Caracterização físico-química de amostras de mel de abelha africanizada dos municípios de Santa Helena e Terra Roxa (PR) / Physicochemical parameters of honey from samples from africanized honeybees in Santa Helena and terra roxa counties (PR)

O presente estudo teve como objetivo a caracterização físico-química de amostras de mel de Apis mellifera coletadas nos municípios de Santa Helena e Terra Roxa, localizados na região oeste do Estado do Paraná, Brasil. Foram coletadas 40 amostras de mel, sendo 20 do município de Santa Helena e 20 de Terra Roxa (PR), coletadas diretamente com os apicultores, as quais foram submetidas a análises físico-químicas de umidade, acidez, pH, cinzas, condutividade elétrica e cor, a fim de verificar se as mesmas apresentavam-se em conformidade com a legislação nacional vigente (Instrução Normativa nº 11), além de conhecer o perfil físico-químico do mel das diferentes localidades, na safra 2008/2009. Os dados encontrados foram submetidos à análise de variância e teste F a 5% de significância. Os resultados apresentaram diferença significativa (P<0,05) apenas entre os valores de acidez, tendo o mel oriundo de Terra Roxa apresentado valor mais alto (33,45±7,7meq.kg-1) que o de Santa Helena (24,53±6,3meq.kg-1). Em sua maioria, as amostras analisadas encontraram-se dentro das especificações determinadas pela legislação para as características físico-químicas, com exceção do parâmetro de umidade, que, apesar de não ter apresentado diferença significativa entre os valores encontrados para os dois municípios, estavam acima do limite estabelecido pela legislação (20 por cento) em 8 amostras do município de Santa Helena e em 7 de Terra Roxa, totalizando 37,5 por cento) das amostras. Essa característica pode ter deixado o produto mais susceptível à fermentação e pode ter sido ocasionada pela colheita imatura do mel...

This study aimed to physicochemically characterize the honey samples of Apis mellifera collected in Santa Helena and Terra Roxa counties, located in the western region of Paraná State, Brazil. Forty honey samples were collected, 20 in Santa Helena and 20 in Terra Roxa (PR) counties, directly from beekeepers, and were subjected to physico-chemical analyzes of moisture, acidity, pH, ashes, electrical conductivity and color, to verify whether they were in accordance with the existing national legislation (Instruction No. 11), in addition to knowing the physicochemical profile of different sites during the 2008/2009 season. The data were submitted to analysis of variance and F test at 5 percent significance level. The results showed significant differences (P<0.05) between values of acidity, and the honey samples from Terra Roxa presented a higher value (33.45±7.7 meq.kg-1) than Santa Helena (24 = 53±6.3 meq.kg-1). Most of the analyzed samples were within the specifications prescribed in the legislation for the physico-chemical parameters except for moisture, which despite having presented a significant difference between values obtained from two counties, were above the limits established by the legislation (20 percent) in eight samples in Santa Helena and seven in Terra Roxa counties, totaling 37.5 percent. This characteristic may have made the product more susceptible to fermentation, and may have been caused by harvesting immature honey...

Inactivation of foodborne pathogens in milk using dynamic high pressure.

Improving the microbiological safety of perishable foods is currently a major preoccupation in the food industry. The aim of this study was to investigate the inactivation of three major food pathogens (Listeria monocytogenes [LSD 105-1], Escherichia coli O157:H7 [ATCC 35150], and Salmonella enterica serotype Enteritidis ATCC [13047]) by dynamic high pressure (DHP) in order to evaluate its potential as a new alternative for the cold pasteurization of milk. The effectiveness of DHP treatment against L. monocYtogenes, E. coli O157:H7, and Salmonella Enteritidis was first evaluated in 0.01 M phosphate-buffered saline (PBS) at pH 7.2 as a function of applied pressure (100, 200, and 300 MPa) and of the number of passes (1, 3, and 5) at 25 degrees C. A single pass at 100 MPa produced no significant inactivation of the three pathogens, while increasing the pressure up to 300 MPa or the number of passes to five increased inactivation. From an initial count of 8.3 log CFU/ml, complete inactivation of viable L. monocytogenes was achieved after three successive passes at 300 MPa, while 200-MPa treatments with three and five passes completely eliminated viable Salmonella Enteritidis and E. coli O157:H7, respectively. The effectiveness of DHP for the inactivation of these pathogens was compared to that of hydrostatic high pressure (HHP) using the same pressure (200 MPa, single pass at 25 degrees C). In general, two additional log reductions in viable count were obtained with DHP DHP was less effective against L. monocytogenes and E. coli O157:H7 in raw milk than in PBS. After five passes at 200 MPa, an 8.3-log reduction was obtained for E. coli O157:H7, while a reduction of about 5.8 log CFU/ml was obtained for L. monocytogenes exposed to 300 MPa for five passes. Exposing milk or buffer samples to mild heating (45 to 60 degrees C) prior to dynamic pressurization enhanced the lethal effect of DHP The inactivation of pathogens also depended on the initial bacterial concentration. The highest reduction was obtained when the bacterial load did not exceed 10(5) CFU/ml. In conclusion, DHP was shown to be very effective for the destruction of the tested pathogens. It offers a promising alternative for the cold pasteurization of milk and possibly other liquid foods.

High-resolution imaging of laser-produced plasmas at a wavelength of 130 A by a normal-incidence multilayer-mirror microscope.

Laser-produced plasmas were imaged by a microscope consisting of spherical, primary, and secondary mirrors in a Cassegrain-type optical configuration. The mirrors were coated with 40 periods of Mo and Si and had a peak reflectance of ∼60% at a wavelength of 130 Å. Nb, Au, and Al targets were irradiated by as many as 24 beams of the Omega laser at the Laboratory for Laser Energetics at the University of Rochester. The images were recorded on Kodak 101 film, and the resolution was limited by the 10-µm emulsion grain size. Two different secondary mirrors produced images with a magnification of 0.8 or 2.2, and a variety of plasma emission features were recorded with 5-µm (0.6-arcsec) resolution in the target plane. The possibility of operating a similar microscope in the wavelength region of 34-50 A is discussed.

Helicoidal self-ordering of cellulose microfibrils in aqueous suspension.

In many skeletal support systems of plants and animals, cellulose, chitin, and collagen occur in the form of microfibrils ordered in a chiral nematic fashion (helicoids). However, these structures remain poorly understood due to the many constituents present in biological tissues. Here we report an in vitro system that attracts by its simplicity. Only one chemical component, cellulose, is present in the form of fibrillar fragments dispersed in water. Above a critical concentration the colloidal dispersion separates spontaneously into a chiral nematic liquid crystalline phase. On drying this phase solidifies into regularly twisted fibrillar layers that mimic the structural organization of helicoids in nature.