New and classical spoilage bacteria causing widespread blowing in Argentinean soft and semihard cheeses

A total of 16 soft and semihard Argentinean cheeses, and 95 pasteurized cheese–milk samples, were analysed for microorganisms responsible for blowing. Lactic acid bacteria (starter microflora) resulted in high numbers (> 10⁷ colony‐forming units (cfu)/g). Coliform and yeast counts were lower than 10⁴ cfu/g. Cremoso cheeses were blown by leuconostocs, lactobacilli and Bacillus polymyxa. Mozzarella was spoiled by B. polymyxa and Bacillus macerans. Semihard cheeses were affected by spore‐forming (Clostridium and Bacillus), propionic and lactobacilli strains. Clostridia, Bacillus, leuconostocs and heterofermentative lactobacilli were detected in pasteurized milk. Bacillus strains were not previously associated with blowing in soft and semihard cheeses.     

PURIFICATION AND CHARACTERIZATION OF A PROTEASE FROM THE PYLORIC CAECA OF MENHADEN (Brevoortia spp) AND MULLET (Mugil spp) FROM THE SOUTHWEST ATLANTIC REGION

A protease classified as trypsin was isolated and purified from the pyloric caeca of two species of fishes: Brevoortia spp (menhaden) and Mugil spp. (mullet). The characterization of both enzymes as trypsin was based on their molecular weight (24 kDa) determined by SDS-PAGE, their inhibition by some known trypsin inhibitors (PMSF, SBTI, TLCK and benzamidine), and their ability to hydrolyze the synthetic trypsin substrate N-α-Benzoyl-DL-arginine-p-nitroanilide (BAPA). Menhaden trypsin had maximum activity at pH 9.5 and was stable for 30 min between pH 6.0 and 10.0 at 0, 10 and 25C. On the other hand, mullet trypsin showed maximum activity at pH's from 7.8 to 9.0, and was stable over a wider pH range (7.0–10.0). The optimum temperature for menhaden and mullet trypsin was 63C and 60C respectively. Thermostability for menhaden trypsin was up to 50C, whereas mullet trypsin was stable up to 60C. The Km(BAPA) values for menhaden trypsin were conserved in the temperature range from 10 to 30C, while for mullet trypsin the Km(BAPA) was conserved between 10 and 25C.     

A multiaxial fatigue criterion for random loading

ABSTRACT A multiaxial fatigue criterion for random loading is proposed. Firstly, the orientation of the critical plane, where fatigue life estimation is carried out, is determined from the weighted mean position of the principal stress directions. Then, the scalar value of the normal stress vector N (t) perpendicular to the critical plane is taken as the cycle counting variable since the direction of such a vector is fixed with respect to time (conversely to the time‐varying direction of the shear stress vector C (t)), and a nonlinear combination of normal and shear stress components acting on the critical plane is used to define an equivalent stress amplitude. Finally, a damage accumulation model is employed to process such an equivalent stress amplitude and to determine fatigue endurance. This criterion is herein applied to some relevant random fatigue tests (proportional bending and torsion).     

Latent crack path and service life predictions for unnotched concrete under bending by digital speckle correlation method

The critical factor for flexural fracture of an unnotched concrete structure is the local damage with stress concentration. The latent critical crack path on the concrete surface is difficult to inspect using ordinary experimental methods. In the present paper, the digital speckle correlation method (DSCM) is employed to obtain the latent critical crack and to calculate the strain and displacement distributions on the surface of unnotched concrete under flexural load. The relationships of static flexural load versus longitudinal strain and load-direction displacement as well as fracture toughness are inherent material parameters. Furthermore, the cohesive energy density (CED) around the latent critical crack for unnotched concrete and the brittleness number are also determined by using the DSCM results. Then, the tensile performance of concrete and the residual service life are evaluated through the above material parameters. It is found that the latent crack path on the concrete surface depends on the strain fields after the bending force applied to the specimen reaches 30% of concrete flexural strength, and the cohesive stress does not rapidly increase until reaching 75% of concrete flexural strength. The service life of unnotched concrete without steel bars is dependent on the local cohesive performance around the latent crack path. Finally, the experimental results show that DSCM is useful to confirm the connection between the local damage of the material and the whole structure safety.     

A study of the interaction of sodium dodecyl sulphate with the proteins of human heel stratum corneum

The aim of this research is to study the in vitro interaction of the anionic surfactant sodium dodecyl sulphate with human heel callus with special regard to the callus proteins.
The sorption of SDS by callus is analysed at different pH values, demonstrating the expected maximum binding of the anionic surfactant at low pH. In both surfactant and blank solutions, swelling of the callus pieces occurs but to different extents. The sorption of SDS by callus is accompanied by a loss of free amino acids and proteins. The protein composition of the callus residues after chemical treatment and of the corresponding treatment baths is examined by amino acid analysis and shows differences in the respective molar amino acid ratios. Results obtained with more specific techniques, such as gel electrophoresis and immunoblotting, demonstrate identical as well as different protein components in the treatment baths depending on the experimental conditions (pH, blank or SDS). Although effects due to the surfactant treatment are in principle more distinct than with blank experiments, those of the latter cannot be neglected.     

EFFECT OF ANTEMORTEM JOURNEY AND LAIRAGE AT ABATTOIR ON RABBIT MEAT QUALITY

A study was conducted to determine the effects of journey duration (1 versus 3 h) and lairage time at abattoir (0 versus 5 h) on rabbit meat quality traits. Rabbits transported for 3 h produced meat with significantly higher pH values ( P <  0.01), darker (lower L* values, P <  0.01) and less yellow ( P <  0.05) color, as well as lower losses during cooking ( P <  0.01), than those transported for 1 h. Moreover, animals laired for 5 h yielded meat with more ( P <  0.05) yellow color, cooking losses ( P <  0.05) and higher shear values ( P <  0.01) than rabbits not laired before slaughtering. The nuclear magnetic resonance analysis revealed that these differences ( P <  0.05) are mainly related to changes occurring in the distribution of myofibrillar (T₂₁) and extra-myofibrillar (T₂₂) water. In conclusion, this study indicated that journey time and lairage at abattoir may play an important role in determining rabbit meat quality traits.

PRACTICAL APPLICATIONS

In many previous studies that considered the effect of journey and lairage on rabbit meat quality, animals were stress-induced by extreme conditions of journey and/or lairage that were unlikely to occur during commercial operations. The aim of this study is to establish whether meat quality characteristics are still influenced when journey and lairage times match current commercial production practices. Because processing-plant efficiency depends on product uniformity, it will be interesting to test the potential variability effect of rabbit preslaughter practices on meat quality properties.