Drying kinetics of gluten-free pasta according to temperature and relative humidity

V. LARROSA; G. LORENZO; N. ZARITZKY; A. CALIFANO

Montevideo

Congreso; "X Congreso Iberoamericano de Ingeniería de Alimentos"; 2015

Laboratorio Tecnológico de Uruguay (LATU)

Pasta drying involves a biphasic system: pasta dough and drying air. Drying rates depend on equipment characteristics (temperature, relative humidity (RH), air flow), and pasta properties (moisture, volume/surface relationship, formulation). Particularly, gluten-free (GF) dried pasta, which lacks a gluten network, might become fragile and disintegrate during cooking if the air conditions are inadequate. The aim of this work was to study the effect of operating variables (temperature and RH of the air) on the drying rate of gluten-free pasta by mathematically modeling the drying process. Pasta dough contained 51.4% corn starch and corn flour, 6.6% dry-egg proteins, 2.5% mixture of xanthan and locust bean gums, 35.8% water, 2.6% sunflower oil, and 1.1% NaCl. GF noodles geometry was 200x8x2 mm. Experimental runs were done in a forced convection cabinet dryer, with independent air temperature and humidity controls, and a continuous weight data acquisition system. Four combinations of temperature (30?50ºC) and RH (40-80%) were used, maintaining a constant air velocity (0.5 m/s). The drying process was modeled using heat and mass coupled balances, considering bidirectional transport. A diffusional model for water transfer through pasta was assumed and heat transport was based on a conductive model. Pasta properties and transport coefficients were determined using pasta composition and processing conditions. Experimental water losses were modeled using finite element methodology to solve the partial differential equations. The model fitting to experimental data was good and validation with independent data was also satisfactory. The average water diffusional coefficient was de 3.5x10-11 m2/s, similar to those reported for wheat pasta. Inclusion of heat transport contribution in the model was correct since temperature in the center of the solid reached an asymptotic value after at least 30 min. Gluten-free noodles drying process was 50% faster than drying traditional wheat pasta under the same operating conditions.