Edited by: Boqiang Li, Institute of Botany (CAS), China
Reviewed by: Xianghong Meng, Ocean University of China, China; Hongbing Deng, Wuhan University, China
This article was submitted to Food Microbiology, a section of the journal Frontiers in Microbiology
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Chitosan is a natural biopolymer from crab shells that is known for its biocompatibility, biodegradability, and bioactivity. In human medicine, chitosan is used as a stabilizer for active ingredients in tablets, and is popular in slimming diets. Due to its low toxicity, it was the first basic substance approved by the European Union for plant protection (Reg. EU 2014/563), for both organic agriculture and integrated pest management. When applied to plants, chitosan shows triple activity: (i) elicitation of host defenses; (ii) antimicrobial activity; and (iii) film formation on the treated surface. The eliciting activity of chitosan has been studied since the 1990’s, which started with monitoring of enzyme activities linked to defense mechanisms (e.g., chitinase, β-1,3 glucanase, phenylalanine ammonia-lyase) in different fruit (e.g., strawberry, other berries, citrus fruit, table grapes). This continued with investigations with qRT-PCR (Quantitative Real-Time Polymerase Chain Reaction), and more recently, with RNA-Seq. The antimicrobial activity of chitosan against a wide range of plant pathogens has been confirmed through many
Chitosan is the linear polysaccharide of glucosamine and N-acetylglucosamine units joined by β-1,4-glycosidic links and it is obtained by deacetilation of chitin through exposure to NaOH solutions or to the enzyme chitinase. Chitosan and chitin are naturally occurring polymers. For their biocompatibility and biosafety, their applications are widespread in many industries, such as cosmetology, food, biotechnology, pharmacology, medicine, and agriculture (
Number of documents available on Scopus through searches with keywords ‘chitosan’ and ‘postharvest’ in ‘Article title, Abstract, and Keywords’ or in ‘All fields’ published over the last 30 years (accessed on 6 November 2018).
The potential effectiveness of chitosan as a coating for fresh fruit was first proposed by
Postharvest chitosan treatments with other applications for storage decay of temperate fruit.
Fruit | Decay agent | Combination with chitosan | Reference |
---|---|---|---|
Table grapes | Salicylic acid | ||
General decay | Glucose complex | ||
– | |||
– | |||
General decay | – | ||
General decay | Ultraviolet-C | ||
General decay | – | ||
Menta essential oil | |||
Salvia officinalis essential oil | |||
Strawberry | Lavander and thyme essential oil | ||
General decay | Poeny extract | ||
Olive oil processing waste | |||
Total microbial load | Natamycin, nisin, pomegranate, grape seed extract | ||
Total microbial load | Quinoa protein-chitosan and quinoa protein-chitosan-sunflower oil | ||
Total microbial load | Sodium benzoate and potassium sorbate | ||
Zataria multiflora essential oil | |||
Cinnamon leaf essential oil containing oleic acid | |||
General decay | – | ||
General decay | Geraniol and thymol | ||
General decay | Carboxymethyl cellulose, hydroxypropylmethyl cellulose | ||
Nanosized silver-chitosan composite | |||
General decay | Beeswax | ||
– | |||
Pear | General decay | Cellulose nanocrystals | |
General decay | Acylated soy protein isolate and stearic acid | ||
Apple | General decay | Olive waste extracts | |
– | |||
– | |||
– | |||
Calyx senescence | V | ||
Citrus | Silver nanoparticles | ||
Colletotrichum gloeosporioides | |||
Cress and/or pomegranate extracts | |||
Clove oil | |||
Cyclic lipopeptide antibiotics from |
|||
General decay | Carboxymethyl cellulose | ||
Total microbial load | Silver and zinc oxide nanoparticles | ||
Peach | Polyethylene terephthalate punnets containing thyme oil and sealed with chitosan/boehmite nanocomposite lidding films | ||
General decay | γ-ray | ||
– | |||
Sweet cherry | General decay | – | |
– | Hydroxypropyl methylcellulose | ||
Plum | General decay | Ascorbic acid | |
Postharvest chitosan treatments with other applications for storage decay of subtropical fruit.
Fruit | Decay agent | Combination with chitosan | Reference |
---|---|---|---|
Mango | Anthracnose ( |
Spermidine | |
Anthracnose ( |
Lactoperoxidase system incorporated chitosan films | ||
Anthracnose | |||
Anthracnose ( |
Lactoperoxidase system incorporated chitosan films | ||
Anthrcanose | |||
Citrus | Green mold ( |
||
Anthracnose ( |
|||
Avocado | Anthracnose ( |
Thyme oil | |
Tomato | Methyl jasmonate | ||
Essential oil from |
|||
Pomegranate | Lemongrass film | ||
Preharvest chitosan treatments with other applications for storage decay of temperate fruit.
Fruit | Decay | Combination with chitosan | Reference |
---|---|---|---|
Citrus | |||
Peach | General decay | Calcium chloride | |
Jujube fruit | – | ||
Table grapes | Salicylic acid | ||
– | |||
Strawberry | – | ||
– | |||
General decay | – | ||
Sweet cherry | – | ||
Chitosan is known to elicit plant defences against several classes of pathogens, including fungi, viruses, bacteria and phytoplasma (
Proportion of antimicrobial, eliciting, and film-forming properties of chitosan.
Physiological changes that can occur in fresh fruit after chitosan treatment, alone or in combination with other applications.
Fruit | Physiological change | Combination with chitosan | Reference |
---|---|---|---|
Apple | 20 genes involved in defence responses, metabolism, signal transduction, transcription factors, protein biosynthesis, cytoskeleton. | – | |
Total phenolic, flavonoids, antioxidants, pigments, weight loss | Olive waste extract | ||
Peach | Malondialdehyde content | γ-ray | |
Catalase, peroxidase, β-1,3-glucanase and chitinase | – | ||
Total soluble solids, weight loss, ascorbic acid content | Silver and zinc oxide nanoparticles | ||
Color and fruit firmness | Polyethylene terephthalate punnets containing thyme oil and sealed with chitosan/boehmite nanocomposite lidding films | ||
Fruit firmness, weight loss, total soluble solids, total phenolic content, and titratable acidity | Calcium chloride | ||
Plum | Fruit firmness, respiration rate, fruit color, polygalacturonase, superoxide dismutase, peroxidase, catalase, polyphenol oxidase, phenylalanine ammonia lyase and pectin methylesterase activities, superoxide free radicals, malondialdehyde content | Ascorbic acid | |
Sweet cherry | Malondialdehyde content and superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, guaiacol peroxidase lipoxygenase activities | – | |
Strawberry | Over 5000 differently expressed genes | – | |
18 defence genes | – | ||
Fruit color | – | ||
Fruit firmness, anthocyanin and total phenol content | – | ||
Weight loss, titratable acidity, pH, total soluble solids, total phenols, anthocyanin and ascorbic acid content, activity of polygalacturonase, pectin methyl esterase, β-galactosidase and cellulose | Carboxymethyl cellulose, hydroxypropylmethyl cellulose | ||
Weight loss | Lavander and thyme essential oil | ||
Titratable acidity, soluble solids content | – | ||
pH and soluble solids content | Natamycin, nisin, pomegranate, grape seed extract | ||
Weight loss, ascorbic acid | Poeny extract | ||
Weight loss, respiration rate, skin and flesh color, firmness, pH, titratable acidity, soluble solids content, reducing sugars content | Beeswax | ||
Weight loss, firmness, color and total soluble solids content | Sodium benzoate, potassium sorbate | ||
Weight losses, total soluble solids and titratable acidity | Olive waste extract | ||
Allergen-related gene | – | ||
Table grapes | Phenylalanine ammonia lyase, chitinase, and β-1, 3-glucanase, phenolic compounds, respiration rate, weight loss, total soluble solids, titratable acidity | Salicylic acid | |
Total phenols, flavonoids and ascorbic acid content, activities of peroxidase, polyphenoloxidase, polygalacturonase, and xylanase, fruit firmness | – | ||
Fruit color | – | ||
Weight loss, titratable acidity, pH and soluble solids content, resveratrol content | Ultraviolet-C | ||
Weight loss, soluble solids content and titratable acidity | Salvia officinalis essential oil | ||
Firmness, titratable acidity, soluble solids, color, weight loss | Menta essential oil | ||
Total soluble solids, ascorbic acid content, titratable acidity, weight loss, respiration rate, activities of peroxidase and superoxide dismutase | Glucose complex | ||
Titratable acidity, soluble solids, color, firmness | |||
Chitinase activity, quercetin, myricetin, and resveratrol content | – | ||
Citrus | Chitinase and phenylalanine ammonia lyase | – | |
640 differentially expressed genes, many involved in secondary metabolism and hormone metabolism pathways | – | ||
Fruit firmness, weight loss, total soluble solids | Carboxymethyl cellulose | ||
Peroxidase and phenylalanine ammonia-lyase | Cyclic lipopeptide antibiotics from |
||
Contents of chlorophylls and total carotenoids | |||
Phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase | |||
Jujube | Fruit firmness, cellulase, pectinase | – | |
Pear | Total phenolic and flavonoid contents, superoxide dismutase, peroxidase and catalase activities, total antioxidant activity | Calcium chloride | |
Malic acid-metabolising enzymes and related genes expression | Calcium chloride | ||
Mango | Peroxidase (POD) and polyphenol oxidase (PPO) gene expression | – | |
Kiwifruit | Induced gene expression and increased enzymatic activity of catalase, superoxide dismutase and ascorbate peroxidase | – | |
Numerous studies on chitosan inhibitory activities toward numerous microrganisms have been carried out since the first report of almost half a century ago (
Once applied to a plant surface by dipping or spraying, chitosan can form an edible coating, the properties of which (e.g., thickness, viscosity, gas, and water permeability) greatly depend on the acid in which the biopolymer is dissolved. The film-forming properties of chitosan account for 20–30% of the chitosan effectiveness in the control of postharvest decay of fruit and vegetables (Figure
When first used in experimental trials, chitosan needed to be dissolved in an acid (e.g., hydrochloric acid, acetic acid, which were among the most effective ones; see
Some chitosan-based commercial products that are available for control of postharvest diseases of fruit and vegetables.
Product trade name | Company (Country) | Formulation | Active ingredient (%) |
---|---|---|---|
Chito plant | ChiPro GmbH (Bremen, Germany) | Powder | 99.9 |
Chito plant | ChiPro GmbH (Bremen, Germany) | Liquid | 2.5 |
OII-YS | Venture Innovations (Lafayette, LA, United States) | Liquid | 5.8 |
KaitoSol | Advanced Green Nanotechnologies Sdn Bhd (Cambridge, United Kingdom) | Liquid | 12.5 |
Armour-Zen | Botry-Zen Limited (Dunedin, New Zealand) | Liquid | 14.4 |
Biorend | Bioagro S.A. (Chile) | Liquid | 1.25 |
Kiforce | Alba Milagro (Milan, Italy) | Liquid | 6 |
FreshSeal | BASF Corporation (Mount Olive, NJ, United States) | Liquid | 2.5 |
ChitoClear | Primex ehf (Siglufjordur, Iceland) | Powder | 100 |
Bioshield | Seafresh (Bangkok, Thailand) | Powder | 100 |
Biochikol 020 PC | Gumitex (Lowics, Poland) | Liquid | 2 |
Kadozan | Lytone Enterprise, Inc. (Shanghai Branch, China) | Liquid | 2 |
Kendal cops | Valagro (Atessa, Italy) | Liquid | 4 |
Chitosan 87% | Korea Chengcheng Chemical Company (China) | TC (Technical material) | 87 |
Chitosan 2% | Korea Chengcheng Chemical Company (China) | SLX (Soluble concentrate) | 2 |
The effectiveness of chitosan application arises from the integrated combination of its three mechanisms of action. There are increasing consumer requests for fruit and vegetables to be free from residues of synthetic pesticides, such that the rules defined by the public administration have become more limiting in terms of the active ingredients allowed and the maximum residue limits. Also, large stores compete with each other to further reduce these limits, compared to the legal thresholds (
GR proposed the review, collected data on chitosan popularity over time and on commercial products, coordinated the authors, and wrote the article. EF collected papers on effectiveness of chitosan on temperate fruit and on the mechanisms of action in the tables, and helped with the writing. DS collected papers on effectiveness of chitosan on tropical fruit and on the mechanisms of action in the tables, and helped with the writing.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.