Modelado del transporte de vapor de agua a través de películas comestibles de almidón

BERTUZZI MARÍA A.; VICENTE, MARÍA S.; ARMADA, MARGARITA; GOTTIFREDI, JUAN C.

Valencia

Congreso; III Congreso Iberoamericano de Ingeniería de Alimentos y I Congreso Español de Ingeniería de Alimentos; 2001

IATA, Universidad Politécnica de Valencia

The ASTM E96 cup method used to calculate water vapor permeabilities in edible films involves numerous assumptions. One of them is that water concentration is constant in the film. In addition permeability equations assume that the film solubility and diffusivity coefficients are constant and that negligible resistance to mass transfer exist in the gas phases on both sides of the film. In this paper we show that these assumptions are not true for edible films based on starch (high amylose corn starch). We have determined diffusivity and solubility coefficients separately. These values are used to predict the permeability and the predicted values are compared with the experimental ones. Diffusivity coefficients were determinated by a transient state gravimetric technique in a high vacuum electrobalance (Cahn RG). The obtained values show a great dependence on water concentration. The water vapor absorption isotherms were obtained according to the COST Method for different temperatures and in a wide range of water activities. Isotherm curves went upwards, which means that the solubility coefficients are temperature and concentration dependent. The isotherms were adequately fitted by the Flory-Huggins theory and their parameters were determined. Fick’s first law was solved taking into account the diffusivity and solubility coefficient concentration dependence. The flux values predicted by this way were compared with the experimental ones obtained according to ASTM E96.