Effect of pH and Total Pigment Concentration on the Internal Color of Cooked Ground Beef Patties

pH of ground beef components, from three purveyors, was measured for 150 consecutive days of production. Patties were produced from the components with pH values within the interval 5.6–6.2 and cooked (71°C) on a gas grill (176°C). The internal color of the cooked patties was described by a sensory panel. The internal color varied from grey in patties within the normal pH range (5.3–5.7) of muscle, to slightly red in muscles with a pH of 6.2. Red to pink cooked color was most intense inside those patties with the highest pH and the greatest concentration of total pigments. Bull meat exhibited a much higher pH and a greater level of total pigments than the other components studied. Controlling the pH of bull meat could be important in improving the cooking characteristics and quality of ground patties containing it. Purveyor specifications for bull meat should include pH as a criteria for purchase when cooking time and quality are critical to the customer.     

Effect of Freezing of Beef on Subsequent Postmortem Aging and Shear Force

Seventy-two steaks were used to determine effects of freezing postrigor muscle on aging of meat and shear force. Steaks were removed from each carcass 24 hr postmortem and aged at 2°C for 2 or 6 days; or frozen at ? 30°C for 27 days, thawed 24 hr and aged 2 or 6 days at 2°C. After aging, steaks were cooked and shear force determinations made. Aging of meat reduced shear force values; however, meat aged after freezing had lower (P < 0.03) shear force values than meat aged before freezing. Meat cooked after freezing had greater (P < 0.05) cooking losses. Freezing enhances the aging process and improves shear values of meat.     

The effect of oxygen exclusion during cooling of cooked turkey breast on the development of lipid oxidation in the stored product

In this study it was shown that cooling of freshly cooked turkey breast out of contact with air was highly effective in reducing the subsequent progress of lipid oxidation in the stored chilled (4 °C) product. Compared with cooling in contact with air, lipid oxidation in aerobically stored samples, as measured by muscle concentrations of hexanal and 2‐thiobarbituric acid‐reactive substances, was much lower for breast portions which were either cooled in a nitrogen atmosphere or subjected to hot vacuum packaging. Tissue hexanal concentrations of around 1.4 µg g^?1 muscle, which have previously been shown to be associated with the initial stages of sensory detection of oxidised off‐flavours, were reached after 5 and 3 days of storage respectively in nitrogen‐cooled/air‐stored and vacuum‐packed/air‐stored samples compared to only 1 day in breast portions which were cooled and stored in air. Cooling and storing under nitrogen had the effect of almost completely inhibiting lipid oxidation in samples stored for 7 days. An acceptable flavour shelf‐life of approximately 7 days with respect to lipid oxidation was achieved when vacuum‐packed breast portions cooked to an internal temperature of 85 °C were packaged before the core temperature fell below about 60 °C. © 2002 Society of Chemical Industry     

Sodium Tripolyphosphate Stability and Effect in Ground Turkey Meat

Ground turkey meat, cooked and uncooked, was prepared with and without 0.5% sodium tripolyphosphate (SIP) and stored at 5°C for different periods of time. STP stability was evaluated by determining soluble orthophosphate. Water-holding capacity (WHC), pH, and mi-crobial count were also measured. STP hydrolyzed rapidly in uncooked samples. Refrigerated storage time (up to 6 days) did not affect STP hydrolysis in cooked turkey meat. Heating accelerated the rate of STP hydrolysis. End point temperatures (65, 75, and 85 °C) did not affect the extent of STP hydrolysis. STP increased WHC in both cooked and uncooked samples. STP did not inhibit total microbial growth in cooked or uncooked ground turkey meat.     

Effect of Cooking on the Thermal Conductivity of Whole and Ground Lean Beef

The probe method was used to measure thermal conductivity of beef through a temperature range of 30–120°C. Thermal conductivity of beef increases with temperature up to 70°C followed by a decrease during the denaturation of proteins and subsequent loss of water. The thermal conductivity of beef again increases with temperature after protein denaturation. The thermal conductivity of cooked beef is lower than raw beef up to about 80°C. The rate of increase for cooked meat thermal conductivity is fairly constant with temperature at a given moisture content. Models based on composition and temperature were found to predict the thermal conductivity of meat during cooking at an average standard percent error of 7%.     

Binding of Meat Pieces: Influence of Some Processing Factors on Binding Strength and Cooking Losses

Evacuation of the chamber of the press used to form flaked beef into a restructured meat product (patty) did not affect the binding strength of the cooked patty but under some conditions decreased the cooking loss. In studies using patty mixes containing 0–1.0% added sodium chloride, meat binding strength increased with decrease in the temperature of the mix when formed into patties over the temperature range - 1° to -5°C. The largest effect generally occurred between - 1° and -2°C. However, the effect was only noted in patties that were frozen (-30°C) before being cooked for assessment. With decrease below - 1°C of the temperature of patties when pressed, cooking losses increased for the patties without added salt but decreased for those with added salt (0.5% or 1%). Change in the pressure applied to form the patty (in the range 1.4–13.7 MPa) can affect binding strength.     

Thermal inactivation of Salmonella spp. in ground chicken breast or thigh meat

Thermal inactivation of a four‐strain mixture of Salmonella spp. was determined in chicken breast and thigh meat. Inoculated meat was packaged in bags and then completely immersed in a circulating water bath and held at 55, 57.5, 60 and 62.5 °C for pre‐determined lengths of time. When the surviving bacteria were enumerated on tryptic soya agar supplemented with 0.6% yeast extract and 1% pyruvate (non‐selective medium), D‐values (time to inactivate 90% of bacteria) in chicken breast meat were 6.08, 4.77, 3.00 and 0.66 min at 55, 57.5, 60 and 62.5 °C, respectively; the values in thigh meat ranged from 11.48 min at 55 °C to 0.84 min at 62.5 °C. As expected, the measured heat resistance was lower when the recovery medium was selective (xylose lysine deoxycholate agar). Thermal death time values from this study will assist food processors in designing the HACCP plans to effectively eliminate Salmonella spp. in cooked chicken breast and thigh meat.     

Effects of Metmyoglobin Reducing Activity and Thermal Stability of NADH‐Dependent Reductase and Lactate Dehydrogenase on Premature Browning in Ground Beef

Premature browning is a condition wherein ground beef exhibits a well‐done appearance before reaching the USDA recommended internal cooked meat temperature of 71.1 °C; however, the mechanism is unclear. The objectives of this study were: (1) to determine the effects of packaging and temperature on metmyoglobin reducing activity (MRA) of cooked ground beef patties and (2) to assess the effects of temperature and pH on thermal stability of NADH‐dependent reductase, lactate dehydrogenase (LDH), and oxymyoglobin (OxyMb) in‐vitro. Beef patties (lean: fat = 85:15) were packaged in high‐oxygen modified atmosphere (HiOX‐MAP) or vacuum (VP) and cooked to either 65 or 71 °C. Internal meat color and MRA of both raw and cooked patties were determined. Purified NADH‐dependent reductase and LDH were used to determine the effects of pH and temperature on enzyme activity. MRA of cooked patties was temperature and packaging dependent (P < 0.05). Vacuum packaged patties cooked to 71 °C had greater (P < 0.05) MRA than HiOX‐MAP counterparts. Thermal stability of OxyMb, NADH‐dependent reductase, and LDH were different and pH‐dependent. LDH was able to generate NADH at 84 °C; whereas NADH‐dependent reductase was least stable to heat. The results suggest that patties have MRA at cooking temperatures, which can influence cooked meat color.     

Effect of shortening during cooking on the tenderness and histology of beef

In muscles which have gone into rigor at 15°C or 37°C without shortening, prevention of cooking shortening leads to greater toughness than in samples cooked free. This tenderness difference is not seen in cold shortened muscles. A histological study showed that heat shrinkage of collagen imposes an irregular “cooking crimp” in unshortened muscle, cooked free. This is quite distinct from cold induced crimp. Cooking cold shortened muscle under restraint completely removes the cold crimp. A striking “crossed-diagonal” orientation of the perimysial collagen in the cooked meat is described.     

Textural properties and water-holding capacity of broiler breast meat cooked to various internal endpoint temperatures

A total of 100 broiler breast meat was cooked at 176°C to internal temperatures of either 71, 73, 75, 77, or 79°C. Tenderness significantly decreased as internal temperatures increased. The decrease was most pronounced at 79°C with a 26.4% increase in Meullenet-Owens-Razor-Shear (MORS) energy compared to that at 71°C. The toughness-temperature coefficient (TTC, change in tenderness/1°C increase) was calculated to be 4.48% across the temperature ranges. Cooking loss increased constantly with the increase of internal temperatures and ranged from 15 to 27% across the range of endpoint temperatures. Poultry breast meat cooked to a higher internal temperature was in average less tender and also more variable in tenderness.     

Volatile Profiles of Raw and Cooked Turkey Thigh as Affected by Purge Temperature and Holding Time Before Purge

Effects of purge temperature and sample holding time on volatile profiles were determined using a purge-and-trap/gas chromatography unit with autosampler. Purge temperature and sample holding time before purge influenced the profile of volatiles in raw and cooked meat. The most notable changes were observed when the purge temperature was increased from 60°C to 80°C. Many of the changes in volatiles were related to oxidation of lipids. We recommend that meat should be purged at 40°C or 50°C (temperature at sensory analysis) to minimize heat-induced production of volatiles and sample purge should be done within 3h after sampling to reduce oxidative changes during sample holding time.     

Changes in the Tenderness of Meat Cooked at 50–65°C

Warner-Bratzler (WB) shear force values obtained for stretched veal muscles decreased as cooking temperatures were increased from 50 to 60°C. Increased proteolytic enzyme activity at these temperatures to give accelerated aging did not appear to explain the effects since there was still a substantial decrease in shear force with increase in cooking temperature from 50 to 60°C, even when well aged (7 wk at 5–6°C) meat and meat cooked for 24 hr was used. A more likely explanation was that, even at these relatively low temperatures, changes in connective tissue were involved since (a) the magnitude and direction of the change in shear force with increasing temperature was dependent on animal age and cooking time; (b) the effect of recooking at 80°C was dependent on animal age; and (c) the effects of increasing the cooking temperature and/or time on adhesion between the meat fibres was significantly greater for the samples from the younger animals.     

Effects of Frozen Storage and Cooking on Lipid Oxidation in Chicken Meat

Fresh chicken breast and leg meat samples, which were frozen for 3 months or 6 months at −18°C, were cooked in microwave and convection ovens and then tested for levels of lipid oxidation. After 6 months storage, malonaldehyde in fat from meat samples, as measured by a TBA assay, modified to avoid sample autoxidation, increased 2.5 fold, while the fluorescence excitation (360 nm) and emission (440 nm) spectra increased an average of 34%. Fat from meat cooked in a convection oven averaged 83% higher malonaldehyde concentration and 21% higher fluorescence compared to levels before cooking. Levels of lipid oxidation products in fat from chicken breast and leg meat were not significantly different in microwave compared to convection oven cooking; but certain secondary fluorescent products were higher in meats cooked by convection oven.     

The tenderness of cooked and raw meat from young and old beef animals

The shortening-toughness relationships for sternomandibularis muscles of young ox and large old bull have been compared. In both, toughness, measured by tenderometer, increases to a maximum at a shortening of 40%, and declines steeply from there at higher shortenings. This characteristic peaked relationship is obtained for ox and bull cooked both at 60 and 80 °C. However, toughness values for meat cooked to 60 °C are only about half those for meat cooked to 80 °C. In contrast to these similarities in the relationships for young and old animals, the rate of toughness increase with shortening in ox is considerably less than in bull. Thus toughness of ox at a given shortening and cooking temperature is considerably lower than that for bull, especially at high shortenings. A further distinction is made between the animals in that raw ox muscle does not give a peaked shortening-toughness relationship, whereas raw old bull does. The results have shown that for longissimus and sternomandibularis muscles a trained taste panel is only sensitive to variations in toughness in the lower half of the range of shear force values determined by tenderometer. In the light of this, live animal characteristics and muscle shortening are both important in determining toughness measured by taste panel.     

Oxidative stability of processed pork. Assay based on ESR-detection of radicals

The tendency to radical formation as an early event in lipid oxidation was used to characterise the oxidative stability of processed pork in an assay based on the spin trapping technique and electron spin resonance (ESR) spectroscopy. Pork cooked at different temperatures was evaluated, and it was found that heating at 95 °C resulted in higher radical formation than heating at 70 °C or at 120 °C. The tendency to formation of radicals (identified as carbon-centered radicals from the hyperfine coupling constants) was found to correlate with the rate of oxygen depletion as measured electrochemically, and the ESR assay should be further explored as a tool for the prediction of oxidative stability of meat products.     

Effect of High Temperature Conditioning on Beef from Grass or Grain Fed Cattle

Hereford by Angus heifers (n = 24) were fed grass or grain diets and slaughtered at 22 mo of age. The left side was chilled for 48 hr at 1°C while the right side was high temperature conditioned at 12 or 26°C for 3 hr and subsequently moved to the 1°C cooler. Meat from grass-fed heifers was darker in color, leaner and tended to be less tender than meat from gram-fed heifers. High temperature conditioning had no effect on carcass characteristics or cooked meat sensory attributes. Meat from the longissimus muscle was more tender and juicy than meat from the semitendinosus or semimembranosus.     

Cooking loss and juiciness of pork in relation to raw meat quality and cooking procedure

The study comprised two experiments with the aim to investigate the influence of raw meat quality and cooking procedure on cooking loss and juiciness of pork. The first experiment determined the cooking loss at 60, 70 and 80 °C centre temperature of 10 raw meat qualities (defined according to ultimate pH, drip loss, breed and rearing conditions) when cooked as steaks on a pan or as a roast in oven at a oven temperature of 90 or 190 °C. The differences in cooking loss between the raw meat qualities and the cooking procedures did decrease as the centre temperature increased and were almost negligble at 80 °C. Low water holding capacity (WHC) and low pH resulted in high cooking loss while no difference in cooking loss was observed between meat having medium or high WHC and pH. In the second experiment four raw meat qualities (standard, Duroc, low pH and heavy carcass weight) chosen from the first experiment to ensure a wide variation in cooking loss, were cooked in oven at 90 or 190 °C oven temperature. Juiciness was assessed three times during the chewing process. The results suggested that juiciness experienced initially in the chewing process depended only on the water content of the meat, whereas juiciness experienced later in the chewing process was determined by a combination of the water and intramuscular fat contents and the saliva production during chewing.     

Physical and Sensory Characteristics of Fresh Pork Leg Roasts Cooked at Low Temperatures

The effects of oven temperatures of 82, 93, 121 and 163°C were studied using 31 fresh pork leg roasts cooked to 74°C in oven bags. Warmed-over-flavor (WOF) was measured by sensory analysis after holding 3 hr at 68°C and after holding 24 hr at 2°C and then reheating to 68°C prior to serving. Roasts cooked at 82 and 93°C tended to have less WOF after refrigeration and reheating than roasts cooked at 121 and 163°C. Roasts cooked at 93°C had fewer aerobic mesophilic bacteria than those cooked at 121 and 163°C. In general, objective and sensory perception measurements indicated that roasts cooked at 82 and 93°C were of higher quality.     

Effect of pre-incubation conditions on growth and survival of Staphylococcus aureus in sliced cooked chicken breast

In this work, the effect of pre-incubation conditions (temperature: 10, 15, 37 °C; pH 5.5, 6.5 and water activity, a_w: 0.997, 0.960) was evaluated on the subsequent growth, survival and enterotoxin production (SE) of Staphylococcus aureus in cooked chicken breast incubated at 10 and 20 °C. Results showed the ability of S. aureus to survive at 10 °C when pre-incubated at low a_w (0.960) what could constitute a food risk if osmotic stressed cells of S. aureus which form biofilms survive on dried surfaces, and they are transferred to cooked meat products by cross-contamination. Regarding growth at 20 °C, cells pre-incubated at pH 5.5 and a_w 0.960 had a longer lag phase and a slower maximum growth rate. On the contrary, it was highlighted that pre-incubation at optimal conditions (37 °C/pH 6.5/a_w 0.997) produced a better adaptation and a faster growth in meat products what would lead to a higher SE production. These findings can support the adoption of management strategies and preventive measures in food industries leading to avoid growth and SE production in meat products.     

Effect of Albumen on TBA Values of Comminuted Poultry Meat

Fresh ground broiler meat was prepared and thoroughly mixed with 0, 5 and 10% raw or cooked albumen. The changes in TBA values for these ground meat-albumen mixtures were determined following storage at 2–4°C. Albumen reduced (P < 0.05) the TBA values of raw ground poultry meat but did not prevent carbonyl formation during storage. Raw albumen was more effective than cooked albumen. Adding albumen to ground poultry meat before oxidative cooking also decreased (P < 0.05) the amount of carbonyl volatiles produced.