Lucía Famá

Biodegradability and plasticizing effect of yerba mate extract on cassava starch edible films.

Biodegradable and edible cassava starch-glycerol based films with different concentrations of yerba mate extract (0, 5 and 20wt.%) were prepared by casting. The plasticizing effect of yerba mate extract when it was incorporated into the matrix as an antioxidant was investigated. Thermal degradation and biodegradability of the obtained biofilms were also studied. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR), X-ray diffraction analysis (XRD), water absorbance, stability in different solutions and biodegradability studies were performed. The clear correlation among the results obtained from the different analysis confirmed the plasticizing effect of yerba mate extract on the starch-glycerol matrix. Also, the extract led to a decrease in the degradation time of the films in soil ensuring their complete biodegradability before two weeks and to films stability in acidic and alkaline media. The plasticizing effect of yerba mate extract makes it an attractive additive for starch films which will be used as packaging or coating; and its contribution to an earlier biodegradability will contribute to waste reduction.

Effect of beet flour on films made from biological macromolecules: Native and modified plantain flour

Biological macromolecules such as starches of different amylaceous sources have been used in the formulation of edible films. However, there are few studies aimed at evaluating edible and intelligent films with response to pH changes from natural pigments, this despite the importance of these materials. In this context, films from native and modified plantain flour, plasticized with glycerol, with or without the addition of beet flour were developed. The chemical and structural composition of the flours, and its incidence on thickness, water solubility, contact angle, and mechanical and microstructural properties were evaluated, thus as its response to pH changes of the developed films. The observations showed that the incorporation of beet flour allowed to obtain intelligent films front to pH changes alkaline. Likewise, the betalains that were found in beet flour interacted more efficiently with the phosphated plantain flour, limiting well its immediate response to pH changes. In the same way, proteins and sugars of beet flour allowed to obtain more flexible films, due to the hydrogen bond interactions between these constituents and the plantain flours. This latter could justify the decrease of contact angle, and the increase on thickness and solubility of these films.

Size effect of ZnO nanorods on physicochemical properties of plasticized starch composites

This work demonstrates that the size of ZnO nanorods (ZnONR) with similar aspect ratio determines several physicochemical and microbiological properties of thermoplastic starch composites (TPS/ZnONR) at a given concentration of ZnONRs. A combination of sol-gel and hydrothermal methods was developed to synthesize ZnONR with different sizes but similar aspect ratios. Starch composites containing 1wt.% of ZnONR were prepared by casting. Composites with smaller size nanorods (ZnONR-S) showed more efficiency in shielding UVA radiation and had a higher solubility and water vapor permeability than those with larger nanorods (ZnONR-L). Mechanical properties, biodegradability and antibacterial activity were also influenced by the size of the ZnONR. X-ray diffraction analysis showed that composites with ZnONR-S maintained the typical B-V type starch structure, intensifying the V-type starch structure peaks, while composite with ZnONR-L induced the formation of an amorphous structure, preventing starch retrogradation during storage. Properties affected by nanorods size are fundamental in determining composite applications.

Active and smart biodegradable packaging based on starch and natural extracts

Active and smart biodegradable films from cassava starch and glycerol with 5wt.% of different natural extracts such as green tea and basil were obtained by casting. Their functional capacity as antioxidants and their physicochemical properties achieved from the incorporation of these types of extracts were evaluated. The content of phenolic compounds in the extracts led to films with significant antioxidant activity, being greater in the case of the system containing green tea extract. Color changes in both materials after immersion in different media (acid and basic) due to the presence of chlorophyll and carotenoids in the extracts were observed, but the film with basil extract reacted most notably to the different pH. These films degraded in soil under two weeks and were thermal stable up to 240°C. Finally, the incorporation of extracts of green tea and basil led to thermoplastic starch films with lower water vapor permeability retaining their flexibility.