Susana E. Zorrilla

A model for using the diffusion cell in the determination of multicomponent diffusion coefficients in gels or foods

Abstract A model for a multicomponent system using the cell for determining apparent diffusion coefficients in gels and foods was developed. In this case, the generalized Ficks law form was used as a constitutive equation for the diffusive molar flux of solutes. Using the method of eigenvectors and eigenvalues, the mass transfer equations were rearranged to simplify the mathematical treatment. Simple expressions for determining the diffusion coefficients of two or more solutes which diffuse in a rigid medium were obtained. In this case, experiments to study the diffusion of NaCl and KCl in cheese were shown and the corresponding effective diffusion coefficients were obtained.

Calcium Uptake during Immersion of Strawberries in CaCl2 Solutions

The present study studied calcium uptake in strawberries during immersion in CaCl(2) solutions by analyzing total calcium and cell-wall calcium contents and the relationships between cell-wall calcium content, pectin content, and the degree of pectin esterification, considering different temperatures and concentrations of the immersion solution. In addition, calcium uptake at different zones of the strawberries was studied. Calcium uptake increased significantly when the concentration of the immersion solution increased from 1% to 10% (v/v), and calcium uptake was higher at 38 degrees C at some immersion times, but there were no significant differences between 1 and 24 degrees C. Most of the calcium incorporated by the strawberries was retained in the alcohol insoluble solids and it may be related to calcium bounded to the cell wall. Calcium content did not change during immersion in CaCl(2) solution in the internal or in the central zones; however, it increased significantly in the external zone.

Natural astaxanthin encapsulation: Use of response surface methodology for the design of alginate beads

Nowadays, consumers are more conscious about healthier products consumption benefits. Astaxanthin obtained from the microalgae Haematococcus pluvialis represents a natural ingredient for the nutraceutical and functional food industries. It is claimed that astaxanthin has much stronger antioxidant activity than vitamin E and β-carotene, providing different health benefits. However, the unstable structure of the molecule limits its application in functional foods development. Therefore, the present study evaluates the effect of five independent formulation and process variables for natural astaxanthin oleoresin encapsulation using an external ionic gelation technique. Response surface methodology can be used for studying the effect of several factors at different levels and their influences on each other, which overcomes the shortcoming of the traditional orthogonal method. The results showed that alginate and CaCl2 concentrations have a significant effect on particles size obtained, while alginate/oleoresin ratio and surfactant concentration greatly influence the astaxanthin oleoresin release rate. In vitro studies under simulated intestinal conditions showed that astaxanthin oleoresin release process can be described by Hopfenberg model. Three mathematical models were obtained for predicting particle size, astaxanthin release rate and encapsulation yield under different process conditions, providing a platform for microencapsulation technology optimization for healthy food design.