Produção de filmes biodegradáveis e aprimoramento de suas propriedades utilizando tecnologias não térmicas

Abstract

Starch-based films, despite being a promising biodegradable packaging alternative, face performance challenges due to their high solubility and low hydrophobicity. To overcome these limitations, the study explored three strategies: DBD plasma, incorporation of anthocyanin-rich extracts (grape and acerola residues), and addition of carrageenan. In stage I, the effects of DBD plasma were evaluated on the physicochemical and structural properties of cornstarch. Different frequencies (100, 200, and 300 Hz) and exposure times (10 and 20 min) were tested. The 200 Hz treatment for 20 min was the most effective, causing the greatest changes in the amylose-to-amylopectin ratio, solubility, water absorption, and morphology. The starch surface became smoother and more porous. Minor changes in the ordered structure of the starch were observed, as determined by FTIR. Stage II consisted of producing films (5% w/w) by casting using the starch from stage 1 and plasma treating the film-forming solution using the same molds tested previously. The results showed significant differences in their physicochemical and morphological properties. Most of the chemical changes occurred in the starch subjected to plasma before film formation, while the films produced with untreated starch showed physical changes. In stage III, anthocyanin extracts were added to the films along with DBD treatment under optimized conditions. The starch films with acerola and grape extracts, separately, showed a good colorimetric response for pH indication, but with some disadvantages in physicochemical properties, such as moisture and solubility, but without significantly altering the contact angle, amylose content, or FTIR spectra. Finally, stage IV involved the addition of carrageenan to the starch films (2.5% w/w each) and anthocyanins. The film's pH-indicating capability (more satisfactory with grape extract) and improved physical properties, such as increased hydrophobicity (contact angle increased from 52.9° to 74.8° with grape pomace extract), were confirmed. In summary, the application of plasma proved capable of improving film properties without compromising food freshness indication via the colorimetric response of anthocyanins to pH variations. For a smart film, the recommendation would be to use plasma, carrageenan, and grape extract.