Effect of drying temperature and pH alteration on mechanical and water barrier properties of transglutaminase cross linked zein-oleic acid composite films

- Mechanical and water barrier properties improved at low pH of 5 and 6.
- Temperatures 30 °C and 35° C improved tensile strength.
- Elongation at break improved at low drying temperatures.
- Increased oleic acid concentration reduced tensile strength.

Mechanical and water barrier properties of zein-oleic acid composite films were evaluated at four pH values (5, 6, 7, 8) and four drying temperature values (20 °C and 45% RH, 25 °C, 30 °C, 35 °C). Mechanical and water barrier properties of the films were significantly affected by both pH and drying temperature. Low pH (5 and 6) accompanied by high drying temperature (30 °C and 35 °C) improved tensile strength, solubility and water vapour permeability while high pHs (7 and 8) accompanied by low drying temperature (20 °C and 45% RH, 25 °C) improved elongation at break but did not improve tensile strength, solubility and water vapour permeability. The highest values obtained for different properties and conditions were as follows: Tensile strength (30.7 MPa, pH 6, 35 °C, 1% oleic acid), water vapour permeability (0.51 g mm m−2 h−1 kPa−1, pH 5, 35 °C, 4% oleic acid) and solubility (1.7%, pH 6, 35 °C, 4% oleic acid). The lowest values were as follows: Tensile strength (3.3 MPa, pH 7, 20 °C/45% relative humidity, 4% oleic acid), water vapour permeability (1.59 g mm m−2 h−1 kPa−1, pH 8, 20 °C/45% relative humidity, 4% oleic acid) and solubility (7.73%, pH 8, 20 °C/45% relative humidity, 1% oleic acid).