Response surface method applied to optimization of estradiol permeation in chitosan membranes

The present work deals with the study of estradiol permeation in chitosan membranes. A fractional factorial design was built for the determination of the main factors affecting estradiol permeation. The independent factors analysed were: concentration of chitosan, concentration of cross-linking agent, cross-linking time and thermal treatment. It was found that concentration of chitosan and cross-linking time significantly affected the response. The effects of thermal treatment and concentration of cross-linking agent were not significant. An optimization process based on response surface methodology was carried out in order to develop a statistical model which describes the relationship between active independent variables and estradiol flux. This model can be used to find out a combination of factor levels during response optimization. Possible options for response optimization are to maximize, minimize or move towards a target value.     

OPTIMIZATION OF MANUFACTURE OF ALMOND PASTE COOKIES USING RESPONSE SURFACE METHODOLOGY

The response surface methodology (RSM) was used in the optimization of a modified recipe of almond paste cookies to pinpoint the best combination of the most important factors, in order to obtain an enhanced product with quality characteristics similar to the typical one. In this modified recipe, bamboo fiber and fructose were added as humectant and anticrystallizing agents to extend the shelf life of the cookies. Five quantitative controllable factors were selected for the experimental design: weight of bamboo fiber, fructose/saccharose ratio (F/S) and weight of egg white as ingredients, and baking time and temperature as process parameters. To assess the product quality, texture, moisture content and color were considered as dependent variables. The three second-order polynomial models obtained by RSM and the subsequent optimization step indicated that a formulation with 28.95 g of fiber, 252.5 g of egg white, an F/S equal to 0.1, baking time and temperature of 21.5 min and 185.5C, respectively, represents the best recipe to manufacture a new product with quality attributes very similar to the typical one and, in addition, with an extended shelf life.

PRACTICAL APPLICATIONS

The importance of this work arises from the possibility to obtain new formulations by the enhancement of original recipes of products with a very limited shelf life using a statistical and designed approach. The achieved results led to a higher quality of these products over time, without changing the most important characteristics related to consumer acceptance.     

The transmission zeros of systems with delays†

In this paper we study the properties of the zeros of a system with general delays in the input, state and control variables. The main result of this paper shows that the zeros of the transfer function are always zeros of the system matrix, with of at least the same multiplicity moreover, when the system is canonical, the zeros of the system matrix are zeros of the transfer function, with the same multiplicity.