BACTERIOLOGICAL ANALYSES OF FROZEN SHRIMP. 2. Staphylococci in Precooked Frozen Chilean Shrimp

SUMMARY– 392 samples of precooked frozen shrimp from two Chilean manufacturers, A and B, were quantitatively examined for the presence of Staphylococcus aureus by direct plating on Difco mannitol salt agar (MSA, 10% NaCI). 140 samples (35.7%) were found to contain Staphylococci but only half of these had counts of over 100,82.4% remaining within the acceptable limit. Frozen shrimps are prone to contamination by Staphylococcus during processing, especially if hand-processed, but these results show that it is possible to obtain a good-quality product when stringent sanitary measures are observed. MSA was compared with Baird Parker's egg yolk medium (BPM) by plating simultaneously on it 141 samples from manufacturer B; BPM detected S. aureus in a smaller number of samples (7.8%), and gave rise to fewer colonies than MSA. BPM seemed to be inhibitory even to some Staphylococcus strains, i.e., it is unsuitable for use in these frozen foods. From 2 other manufacturers, C and D, 80 samples of frozen shrimp, together with 60 nasal swab samples from food handlers were plated to investigate some cultural characteristics of S. aureus. 57 strains of this organism were obtained, 41 belonging to shrimp samples and 16 to nasal carriers from both manufacturers. The strains were isolated and, when tested by anaerobic fermentation of mannitol, deep growth in cysteine agar, catalase and coagulase reactions, all gave positive tests. Phosphatase and DNase reactions were less constant. All the strains with 1 exception were sensitive to 8 antibiotics tested. Thus, the general properties ascribed to S. aureus species appear unaltered in frozen shrimps. 28 strains (49.1%) could be typified with the set of 21 international phages, most of them belonging to group III; only in manufacturer D strains coming from food and food handlers were phage type related. In manufacturer C most strains were untypable.     

Electrochemical copolymerization of N-methylpyrrole and 2,2′-bithitiophene; characterization,micro-capacitor study,and equivalent circuit model evaluation

N-methylpyrrole (N-MPy) and 2,2′-bithiophene (BTh) were electrocopolymerized in 0·2 M acetonitrile–sodium perchlorate solvent–electrolyte couple on a glassy carbon electrode (GCE) by cyclic voltammetry (CV). The resulting homopolymers and copolymers in different initial feed ratios of [N-MPy]₀/[BTh]₀ = 1/1, 1/2, 1/5 and 1/10 were characterized by CV, Fourier-transform infrared reflectance attenuated transmittance (FTIR–ATR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS). The capacitive behaviours of the modified electrodes were defined via Nyquist, Bode-magnitude, Bode-phase and admittance plots. The equivalent circuit model of R(C(R)(QR)(CR)) was performed to fit theoretical and experimental data. The highest low-frequency capacitance (C _LF) were obtained as C _LF = ～ 1·23 × 10 ^?4 mF cm ^?2 for P(N-MPy), C _LF = ～ 2·09 × 10 ^?4 mF cm^?2 for P(BTh) and C _LF = ～ 5·54 × 10 ^?4 mF cm^?2 for copolymer in the inital feed ratio of [N-MPy]₀/[BTh] ₀ = 1/2.

Influence of the rheological behaviour of the lubricant on the appearance of pitting in elastohydrodynamic regime

This paper analyses the influence of lubricant behaviour on the appearance of pitting. It attempts to study the effect of viscosity–pressure relation, compressibility, film thickness–roughness relation and friction coefficient on pitting failure of the contacting elements. To explain these effects, we first deal with the influence of the oil on the lubrication of the contact using elastohydrodynamic theory and secondly two multiaxial fatigue criteria are used, Crossland criterion and Dang Van criterion, to evaluate the influence of the rheology on the appearance of pitting. Finally, different applications are presented together with a discussion on the results obtained.     

Comparative informative value of chromosome aberrations and sister chromatid exchanges in the evaluation of metals in the environment

The effects of met-enkephalin, leu-enkephalin, D-Ala2-metenkephalin, and somatostatin on Wenckebach arrhythmia and atrioventricular dissociation was investigated in experiments on anesthesized cats. Arrhythmias were induced by stimulation of the vagus with short repetitive bursts of pulses. Enkephalins evoked a protective effect in both arrhythmias whereas somatostatin had no antiarrhythmic properties. The protective effect of enkephalins persisted after blockage of mu-opiate receptors with naloxone (0.2 mg/kg), but in high doses (2 mg/kg), which blocked both mu- and delta-opiate receptors, antiarrhythmic effects was abolished. It is concluded that the protective effect of enkephalins against vagally induced arrhythmias may be due to the stimulation of delta-opiate receptors located on the presynaptic vagal endings. As a results, stimulation-evoked acetylcholine release is diminished, which prevent the arrhythmogenic effect of the vagus nerve.     

Influence of berry ripeness on concentration,qualitative composition and extractability of grape seed tannins

Background and Aims: The evolution of seed tannins in three grape varieties grown in the same vineyard was followed from preveraison to harvest, to determine their pattern of accumulation. Also, to elucidate whether the use of 70% acetone as extracting solvent overestimate what will occur during fermentation, seed tannins were extracted throughout the ripening period with a method that involved a 3 days extraction with aqueous 12.5% ethanol and the results compared with the acetone extraction method. Methods and Results: For both methods, the extracted tannins were analysed following acid‐catalysis in the presence of excess of phloroglucinol. Seed tannins reached a maximum around veraison and decreased towards maturity, the mean degree of polymerization (mDP) varying only slightly during the studied period. When tannins were extracted with 12.5% ethanol, their concentration was much higher during the first part of the maturation than using acetone but was significantly lower at harvest. Conclusions: The decrease in extractable seed tannins during ripening was observed with both solvents. The differences observed in the concentration of tannins with both solvents could be due to the histochemical changes occurring in seeds during maturation. Significance of the Study: The differences observed in tannin concentration with the two different methods may indicate that when pulp maturity is reached before seeds are ripe, the fermenting solution will extract more tannins than the acetone method. These results point to the importance of extraction methodology when monitoring seed maturity for the prediction of seed tannins in wine.