Effect of endosperm type on texture and in vitro starch digestibility of maize tortillas

Tortilla is the main staple of Mexico and it is made using diverse maize varieties, which have different endosperm types. Three maize varieties with vitreous, intermediate and floury endosperms were used. Texture and starch digestibility were evaluated in freshly prepared and stored tortillas for 24, 48 and 72 h. Tortilla made with maize of vitreous endosperm had the highest force to rupture and the lowest distance of elongation, indicating more rigid texture. Stored tortillas had lower available starch content and higher effect was shown by tortilla of vitreous endosperm, pattern that agrees with the higher increase in the resistant starch content with the storage time. Fresh tortilla of floury endosperm showed the highest hydrolysis rate during the first 15 min followed by tortillas of intermediate and vitreous endosperms. Starch hydrolysis values decreased when storage time increased, in agreement with the resistant starch content in the stored tortillas. At the longest storage time (72 h) tortilla of floury endosperm presented higher hydrolysis rate, followed by tortilla of intermediate and vitreous endosperms. The endosperm type plays an important role in the textural and starch digestibility of fresh and stored tortillas.     

Full in-situ characterization of spatial light modulators in an optical correlator. Filter adaptation to operating curves

Abstract

In this paper we present one method for the characterization of the spatial light modulators (SLMs) of a real-time Vander Lugt type of correlator. This correlator uses two SLMs: one to introduce the scene and a second to introduce the frequency‐matched filter. The SLM characterization methods are in situ, that is in the correlator set‐up. Illumination conditions are different for each SLM, and consequently different characterization techniques must be used in each case. For the characterization of the scene SLM a diffraction method is used, while for the characterization of the filter SLM an interferometric technique is more convenient. Finally, we take into account the operating curves of scene and filter SLMs in the design of the filter in order to optimize the correlation peak.     

A method for efficiently solving the IAST equations with an application to adsorber dynamics

The Ideal Adsorbed Solution Theory (IAST) developed by Myers and Prausnitz and Radke and Prausnitz provides a powerful tool to calculate multicomponent adsorption equilibria based on single component adsorption isotherms. An important aspect of the application of IAST is that it requires the solution of an implicit algebraic system of equations. Analytical solutions can be derived only for few simple single component isotherm models. This work offers a new concept to solve the equations of the IAST for mixtures of N components characterized by nondecreasing single component adsorption isotherm behavior. The approach is based on transforming the algebraic system of IAST equations to a system of ODEs with one specified initial value. This work also provides analytical expressions for the partial derivatives of the predicted adsorption equilibria and increases the efficiency of numerical calculations for fixed‐bed adsorber dynamics. The strength of the solution method is illustrated in case studies. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1263–1277, 2013     

Antihypertensive activity of AMC3, an engineered 11S amaranth globulin expressed in Escherichia coli,in spontaneously hypertensive rats

The acidic-subunit of 11S seed storage globulin of Amaranthus hypochondriacus was recently modified by the incorporation of antihypertensive biopeptides: four units of Val–Tyr dipeptides (VY) in tandem and one of Ile–Pro–Pro tripeptide (IPP), was named AMC3. The in vivo effect of AMC3 enzymatic hydrolysates (AEH) produced in Escherichia coli, was evaluated in spontaneously hypertensive rats (SHR) by once-oral administration experiments. As positive control a SHR group received a dose of captopril (50 mg/kg) (an angiotensin-converting enzyme (ACE) inhibitor used for the treatment of hypertension). Mean arterial pressure (MAP) was measured for 6 h after AEH or captopril administration. AEH administration at maximal dose (100 mg/kg) significantly reduced MAP similar to the group treated with captopril. The maximal reduction in MAP was observed after 3.5 h after AEH oral administration. The present study showed that enzymatic hydrolysates of AMC3 containing ACE inhibitory peptides (4xVY and IPP) sequences had significant antihypertensive action by oral administration in spontaneously hypertensive rats (SHR).     

Characterization of sewage waters by biochemical fingerprinting of Enterococci

Three sewage waters with different sources of faecal pollution (human, pig and mixed origin) were analysed. Enumeration of Enterococci was performed and representative strains for each sample were isolated. Biochemical fingerprints of these strains were obtained by using a simple automated microplate system. The structure and composition of the Enterococci populations were studied and the most representative biochemical profiles were determined by cluster analysis. The diversity index was high for all the sewage waters sampled. The enterococcal populations detected in the three kinds of sewage waters were similar. Although many of the representative strains were found in the three kinds of samples, some strains were detected only in human sewage and others only in pig slurry.     

Inductive measurement of metallic cylindrical shells

The thickness of thin cylindrical copper shells of radiusaand thicknessD(D/a < 0.15)were measured by means of an inductive measurement. The samples were obtained by chemical reduction of thick copper pipes. The conductivity of the cylinders was measured by a standard four-terminal technique. The agreement between the value of thickness measured mechanically and the value obtained from inductive measurement is of the order of ±2 percent. Thicker brass shells were measured and these results compared with theory. The extension of the inductive measurement to cylindrical shells covering cylinders with a finite conductivity is also discussed.     

Erosion of Finite Thickness Sediment Beds by Single and Multiple Circular Jets

Sediment management in reservoirs with the help of water jets has motivated this work. Erosion caused by single and multiple submerged circular turbulent wall jets on a noncohesive sediment bed of finite thickness lying on a fixed boundary was studied with the help of laboratory experiments. Different combinations of jet diameter, jet separation, and sediment thickness to jet diameter ratio were tested. Results show a relation between dimensionless parameters characterizing the steady state bed profile and the densimetric particle Froude number F0 given by the velocity at the nozzle and the effective diameter and submerged specific density of the sediment. Evolution of scour with time confirms previous studies where the erosion was found to initially grow with the logarithm of time up to a certain reference time t*. This time, made dimensionless with a time scale tc involving the volume of sediment scoured and the rate of erosion, was also related to the densimetric Froude number. A comparison with studies regarding erosion of a semiinfinite layer of sediment is also presented.     

Chemical and biochemical changes in prickly pears with different ripening behaviour

Chemical and biochemical changes were studied in ripening prickly pears from three Opuntia morphospecies with different ripening behaviour: Naranjona (O. ficus-indica), Blanca Cristalina (Opuntia sp.), and Charola (O. streptacantha), of early, intermediate, and late ripening, respectively. At fullyripe stage (commercial maturity), Blanca Cristalina showed the biggest fruits, the hardest texture, and its pulp had the highest protein content. There were no significant differences among morphospecies in pH or total soluble solids in fully ripe fruits. The three species exhibited considerable levels of vitamin C, dietary fibre, and minerals such as calcium, iron, and zinc. Protein expression was analysed in pulp and skin from every species at physiological and commercial maturity. Some proteins appeared at both stages, while many others expressed differentially. This study evaluated prickly pear components important for human nutrition and health, and provided basic information on pricky pear ripening, with a view to its control and to improving shelf life.