Abstract:To enhance the Maillard reaction during the film formation process and improve their functional properties, whey protein isolate (WPI), sodium caseinate (NaCas), and pullulan polysaccharide (PUL) were used as film-forming substrates. Under alkaline conditions with a pH value of 7.0~12.0, wet heating (90 ℃) was used to synergistically trigger the Maillard reaction. The degree of carbonyl-ammonia reaction was determined by parameters such as changes in the content of free amino acids and reducing sugars in the film-forming solution and degree of browning. The structural changes, barrier properties, thermal stability and antioxidant activity of the modified films were investigated. These films were also applied to the packaging and storage of coconut oil. The results show that alkaline conditions significantly accelerate and enhance the Maillard reaction of the thermotropic film-forming solution and improve the functional properties of films. Furthermore, the performance and properties of films significantly improved at pH value 11.0. Oxygen transmittance, water vapor transmittance, and tensile strength reached 0.045 cm3/(m2•d), 5.680×10-12 g•cm/(cm2•s•Pa), and 3.61 MPa high barrier and high strength, respectively; DPPH radical scavenging ability and reducing power reached 95.07% and 1.83, respectively, achieving outstanding antioxidant activities. In the accelerated storage experiment at 50 ℃, the acid and peroxide values of coconut oil were 0.27 mg/g and 0.12 g/100 g, respectively, after 20 days. The films significantly inhibited the oxidative rancidity of coconut oil and extended its shelf life. The results provide new applications of Maillard reaction modified films to prolong the shelf life of oils and fats.
