RESUMO
Rosemary (Rosmarinus officinalis L.) is known to be an effective potential source of natural antioxidants which confer benefits to human health. Their bioactive properties are mainly due to phenolic compounds but these molecules are highly vulnerable to oxidants, light, heat, pH, water and enzymatic activities. Therefore, the stability and shelf life of phenolic compounds should be increased by being protected from chemical and physical damage by means of encapsulation prior to application. Encapsulation is becoming increasingly important in the pharmaceutical, food, cosmetics, textile, personal care, chemical, biotechnology, and medicinal industries due to its potential for stabilization and delivery of delicate and precious bioactive compounds. The aim of the present work was to describe the polyphenolic profile of Tunisian Rosemary, collected from two different bioclimatic areas, and further loading in silk fibroin nanoparticles. The loaded nanoparticles were characterized in terms of morphology, size, polydispersity, Z-potential, secondary structure of the protein, encapsulation efficiency, loading content, and antioxidant activity. On one hand, HPLC analysis revealed the presence of 18 polyphenolic compounds of whichcarnosic acid and carnosol were found to be the most abundant compounds (46.3 to 76.4 and 22.4 to 43.5 mg of compound per gram of dry plant weight (mg/g DPW) respectively), Total phenolic content (TPC) ranged from 85.8 to 137.3 mg of gallic acid equivalent (GAE)/g DPW in post-distilled rosemary extracts andantioxidant activity reached the values of 5.9 to 8.3 µmol of ascorbic acid equivalent (AAE)/g DPW). On the other hand loaded nanoparticles were almost spherical and presented nanometric size and negative Z-potential. Although the encapsulation efficiency in silk fibroin nanoparticles and the drug loading content were low in the conditions of the assay, the encapsulated polyphenols retained near 85% of the radical scavenging activity against DPPH· after 24 h. of incubation at 37 °C. The results showed that post-distilled rosemary residues had an effective potential as natural antioxidants due to their significant antioxidant activity and seemed to be useful in both pharmaceutical and food industries with beneficial properties that might confer benefits to human health and these silk fibroin nanoparticles loaded with rosemary extracts are thus a promising combination for several applications in food technology or nanomedicine.
RESUMO
The main objective of the present research is to study the effect of the incorporation of low amounts of silk fibroin nanoparticles (SFNs) and yerba mate nanoparticles (YMNs) on the migration phenomenon into ethanolic food simulants as well as on the disintegrability under composting conditions of mechanically recycled polylactic acid (PLA). Recycled PLA was obtained under simulated recycling conditions by melt processing virgin PLA into films and further subjecting them to an accelerated aging process, which involved photochemical, thermal, and hydrothermal aging steps followed by an intense washing step. SFNs were extracted from Bombyx mori cocoons and YMNs from yerba mate waste. Then, recycled PLA was melted, reprocessed, and reinforced with either 1%wt. of SFNs or YMNs, by melt extrusion, and further processed into films by compression molding. The obtained nanocomposites were exposed to ethanolic food simulants (ethanol 10% v/v, simulant A and ethanol 50% v/v, simulant D1) and the structural, thermal, and mechanical properties were studied before and after the exposure to the food simulants. The migration levels in both food simulants were below the overall migration limits required for food contact materials. The materials were disintegrated under simulated composting conditions at the laboratory scale level and it was observed that the nanoparticles delayed the disintegration rate of the recycled PLA matrix, but nanocomposites were fully disintegrated in less than one month.
RESUMO
Poly(lactic acid) (PLA) is one of the most used biobased and biodegradable polymers. Due to their high stability, some of the newest grades of PLA are only degradable under severe industrial conditions. For these grades, mechanical recycling is a viable end-of-life option, with great environmental advantages. However, the polymer undergoes degradation during its service life and in the melt reprocessing, which leads to a decrease in properties that can compromise the recyclability of PLA. The goal of this work was to evaluate the usefulness of adding small amounts of two organic fillers, chitosan, and silk fibroin nanoparticles, during the recycling process for improving the properties of the recycled plastic. The degradation level of the aged polymer and the nature and amount of filler affect the performance of the recycled plastics. The fillers reduce the degradation during the melt reprocessing of PLA previously subjected to severe hydrolysis, thus increasing the intrinsic viscosity of the recycled plastic. A careful selection of the added organic filler lead to recycled plastics with improvements in some key mechanical, thermal, and barrier properties. Thus, the use of organic fillers represents a cost-effective and environmentally sound way for improving the mechanical recycling of bioplastics.
