Papers by Vrani Ibarra-Junquera
Food Chemistry, 2010
Raw and cooked (boiled and grilled) Poblano, Bell, Chilaca, Caribe, Jalapeño, Serrano, Habanero, ... more Raw and cooked (boiled and grilled) Poblano, Bell, Chilaca, Caribe, Jalapeño, Serrano, Habanero, and Manzano peppers were evaluated for tristimulus colour, capsaicinoids (capsaicin, dihydrocapsaicin, nordihydrocapscapsaicin), and total phenolic contents. Boiling (96°C) and grilling (210°C) was performed under household conditions according to typical procedures of the Mexican cuisine. Contents of capsaicin (0.6-913.8 lg/g), dihydrocapsaicin (0-756.9 lg/g), nordihydrocapsaicin (0-68.2 lg/g), and total phenolics (1150.5-2190.0 lg of gallic acid equivalents/g) in raw peppers varied widely between types of peppers. Moderate losses (1.1-28.1%) in capsaicinoids were induced by boiling while grilling caused a significant increase (2.6-924.9%) in the content of these compounds. Proportion of individual capsaicinoids was similar in raw and cooked peppers. Boiling and grilling sequentially increased (7.4-137.0%) the total phenolic content in pungent peppers. Total phenolic content in non-pungent Bell peppers was reduced by cooking (1.6-26.9%). Boiling induced smaller changes in colour values (L*, a*, and b*) compared to grilling. The results demonstrated that Mexican raw peppers are rich in capsaicinoids and phenolic compounds. Household cooking can cause either decreases or increases in the content of such compounds in peppers.
Korean Journal of Chemical Engineering, 2008
The classical dynamical systems model of continuous stirred tank reactors (CSTR) in which a first... more The classical dynamical systems model of continuous stirred tank reactors (CSTR) in which a first order chemical reaction takes place is reformulated in terms of the stochastic cellular automata procedure developed in the works of Seyborg [2] and Neuforth [3], which is extended by including the feed flow of chemical reactants. We show that this cellular automata model is able to simulate the dilution rate and the mixing process in the CSTR, as well as the details of the heat removal due to the jacket. The cellular automata approach is expected to be of considerable applicability at any industrial scale and especially for any type of microchemical system.
The population dynamics of mixed-culture and sequential-cultures in fruit-must fermentation is a ... more The population dynamics of mixed-culture and sequential-cultures in fruit-must fermentation is a very interesting problem from both the theoretical and technological stand point. By mixed-culture we refer to those fermentations in which more that one strain/species are present from the beginning of the process; and by sequential to those in which different microorganisms are added along the process. These kinds of fermentations play a key role in industry of fermented beverages. The mathematical models of such processes should represent the dynamics of multiple species growing in a mixture of substrates as the fruit must composition includes an important proportion of hexoses and pentoses. Since the flavor is a basic aspect of beverages, and in general of all fermented foods, it is fundamental to study the population dynamics and its impact in the organoleptic properties, through the influence in the volatile compound profile. The goal of this paper is to present a panorama of the investigations of these fermentative ecosystems from a biological, mathematical, and technological stand point.
Computers & Chemical Engineering, 2007
It is shown that periodic orbits can emerge in Cholette's bioreactor model working under the infl... more It is shown that periodic orbits can emerge in Cholette's bioreactor model working under the influence of a PI-controller. We find a diffeomorphic coordinate transformation that turns this controlled enzymatic reaction system into a generalized Liénard form. Furthermore, we give sufficient conditions for the existence and uniqueness of limit cycles in the new coordinates. We also perform numerical simulations illustrating the possibility of the existence of a local center (period annulus). A result with possible practical applications is that the oscillation frequency is a function of the integral control gain parameter.
The population dynamics of mixed-culture and sequential-cultures in fruit-must fermentation is a ... more The population dynamics of mixed-culture and sequential-cultures in fruit-must fermentation is a very interesting problem from both the theoretical and technological stand point. By mixed-culture we refer to those fermentations in which more that one strain/species are present from the beginning of the process; and by sequential to those in which different microorganisms are added along the process. These kinds
Bioprocess and Biosystems Engineering, 2009
We describe an algorithm for the continuous monitoring of the biomass and ethanol concentrations ... more We describe an algorithm for the continuous monitoring of the biomass and ethanol concentrations as well as the growth rate in the Mezcal fermentation process. The algorithm performs its task having available only the online measurements of the redox potential. The procedure combines an artificial neural network (ANN) that relates the redox potential to the ethanol and biomass concentrations with a nonlinear observer-based algorithm that uses the ANN biomass estimations to infer the growth rate of this fermentation process. The results show that the redox potential is a valuable indicator of the metabolic activity of the microorganisms during Mezcal fermentation. In addition, the estimated growth rate can be considered as a direct evidence of the presence of mixed culture growth in the process. Usually, mixtures of microorganisms could be intuitively clear in this kind of processes; however, the total biomass data do not provide definite evidence by themselves. In this paper, the detailed design of the software sensor as well as its experimental application is presented at the laboratory level.
Food Science and Biotechnology, 2010
In this study, 2 Trichoderma strains (T-I and T-II) were evaluated for the production, by submerg... more In this study, 2 Trichoderma strains (T-I and T-II) were evaluated for the production, by submerged (SmF) and solid state fermentation (SSF) of an enzymatic complex with the capacity to degrade the cell components of mango peels, using these as support (in SSF) and source of nutrients. Highest enzymatic activity (7,552.5 units of endo-glucanase/L) was found in T-II by SSF. Efficiency of this crude enzymatic extract in the extraction of mango juice was evaluated, improving the yield up to 79%, representing an alternative to give an added value of mango peels improving the yields of production of mango juice.
This work presents a rapid and simple freeze centrifugation method to concentrate dilute protein ... more This work presents a rapid and simple freeze centrifugation method to concentrate dilute protein solutions for detection by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) Coomassie blue staining. Moreover, a simple way to assemble a cryoconcentration device is presented, and its use is discussed. Commercial purified protein standard and an enzyme with high fructosyltransferase (FTase) activity, coming from target fractions obtained by chromatographic separation, were used as an example. FTase, coming directly from the chromatographic fractions, was difficult to view through SDS-PAGE analysis; however, it was easily visualized, and its activity was enhanced, after the application of the freeze centrifugation protocol presented here.
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Papers by Vrani Ibarra-Junquera