DEVELOPMENT AND CHARACTERIZATION OF HYDROPHILIC ACTIVE POLYMERS FOR FOOD PACKAGING APPLICATIONS 
ABSTRACT
This PhD dissertation thesis has been focused on two interesting active packaging systems which aim has been the control of oxidation processes in packaged food and the retention of undesired components initially present in food or developed during storage. 
Two hydrophilic polymers EVOH and PVOH, widely used in packaging design to provide barrier properties have been used as polymeric matrices for these active packaging systems. The hydrophilic nature of these polymers and the presence of polar groups impart an adequate interaction with the added agents and provide a triggering mechanism of activity very useful for the technological application.
To delay food deterioration caused by oxidative processes, natural antioxidant substances (ascorbic acid, ferulic acid, catechin, quercetin and green tea extract) were incorporated to the polymer by melt-mixing during extrusion (EVOH 44) or by solution/evaporation (EVOH 29). The physicochemical properties of the materials developed were characterized, evaluating the effect of the addition of the antioxidants and the effect of the type of processing. The release of these agents into various food simulants was fully characterized and the activity in the protection of food products was confirmed in fried peanuts, sunflower seed oil and brined sardines. All materials presented a significant antioxidant activity, the agent release being dependent on the concentration of the additive and their solubilities in the simulants. In general, the functional properties of the polymers as materials for the design of food packages were not relevantly affected by the incorporation of the antioxidants.

Scavenging activity of undesired components was focused on the control of cholesterol in whole milk and the control of byproducts produced by fat oxidation through the formation of inclusion complexes with cyclodextrins immobilized in EVOH and PVOH films.
Cyclodextrin containing EVOH films obtained by extrusion were mainly transparent with some discontinuities caused by accumulation of the agent. The incorporation of the oligosaccharides produced a slight increase in the permeability to gases and vapors owing to an increase in free volume. Films presented a significant effect on cholesterol content of milk and on the accumulation of aldehydes produced by oxidation of packaged peanuts. Cyclodextrin containing PVOH films obtained by casting received a cross-linking treatment with glyoxal to improve the immobilization of the cyclodextrin and the solution of the polymer. Tests with milk proved that the films were active as scavengers of cholesterol.