Applications of Chitosan for Improvement of Quality and Shelf Life of Foods: A Review

Intermolecular interaction and solid state characterization of abietic acid/chitosan solid dispersions possessing antimicrobial and antioxidant properties

The aim of this work was to prepare and characterize solid dispersions of abietic acid (AB) and chitosan (CS) to investigate how formulation of the mixture may help in the battle against microbial colonization in different areas, such as the biomedical field or the food industry. Solid dispersions were characterized by differential scanning calorimetry, infrared spectroscopy, Raman spectroscopy, polarized optical microscopy, zeta potential and size analysis. The data showed that the dispersion/solvent evaporation method formed solid dispersions in which abietic acid was molecularly dispersed in the carrier. A synergistic effect between the two components in terms of antioxidant and antimicrobial properties was found, especially in the formulations obtained with 1/1 AB/CS molar ratio. Interestingly, the aggregation state (amorphous/crystalline) of AB seemed to affect the antimicrobial activity of the formulation, suggesting increased bioactivity when the drug was in the amorphous state. These findings, together with the demonstrated biocompatibility of the formulations, seem to open promising perspectives for a successful application of the developed AB/CS formulations in the biomedical field or in the food industry.

Emerging Chitosan-Based Films for Food Packaging Applications

Recent years have witnessed great developments in biobased polymer packaging films for the serious environmental problems caused by the petroleum-based nonbiodegradable packaging materials. Chitosan is one of the most abundant biopolymers after cellulose. Chitosan-based materials have been widely applied in various fields for their biological and physical properties of biocompatibility, biodegradability, antimicrobial ability, and easy film forming ability. Different chitosan-based films have been fabricated and applied in the field of food packaging. Most of the review papers related to chitosan-based films are focusing on antibacterial food packaging films. Along with the advances in the nanotechnology and polymer science, numerous strategies, for instance direct casting, coating, dipping, layer-by-layer assembly, and extrusion, have been employed to prepare chitosan-based films with multiple functionalities. The emerging food packaging applications of chitosan-based films as antibacterial films, barrier films, and sensing films have achieved great developments. This article comprehensively reviews recent advances in the preparation and application of engineered chitosan-based films in food packaging fields.

Investigation of an elutable N-propylphosphonic acid chitosan derivative composition with a chitosan matrix prepared from carbonic acid solution

Porous chitosan composites using CO₂ dissolution procedure and including water soluble N-propylphosphonic chitosan derivative (p-CHI) were obtained and characterized. In contrast to the control material, composites containing modified chitosan distinguished by a rapid moisture absorption and good adhesion to the skin. The FTIR analysis confirmed the presence of propylphosphonic group in the structure of the polymer. The porosity of the materials was in the range 55-77% and decreased with increasong amount of modified chitosan in materials. Solubility of composites was dependent on the content of p-CHI in scaffolds (40%, 25% and 15%) and reached values 11%, 9% and 6,5%, respectively. The values of other parameters like swelling degree (30g/g) good antioxidant and antimicrobial properties (almost 100% reduction of S.aureus, E.coli and C. albicans growth) and low in vitro cytotoxicity against fibroblasts were highly advantageous for possible biomedical applications of the composites.

Chitosan-coated amyloid fibrils increase adipogenesis of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the potential to revolutionize medicine due to their ability to differentiate into specific lineages for targeted tissue repair. Development of materials and cell culture platforms that improve differentiation of either autologous or allogenic stem cell sources into specific lineages would enhance clinical utilization of MCSs. In this study, nanoscale amyloid fibrils were evaluated as substrate materials to encourage viability, proliferation, multipotency, and differentiation of MSCs. Fibrils assembled from the proteins lysozyme or β-lactoglobulin, with and without chitosan coatings, were deposited on planar mica surfaces. MSCs were cultured and differentiated on fibril-covered surfaces, as well as on unstructured controls and tissue culture plastic. Expression of CD44 and CD90 proteins indicated that multipotency was maintained for all fibrils, and osteogenic differentiation was similarly comparable among all tested materials. MSCs grown for 7days on fibril-covered surfaces favored multicellular spheroid formation and demonstrated a >75% increase in adipogenesis compared to tissue culture plastic controls, although this benefit could only be achieved if MSCs were transferred to TCP for the final differentiation step. The largest spheroids and greatest tendency to undergo adipogenesis was evidenced among MSCs grown on fibrils coated with the positively-charged polysaccharide chitosan, suggesting that spheroid formation is prompted by both topography and cell-surface interactivity and that there is a connection between multicellular spheroid formation and adipogenesis.

Improved quality of a vitamin B12-fortified ‘ready to blend’ fresh-cut mix salad with chitosan

A vitamin B12-fortified (0.25 mg L−1) chitosan (10 g L−1) coating was applied to a ready-to-blend fresh-cut salad including melon, pineapple and carrot, which was stored at 5 ℃ up to nine days. Uncoated samples were used as control while the vitamin B12 effect was compared to non-fortified chitosan-coated samples. Beverages were prepared on blending days 0, 4, 7 and 9 with subsequent storage at 5 ℃ for 0, 24 and 48 h. Physicochemical quality of fresh blended beverages was well preserved throughout storage. The chitosan coating highly reduced epiphytic microflora growth and polyphenoloxidase/peroxidase activities. No relevant variations of total phenolic contents were observed between different fresh blended beverages. However, its total antioxidant capacity reported after blending was lower as storage time of ready-to-blend samples increased. Fortified samples showed a vitamin B12 content of 8.6 µg kg−1 on processing day, ensuring 200 mL of such beverage the recommended daily intake of this vitamin. In conclusion, a ready-to-blend fruit/vegetable mix, fortified with vitamin B12, was developed with a shelf life of nine days at 5 ℃ showing the prepared beverages good quality during subsequent storage for 48 h at 5 ℃.

The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes

The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) molar mass on the interaction with statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been systematically investigated for different PAMAMPS chemical charge densities (15% and 100%) and different ionic strengths. The study of the ionic strength dependence of the binding constant allowed the determination of the total number of released counter-ions during the formation of the PEC, which can be compared to the total number of counter-ions initially condensed on the individual polyelectrolyte partners before the association. Interestingly, this fraction of released counter-ions, which was strongly dependent on the PLL molar mass, was almost independent of the PAMAMPS charge density. These findings are useful to predict the binding constant according to the molar mass and charge density of the polyelectrolyte partners.

Antibacterial Activity of Neat Chitosan Powder and Flakes

This study investigates the antibacterial activity of neat chitosan powder and flakes against three different bacterial species, Escherichia coli, Listeria innocua and Staphylococcus aureus, which are frequent causes of food spoilage. The effect of chitosan concentration and purity, as well as the influence of temperature, ionic strength (salt) and impact of a solid physical support in the medium are examined. Results show that the antibacterial activity of neat chitosan: (i) requires partial solubilisation; (ii) can be promoted by environmental factors such as adequate temperature range, ionic strength and the presence of a solid physical support that may facilitate the attachment of bacteria; (iii) depends on bacterial species, with a sensitivity order of E. coli > L. innocua > S. aureus; and (iv) increases with chitosan concentration, up to a critical point above which this effect decreases. The latter may be due to remaining proteins in chitosan acting as nutrients for bacteria therefore limiting its antibacterial activity. These results on the direct use of chitosan powder and flakes as potential antimicrobial agents for food protection at pH values lower than the chitosan pK_a (6.2-6.7) are promising.

Inactivation Strategies for Clostridium perfringens Spores and Vegetative Cells

Clostridium perfringens is an important pathogen to human and animals and causes a wide array of diseases, including histotoxic and gastrointestinal illnesses. C. perfringens spores are crucial in terms of the pathogenicity of this bacterium because they can survive in a dormant state in the environment and return to being live bacteria when they come in contact with nutrients in food or the human body. Although the strategies to inactivate C. perfringens vegetative cells are effective, the inactivation of C. perfringens spores is still a great challenge. A number of studies have been conducted in the past decade or so toward developing efficient inactivation strategies for C. perfringens spores and vegetative cells, which include physical approaches and the use of chemical preservatives and naturally derived antimicrobial agents. In this review, different inactivation strategies applied to control C. perfringens cells and spores are summarized, and the potential limitations and challenges of these strategies are discussed.

An environmental application of functionalized chitosan: enhancement of the separation of the solid and liquid fractions of digestate from anaerobic digestion

A high molecular weight chitosan was chemically modified to quantitatively incorporate quaternary ammonium groups. Its efficiency was evaluated in the liquid-solid separation for various liquors, and compared with the one of a polyelectrolyte usually used for this utilization. The performance of the liquid-solid separation was estimated through the determination of two parameters measured after the screening- settling of the mixture liquor/flocculating agent: the separation efficiency (EV) and the TS removal efficiency (ETS). Apart for liquor 6, TS removal was always better after an addition of functionalized chitosan. Furthermore, whatever the type of liquor, the distribution was modified by an increased presence of high-size particles when functionalized chitosan was added. Moreover, chitosan addition tended to homogenize the size of the particles, which could facilitate the choice of the liquid-solid separation process. This homogenization was particularly observed for the liquor initially highly dispersed in size, i.e. liquors 1, 4, 6 and 8.

Difference between Chitosan Hydrogels via Alkaline and Acidic Solvent Systems

Chitosan (CS) has generated considerable interest for its desirable properties and wide applications. Hydrogel has been proven to be a major and vital form in the applications of CS materials. Among various types of CS hydrogels, physical cross-linked CS hydrogels are popular, because they avoided the potential toxicity and sacrifice of intrinsic properties caused by cross-linking or reinforcements. Alkaline solvent system and acidic solvent system are two important solvent systems for the preparation of physical cross-linked CS hydrogels, and also lay the foundations of CS hydrogel-based materials in many aspects. As members of physical cross-linked CS hydrogels, gel material via alkaline solvent system showed significant differences from that via acidic solvent system, but the reasons behind are still unexplored. In the present work, we studied the difference between CS hydrogel via alkaline system and acidic system, in terms of gelation process, hydrogel structure and mechanical property. In-situ/pseudo in-situ studies were carried out, including fluorescent imaging of gelation process, which provided dynamic visualization. Finally, the reasons behind the differences were explained, accompanied by the discussion about design strategy based on gelation behavior of the two systems.

Microbial chitosan as a biopreservative for fish sausages

Processed fish products are worthy sources to supply man with his main nutritional needs, but they are extremely susceptible to quality loss during storage. Microbial (fungal) chitosan is a bioactive polymer that has numerous applications in health promoting fields. Fungal chitosan was extracted from the grown mycelia of Aspergillus brasiliensis (niger) to investigate its potential role as antimicrobial, preservative and quality improvement agent, in processed fish sausages from Nile tilapia (Oreochromis niloticus). The produced chitosan had a molecular weight of 29kDa, deacetylation degree of 91% and solubility of 99% in acetic acid solution. Fish sausages supplementation with 1.5% chitosan resulted in sharp reductions of microbial load (Total aerobic microorganisms, coliforms, yeast & molds, E. coli, Enterobacteriaceae and Staphylococcus aureus) during cold storage, at 4°C for 28days. Sensory attributes were notably enhanced in stored chitosan-supplemented sausages, especially the odor and taste characteristics. Captured micrographs, of exposed S. aureus to chitosan, exhibited vigorous morphological alterations after 4h, and complete cell lysis after 8h of exposure period. A. brasiliensis chitosan, however, could be strongly recommended, as a supplement for Nile tilapia fish sausages, to maintain microbiological quality and enhance sensory attributes of the product during storage.

A Chitosan Derivative Containing Both Carboxylic Acid and Quaternary Ammonium Moieties for the Synthesis of Cyclic Carbonates

Chitosan, a renewable feedstock, is modified and used as a catalytic support in the presence of potassium iodide. The system is highly efficient towards the incorporation of carbon dioxide (CO2 ) into epoxides. It demonstrates very good thermal stability and is recyclable more than five times without loss of activity. The optimal reaction conditions were determined using allylglycidyl ether as a model and extended to a wide range of other epoxides. Cyclic carbonates were obtained with very high yield in a few hours under mild conditions (2-7 bar≈0.2-0.7 MPa, 80 °C) and no solvent.

Preparation of antioxidant active films based on chitosan: diffusivity study of α-tocopherol into food simulants

New active films based on chitosan and polycaprolactone blends and containing α-tocopherol were designed for food packaging applications. Mechanical properties, stability against temperature and swelling degree in 50 % ethanol (v/v) were evaluated. Migration kinetics of α-tocopherol from the developed films into butter and food simulants [50 % ethanol (v/v), 95 % ethanol (v/v), and isooctane] at different temperatures were studied. α-Tocopherol was quantified in the food simulants by means of high performance liquid chromatography with diode-array detection at 292 nm. The proposed method exhibited a good sensitivity with a limit of detection of 0.1 mg/L. The kinetics release of α-tocopherol was characterized by determining the partition and the diffusion coefficients by using a mathematical modeling based on Fick's Second Law. The diffusion coefficients obtained ranged between 1.03 × 10(-13) and 2.24 × 10(-12) cm(2)/s for 95 % ethanol (v/v) at 4 and 20 °C, respectively. Developed films maintained the antioxidant activity for more than 20 days.

Recent advances in the understanding of the Aspergillus fumigatus cell wall

Over the past several decades, research on the synthesis and organization of the cell wall polysaccharides of Aspergillus fumigatus has expanded our knowledge of this important fungal structure. Besides protecting the fungus from environmental stresses and maintaining structural integrity of the organism, the cell wall is also the primary site for interaction with host tissues during infection. Cell wall polysaccharides are important ligands for the recognition of fungi by the innate immune system and they can mediate potent immunomodulatory effects. The synthesis of cell wall polysaccharides is a complicated process that requires coordinated regulation of many biosynthetic and metabolic pathways. Continuous synthesis and remodeling of the polysaccharides of the cell wall is essential for the survival of the fungus during development, reproduction, colonization and invasion. As these polysaccharides are absent from the human host, these biosynthetic pathways are attractive targets for antifungal development. In this review, we present recent advances in our understanding of Aspergillus fumigatus cell wall polysaccharides, including the emerging role of cell wall polysaccharides in the host-pathogen interaction.

Potentiating the Heat Inactivation of Escherichia coli O157:H7 in Ground Beef Patties by Natural Antimicrobials

Escherichia coli O157: H7 (EHEC) is a major foodborne pathogen largely transmitted to humans through the consumption of undercooked ground beef. This study investigated the efficacy of two food-grade, plant-derived antimicrobials, namely rutin (RT), and resveratrol (RV) with or without chitosan (CH) in enhancing EHEC inactivation in undercooked hamburger patties. Further, the effect of aforementioned treatments on beef color and lipid oxidation was analyzed. Additionally, the deleterious effects of these antimicrobial treatments on EHEC was determined using scanning electron microscopy (SEM). Ground beef was inoculated with a five-strain mixture of EHEC (7.0 log CFU/g), followed by the addition of RT (0.05%, 0.1% w/w) or RV (0.1, 0.2% w/w) with or without CH (0.01% w/w). The meat was formed into patties (25 g) and stored at 4°C for 5 days. On days 1, 3, and 5, the patties were cooked (65°C, medium rare) and surviving EHEC was enumerated. The effect of these treatments on meat color and lipid oxidation during storage was also determined as per American Meat Science Association guidelines. The study was repeated three times with duplicate samples of each treatment. Both RT and RV enhanced the thermal destruction of EHEC, and reduced the pathogen load by at least 3 log CFU/g compared to control (P < 0.05). The combination of RT or RV with CH was found to be more effective, and reduced EHEC by 5 log CFU/g (P < 0.05). EHEC counts in uncooked patties did not decline during storage for 5 days (P > 0.05). Moreover, patties treated with RV plus CH were more color stable with higher a^∗ values (P < 0.05). SEM results revealed that heat treatment with antimicrobials (CH + RV 0.2%) resulted in complete destruction of EHEC cells and extrusion of intracellular contents. Results suggest that the aforementioned antimicrobials could be used for enhancing the thermal inactivation of EHEC in undercooked patties; however, detailed sensory studies are warranted.

Chitosan/poly-γ-glutamic acid nanoparticles improve the solubility of lutein

The aim of this study was to improve the solubility of lutein through the use of chitosan (CS)/poly-γ-glutamic acid (γ-PGA) nanoencapsulation. In terms of redispersibility, water-soluble chitosan (WsCS)/γ-PGA nanoparticles (NPs) were better than insoluble chitosan (InCS)/γ-PGA NPs. The lutein-loaded WsCS/γ-PGA NP has a spherical form with a size around 200nm and a narrow size distribution (PDI<0.1). Solubility measures showed that nanoencapsulation of lutein into WsCS/γ-PGA NPs resulted in a significant 12-fold higher solubility compared to that of non-nanoencapsulated lutein (p<0.05). The redispersibility index of the lutein-loaded NPs was 1.01, indicating that they were completely reconstituted into aqueous solution as same as original aqueous solution. These results suggest that WsCS/γ-PGA nanoencapsulation can be used to enhance the solubility of lutein and other poorly water-soluble compounds.

Antifungal Edible Coatings for Fresh Citrus Fruit: A Review

According to their origin, major postharvest losses of citrus fruit are caused by weight loss, fungal diseases, physiological disorders, and quarantine pests. Cold storage and postharvest treatments with conventional chemical fungicides, synthetic waxes, or combinations of them are commonly used to minimize postharvest losses. However, the repeated application of these treatments has led to important problems such as health and environmental issues associated with fungicide residues or waxes containing ammoniacal compounds, or the proliferation of resistant pathogenic fungal strains. There is, therefore, an increasing need to find non-polluting alternatives to be used as part of integrated disease management (IDM) programs for preservation of fresh citrus fruit. Among them, the development of novel natural edible films and coatings with antimicrobial properties is a technological challenge for the industry and a very active research field worldwide. Chitosan and other edible coatings formulated by adding antifungal agents to composite emulsions based on polysaccharides or proteins and lipids are reviewed in this article. The most important antifungal ingredients are selected for their ability to control major citrus postharvest diseases like green and blue molds, caused by Penicillium digitatum and Penicillium italicum, respectively, and include low-toxicity or natural chemicals such as food additives, generally recognized as safe (GRAS) compounds, plant extracts, or essential oils, and biological control agents such as some antagonistic strains of yeasts or bacteria.