Biopolymer based edible films and coatings
An edible coating is a thin layer of edible material formed as a coating on a food product, while an edible film is a preformed, thin layer, made of edible material, which once formed can be placed on or between food components (McHugh, 2000). Some of their functions are to protect the product from mechanical damage, physical, chemical and microbiological activities. Their use in food applications and especially highly perishable products such as horticultural ones, is based on some particular properties such as cost, availability, functional attributes, mechanical properties (flexibility, tension), optical properties (brightness and opacity), the barrier effect against gases flow, structural resistance to water and microorganisms and sensory acceptability (Falguera et al., 2011).
Edible films are usually classified according to their structural material. In this way, films are based on proteins, lipids, polysaccharides or their composites. For example, a composite film may consist of lipids and hydrocolloids combined to form a bilayer or a cluster (Krochta et al., 1994). In some recent studies the production of edible and biodegradable films by combining various polysaccharides, proteins and lipids is considered with the aim of taking advantage of the properties of each compound and the synergy between them. The mechanical and barrier properties of these films not only depend on the compounds used in the polymer matrix, but also on their compatibility, table 2 (Altenhofen et al., 2009).
Table 2 summarizes the main compounds used in edible films and coatings structural matrices. The optimization of edible films composition is one of the most important steps of the research in this field, since they must be formulated according to the properties of the fruits and vegetables to which they have to be applied (Rojas-Grau et al., 2009a). Thus, it is very important to characterize and test different films for fresh and minimally processed food, since each one of them has different quality attributes to be maintained and enhanced during the storage time. Carboxymethylcellulose, casein (Ponce et al., 2008) and its derivatives (Fabra et al., 2009), locust bean gum, guar gum, ethyl cellulose (Shrestha et al., 2003), gelatin supplemented with glycerol, sorbitol and sucrose as plasticizers (Sobral et al., 2001), composite edible films of gelatin casein cross-linked with transglutaminase (Chambi & Grosso, 2006), pectin (Maftoonazad et al., 2007), cassava starch with natural antimicrobial compounds (Kechichian et al., 2010), pre-gelatinized standard maize starch (Pagella et al., 2002), wheat gluten (Tanada et al., 2005) and mixtures of sodium alginate and pectin, with the addition of CaCl2 as a crosslinker material affecting mechanical properties, water solubility, moisture content, film thickness and its ability to contain calcium (Altenhofen et al., 2009).
FUNCTIONALIZATION OF EDIBLE FILMS
To broaden the range of potential applications where food packaging could be used, researchers are increasingly investigating additional functionalization of edible films and coatings by incorporating a variety of active food additives including antioxidants and antimicrobials.
Natural Antioxidants: Chemistry and Sources
Many different chemical compounds have shown some antioxidant activity through different mechanisms of action. According to Laguerre et al. (2007), these mechanisms result in antioxidant activity of a particular compound, such as UV filtration, singlet oxygen deactivation, peroxidant enzyme inhibition, chelation of transition metals, enzymatic detoxification of reactive oxygen species, and their stabilization through hydrogen radical transfer.
Numerous studies have reported the synergistic effects found in antioxidant mixtures (Eberhardt et al., 2000). Indeed, combinations of antioxidants may be more effective at reducing reactive oxygen species than pure compounds, especially if the mixture includes both water-soluble and lipid-soluble antioxidants. If this is the case, the mixture will be capable of quenching free radicals in both aqueous and lipid phases (Chen & Tappel, 1996). The application of antioxidants (pure, mixtures and extracts) to food products is described in the following section. The synergistic effect in the antioxidant mixtures is a common phenomenon that takes place in the final products.
Patents on the use of antioxidant
The number of patents on the application of antioxidants to food products has progressively increased over the last few years. Fukumoto et al. (2007) invented an antioxidant material containing flavonoid aglycon (derived from lemons, limes or sudachis) and vitamin C, a combination in which a synergistic effect is observed. This extract would be added to food products or beverages. Tan et al. (2010) reported the invention of a method for extracting the Effect of packaging on light-induced changes in packed foods antioxidant compounds (phenolics and flavonoids) from the palm tree. These compounds are potent antioxidants to be applied in foods and edible oils. Ahotupa et al. (2006) claimed a food product containing a phenolic compound (hydroxymatairesinol), and found that the administration of this could increase the level of enterolactone, thereby causing cancer prevention.
Meat and Fish Products
Meat, poultry and fish products are very prone to lipid oxidation both because of their high content in unsaturated fatty acids and also due to intrinsic factors to processing and storage conditions. In these products, oxidative reactions can lead to undesirable changes in taste, flavor, and color. The addition of antioxidants can reduce the rate of lipid oxidation and hydrolysis by sequestering and stabilizing free radicals. In this sense, Montenegro (2009) optimized a natural antioxidant composition prepared from phenolic extracts of monofloral honey that prevents the oxidation of meat products, especially poultry. The honey extract contained gallic acid, rutin, ferulic acid, salicylic acid, naringenin, kaempferol and a pH of 4.2-5.0. Kolar et al. (2009) patented a natural mixture for the antioxidative protection of fats and foodstuffs containing fats, such as fish, fresh meat, fresh spiced meat, fresh and cooked sausages, salami, dry cured and cooked cured products, and pastrami. The mixture was prepared with an extract of at least one plant selected from the Labiatae family and green tea extract and comprises carnosic acid, rosmarinic acid, and epigallocatechingallate. Fellenberg Plaza et al. (2008) formulated a liquid extract from soapbark tree comprising 1.4-5.4% total phenols. The extract was applied to marinated chicken leg and chicken breast. Results showed that the greater concentration of polyphenols in this extract showed a prooxidant effect after 2 days of refrigeration. Sandoval et al. (2006) succeeded in preventing the discoloration of fresh beef slices, which were vacuum packed and refrigerated, by means of the injection of a vegetable protein composition containing antioxidants (alkali metal salt of isoascorbic acid). Gaynor et al. (2004) incorporated ascorbate or erythrobate as antioxidants in the formulation of emulsified casings prepared with cellulose and nisin and applied to meat products (e.g. frankfurter).
Table of contents :
I. Introduction et objectifs de l’étude
II. Synthèse bibliographique
II.1. Food packaging development
II.2. Biopolymer based edible films and coatings
II.3. Functionalization of edible films
II.4. Application of antioxidant films and coatings on food products
II.5. Effect of packaging on light-induced changes in pack foods
III. Matériel et Méthodes
III.2.1. HPLC analysis
III.2.2. Mass spectrometric conditions
III.2.3. Preparation of HPMC films
III.2.4. Preparation of antioxidant-HPMC composite solutions
III.2.5. Fabrication of antioxidant films
III.2.6. Film conditioning for photo-aging
III.3. HPMC film characterization
III.3.1. Film thickness measurement
III.3.2. Film color measurements
III.3.3. Light transparency
III.3.4. Mechanical properties
III.3.5. Water vapor permeability
III.3.6. Oxygen permeability
III.3.7. Water sorption isotherms
III.3.8. Differential scanning calorimetry analysis
III.3.9. Scanning electron microscopy (SEM)
III.4. Films application on salmon oil
III.4.1. Determination of total phenolic contents
III.4.2. Release of antioxidant agents from films
III.4.3. Estimation of Diffusion and Partition coefficient
III.4.4. ABTS radicals scavenging activity
III.4.5. FTIR analysis of antioxidant films
III.5. Salmon oil quality parameters
III.5.1. Oil color measurement
III.5.2. Headspace oxygen uptake
III.5.3. Conjugated dienes determination of salmon oil
III.5.4. Fatty acid composition of salmon oil
III.5.5. FTIR analysis of salmon oil
IV. Résultats et Discussion
Chapitre IV.1: Contrôle de la photo-oxydation de l’huile de saumon au cours du stockage dans un film d’HPMC : influence de la couleur du film
Chapitre IV.2 : Fabrication et caractérisation physico-chimique de films d’HPMC fonctionnalisés par des extraits de plantes commerciaux : influence de la lumière et de la composition du film
Chapitre IV.3 : Activité antioxydante et photo-vieillissement des films d’HPMC fonctionnalisés avec des extraits naturels de plantes
Chapitre IV.4 : Cinétiques de libration et stabilité de l’activité antioxydante de composes phénoliques naturels incorporés dans des films de biopolymère
Chapitre IV.5 : Effet de la couleur des films d’HPMC–anthocyanines et de leur perméabilité à l’oxygène sur la conservation de l’huile de saumon
V. Conclusion et perspectives
VI. Publications et communications scientifique
VII. References bibliographiques