Bacteriological evaluation of goat milk and cheese distributed in the Metropolitan Area of San José, Costa Rica

In the last years, there has been an increase in the production, industrialization and consumption of goat's milk and derivate products, including cheese, worldwide. Nevertheless, in Costa Rica there is no study of these products, reason why the objective of this work was to determine the microbiological characteristics of goat's milk and fresh cheese distributed in the Metropolitan Area of San José, Costa Rica, in order to evaluate its impact in the economical field and as a potential risk for Public Health. A total of 25 raw goat's milk samples, obtained by manual milking from 5 different producers tested in five different dates and 15 cheese samples, elaborated with pasteurized milk, commercially available and coming from three different producers were analyzed. The study included the analysis of spoilage bacteria (total aeobic count and lactic bacteria count), indicators of hygiene (total coliforms), fecal contamination (fecal coliforms), manipulation (Staphylococcus aureus) and pathogens (Listeria monocytogenes and Salmonella spp). High results were obtained for the total aerobic count and lactic bacteria count of the milk and cheese samples, showing a reduced shelf life. Total coliforms, in limits beyond the established ones by the Costa Rican legislation for human consumption raw milk, were found in 100% of milk samples, as well as for fecal coliforms in 76% of them. All cheese samples, except one, were negative for these indicators, suggesting good manufacturing practices. S. aureus counts were low and both Salmonella spp. and L. monocytogenes were not isolated from samples analyzed.     

Evaluation of the polymerase chain reaction (PCR) for the detection and identification of Listeria monocytogens in fresh cheese coming from the metropolitan area of San José, Costa Rica

Food borne diseases are very important worldwide and their frequency is still high despite the different efforts focused in diminishing their morbidity and mortality. Listeria monocytogenes is one of the agents associated in this kind of diseases. In the lactic industry, this bacteria is important since raw milks as well as dairy products have been associated in outbreaks, being fresh cheese one of the most vulnerable products to the contamination with this bacteria. The traditional identification of the bacteria is done by a laborious, time consuming and low sensitive technique and the polymerase chain reaction may allow more precise and exact results in shorter time. For this reason the objective of the present study was to optimize the procedure to determine the sensitivity and specificity limits for the detection of L. monocytogenes from fresh cheese and the predictive value of the test. In order to achieve this objective, 76 pasteurized cheese samples were evaluated (45 samples were artificially inoculated at the lab and 31 were used as negative controls). The validation of the technique was done in 50 samples of non pasteurized fresh cheese. Traditional culture isolation was performed according to the methodology described in Compendium of Methods for the Microbiological Examination of Foods. PCR reaction for the detection of L. monocytogenes was based on the methodology described by Poutou,using primers characteristic of the genus and the listeriolisine O gene that is specie's specific. The optimal incubation period determined for the selective enrichment broth was of 48h, and a 100% sensitivity, specificity, predictive value (positive and negative) were obtained by PCR. The technique validation showed the specificity ofthe test in the detection of only the L. monocytogenes species, and not other genus or species that may appear in food matrixes or in food environments.     

Evaluation of the presence of bacteria in food and environment of an Oncological Service of a National Hospital, San José, Costa Rica

The microbiological quality of 92 samples from the Oncological Service of a National Hospital, San José, Costa Rica was evaluated during the months of February to July, 2002. Of these samples, 48 were from salads, refreshments, and fruits and 44 from surfaces, air and hands of the medical personnel. The presence of total and fecal coliforms was determined by the total plate count technique, using Violet Red Bile Agar for the isolation of total and fecal coliforms, Baird-Parker Agar for Staphylococcus aureus, Cetrimide Agar for Pseudomonas and Listeria was enriched in University of Vermont Broth, Fraizer Broth and isolated in Oxford Agar. From the food samples analyzed, 77% were positive for at least one of the parameters studied; the fruits presented the greater contamination (94%) and the cooked salads the minor, even though Listeria was isolated in 13% of them. All tested salads (100%) were positive for fecal coliforms. Pseudomonas and S. aureus were isolated from fruits, raw salads, and refreshments. All the analyzed surfaces, with an exception, were negative for the parameters evaluated. 75% of the hands of the medical personnel were positive for at least one of the parameters evaluated; 25% had total coliforms (2.8x10(3) UFC/hand), 13% fecal coliforms (2.4x10(3) UFC/ hand), 69% S. aureus (1.3x10(3) UFC/hand) and 19% Pseudomonas sp. 115 isolates were randomly selected, and identified using miniaturized tests (API). When comparing these identifications with the 166 isolations done at the Clinical Laboratory of the Hospital from the infected patients of oncology, by means of variance analysis, it was determined that both bacterial populations were statistically similar.     

Possible Negative Value of the Grüneisen Coefficient of Hydrogen in the Area of Pressures from 40 to 75 GPa and Temperatures from 3500 to 7500 K

Experimental data on single and double shock compression of initially liquid and gaseous (compressed by initial pressure) hydrogen isotopes (protium and deuterium) at pressures of ≈10–180 GPa and temperatures of ≈3000–20 000 K are considered. The mean values of the measured variables (pressure, density, internal energy, and temperature) show that hydrogen at a pressure of ≈41 GPa in the temperature interval of ≈3500–5700 K and at a pressure of ≈74 GPa in the temperature interval of ≈5000–7500 K is characterized by a negative value of the Grüneisen coefficient. Such an anomaly may play a key role in some processes, including those proceeding in the Jupiter gas envelope, which mainly consists of protium (≈90%) and helium (≈10%). In the range of pressures (depths) of its manifestation, convection in the protium envelope is forbidden with an increase in temperature in the envelope with increasing pressure. Possibly, a comparatively low fraction of helium does not suppress the anomaly, and it serves as a barrier for large-scale convection in the Jupiter envelope. Additional refining experiments are required to confirm this anomaly.     

A cylindrical photoreactor irradiated from the bottom—II. Models for the local volumetric rate of energy absorption with polychromatic radiation and their evaluation

This study of the radiation field generated in a cylindrical photoreactor irradiated from the bottom presents the theoretical foundations of a method for the experimental verification of three different radiation models. The expressions representing the local volumetric rate of energy absorption (LVREA) were formulated and applied to the prediction of the rate of an actinometric reaction. This reaction takes place inside a microreactor operated in a batch recycling system with polychromatic radiation.The values obtained portray the same behaviour as that of the energy densities calculated previously (Part I), thus becoming a valid, accurate method for the experimental measurement of the absolute values of the radiation field that are sought after (volumetric rate of energy absorption).The proposed approach is able to produce quasi-point values of the absolute values of the VREA at the microreactor as an excellent approximation to the absolute values of the LVREA (local measurements).The present work also points out the qualitative and quantitative discrepancies of the results predicted by the line models when compared with those of the extense source model with volumetric emission.     

Synthesis and evaluation of different adsorbents based on poly(methacrylic acid–trimethylolpropane trimethacrylate) and poly(vinylimidazole–trimethylolpropane trimethacrylate) for the adsorption of tebuthiuron from aqueous medium

In the present study a new cross-linked copolymer poly(methacrylic acid–trimethylolpropane trimethacrylate) (named PMA) and poly(vinylimidazole–trimethylolpropane trimethacrylate) (named PVI) was synthesized through precipitation polymerization and applied to the adsorption of tebuthiuron. Adsorbent materials were characterized by using FT-IR, SEM, TGA, textural data, and elemental analysis. Kinetic study showed that the tebuthiuron adsorption was very quick and the equilibrium time was achieved at 20 min for both polymers. Experimental kinetic data for both polymers were very well described by the second-order kinetic model, thus indicating that tebuthiuron adsorption involves chemical adsorption in different binding sites, which could control the reaction rate. Adsorption equilibrium data were better fitted to the dual-site Langmuir–Freundlich model, which recognizes the existence of two kinds of adsorption sites on the polymer surface ascribed to the presence of carboxyl and carbonyl groups from PMA and imidazole ring and carbonyl group from PVI. The maximum adsorption capacities of PMA and PVI were found to be 186.76 and 213.89 mg g^− 1, respectively, which are much higher than other adsorbents.     

Determination of Essential Fatty Acids in Captured and Farmed Matrinxã (<Emphasis Type="Italic">Brycon cephalus</Emphasis>) from the Brazilian Amazonian Area

The aim of this research was to quantify the methyl esters of linoleic (LA), α-linolenic (LNA), arachidonic (AA), eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids in the muscular tissue and orbital cavity of farmed Matrinxã (Brycon cephalus) and in those caught in the Brazilian Amazonian Area during two periods. For the farmed fish, the amounts (mg/g of fat) of LA, LNA, AA, EPA, and DHA found in the muscle were 197.6, 75.7, 165.0, 4.1, and 30.0 mg/g of fat, respectively. The amounts of these FA in the orbital cavity were 152.6, 9.1, 249.4, 3.6, and 22.3 mg/g of fat for LA, LNA, AA, EPA, and DHA, respectively. For the fish caught during the wet period, the LA, LNA, AA, EPA, and DHA found in the muscle were 438.2, 118.3, 42.7, 5.2, and 10.3 mg/g of fat, in the orbital cavity were found 489.1, 18.6, 18.1, 6.2, and 18.7 mg/g of fat, respectively. In the dry season, the amounts (mg/g of fat) of LA, LNA, AA, EPA, and DHA in the muscle were 193.1, 40.0, 43.4, 8.1, and 61.3, while the found in the orbital cavity were 152.9, 28.4, 5.1, 4.9, 19.6 mg/g of fat. According to their contents of EPA, and DHA, matrinxã captured in the dry season can be considered as a rich source of EFA.     

Influences of dietary n−3 long-chain PUFA on body concentrations of 20∶5n−3, 22∶5n−3, and 22∶6n−3 in the larvae of a marine teleost fish from Australian waters,the striped trumpeter (<Emphasis Type="Italic">Latris lineata</Emphasis>)

We determined the effect of dietary long-chain (≥C₂₀) PUFA (LC-PUFA), 20∶5n−3 and 22∶6n−3, on larval striped trumpeter (Latris lineata) biochemistry through early development and during live feeding with rotifers (Brachionus plicatilis). Rotifers were enriched using seven experimental emulsions formulated with increasing concentrations of n−3 LC-PUFA, mainly 20∶5n−3 and 22∶6n−3. Enriched rotifer n−3 LC-PUFA concentrations ranged from 10–30 mg/g dry matter. Enriched rotifers were fed to striped trumpeter larvae from 5 to 18 d post-hatch (dph) in a short-term experiment to minimize gross deficiency symptoms such as poor survival that could confound results. No relationships were observed between larval growth or survival with dietary n−3 LC-PUFA at 18 dph. The larval FA profiles generally reflected those of the rotifer diet, and significant positive regressions were observed between most dietary and larval FA at 10, 14, and 18 dph. The major exception observed was an inverse relationship between dietary and larval 22∶5n−3. The presence of 22∶5n−3 in elevated amounts when dietary 22∶5n−3. The presence of 22∶5n−3 in elevated amounts when dietary 22∶6n−3 was depressed suggests that elongation of 20∶5n−3 may be occurring in an attempt to raise body concentrations of 22∶6n−3. We hypothesize that accumulation of 22∶5n−3 might be an early indicator of 22∶6n−3 deficiency in larval fish that precedes a reduction in growth or survival. A possible role of 22∶5n−3 as a biochemical surrogate for 22∶6n−3 is discussed.