Mirpoor, Seyedeh Fatemeh (2022) Protein-based bioplastics from seed oilcakes. [Tesi di dottorato]

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Abstract

The use of petroleum-based plastics in different fields, such as food and pharmaceutical sectors, has increased significantly in the last 50 years, being the durability of the plastic materials, as well as their outstanding features, the main reason of their success. However, their worldwide applications led to huge waste-disposal problems and, as a consequence, to a dramatic environmental pollution. These issues have encouraged innovation and research activities in the field of biodegradable plastics, offering alternatives for conventional plastics. One potential option to pursue would be to explore agri-food wastes and by-products for bioplastic production. Numerous different seeds are utilized for edible and non-edible oil extraction and seed by-products following oil extraction. These by-products are known as seed oil cakes (SOCs) and represent roughly 50% of the original seed weight. Since SOCs are rich in fibers, proteins and secondary metabolites, they are considered as promising candidates to be raw material consumed in a biorefinery for the production of bioplastics. In this scenario the present thesis provides insights into the production and characterization of bioplastics obtained by using the proteins extracted from hemp (Cannabis sativa), cardoon (Cynara cardunculus) and argan (Argania spinosa L.) SOCs. Different conditions, such as i) change in pH, ii) protein amount and iii) plasticizer concentration were exploited in order to find the best conditions to develop these protein-based films. To achieve innovative films with improved features the films showing the best characteristics were also modified by adding different additives. Hemp proteins (HPs) and cardoon proteins (CPs) were preliminarily cross-linked by means of microbial transglutaminase (mTGase) and an improvement in both mechanical and barrier properties of the derived films was observed. The results obtained from wrapping peanuts revealed that films prepared with enzyme-modified CPs are able to prolong the shelf life of the oily food. Moreover, nanocrystalline cellulose (NC) and the lignin fraction (LF), obtained from egagropili and added to the HP-based film forming solutions, enhanced the film technological properties. To develop an active bioplastic, cardoon leaf extract (CLE) was tested as additive of CP-based films and a further enhancement of the mechanical, barrier properties and antioxidant activity of the obtained materials was observed. Finally the interfacial properties of the SOC proteins and the surface wetting of the obtained bioplastics were studied in the period of stay at the Department of Applied Physics of the University of Granada (Spain).

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