J.J. Chanona-Pérez

Shrinkage and Deformation of Agave atrovirens Karw Tissue during Convective Drying: Influence of Structural Arrangements

The influence of structural arrangements of Agave discs cut transversally (ADCT) and longitudinally (ADCL) on moisture loss, shrinkage, and shape was evaluated during convective drying by physical and image parameters. ADCT showed lower drying and shrinkage rates than ADCL. The fractal exponent (d) relating volume and thickness of samples rose from 1.552 ± 0.126 to 2.394 ± 0.128 and from 1.662 ± 0.111 to 1.848 ± 0.070 for ADCT and ADCL, respectively, which indicates that shrinkage was nonisotropic for both cases. Parameters considered for evaluating the changes of size and shape of Agave discs at macro- and microscopic levels during drying were projected area (PA), major length (ML), shape factor (SF), and fractal dimension of contour (FDC). The values obtained for these parameters demonstrated that changes in shrinkage and shape of both samples were dependent on structural arrangements of the samples. During the drying of ADCT samples, which have short and rigid structures, pronounced creasing was observed compared to ADCL materials, which are mainly formed by long and rigid structures. Also, it was observed that orientation of fibers influenced shrinkage and deformation.

Effect of the Addition of Mixtures of Glucose Oxidase, Peroxidase and Xylanase on Rheological and Breadmaking Properties of Wheat Flour

Addition of glucose oxidase (GOX), peroxidase (POX), and xylanase (XYL) on dough rheological parameters, and bread quality was studied. When these enzymes were used as a blend, it showed a different effect compared to when added alone. Addition of peroxidase or xylanase increased water absorption, while incorporation of GOX did not affect it. Water absorption decreased in flour added with a blend of the three enzymes. High concentrations of GOX or XYL decreased stability, while presence of POX had minimum effect on this parameter. None of the enzymes, neither alone or blended, improved bread volume. Crumb characteristics were only improved by XYL.

Ultrasound-assisted extraction of starch from frozen jicama (P. erosus) roots: Effect on yield, structural characteristics and thermal properties

ABSTRACT Jicama roots have been studied as an alternative starch source. However, reports about the extraction yield are scarce, as well as publications about the use of pretreatment techniques for this material. Hence, the aim of this study was to analyze the effect of sonication on the starch yield as well as on the granule structure. Ultrasound was observed to have a positive effect on the starch yield, with the largest value obtained at a sonication time of 10 min (24.76 ± 2.4%). This represents a 46.9% increase over a non-treated sample (16.86 ± 0.9%), and the starch granule structure was unaffected, as confirmed by microscopy and an X-ray diffraction analysis The imperviousness of the starch granule to the sonication process is attributed to the protective effect of soluble fiber and a change in viscosity caused by the material released from parenchyma cells. More studies are required in this area.

Structural, mechanical and enzymatic study of pectin and cellulose during mango ripening

Mango is an important crop worldwide, with a postharvest loss that is huge due to its climacteric behaviour. This study evaluated the softening of Tommy Atkins mangos during the ripening process. Ripening index (RPI) shown a decrease from 9.18 ± 0.14 to 4.75 ± 0.47. The enzymatic activity agreed with physicochemical parameters and with the structural and mechanical changes. Three pectin fractions were isolated from the mango cell wall: water soluble (WSP), chelator soluble (CSP) and diluted alkali soluble (DASP) pectin. The Younǵs modulus (E) of the primary cell wall was evaluated, it decreased from 1.69 ± 1.02 to 0.39 ± 0.16 MPa, which could be attributed to the softening of the fruit. A linear fit correlation between E and RPI was found. X-ray and confocal laser scanning microscopy analysis showed the changes occurred in the mango cell wall structure during maturation. Novelties of current study can be helpful in the use of mango wastes to obtain cellulose.

Tools for the Study of Nanostructures

In this chapter, some of the most used microscopy techniques for analyzing the structure of biological materials at the micro- and nanoscale will be presented. These techniques are usually applied looking for the changes that promote the arise of new properties and phenomena that emerge at these scales, hence, the purpose of this chapter is to provide the reader with examples of the application of different types of microscopy techniques usually used to characterize food items.

Effective Drying Zones and Nonlinear Dynamics in a Laboratory Spray Dryer

Spray drying is a widely used unit operation. However, there is not enough information regarding the design of spray dryer equipment. The aim of this research was the identification of spray drying zones using the concept of heat transfer units and to link this approach with results from CFD simulation in steady and nonsteady-state conditions. Experiments were carried out in a two-fluid nozzle laboratory co-current spray dryer. Three zones inside the chamber were found: first and second drying stage zones and a particle expansion stage. The earlier findings showed the highest transfer coefficients, which may suggest the presence of a highly turbulent flow. CFD analysis was performed to assess air and air-particle hydrodynamics, including nonlinear analysis and the effect of particles on the effective drying zones. Good agreement between assessed turbulence and transfer units was found. Drying zones had a high degree of air-particle recirculation, which could be characterized through nonlinear dynamics by evaluating Lyapunov coefficients and by the presence of attractors (related to fractal dimension of texture of reflected laser beam cropped images). While the transfer units approach is useful for construction of lumped models, CFD and experiments based on air-particle nonlinear trajectories give insight on understanding the turbulence that takes place inside the dryer. Both approaches may be useful and could complement each other for design purposes.