EFFECTIVE REPLACEMENT IN FOOD PACKAGING OF OIL-BASED OXYGEN-BARRIER POLYMERS (EVOH, PVDC), WITH BIO-COMPOSITES CONTAINING CELLULOSE NANOCRYSTALS (CNCS) EXTRACTED FROM WASTE AND BIOMASSES
Creators: name: FOTIE, GHISLAIN
Publisher: name: Universit� degli Studi di Milano
Year: 2019

description: With increasing pollution and global warming of the environment, a wide spectrum of engineering technologies has emerged in food packaging to develop innovative materials with less carbon dioxide release and Green House emissions. Nowadays, an ideal food packaging must meet all the requirements of food safety and comply with environmental concerns concomitantly. One of the strategies to implement a food package that encompasses all consumer needs is to resort to eco-friendly laminates that combine several layers of materials with different functions in terms of gas/oil/water barrier and mechanical properties. The PhD research was focused on the replacement of currently used EVOH conventional gas barrier laminates with bio-based laminates containing cellulose nanocrystals (CNCs) for shelf-life extension of sensitive-oxidation foods products. Chemico-physically, cellulose is a microfibrillated structure, the most abundant biopolymer, made of millions of beta 1-4 glucose linked by glycosidic bonds; its hierarchical organization denotes from the crystalline and amorphous regions containing chains of glucose firmly hold together side-by-side by hydrogen bonds providing high tensile strength. CNCs are generally obtained by a chemical process called ?top-down? either by acidic or oxidative hydrolysis of the amorphous part of cellulose. CNCs are biodegradable tiny particles whose at least one dimension is smaller than or equal to 100 nm. Actually, CNCs-coated polymers exhibit unique and extraordinary barrier properties to gases. However, since most biodegradable materials are hydrophilic by nature, CNCs tend to integrate water in wet environment which then allows the gases to pass through the coated polymers even abruptly. That phenomenon of water sensibility of CNCs was investigated in-depth during the first stage of the research and two solutions were considered plausible to alleviate that drawback, that of chemically modifying the CNCs surface for making them more hydrophobic or/and that of laminating the CNCs between two water-repellent plastic films to protect them from the humid surrounding. Standard (unmodified) and esterified (modified) CNCs were produced and characterizedto assess their functional groups, crystallinity index, apparent hydrodynamic diameter and size and hydrophilic behavior. Subsequently, plastic films were coated with standard and modified CNCs and characterized by the contact angle, Z-potential, gases permeability (Water vapor, O2, CO2). Coated-CNCs plastic films were then laminated with solvent-based polyurethanic adhesive and characterized by delamination test and gas permeability at 50% and 80% RH to evaluate the effectiveness of the lamination in the protection of CNCs coatings from the wet environment. Between 90% and 1200% improvement of gas barrier was achieved after the lamination.More importantly, the chemical modification of cellulose nanocrystals combined with the lamination resulted to be the best strategy to overcome the water sensitivity of CNCs in wet environment. Finally, a comparative food shelf-life assessment by using both synthetic (EVOH) and bio-based (CNCs) barriers laminates were successfully performed on grated cheese and ground coffee. The results obtained confirmed with certainty that CNCs implementation as a replacement of petroleum-based gas barrier is effective and that will contribute to develop more advanced and sustainable food packaging able to reduce the dependency on synthetic polymers and promoting a circular economy.