Chitosan as Antimicrobial Agent: Applications and Mode of Action

Chitin is the second most abundant natural biopolymer after cellulose. The chemical structure of chitin is similar to that of cellulose with 2-acetamido-2-deoxy-β- d -glucose (NAG) monomers attached via β(14) linkages. Chitosan is the deacetylated (to varying degrees) form of chitin, which, unlike chitin, is soluble in acidic solutions. Application of chitinous products in foods and pharmaceuticals as well as processing aids has received considerable attention in recent years as exotic synthetic compounds are losing their appeal. This review summarizes some of the important developments related to food applications of chitin, chitosan and their derivatives.

Food applications of chitin and chitosans

Perspectives for chitosan based antimicrobial films in food applications

Chitin and its deacetylated derivative chitosan are natural polymers composed of randomly distributed � -(1-4)- linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitin is insoluble in aqueous media while chitosan is soluble in acidic conditions due to the free protonable amino groups present in the D-glucosamine units. Due to their natural origin, both chitin and chitosan can not be defined as a unique chemical structure but as a fam- ily of polymers which present a high variability in their chemical and physical properties. This variability is related not only to the origin of the samples but also to their method of preparation. Chitin and chitosan are used in fields as different as food, biomedicine and agriculture, among others. The success of chitin and chitosan in each of these specific applica- tions is directly related to deep research into their physicochemical properties. In recent years, several reviews covering different aspects of the applications of chitin and chitosan have been published. However, these reviews have not taken into account the key role of the physicochemical properties of chitin and chitosan in their possible applications. The aim of this review is to highlight the relationship between the physicochemical properties of the polymers and their behaviour. A functional characterization of chitin and chitosan regarding some biological properties and some specific applications (drug delivery, tissue engineering, functional food, food preservative, biocatalyst immobilization, wastewater treatment, molecular imprinting and metal nanocomposites) is presented. The molecular mechanism of the biological properties such as biocompatibility, mucoadhesion, permeation enhancing effect, anticholesterolemic, and antimicrobial has been up- dated.

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Functional Characterization of Chitin and Chitosan

▪ Abstract Losses from postharvest fruit diseases range from 1 to 20 percent in the United States, depending on the commodity. The application of fungicides to fruits after harvest to reduce decay has been increasingly curtailed by the development of pathogen resistance to many key fungicides, the lack of replacement fungicides, negative public perception regarding the safety of pesticides and consequent restrictions on fungicide use. Biological control of postharvest diseases (BCPD) has emerged as an effective alternative. Because wound-invading necrotrophic pathogens are vulnerable to biocontrol, antagonists can be applied directly to the targeted area (fruit wounds), and a single application using existing delivery systems (drenches, line sprayers, on-line dips) can significantly reduce fruit decays. The pioneering biocontrol products BioSave and Aspire were registered by EPA in 1995 for control of postharvest rots of pome and citrus fruit, respectively, and are commercially available. The limitations ...

Biological control of postharvest diseases of fruits.

The effect of chitosan coating (1.0 and 1.5% w/v) in controlling decay of strawberries at 13°C was investigated as compared to a fungicide, iprodione (Rovral®). Chitosan coating significantly reduced decay of berries (P ≤ 0.05) compared to the control. There was no significant difference between chitosan and fungicide treatments up to 21 days storage. Thereafter, Rovral®-treated berries decayed at a higher rate than chitosan-coated berries. Chitosan-coated berries stored at 4°C were firmer, higher in titratable acidity, and synthesized anthocyanin at a slower rate than Rovral®-treated or nontreated berries. Chitosan coating decreased respiration rate of the berries with a greater effect at higher concentration.

Chitosan Coating Effect on Storability and Quality of Fresh Strawberries

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/Postharvest%20Biology%20and%20Technology/Vol19.Issue3.Jul2000/1695.pdf

Control of postharvest decay of apple fruit by Aureobasidium pullulans and induction of defense responses

The effect of chitosan on respiration, ethylene production, and quality attributes of tomato (Lycopersicon esculentum Mill.) fruit stored at 20C was investigated. Coating the fruit with chitosan solutions reduced the respiration rate and ethylene production, with greater effect at 2% than 1% chitosan. Coating increased the internal CO 2 and decreased the internal O 2 levels of the tomatoes. Chitosan-coated tomatoes were firmer, higher in titratable acidity, less decayed, and exhibited less red pigmentation than the control fruit at the end of storage (...)

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Chitosan coating to extend the storage life of tomatoes

Antifungal activity of chitosan on post-harvest pathogens: induction of morphological and cytological alterations in Rhizopus stolonifer

The effect of chitosan coating (1.0 and 1.5% w/v) on the storability of bell pepper and cucumber fruits stored at 13 and 20C (RH 85%) was determined by monitoring the weight loss, respiration and quality: Chitosan coating markedly reduced the weight loss in both bell pepper and cucumber at both temperatures. Increasing the concentration of chitosan from 1.0 to 1.5% (w/v) resulted in a significantly greater weight retention in both fruits. In addition, coating cucumber and bell pepper with chitosan reduced the respiration rate, loss of color, wilting and fungal infection. the mechanism by which chitosan coating delayed senescence in bell pepper and cucumber is most likely due to its ability to alleviate water stress.

Ahmed El Ghaouth

Papers

Chitosan Coating Effect on Storability and Quality of Fresh Strawberries

Control of postharvest decay of apple fruit by Aureobasidium pullulans and induction of defense responses

Chitosan coating to extend the storage life of tomatoes

Antifungal activity of chitosan on post-harvest pathogens: induction of morphological and cytological alterations in Rhizopus stolonifer

USE of CHITOSAN COATING to REDUCE WATER LOSS and MAINTAIN QUALITY of CUCUMBER and BELL PEPPER FRUITS