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The effect of addition of glucose, lactic acid (LA) as well as radurization on several bacterial groups in refrigerated beef was investigated. Glucose added to meat in concentrations of 2 to 10% (w/w) had little influence on the bacteria monitored. Addition of LA to a pH of 5 had a marked effect on several bacteria groups in meat; the effect became more pronounced during storage. An increased shelf life was obtained but the appearance of LA-treated samples was undesirable. Radurization (2.5 kGy) had a far greater effect on shelf life than any of the other treatments, although an overwhelming population of lactic acid bacteria developed toward the end of the storage period. Radurization also caused a significant increase in the shelf life in comparison to control, glucose-treated and LA-treated meat samples. A combiend treatment of radurization and LA had an even greater effect on the bacterial population and the shelf life of meat than that of the two separate treatments.

1. Effects of the amount of food consumed on reproduction of the carabid beetle,Carabus yaconinus B., were studied in the laboratory by rearing beetles at different food levels, and the feeding and oviposition rates in the field were estimated on the basis of the relationships between the amount of food consumed, body weight and egg production obtained in the experiment. 2. The maximum amount of food consumed was 150 mg of minced beef per day. The number of eggs laid per day and the mean body weight increased with an increase in the amount of food consumed. High mortality occurred only when the beetles consumed less than 25 mg of minced beef per day. 3. The ratio of current body weight to the minimum one just before death by starvation,W/Wmin, was used for the estimation of the rates of food consumption and egg production. The relationships between meanW/Wmin ratio, the amount of food consumed and the number of eggs laid per day were clarified. 4. The relationships between ovary states (ovary weight and the number of mature eggs in the ovary) andW/Wmin ratio were examined for the females caught in the field. Females with higher values ofW/Wmin ratio had more mature eggs. 5. The amount of food consumed by females in the field during the reproductive period was estimated to be 50–70% of the maximum value attained in the experiment and the estimated rate of oviposition was 45–59% of the maximum rate attained in the experiment.

Yeast flora present in minced beef before and after radurisation were examined. No reduction in the number of yeast cells was observed after the meat was radurised at a dose of 2.5 kGy. A definite increase in the number of psychrotrophic yeast was observed in radurised meat after 14 days of storage at 4°C. The recovered yeast flora comprised representatives of the following species: Candida famata (9 isolates); C. lipolytica (4 isolates); C. parapsilosis (20 isolates); C. sake (27 isolates); C. zeylanoides (28 isolates); Cryptococcus albidus var. albidus (6 isolates); Cr. infirmo-miniatus (1 isolate); Cr. laurentii var. laurentii (31 isolates); Trichosporon cutaneum (1 isolate); Tr. pullulans (2 isolates); Rhodotorula minuta var. texensis (1 isolate); Rh. rubra (1 isolate).

One hundred and seventy-two samples of pig faces, collected at a slaughterhouse, were investigated for Listeria species. Three of the samples (1.7%) contained L. monocytogenes , while L. innocua was demonstrated in four other samples. The 172 samples represented pigs from 72 herds, 14 (19%) of which were SPF herds. Listeria was not demonstrated in any of the samples from the SPF herds representing 24% of all samples investigated. This indicates that the incidence of L. monocytogenes in SPF herds might be very low. In 51 samples of minced pork, Listeria spp. were demonstrated in 32 samples, L. monocytogenes in six samples, L. innocua in 26 samples, and L. seeligeri in one sample. In comparison with similar findings in cattle faeces and minced beef, the conclusion was drawn that faecal contamination may play an important role in the dissemination of L. monocytogenes in raw meats.

The effect of various stages of the irradiation processing of beef on the injury and inactivation of radiation-resistant Moraxella-Acinetobactor cells was studied. Moraxella-Acinetobacter cells were more resistant to heat inactivation and injury when heated in meat with salts (0.75% NaCl and 0.375% sodium tripolyphosphate) then in meat without salts. These salts had no effect on radiation resistance. Both radiation- and heat-injured cells were unable to form colonies at 30 degrees C in plate count agar containing 0.8% NaCl. Neither unstressed nor heat-stressed cells were able to multiply in minced beef incubated at 30 degrees C for 12 h. Only after the beef was diluted 1:10 with peptone water were the heat-injured cells able to repair and eventually multiply. Heated cells were more sensitive to radiation inactivation and injury than unheated cells. After repair, the cells regained their resistance to both NaCl and irradiation. Freezing and storage at -40 degrees C for 14 days had only a slight effect on either unstressed or heat-stressed cells.

SummaryThirty-one laboratories examined a total of 6169 meat samples, 1236 from abattoirs and 4933 from retail and other outlets.Campylobacter jejuniwas isolated from 98 (1·6%). A higher isolation rate of 49/1236 (4·0%) was found among abattoir than among retail and other samples (49/4933–1·0%). Twenty-two of the laboratories looked for salmonella; although 94/4002 (2·3%) were positive, in only one sample of minced beef were campylobacter and salmonella found together. Isolation rates for salmonellae were 75/3576 (2·1%) from retail and 19/426 (4·5%) from abattoir samples.Analysis of the results revealed that (1) the contamination rate of raw red meat byC. jejuniis, in general, very low; (2) when contaminated, numbers of organisms are generally also very low; (3) enrichment procedures were of some value; 41/98 (42%) isolates were detected by enrichment only, but, on the other hand 8 (8%) were direct plate positive/enrichment negative; (4) practice at looking for the organism and increased seasonal temperatures over the survey period did not result in a noticeable increase in isolations; (5) there was no apparent correlation between campylobacter and salmonella isolations.

Results obtained with tetrathionate broth (TBB) using the standard method and Rappaport-Vassiliadis medium (RV) did not differ markedly with respect to the proportion of positive samples or the sero- and phage types of salmonellae isolated from minced beef and pork. TBB, based on the commercial dehydrated medium of Oxoid (CM 343), gave fewer positive samples while that of Merck (Art. No. 5172) was equivalent to RV. In individual experiments results were sometimes markedly different. Results obtained for reference samples of minced meat, with salmonellae added, demonstrated that the chances of detecting salmonellae increase with increasing numbers present initially. At the same time it was also demonstrated that the presence of minced meat and its competing microflora have an unpredictable effect on the detection of salmonellae.

Small scale consumer trials using the weight-of-rejection technique did not provide a satisfactory pattern for the assessment of acceptability of dehydrated beef vacuum-dried in edible fat, because of the high level of meat consumption. The acceptability has therefore been assessed from large-scale consumer trials in Service establishments by means of questionnaires. When vacuum-dried minced beef was reconstituted and prepared under supervision, it was as acceptable as the fresh equivalent. When vacuum-dried beef steak was similarly treated, it was less acceptable than fresh steak, chiefly because of its slightly fibrous texture, but was about as acceptable as either fresh or dehydrated mince similarly flavoured and seasoned.

Food materials dried by the accelerated freeze drying (A.F.D.) process have been tested for free radicals and the concentration and properties of the free radicals compared with those in fresh heart muscle. In fresh muscle at 77° K, the free-radical concentration was between 2.0 and 5.2 × 1015 per g. of tissue; A.F.D. minced beef 8.28 × 1015; A.F.D. herring 6.47 × 1014; A.F.D. maize 1.78 × 1014; A.F.D. rat cake 1.30 × 1014. No free radicals were detected in either the minced beef or maize before A.F.D. processing; nor could free radicals be detected in a quick-frozen (−15° c) sample of minced beef stored some weeks. There is a higher concentration of free radicals when the lipid content of the food is high. The free-radical concentration increased in A.F.D. food in the presence of air and oxygen and also when it was heated to 100° c. The addition of water to A.F.D. food reduced the free-radical concentration to undetectable levels.

A method is described for preparing a 19 S thyroglobulin component from a saline beef thyroid extract by chromatographic fractionation on Sephadex G-200. By employing Sephadex G-200 it was possible to separate a saline extract of minced beef thyroid gland into several fractions, the first of which (fraction I) contained approximately 60% of the protein and 96% of the iodine. Spectrophotometric, ultracentrifugal, and immunochemical methods revealed that fraction I possessed, in addition to the 19 S thyroglobulin protein, a 25 S component as well as serum proteins. A narrow band of fraction I appeared to be free of both the 25 S component and the serum proteins. The material in this subfraction had a sedimentation constant of S20,w = 19.1 and contained 1.2 mg of iodine per 100 mg of protein.

Partial gastrectomy and intestinal resection significantly impaired glucose tolerance (p < 0·05) and significantly decreased the release of insulin by intravenous glucose (p < 0·05) or a meal of minced beef (p < 0·01). There was a significantly greater release of insulin one hour after oral glucose in the gastrectomy patients (p < 0·05).

Fresh meats (minced beef and sausage) and cooked meats (boiled ham and roast pork) from twenty-five butcher's shops in Essex were examined for contamination by antibioticresistant faecal coliform bacteria. Of twenty-five samples of each meat examined, eleven sausage, three mince, no boiled-ham, and two roast-pork samples were contaminated with faecal Escherichia coli. All samples, fresh and cooked, were heavily contaminated with other types of bacteria: up to 10 6 bacteria per g. of boiled ham and 10 5 bacteria per g. of roast pork. About 40% of fresh-meat and 4-12% of cooked-meat samples carried drug-resistant coliform organisms. Of a hundred samples only two yielded E. coli with transferable drug resistance. There was very little evidence of contamination of meats and meat products by drug-resistant faecal E. coli, but the results demonstrated that all the foods examined were heavily contaminated by bacteria, probably from human handlers.

The survival of S. typhimurium U285 was studied in cooked minced beef, sausage mixture and tryptone soya yeast extract (TSY) broth stored at freezer temperatures (-18 degrees C to -20 degrees C) for up to 10 weeks. Survival, as indicated by changes in viable counts, was best in minced beef followed by sausage mixture and TSY broth. Metabolic injury was minimal in each substrate whereas structural injury was detected, especially in TSY broth. Recovery, as indicated by changes in viable counts during thawing at room temperature, was generally complete after thawing 10 g or 10 ml amounts for 2 h. Viable counts obtained after thawing at refrigerator temperature for 24 h were similar to those obtained after 2h at room temperature. For specimens containing low inocula of salmonellae (0.5 cells/g), more isolations were obtained with pre-enrichment than with direct enrichment for minced beef and sausage mixture.

From the work reported it can be seen that the in vivo neutron activation analysis method can be used to measure nitrogen in vivo in small animals (mass about 5 kg) with a reproducibility of +or-7% (1 SD). Measurements of nitrogen in minced beef were consistent with the chemical analysis method. For live animals the statistical error was low enough to determine the quantity of nitrogen to better than 10%. To improve this method one should use more detectors to increase the statistical accuracy without increasing the dose or time.

A tube rheometer was used for determining rheological properties of coarsely minced beef and pork. Slip at the tube wall, indicated through the dependence of the consistency coefficient of the power-law model upon the tube diameter, was determined. In the measured range of shear rates, the flow behaviour index was found to be independent of the tube diameter. The consistency coefficient, being a function of the dimensionless tube diameter was expressed by means of an empirical equation, applicable in designing systems for meat transportation in pipes.

SUMMARYMinced (ground) beef from three supermarkets, three intermediate-sized chain butchers and three small family butchers in each of three geographical areas was examined three times in warm weather and three times in cool. The total viable count (37 and 20°C), numbers of Enterobacteriaceae (37 and 17°C), and presumptive coliforms did not differ significantly between shop type or season. Statistically significant differences in numbers of faecal Streptococci,Staphylococcus aureusandClostridium perfringenswere too small to be of commercial importance, or diagnostic value.

Thirty-nine samples of feeds and 79 faecal samples were collected at seven different dairy farms, at some of which the cows were suffering from Listeria mastitis. Faecal samples were also collected from poultry on a dairy farm and from cages used for transportation of poultry to slaughter. Also neck-skin samples were taken from 17 carcasses of dressed poultry, and five samples of scalding and chilling water at a poultry slaughterhouse. Finally, 67 samples of minced beef were collected from retail shops. The overall results show that approximately 82% of the feed samples harboured Listeria spp. and 62% Listeria monocytogenes. The faecal samples showed that 67% harboured Listeria spp. and 51% L. monocytogenes. In the minced beef samples, Listeria spp. could be demonstrated in 67% and L. monocytogenes in 28%. Of the faecal samples from poultry, 33% harboured Listeria spp. and also 33% L. monocytogenes. Listeria spp. were detected in 94% of the poultry neck-skin samples, and L. monocytogenes in 47%. Almost all L. monocytogenes from faeces and feeds agglutinated Listeria antisera against serotypes 1-4, while only 71% of the strains from minced beef agglutinated the same antisera. The high prevalence of positive findings indicates that the isolation method used is suitable for detection of Listeria spp. in heavily contaminated material as well as in foods with low bacterial counts.

Reference samples consisting of spray-dried milk artificially contaminated with Salmonella typhimurium II 505 contained in a gelatin capsule have been developed to evaluate the standard method for the detection of Salmonellae in foods and feeding stuffs. The present study was carried out to evaluate these reference samples. Salmonella isolations from reference samples in the absence of food were satisfactory in 4 out of 6 laboratories when Muller-Kauffmann tetrathionate broth prepared according to ISO-6579 (TBB-ISO) was used and in all laboratories when the secondary enrichment medium was the magnesium chloride-malachite green broth of Rappaport-Vassiliadis (RV). The proportion of Salmonella isolations from reference samples decreased from 80% to 47% with TBB-ISO and from 95% to 63% with RV in the presence of food. Most negative results were obtained with foods such as minced pork and minced beef, which had high aerobic and Enterobacteriaceae plate counts. It is concluded that the reference samples can be used to test the performance of media and the reproducibility of methods when it is used without the addition of food. The results obtained for Salmonella isolations in the presence of food questioned the role of numbers and types of competitive micro-organisms. In particular these latter results indicated that more research is needed to gain a better understanding of the Salmonella isolation procedure.

A gas chromatographic/mass spectormetric assay has been developed for the simultaneous measurement of 2-amino-3,8-dimethylimidazo[4,5-ƒ]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-ƒ]quinoxaline (DiMeIQx) in fried beef. The method employs capillary column gas chromatography, electron capture negative ion chemical ionization mass spectrometry and a stable isotope labelled analogue of MeIQx as common internal standard. Two patties of lean minced beef which had been cooked separately were analysed and found to contain both compounds (patty 1:2.4 ng MeIQx g−1 meat, 1.2 ng DiMeIQx g−1 meat; patty 2: 1.3 ng MeIQx g−1 meat, 0.5 ng DiMeIQx g−1 meat). Neither compound was present in the meat prior to cooking.

A double-antibody sandwich ELISA (enzyme-linked immunosorbent assay) has been successfully developed for the detection of defined amounts of horse meat (1-50%) in unheated meat mixtures. The assay uses horse-specific antibodies obtained by immunoadsorption of the crude horse antisera onto immobilised sarcoplasmic extracts from chicken, beef and pig to remove cross-reacting antibodies. The purified antibodies bound to a solid support sequester horse muscle soluble proteins from meat mixtures. Further immunorecognition was made with the same antibodies conjugated to the enzyme horseradish peroxidase. Subsequent enzymic conversion of substrate gave clear optical density differences when assaying mixtures of minced beef and pig containing variable amounts of horse meat.

Growth rates and lag times of Salmonella organisms were determined in minced beef at temperatures between 10 and 35°C. A mixture of serotypes containing antibiotic-resistance markers was used to allow small numbers of salmonellae to be counted in the presence of an excess of competing organisms. Maximum growth rates and lag times of salmonellae were unaffected by inoculum size. The effect of temperature on growth rate could be described by the simple square root relationship of Ratkowsky et al. (J. Bacteriol. 149, 1–5, 1982).

Yield stress values and flow curves as functions of temperature, time of standing, fat content, brine addition and aggregates size have been investigated for coarsely minced beef using modified coaxial rotational rheometry. Results for the yield stress dependences are in good qualitative accordance with those for comminuted meat homogenates.

A gas chromatographic-mass spectrometric assay has been developed for the simultaneous measurement of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) in fried beef. The method employs capillary column gas chromatography, electron capture negative ion chemical ionisation mass spectrometry and a stable isotope labelled analogue of MeIQx (the synthesis of which is described) as common internal standard. Two patties of lean minced beef which had been cooked separately were analysed and found to contain both compounds (patty 1-2.4 ng MeIQx/g meat, 1.2 ng DiMeIQx/g meat; patty 2-1.3 ng MeIQx/g meat, 0.5 ng DiMeIQx/g meat). Neither compound was present in the meat prior to cooking.

The susceptibilities to six antibiotics have been determined of Clostridium perfringens serotypes isolated from beef, pork and lamb carcases and from minced beef. Generally similar results were obtained to those of previous studies of mainly clinical isolates. Fourteen of the 229 strains tested were resistant to tetracycline; three of these, from the same beef carcase, were also resistant to erythromycin.

Samples of minced (ground) beef were purchased on three occasions from seven supermarkets and eleven butcher's shops in one geographical area during winter. Total viable counts (at 37°C and 20°C), numbers of Enterobacteriaceae (at 37°C) and Escherichia coli biotype I were similar between shop type. No Salmonella spp. were detected. In general, bacterial counts were lower than in a similar survey four years previously. The fat and collagen content of the samples was also determined. In a previous survey, 37% of samples contained more than 25% fat, while, in this survey, only 17% of the samples exceeded that level. Collagen levels in the mince at retail ranged from 1·4% to 4·4% (1·5% to 5·1% on a wet fat-free basis).

Three hundred and eighty three yeasts isolated from samples of unsulphited or sulphited sausages and skinless sausages and minced beef were characterized in detail. Debaryomyces hansenii was the most commonly isolated yeast from most samples followed by Candida zeylanoides and Pichia membranaefaciens. The presence of sulphite in sausages did not appear to affect the numbers and range of yeasts present but did affect their relative proportions. A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.

In order to gain the most information from the Wassermann test, more than one antigen should be used in the "set up." One of the antigens so used should undoubtedly be the Noguchi acetone-insoluble, as it will give positive reactions with a higher percentage of syphilitic serums than the alcoholic extracts, while it is less likely to give false positive reactions than the more sensitive cholesterinized extracts. But its preparation requires so much time that this becomes quite a factor in a laboratory where considerable quantities are used. With a view of hastening the process of extraction and evaporation we tried this at higher temperatures and find that boiling temperature in no way interferes. In this way we can prepare and titrate an antigen all in one day. PROCEDURE To one part of finely minced beef heart, nine parts of commercial ethyl alcohol are added. (We have recently tried the

SummaryThe succinic dehydrogenase activity of beef muscle determined after different methods of homogenization of the tissue was investigated. The amount of beef muscle needed for a representative sample was too large to be conveniently used with the Potter-Elvehjem homogenizer; however, the samples could be prepared for assay by homogenizing in a Waring blendor, provided that the homogenization time is held to a minimum. This was evidenced from studies which showed that homogenizing the minced beef tissues in a Waring blendor for 1 minute or homogenizing Latapie minces for 1/2 minute resulted in a greater succinic dehydrogenase activity than that obtained when the tissues were homogenized for longer periods. Other experiments with rat tissues showed that the enzyme activity of rat muscle homogenized in the Waring blendor for 1 minute, in a Potter-Elvehjem homogenizer, or ground with sand was essentially the same.

A specific PCR assay was used to detect Salmonella in enriched broths of 48 natural samples of minced pork and 48 natural samples of minced beef. By comparison with a routine culture method, the sensitivity of the PCR method was estimated to be 92% and the specificity of the PCR method was estimated to be 99%. The sensitivity of the culture method was estimated to be 50% in this study.

The synthesis of investigations of three salmonellosis outbreaks which occured in France between 1998 and 2000 confirms the role of the consumption of minced beef and highlights the importance of prevention measures.