Air-drying kinetics of functional apple products fortified with calcium.

GONZÁLEZ-FÉSLER, M.; SALVATORI, D.; ALZAMORA, S.M.

Montevideo, Uruguay

Congreso; XIII Seminario Latinoamericano y del Caribe. Ciencia & tecnología de los Alimentos; 2004

Sociedad Uruguaya de Ciencia y Tecnología de Alimentos, Asoc. Latinoamericana y del Caribe de Ciencia y Tecnología de los Alimentos

Different techniques, such as vacuum impregnation (VI), atmospheric impregnation (AI) and a VI-AI combination, have been recently proposed for calcium fortification of fruits. These processes basically consist in immersing the sample in a Ca++ concentrated solution at room temperature under specific conditions of time and pressure, so that the external solution and/or the solute can be introduced into the vegetable matrix. Therefore, important changes in physicochemical and structural properties take place in the fruit, which will affect its behavior during the final preservation stage. An adequate control of blanching pretreatment and impregnation treatments prior to drying processes may be used as a tool to improve mass transfer and to develop functional dehydrated  foods. The objective of this study was to analyze the effect of calcium impregnation treatments (AI, VI or VI-AI), with and without previous blanching, on the air drying kinetics of apple. Apple impregnation was conducted with an isotonic glucose aqueous solution containing 5.24 % (w/w) Ca++ salts. A 50 mmHg vacuum pressure was applied for a time t1 (0,15 min) and then atmospheric pressure was restored and maintained for a time t2 (0, 1.5, 6 h). For blanching process prior to impregnation, samples were immersed in saturated vapor (2 min) and then cooled in water (5min). Drying curves of the impregnated apples were obtained at 60 ºC in conditions of internal control for mass transfer and values of effective water diffusivity (Deff) during the first falling rate period were determined. Blanching increased drying rate of fresh apples, evidently due to the lower resistance to water flux as a consequence of rupture of membranes and swelling of cell walls. For impregnated apples (with and without previous blanching) Deff was found to decrease.