Process optimization of whey protein concentrate-chitosan edible films modified by ultrasonic/microwave assisting treatment

Abstract: To preparing a new high-performance edible film, the edible films were made from whey protein concentrate (WPC) and chitosan (CS). The modified treatment with assistance of ultrasonic/microwave group was carried out. According to pre-test, the optimal ultrasonic power 90 W, microwave power 300 W, modified temperature 30℃, the edible films were prepared using WPC: CS=6:6, namely, whey protein concentrate 1.5 g and chitosan (CS) 1.5 g, sorbitol concentration 3 g, pH value 5. The results showed that water vapor permeability (WVP) of the edible films modified with assistance of ultrasonic/microwave was 1.18×10-13 g/(cm·s·Pa), lower than that of the control group (1.64×10-13 g/(cm·s·Pa)), in other words, water vapor permeability modified with assistance of ultrasonic/microwave group, was reduced by 27.9%, by contrast with ultrasound and microwave group water vapor permeability was reduced by 13.4% and 8.9%, respectively; oxygen permeability (OP) of the edible films modified with assistance of ultrasonic/microwave was 1.09×10-5 cm3/(m2·d·Pa), which was lower than 2.1×10-5 cm3/(m2·d·Pa) of the control group, namely, oxygen permeability was reduced by 48.1%, by contrast with ultrasound and microwave group oxygen permeability was reduced by 27.3% and 25.9%, respectively. The results showed that ultrasonic/microwave assisting treatment can reduce water vapor permeability and oxygen permeability of blend films of whey protein concentrate and chitosan.The paper analyzed the effects of factors on the tensile strength, elongation at break, transmittance, water vapor permeability and oxygen permeability by single factor experiments. Those factors included film-forming ratio WPC:CS, adding quantity of sorbitol (as plasticizer), the pH, and the time of ultrasonic/microwave assisting treatment. The optimal technology parameters were WPC:CS=5.8:6.2, sorbitol concentration 0.021 g/mL, pH value 5.13, and ultrasonic/microwave assisting treatment time 5 min; and under the conditions, the blend films exhibited good physical properties, and transmittance was 60.23%, WVP was 1.22×10-13 g/(cm·s·Pa), OP was 1.29×10-5 cm3/(m2·d·Pa), tensile strength was 20.53 MPa and elongation at break was 58.91%. According to the optimization results, WPC/CS edible films were prepared and performance test was executed. The measured average values from three parallel verification experiments were: Tensile strength (TS) 23.45 MPa, water vapor permeability 1.34×10-13 g/(cm·s·Pa), elongation at break 57.6%, oxygen permeability 1.15×10-5 cm3/(m2·d·Pa) and transmittance 61.5%. The relative error of transmittance was minimum which was only 2.07%, and the relative error of water vapor permeability was maximum which was 5.65%. It was found that the relative error experiment results can be used to predict. The results can provide a reference for the development of a new edible film.