Evaluation of Various Methods for Roasting Frozen Turkeys

Frozen turkeys were roasted to a lower than normal final temperature (71.1°C, 160°F) by one of the following methods: (1) foil tent, 93.3°C (200°F) oven; (2) foil wrap, 93.3°C (200°F) oven; (3) foil tent, 162.8°C (325°F) oven; (4) roasting bag, 176.7°C (350°F) oven; (5) foil wrap, 204.4°C (400°F) oven; or (6) microwave oven. Birds roasted by low temperature roasting methods received highest ratings for most attributes. Basted birds were preferred for all eating quality attributes. Microwave roasted birds reached final temperature fastest and with least energy consumption, but were rated low in appearance and eating qualities, and often had undesirably pink thigh joints. Turkeys inoculated with Salmonella typhimurium and Clostridium perfringens vegetative cells were essentially sterilized by all roasting methods. These methods can be considered as convenient alternatives to conventional roasting procedures.     

Fate of Listeria monocytogenes and Aeromonas hydrophila on Catfish Fillets Cooked in a Microwave Oven

Channel catfish fillets were inoculated with SJ lo⁶ cell/cm² each of Listeria monocytogenes and Aeromonas hydrophila and cooked in a microwave oven to internal temperatures of 55, 60, and 70°C. The fillets were either left uncovered or covered with polyvinylidene chloride films during cooking. A. hydrophila populations were reduced to nondetectable levels on covered fillets cooked to 70 °C. At 60 °C, L. monocyrogenes populatoins were reduced by = 4 logs for covered and by 2 logs for uncovered fillets. Covering fillets increased lethality at each temperature; however, some pathogens could survive at < 60 °C.     

Temperature Histories at Critical Points and Recommended Cooking Time for Whole Turkeys Baked in a Conventional Oven

Time-temperature histories and cooking times were determined for turkeys baked at 162.8°C from 4.44°C to an endpoint of 82.2°C in the thigh joint or breast. Turkeys (128) in five weight classes from 5.9 to 10.8 kg (0.9 kg increments) were equally divided into fresh, frozen, stuffed, unstuffed, and cooked shielded or unsheilded groups. The slowest heating point was either the wing joint or stuffing geometric center. Cooking time for unsheilded turkeys was 155 min plus 11 min/kg, unstuffed, and 200 min plus 8.8 min/kg, stuffed. Median cooking loss was 23%. Shielding of breasts prolonged cooking time. The cooking endpoint of 82.2°C in the thigh joint provided adequate lethality against Salmonella in the slowest heating points of both stuffed and unstuffed birds.     

Influence of Rapid Cooking Methods on the Survival of Trichinella spiralis in Pork Chops from Experimentally Infected Pigs

Pork chops (1.3, 2.5 or 3.8 cm thick) cooked to an internal temperature of 17 or 77°C by conventional oven, convection oven or flat grill contained no motile trichinae, whereas chops cooked to 66°C sometimes contained motile trichinae. Chops cooked by either charbroil or deep fat fry and pretreated in a microwave oven sometimes had motile trichinae even after cooking to an end point of 77°C. Chops, which had been frozen for 18 hr at -23°C and were thawed by microwave to 0°C then deep fat fried to an end point temperature, sometimes had infectious trichinae as confirmed by tests with rats and mice. Additional research is underway to verify the thermal death times and temperatures for T. spiralis larvae.     

The effect of different cooking procedures on microbiological and chemical quality characteristics of Tekirdaǧ meatballs

In this research, the effects of different cooking processes (grilling, oven, and microwave cooking) on microbial flora and chemical composition of the raw and cooked meatballs as consumed in Tekirdaǧ were investigated. Microbial flora of the raw meatballs was as follows: total bacteria, 6.02×10⁶ cfu/g; psychrophilic bacteria, 1.3×10⁵ cfu/g; yeast and mould, 2.4×10⁵ cfu/g; coliforms, 1.1×10⁵ cfu/g; Escherichia coli, 1.0×10² cfu/g; total staphylococcae, 3.3×10² cfu/g; Staphylococcus aureus, 85 cfu/g. While Salmonella was found in only one sample, none of the samples contained Clostridium perfringens. The cooking processes clearly decreased the microbial flora (2–3 log cycles in grilling (71°C) and oven‐cooked (79°C( 3–4 log cycles in microwave (97°C) heating) of the meatballs. However, because of the crust formation and high moisture losses from the meatball surface in microwave heating, some sensorial defects were observed in the final product. Also, fat and moisture losses were higher in microwave cooking compared to the other cooking processes. In conclusion, it is advised to use slightly higher temperatures than used in the grilling or conventinal cooking procedures to increase microbial quality of the meatballs studied in this research.     

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

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

Clostridium sporogenes and Listeria monocytogenes: Survival and Inhibition in Microwave-ready Beef Roasts Containing Selected Antimicrobials

Beef roasts were pumped with brines containing phosphates and acetic acid, sodium lactate, potassium sorbate, or glycerol monolaurin, and cooked in-the-bag once or twice to 62.8°C. Samples were examined during storage at 2, 5, and 10°C and after mishandling at 25°C for survival of inoculated Clostridium sporogenes spores and Listeria monocytogenes. Clostridia and listeriae survived one cooking when surface inoculated and two cookings in roasts inoculated internally. Lactate in brine afforded protection against clostridial survival and growth in temperature-abused roasts. Clostridia grew after 24 hr at 25°C in untreated roasts cooked once, and after 48 hr of abuse in most others except those with lactate or monolaurin. Listeria survival was reduced by lactate and monolaurin in recooked surface-inoculated roasts.     

Scanning Electron Microscopy, Proteolytic Enzyme Activity, and Acceptability of Beef Semitendinosus Cooked by Microwaves and Conventional Heat

Beef semitendinosus muscles cooked by conventional heat and microwave energy to endpoint temperatures of 40, 50, 60, and 70°C were evaluated for structural (scanning electron microscopy, SEM) changes, enzyme activity, and shear value. The 70°C samples were evaluated by sensory panel. As endpoint temperature increased, there were concomitant increases observable in SEM in intermyofibrillar spaces, fiber fragmentation, and occurrence of nonfibrous connective tissue. At 70°C, microwave samples were more fragmented, flattened, and coagulated than the conventional samples. Generally, enzyme activity of the muscle and drip decreased as end-point temperature increased. Conventional samples received higher sensory scores than microwave samples.     

Evaluation of 54° and 60°C Holding Temperatures on Aerobic Plate Counts and Coliform Determinations of Control and Post Cooking Contaminated Beef Roast

Fabricated beef roasts were cooked to an internal temperature of 60°C and the surface inoculated with a suspension of Escherichia coli at a level of lo⁶ cells/cm². Roasts were then stored in a warming oven at 54° and 60°C for 1, 2, 6, and 12 hr. Under these conditions the destruction of this strain of E. coli is quite rapid (less than 6 hr) at the 60°C holding temperature. The holding temperatures do allow the growth of thermoduric organisms naturally present in the product to initiate exponential growth after 6 hr at 54°C. The higher holding temperature reduced the rate of multiplication of the thermoduric organisms.     

The effect of temperature abuse on Clostridium perfringens and Bacillus cereus in raw beef and chicken substrates during frozen storage

Raw beef and chicken substrates inoculated with Clostridium perfringens and Bacillus cereus were subjected to severe temperature abuse at intervals during 6 months frozen storage. Clostridium perfringens grew in the thawing substrates at 20°C after one month but not after two months frozen storage. Substantial growth of Cl. perfringens and B. cereus occurred during 24 h of thawing at 27°C in chicken and beef substrates and this was maintained throughout frozen storage. Refreezing thawed samples reduced viable counts of Cl. perfringens and B. cereus by up to 99 and 97% respectively; non-growing cells of Cl. perfringens were much more resistant. Spores of Cl. perfringens and B. cereus were more resistant to prolonged frozen storage than vegetative cells.     

Growth of Clostridium perfringens spores inoculated in sous-vide processed Korean traditional Galbijjim under different storage conditions

To evaluate the microbiological safety of Korean traditional seasoned beef processed by sous-vide method, Clostridium perfringens spores were inoculated into the samples, and then germination and growth of spores were observed under different temperatures for days. Also, changes in pH, water activity, and salt contents were analyzed. As the results, there was no difference in water activity and pH of the samples during the storage at any temperature. However, salt contents of the samples significantly increased as storage time increased, and the storage temperature affected the change of salt contents. C. perfringens did not grow at 4 and 10°C for 24 days however, the bacterial growth was observed at 20°C after 2 days of storage. Based on these simulation tests, the microbiological safety of sous-vide processed galbijjim can be guaranteed at 4 and 10°C for 24 days even though the raw materials were contaminated by C. perfringens spores.     

Growth of Staphylococcus aureus in Cooked Potato and Potato Salad—A One‐Step Kinetic Analysis*

Staphylococcus aureus is a Gram‐positive spherically‐shaped bacterium capable of producing heat‐stable enterotoxins that cause acute gastrointestinal diseases. The growth of this pathogen in food is a major threat to public health worldwide. Potato salad is a frequent vehicle for infection and food poisoning caused by S. aureus. Therefore, the objective of this study was to investigate the growth kinetics of S. aureus in cooked potato and potato salad. Samples of potato cubes and potato salad inoculated with S. aureus were incubated at temperatures between 8 and 43 °C to observe its growth for developing growth models. No growth was observed at 8 °C. The experimental results showed that the growth curves did not exhibit lag phases, and can be described by a 3‐parameter logistic model. A one‐step kinetic analysis approach was used to simultaneously analyze all growth curves by direct construction of both the primary and secondary (Ratkowsky square root) models using nonlinear regression to minimize the global residual error. The estimated nominal minimum growth temperature of S. aureus was 6.12 °C in potato cubes and 8.80 °C in potato salad. The estimated maximum growth temperatures of S. aureus in potato cubes and potato salad were very close to each other (46.3 and 46.8 °C, respectively). On the average, the specific growth rates of S. aureus in potato cubes were approximately 70% higher than those in potato salad. This study suggests that cooked potato and potato salad should be stored below 6 °C or above 47 °C to prevent the growth of S. aureus. The mathematical models and kinetic parameters can be used to accurately evaluate the effect of temperature abuse on the growth of S. aureus and conduct risk assessments of S. aureus in cooked potato and potato salad.     

Assessment of Enterotoxin Production and Cross‐Contamination of Staphylococcus aureus between Food Processing Materials and Ready‐To‐Eat Cooked Fish Paste

This study evaluated Staphylococcus aureus growth and subsequent staphylococcal enterotoxin A production in tryptone soy broth and on ready‐to‐eat cooked fish paste at 12 to 37 °C, as well as cross‐contamination between stainless steel, polyethylene, and latex glove at room temperature. A model was developed using Barany and Roberts's growth model, which satisfactorily described the suitable growth of S. aureus with R²‐adj from 0.94 to 0.99. Except at 12 °C, S. aureus cells in TSB presented a lag time lower (14.64 to 1.65 h), grew faster (0.08 to 0.31 log CFU/h) and produced SEA at lower cell density levels (5.65 to 6.44 log CFU/mL) compare to those inoculated on cooked fish paste with data of 16.920 to 1.985 h, 0.02 to 0.23 log CFU/h, and 6.19 to 7.11 log CFU/g, respectively. Staphylococcal enterotoxin type A (SEA) visual immunoassay test showed that primary SEA detection varied considerably among different storage temperature degrees and media. For example, it occurred only during exponential phase at 30 and 37 °C in TSB, but in cooked fish paste it took place at late exponential phase of S. aureus growth at 20 and 25 °C. The SEA detection test was negative on presence of S. aureus on cooked fish paste stored at 12 and 15°C, although cell density reached level of 6.12 log CFU/g at 15 °C. Cross‐contamination expressed as transfer rate of S. aureus from polyethylene surface to cooked fish paste surface was slower than that observed with steel surface to cooked fish paste under same conditions. These results provide helpful information for controlling S. aureus growth, SEA production and cross‐contamination during processing of cooked fish paste.     

Effect of Rooibos (Aspalathus linearis) on Growth Control of Clostridium perfringens and Lipid Oxidation of Ready‐to‐Eat Jokbal (Pig's Trotters)

This study investigated the antimicrobial effects of rooibos (tea extract), potassium lactate (PL) and sodium diacetate (SDA) mixture alone or in combinations on the growth of Clostridium perfringens vegetative cell and spore in ready‐to‐eat (RTE) Jokbal (pig's trotters). Addition of a combination of 10% rooibos and 4% PL + SDA inhibit growth of C. perfringens vegetative cell in Jokbal at 24 °C and 36 °C. The significant inhibition on germination and growth of C. perfringens spores was also observed in Jokbal with a combination of 10% rooibos and 4% PL + SDA (PL: 2.24%, SDA: 0.16%) at 24 °C. The Jokbal treated with 10% rooibos and 4% PL + SDA mixture had significantly (P < 0.05) lower TBARS values than the control at 10 and 24 °C. The lipid oxidation inhibition effect was the highest (P < 0.05) in anaerobic packed Jokbal with 10% rooibos. The addition of a combination of 10% rooibos and 4% PL + SDA during the processing of Jokbal prevented the growth of C. perfringens and the germination and growth of C. perfringens spores at room temperature. This study shows rooibos tea as a valuable natural food preservative in meat products.     

Predictive model for growth of Clostridium perfringens during cooling of cooked ground pork

A predictive dynamic model for Clostridium perfringens spore germination and outgrowth in cooked pork products during cooling is presented. Cooked, ground pork was inoculated with C. perfringens spores and vacuum packaged. For the isothermal experiments, all samples were incubated in a water bath stabilized at selected temperatures between 10 and 51 °C and sampled periodically. For dynamic experiments, the samples were cooled from 54.4 to 27 °C and subsequently from 27 to 4 °C for different time periods, designated as x and y hours, respectively. The growth models used were based on a model developed by Baranyi and Roberts (1994), which incorporates a constant, referred to as the physiological state constant, q₀. The value of this constant captures the cells' history before the cooling begins. To estimate specific growth rates, data from isothermal experiments were used, from which a secondary model was developed, based on a particular form of Ratkowsky's 4-parameter equation. Using the data from dynamic experiments and the Ratkowsky model, an optimal value of q₀ (=0.01375) was derived minimizing the mean square error of predictions. However, using this estimate, the model had a tendency to over-predict relative growth when there was observed small amounts of relative growth, and under-predict relative growth when there was observed large relative growth. To provide more fail-safe estimates, rather than using the derived value of q₀, a value of 0.04 is recommended. The predictive model with this value of q₀ would provide more fail-safe estimates of relative growth and could aid producers and regulatory agencies with determining disposition of products that were subjected to cooling deviations.Industrial relevanceSafe time/temperature for cooling of cooked pork is very important to guard against the pathogen in cooked products. Predictive model will assist industry to determine compliance with regulatory performance standards and to ensure microbiological safety of cooked products.     

High pressure thermal processing for the inactivation of Clostridium perfringens spores in beef slurry

The spores of Clostridium perfringens can survive and grow in cooked/pasteurized meat, especially during the cooling of large portions. In this study, 600 MPa high pressure thermal processing (HPTP) at 75 °C for the inactivation of C. perfringens spores was compared with 75 °C thermal processing alone. The HPTP enhanced the inactivation of C. perfringens spores in beef slurry, resulting in 2.2 log reductions for HPTP vs. no reductions for thermal processing after 20 min. Then, the HPTP resistance of two C. perfringens spore strains in beef slurry at 600 MPa was compared and modeled, and the effect of temperature investigated. The NZRM 898 and NZRM 2621 exhibited similar resistance, and Weibull modeled well the log spore survivor curves. The spore inactivation increased when HPTP temperature was raised from 38 to 75 °C. The results confirm the advantage of high pressure technology to increase the thermal inactivation of C. perfringens spores in beef slurry.Industrial relevanceC. perfringens spores may cause food/meat poisoning as a result of improperly handled and prepared foods in industrial kitchens. Thermal processes at 100 °C or higher are generally carried out to ensure the elimination of these pathogenic spores. High pressure processing (HPP) is a food pasteurization technique which would help to maintain the sensorial and nutritional properties of food. Preservation of foods with HPP in conjunction with mild heat (HPTP) would enhance the spore inactivation compared to thermal processing alone at the same temperature, due to a known germination–inactivation mechanism. This technology, together with the application of Good Manufacturing Practices, including rapid cooling, is a good alternative to the traditional methods for producing safe processed meat and poultry products with enhanced sensory and nutritional quality.     

Effect of Poly- and Pyrophosphates on the Natural Bacterial Flora and Inoculated Clostridium sporogenes PA 3679 in Cooked Vacuum packaged Bratwurst

Survival and growth of inoculated Clostridium sporogenes PA 3679 and of natural aerobic and anaerobic bacterial flora were studied in cooked, vacuum packed bratwurst containing 0.5% phosphates during refrigerated (5°C) and subsequent temperature abuse storage (24°C). Sodium acid pyrophosphate (SAPP), sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP) and sodium polyphosphate glassy (SPG) were tested. No significant bacterial inhibition by any phosphate was observed during refrigerated storage, nor was there appreciable growth in the control bratwurst. However, SAPP significantly inhibited aerobic and anaerobic bacteria (including C. sporogenes) upon temperature abuse, followed in effect by TSPP and STPP. Cooking to 65.5°C helped retain antimicrobial properties of phosphates to some extent. Enzymatic hydrolysis of phosphates is postulated as a major factor in loss of antimicrobial properties of phosphates in processed meats.     

Evaluation of animal age and muscle type on beef log juice colour and residual GOT activity when cooked to target end-point temperature of 79.4 °C†

The effectiveness of the pink-juice test to determine 79.4 °C end-point temperature (EPT) of cooked beef logs was appraised. Logs made from five cuts of meat from three animal age groups were fabricated in triplicate to simulate products received at ports of entry and then cooked to EPTs of 78.0–81.8 °C. CIELAB L*, a*, b*, C and h ° values of internal surfaces of freshly sliced meat and pressed juices from samples were determined. Sensory ratings were made by six trained panelists to determine intensities of residual red color of the juices. Animal age and cut of meat had little effect on the CIELAB color values. Residual red color was apparent in all samples by both sensory and a* values analysis. Sensory ratings did not vary significantly (P < 0.05) by animal age or cut of meat. Average values of 3.2 (intensity range, 1–9) corresponded to an EPT slightly greater than 80 °C; absence of red color in the juices would therefore indicate an EPT in excess of the target temp of 79.4 °C. Residual glutamic-oxaloacetic transaminase activity (GOT) activity, used as a collateral test for EPT, ranged from 482.5 to 1641.8 SFU ml⁻¹ of juice and differed significantly by cut of meat (P < 0.05), but not by animal age. © 1999 Society of Chemical Industry     

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.     

Destruction of Trichinella spiralis During Cooking

Center cut chops (longissimus dorsi), 2.5 cm in thickness, from 31 pigs experimentally infected with Trichinella spiralis larvae and containing 37 ± 5 larvae per gram were cooked to a final internal temperature of 66, 71, 77 or 82° C by one of eight methods to determine their efficacy in killing encysted larvae. The results indicate that with the time and temperatures used in this study, some rapid methods of cooking pork chops that involved the use of a microwave oven did not completely destroy T. spiralis larvae at 77 or 82° C. The data also showed that cooking pork chops to an internal temperature of 77° C in the conventional oven, convection oven, flat grill, charbroiler or deep fat gryer did inactivate encysted T. spiralis larvae in pork chops.