The effects of ultrasonic/microwave assisted treatment on the water vapor barrier properties of soybean protein isolate-based oleic acid/stearic acid blend edible films

Edible films were prepared using soy protein isolate (4g/100 g), oleic acid (0–2 g/100 g) and stearic acid (0–2 g/100 g). Effects of the ratio of oleic acid to stearic acid and ultrasonic/microwave assisted treatment on the water vapor permeability (WVP) and contact angle of the prepared films were evaluated. Changes in the ratios of oleic acid to stearic acid had significant effects on WVP and contact angle (p < 0.05). It was found that the prepared films (oleic acid:stearic acid = 2:3) had the lowest WVP value (0.1 × 10−12  g cm−1 s−1 Pa−1) and highest contact angle value (135°), when the treatment temperature, time and power were 20 °C, 15 min, and 500 W respectively. Additionally, when OA and SA were added, the peak at 2920 cm−1 appeared, indicating a certain degree of interaction between the lipid and SPI.