Lactic Acid Concentration and Microbial Spoilage in Anaerobically and Aerobically Stored Ground Beef

Lactic acid concentration of coarsely ground beef, packaged in low oxygen permeability casings, is inversely related to sensory acceptability of the meat following regrinding and aerobic storage for six additional days. Samples, reground and stored aerobically after periods of anaerobic storage, were assayed for total aerobic bacterial counts, percentage of gram-positive microflora, and pH. Lactic acid concentration ranged from 130 to 1055 mg per 100g ground beef and increased with anaerobic storage. During 6 days of aerobic storage, both increases and decreases in concentration were noted and related to changes in microbial flora. A positive correlation was found between the proportion of gram-positive bacteria (lactic acid bacteria) and lactic acid and pH.     

Protein Quality of Selected Muscle Foods as Affected by the Exchange of Dietary Wheat Bran for Cellulose

The exchange of 8.4% neutral detergent fiber (NDF) of wheat bran for 8.3% NDF of cellulose in diets containing either beef, chicken, fish or casein as protein sources did not (P>0.05) alter feed consumption, weight gain or energy intake in the protein efficiency ratio (PER) bioassay with weanling rats. Higher (P<0.05) fecal nitrogen (N) excretions and lower (P<0.05) N digestibilities occurred for each protein source when wheat bran was exchanged for cellulose. The exchange also had no effect (P>0.05) on PER or net protein ratio (NPR) of casein or fish protein or on NPR of chicken protein. However, PER and NPR of beef and PER for chicken were reduced (P<0.05) when the dietary fiber was exchanged.     

Variations in Radiation Sensitivity of Foodborne Pathogens Associated with the Suspending Meat

Longissimus dorsi from beef, pork, and lamb and turkey breast and leg meats were inoculated with Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus, and the gamma radiation resistance of the pathogens were determined under identical conditions. At 5°C the respective radiation D-values of E. coli O157:H7 and L. monocytogenes did not vary with the suspending meat. The D-value for a mixture of Salmonella spp. was significantly lower on pork than on beef, lamb, turkey breast, and turkey leg meats. The D-value for S. aureus was significantly lower on lamb and mechanically deboned chicken meat than on the other meats. All values were, nevertheless, within expected ranges.     

Bioavailability of Calcium from Sesame Seeds, Almond Powder, Whole Wheat Bread, Spinach and Nonfat Dry Milk in Rats

Calcium bioavailability (BV) from sesame seeds, almond powder, whole wheat bread, spinach, and nonfat dry milk (NFDM) was compared to calcium BV from a calcium carbonate (CaCO₃)-supplemented control diet using a rat model. When comparing different calcium sources, the relative BV of the products was CaCO₃ (100%), NFDM (100%) whole wheat bread (95%), almond powder (66%), sesame seeds (65%), NFDM and spinach mixture (52%), and spinach (47%). Separate almond, NFDM, and CaCO₃ diets were supplemented with 0.4% ascorbic acid; vitamin C addition had no significant effect on calcium BV.     

Fractionation of green tea extracts: correlation of antimutagenic effect with flavanol content

The present study was undertaken to evaluate the role of individual flavanols in the antimutagenic potential of green tea. Aqueous extracts of green tea were fractionated into four fractions, each of which was fully defined with respect to its content of (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epicatechin and gallic acid. The ability of each fraction to antagonize the mutagenicity of four model mutagens, namely N-nitrosopyrrolidine, benzo(a)pyrene, 2-aminoanthracene and Glu-P-1 (2-amino-6-methyldipyrido[1,2-a: 3,2-d]imidazole), was investigated in the Ames test. No correlation could be established between any of the flavanols and antimutagenic potential. Similarly, no correlation was evident between the flavanol content of each fraction and its ability to inhibit CYP1A, as exemplified by the O-dealkylations of methoxy- and ethoxy-resorufin. Furthermore, no relationship could be established between CYP2B activity, as exemplified by the O-depentylation of pentoxyresorufin and the antimutagenic potential of green tea. Using a modified Ames test procedure, the ability of each tea fraction to scavenge the metabolically generated reactive intermediates of the model mutagens was investigated, this being an additional mechanism of the antimutagenic potential of green tea. Generally, fractions with high flavanol content were more effective scavengers. It is concluded that the contribution of flavanols to the antimutagenic activity of green tea is, at best, limited. ©1997 SCI     

Influence of Poultry Species, Muscle Groups, and NaCl Level on Strength, Deformability, and Water Retention in Heat-Set Muscle Gels

The effects of poultry species (chicken and turkey), muscle groups (breast, thigh, and drum) and NaCl concentration (1% and 2%) on a low fat gel system were compared using measurements of shear stress (strength), shear strain (deformability), and two water retention measurements. Results showed doubling NaCl tended to double stress for all species and muscle groups and increased strain by 30–50%. Cross species differences showed higher stress in turkey gels than in chicken gels with 2% NaCl. For both species, stress, strain and water retention were lowest in breast gels with both NaCl concentrations, and strain was greater in thigh gels than in drum gels with 2% NaCl.     

Steam Surface Pasteurization of Beef Frankfurters

Meat and poultry products are sources of foodborne bacterial contamination. We used flash steam heating followed by evaporative cooling to quickly reduce bacterial contamination on the surface of beef frankfurters without degrading appearance. The rate of heat transfer was studied by measuring surface temperature in a pressure chamber during steam heating. Quality changes were determined by measuring color and weight as functions of steam temperature and treatment time. Efficacy of the process was verified by microbiological experiments using L. innocua. Treatment times of 30–40 set at 115–136°C gave a 4 log reduction in bacterial counts on the surface without severely affecting color or weight. After long-term storage at 6°C and at 19°C, levels of bacteria on inoculated frankfurters remained reduced and there was no difference between treated and untreated products in color or weight.     

Differential Thermal Analysis Investigation of the High-Low Cristobalite Inversion Under Hydrostatic Pressure to 7 Kbar

The high-low inversion in polycrystalline cristobalite, synthesized from quartz at 1500°C, was investigated by differential thermal analysis to 7 kbar in hydrostatic apparatus. A region of anomalous curvature ( d²T/dp² >0) exists to ∼1 kbar; at higher pressure, the low→high and high→low transition temperatures vary linearly with pressure, with slopes of ∼51.₁ and 53. ₆ deg kbar⁻¹, respectively. Extrapolated 1-bar intercepts are ∼232° and ∼209°C, respectively. It is concluded that high cristobalite is less compressible than low cristobalite near the inversion. The hysteresis between the high→low and low→high transition temperatures decreases with increasing pressure.     

Deformation and Fracture Processes in Calcium Fluoride Single Crystals

The plastic properties of calcium fluoride single crystals tested in compression were investigated in the temperature range 25° to 1000°C. Above 400° C., the crystals showed appreciable ductility. The critical resolved shear stress, t, decreased with absolute temperature, T , according to the equation t = t₀e^+K/T. The rate of work-hardening decreased rapidly as the temperature increased but retained a relatively high value even as the melting point was approached. Air-annealed crystals were harder than as-cleaved crystals. Crystals with a (111) plane normal to the applied stress hardened less rapidly than crystals with a (110) plane normal to the applied stress. The dislocation density increased linearly with strain. (100), (110), and (111) fractures were observed.     

Phase Equilibria in the System CaF2-AlF3-Na3AlF6 and Part of the System CaF2-AlF3-Na3AlF6-Al2O3

The complete phase-equilibrium diagram of the system CaF₂-AlF₃-Na₃AlF₆ and the subsolidus portion of the system CaF₂-AlF₃-Na₃AlF₆-Al₂O₃ were established from microscopic, powder X-ray diffraction, quench, and DTA data obtained from samples encapsulated in sealed tubes and either reacted in the solid state or melted and recrystallized. The system Na₃AlF₆-CaF₂ contains a simple eutectic with no compound formation or solid solution. The system CaF₂-AlF₃-Na₃AlF₆ contains two ternary compounds, NaCaAlF₆ and NaCaAl₂F₉, which melt incongruently at 735° and 712°C, respectively; NaCaAlF₆ exists in three polymorphic forms with transitions at 610° and 722°C and NaCaAl₂F₉ is body-centered cubic with a₀= 10.765 Å. The three binary and two ternary compounds divide the system into eight compatibility triangles. Along the NaCaAlF₆-Na₃AlF₆ join, 7 mol% NaCaAlF₆ is soluble in α-cryolite at 525° and 42% in β-cryolite at 731°C. The quaternary system Na₃AlF₆-AlF₃-CaF₂-Al₂O₃ contains eight compatibility tetrahedra.