Cellulose acetate-based SO2-releasing sheets: Preparation and characterization

The present study aimed to produce sulfur dioxide release sheets based on cellulose acetate (CA) film for using in control of mold growth during fruits storage. For this purpose, first CA film was prepared, and the sodium metabisulfite (MBS) salt was fixed on its surface. Further, the effect of temperature (5, 15 and 25 °C), relative humidity (75, 85 and 95%), and the concentration of MBS (30, 40 and 50% by weight) on the release rate of sulfur dioxide was evaluated after 0.5, 2, 4, 6, 16, and 24 h. The results revealed that the temperature and relative humidity significantly affected the release of sulfur dioxide gas in which the highest gas release was observed at the temperature of 25 °C and relative humidity of 95% (3.64 mmol/L). Also, rising the amount of MBS increased the release rate of sulfur dioxide, significantly. The highest release of sulfur dioxide (4.25 mmol/L) was achieved at a concentration of 50% salt. In the next step, the prepared sheets were laminated to control the release of sulfur dioxide. Paper with a thickness of 30 μm and polyethylene film with a thickness of 25 μm were used to laminate the film. The results revealed that laminating the sheets as single or double side slowed down the release rate of sulfur dioxide from the sheets, and thus, its releasing was controlled. The results also showed that the rate of gas release and its control were higher in dual release sheets. The presence of sodium metabisulfite salt in CA sheet was confirmed through FTIR, XRD and SEM analyses.