The effect of inulin as a prebiotic on the production of probiotic fibre-enriched fermented milk

We investigated the effect of inulin as a prebiotic on the production of probiotic fibre-enriched fermented milk. The kinetics of acidification of inulin-supplemented milk (0, 0.01, 0.02 and 0.04 g/g), as well as probiotic survival, pH and firmness of fermented milk stored at 4°C for 24 h and 7 days after preparation were examined. Probiotic fibre-enriched fermented milk quality was influenced both by the amount of inulin and by the co-culture composition. Depending on the co-culture, inulin addition to milk influenced acidification kinetic parameters, probiotic counts, pH and the firmness of the product.     

TRANSIENT NATURAL DRYING-INDUCED BOUNDARY LAYERS

ABSTRACT

This work presents a methodology far obtaining heat and mass transfer coefficients for problems involving natural convection along a flat plate. In order to simulate drying conditions, a set of data has been obtained for the temperature range between 20 and 98° C and for various absolute humidities, both of the wall and ambient. It is shown that for drying at temperatures above 80° C, Nusselt and Sherwood numbers change very appreciably with respect to values obtained at smaller temperatures. The simulated results show that even for very low temperature differences, the transient period in natural convection along a flal vertical plate is smaller than 3s.     

EVALUATION OF THE PROTEOLYTIC SUSCEPTIBILITY OF THREE LECTINS FROM SUBTRIBE DIOCLEINAE USING ENZYMATIC ACTION, HEAT TREATMENT AND MOLECULAR MODELING

The enzymatic digestion of the lectins from Canavalia brasiliensis, Dioclea grandiflora and Cratylia floribunda seeds was investigated by heat treatment and gel filtration chromatography. The potential sites of lectin cleavage by pepsin and trypsin was then determined by molecular modelling of the three-dimensional structure of D.grandiflora lectin. The lectins were shown to be susceptible to proteolytic cleavage using peptide mapping with the FPLC system. However, new peptides arose when hydrolysis was followed by heat treatment at 73C. According to the molecular model of D.grandiflora lectin, there are numerous sites for pepsin and trypsin proteolysis on the surface of the protein. It is suggested that when subjected to enzymatic action, the resulting peptides interact in order to retain the general folding of the protein. This is attributed, at least in part, to the numerous hydrogen bonds and hydrophobic interactions occurring within the inner protein structure. After heat treatment the additional cleavage sites become available and the lectins become completely inactivated .     

The influence of water activity on thermal stability of horseradish peroxidase

The thermal stability of horseradish peroxidase in the solid state was studied as a function of water activity, from 0.11 to 0.88. At all activities the enzyme was found to be much more stable in the solid state than in solution. Inactivation temperatures were in the range of 140–160°C. Inactivation curves show a biphasic behaviour which can be described by a model assuming two fractions (heat labile and heat stable) with independent first order inactivation kinetics. The labile fraction represents approximately 30% of the total activity. The z-value for both stable and labile fractions depends on water activity (moisture content) and has a maximum at a_w= 0.76 (44.4°C and 43.8°C, respectively).     

NUTRITIVE VALUE OF OPAQUE-2 CORN AND ITS MIXTURE WITH HYBRID CORN AND WHEAT FLOUR

SUMMARY— A study was carried out to evaluate the nutritive value of opaque-2 corn grown in Brazil and the nutritional effects of its mixture with hybrid corn and wheat flour. These studies were conducted with rats to determine the growth rate, feed efficiency and protein efficiency ratio. Amino acid analyses of Brazilian opaque-2 corn confirmed its high lysine content and other differences in amino acid content; nutritive value was shown to be similar to the American variety. There were small variations among samples of opaque-2 corn grown in different regions and crop years, but all had high nutritive value. The nutritive value of the hybrid corn was little improved by its mixture with the high lysine opaaue-2 corn. Better results were found when the opaque-2 was mixed with the wheat flour.     

Influence of large solid spherical particles on the residence time distribution of the fluid in two-phase tubular flow

The effect of large solid particles on the residence time distribution of the fluid in two-phase flow was studied in a pilot scale continuous tubular system. The residence time distribution was characterized with four parameters: the normalized minimum and mean residence time, the normalized standard deviation and the skewness. The effect of particle concentration (1 and 3%) and particle diameter (diameters approximately 0.3 and 0.4 of the tube diameter) were analysed for fluids with different viscosities and at different flow rates. It was observed that the presence of particles, even at very low concentration, has a significant effect, increasing the mean residence time and decreasing the standardized dispersion. This effect was attributed to particles breaking the velocity profile of the fluid and causing some localized mixing due to their rotational velocity. Although the presence of particles affected the results, their concentration (or number) was not relevant, in the range tested, which is very low for particulate foods.     

Core-shell CdS/Cd(OH)2 quantum dots: synthesis and bioconjugation to target red cells antigens

We report a new and efficient methodology of labelling red blood cells, in order to investigate the expression of anti-A antigen, employing luminescent semiconductor nanocrystals. Highly luminescent and stable core-shell cadmium sulphide/cadmium hydroxide [CdS/CdS(OH)₂] colloidal particles were obtained in the nanometre size range. The surface of these particles was characterized by using a monoclonal anti-A antibody via a one-step glutaraldehyde cross-linking procedure, followed by conjugation of the particles to red cells of blood groups A⁺, and O⁺. Laser scanning confocal microscopy images indicated that after conjugation for 30 min, A⁺ and erythrocytes presented different patterns of dual bright emission whereas the O⁺ group cells showed no emission. We suggest that this labelling procedure may be applied as a quantitative tool to investigate the distribution and expression of alloantigen in red blood cells.     

Crystalline phases found in rapidly quenched Ni–Nb–Zr alloys

The properties of metallic alloys can be significantly improved by developing non‐equilibrium phases in the microstructures through rapid solidification techniques, thus the characterisation of these unusual structures is extremely important. In this research, the microstructures of three rapidly quenched alloys, namely Ni_65.2Nb_33.8Zr_1.0, Ni_54.8Nb_31.1Zr_14.1 and Ni_54.8Nb_21.6Zr_23.6 (at. %) were investigated in greater detail in order to determine the structures and compositions of their crystalline phases. These crystalline phases were characterised using a combination of scanning electron microscopy, energy dispersive x‐ray spectroscopy, x‐ray diffraction and transmission electron microscopy techniques. The phases were compared to the crystalline structures reported in the literature. Our results indicate some agreement with the Ni–Nb phase diagram and an isothermal section of the Ni–Nb–Zr phase diagram; however, it is detected zirconium solubility in the Ni₃Nb phase, as well as, the absence of expected crystalline phases.