Obtaining active extracts from beet root leaves and stems (BLS) is an alternative for the valorization of this agricultural waste. Subcritical water extraction (SWE) at 150 °C and 170 °C has been used to obtain these extracts, which were incorporated (6% wt.) into polymer matrices to produce antioxidant films of thermoplastic starch (TPS) and polylactic acid (PLA) for the preservation of sunflower oil. A high extraction yield (67–60% solubilized solids) was achieved, and the extracts contained high levels of total phenols (51–73 mg GAE·g⁻¹ extract) and betalains and great radical scavenging capacity (EC₅₀: 30–22 mg mg⁻¹ DPPH). The highest temperature promoted the extract’s phenolic richness and antioxidant capacity. The TPS and PLA films containing extracts exhibited color and UV-light blocking effects. The extracts reduced the oxygen permeability (OP) and water vapor permeability of PLA films while promoting those of the TPS films. The capacity of the films to preserve sunflower oil from oxidation was mainly controlled by the OP values of the films, which were very high in TPS films with low OP values. However, in the PLA films (which were more permeable to oxygen), the antioxidant extracts provided significant protection against sunflower oil oxidation.

Purpose: This is one of the innovative studies that performs a comparative study of active and biodegradable starch-based films containing natamycin, produced by casting and thermo-compression methods to improve the microbiological stability of Argentinian Port Salut cheese.Design/methodology/approach: Barrier and diffusion tests were carried out in order to evaluate the effectiveness of the films as antifungal packaging.Findings: Films exhibited strong barrier action, with cast films proving to be the most effective yeast inhibitors. In the diffusion test, both types of films loaded with natamycin demonstrated a decrease in Zygosaccharomyces bailii counts after 48 h. Casting films significantly reduced Zygosaccharomyces rouxii and Saccharomyces cerevisiae counts after 48 h, while thermo-compression films partially inhibited yeasts. Casting films presented the most effective antimicrobial action in protecting cheese against yeast contamination.Originality/value: This study provides a comparative analysis of the impact of processing methods on the properties of starch-based films incorporating the natural antimicrobial, natamycin. This research studies edible films based on tapioca starch, with or without natamycin, produced by means of casting and thermo-compression techniques, and compares the films antimicrobial properties against Z. bailli, Z. rouxii and S. cerevisiae using model systems and Argentinian Port Salut cheese.