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

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 \u201ctop-down\u201d 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

Manufacturing of Food Packaging Based on Nanocellulose : Current Advances and Challenges

Nowadays, environmental pollution due to synthetic polymers represents one of the biggest worldwide challenges. As demonstrated in numerous scientific articles, plant-based nanocellulose (NC) is a biodegradable and nontoxic material whose mechanical, rheological, and gas barrier properties are competitive compared to those of oil-based plastics. However, the sensitivity of NC in humid ambient and lack of thermosealability have proven to be a major obstacle that hinders its breakthrough in various sectors including food packaging. In recent years, attempts have been made in order to provide a hydrophobic character to NC through chemical modifications. In addition, extensive works on nanocellulose applications in food packaging such as coating, layer-by-layer, casting, and electrospinning have been reported. Despite these enormous advances, it can easily be observed that packaging manufacturers have not yet shown a particular interest in terms of applicability and processability of the nanocellulose due to the lack of guidelines and guarantee on the success of their implementation. This review is useful for researchers and packaging manufacturers because it puts emphasis on recent works that have dealt with the nanocellulose applications and focuses on the best strategies to be adopted for swift and sustainable industrial manufacturing scale-up of high-performance bio-based/compostable packaging in replacement of the oil-based counterparts used today

Are Cellulose nanocrystals ‘alien particles’ to human experience?

A wide family of cellulose-based additives are authorized worldwide as fillers and thickening agents in foods, pills and tablets, and microcrystalline cellulose (MCC) is, among these, the most important one. Since MCC manufacturing is similar to the main production route of cellulose nanocrystals (CNCs), it is reasonable to wonder whether the MCC would contain CNCs as minor components. In this Short Communications we provide first results about the occurrence of CNCs in MCC, observed by dynamic light scattering and transmission electron microscopy after serial filtrations of MCC suspensions. The incidence of cellulose nanoparticles has been proved in several different trials in our ongoing works on diverse MCC samples and the nanoparticles isolated showed shape and dimensions similar to those commonly produced by acidic hydrolysis at laboratory level. Therefore, the presence of CNCs in many products is considered as a certainty. The foods and the pharmaceuticals we have been consuming so far, do indeed contain traces of CNCs to such an extent that this wide presence in consumed products should be taken into account when considering possible limitations of the use of these nanoparticles in food contact materials manufacture

The effect of moisture on cellulose nanocrystals intended as a high gas barrier coating on flexible packaging materials

Cellulose nanocrystals (CNCs) exhibit outstanding gas barrier properties, which supports their use as a biobased and biodegradable barrier coating on flexible food packaging materials. As highly hydrophilic biopolymers, however, CNCs have a strong sensitivity to water that can be detrimental to applications with fresh foods and in moist conditions due to the loss of barrier properties. In this work, the oxygen and water vapor permeability of polyethylene terephthalate (PET) films coated with CNCs obtained from cotton linters were measured at varying levels of relative humidity, both in adsorption and desorption, and from these data, the diffusion and solubility coefficients were estimated. Therefore, the characterization of CNCs was aimed at understanding the fundamentals of the water-CNCs interaction and proposing counteractions. The CNCs' moisture absorption and desorption isotherms at 25 \uc2\ub0C were collected in the range of relative humidity 0-97% using different techniques and analyzed through GAB (Guggenheim-Anderson-de Boer) and Oswin models. The effects of moisture on the water status, following the freezable water index, and on the crystal structure of CNCs were investigated by Differential Scanning Calorimetry and by X-ray Powder Diffraction, respectively. These findings point to the opportunity of coupling CNCs with hydrophobic layers in order to boost their capabilities as barrier packaging materials

Carbon dioxide diffusion at different relative humidity through coating of cellulose nanocrystals for food packaging applications

In this paper, the investigation was focused on the CO2permeability through CNCs coating at various RH values, comparing with the O2one, aiming to evaluate the potential usage in all the applications of modified atmosphere packaging for intermediate-low moisture foods where the role of carbon dioxide is essential for shelf life extension. For this purpose, PET \ufb01lms were coated with characterized CNCs, obtained from cotton linters, and the CO2permeance was measured as a function of increasing RH values (from 0% to 80%). After calculating the diffusion and solubility coef\ufb01cients, and estimating the CO2/O2selectivity, the possible evolution of different modified atmospheres has been theoretically calculated. The results obtained, let hypothesize that, in consequence of a very high CO2/O2permeability selectivity, the CNCs coated films can be useful in some modified atmosphere packaging applications, in a range of RH typical of many medium-high RH food products