Drying kinetics modeling of hot air drying of emulsion templated oleogels employing hydroxypropyl methylcellulose as structuring agent

Abstract

This work focused on the drying of O/W emulsions employed to obtain templated structured oils with hydroxypropyl methylcellulose (HPMC) as oleogelator. Sunflower oil/water emulsions with different HPMC content (1%–3% w/w) were dried at different air temperatures (from 70 to 100 °C) employing two different initial thicknesses (0.25 and 0.50 cm). Drying kinetics showed the existence of an initial constant drying rate period followed by a falling drying rate period below critical moisture content. This critical content was constant (0.38 kg water/kg dry solid) independently of drying conditions and HPMC content. Drying rate decreased linearly with moisture content during the falling rate periods. A 3-parameter model was proposed to simulate drying kinetics in the range of drying temperature and HPMC content of tested oleogels. Physical properties of fresh and stored (20 days) oleogels such as oil binding capacity, color, and hardness were measured to evaluate drying conditions effect on product quality. Temperatures above 70 °C were necessary to promote the HPMC gelation. Best characteristics of oleogels in terms of texture, color and oil binding capacity were obtained with HPMC content of 2% w/w, 0.25 cm of emulsion thickness and 80 °C of drying temperature. These results are useful for the design of large-scale dryers for this new kind of products.