| Popis: |
To develop a new type of food packaging film and improve the level of resource utilization of enoki mushroom, polyvinyl alcohol (PVA) was used as the film-forming substrate, and the composite film of PVA-enoki mushroom aqueous extract was prepared by blending with enoki mushroom aqueous extract. The physical properties of the composite film, such as tensile strength, elongation at break, water resistance, thickness, opacity and water vapor transmission rate were taken as parameters to study the effects of PVA addition, 2-acetyltriethyl citrate (ATEC) addition, enoki mushroom aqueous extract addition, drying time and drying temperature on the physical properties of the composite film. Principal component analysis was used to comprehensive evaluation of composite film performance. The multiple regression equation model was established for the preparation of PVA-enoki mushroom aqueous extract composite film by response surface analysis, and the conditions for the preparation of the composite film were optimized. The effects of composite film on freshness indexes such as browning degree, weight loss, vitamin C and malondialdehyde of strawberries during storage (6 d) at 20 ℃ were also investigated. The results showed that 4.0 g of PVA, 4.0 g of ATEC, 3.9 g of aqueous extract of enoki mushroom, 62 ℃ drying temperature and 3.5 h drying time were the optimal conditions for composite film preparation. The tensile strength of the composite film was 31.76±0.50 N/cm2, elongation at break was 97.99%±0.25%, water vapor transmission rate was 1.44×10−9±1.53×10−11 g·mm/m2·h·kPa, water resistance was 549.14±0.94 s/mm, film thickness was 0.062±0.002 mm, opacity was 20.97±0.39, and a combined physical property score of 102.25±0.16, with a relative error of 0.57% from the model prediction. Infrared spectroscopy, scanning electron microscopy and X-ray diffraction analyses showed that the composite film was structurally intact, and the aqueous extract of enoki mushroom was compatible with the matrix and bound by hydrogen bonding. According to the indicators including the browning degree, weight loss, vitamin C, and malondialdehyde, the prepared composite film showed a better preservation effect during strawberry storage. |
