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Ovando-Chacon G.E.,Instituto Tecnologico De Veracruz | Ovando-Chacon S.L.,Instituto Tecnológico de Tuxtla Gutierrez | Prince-Avelino J.C.,Instituto Tecnologico De Veracruz
International Journal of Heat and Mass Transfer | Year: 2012

Entropy generation due to steady state heat transfer and the motion of the vertical boundaries in a two-dimensional square cavity is numerically studied, using the value of the velocity and temperature obtained by solving the Navier-Stokes equation coupled with the energy equation with the finite element method and an operator splitting scheme. Increasing the Richardson number, the entropy generation by fluid friction is intensified inside the cavity due to the vortex formation at the central part of the cavity. The entropy generation by heat transfer becomes more intense at the vertical walls and the central low part of the cavity due to the stronger temperature gradients at this region. © 2011 Elsevier Ltd. All rights reserved.


Mani-Lopez E.,Instituto Tecnologico De Veracruz | Garcia H.S.,Instituto Tecnologico De Veracruz | Lopez-Malo A.,Universidad de Las Americas Puebla
Food Research International | Year: 2012

Salmonella, a food-borne pathogen, has a recurrent incidence in meat and poultry products. Currently, cases of salmonellosis represent very important economic losses in many countries. An alternative for the prevention of Salmonella outbreaks due to consumption of meat and poultry products, are organic acids (acetic, citric, lactic, malic, propionic, and tartaric among others). Organic acids have been utilized for many years for decontamination of beef, pork and poultry products from several bacteria including Salmonella. Current reports describe new treatments with organic acids using the hurdle technology approach to inhibit Salmonella. Also, preventive actions should be taken in order to decrease the appearance of resistant strains of Salmonella as a result of insufficient or sub-lethal treatments with organic acids in meat and poultry products. This review presents general insights on the use of the organic acids to control Salmonella in meat and poultry products. Also, information of the action mechanism, types and doses of treatments, as well as how resistance can occur from improper application of organic acids. © 2011 Elsevier Ltd.


Rascon M.P.,Instituto Tecnologico De Veracruz | Beristain C.I.,University of Veracruz | Garcia H.S.,Instituto Tecnologico De Veracruz | Salgado M.A.,Instituto Tecnologico De Veracruz
LWT - Food Science and Technology | Year: 2011

The performance of gum arabic (GA) and soy protein isolate (SPI) on paprika oleoresin microcapsules preparation and their storage were evaluated. Paprika oleoresin emulsions with a ratio of paprika oleoresin/wall material of 1:4 (w/w) were prepared using high-pressure homogenization, and then spray dried. Both treatments showed that carotenoid retention in the microcapsules increased as inlet air temperature was increased from 160 to 200 °C, and the yellow fraction was more stable than the red fraction at all temperatures tested. Microcapsules with the highest carotenoid retention were stored at different aw's at 35 °C. Maximal stability for carotenoid oxidation was found at aw's of 0.274 and 0.710 for microcapsules prepared with GA and SPI respectively. In both treatments the lowest carotenoid degradation was associated to the minimum integral entropy zone and affected in the same way to the red and yellow pigments, during storage at 35 °C. Additionally, in contrast to microcapsules prepared with SPI, GA microcapsules were unable to retain their structural integrity at water activities above 0.743. © 2010 Elsevier Ltd.


Prince J.C.,Instituto Tecnologico De Veracruz | Williams F.A.,University of California at San Diego | Ovando G.E.,Instituto Tecnologico De Veracruz
Fuel | Year: 2015

The low-temperature ignition of mixtures of n-heptane and air at elevated pressures (13-40 bar) is addressed. A base mechanism of 272 elementary reactions among 45 species, which models the ignition time of this fuel under a wide range of conditions for initial temperatures above about 1000 K is revised and augmented to produce the two-stage ignition and negative-temperature-coefficient (NTC) behavior seen experimentally for this fuel below 1000 K. By using available kinetic data, it is shown that by adding only 4 additional species to the original chemical mechanism, removing 8 of the original steps and replacing them by 14 new steps, the low-temperature ignition phenomena are modeled well. The numerical ignition-time predictions of this mechanism are compared with results of experimental shock-tube measurements in which NTC behavior and two-stage ignition are observed, showing reasonably good agreement. These results thus extend the range of applicability of the original mechanism to lower temperatures that are of interest in various applications, such as those for HCCI engines. ©2014 Elsevier Ltd. All rights reserved.


Garcia-Alvarado M.A.,Instituto Tecnologico De Veracruz | Ruiz-Lopez I.I.,Autonomous University of Puebla
Chemical Engineering Science | Year: 2010

In this paper a design method was formulated to deal with robustness and performance specifications for any MIMO linear controller. The controller tuning procedure was expressed as an optimization problem in which novel time-domain integrals of the weighted squared error and weighted squared control signals, with initial state zero and inputs not necessarily defined over the Lebesgue normed space (L2 +), were minimized. The control robustness is achieved by constraining the minimization such that the maximum complex/real ratio of the closed-loop control system eigenvalues was lower than one. The proposed tuning method was applied in the design of linear controllers with PID structure for a CSTR with disturbance noise and a nonlinear CSTR with control signal saturations, both reported in literature. The results show that the proposed control systems surpass the performance and robustness characteristics of the controllers designed with other reported methods. © 2010 Elsevier Ltd. All rights reserved.


Prince J.C.,Instituto Tecnologico De Veracruz | Williams F.A.,University of California at San Diego
Combustion and Flame | Year: 2012

The low-temperature (500-1000. K) ignition of propane-air and ethane-air mixtures is studied in this work. An original detailed mechanism of 235 elementary reactions among 40 species, which models the ignition time of these fuels under a wide range of conditions for initial temperatures above about 1000. K, the so-called San Diego Mech, is revised and augmented to produce the two-stage ignition and negative-temperature-coefficient (NTC) behavior seen experimentally for these fuels below 1000. K. By using available kinetic data and introducing applicable steady-state approximations, it is shown that adding only four more reactions for each fuel to the original chemical mechanism succeeds in modeling the low-temperature regime. The predictions of this mechanism are compared with two types of experimental measurements, namely those from rapid-compression machines and those from static-reactor vessels, where NTC behavior and two-stage ignition are observed. The numerical results for the ignition delay exhibit reasonably good agreement with the experimental data from the rapid-compression machine, both qualitatively and quantitatively, as do the predictions for the static reactor, when radical loss by surface reactions is taken into account in an approximate manner. These results thus extend the range of applicability of the mechanism to lower temperatures that are of interest in various applications, such as HCCI engines. © 2012 The Combustion Institute.


Corzo C.A.,Juarez Autonomous University of Tabasco | Waliszewski K.N.,Instituto Tecnologico De Veracruz | Welti-Chanes J.,Monterrey Institute of Technology
Food Chemistry | Year: 2012

Optimal pH and temperature conditions for proteolytic activity of pineapple fruit bromelain were determined using five different substrates: azocasein and azoalbumin (pH 3-10 at 20-70°C), casein and sodium caseinate (pH 2-10 at 20-70°C), and haemoglobin (pH 2-6.5 at 30-60°C). Fruit bromelain has shown optimum activity at pH 7.5 for azoalbumin and at 6.5 for azocasein, all at 55°C. Fruit bromelain activity determined with casein and sodium caseinate has shown optimum activity at 59°C, while the optimum pH was 7.7 for casein and 6.5 for sodium caseinate. Optimum hydrolysis conditions of fruit bromelain towards haemoglobin showed a sharp peak at an acidic pH 2.9 at 37°C. The lowest results of K m and the highest results of V max/ K m were found for azocasein and azoalbumin. These substrates are highly recommended for fruit bromelain activity determination. © 2012 Elsevier Ltd. All rights reserved.


Martinez-Gonzalez R.,Instituto Tecnologico De Veracruz
2016 IEEE International Engineering Summit, IE-Summit 2016 | Year: 2016

For the current manuscript, an automatic gain control circuit is proposed; it is designed in current-mode. Additionally, it has a digitally controlled feedback. The design follows a bottom-up designing philosophy; then, the first step is to simulate the mathematical behavior of the proposal. Matlab is the mathematical tool used for mathematical validation. After corroborating its behavior, the circuit is designed using basic cells in SPICE; some of the cells are specially designed for this application. Finally, the main objective was achieved since a circuit able to adapt the gain factor is obtained. © 2016 IEEE.


Hernandez-Campos F.J.,Zacatepec Institute of Technology | Brito-De La Fuente E.,Fresenius Kabi Deutschland GmbH | Torrestiana-SANCHEZ B.,Instituto Tecnologico De Veracruz
Journal of Agricultural and Food Chemistry | Year: 2010

Immunoglobulin Y (IgY) was purified from hen egg yolk water-soluble protein fraction by ultrafiltration-diafiltration with different membranes. The effect of changing solution properties (pH and Ionic strength) on purification factor (P), process selectivity (ψ), and IgY recovery (RIgy) was studied. Salt presence (150 and 1500 mM) decreased the selectivity and purity factor. This effect was more evident at pH values closer to or higher than the IgY's isoelectric point. The best results were obtained in the absence of salt at pH values of 5.7 and 6.7 using poliethersulfone (PES) and modified PES (MPES), respectively. Process selectivity was doubled, and IgY's purification factors were increased in more than 1 order of magnitude when diafiltration was used. Results from this work show the potential of membrane technology for the purification of IgY from hen's egg yolk. © 2009 American Chemical Society.


Lopez-Martinez L.X.,Instituto Tecnologico De Veracruz | Parkin K.L.,University of Wisconsin - Madison | Garcia H.S.,Instituto Tecnologico De Veracruz
Plant Foods for Human Nutrition | Year: 2011

White, blue, red and purple corns (Zea mays L.) were lime-cooked to obtain masa for tortillas. The total phenolics and anthocyanins content, antioxidant activity expressed as total reducing power (TRP), peroxyl radical bleaching (PRAC), total antioxidant activity (TAA) and quinone reductase (QR) induction in the murine hepatoma (Hepa 1 c1c7 cell line) as a biological marker for phase II detoxification enzymes were investigated. Among the extracts prepared from raw corn varieties the highest concentration of total phenolics, anthocyanins, antioxidant index and induction of QR-inducing activity were found in the Veracruz 42 (Ver 42) genotype. The nixtamalization process (masa) reduced total phenolics, anthocyanins and antioxidant activities and the ability for QR induction when was compared to raw grain. Processing masa into tortillas also negatively affected total phenolics, anthocyanin concentration, antioxidant activities, and QR induction in the colored corn varieties. The blue variety and its corresponding masa and tortillas did not induce QR. Ver 42 genotype and their products (masa and tortilla) showed the greatest antioxidant activity and capacity to induce QR © 2011 Springer Science+Business Media, LLC.

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