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Item Type: Tesi di dottorato
Resource language: English
Date: 18 January 2019
Number of Pages: 145
Institution: Università degli Studi di Napoli Federico II
Department: Scienze Chimiche
Dottorato: Biotecnologie
Ciclo di dottorato: 31
Coordinatore del Corso di dottorato:
Porta, RaffaeleUNSPECIFIED
Di Pierro, ProsperoUNSPECIFIED
Date: 18 January 2019
Number of Pages: 145
Keywords: Bioplastic, coatings, edible films, food shelf-life
Settori scientifico-disciplinari del MIUR: Area 05 - Scienze biologiche > BIO/10 - Biochimica
Date Deposited: 15 Jan 2019 09:13
Last Modified: 04 Apr 2022 09:05

Collection description

The current alarming scenario of plastic pollution shows that more than 700 thousand plastic shopping bags and 400 thousand plastic bottles are consumed worldwide every minute. Consequently, about 35 millions tons of plastic wastes are annually produced in the entire world but only 7% of them are recycled. Moreover, when in contact with foods, many petrol-derived plastics can be harmful for human health, causing severe damages to the endocrin system. Possible solutions to these huge environmental and health problems may be (i) the biodegradation of the plastic materials, (ii) the synthesis of oil-derived biodegradable materials, (iii) the synthesis of substituting biodegradable materials derived from natural sources called “bioplastics”. Several edible bioplastics are currently used to coat or wrap highly perishable foodstuff to protect their nutritional and organoleptic properties by extending food shelf-life and reducing the negative effects caused by food processing, such as enzymatic browning, texture breakdown and off-flavors development. Protein and polysaccharides represent two of the main biopolymers used to prepare biodegradable/edible films, even though they still present several disadvantages due to the limited mechanical and/or barrier properties of the derived bioplastics. The present work was carried out to prepare and characterize new hydrocolloid materials made with either a concentrate of proteins extracted from bitter vetch (Vicia ervilia) seeds (BVPC) or from chitosan (CH), a polymer derived from chitin, the second most abundant polysaccharide occurring in nature. To achieve innovative films with improved features we investigated the effectiveness of the addition of new compounds possessing plasticizing activities to BVPC and CH film forming solutions, such as the aliphatic polyamines, as well as the procedures of both blending of BVPC with the polysaccharide pectin (PEC) and protein crosslinking by the enzyme transglutaminase of microbial origin (mTGase). Our findings suggested that the use of spermidine (SPD) or of a combination of the polyamine with a primary plasticizer such as glycerol (GLY), as additives of BVPC-based films, may open new possibilities to generate hydrocolloid edible biomaterials endowed with improved mechanical and/or barrier properties specifically suitable for the coating/wrapping of different food products. The obtained results indicates that SPD is not only able to act as a plasticizer itself, by interacting with proteins by both hydrogen and ionic bonds as demonstrated by FT-IR analysis, but that it also facilitates GLY-dependent reduction of the intermolecular forces along the protein chains, consequently improving film flexibility and extensibility. Thus, SPD was demonstrated to be not only a primary, but also as a secondary plasticizer because of its ability to enhance GLY plasticizing performance. Moreover, the blending of BVPC with PEC in the presence or absence of mTGase is the other way to achieve further innovative edible bioplastics. In fact, PEC addition markedly decreased the gas permeability of BVPC films and mTGase-catalyzed protein crosslinks determined a further enhancement of their barrier properties. These findings, supported by SEM morphological analyses, suggest that the improved functional features depend on film more compact structure due to crosslinked proteins grafted with PEC. Since chitin waste, mainly produced from seafood processing (crustacean shells), still represents a major environmental issue, the attention was also addressed to improve the mechanical and barrier properties of CH-based bioplastics by assaying SPD, with and without GLY, as new plasticizer. Our findings demonstrated that SPD containing CH films were always more extensible, exhibiting an elongation at break higher than that observed with glycerol-plasticized films, as a consequence of the occurrence of both hydrophobic and H-bonding interactions of SPD with CH chains observed in FT-IR spectra. Furthermore, the concurrent presence of appropriate concentrations of SPD and GLY enhanced the plasticity of the new biomaterial, conferring to it the ability to be also heat-sealed. Finally, all the prepared CH films exhibited a clear antimicrobial activity, thus representing credible candidates as food preservative coatings and/or wrappings. A preliminary application of the new obtained biomaterials was realized by wrapping salted and unsalted Nabulsi cheese samples. In fact, many undesirable changes such as discoloration, off-flavor production, slime and gas formation, bitterness and textural problems may occur with Nabulsi cheese, a typical Palestinian fresh dairy product produced by traditional methods, during its storage in large cans, also in spite of high brine concentration. The obtained results demonstrate that the wrapping of the unsalted Nabulsi cheese by hydrocolloid films (mostly BVPC-based ones) has the same effects of LDPE wrapping, as well as of the salting treatment, in preventing the lowering of pH and the increase of titratable acidity occurring during the storage of the unwrapped dairy product. A possible industrial production of unsalted Nabulsi cheese wrapped with the reported edible film would present the advantages to increase its shelf-life, avoid any postprocess contamination, and enhance the following possible demand for an unsalted, healthy and ready-to-eat cheese, potentially to be used also in sweet pastry.


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