UV-SHIELDED BIODEGRADABLE FILMS PRODUCED FROM WHOLE GRAPE BY-PRODUCTS

The excessive disposal of single-use plastics has driven the search for sustainable alternatives, especially those based on renewable and biodegradable sources. This study evaluated the use of grape processing by-products (blend of Bordô, Concord and Isabel cultivars) in the production of biodegradable films with potential use as active packaging for food. The by-product was subjected to mild hydrolysis with citric acid (0.1 mol· L⁻¹, 40 °C, for 16 h), and incorporated into two polymeric formulations with a total solids of 1.3 g, approximately 77% of which is composed of the by-product: F1 (23% pectin) and F2 (17% pectin and 6% carboxymethylcellulose – CMC). The films were obtained by continuous casting, with glycerol (30% on a dry basis) as plasticizer.

The samples were characterized for mechanical, optical, barrier and infrared spectroscopy (FTIR) properties. In mechanical terms, F2 showed higher tensile strength (1.16 MPa) and elongation at break (31.7%) compared to F1 (0.77 MPa and 19.2%), indicating that the addition of CMC contributed to greater flexibility and integrity of the matrix. The elastic modulus did not show significant difference between the formulations (~5.2 MPa).

All samples showed excellent shielding to ultraviolet radiation, with blocking greater than 94% in the entire spectral range (UVA, UVB and UVC), highlighting its potential for protection of foods sensitive to photo-oxidation. Transparency was significantly higher in F1 (60.3%) than in F2 (10.2%), possibly due to the greater homogeneity of the pectin matrix and the lower optical interference of the CMC