Microbiology of Beef, Pork and Lamb Stored in Vacuum or Modified Gas Atmospheres

Beef, pork and lamb loins were vacuum-packaged as subprimal cuts (controls), reformed subprimal cuts and as retail cuts (steaks or chops). Subprimal cuts, reformed subprimal cuts and one group of retail cuts remained vacuum-packaged. Other groups of retail cuts were injected with atmospheres of either 20% CO₂ + 80% N₂ or 40% CO₂ + 60% N₂. Cuts were randomly assigned to storage periods of 0-21 days at 2 ± 1 C. At weekly intervals, steaks or chops were removed from each treatment and examined after storage for 5 days under retail display conditions. Psychrotrophic bacterial counts and lactobacilli counts of steaks and chops stored in CO₂-N₂ atmospheres usually were lower, though not often statistically significant, than those of comparable vacuum-packaged steaks, chops or loins. Psychrotrophic counts of steaks and pork chops, initially held in CO₂,-N₂ atmospheres and then subjected to retail display, usually were lower than those of comparable steaks and chops that had been vacuum-packaged (without added CO₂-N₂) or prepared from vacuum-packaged loins.

Effect of CO2-N2 Atmospheres on the Microbial Flora of Pork

Pork loins were vacuum-packaged; one group remained vacuum-packaged, other vacuum packages were injected with gas atmospheres of either 20% CO₂ + 80% N₂ or 40% CO₂ + 60% N₂. Loins were stored for 7, 14, 21 and 28 days at 1-3 C. After each storage interval, chops were prepared from loins and subjected to 5 days of retail display. Psychrotrophic bacterial counts of lean and fat surfaces of loins stored in 40% CO₂ + 60% N₂ were frequently significantly lower than counts of comparable sites of vacuum-packaged loins. Lactobacillus counts of the subcutaneous fat cover of loins stored in CO₂ + N₂ were in most instances (7 of 8 comparisons) significantly higher than those of vacuum-packaged loins; this was true in only 2 of 8 comparisons for the lean surface. Psychrotrophic bacterial counts of chops prepared from loins subjected to the various storage treatments were seldom significantly different. During storage of pork loins, lactobacilli became a predominant part of the microflora and comprised more than 90% of the microflora after 21 days for loins stored in CO₂ + N₂ and after 28 days for vacuum-packaged loins. Pseudomonas spp. continued to persist to a greater degree in the vacuum-packaged loins than in the loins stored in CO₂ + N₂.

Isolation of Yersinia enterocolitica from Pig Tonsils

Yersinia enterocolitica serotype 0:5 was isolated from the tonsils of 8 of 27 butcher hogs subjected to normal slaughtering procedures. Isolation through enrichment in cold mannitol broth or a bile medium at 4 C for 10-60 days was equally effective. Enrichment in modified Rappaport broth at 25 C for longer than 2 days sharply decreased recovery of Y. enterocolitica from tonsils. The type of enrichment medium also had a marked effect on the recovery efficiency of different strains of Y. enterocolitica from ground meat.

Brain amines and peptides--their relevance to psychiatry

The amine theory of affective disorder and the dopamine and endorphin theories of schizophrenia are controversial but heuristically valuable concepts that have emerged from the psychobiological revolution of the last decade. That revolution stemmed largely from the development of techniques for localizing and assaying neuroregulators and their receptors in the brain under normal, pathological and experimental conditions. The data thus obtained are reviewed here, and the current status of the emergent psychobiological hypotheses assessed.

Squirrel monkey retrovirus and Herpesvirus saimiri: observation in the same cell following isolation

Electron microscopic examination of mink lung cells previously cultured with a squirrel monkey (Saimiri sciureus) throat swab suspension revealed the presence of squirrel monkey retrovirus (SMRV) and Herpesvirus saimiri (HVS) coexisting within the same cells in culture. HVS was identified by serum neutralization, and the retrovirus isolate was identified as SMRV by a morphologic examination, microimmunodiffusion analysis, and demonstration of an Mg2+ preference for the RNA-directed DNA polymerase.

Electron microscopic examination of primate feces for rotaviruses

Using electron microscopic procedures known to be capable of detecting rotaviruses, feces from both human and nonhuman primates were examined for the presence of these viruses. Fecal samples were taken from man and animals with and without diarrhea. Rotaviruses were not observed in these specimens.

Physical, Chemical and Palatability Traits of Electrically Stimulated, Hot-boned, Vacuum-packaged Beef

The right sides of six beef carcasses were electrically stimulated, whereas the left sides were not so treated. Sections of longissimus and semimembranosus muscles were removed from electrically stimulated sides at 1 h postmortem (hot-boned) and from sides which were not electrically stimulated at 24 h postmortem (conventionally boned); these muscles were vacuum-packaged immediately after removal and aged for 2 weeks at 1 ± 1 C. After aging, steaks were removed and used for determinations of palatability, cooking loss, pH, sarcomere length and protein solubility. Further evaluation included purification and electrophoresis of myofibrillar proteins. Longissimus muscles from electrically stimulated, hot-boned beef had lower (P < .05) juiciness ratings than those from conventionally handled sides; semimembranosus muscles from electrically stimulated, hot-boned sides sustained lower (P < .05) weight losses during storage but higher (P < .05) cooking losses than muscles from conventionally handled sides. Hot-boning of electrically stimulated beef had no effect (P > .05) on tenderness, flavor desirability, pH, sarcomere length, amount of non-protein nitrogen or percentage of soluble myofibrillar proteins; slight alterations were noted in the electrophoretic banding patterns, on SDS gels, of myofibrillar proteins from electrically stimulated. hot-boned sides. Hot-boned beef was as palatable as conventionally handled beef if sides were electrically stimulated on the kill floor before hot-boning and if beef from both treatments was vacuum packaged and aged for 2 weeks at 1 ± 1 C.

Blade Tenderization Effects on Cooking and Palatability Characteristics of Steaks from Bullock and Cow Carcasses

Steaks (n = 240) from bullock and cow carcasses were studied to determine effects of blade tenderization on cooking and palatability characteristics. After two control (0×) steaks were removed, strip loins, inside rounds, outside rounds and top sirloin butts (all boneless) were blade-tenderized; additional steaks were removed after one (1×) and two (2×) passes through a blade tenderizer. Evaluations included cooking time, cooking loss, visual degree of doneness, Warner-Bratzler shear force and sensory panel evaluation for tenderness, amount of organoleptically detectable connective tissue, flavor, juiciness and overall palatability. Blade tenderization of bullock muscles resulted in steaks which required less time to cook, had decreased amounts of organoleptically detectable connective tissue and had increased tenderness, flavor and overall palatability ratings. Blade tenderization of cow muscles had little or no effect on cooking characteristics, tenderness, flavor, or overall palatability of muscles from the round but increased the tenderness, decreased the shear force value and amount of organoleptically detectable connective tissue, and increased the overall palatability of the longissimus dorsi muscle. Blade tenderization, though it will usually improve tenderness, will not improve the product enough to make beef of unsatisfactory quality comparable to that from high quality beef.

Role of Hafnia alvei and a Lactobacillus Species in the Spoilage of Vacuum-Packaged Strip Loin Steaks

A microbiological examination of vacuum-packaged strip loin steaks that were defective (gassy packages, hydrogen sulfide odor) revealed high total counts (10⁷-10⁸/cm²) with Hafnia alvei , Lactobacillus and Pseudomonas spp. as major isolates. Re-inoculation experiments indicated that H. alvei was the likely cause of the hydrogen sulfide odor. Gas formation resulted from the activity of heterofermentative lactobacilli and H. alvei . Improvements in plant practices and temperature control eliminated the problem.

Differentiation of the formaldehyde-induced fluorescent products of noradrenaline and dopamine by microspectrofluorometry

The influence of concentration of dopamine and noradrenaline on the spectral characteristics of their formaldehyde-induced fluorophore, together with the influence of duration of reaction with formaldehyde, has been investigated in a model system. No substantial differences between fluorescence spectra of the amine fluorophores were observed. Accordingly, the influence of hydrochloric acid and ammonia vapours on the fluorophores was investigated. A shift to shorter wavelengths in the excitation maximum of each fluorophore was observed after a brief exposure to hydrochloric acid vapour; more prolonged exposure resulted in a pronounced shift back to longer wavelengths in the case of noradrenaline but no substantial change was observed with dopamine. Brief exposure to hydrochloric acid vapour resulted in a substantial increase in the rate of fading of the noradrenaline fluorophore on exposure to exciting radiation. It is suggested that this offers a convenient way of differentiating the amines.

Attachment of Microorganisms to Pork Skin and Surfaces of Beef and Lamb Carcasses

A model system was developed to study attachment to and possibly detachment of bacteria from pork skin and thin-surface slices of beef and lamb carcasses. The technique involves embedding pork skin and beef and lamb surfaces in solidified wax with the skin surface exposed. After exposure of the skin or carcass surface to bacterial suspensions and subsequent manipulations, the sample is removed aseptically from the wax and subjected to agar plate counting methods. A direct relationship existed between bacterial counts of the skin or carcass surface and concentration of bacterial cells in the attachment medium. Much of the bacterial attachment occurred during the first minute of immersion in the attachment medium, although in some instances continued attachment occurred over a 30-min period. Gram-negative motile bacteria showed greater attachment than did gram-positive non-motile species. Temperature and pH of the attachment medium had little effect on the extent of bacterial attachment.

Cell-free varicella-zoster virus in cultured human melanoma cells

Varicella-zoster virus (VZV) has been isolated and serially propagated in a continuous cell line derived from a human malignant melanoma tumour. Human melanoma cells (HMC) have been further evaluated as a substrate for the production of cell-free virus and compare favourably with human embryo cells. Within 60 h after inoculation with VZV-infected cells, HMC monolayers incubated at 32 degrees C exhibited advanced syncytial cytopathic effect, and the overlying culture medium contained greater than 10(2) p.f.u./ml. The cell pellet from a mechanically dispersed 150 cm2 monolayer yielded 10(5) p.f.u. after sonic disruption, while the medium ('scraping medium') in which the cells had been harvested contained up to one log more infectious virus than was found in the cells from the same monolayer. When infected cells were subjected to Dounce homogenization, most of the infectivity was found in the nuclear fraction. The concentration and purification of cell-free virus were also investigated. Concentration was carried out by three methods: ultracentrifugation, dialysis against hydrophilic compounds and liquid polymer phase separation. The first two procedures caused considerable loss of biological activity, whereas precipitation with 8% polyethylene glycol resulted in a 50-fold increase in titre. Purification of cell-free virus with retention of infectivity was achieved by rate zonal centrifugation in linear potassium tartrate gradients. Infectious virus was also recovered after sedimentation in combination equilibrium-viscosity gradients of potassium tartrate and glycerol, but not after centrifugation to equilibrium in caesium chloride gradients.

Physical and Sensory Characteristics of Pork Packaged in Various Gas Atmospheres

One hundred and ninety-six boneless pork roasts were vacuum-packaged. Twenty-eight roasts remained vacuum-packaged to serve as controls. The remaining packages were divided into six groups of 28 packages each and injected with one of six gas mixtures: (a) 100% O₂, (b) 20% CO₂ + 80% N₂, (c) 50% CO₂ + 50% O₂, (d) 20% CO₂ + 80% O₂, (e) 25% CO₂ + 25% O₂ + 50% N₂ or (f) 51% CO₂ + 30% O₂ + 18% N₂ + 1% CO. Five packages from each packaging treatment were removed from storage after 7, 14, 21, 28 or 35 days. Data collection included gas composition of the intact packages and off-odor, surface discoloration, overall appearance, retail caselife and palatability of cuts. The most prevalent gas in vacuum packages was CO₂ with weight percentages of 62-88% during the 35-day storage period. Packages initially injected with an atmosphere containing 100% O₂ showed a gradual decrease in O₂ and an increase in CO₂ with increased storage. Roasts stored in O₂-containing atmospheres for 14 and/or 21 days had a higher incidence of off-odor and chops from such roasts had lower overall appearance ratings after 1 day of retail display and lower flavor and overall palatability ratings than comparable vacuum packaged meats. These differences were significant only for roasts stored in modified atmospheres containing high concentrations of O₂ and only after extended periods of storage. Data suggest that a modified gas atmosphere of 20% CO₂ + 80% N₂ is a suitable alternative to vacuum-packaging.

Microbiology of Pork Packaged in Various Gas Atmospheres

Boneless pork roasts were vacuum-packaged; one group remained in vacuum-packages (controls), other vacuum-packages were injected with one of six gas mixtures: (a) 100% O₂, (b) 20% CO₂ + 80% N₂, (c) 50% CO₂ + 50% O₂. (d) 20% CO₂ + 80% O₂, (e) 25% CO₂ + 25% O₂ + 50% N₂, or (f) 51% CO₂ + 30% O₂ + 18% N₂ + 1% CO. Roasts were stored from 0-35 days at 1-3 C and chops from each treatment were observed under retail conditions for 5 days. Differences, both in psychrotrophic and lactobacillus counts, between roasts stored in modified gas atmospheres and those stored in vacuum-packages were rarely statistically significant. Psychrotrophic counts of pork chops from roasts stored for 21-35 days in modified gas atmospheres were somewhat higher than those prepared from comparable vacuum-packaged roasts. However, few of these differences were statistically significant. The initial microbial flora of the roasts consisted of Pseudomonas and Lactobacillus spp. Pseudomonas spp. remained a significant part of the microflora of roasts stored in 100% O₂, whereas lactic acid bacteria ( Lactobacillus and Leuconostoc spp.) predominated on roasts after 1 week in all other atmospheres.

Microbiology of Beef Packaged in Various Gas Atmospheres

Boneless beef roasts ( longissimus muscles) were vacuum-packaged and then the bags were injected with one of six gas mixtures: 100% O₂, 20% CO₂ +80% N₂, 50% CO₂ + 50% O₂, 20% CO₂ +80% O₂, 25% CO₂ + 25% O₂ +50% N₂ or 51% CO₂ + 30% O₂ + 18% N₂ + 1% CO. One group of roasts, vacuum-packaged without added gas served as controls. Roasts were stored for 0-35 days at 1-3 C. At five weekly intervals, steaks were removed from roasts in each treatment and examined after storage for 5 days under retail display conditions. Psychrotrophic plate counts of roasts stored in modified gas atmospheres were usually higher than those stored in conventional vacuum packages. Differences in lactobacillus counts between roasts stored in modified gas atmospheres and those stored in vacuum packages rarely were statistically significant. Counts of retail steaks prepared from roasts stored in various gas atmospheres were usually slightly higher than those prepared from comparable vacuum packaged roasts. In most instances these differences were not statistically significant. Initially, the microbial flora of vacuum-packaged beef roasts consisted primarily of Moraxella-Acinetobacter and Pseudomonas spp. Lactobacilli predominated on roasts at later storage intervals even on roasts stored in atmospheres initially containing 100% O₂ or 20% CO₂ + 80% O₂. Pseudomonas spp. remained a substantial part of the microflora of roasts stored in high O₂ containing atmospheres.

Physical and Sensory Characteristics of Beef Packaged in Modified Gas Atmospheres

One hundred and ninety-six boneless beef roasts ( longissimus muscles) were vacuum packaged. Twenty-eight roasts remained vacuum packaged to serve as controls while the remaining packages were injected with one of six gas mixtures: (a) 100% O₂, (b) 20% CO₂ + 80% N₂, (c) 50% CO₂ + 50%O₂, (d) 20% CO₂ + 80% O₂, (e) 25% CO₂ + 25% O₂ +50% N₂ or(f) 51% CO₂ + 30% O₂ + 18% N₂ + 1% CO. Five cuts from each packaging treatment were stored in a 1-3-C cooler for 7, 14, 21, 28 or 35 days and subsequently evaluated for relative percentages of various gases in the intact packages, off-odor, surface discoloration. overall appearance, metmyoglobin percentages and palatability. Packages initially injected with modified gas atmospheres containing O₂ increased in relative percentages of CO₂ with advancing storage times. Roasts stored in modified atmospheres initially containing high levels of O₂ exhibited a greater incidence of off-odor, more surface discoloration, lower overall appearance ratings, shorter retail caselife and lower overall palatability ratings than vacuum-packaged roasts or roasts stored in an atmosphere initially containing 20% CO₂ + 80% N₂.

The isolation of herpesvirus from trigeminal ganglia of normal baboons (Papio cynocephalus)

A herpesvirus was isolated from the trigeminal ganglia of three of six normal baboons (Papio cynocephalus). This virus possessed the virologic characteristics of SA8, A herpesvirus known to be indigenous to the baboon.

Comparison of Mason-Pfizer monkey virus and squirrel monkey (Saimiri sciureus) retrovirus by immunoelectron microscopy

Comparison of Mason-Pfizer monkey virus and squirrel monkey retrovirus (both candidate type D oncornaviruses) by immunoelectron microscopy revealed that these two viruses do not share common surface antigens.

The photochemistry of 3β-Acetoxy-6-nitrocholest-5-ene and 6-Nitrocholest-5-ene. The mechanism of photodeconjugation of α,β-unsaturated nitro compounds

The photochemistry of 3β-acetoxy-6-nitrocholest-5-ene (1) and 6- nitrocholest-5-ene (11) has been investigated in a number of solvents. It is suggested that for both compounds the major primary photo-product is the corresponding aci-nitro tautomer, which then undergoes further reactions depending mainly on the conditions employed. The aci-nitro compounds are believed to be formed by a 1,5-hydrogen shift from C4 to oxygen, and their intermediacy is supported by the formation of a mixture of 6α-deutero-6β-nitrocholest-4-ene and 6β-deutero-6α- nitrocholest-4-ene on irradiation of 6-nitrocholest-5-ene in Me3COD.��� Several other reactions of 3β-acetoxy-6-nitrocholest-5-ene and 6- nitrocholest-5-ene are described.

The structures of the Isoxazoles and 5-Isoxazolinones formed on irradiation of 3β-Acetoxy-6-nitrocholest-5-ene and 6-Nitrocholest-5-ene

.The two heterocyclic compounds produced on irradiation of 3β-acetoxy-6- nitrocholest-5-ene (1) have been shown by chemical degradation to be 3β-acetoxycholest-4-eno[6,5,4-cd]isoxazole (3) and 3β-acetoxy-A- norcholestano[6,5-c]-2'-isoxazoin-5'-one (4), while those formed from 6-nitrocholest-5-ene (2) are the analogous compounds, cholest-4-eno[6,5,4-cd]isoxazole (5) and A-norcholestano[6,5-c]-2'-isoxazolin-5'- one (6).

Observation of togavirus-like particles in nonhuman primates

Particles resembling togaviruses were observed by electron microscopy in the urinary bladder lamina propria of one capuchin monkey and in placental syncytiotrophoblasts of one baboon. Type C viruses were observed in the baboon placenta, but not in the tissues of the capuchin monkey.

The base-catalysed equilibration of 6α-Nitrocholest-4-ene and 6β-Nitrocholest-4-ene

Treatment of 6β-nitrocholest-4-ene with a catalytic amount of sodium methoxide in methanol gave an equilibrium mixture which contained the starting material and the 6α-epimer in a 1 : 1 ratio. The unusual stability of the 6β-epimer is explained by electronic factors.