Coating a film on the surface of fruits to prolong the shelf life is an often-used method. However, wax coating is not sustainable and environmentally compatible. In this study, soybean protein isolate (SPI) and hydroxypropyl methyl cellulose (HPMC) were dissolved to form a coating solution with glycerin added as a plasticizer. The results showed that the tensile strength (TS) of the films increased from 6.52 to 20.76 MPa and the elongation at break (EAB) decreased from 68.07% to 12.67% when HPMC content increased from 0% to 20%, respectively. The intermolecular forces between the SPI and HPMC molecules made the polymers film-forming and the obtained film more continuous and stronger. The obtained film was tested on grapes and cherry tomatoes, which tightly coated with the film without any cracks. This greatly delayed their deterioration. By comparing the mass loss, total soluble solids, hardness, titratable acids, and pH values, the results showed that the coated grapes and cherry tomatoes exhibited higher freshness than the bare ones. This study fabricated an environmentally friendly coating that could prolong the shelf life of fruits, which will potentially promote the healthy development of the fruit industry.

Promising pH-smart films suffer from problems of complicated production, high cost, high energy consumption, and low light barrier. In this study, poplar veneer was used as an alternative to the film matrix. A strategy was realized wherein bleaching and carboxylation were simultaneously developed to construct a green and smart label via alkaline H 2 O 2 treatment and adsorption of mulberry anthocyanins. When the concentrations of H 2 O 2 and NaOH increased to 6% and 0.1 mol/L, the carboxyl content and anthocyanin adsorption amount of veneer reached 1.04 mmol/g and 4.057 mg/g, respectively. The carboxyl content and adsorption capacity of anthocyanins were positively correlated. ALV showed good pH sensitivity and the ability to fix anthocyanins firmly. The color of ALV changed from purplish red to dark blue when the TVB-N of pork reached 14.78 mg/100 g, which was close to the threshold value of GB 2733-2015. This study provides a new material that can help assess the freshness of food in a safe and green way. It achieves a high-value conversion and the utilization of low-quality wood, opening up a new field of wood utilization.