Predominantly produced today by the deacetylation of chitin on an industrial scale, chitosan is found in the exoskeleton of crustaceans and insects, and the cell walls of many fungi and some algae.

Although the main source of chitin is crab, shrimp, crayfish, and shrimp residues, the importance of insect chitosan depends on the role insects play as a sustainable protein source.

Insects are seen as an alternative to traditionally consumed proteins derived predominantly from traditional livestock mainly cows, chickens, and pigs and fish. Chitin and chitosan have interesting physicochemical, biological, and mechanical properties. One such property of chitosan is related to its antimicrobial activity.

There are several studies demonstrating the antimicrobial and antifungal properties of chitosan and many derivatives [ 6 , 7 , 8 , 9 , 10 , 11 ]. Recently, the effect of the physical form of chitosan on its antibacterial activity against pathogenic bacteria was studied.

Researchers examined chitosan coating as an inhibitor of Listeria monocytogenes on vacuum-packed pork fillets and fresh cheese. The antibacterial effect is reported to be generally rapid, eliminating bacteria within a few hours. As for the physical properties of chitosan, these are mainly governed by two factors: deacetylation degree DD and molecular weight MW.

Natural origin, as well as variability in chemical composition, can affect the properties of chitosan and have an impact on its industrial uses.

Some studies have revealed that DD correlates with the antimicrobial activity of chitosan. The effect of chitosan as an antimicrobial in the agriculture and food industry has been studied.

According to these studies, the antimicrobial activity of chitosan depends on several external and internal factors as well as a number of environmental factors. The type of microorganism, physiological state, pH, temperature, ionic strength, metal ions, ethylenediaminetetraacetic acid EDTA , the presence of organic matter, MW, DD, solvent, and concentration are all influencing factors [ 12 ].

Chitosan is a commercial biopolymer produced predominantly from crab and shrimp residues. The physicochemical properties of chitosan affect the functional properties that differ according to crustacean type and preparation methods.

Chitosan has been studied to compare the functionality of commercial products obtained from crustacean and insect chitosan as antimicrobials. The results indicated differences between commercial insect chitosan and crustacean chitosan with regard to their antimicrobial capacity.

Generally speaking, crustacean chitosan with a pH of 5,0 during a hour incubation period displayed a greater antimicrobial capacity than insect chitosan at the same pH. This behavior was seen mostly in Salmonella cases where crustacean chitosan resulted in more than 4 logarithmic decreases, whereas insect chitosan was only bacteriostatic resulting in about a 1 logarithmic decrease.

The similar behavior was noticed for Escherichia coli , despite the smaller differences in antimicrobial influence in Salmonella cases. As noted, some studies have pointed out potential differences between the functions and physical properties of chitosan in different species of crustaceans.

This may be even more pronounced among chitosan obtained from various sources such as crustaceans and insects [ 6 ]. Antimicrobial activity can be adversely affected by pH, and as such pH plays an important role in the antimicrobial capacity of chitosan. Low pH chitosan appears to have more antimicrobial activity than high pH chitosan [ 13 ].

A study was conducted to determine the effect of two different concentrations of chitosan at pH 6,5 and 5,5 on different pathogenic microorganisms, including Salmonella Typhimurium, E. coli , and L. The author concluded that chitosan with a pH of 6.

At pH 5,5; there was inhibition of the microorganisms tested for 24 to 72 hours of storage at 30°C. The researcher concluded that chitosan acts better at pH 5.

Another researcher examined the antibacterial activity of chitosan of different MW at various pH levels pH 4, 4. monocytogenes strains. The results also indicated that, with the exception of two L.

monocytogenes strains, chitosan with a pH of 5 had the greatest bacterial reduction effect during a hour incubation period [ 15 ]. In another study, two pH levels were tested at a concentration of 0. Later an 8-hour incubation, the antibacterial effect was found to be higher at pH 5,0 than pH 6,2 for S.

Typhimurium, but the opposite for E. coli and Listeria monocytogenes , where the antimicrobial effect of chitosan at pH 6. The effect of chitosan at both pH levels seemed to be dependent on the microorganism. Differences were observed in chitosan at both pH levels of acetic acid compared to control.

Chitosan exhibited a pronounced antimicrobial activity at both pH values, particularly on L. Chitosan obtained from both sources, crustaceans and insects, was bacteriostatic or bactericidal for three pathogenic microorganisms at pH 5.

Several hypotheses have been proposed about the antimicrobial function of chitosan. Ionic interactions occcuring between the positive charges of amino groups and negative bacterial surface molecules under acid conditions change the membrane permeability which leads to cellular lysis.

Interaction with necessary nutrients for bacteria could be another mechanism. In contrast, at a higher initial inoculum concentration, 0. Regardless of the inoculum level, any chito-oligosaccharide mixture of 0. coli by at least 3 log cycles.

However, the results regarding the effect of inoculum size are not conclusive because they vary with pH and type of microorganism.

Therefore, it is not possible to predict higher antimicrobial activity at a given inoculum size in all cases [ 16 , 17 ]. Included in the peptidoglycan layer on the cell surface, teichoic acid is vital for the growth of Gram-positive bacteria as well as for cell division. Chitosan and its derivatives can bind to teichoic acid on the surface of Gram-positive bacteria non-covalently.

In addition, the effect of chitosan on teichoic acid has been demonstrated by testing Staphylococcus aureus mutant strains lacking the genes needed for teichoic acid biosynthesis [ 19 ].

Teichoic acid has, interestingly, many functions. It controls activities of enzymes, helps to cope with environmental stress, and manages the cationic concentration in the cell cover by binding to the cell surface and the cell receptor.

The mechanism of antimicrobial effect of chitosan on Gram-positive bacteria is due to electrostatic effect with teichoic acid, resulting in disruption and death of cell [ 18 ].

Two different mechanisms mediate the interactions between chitosan and the outer membrane of Gram-negative bacteria. The first mechanism involves chelating chitosan with various cations when pH is higher than pKa, resulting in a breakdown in the uptake of essential nutrients and a breakdown in cell wall integrity.

The second mechanism involves electrostatic interactions between chitosan and anions associated with lipopolysaccharides in the outer membrane.

Chitosan also creates disruptions in the inner membrane, causing intracellular content to leak. Moreover, chitosan can bind non-covalently to the cell membrane of Gram-negative bacteria, suggesting it plays an important role in antimicrobial activity [ 20 , 21 ]. The difference between Gram-positive and Gram-negative bacteria is more obvious compared to chitosan-resistant fungi and chitosan-sensitive fungi.

However, chitosan is unable to make the cell wall of chitosan-resistant fungi permeable due to its variable fluidity, so it remains on the cell surface and forms a polymer to function as a barrier against oxygen and necessary nutrients, ultimately resulting in cell death. The lowered antimicrobial activity of chitosan was also seen in a Neurospora crassa mutant strain, explaining the lower levels of unsaturated fatty acids relative to the wild-type strain.

Thus, the antibacterial effect of chitosan on fungi is greatly affected by the fluency of the cell membrane and the type of mushrooms [ 18 ]. Chitosan inhibited the growth of Aspergillus flavus and aflatoxin in liquid culture, pre-harvest corn and peanuts, and increased the production of phytoalexin in germinating peanuts.

Chitosan has become the first compound in the list of basic substances approved by the European Union for plant protection in agricultural practices, both for organic agriculture and for integrated pest control Tes. Thus, chitosan can be used as a biodegradable fungicide.

In addition, chitosan shows antiviral activity against plant viruses. It has been demonstrated that chitosan inhibits productive infection caused by bacteriophages. The efficacy of bacteriophage inhibition is directly dependent on the final concentration in the medium.

The main factors by which chitosan suppresses phage infections are phage particle inactivation and inhibition of bacteriophage growth at the cellular level.

Chitosan can be used for induction of phagoresistance in industrial microorganism cultures to prevent unwanted phagolysis caused by inoculum contamination with virulent bacteriophages or spontaneous prophage induction in lysogenic culture [ 22 ].

Chitosan only dissolves in acidic aqueous environment where it becomes polycationic when the pH value is lower than the pKa amount. Polycationic chitosan molecules react with negatively charged cell wall molecules, including proteins, phospholipids, polysaccharides, and fatty acids because of the high intensity of amino groups found on the polymer surface, ultimately causing intracellular materials to leak.

Moreover, the positive charge of chitosan improves at low pH values, increasing the absorption of chitosan at the bacterial cell wall. The protonation of the amino group is related to the degree of polymerization as well as the pH of the environment.

For example, chitosan is more effective against Candida lambica at pH 4 than pH 6 [ 18 ]. At that time, it was also seen as a hemostatic agent. Chitosan has been used in water purification for the last 30 years.

Since then, numerous studies have been conducted to find ways to use these materials. Today, chitosan is known as a dietary supplement for weight loss. In fact, it has been marketed for this purpose in Japan as well as Europe for about 20 years. Chitosan has attracted great attention because of its increasing demand as a highly beneficial biopolymer in recent times.

Chitosan, which is obtained by deacetylation of chitin with sodium hydroxide NaOH , can be extracted from a variety of fungi, insects, and crustaceans. Basically, chitosan is a polymer consisting of randomly distributed units of N-acetyl-D-glucosamine and D-glucosamine with different deacetylation degree, acetylation type, and molecular weight which could be chemically modified to its derivatives.

These derivatives affect antibacterial influence of chitosan and its solubility in acidic solutions. The amino group at the C-6 position differs from chitosan obtained from chitin due to its chemical, physical, and biological functions [ 18 ].

Chitosan is a very useful and attractive biopolymer due to its diverse chemical structure. The wide range of chitosan samples described in different studies is surprising. Moreover, there are various conflicts regarding the use of chitosan in different biological applications [ 26 ].

Speaking of the synthesis of chitosan derivatives, the most beneficial advantage of chitosan is that it can be chemically modified into a wide variety of derivatives.

Due to the presence of a primary alcohol group and an amino group, N, O-modified chitosan, as well as O-modified chitosan, can be modified to N-modified chitosan. The main reason for the synthesis of different chitosan derivatives is to improve certain properties.

Today, chitosan can be modified using two methods: Selective and non-selective modifications. The hydroxyl group is less nucleophilic than the amino group; however, both groups can still interact with electrophiles, including isothiocyanates and acids.

These reactions lead to the selective O-chitosan derivative to be synthesized by a one-point reaction, while the non-selective N, O-chitosan derivative is synthesized. An acidic solution like sulfuric acid H 2 SO 4 can be used in production of the O-chitosan derivative.

The amino group is protonated by using an acidic solution, which makes the alcohol functional group more reactive. On the other hand, the selective chitosan derivative equiped using this method is just limited to electrophiles and can only react with the amino group [ 28 , 29 , 30 ].

Due to its low cost, biocompatibility, absence of toxicity, and biodegradability, chitosan has applications in various fields such as tissue engineering, cosmetics, biomedicine, and biotechnology. Chitosan can be used to clarify agent wastewater and remove dye or metal ions due to its potential to protonate the amino group [ 31 ].

It can widely be used in the food industry as a browning inhibitor in juices, an antioxidant in sausages, a purifying agent in apple juices, and an antimicrobial agent. Chitosan can also be used to deliver transmucosal proteins and peptides thanks to its ability to adhere to the mucosa and open epithelial cell connections.

Finally, it can be used as a carrier of macromolecular drugs. Conventionaly, chitosan has been used in its natural form with some limitations such as low surface area, low porosity, and low solubility at neutral pH.

The functionality of chitosan can be increased by producing different derivatives through various chemical and physical processes [ 18 ].

Today, while preserving the organoleptic and nutritional properties of food products, great importance is attached to microbiological food safety. To accommodate these processes, the food industry must use special packaging materials that protect the quality and safety of food.

Moreover, new generation food packaging materials are expected to have antimicrobial properties which create an environment that delays or completely prevents microbial growth, thus extending the shelf life of food products. Antimicrobial materials can be classified into two broad categories: organic materials and inorganic materials [ 32 , 33 ].

Inorganic substances are stable under severe conditions. However, examples of organic antimicrobial materials include halogenated compounds, quaternary ammonium salts, and phenols.

Also, recent studies have found that natural polymers like chitosan and its derivatives have antibacterial activities. Thus, chitosan is promising substance that can be used in food packaging due to its ability to prevent gas or aroma in dry status and to form an excellent film [ 18 ] and for this purposes chitosan is used in various foods to extend shelf life mentioned in Table 1.

The antibacterial function of chitosan and its derivatives can be affected by different food ingredients. coli to hexadecane via chitosan as a result of disruption of the electrostatic interaction liable for chitosan adsorption to the organism cell surface. Also, the addition of a metal ion lessened the antimicrobial influence of the chitosan derivative against Staphylococcus aureus.

It has also been informed that starch, α-lactalbumin and β-lactoglobulin whey proteins , and sodium chloride NaCl have a negative effect on antibacterial function of chitosan; however, fat had no effect [ 34 , 35 ].

Chitosan is used as a food additive in many countries, including Japan, Korea, and Italy, due to its many properties. Today, customers demand safe and quality food products. The food industry is an area where important applications of chitosan are widely used.

Reducing or preventing the number of chemicals in food is highly demanded in food industry. To meet this growing demand, chitosan can be used as an additive in food products. Chitosan can react with metals and prevent the initiation of lipid oxidation; therefore, it can be used as a secondary antioxidant.

For example, combining chitosan with glucose enhances its antioxidant property, but it does not affect its antibacterial influence against E. coli , S. aureus , Bacillus subtilis , and Pseudomonas. Chitosan can also be bound to other naturally occurring substances such as xylan to improve their antibacterial and antioxidant properties [ 37 , 38 ].

In addition, the low oxygen permeability of chitosan can decrease the contact of food with oxygen, thereby reducing the oxidation rate. Chitosan and its derivatives can be used as a promising substance to extend the shelf life of various food products.

For example, when a chitosan-based substance is used to coat certain food products, it can decrease bread hardness, retrogradation, weight loss, and bacterial development.

The surface of eggs and fruits can be coated with chitosan to create a protective barrier that can decrease respiration and sweating rates, as well as prevent the transfer of gas and moisture from albumin through eggshells. Thus, chitosan can be used to improve the structure and quality of food products as well as prevent microbial growth and color changes [ 18 ].

It is known that cattle act as a native reservoir for the E. coli OH7 agent that causes most foodborne diseases. Unfortunately, the inhibition of E. coli OH7 contamination on meat and meat products has not been successful.

Controlling the contamination of these pathogens is very important during processing level and to reduce the contamination of E. coli OH7 in cattle to an acceptable value. The effect of chitosan on E. coli OH7 infected calves was researched and the results defined that the time of fecal contamination was remarkably decreased in chitosan-treated animals compared to untreated animals.

Also, chitosan administration did not cause any ration profitability or abnormal behavior [ 39 ]. One of the factors affecting the antimicrobial activity of chitosan is the DD. An increase in DD means an increased number of amino groups on chitosan.

As a result, chitosan has an increasing number of protonated amino groups in an acidic condition and is fully soluble in water, which increases the likelihood of interaction between chitosan and negatively charged cell walls of microorganisms. Low MW fractions have little or no activity.

Chitosan with a MW ranging from 10, to , Da will be useful in inhibiting bacterial growth. In addition, chitosan with an average MW of Da, was effective against E. One researcher reported that while D-glucosamine hydrochloride chitosan monomer did not exhibit any growth inhibition against several bacteria, chitosan was effective.

This suggests that the antimicrobial activity of chitosan is not only related to its cationic nature but also its chain length. However, another researcher found that 10, Da chitosan was least effective in bactericidal activities, while , Da chitosan was most effective [ 36 ].

Chitosan is also used as an encapsulation material to improve food processing. Encapsulation is an attractive technology for protecting chemicals to prevent unwanted changes. Encapsulation materials can be formed with one or more compounds, such as chitosan, maltodextrin, acacia gum, hydroxypropyl methylcellulose phthalate gelatin, and starch, which can be used as a mixture or alone, among others.

Chitosan has also attracted attention due to its applications in food and pharmacy. The antimicrobial and antifungal activities of chitosan are some of the most intriguing properties for improving food preservation and reducing the use of chemical preservatives. One study reported the use of chitosan in combination with essential oils, using nanoencapsulation processes, which have the potential to be applied in food industries.

Due to the fact that essential oils such as thymol, eugenol, and carvacrol found in thyme, clove, and thyme essential oils easily degrade in light, air, and high temperatures, nanoencapsulation has recently been developed as an effective technique to protect them from evaporation and oxidation [ 40 ].

The ion binding character of chitosan is another important quality. Chitosan has proven to have the best chelating properties among other natural polymers. Although hydroxyl groups may also be involved in absorption, the amino groups of chitosan are responsible for compound formation, in which nitrogen is a donor of electron pairs.

The mechanism for collaborating the reactive groups with metal ions is very different and can link to the ion pattern, pH, and also the key ingredients of the solution. With regard to food applications of chitosan, information on the selective binding of essential metal ions to chitosan is important for its application as a cholesterol-lowering agent and its more controversial use as a weight loss agent [ 42 ].

Recently, researchers are increasingly interested in active food packaging materials, and there has been more interest in finding materials that provide biological activity to thin films as well as improving their properties.

With the widespread use of non-fragile petroleum-based plastics, environmental pollution has become increasingly apparent. Most countries have placed restrictions on plastics, and there is an increasing demand for biodegradable functional packaging materials.

Among the many natural biopolymers, chitosan has gained increasing attention thanks to its non-toxicity, biodegradability, biocompatibility, antibacterial activity, and excellent film-forming ability. Chitosan is a native cationic linear polysaccharide created of D-glucosamine and N-acetyl-D-glucosamine units prepared by partial deacetylation of chitin.

Chitosan has excellent features that enable it to be used as wound dressing in the medical area, for tissue engineering, and as food packaging in the industrial area [ 8 ]. As a result, chitosan is one of the most important edible films used worldwide, produced by the deacetylation of chitin.

Many native biopolymers can be used to compose edible films; however, among them chitosan attracts the attention for its excellent film-forming activity, flexibility, stability, biocompatibility, non-toxicity, biodegradability, and commercial usability.

Chitosan, which is a traditionally available polysaccharide with the deacetylation of chitin, was generally accepted as safe by FDA United States Food and Drug Administration in and was confirmed for use as a food supplement suitable for human diets [ 7 ].

The most prominent properties of chitosan, as a compound obtained by various methods, can be attributed to its antimicrobial and antioxidant properties. Scientific publications reporting the antimicrobial activity of chitosan are specified in Tables 2 and 3. Considering these properties, the use of chitosan as an edible film to extend the shelf life of foods has been studied by many researchers.

Studies revealing the antibacterial properties of chitosan, accordind to Olatunde et al. Chitosan is a versatile biopolymer that has a variety of commercial applications. However, individual research reports have used chitosans from various sources with varying physicochemical properties.

Hence, the question arises as to how to globally produce chitosans with consistent properties. Each batch of chitosan produced from the same manufacturer may differ in its quality. Functional properties of chitosan vary with molecular weight and degree of deacetylation.

With proper modification of chitosan, its functional properties and biological activities can be further enhanced, and more applications are being developed. Chitosan with different structures shows different biological activities and not all the biological activities are found in one kind of chitosan.

Each special type of bioactive chitosan should be developed for its potential application. Moreover, many studies carried out on chitosan and chitooligosaccharide bioactivity have not provided detailed molecular mechanisms. Hence, it is difficult to explain exactly how these molecules exert their activities.

Therefore, future research should be directed toward understanding their molecular-level details, which may provide insights into the unknown biochemical functions of chitosan. One major drawback of chitosan film is its high sensitivity to humidity, and thus, it may not be appropriate for use when it is in direct contact with moist foods.

More research is needed to develop antimicrobial chitosan films that are less sensitive to humidity. Numerous researches conducted on food applications of chitosans have been done at a small or laboratory scale.

Further research on quality and shelf life of foods, containing or coated with chitosan, should be conducted on scale-up with large volumes typical of commercial conditions.

Chitosan is a polysaccharide-based film applied to the outer surface of foods and is effective in controlling physiological, morphological, and physiochemical changes in foods. Chitosan films can control oxygen and moisture permeability and have antioxidant and antimicrobial effects on food.

The most widely accepted hypotheses about the antimicrobial effect of chitosan are: 1 ionic surface interaction resulting in cell wall leakage; 2 inhibition of mRNA and protein synthesis by the penetration of chitosan into the nuclei of microorganisms; and 3 creating an external barrier, chelating metals and triggering suppression of microbial growth in essential nutrients.

All of these situations are likely to occur at the same time but at different densities. The MW and DD are also important factors in determining such activity. Generally, the lower the MW and DD, the higher the effectiveness in reducing microorganism growth and proliferation.

Despite the many advantages of chitosan, there are also various restrictions related to its use. The most important limitation of chitosan is its low solubility at neutral pH. To compensate for this deficiency, various chemical and physical processes have been used to increase its solubility.

Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Edited by Mohammed Berrada. Open access peer-reviewed chapter Chitosan for Using Food Protection Written By Sadik Büyükyörük. DOWNLOAD FOR FREE Share Cite Cite this chapter There are two ways to cite this chapter:.

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Chapter metrics overview Chapter Downloads View Full Metrics. Impact of this chapter. Keywords Antimicrobial activity chitosan food safety mode of action public health. Lychee fruit The browning is delayed by preventing the increase in polyphenol oxidase activity.

Juices Use of soluble chitosan as a purifier in apple, grape, lemon, and orange juice Fruit juices are purer than bentonite and gelatin, and the acceptance of fruit juices has increased. To control the acidity of carrots and apple juice It was observed to cause a significant decrease in titration acidity.

Apple and pear juice It has also been indicated it prevent enzymatic browning. Pork products It was determined that chitosanglutamate used at 0. Sausage It has been determined that chitosan reduces the use of sodium nitrite in sausage by half ppm without affecting quality and storage stability, and has also been found to reduce the amount of residual nitrite.

Applications in Dairy Products Cheese It has been reported that it inhibits the growth of L. monocytogenes and S. aureus, but does not affect Gram-negative Pseudomonas aeroginosa. Mozzarella It has been determined that when used with the Lysozyme enzyme for film and coating purposes, it inhibits the growth of E.

coli, L. monocytogenes, Pseudomonas fluorescens and yeast and molds and improves shelf life. Coated with chitosan-lysozyme mixture Growth inhibition of L.

monocytogenes, Salmonella enterica, coliforms, yeast and mold, delayed moisture loss and pH changes have been reported. Table 1. The effect of chitosan on some food groups. Study on Chitosan Food Preservatives Technology p. Research Development of Antibacterial Plastic Packaging p.

Optimization of Deposition Conditions for Preparing Silica Films by RF Magnetron Sputtering p. Research Development of Biodegradable Modification of Poly vinyl alcohol Film p. Home Advanced Materials Research Advanced Materials Research Vol.

Study on Chitosan Food Preservatives Technology. Article Preview. Abstract: With the improvement of living standards, the requirement of food quality, nutrition, and freshness have been higher and higher.

Access through your institution. Add to Cart. You might also be interested in these eBooks. View Preview. Advanced Materials Research Volume Cite this paper. Online since:. November Rui Rui Qin , Wen Cai Xu , Dong Li Li , Shi Yong Luo. Chitosan CS , Coating , Food Fresh-Keeping Technology , Fresh-Keeping Mechanism.

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