Mercedes Ana Peltzer

Effects of modified cellulose nanocrystals on the barrier and migration properties of PLA nano-biocomposites.

The aim of this paper is to report the impact of the addition of cellulose nanocrystals on the barrier properties and on the migration behaviour of poly(lactic acid), PLA, based nano-biocomposites prepared by the solvent casting method. Their microstructure, crystallinity, barrier and overall migration properties were investigated. Pristine (CNC) and surfactant-modified cellulose nanocrystals (s-CNC) were used, and the effect of the cellulose modification and content in the nano-biocomposites was investigated. The presence of surfactant on the nanocrystal surface favours the dispersion of CNC in the PLA matrix. Electron microscopy analysis shows the good dispersion of s-CNC in the nanoscale with well-defined single crystals indicating that the surfactant allowed a better interaction between the cellulose structures and the PLA matrix. Reductions of 34% in water permeability were obtained for the cast films containing 1 wt.% of s-CNC while good oxygen barrier properties were detected for nano-biocomposites with both 1 wt.% and 5 wt.% of modified and un-modified cellulose nanocrystals, underlining the improvement provided by cellulose on the PLA films. Moreover, the migration level of the studied nano-biocomposites was below the overall migration limits required by the current normative for food packaging materials in both non-polar and polar simulants.

Grain sorption equilibria of quinoa grains

Abstract Quinoa has been identified as a promising source of food. Reports in the literature have focused mainly on agronomic potential, composition, nature of the starch and protein quality. Other aspects related with drying and storing of quinoa seed have received less attention. Moisture sorption isotherms constitute an essential part of the theory of drying and in the study of storage of dehydrated foods. Vapour water sorption of quinoa grains was determined at 20, 30 and 40 °C in the range of 0.089–0.851 water activity ( a w ) by means of the gravimetric method. Experimental curves were fitted to one three-parameter equation (Guggenheim–Anderson–de Boer, GAB equation). The equilibrium values and temperature shifts were modelled with a three-parameter equation in the approximate moisture content range of 0.02–0.18 (g water/g dry matter). An analytical expression to calculate the isosteric heat of sorption and its moisture content dependence was used and the results were compared with the isosteric heat calculated from the experimental equilibrium data by means of the Clausius–Clapeyron equation. The GAB model describe the sorption isotherms of quinoa grains at different temperatures in the range of a w investigated, the sorption areas obtained from the GAB equation were comparable with other sorption areas reported in the literature for various cereal grains and the effect of temperature on water sorption isotherms is adequately describes by an equation based on the enthalpy-entropy compensation.

Nano-biocomposite films with modified cellulose nanocrystals and synthesized silver nanoparticles

Ternary nano-biocomposite films based on poly(lactic acid) (PLA) with modified cellulose nanocrystals (s-CNC) and synthesized silver nanoparticles (Ag) have been prepared and characterized. The functionalization of the CNC surface with an acid phosphate ester of ethoxylated nonylphenol favoured its dispersion in the PLA matrix. The positive effects of the addition of cellulose and silver on the PLA barrier properties were confirmed by reductions in the water permeability (WVP) and oxygen transmission rate (OTR) of the films tested. The migration level of all nano-biocomposites in contact with food simulants were below the permitted limits in both non-polar and polar simulants. PLA nano-biocomposites showed a significant antibacterial activity influenced by the Ag content, while composting tests showed that the materials were visibly disintegrated after 15 days with the ternary systems showing the highest rate of disintegration under composting conditions.

Development of novel nano-biocomposite antioxidant films based on poly (lactic acid) and thymol for active packaging

Novel nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by incorporating thymol, as the active additive, and modified montmorillonite (D43B) at two different concentrations. A complete thermal, structural, mechanical and functional characterization of all nano-biocomposites was carried out. Thermal stability was not significantly affected by the addition of thymol, but the incorporation of D43B improved mechanical properties and reduced the oxygen transmission rate by the formation of intercalated structures, as suggested by wide angle X-ray scattering patterns and transmission electron microscopy images. The addition of thymol decreased the PLA glass transition temperature, as the result of the polymer plasticization, and led to modification of the elastic modulus and elongation at break. Finally, the amount of thymol remaining in these formulations was determined by liquid chromatography (HPLC-UV) and the antioxidant activity by the DPPH spectroscopic method, suggesting that the formulated nano-biocomposites could be considered a promising antioxidant active packaging material.

Migration study of carvacrol as a natural antioxidant in high-density polyethylene for active packaging

The migration behaviour of low molecular weight compounds from food packaging materials is one of the key issues in assessing the possibility of use in such applications. The aim of this work was to study the migration of carvacrol (1% and 2% w/w) when added to high-density polyethylene. All materials were exposed to the food simulants olive oil and distilled water separately at 40°C and 25°C. Three significant variables influencing the migration process were considered: incubation temperatures, the initial concentration of antioxidant, and the type of simulant (oil and aqueous). The amount of carvacrol migrating to olive oil was significantly higher than in water because of the higher solubility of this antioxidant in oil. Experimental results agreed reasonably well with those obtained by the application of a simple model derived from Ficks Second Law. Carvacrol could therefore be used in active packaging formulations as its release from the polymer matrix can be controlled.

PLA-Based Nanocomposites Reinforced with CNC for Food Packaging Applications: From Synthesis to Biodegradation

Poly(lactic acid) (PLA) is currently the most used biopolymer in several food packaging applications at industrial level, due to its many advantages such as high transparency, availability in the market, and ease of processing. However, PLA presents some drawbacks such as its poor mechanical, thermal, and barrier properties. The addition of nanofillers to PLA matrix leads to an enhancement in the thermomechanical performance. The optimal nanofiller should be nontoxic, approved for food contact, renewable, and biodegradable. Cellulose derivatives, particularly cellulose nanocrystals (CNCs), are optimal fillers with interesting properties (i.e., stiff, lightweight, highly abundant in nature, at low cost, and biodegradable). In this chapter the current industrial PLA obtainment, processing, and compostability are reviewed in relation to its application as sustainable food packaging material. The advantages of reinforcing PLA with CNC to improve the thermal, mechanical, and barrier performance of the final bionanocomposites are also summarized.

Nanocellulose-Based Polymeric Blends for Food Packaging Applications

Abstract Nanocellulose has gained considerable attention in the food packaging industry as a nanoreinforcement for polymer matrices, mainly those biobased and biodegradable. Derived from the most abundant polymeric resource in nature and with inherent biodegradability, nanocellulose is an interesting nanofiller for the development of bionanocomposites processed by traditional processing techniques. Due to the high number of hydroxyl groups on its surface, nanocellulose is easy to functionalize, mainly to improve its dispersion within the polymer matrix. Well-dispersed nanocellulose is able to enhance several properties of polymers, including thermal, mechanical, barrier, and surface wettability properties, as well as control of active compound release, etc. This chapter reviews the most relevant processing aspects of nanocellulose-based polymeric blends such as thermal stability and nanofiller dispersion. It also summarizes recent developments in biobased and biodegradable nanocellulose-based polymeric blends for food packaging with an emphasis on bionanocomposite properties and a focus on the sustainable food packaging field.