Effects of high hydrostatic pressure processing on structure and functional properties of biodegradable film.

Effects of high hydrostatic pressure (HHP) processing (200-400 MPa/5 or 10 min) on functional properties of cellulose acetate (CA) films were investigated. As for mechanical properties, HHP caused a reduction in tensile strength (TS), Young's modulus (YM) and an increase in elongation at break (EB). The pressurized films were more luminous, yellowish, reddish and opaque. Less affinity for water was detected for pressurized films through analyses of contact angle and moisture absorption, in addition to reducing the water vapor transmission rate (WVTR). Scanning electron microscopy (SEM) showed the occurrence of delamination for most films, except those treated with 200 MPa/10 min and 300 MPa/10 min. All films showed a predominance of amorphous structure in X-ray diffraction analysis (XRD). That is alignment with the results of differential scanning calorimetry (DSC), which presented values for glass transition temperature (Tg), water adsorption and melting temperature characteristic of materials with low crystallinity. Films treated with HHP had better mechanical resistance during the sealing at 250 °C. In overall the results confirmed the minimal influence of HHP on the functional properties of the CA film and contributed to the scientific and technological knowledge for its potential application in foods processed by HHP.

Structure and functional properties of cellulose acetate films incorporated with glycerol.

Tests were performed with cellulose acetate films (CA) incorporating 5, 10, 20, 30, and 50% (w/v) of glycerol with the purpose of evaluating the possible changes caused by the plasticizer on the functional properties of the packaging. The glass transition temperature (Tg) and relative crystallinity (RC) were are obtained by DSC and XRD, respectively. The results showed that, the presence of glycerol in the films caused increased thickness, water vapor transmission rate (WVTR), and optical properties for most treatments. Moreover, morphological changes were evidenced in scanning electron microscopy (SEM). A reduction of tensile strength (TS) and Young's modulus (YM) was observed only in the concentration of 50% of glycerol. Therefore, the results suggest that there was an interaction between glycerol and cellulose acetate, demonstrating that the film has potential for use as food packaging.