GROWTH OF STAPHYLOCOCCUS AUREUS AND ENTEROTOXIN A PRODUCTION IN FOODS CONTAINING POLYPHOSPHATES

Effects of pyro-, tripoly- and hexametaphosphates (0.5 and 1%, w/w) on growth of Staphylococcus aureus strain 196E and enterotoxin A (SEA) production were studied in cooked custard and beef at 22 and 30°C. No effect was observed in custard, where cell numbers/g increased from 10³ to 10⁸ and SEA reached 4.2 ng/g after 48 h at 22°C, irrespective of treatment. Cell numbers in cooked beef were ca. 10⁹/g after 48 h, and reduced numbers (by 1.5–2 log cycles) were found in samples containing 0.5 and 1% pyrophosphate during incubation at 22%, but not at 30°C. SEA concentrations in beef were 28 ng/g after 48 h at 22°C, and 93 and 184 ng/g after 24 and 48 h, respectively, at 30°C. SEA concentration correlated with amount of growth, and was nondetectable when cell numbers were ± 10⁶/g. Reduction of the meat pH by sodium acid pyrophosphate contributed to the observed inhibitory effect.     

MICROBIOLOGICAL STATUS OF BEEF CARCASS MEAT IN INDONESIA

The microbiological status of beef carcass meat was investigated at a traditional and a semi-modern abattoir in Indonesia. Carcasses from the traditional abattoir were generally less contaminated than those from the semi-modern abattoir. The average total aerobic viable bacterial count of carcasses produced at the traditional abattoir, (log₁₀ 3.62/cm²) was found to be significantly lower (p = 0.02) at the semi-modern abattoir (log₁₀ 4.02/cm²). More than 70% of carcasses at both abattoirs were found to be positive for Escherichia coli (> 10 organisms/cm²), while Salmonellae were found on approximately 15% of carcasses at both locations.     

Storage characteristics of sous vide cooked roast beef

The technological, microbiological, and sensory storage characteristics of low temperature sous vide cooked roast beef were investigated. the effect of two heat treatments, 59°C (P₇₀¹⁰in core 8.4) and 62°C (P₇₀¹⁰ in core 15.9) on the stability of spiced roast beef made from Musculus semitendinosus with a high initial microbial load were compared as well as storage temperatures of 2 and 10°C. Although chilling baths with circulating water were used, recommended chilling rates for sous vide products could not be attained. Yield was significantly higher at 59°C and at a storage temperature of 2°C but decreased during storage. At 62°C the meat became significantly more tender than at 59°C as measured by shear force. No differences in microbiology were observed between heating regimes. At low storage temperature products were microbiologically stable over a 35-day period. At 10°C, however, a rise in psychrotrophic aerobic counts and occasional pack swelling was observed. In a commercial scale experiment conducted with sous vide cooked (62°C) beef with low initial counts, no increase in aerobic counts was observed at 2, 5 and 10°C while swelling occurred in 28% of the packages stored at 10°C and in none at 2 and 5°C. the swelling was due to different types of gas-producing clostridia. Warmed-over flavour (as TBARS) showed no development during storage in intact packages, while slicing and serving the roast beef under commercial conditions resulted in a marked increase to < 100 μmole kg⁻¹. In spiced roast beef only minor changes in off-odour and off-flavour of the product were observed during 23 days of storage at 2°C.     

Effect of irradiation and modified atmosphere packaging on the microbiological safety of minced pork stored under temperature abuse conditions

The safety of irradiated pork packed in 25% CO₂:75% N₂ and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens . Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of 10² cells g^-1. When higher inoculum levels were used (10⁶ cells g^-1) irradiation at 1.75 kGy reduced pathogen numbers by 1 –>5 log₁₀ cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.
In all cases when high numbers (10⁶ to 10⁷g^-1) of spoilage and/or pathogenic bacteria were present initially on the pork the meat appeared spoiled, and although irradiation reduced the number of microorganisms, the meat was still unacceptable from a sensory viewpoint after treatment.
It was concluded that the microbiological safety of irradiated, modified atmosphere packaged (MAP) pork is better than that of unirradiated MAP pork.     

Rapid dye reduction tests for the determination of microbiological quality of meat

Rapid dye reduction tests have been developed to determine the quality of meat. Three chemical indicators, resazurin and two tetrazolium compounds, were used to correlate the microbial numbers and reduction times in meat samples. Twenty-five surface samples from sheep carcasses were subjected to each reduction test. Total viable counts given were obtained at 37°C. Resazurin reduction time was 90–120 min when the bacterial counts ranged from 1.5×10⁶ to 7.7×10⁶/cm². Samples showing bacterial counts between 1.5×10⁶ and 6.0×10⁶/cm² reduced tetrazolium (NBT) in 360–390 min whereas samples containing bacterial counts of 2.1×10⁶/cm² took 420–450 min to reduce iodophenyl nitrophenyl tetrazolium (INT) dye. Regression equations relating the number of organisms per cm² and reduction time were applied to predict the microbiological quality of meat samples from reduction time data. Among the three dyes, resazurin gave the lowest reduction time.     

Lead and cadmium in meat and meat products consumed by the population in Tenerife Island, Spain

The aim of this study was to determine the levels of lead and cadmium in chicken, pork, beef, lamb and turkey samples (both meat and meat products), collected in the island of Tenerife (Spain). Lead and cadmium were measured by graphite furnace atomic absorption spectrometry (GFAAS). Mean concentrations of lead and cadmium were 6.94 and 1.68 µg kg^-1 in chicken meat, 5.00 and 5.49 µg kg^-1 in pork meat, 1.91 and 1.90 µg kg^-1 in beef meat and 1.35 and 1.22 µg kg^-1 in lamb meat samples, respectively. Lead was below the detection limit in turkey samples and mean cadmium concentration was 5.49 µg kg^-1. Mean concentrations of lead and cadmium in chicken meat product samples were 3.16 and 4.15 µg kg^-1, 4.89 and 6.50 µg kg^-1 in pork meat product, 6.72 and 4.76 µg kg^-1 in beef meat product and 9.12 and 5.98 µg kg^-1 in turkey meat product samples, respectively. The percentage contribution of the two considered metals to provisional tolerable weekly intake (PTWI) was calculated for meat and meat products. Statistically significant differences were found for lead content in meats between the chicken and pork groups and the turkey and beef groups, whereas for cadmium concentrations in meats, significant differences were observed between the turkey and chicken, beef and lamb groups. In meat products, no clear differences were observed for lead and cadmium between the various groups.     

THE QUALITY CHARACTERISTICS OF M. LONGISSIMUS FROM HANWOO (KOREAN CATTLE) WITH DIFFERENT FLOOR SPACE

The quality characteristics of Musculus longissimus from Hanwoo bulls with different floor space were studied. Fifteen heads of bulls were randomly divided into three groups (9, 18 and 27 m²). At 48 h postslaughter, samples were collected and stored at 4  ±  0.5C for 9 days. The n6 / n3 polyunsaturated fatty acid of the meat from cattle in 27 m² was significantly lower ( P <  0.05) than that in other groups. The meat of cattle in 27 m² contained more C20:5 n-3 eicosapentaenoate (EPA) ( P <  0.05) than the meat from cattle in 9 m². The pH value and drip loss of the meat from cattle in 27 m² were significantly higher ( P <  0.05) than those in other groups. The 2-thiobarbituric acid reactive substances and peroxide values of the meat from cattle in 27 m² were significantly lower ( P <  0.05) than those in other groups at 6 and 9 days of storage. The increasing floor space from 9 to 27 m² improved the fatty acid composition, water-holding capacity and lipid stability of the meat.

PRACTICAL APPLICATIONS

Meat quality is one of the important values related to human well-being. Floor space is one of the important factors in animal welfare that affect beef quality. Increasing the floor space from 9 to 27 m² for bulls during the finishing period had improved the meat quality, especially in respect to fatty acid composition, water-holding capacity and lipid oxidation resistance.     

Selenium content in selected products of animal origin and estimation of the degree of cover daily Se requirement in Poland

The aim of the study was to determine Se concentration in selected products of animal origin (dairy products, pork, beef, chicken, giblets, fish, eggs) and to estimate the degree to which these products cover daily Se requirement in humans. Selenium concentrations were determined using the spectrofluorometric method. Mean Se concentration in the milk, yoghurt, kefir, and probiotic drinks was 0.020 μg mL⁻¹, 0.010 μg mL⁻¹, 0.012 μg mL⁻¹ and 0.012 μg mL⁻¹, respectively. Selenium concentration in cheese ranged 0.022–0.088 μg g⁻¹ wet weight. The average selenium content of meat ranged from 0.064 (beef) to 0.094 (chicken) μg g⁻¹ w.w. The mean Se content of giblets (liver: 0.307–0.401 μg g⁻¹ w.w.) was significantly ( P  < 0.05) higher than in meat. The concentration of Se depends on fish species and in our study it ranged from 0.136 ± 0.023 (flounder) to 0.282 ± 0.024 μg g⁻¹ w.w. (mackerel). The results obtained show that the analysed food provides 22.8% of the daily selenium requirement. Considering that animal products account for 40–45% of the diet daily selenium intake averages 33–37 μg.     

Ozone treatment of chilled beef

Summary. The initial specific rate of ozone decomposition by muscle was 1.02 ± 0.23 m/hr, for tissue stored at 0.3°C and equilibrium relative humidities (EH) of 99.3, 98.5 or 98.0% in air with ozone concentrations between 0.15 and 38.3 mg/m³, or in air-ozone mixtures containing 11% CO₂. the value was not affected by the presence or absence on the muscle surface of meat spoilage bacteria, yeasts or moulds but considerably lower values were obtained for lean and high fat surface tissues (0.44 and 0.31, respectively).
The slope α of the linear course of the logarithm of reaction velocity-time curves was a power function α= - 9.74 10^-4[O₃]^1.54 for ozone concentrations [O₃] 5 mg/m³. the slope was not significantly different from zero when muscle of EH 98.5% was exposed to 0.7 mg/m³ ozone, but significant values were determined when muscle had an EH of 98.0, and also when tissue (EH 99.3%) was exposed to ozone concentrations > 0.7 mg/m³. Values of α determined for surface tissue and muscle tissue were not significantly different when the same treatment was applied.     

DISPLAY LIFE OF FRESH BEEF CONTAINING DIFFERENT LEVELS OF VITAMIN E AND INITIAL MICROBIAL CONTAMINATION

Strip loins from beef cattle fed diets supplemented or not supplemented with α-tocopheryl acetate (vitamin E; 500 IU·animal⁻¹·d^-1) were fabricated into steaks inoculated at three initial levels (1.7 to 1.9; 2.3 to 2.5; 6.4 to 7.1 log CFU/cm²) of bacterial contamination (from over aged retail steaks) and evaluated for psychrotrophic plate counts (PPC), overall appearance and color during 6 days of simulated retail display (0 to 4C). Initial contamination affected changes in PPC (P < 0.05) during display, while the highest level of initial contamination eliminated benefits of high vitamin E concentrations on product color within 4 days of retail display. However, increased vitamin E concentrations in steaks were associated with higher (P < 0.05) CIE a* values appearance scores when the level of initial contamination was less than 2.5 CFU/cm². Results indicated that vitamin E supplementation does not mask high levels of bacterial contamination.     

PRESSURE-INDUCED SOLUBILIZATION OF MEAT PROTEINS IN SALINE SOLUTION

Under some conditions, pressures of the order of 100 mega-newtons/meter² (MNm⁻²) applied to homogenates of ovine meat in 0.5M sodium chloride solution were found to give about a threefold increase in the yield of salt-soluble protein. At pressures of about 70 MNm⁻²the water-holding capacity (WHC) of homogenates of meat from some carcasses was increased. The effect of pressure on protein solubility was dependent on meat concentration in the homogenate (pressure was ineffective at high meat concentrations); duration of pressurization; and pH (being most effective in the pH range 5.3–7). The pressure-induced solubilization of meat proteins is assumed to occur via an ionic mechanism.     

Role of biogenic amines as index of freshness in beef meat packed with different biopolymeric materials

The main objectives of this work were to evaluate the chemical and microbiological fresh beef meat quality packed in aerobic atmosphere with biopolymers, to investigate the possible role of biogenic amines (BAs) as indicators of spoilage in fresh beef meat stored at 4 °C for 8 days. The results of this research highlighted that for fresh meat packaging it could be possible to replace the PS tray/PVC film system, with an expanded PLA biopolymeric tray heat-sealed with a biopolymeric film, characterized by a negligible environmental impact in comparison with the use of synthetic plastic materials. The storage time differentiated the meat samples on the basis of pH and microbiological characteristics. With regard to BAs, tyramine and cadaverine resulted strongly influenced by the storage time, and to a less extent putrescine and spermidine. Tyramine and cadaverine could be used as spoilage indexes of fresh beef meat chilled and packed in aerobic atmosphere with biopolymers.     

INACTIVATION OF BACTERIAL SPORES BY COMBINED ACTION OF HYDROSTATIC PRESSURE AND BACTERIOCINS IN ROAST BEEF

Foodborne bacterial spores are normally resistant to high hydrostatic pressure; however, at moderate pressure, they can be induced to germinate and outgrow. At this stage, they can be killed by bacteriocin-based biopreservatives (BP-containing pediocin and nisin at 3:7 ratio; BP_X, BP + 100 μg/mL lysozyme; BP_Y, BP_X+ 500 μg/mL Na-EDTA). Based on this principle, spores of the meat spoilage organism, Clostridium laramie (1–2 × 10² spores/bag) alone or a mixture of four clostridial spores (5 × 10³ spores/bag), Clostridium sporogenes, Clostridium perfringens, Clostridium tertium, and Clostridium laramie, were inoculated in roast beef in the presence of 5000 AU/g of bacteriocin-based biopreservatives. The roast beef samples were subjected to hydrostatic pressure (HP) at 345 MPa for 5 min at 60C and stored at 4 or 12C for 84 days or at 25C for 7 days. The HP treatment of roast beef samples inoculated with a mixture of clostridial spores could be stored for 42 days at 4C. The HP in combination with either BP_X or BP_Y extended the shelf-life of roast beef up to 7 days at 25C. The combined treatment of HP and BP controlled the growth of C. laramie spores and extended the shelf-life of roast beef for 84 days when stored at 4C.     

MICROBIOLOGICAL STATUS OF EGYPTIAN SALTED MEAT (BASTERMA) AND FRESH SAUSAGE

The microbiological quality of 125 samples of the most popular Egyptian meat products (75 Egyptian fresh sausage "EPS" and 50 basterma) was determined. The aerobic plate count (APC) and Lactobacillaceae count of basterma ranged from 1 × 10⁴ to 9 × 10⁶ CFU/g, respectively . Enterobacteriaceae, mold and yeast counts for basterma were similar (<1 × 10² CFU/g). Artificially contaminated slices of meat and garlic paste of basterma showed that the paste inhibited growth of Salmonella typhimurium. APC and Enterobacteriaceae counts of EFS ranged from 1.1 × 10⁴ to 1 × 10⁸ and from 1 × 10² to 1 × 10⁷ CFU/g, respectively. Nearly 26% and 29% of EFS were positive for Clostridium perfringens and coagulase-positive Staphylococcus aureus, respectively . Salmonella could not be detected in any examined samples. Bacteriologically, EFS might pose a potential health hazard, making it imperative to institute sanitary measures during its production and sale .; Accepted for Publication July 2, 1997     

CALCIUM CHLORIDE EFFECTS ON TBA VALUES OF COOKED MEAT

Ground chicken breast and beef top round (semimembranosus) muscles were treated with CaCl₂ (0.05, 0.10, 0.15, and 0.20% on final sample weight basis) and cooked to an internal temperature of 80C. Cooked samples were aerobically stored at 4C for 0 or 4 days and analyzed for 2-thiobarbituric acid (TBA)-reactive substances. Results indicated that CaCl₂ can either inhibit or accelerate lipid oxidation in cooked meat depending on its concentration/meat animal species. TBA values of chicken samples were decreased by CaCl₂ used at ≥ 0.1% of final weight. However, only beef samples treated with the highest CaCl₂ level (0.20%) tended to have lower TBA values when compared to control samples (treated with deionized water only). CaCl₂ used at low levels (0.05% for chicken and ≤0.15% for beef) tended to elevate cooked meat TBA values.     

PENETRATION OF SUBSTANCES INTO MUSCLE

The rate and depth of penetration of two dye markers, hematoxylin and eosin, into beef muscle were compared. The effects of temperature, aging, meat texture, and type of muscle were investigated. Samples (1 cm³) were placed into dye markers, and then were sectioned at selected time intervals and examined microscopically. Hematoxylin penetrated into the meat slower than eosin; depth of hematoxylin penetration decreased with decreasing temperature, firmer meat texture and aging. Penetration rate was faster at the beginning than at the end of the test period. Penetration rate and depth of oxygen into beef, lamb, and pork were investigated also. The samples (8 cm³) were placed in a modified atmosphere package containing 80% oxygen and 20% carbon dioxide. The samples were cut at selected time intervals up to 26 h after addition of oxygen and oxygen penetration rate and depth were measured. Oxygen penetration was deeper in beef than in pork and deeper in pork than in lamb. Oxygen penetration rate was faster initially and then slowed as time progressed.     

Reduction of Escherichia Coli O157:H7 and Lactobacillus Plantarum Numbers on Fresh Beef by Polylactic Acid and Vacuum Packaging

ABSTRACT: The efficacy of 2% molecular weight 240, 2% molecular weight 360 polylactic acid (PLA), and an equal mix of both at reducing numbers of Escherichia coli O157:H7 and Lactobacillus plantarum on raw beef was determined. Fresh beef cubes inoculated with either organism were dipped in PLA solutions or wrapped in PLA-sprayed films. Samples were vacuum packaged and stored at 4°C for 42 d. Treated samples maintained a significantly lower pH than controls. Growth of E. coli O157:H7 was totally inhibited by both PLA treatments by up to 7.29 log₁₀ CFU/cm² when the spray method was used. However, PLA treatments against L. plantarum were not very effective.     

Microbiological condition of beef mechanically tenderized at a packing plant

When striploins were mechanically tenderized at a beef packing plant, the log total numbers of aerobes, coliforms, staphylococci/listerias and Escherichia coli recovered from surfaces before or after tenderizing were about 2.8, 2.0, 0.6 and 0.3 log cfu 25 cm⁻², respectively. The numbers of those organisms recovered from the deep tissues of the tenderized meat were about 2.0, 1.5 and 1.2 log cfu 25 g⁻¹ and none, respectively. The aerobes recovered from the deep tissues were unexpectedly numerous in view of the small numbers of bacteria on meat surfaces. That suggests deep tissue contamination was affected by factors other than the numbers on meat surfaces. After cooking tenderized beef to medium rare or well done conditions, with maximum temperatures at steak centres of 65.4 or 73.4 °C, respectively, aerobes were recovered from only 2 of 25 samples cooked to each condition, at numbers of one or two per sample. This indicates that such cooking can ensure the microbiological safety of mechanically tenderized beef prepared under controlled conditions.     

Quantitative changes in bacteria, amino acids and biogenic amines in sardine (Sardina pilchardus) stored at ambient temperature (25–28°C) and in ice

Freshly caught sardines contained high levels of bacteria located mainly on the skin and the gills. These bacteria invaded and grew rapidly in sardine muscle, reaching 5x10⁸ c.f.u. g^-1 and 6x10⁸ c.f.u. g^-1 respectively after 24h at ambient temperature and 8 days in ice.
Histidine, arginine, lysine, tyrosine and methionine levels decreased during storage. The other amino acids, except proline and taurine, accumulated in the fish muscle, indicating an extensive proteolysis.
Histamine, cadaverine and putrescine accumulated to levels of 2350ppm, 1050ppm and 300ppm respectively, after 24h storage at ambient temperature. Histamine and cadaverine reached similar levels after 8 days storage in ice, whereas putrescine formation was insignificant. Spermidine and spermine levels increased slightly under ambient conditions.
Salting the fish at 8% delayed bacterial and chemical changes but only in iced sardines.
The high content of free histidine found in sardines and the susceptibility of its muscle to histamine and cadaverine formation could explain its increasing implication in incidents of histamine poisoning.     

SURVIVAL OF THREE SALMONELLA SEROTYPES ON BEEF TRIMMINGS DURING SIMULATED COMMERCIAL FREEZING AND FROZEN STORAGE

This study investigated the survival of three Salmonella serotypes (S. Brandenberg, S. Dublin and S. Typhimurium) on beef trimmings during simulated commercial freezing, frozen storage for 9 months and subsequent abusive slow thawing and refreezing conditions. This was achieved by plating samples monthly and after thawing and refreezing on nonselective Tryptic Soy Agar (TSA) and selective Xylose Lysine Desoxycholate Agar (XLD) and incubating both at 37C for 24 h to determine Salmonella counts, aerobic counts and the presence, if any, of sublethal injury of this pathogen. Two freezing temperatures (−18C or −35C) to simulate slow or rapid freezing respectively, and two inoculation levels (10³ cfu g⁻¹ or 10⁵ cfu g⁻¹) were used. Aerobic counts and counts of all the Salmonella serotypes did not change significantly (p > 0.05) during frozen storage or for any of the other treatments applied in this study. This finding was attributed to the insulating nature of the subcutaneous fat layer in this manufacturing cut. These results are important with respect to food safety associated with ground beef processing.