Ingredient Effects on the Thermal Inactivation of Foot-and-Mouth Disease Virus in Formulated, Comminuted Meat Products

The stability of foot-and-mouth disease (FMD) virus after thermal processing of formulated comminuted beef products, such as, Salisbury steak, beef loaf and cured beef prepared from FMD-infected cattle, was examined. Virus survival after product processing in flexible plastic tubes varied with the ingredient present in the product formulation. The virus was completely inactivated in those products containing inorganic salts (sodium chloride, tripolyphosphate or nitrite), farinaceous material or spices after thermal processing to a core temperature of 79.4°C. In those formulated products that contained either FMDV virus-positive milk or heart tissue from infected cattle, the virus survived the above processing conditions. However, the virus was inactivated in these same products after processing to a core temperature of 93°C.     

Thermal Destruction of Listeria monocytogenes in a Meat Slurry and in Ground Beef

Thermal destruction of Listeria monocytogenes cells was determined in phosphate buffer, a meat slurry (20% ground beef/80% water) and in ground beef. D-values at 60°C, 65°C and 70°C in phosphate buffer, and in the meat slurry were 0.63, 0.29 and 0.15, and 2.54, 0.75 and 0.23 min, respectively. Heating of ground beef (80% lean) in a 75°C water bath to 50°C, 60°C or 65°C required 6.2, 8.4 and 10.6 min, respectively, and resulted in 0.2-0.9, 1.6-3.4 and 4.4-6.1 log reductions in L. monocytogenes cells, from the initial inoculation level of 8.08 log CFU/g. Viable cells were also detected after cold (21 days) or selective enrichment (24 hr) in eight out of nine samples of ground beef inoculated with 7.84-8.08 log CFU/g and cooked to 70°C.     

Proteins as Potential Endpoint Temperature Indicators for Ground Beef Patties

Ground beef patties were cooked to 63, 66, 68 and 71°C and 25g meat from the center of each patty was extracted. Changes in protein composition of extracts were monitored by sodium dodecyl sulfate-polya-crylamide gel electrophoresis, Western blotting and enzyme activity. Acid phosphatase, bovine serum albumin, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, phosphoglycerate mutase, and tri-ose phosphate isomerase concentration or activity decreased (P < 0.05) as endpoint temperatures increased. None of the enzymes was completely inactivated or insolubilized at 71°C. These proteins might be useful in assays to verify processing temperatures of ground beef patties.     

Effects of storage under a modified atmosphere on the microbiological and organoleptic qualities of ground beef prepared from pasteurized manufacturing beef

A 40‐kg lot of manufacturing beef, i.e. meat used for the production of ground beef products, was collected at a beef packing plant. The lot was divided into two batches. One batch was pasteurized by immersion in water at 85 °C for 60 s, the other batch was not pasteurized. Both batches were then ground. The ground meat was packed in overwrapped trays, which were master packaged under a modified atmosphere of 70% O₂ : 30% CO₂. The master packs were stored at 2 °C for up to 12 days. At the time of pack preparation and at 2‐day intervals, a master pack containing pasteurized and another pack containing unpasteurized meat, were opened and retail packs from each master pack were displayed at 4 °C for 3 days. Samples for microbiological analysis were obtained at the times of opening master packs and at the end of display. Displayed meat was assessed daily for colour, discoloration and retail appearance, and for odour intensity and acceptability at the end of display. After either a period of storage or a period of storage and display, the numbers of bacteria recovered from pasteurized meat were less than the numbers recovered from unpasteurized meat. The colour of pasteurized meat was perceived as being paler than that of unpasteurized meat, but discoloration was similar or less, and retail appearance was similar or better for pasteurized than unpasteurized meat at all times. The odours of displayed, pasteurized meat were generally somewhat less intense and more acceptable than those of unpasteurized meat. The findings indicate that pasteurization of manufacturing beef to improve the microbiological safety of ground beef provides a product of acceptable appearance and enhanced stability during storage under a modified atmosphere and subsequent display in air.     

Effect of Thermal Processing on the Survival of Foot-and-Mouth Disease Virus in Ground Meat

Foot-and-mouth disease virus was examined for its stability during cooking in tissues from infected cattle. The 0₁ (CANEFA 2) serotype of foot-and-mouth disease virus survived in lymph node tissues after heating for 2 hr at 69°C, for 1 hr but not for 2 hr at 82°C, and for 15 min but not for 0.5 hr at 90°C. Incorporation of 1% NaCl into suspensions of infected lymph nodes enhanced viral survival after heating for 0.5 hr but not for 1 hr at 90°C. The virus did not survive in either ground beef or meatballs contaminated with infected lymph node tissue, when processed to internal temperatures of 93.3, 96.1 or 98.8°C using commercial thermal processing procedures. Accurate temperature measurements were achieved with a temperature sensitive indicator disc developed in this study.     

Heat resistance of Escherichia coli O157:H7 in cook‐in‐bag ground beef as affected by pH and acidulant†

Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7.     

Electrical Stimulation and Hot Boning: Cooking Losses, Sensory Properties, and Microbial Counts of Ground Beef

Six batches of ground beef, approximately 10, 15, or 20% fat, were fabricated from flanks (lean and fat trim) of electrically stimulated-hot boned (ESHB) or conventionally chilled (CC) beef sides. Patties (2.5 × 7.6 × 8.2 cm) from each batch were modified broiled for 35 min at 177°C. Generally, ESHB and CC products were comparable in cooking and sensory properties and in microbial counts of raw products. ESHB products had slightly higher cooking losses, more intense beef flavor, and were slightly juicier than CC products. Small differences between ESHB and CC products more often were attributable to fat content than to processing treatment (ESHB or CC).     

Total Caloric Input of a Thermal Process as an Index of Lethality for Foot-and-Mouth Disease Virus

Because significant quantities of foot-and-mouth disease virus undetectable by cell culture infectivity assay can persist in infected tissues throughout thermal processing, classical methods for measuring virus inactivation are difficult to achieve. This study was undertaken to observe the lethality of a given process rather than determining a constant for process time for a given lethality. Thermal diffusivities (α) and one-dimensional heat flux (Q) were determined for three thermal processes used in processing of beef and pork products. Foot-and-mouth disease virus survived in ground beef cooked in flexible nylon thermal processing tubes to core temperatures of 63°C (892 kcal/ m²) in 1.2 hr and 71.2°C (1004 kcal/m²) in 1.45 hr; however, the virus did not survive after processing to a core temperature of 79.4°C (1363 kcal/m²) in 2.0 hr.     

GROWTH OF ESCHERICHIA COLI O157:H7 AND SALMONELLA SEROVARS ON RAW BEEF, PORK, CHICKEN, BRATWURST AND CURED CORNED BEEF: IMPLICATIONS FOR HACCP PLAN CRITICAL LIMITS

Small amounts (10–25 g; 6.3–20.8 cm² inoculated area) of raw ground beef, intact beef, pork and chicken (dark and white meat),and bratwurst and cured corned beef were inoculated with Salmonella serovars and Escherichia coli O157:H7, refrigerated 24 h at 5C, and then held either at 10C (± 1C) for up to 8 h or at room temperature (22C ± 2C) for up to 2 h. Except for a 0.2 log CFU increase in Salmonella serovars in ground beef during 2 h at room temperature, pathogens did not grow. Results of trials with commercial amounts of beef, pork, chicken, ground beef and bratwurst exposed to 10C for 8 h or 22C for 2 h also showed no pathogen growth. Potential critical limits for processing of previously refrigerated raw meat products are exposure temperatures between 5 and 10C for not more than 8 h or between 5 and 22C for not more than 2 h.     

Detection of Pork in Processed Meat by an Enzyme-linked Immunosorbent Assay Using Antiswine Antisera

An antiserum to autoclaved porcine muscle extract was raised in sheep and tested for the detection of pork in mixtures of pork in mutton (P/ S) or beef (P/B) heated at 70, 100, and 120°C for 30 min using a competitive enzyme-linked immunosorbent assay (ELISA) method. The results indicated that the antiserum detected low percentages of pork (1%) mixed in beef and in mutton (0.5%) even when the meat mixtures were heated at 70, 100 or 120°C for 30 min, which correspond to heat treatments of commercially processed meat products. Regression analysis showed a high positive correlation (r > 0.99) between absorbance (OD) values and different percentages of experimental or commercially processed P/B meat mixtures. It was concluded that the combination of anti-porcine sera raised in sheep and the ELISA method can be used for the detection of low percentages of pork in processed meats.     

Combined Treatments of Heat, Irradiation, and pH Effects on Infectivity of Foot-and-Mouth Disease Virus in Bovine Tissues

Various traditional methods for processing meat products were examined for their virucidal effects on the A, O, and C serotypes of food-and-mouth disease virus. Aging, curing, heating at 78°C for 20 min or irradiation (1.5 Mrad, 2.5 Mrad) that did not alter the sensory characteristics of the product were used singly or in combination. The only processing treatment that was virucidal was the combination of heat and gamma irradiation.     

Species identification by oligonucleotide hybridisation: the influence of processing of meat products

We have evaluated the influence of meat processing on the results obtained with a species identification test by DNA oligonucleotide hybridisation. Freezing and thawing of meat did not cause a substantial reduction in the hybridisation signal. Heating of meat at 100°C or 120°C, however, led to signal reduction caused by DNA degradation, but identification was still possible. The signal is highly influenced by the kind of tissues processed. Four extensively processed products with 50 g kg⁻¹ species admixtures were tested. Admixtures could be detected in three products but no hybridisation signal was observed with corned beef. We conclude that the quantification of admixtures by hybridisation is not better than with most alternative methods of species identification, as the strength of the signal depends on factors such as tissue origin and sample processing. © 1999 Society of Chemical Industry     

Thermal inactivation ofClostridium perfringensvegetative cells in ground beef and turkey as affected by sodium pyrophosphate

The heat resistance (55–65°C) ofClostridium perfringensvegetative cells in ground beef and turkey that included 0, 0.15 or 0.3% (w/w) sodium pyrophosphate (SPP) was assessed in bags heated using a water bath. The surviving cell population was assayed on tryptose–sulfite– cycloserine agar. The decimal reduction (D)-values in beef that included no SPP were 21.6, 10.2, 5.3, and 1.6min at 55, 57.5, 60, 62.5°C, respectively; the values in turkey ranged from 17.5min at 55°C to 1.3min at 62.5°C. Addition of 0.15% SPP resulted in concomitant decrease in heat resistance as evidenced by reduced bacterialD-values. TheD-values in beef that included 0.15% SPP were 17.9, 9.4, 3.5, and 1.2min at 55, 57.5, 60, and 62.5°C, respectively; the values in turkey ranged from 16.2min at 55°C to 1.1min at 62.5°C. The heat resistance was further decreased when the SPP level in beef and turkey was increased to 0.3%. Heating such products to an internal temperature of 65°C for 1min killed >8log₁₀cfug^-1. The z-values in beef and turkey for all treatments were similar, ranging from 6.22 to 6.77°C. Thermal death time values from this study should assist institutional food service settings in the design of thermal processes that ensure safety againstC. perfringensin cooked beef and turkey.     

Formation of amino-imidazo-azaarenes and carbolines in fried beef patties and chicken breasts under different cooking conditions in Korea

The effect of cooking temperature and time on amino-imidazo-azaarenes (AIAs) and carbolines in fried ground beef patties and chicken breast under different cooking conditions in Korea was evaluated. Beef patties were fried at different temperatures (150, 180, and 230°C) for 4, 8, 12, and 16 min per each side and then the amount of AIAs and carbolines was evaluated by solid-phase extraction and HPLC-MS analysis. In fried ground beef patties, formations of 9H-pyrido [3,4-b]indole (Norharman) and 1-methyl-9H-pyrido [3,4-b]indole (Harman) were dramatically increased at 230°C for 16 min. Concentrations of Norhanrman and Harman formed at 230°C for 16 min/side were 12 and 40 times greater than level those of Norharman formed at same cooking condition. In fried chicken breasts, 2-amino-3,7,8-trimethylimidazo[4,5-f] quinoxaline (7,8-DiMeIQx) and 2-amino-3,4,7,8-tetramethylimidazo[ 4,5-f]quinoxaline (Tri-MeIQx) were not found at 150 and 180°C. Norhanrman formed at 230°C for 16 min was approximately 4 times higher than fried chicken breasts at 180°C. These results suggest that increase of cooking temperature and time was directly affected on AIAs and carbolines formation in Korean cooked meat.     

Enhanced Thermal Resistance of Salmonella in Whole Muscle Compared to Ground Beef

Irradiated beef (whole ‐muscle and ground product with identical fat, protein, and moisture composition) was exposed to a Salmonella‐ inoculated marinade and heated in brass tubes in a water bath at 55 °C, 60 °C, and 62.5 °C. The bacterial load and thermal lag time were similar (α= 0.05) for both whole and ground muscle; therefore, all samples had equivalent composition, inoculation levels, and thermal histories. Assuming 1st‐order kinetics, the inactivation rate constants (k values) in whole muscle were 50% lower than those in ground product at each temperature (P = 0.0001), and Arrhenius‐type models described the temperature dependency of k (R² > 0.95). Because thermal processing regulations are generally based on ground product studies, thermal process validations for meat and poultry products may need to consider the physical state (whole ‐muscle versus ground) of the product being manufactured.     

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.     

Transaminase (AST/GOT and ALT/GPT) Activity in Ground Beef as a Means of Determining End-point Temperature

Thermal processing conditions [rate of temperature increase, 0.35°C or 3.5°C/min; end-point temperature (EPT), 57.2, 71.1, and 79.4°C; dwell time, 0 and 30 min; and enzyme extraction medium (deionized water, 0.9% saline, and pH 7 buffer)] affected glutamic oxalacetic transaminase (GOT; aspartate aminotransferase, E.C. 2.6.1.1) and glutamic pyruvic transaminase (GPT; alanine aminotransferase; E.C. 2.6.1.2) activity in thermal treated ground beef samples. There was greater loss of GOT activity in samples heat processed at 0.35°C/min than samples heat processed at 3.5°C/min with depletion nearly to zero between 71.1 and 79.4°C. More GOT activity was noted when samples were extracted with 0.9% saline solution. GPT activity was low in all samples and was present after heating to 79.4°C.     

Effect of Heat Treatment for Trypsin Inhibitor Inactivation on Physical and Functional Properties of Peanut Protein

Trypsin inhibitor (TI) inactivation in whole peanut kernels exposed to moist heat had a decimal reduction time (D) of 91 min at 100°C and 9.3 min at 120°C. When all processing times were converted to process time at 120°C using Z of 20°C, the composite D at 120°C was 10 min. Solubility decreased with heating to reach a minimum with 98% TI inactivation. Capacities to spontaneously absorb water and to gel were retained better on heating at 120°C than at 100°C for equal TI inactivation. The most functional protein was in kernels heated at 120°C for 10 min. When 20 or 30% meat protein in a meat loaf formulation was replaced with the latter peanut protein, the resulting loaf retained more fat and water and exhibited higher shearing strengths than all meat formulations.     

EFFECTIVENESS OF CARNOBACTERIUM PISCICOLA LK5 FOR CONTROLLING THE GROWTH OF LISTERIA MONOCYTOGENES SCOTT A IN REFRIGERATED FOODS1

The potential for controlling the growth of Listeria monocytogenes in refrigerated foods using Carnobacterium piscicola LK5, a bacteriocin-producing strain originally isolated from raw ground beef, was studied using co-culture techniques. Eight foods, including UHT milk, canned “all-beef”dog food (cooked meat), raw ground beef, irradiation-sterilized raw ground beef, chicken roll, pasteurized crabmeat, canned creamed corn, and frankfurters, were inoculated with 10³ cfu/g L. monocytogenes Scott A, with and without 10⁴cfu/g LK5, and incubated at 5 and 19C. Samples were removed periodically and assayed for total aerobic plate count using Brain Heart Infusion Agar and L. monocytogenes using Vogel-Johnson Agar or Modified Vogel Johnson Agar. The growth of L. monocytogenes was suppressed in milk, dog food, crabmeat, creamed corn, and frankfurters stored at 5C. The microorganism was less inhibitory at 19C. In sterile raw ground beef, LK5 inactivated the pathogen at 5C and prevented its growth at 19C. No activity attributable to LK5 was observed in refrigerated nonsterile ground beef or chicken roll; however, these products did not support the psychrotrophic growth of the pathogen even in the absence of LK5. LK5 was most effective in products where the background microflora was reduced by either thermal processing or irradiation treatment. The results indicate that C. piscicola LK5 has potential as a means for preventing the growth of L. monocytogenes in a variety of refrigerated food products.     

Cure Levels, Processing Methods and Meat Source Effects on Low-fat Frankfurters

Frankfurters were manufactured from lean meats (100% beef and 50:50 beef-pork) to contain reduced levels of fat (about 1.3%). A curing solutibn was added to yield 160% of fresh meat weight. Three processing methods, coarse ground tumbled, fine ground tumbled and fine ground emulsified were used. All products were cooked in live steam to 71°C internal temperature. Product yields, penetrometer values, color, chemical composition, caloric content and added water were evaluated. Emulsified frankfurters from 50:50 beef-pork mixtures at 160% cure had texture similar to conventional product as well as increased (P<0.05) yields, acceptable color and 74% fewer calories.