DEVELOPMENT OF ENZIMATICALLY RETICULATED EDIBLE FILMS TO BE USED AS ACTIVE PACKAGING
Rossi Márquez, Giovanna (2011) DEVELOPMENT OF ENZIMATICALLY RETICULATED EDIBLE FILMS TO BE USED AS ACTIVE PACKAGING. [Tesi di dottorato] (Inedito)
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The use of plastic packaging is widely diffuse because this material possesses several advantages such as being lightweight, durable, easy to carry and having a low cost production. However, plastic packagings have the problem of not being biodegradable and, therefore, have a global environmental impact. Moreover when in contact with foods, petrol-derived plastics can be harmful for human health especially if the convey plasticizers such as polyvinylclhoride (PVC) that is can cause severe damages to endocrin system. A solution to this problem is to direct attention towards the development of packaging designed primarily for the food industry. (Floros et al.,1997). These innovative materials, that could be named edible films, are obtained from natural molecules like proteins, polysaccharides or lipids and are prepared using different techniques such as spray-drying, casting and dip-coating. In some cases, these films can be used as carriers of antimicrobial agents and are defined as active packaging. However, even if edible films are harmless for both human and environment health,, they possess pour mechanical and barriers properties compared to the traditional ones. Such properties can be improved by the inclusion of covalent bonds by transglutaminase (TGase), that is a biotechnological tool that can polymerize proteins through intermolecular cross-links -( - glutamyl) lysine. In this work we have obtained edible films made of Citrus pectin and TGase-crosslinked whey proteins, and evaluated their use as active packaging when conveying a peptide with antimicrobial activity. Moreover such films have been used to coat dry biscuits and fryed donuts to establish their effectiveness in extending biscuit shelf-life and reduction of fat up-take in donuts. The milk whey is the residue of cheese, is a highly polluting waste material despite being a reserve of high biological value food. As source of such proteins we have used a purchased product named Whey Protein Isolate (WPI) contaning: β-lactoglobulin (65%), α-lactoalbumin (25%), and bovine serum albumin (8%). WPI is largely used in the food industry as a milk substitute, for the production of ice cream, for increasing the protein content of foods, and as food for people that practise hard physical activity. Pectin is a heteropolysaccharide, consists mainly of acid D-galacturonic molecules linked by (-(1-4) and is obtained mainly from the peel of fruits of the Citrus family. In isolated form, pectin is rapidly reassociated to form aggregates or networks may also interact with proteins through hydrogen-type bonds, and ionic bonds.(Liu and Kost, 2009). These interactions can be improved by several treatments to obtain three dimensional complexes with improved mechanical and barrier properties. At the first beginning, the present research was focused on indentifying the best WPI/Pectin ratio and the pHc in order to obtaining the maximum degree of complexation. These parameters allowed us to obtain a stable colloidal solution that was used as the basis for the production of edible films crosslinked or not by TGase. Results have shown that the films obtained at a 4:1 ratio WPI/Pectin and pH 5.1 (pHc) crosslinked with TGase showed good mechanical properties and barrier water vapor and oxygen. In addition, the crosslinking created by TGase makes them a valid support for the release of molecules with antimicrobial activity. The application of these films by dip-coating technique has allowed us to create a layer on surface foods such as dry biscuits and donuts. Results obtained have shown that the application of the films on dry biscuits decreases absorption of water prolonging the shell-life, while applying the same coating to fried products like donuts significantly reduces the oil absorption. In conclusion, the TGase turns out to be a valuable biotechnology tool to reticulate soluble complexes obtained from WPI and Pectin, that allow to obtain edible films with good mechanical and barrier properties useful for valuable applications in the food field.
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