Reconstruction of the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its digital image: the challenge of algal colours

A novel procedure for deriving the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its image is presented. Any digital image acquired by a microscope can be used; typical applications are the analysis of cellular/subcellular metabolic processes under physiological conditions and in response to environmental stressors (e.g. heavy metals), and the measurement of chromophore composition, distribution and concentration in cells. In this paper, we challenged the procedure with images of algae, acquired by means of a CCD camera mounted onto a microscope. The many colours algae display result from the combinations of chromophores whose spectroscopic information is limited to organic solvents extracts that suffers from displacements, amplifications, and contraction/dilatation respect to spectra recorded inside the cell. Hence, preliminary processing is necessary, which consists of in vivo measurement of the absorption spectra of photosynthetic compartments of algal cells and determination of spectra of the single chromophores inside the cell. The final step of the procedure consists in the reconstruction of the absorption spectrum of the cell spot from the colour values of the corresponding pixel(s) in its digital image by minimization of a system of transcendental equations based on the absorption spectra of the chromophores under physiological conditions.     

Determination of Rheological Behavior of Tomato Concentrates Using Back Extrusion

The back extrusion testing technique can be a very useful tool in assessing the rheological behavior of non-Newtonian fluids (e.g. tomato concentrates). In this procedure, an Instron Model 1122 Universal Testing Machine (with stainless steel, solid rod attachment) was used to measure the forces developed as diluted tomato paste was back extruded in a simple piston/annular cylinder geometry. Assuming power law behavior, the force-distance data for extrusions at different piston velocities were analyzed to yield the dimensionless flow behavior index (n) and the consistency coefficient (k) for each sample. Back extrusion measurements were performed on hot break and cold break tomato concentrates with different % total solids. For comparison, rheological measurements were also done on a set of samples with a Carri-Med Controlled Stress Rheometer.     

PARTIAL CHARACTERIZATION OF A WHEY PROTEIN CONCENTRATE AND ITS ENZYME HYDROLYSATES

A whey protein concentrate (WPC) was produced from fresh whey by ultrafiltration (MW cut off 10 kDa) and lyophilization. Enzymatic hydrolysis was performed with three enzyme systems: pancreatin (PA), protamex (PR) or alcalase 0.6L (AL) to produce hydrolysates with 20% degree of hydrolysis (DH). The peptide profiles of the hydroly sates were determined by high performance capillary electrophoresis (HPCE). The relationship between enzyme system and preferential protein substrate could be established. The alcalase hydrolysate (ALH) differed from the other two hydrolysates, and the enzyme showed the lowest specificity for β‐lactaglobulin. Considering the protein content from WPC the pancreatin hydrolytic system was the most efficient leaving only 4.69% unhydrolyzed protein in the final hydrolysate (PAH). For 20% degree of hydrolysis alcalase left 7.98% unhydrolyzed protein, while protamex left 9.81% unhydrolyzed protein in the final hydrolysate.     

Stability of Saffron Pigments in Aqueous Extracts

The effect of pH, light, temperature and oxygen on the stability of saffron pigments in aqueous extracts has been studied. First-order kinetics for the degradation of saffron pigments was observed for all experimental conditions. Kinetic data were calculated from the values of the coloring power of saffron aqueous extracts.     

DETECTION OF BIOGENIC AMINES AS MEAT SPOILAGE INDICATORS

Preparative ion exchange chromatography was performed on beef and pork samples stored at 4–6°C and wrapped in commercial film (Saran). Different peaks obtained for the two species studied, were attributable to the different type of biogenic diamines produced during spoilage. A second set of experiments was performed with pork, beef and rabbit samples. The last served as a control, since no record was available for the time elapsed since slaughtering of the animals of the other two species. Analyses were performed to determine total amine nitrogen produced during storage at chill temperatures in wrapped and unwrapped samples, and the amount of Pseudomonas , total aerobic organisms and lactic acid bacteria. Results suggested that the wrapping material did not produce the microaerophilic conditions to promote the growth of required lactic acid bacteria sufficient to outnumber the other microorganisms present. However, diamine production was slower in wrapped than in unwrapped samples.     

Quantitative Crack Surface Morphology of Bone Cements in Relation to Propagation Rate

Morphology of the crack surface of surgical bone cements has seldom been studied in the past despite the clinical relevance of cement failure. Previous studies on a specific cement type suggest that crack morphology depends on crack propagation rate. The objectives of this work were: (i) to develop a quantitative indicator for describing crack morphology; and (ii) to assess if dependency on crack‐propagation rate is affected by cement formulation. Known crack surfaces were obtained from specimens under controlled loading conditions. Crack surface roughness was measured for different crack‐propagation rates, and compared against the amount of cleaved pre‐cured beads (measured with a semi‐automated procedure based on micrographs). Such indicators were extremely robust, operator‐independent, highly correlated, and sensitive to the type of fracture. Moreover, it was found that crack surface morphology heavily depends upon cement composition. Thus, crack surface roughness is proposed as a method for quantitatively identifying crack morphology, and finally classifying fracture type.     

EFFECT OF BEAN (Phaseolus vulgaris) ALBUMINS ON PHASEOLIN IN VITRO DIGESTIBILITY, ROLE OF TRYPSIN INHIBITORS

The in vitro digestibility of albumin proteins from Phaseolus vulgaris was low (26–32%) and when heated (99C/30 min) it was further reduced to 13–18%, independent of the variety. Phaseolin (the main bean globulin) had, after heating, a digestibility similar to casein, but when heated in mixtures containing as low as 10% of the albumin fraction, it suffered a drastic decrease in its susceptibility to proteolysis. The chemical interactions that occur among the components of the albumin fraction that reduce its digestibility do not occur between phaseolin and albumins. Interactions between phaseolin and albumins depend on pH of heating and are responsible for differences in molecular weight distribution of peptides formed by the action of pepsin, but did not alter overall digestibility of the mixture. The low digestibility indeed was due to heat-stable trypsin inhibitors found in the acid-soluble fraction of the albumins. Lectins and α-amylase inhibitors, glycoproteins of the albumin fraction, showed, in similar experiments, no effect on phaseolin digestibility, in spite of being very poorly digested even after heating.