Percentage of deacetylation, different acid compounds, and molecular weight influence the solubility, physical, or antimicrobial properties and film thickness of CS. This polymer is soluble in acidic to neutral solutions and shows positive charges due the protonation of its amino groups, whose pKa value is equal to 6.5. CS is a cationic linear polysaccharide composed of β-(1–4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit), derived from the structural components of arthropod exoskeletons or the cell walls of fungi and yeast. Chitosan: Structure, Functional Properties, and Methods of ApplicationĬS is a deacetylated derivate of chitin whose is the second-most abundant renewable biopolymer in nature. All these aspects are broadly reviewed in this review, with particular emphasis on the literature published during the last five years ( Table S1).Ģ. This review is carried out with the aim to provide comprehensive and updated overview of the state of the art related to the effects of CS-based ECs on antioxidant systems, enzymatic and non-enzymatic, evaluating the induced oxidative damages during storage in fresh and ready-to-eat fruits. ĬS based coatings are considered the best edible and biologically safe preservative coatings for different fruits and vegetables, owing to their lack of toxicity, biodegradability, and antimicrobial action. Pullulan, chitosan (CS), carrageenan, starch, alginate, cellulose, pectin, gellan gum, and xanthan gum are the main polysaccharide-based materials used for ECs. Furthermore, their mechanical and structural properties are due to a hydrophilic hydrogen-bond network with ordered and compact structure. Polysaccharides are renewable biopolymers widely used in ECs applications for their solubility in water, high available and low allergen content. The coating materials are applied by spraying or dipping method on the surface of fruits and vegetables to obtain a protective mono- or bi-layer. Various types of biopolymer matrix, all biodegradable and non-toxic, such as polysaccharides, lipids and proteins are used alone or in blends to develop ECs. Consequently, in coated fruits and vegetables, respiration and transpiration rates and physiological ripening process are slow down, while the qualitative and sensorial traits are enhanced. ECs create a physical protective barrier between the fruit and the environment modifying the permeability to gas exchange, water vapor and the atmosphere around the commodities. ECs should be realized by biodegradable and biocompatible materials recognized as “generally regarded as safe” (GRAS) or as food additives by the Food and Drug Administration and the European Union, respectively. Edible coatings (ECs) represent an eco-friendly, low-cost, promising and effective method that create a thin layers of edible substances on fruit surfaces, exhibiting film-forming properties to prevent deterioration during postharvest life of whole and fresh-cut fruits and vegetables. Ī challenge to the food industries is to develop and implement several innovative methods and technologies in order to control and reduce fruits and vegetables postharvest losses. Fruits and vegetables are very perishable commodities and their losses and wastes occur at various stages of food supply chain. All these aspects are broadly reviewed in this review, with particular emphasis on the literature published during the last five years.įruits and vegetables, being an excellent source of nutrients, play an important role in human nutrition and high fruit and vegetable intakes in diet are also associated with a decreased incidence of a variety of chronic diseases. This review is carried out with the aim to provide comprehensive and updated over-view of the state of the art related to the effects of chitosan-based edible coatings on anti-oxidant systems, enzymatic and non-enzymatic, evaluating the induced oxidative damages during storage in whole and ready-to-eat fruits. Chitosan-based coatings modulate or control oxidative stress maintaining in different manner the appropriate balance of reactive oxygen species (ROS) in fruit cells, by the interplay of pathways and enzymes involved in ROS production and the scavenging mechanisms which essentially constitute the basic ROS cycle. Chitosan-based edible coatings represent an eco-friendly and biologically safe preservative tool to reduce qualitative decay of fresh and ready-to-eat fruits during post-harvest life due to their lack of toxicity, biodegradability, film-forming properties, and antimicrobial actions.
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