The massive use of synthetic plastics, in particular in the food packaging area, has a great environmental impact, and alternative more ecologic materials are being required. Poly(lactic) acid (PLA) and starch have been extensively studied as potential replacements for non-degradable petrochemical polymers on the basis of their availability, adequate food contact properties and competitive cost. Nevertheless, both polymers exhibit some drawbacks for packaging uses and need to be adapted to the food packaging requirements. Starch, in particular, is very water sensitive and its film properties are heavily dependent on the moisture content, exhibiting relatively low mechanical resistance. PLA films are very brittle and offer low resistance to oxygen permeation. Their combination as blend or multilayer films could provide properties that are more adequate for packaging purposes on the basis of their complementary characteristics. The main characteristics of PLA and starch in terms of not only the barrier and mechanical properties of their films but also of their combinations, by using blending or multilayer strategies, have been analyzed, identifying components or processes that favor the polymer compatibility and the good performance of the combined materials. The properties of some blends/combinations have been discussed in comparison with those of pure polymer films.

Antimicrobial and antioxidant properties of essential oils have previously been extensively reviewed. The mechanisms of action of essential oils have not been clearly identified but they seem to be related with their hydrophobic nature. Applying these natural compounds in the food industry could be a potential alternative, but its application costs and other problems, such as their intense aroma and potential toxicity, limit their use in the area of food preservation. An interesting strategy to reduce doses of essential oils while maintaining their effectiveness could be the incorporation of these natural compounds into edible/biodegradable films. This review discusses the use of essential oils as natural antimicrobial and antioxidant compounds to obtain bioactive films or coatings. The advantages and limitations are also reviewed.

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Cassava starch films containing 25 and 50 % (in the polymer blend) of bovine gelatin were obtained using glycerol (30 %) as plasticizer. Film formulations were also obtained with 15 % of lipid (blend of fatty acid-glycerol esters). Microstructural and physical (optical, barrier and mechanical) properties were analysed in order to compare blend films with neat starch or gelatin films. The incorporation of gelatin and lipids to glycerol-plasticized cassava starch films notably affected their physical properties, while they showed polymer-phase separation and a lipid-dispersed phase. Gelatine incorporation gave rise to harder films with greater resistance to break and extensibility, while the lipids decreased film hardness and resistance but enhanced the stretchability, especially in films with 50 % gelatin content. Likewise, lipids improved water barrier properties of the films, but they impaired the oxygen permeability at the same time as they decreased the film gloss and transparency. After 5 weeks of storage, all the films became harder and more resistant to break, especially those which did not contain lipids, which enhanced the films' extensibility during storage. Cassava starch films with 50 % gelatine, both with and without lipids, exhibited very adequate properties for food coating or packaging.