Raquel Stefanello

Determination of aluminum as contaminant in dialysis concentrates by adsorptive cathodic stripping voltammetry

This paper describes a stripping voltammetric method for the determination of aluminum as contaminant in dialysis concentrates. It is based on the adsorptive deposition of the complex Al-1,2-dihydroxyanthraquinone-3-sulfonic acid (DASA) at the hanging mercury drop electrode (HMDE) at -0.9V (versus Ag/AgCl) and its cathodic stripping during the potential scan. The method was optimized concerning the main electrochemical parameters that influence the voltammetric determination in highly saline solutions (sample dilution factor, deposition time and DASA concentration). The linear range for the measurements was from <LOD to 30μgl-1 with a detection limit calculated as 0.8μgl-1 for a deposition time of 15s. Aluminum recoveries between 91.0 and 105.5% for spiked samples of dialysis concentrates proof the accuracy of the proposed voltammetric method. The method allows the rapid aluminum determination at μgl-1 levels in the presence of Zn(II) as interfering ion, and it was applied to its determination in commercial dialysis concentrates used routinely by hemodialysis centers in Brazil. Aluminum concentrations between 9.0 and 78.7μgl-1 were determined in five different samples of three kinds of dialysis concentrates.

Determination of cadmium, lead and thallium in highly saline hemodialysis solutions by potentiometric stripping analysis (PSA)

Potentiometric stripping analysis (PSA) was investigated to assay simultaneously cadmium, lead and thallium present as contaminants in highly saline solutions used in hemodialysis. The saline matrices were sodium, potassium, magnesium and calcium chlorides, sodium acetate, sodium bicarbonate and glucose, which constitute concentrates for hemodialysis. A 1000mugmL(-1) Hg(II) solution was used to prepare the mercury film electrode (MFE) and to carry out the stripping step. After a 30s accumulation interval the analytes were simultaneously detected in the saline matrices without using masking agents. Determination limits of 80ngL(-1) for cadmium and thallium, and 50ngL(-1) for lead were calculated and a R.S.D. ranging from 0.5 to 2.2% (n = 3) was obtained measuring the analytes directly in commercial hemodialysis saline solutions. Recoveries from spiked samples ranging from 94.6 to 102.0% were obtained. The investigated metals were found in concentrations ranging from 2.7 to 5.7mugL(-1) for cadmium, 27.7 to 75.8muL(-1) for lead and 9.6 to 18.7mugL(-1) for thallium in commercial hemodialysis solutions. The PSA method showed to be adequate to the quality control of saline concentrates for hemodialysis.

Efeito da luz, temperatura e estresse hídrico no potencial fisiológico de sementes de funcho

The objective of this study was to evaluate the effects of light, temperature and hydric stress on the germination and vitality of fennel seeds.. First, the seeds were sowed on paper at constant temperatures of 20, 25, 30oC or alternating temperatures of 20-30oC in the presence or absence of light. In a second step, seeds were kept on paper in aqueous polyethylene glicol (PEG 6000) at the osmotic potentials equivalent to zero; -0,05; -0,10; -0,15; -0,20; -0,25;-0,30MPa. According to the results, it was possible to conclude that germination of fennel seeds occurred in presence or absence light. The fennel seeds germinated better at constant temperatures of 20 and 25oC but 30oC was not useful for the germination test. The decrease in the osmotic potentials reduced the germination and vigor of fennel seeds, and vigor was more affected than germination. The germination was drastically reduced, starting at -0,1 MPa for fennel when there was a decrease in the osmotic potentials with polyethylene glicol 6000.

PHYSIOLOGICAL AND SANITARY QUALITIES OF MAIZE LANDRACE SEEDS STORED UNDER TWO CONDITIONS

The preservation of seed quality during the storage period depends not only on the conditions during production and harvesting but also on the storage and maintenance of appropriate storage product conditions. Thus, the aim of this study was to evaluate the physiological and sanitary qualities of maize landrace seeds stored under two conditions. The maize seed batch varieties Oito carreiras, Cabo roxo and Lombo baio were used. Tests included germination, first count, cold test, accelerated aging and sanity. Based on the results it was concluded that the physiological quality of these seed varieties decreased with the storage period. The major fungi identified in the maize seeds during storage were from the genera Aspergillus, Fusarium and Penicillium, which caused deterioration and reduction of the physiological quality. Storage using a paper bag at a temperature of 10 °C did not prevent the deterioration of maize seeds but was more effective at preserving the quality of the seed compared with a plastic bag at room temperature.

Stability, sensory attributes and acceptance of panettones elaborated with Lactobacillus fermentum IAL 4541 and Wickerhamomyces anomallus IAL 4533

This work aimed to elaborate sourdough panettones with Lactobacillus fermentum (LF) and Wickerhamomyces anomallus (WA) evaluating their microbiological stability, physical and chemical characteristics as well as the impact of these microorganisms on sensory aspects and consumer acceptance. For characterization, panettones were elaborated by long fermentation, using two selected microorganisms, LF and WA in different proportions; and control panettones were formulated using commercial yeast with and without preservative. For sensory analyses, LF, WA, LF/WA (1:1), control with calcium propionate and commercial panettones were compared. Regarding the pH values and total titratable acidity (TTA), a similar behavior was observed among panettones elaborated with the selected strains (LF, WA and mixtures). On the other hand, panettones elaborated with commercial yeast showed a higher pH and lower TTA. Until the 112nd day of storage, the water activity (aw) was similar among all panettones, but in the following analyses, it dropped in all panettones. Panettones elaborated with sourdough maintained better their softness during the storage, when compared with the controls. Regarding microbial stability, control panettones with and without preservative became moldy faster; while sourdough panettones (WA and LF/WA) remained stable throughout all the monitored storage. Sensory evaluation by CATA allowed distinguishing between sourdough and commercial yeast panettones. Desirable characteristics such as nice aroma, pleasant taste and uniform color were checked more often for LF and WA elaborated panettones, whereas yeast flavor was checked more often for the Commercial. Moreover, according to the descriptors used, panettones were grouped into 3 groups: LF/WA, LF + WA and controls. The panettones elaborated with the specific microorganisms of this study were well-accepted sensorially, proving to be very competitive with respect to control and commercial panettone. So, the use of selected microorganisms as a starter for sourdough is a promising alternative for producing panettones with good technological quality, microbiological stability, sensorially differentiate and well accepted by consumers; and, additionally, with the appeal of no added preservative.

Natural conservation attached to the use of microorganisms

In this paper we developed a numerical methodology to study some incompressible fluid flows without free surface, using the curvilinear coordinate system and whose edge geometry is constructed via parametrized spline. First, we discussed the representation of the Navier-Stokes and continuity equations on the curvilinear coordinate system, along with the auxiliary conditions. Then, we presented the numerical method – a simplified version of MAC (Marker and Cell) method – along with the discretization of the governing equations, which is carried out using the finite differences method and the implementation of the FOU (First Order Upwind) scheme. Finally, we applied the numerical methodology to the parallel plates problem, lid-driven cavity problem and atherosclerosis problem, and then we compare the results obtained with those presented in the literature. keyword: finite difference method, simplified MAC method, curvilinear coordinate system, parallel plates problem, lid-driven cavity problem, atherosclerosis problem MSC[2010]: 35Q30, 76M20, 35A30

Survival and stability of Lactobacillus fermentum and Wickerhamomyces anomalus strains upon lyophilisation with different cryoprotectant agents

The stability of microorganisms along the time is important for allowing their industrial use as starter agents, improving fermentation processes. This study aimed to evaluate the survival and maintenance of the cell viability of the lactic acid bacteria Lactobacillus fermentum IAL 4541 and the yeast Wickerhamomyces anomalus IAL 4533, both isolated from wheat sourdough, after lyophilisation with different cryoprotectant and storage at room temperature along a year. Treatments involved adding control solution (S1 = 0.1% peptone water), and four cryoprotectant solutions S2 (10% sucrose), S3 (5% trehalose), S4 (10% skim milk powder) and S5 (10% skim milk powder plus 5% sodium glutamate) to the microbial cells previously of freeze drying processing. To verify the effect of lyophilisation on the number of microbial cells recovered, microbiological analyses were performed and cell viability was calculated before and after lyophilisation and regularly during a storage period of 365 days at room temperature. Viability after freeze-drying was influenced by the cryoprotectant agent employed, as well the microbial stability conferred along the storage. Differences on the microorganism response to some protectors were observed between the lactic acid bacteria and the yeast evaluated. W. anomalus was more affected by absence of cryoprotectant (S1) during freeze drying processing, but this microorganism was more stable than L. fermentum along the storage without the presence of protectant agents. For L. fermentum, S5 was the best protectant, allowing the recovering of 100% of the bacterial cells after lyophilisation and 87% of cell viability was observed after one year storage, followed by S4 (96 and 74%, respectively). S4 and S5 were the best protectant to W. anomalus (viability >80% after 1 year), but no increase in the yeast cell viability was conferred by addition of glutamate (S5) to skim milk. After 1 year of storage, trehalose was much more effective on protection of the yeast than bacteria (72% and 7% of viability, respectively). S2 was the less protectant agent among the tested, and their effectiveness was higher in L. fermentum (allowing 14% of cell recovering up to 120 days of storage) if compared to W. anomalus (25% of viability until 90 days of storage). Our results demonstrate that freeze-drying is a realistic technology for the stability and maintenance of the potential sourdough starter L. fermentum and W. anomalus for long time; however, the choice of cryoprotectant will influence the process effectiveness.

Resposta fisiológica de sementes de chia e linhaça ao estresse hídrico

Studies on water resources are important to understand seed germination. The objective of this study was to evaluate the physiological (germination) response of chia seeds and linseed to water stress. The seeds were placed on paper soaked in solutions of polyethylene glycol in diff erent osmotic potentials. Percentage of germination, fi rst germination count, and germination speed index were evaluated. The reduction of the osmotic potential of the substrate promoted a signifi cant decrease in the germination and vigor of the chia seeds and linseed. In conclusion, seeds of these species are not able to tolerate osmotic potentials equal to or lower than -0.15MPa, being making possible its cultivation areas with concentrations above osmotic potentials.