Live and carcass weights were lower (P < 0.05) in steers supplemented with vitamin D3. Supplementing 6 MIU/6 d of vitamin D3 decreased (P < 0.05) WBS values of gluteus steaks (pooled over aging times). Longissimus steaks from steers supplemented with vitamin D3 for 6 d had lower (P < 0.05) WBS force values than these steaks from control steers or steers fed vitamin D3 for 4 d at 7 d postmortem. Biceps femoris steaks from steers receiving vitamin D3 for 4 d had higher WBS values than steaks from control steers at 14 and 21 d postmortem. Feeding vitamin D3 at 6 MIU for 6 d decreased (P < 0.05) the percentage of steaks that had WBS values > or = 3.86 kg for all steaks. Feeding vitamin D3 had no effect on palatability traits evaluated by trained panelists. Blood Ca concentrations were greater (P < 0.05) when vitamin D3 was fed and with increased vitamin D3 feeding time. Feeding vitamin D3 for 6 d (vs 4 d) delayed pH decline for all muscle types after 0, 3, and 12 h postmortem. Water-holding capacity was increased (P > 0.02) after 0 h, 24 h, and 21 d postmortem when vitamin D3 was fed and was greater at 0 and 24 h if vitamin D3 was fed for 6 d rather than 4 d. These data suggest that supplementing 6 MIU of vitamin D3 will decrease DMI and improve beef tenderness through increased blood plasma Ca concentrations and WHC.

Effectiveness of Two Cooking Systems in Destroying Escherichia coli O157:H7 and Listeria monocytogenes in Ground Beef Patties

A rapid, high-temperature double-sided grilling–broiling (DGB) system was compared to a single-sided broiling (SSB) system for cooking of foodservice ground beef patties to reduce microbial numbers and maintain textural quality. Patties (110g) containing either Escherichia coli O157:H7 or Listeria monocytogenes (106–7 CFU/g) were cooked to target internal temperatures of 60 or 68°C on each cooking system and immediately removed from the grills without the additional holding time at 60 or 68°C that is recommended for foodservice cooking of ground beef patties. Actual final internal temperature attained, position on the grill, degree of doneness, cooking time, after-cook weight, texture characteristics, and bacterial counts of the patties were monitored. The DGB reduced E. coli O157:H7 and L. monocytogenes populations in ground beef patties by 5.7 log10 and 5.4 log10 CFU/g, respectively, when cooked to a target temperature of 60°C (actual final internal temperature of 71.2°C) and by 6.1 log10 and 5.6 log10 CFU/g, respectively, when cooked to a target temperature of 68°C (actual final internal temperature of 75.8°C). The SSB reduced E. coli O157:H7 and L. monocytogenes populations by 1.3 log10 and 1.8 log10 CFU/g, respectively, when cooked to a target temperature of 60°C (actual final internal temperature of 62.7°C) and by 2.9 log10 and 3.6 log10 CFU/g, respectively, when cooked to a target temperature of 68°C (actual final internal temperature of 69.3°C). The DGB system effected a higher, more rapid temperature increase in patties cooked to either target temperature compared to the SSB system. This higher temperature was more effective in destroying pathogens in beef patties. Texture analyses determined that patties cooked on the DGB system had significantly higher values for springiness, adhesiveness, and product height as compared to the SSB system, and patties cooked on either system had significantly higher hardness, gumminess, chewiness, and product height values at the target temperature of 68°C as compared to 60°C.

Injection of beef strip loins with solutions containing sodium tripolyphosphate, sodium lactate, and sodium chloride to enhance palatability.

Beef strip loins (46 U.S. Choice loins and 49 U.S. Select loins) were used to evaluate the potential for enhancing beef tenderness, juiciness, and flavor by injecting fresh cuts with solutions containing sodium tripolyphosphate, sodium lactate, and sodium chloride. One half of each loin served as an untreated control, and the other half was injected with either distilled water (110% of raw weight) or a solution containing phosphate/lactate/chloride solution (107.5, 110, 112.5, or 115% of raw weight). All phosphate/lactate/chloride solutions were formulated to produce injected product concentrations of .25% sodium tripolyphosphate, .5% sodium chloride, and 2.5% sodium lactate. Ten additional U.S. Select loins were injected to 110% of raw weight with a phosphate-only solution (final product concentration of .25% sodium tripolyphosphate) for comparison with Select loins injected to 110% with phosphate/lactate/chloride and with distilled water. Steaks from each control and treated loin section were cooked to two final internal temperatures (66 degrees C and 77 degrees C) for sensory panel evaluation and shear force measurement. Injection of subprimal cuts with phosphate/lactate/chloride solutions improved tenderness (P < .05), juiciness (P < .05), and cooked beef flavor (P < .10) of strip loin steaks and was especially effective for maintaining tenderness and juiciness of steaks cooked to the higher final internal temperature. Injection of Select loins with a solution containing only sodium tripolyphosphate was not effective for improving beef tenderness or juiciness and tended to impart off-flavors characterized by sensory panelists as soapy and sour. Injection of fresh cuts with phosphate/lactate/chloride solutions could assist the beef industry's efforts to improve product quality and consistency.

THERMAL INACTIVATION OF ESCHERICHIA COLI 0157:H7 AND INTERNAL TEMPERATURE COMPARISONS IN THE COOKING OF GROUND BEEF PATTIES

Ground beef patties (114 g) inoculated with a five strain mixture of Escherichia coli 0157:H7 were cooked to six predetermined final internal temperatures (55C, 60C, 65C, 68C, 71C, 74C) in an electric skillet. The presence of verotoxin was then determined in enrichments of E. coli 0157:H7 in the patties. Visual clues including lack of pinkness in color of meat and in meat juices were also observed since consumers rely on them as indicators of doneness. No E. coli 0157:H7 or verotoxin was identified in ground beef patties cooked above 61.2C where the inoculum was below 5000 cfu/patty, the probable infective dose associated with previous outbreaks. E. coli 0157:H7 and verotoxin were detected in patties inoculated with 7.7x 105 CFU/patty even when cooked to 74C. As the final internal cooking temperatures increased, the internal color of the ground beef changed from red to pink to brown. Although we did not observe premature browning in our experiments others have documented its occurrence. Instructions for cooking should emphasize that lack of pinkness may be one clue to doneness but is not always reliable. Expressible meat juices always had some red or pink even when cooked to 74C suggesting that this is also not a good visual clue for doneness. In experiments comparing thermocouples and thermistors, taking internal temperatures of ground beef patties by inserting probes from the top, temperature readings varied by as much as 9C from the reference thermocouple. In contrast, when patties were probed from the side, readings were within 3C of each other from the reference. We suggest that doneness of ground beef patties be assessed with a thermocouple or thermistor inserted into the center of the patty from the side and the patty be removed from the heat only when a temperature of 71 C or higher has been reached.

Heat shock and thermotolerance of Escherichia coli O157:H7 in a model beef gravy system and ground beef.

Duplicate beef gravy or ground beef samples inoculated with a suspension of a four-strain cocktail of Escherichia coli O157:H7 were subjected to sublethal heating at 46 degrees C for 15-30 min, and then heated to a final internal temperature of 60 degrees C. Survivor curves were fitted using a linear model that incorporated a lag period (TL), and D-values and 'time to a 4D inactivation' (T4D) were calculated. Heat-shocking allowed the organism to survive longer than non-heat-shocked cells; the T4D values at 60 degrees C increased 1.56- and 1.50-fold in beef gravy and ground beef, respectively. In ground beef stored at 4 degrees C, thermotolerance was lost after storage for 14 h. However, heat-shocked cells appeared to maintain their thermotolerance for at least 24 h in ground beef held to 15 or 28 degrees C. A 25 min heat shock at 46 degrees C in beef gravy resulted in an increase in the levels of two proteins with apparent molecular masses of 60 and 69 kDa. These two proteins were shown to be immunologically related to GroEL and DnaK, respectively. Increased heat resistance due to heat shock must be considered while designing thermal processes to assure the microbiological safety of thermally processed foods.

Color of cooked beef patties as influenced by formulation and final internal temperature

Five separate formulations of ground beef patties were processed to represent differences in animal maturity, muscle pH, fat content and processing of hot vs cold boned beef. Patties were cooked on electric griddles to internal temperatures (thickest portion) of either 68.3 or 71.1 °C before making visual and instrumental assessment of color. High pH (> 6.2) muscle (whether obtained 48 h post-mortem or through hot processing) produced more red, uncooked color, while patties made from younger age (~36 months) cows (regardless of fat content) appeared more well-done. Patties processed from high pH (not hot processed) muscle had the highest saturation index and highest CIE a ∗ values (71.1 °C only), but still required the longest cooking times to reach final internal temperatures. Reductions in CIE a ∗ values between 68.3 and 71.1 °C temperatures were observed only for patties made from hot processed muscle. This may be related to the decrease in pH that occurred during the early stages of cooking for this formulation. Differences in color between the two internal temperatures were minimal with patties cooked to 68.3 °C possessing higher CIE b ∗, higher saturation index and lower hue angle values ( p ≤ 0.01). Inconsistent relationships between cooked color and internal temperature in cooked patties may result when broad differences exist in muscle pH and animal maturity between ground beef formulations.

Characteristics of High- and Low-Fat Bologna Sausages as Affected by Final Internal Cooking Temperature and Chilling Storage

A study was made of the effect that final internal processing temperature (63, 70 and 78°C) and chilling storage (2°C) exerted on the characteristics (cooking loss, purge loss, colour, Instron texture profile analysis) of high-fat (242 g kg -1 ) and low-fat (100 g kg -1 ) bologna sausage. High-fat sausages were harder and chewier than low-fat sausages. Lower fat contents were accompanied by a significant reduction in the cooking loss and purge loss. Binding properties were not affected (P > 0.05) by final internal cooking temperature. In general, Hunter colour parameter a values were higher in low-fat samples subjected to a high final internal cooking temperature than in those cooked up to only 63°C. High internal temperatures produced harder meat emulsions, an effect which was more pronounced in high-fat than in low-fat sausages. Cohesiveness and springiness of sausages was not affected (P > 0.05) by heat treatment. There were no major variations in textural parameters as a result of chilled storage.