Effect of OHMIC heating and ultrasound on functional properties of biodegradable gelatin‐based films
Victória Hermes de Vargas, Simone Hickmann Flôres, Giovana Domeneghini Mercali, Lígia Damasceno Ferreira Marczak
Abstract
Abstract This study aimed to evaluate the effect of ohmic heating (OH) and ultrasound (US) on the functional properties of biodegradable gelatin‐based films. For OH, electric field strength (30–120 V) and exposure time (5–20 min) were evaluated; for US, intensity (50%–100%) and the exposure time (5–20 min) were investigated. Regarding OH, higher mechanical properties (tensile strength and Young's modulus) values were obtained at the lowest electric field strength applied, regardless of the exposure time. For US, tensile strength and Young's modulus values significantly increased with increasing the US intensity and exposure time. Films produced with OH and US with optimized properties were compared to a control film (produced by conventional heating). X‐ray diffraction and thermogravimetric analysis indicated that films produced by US and OH showed a more ordered structure, with a higher crystallinity index, and were more thermally stable. The most pronounced effects on mechanical properties were obtained using OH: tensile strength increased from 1.53 MPa (control) to 3.86 MPa. US application reduced film opacity, resulting in a more transparent film with a smoother surface. Both treatments also significantly decreased the water vapor permeability but did not affect film thickness, moisture content, water solubility, and biodegradability.