Potential of Lignins as Antioxidant Additive in Active Biodegradable Packaging Materials

Lien vers la version éditeur: http://link.springer.com/article/10.1007/s10924-013-0570-6Due to their polyphenolic structure lignins bear a number of interesting functional properties, such as antioxidant activity. Natural antioxidants are very much looked for in the aim of protection of light or oxygen sensitive goods and are being used in active packaging. Poly(lactide) (PLA)-lignin films were prepared by twin screw extrusion followed by thermo-compression using two different commercial sources of alkali lignins obtained from gramineous plants. A good dispersion of lignin in the matrix was observed. Mechanical properties of the compounded material were merely diminished and oxygen barrier properties slightly enhanced. The chromatographic study of the lignins revealed that the low molecular weight fraction of both lignins increased during the polymer processing. The migration of low molecular weight compounds in an ethanol/water solution simulating fatty foodstuff was performed and the antioxidant activity of the extract was analysed. It was found that the activity increases with increasing severity of the heat treatment because of the generation of free phenolic monomers during processing. These results open an interesting way for application of lignins as an active compound in packaging materials. Lignins do not impair the mechanical and barrier performance of the polymer and the plastics processing even allows for the generation of active substances

LignoStarch Tailored modification of starch by radiation-grafting of lignin

National audienceThermoplastic Starch (TPS) represents ca 80% of the biopolymer market, however, unlike petroleum based polymers, TPS is still manufactured by traditional methods of extrusion and injection molding. Starch is a semi-crystalline renewable biopolymer made of glucose units existing as a mixture of linear polymer chains (amylose) and branched polymer chains (amylopectin). Due to its hydrophyllic nature, starch products show retrogradation and varying mechanical properties with time. Lignin, another renewable biopolymer and a by-product of the paper industry is hydrophobic and limits water sensitivity of TPS blends. Electron Beam radiation-induced grafting of lignin models onto starch/maltodextrin is shown to result in physical stability of the blends with limited loss of mechanical properties, improved surface hydrophobicity, and to impede long-term retrogradation. Lignin, another renewable biopolymer and a by-product of the paper industry is hydrophobic and limits water sensitivity of TPS blends. Electron Beam radiation-induced grafting of lignin models onto starch/maltodextrin is shown to result in physical stability of the blends with limited loss of mechanical properties, improved surface hydrophobicity, and to impede long-term retrogradation

Compensation strategies in response to fatiguing propulsion in wheelchair users : implications for shoulder injury risk

Objective: The aims of the study were to examine whether fatigue-inducing wheelchair propulsion changes neuromuscular activation and propulsion biomechanics and to determine predictor variables for susceptibility to fatigue. Design: This study with a quasi-experimental, one-group, pretest-posttest design investigates a population-based sample of wheelchair users with a spinal cord injury (n = 34, age: 50.8 +/- 9.7 yrs, 82% males). Neuromuscular activation and propulsion biomechanics during treadmill propulsion at 25 W and 45 W were assessed before and after a protocol designed to cause fatigue. Results: With the induced fatigue, wheelchair users propelled with increased neuromuscular activation in the pectoralis major pars sternalis, deltoideus pars acromialis and upper trapezius (45 W, P < 0.05), and a slightly reduced push angle (25 W: 75-74 degrees, P < 0.05, 45 W: 78-76 degrees, P < 0.05). Wheelchair users susceptible to fatigue (47%) were more likely to have a complete lesion, to be injured at an older age, and had less years since injury. This group propelled in general with shorter push angle and greater maximum resultant force, had a greater anaerobic capacity, and had less neuromuscular activation. Conclusions: Compensation strategies in response to fatiguing propulsion could increase the risk for shoulder injury. Predictor variables for susceptibility to fatigue inform interventions preserving shoulder health and include lesion characteristics, propulsion technique, anaerobic capacity, and neuromuscular activation