Are modified pumpkin flour/plum flour nanocomposite films biodegradable and compostable?

Nanocomposite films made from nonconventional food hydrocolloids: phosphated or methylated flours derived from pumpkin (Cucurbita maxima) with or without "huesito" plum (Spondias purpurea) flour, were obtained by the casting methodology. The films were characterized, and in addition two biomarkers of ecotoxicity, survival and weight changes, were determined for each one by means of a novel bioassay using the furniture weevil (Tricorynus sp, Coleoptera: Anobiidae). The films prepared from the methylated flours had a lower sensitivity to water, greater thermal resistance and higher crystallinity percentage than the phosphated flour films. However, these materials were very fragile, as well as being ecotoxic, thus limiting their compostability. Thus, although both the phosphated and methylated pumpkin flour-based films were biodegradable only the phosphated films can be considered as eco-friendly. The plum flour nanocomposite was included due to the anthocyanins it contains, with the aim of developing pH-sensitive films. Unfortunately, neither of the resulting nanocomposite films achieved this objective. Nevertheless, their mechanical and thermal properties were improved, and the ecotoxicity levels reduced, compared to the films prepared without the nanocomposite.