Antifungal activity of chitosan and its application to control post‐harvest quality and fungal rotting of Tankan citrus fruit (Citrus tankan Hayata)

In this study, the antifungal activity of chitosan A (MW = 92.1 kDa) and B (MW = 357.3 kDa), with 94.2% N‐deacetylation were examined at various concentrations against fungi including Penicillium digitatum, Penicillium italicum, Botrydiplodia lecanidion and Botrytis cinerea. The effectiveness of these chitosans to control the post‐harvest quality of Tankan fruit, a popular sub‐tropical citrus fruit, was investigated. It was found that chitosan, depending on type and concentration, caused 25.0–90.5% growth inhibition on test organisms after 5 days of cultivation at 24 °C. Chitosan treatment significantly reduced (P < 0.05) the percentage decay of Tankan fruit during storage at 24 °C. After 42 days of storage at 13 °C, chitosan‐coated Tankan fruits were firmer, exhibited less decay and weight loss, and showed higher titratable acidity, ascorbic acid, and total soluble solids than the control fruit. Weight loss of Tankan fruits decreased as the concentration of chitosan was increased. On the other hand, chitosan A, regardless of concentration tested, was found to be more effective in retaining the firmness, titratable acidity and water content, total solid content and ascorbic acid content of Tankan fruits than chitosan B. Copyright © 2006 Society of Chemical Industry     

Cover Caption

October Online cover : Micrographs of nanosized silver‐fungal chitosan composite antifungal action against Botrytis cinerea after different incubation periods, from “Botryticidal Activity of Nanosized Silver‐Chitosan Composite and Its Application for the Control of Gray Mold in Strawberry” by Shaaban H. Moussa, Ahmed A. Tayel, Abdullah S. Alsohim, and Reda R. Abdallah; p M1591     

A COMBINATION OF HEAT TREATMENT AND CHITOSAN COATING DELAYS RIPENING AND REDUCES DECAY IN “GALA” APPLE FRUIT

ABSTRACT

Apples (Malus domestica Borkh. cv. Gala) were heat‐treated at 38C for 4 days (heat treatment [HT]) before or after coated with 1% chitosan (CTS). Following treatment, apples were stored at 0C for 8 weeks and 20C for 7 days as shelf life. The effectiveness of the combined treatments on the ripeness, quality and decay development caused by Penicillium expansum and Botrytis cinerea was evaluated. Severe heat damage was observed on the fruits heat‐treated after CTS coating (CTS + HT), appeared as external decay and internal brown after treatment. However, no damage on fruits heated before CTS coating (HT + CTS) during the whole storage. Besides the completely control of blue mold and gray mold on artificially inoculated fruits during storage, the HT + CTS treated fruit showed the lowest respiration rate, ethylene evolution, malondialdehyde and membrane leakage, and the highest firmness and consumer acceptance among the treatments. At the same time, this combined treatment could inhibit the lost of green color, titratable acidity and weight loss compared with HT alone.

PRACTICAL APPLICATIONS

“Gala” apple fruits become more popular in the world because of its high productivity and good quality. Hot air treatment alone has been used to delay ripening of Gala but caused the loss of peel green, titratable acidity and weight. This work investigated the effects of hot air treatment combined with chitosan (CTS) coating on the ripening, quality and decay development for Gala apple fruits. Compared with fruits heat‐treat alone, fruits heat‐treated before CTS coating (heat treatment + CTS) preserved original peel color, maintained titratable acidity and weight, completely control decay development and showed the highest consumer acceptance after storage. The information obtained from this study suggested that this combined treatment may be a suitable method for the commercial application on Gala apple fruits.     

Ozone Storage Effects on Anthocyanin Content and Fungal Growth in Blackberries

Ozone exposure was assessed for storage of thornless blackberries which are prone to fungal decay. Blackberries were harvested and stored for 12 days at 2°C in 0.0, 0.1, and 0.3 ppm ozone. Berries were evaluated for fungal decay, anthocyanins, color and peroxidase (POD) activity. Ozone storage suppressed fungal development for 12 days, while 20% of control fruits showed decay. The main mold was Botrytis cinerea. Ozone storage did not cause observable injury or defects. By 12 days, anthocyanin content of juice was similar to initial levels for all treatments. Surface color was better retained in 0.1 and 0.3 ppm-stored berries by 5 days and in 0.3 ppm berries by 12 days, by hue angle values. POD was greater in controls and 0.1 ppm samples, and was lowest in 0.3 ppm fruits by 12 days. Ozone storage resulted in market quality extension.     

Chitosan Controls Postharvest Decay and Elicits Defense Response in Kiwifruit

Chitosan is an eco-friendly alternative to synthetic fungicides for managing postharvest decay of fruits and vegetables. The ability of chitosan to enhance resistance to postharvest gray (Botrytis cinerea) and blue mold (Penicillium expansum) in kiwifruit was investigated. The gene expression and activity of antioxidant enzymes, and total phenolic compounds were determined. Results showed that chitosan at 5 g/L significantly inhibited gray and blue mold in kiwifruit stored at 25 and 4 °C. Chitosan significantly induced the gene expression of catalase, superoxide dismutase, and ascorbate peroxidase, as well as increased the enzyme activity. Moreover, chitosan markedly increased the content of total phenolic compounds in kiwifruit. Importantly, chitosan also exhibited beneficial effects on fruit quality. Taken together, the ability of chitosan to reduce mold in stored kiwifruit may be associated with the elicitation of host defense response. These results have practical implications for the application of chitosan to reduce postharvest losses.     

In vivo and in vitro antifungal effect of fungal chitosan nanocomposite edible coating against strawberry phytopathogenic fungi

This study compared the effectiveness of fungal chitosan nanocomposite, chitosan gel and chitosan nanoparticles against strawberry phytopathogenic fungi (Botrytis cinerea; Rhizopus stolonifer and Aspergillus niger). Nanoparticles were prepared by ionic gelation method and characterised by dynamic light scattering and scanning electron microscopy. The influence of the edible coatings on fungal growth was analysed in vitro and in vivo The fungal chitosan nanoparticles presented an average size = 331.1 nm (±7.21) with a narrow size distribution (PDI = 0.377) and a zeta potential = +34 mV. The edible coating made by the nanocomposite exhibited important changes in fungal morphology, and the best control of the growth of the assayed fungal strains in artificially infected strawberries. Therefore, nanotechnology brought some benefits to the conventional chitosan gel edible coating, improving its antifungal activity and forming a new eco-friendly coating.     

Effects of chitosan-oil coating on blue mold disease and quality attributes of jujube fruits

The effects of chitosan coating enriched with cinnamon oil on blue mold disease and quality attributes were investigated. In the in vitro experiment, the results demonstrated that the antifungal activity against P. citrinum improved with increasing concentration of chitosan or cinnamon oil. In the in vivo study, chitosan-oil treatments significantly reduced fungal decay caused by P. citrinum and all compounds with cinnamon oil at 2.0% showed complete control of the growth of P. citrinum on wound-inoculated fruits. High chitosan-oil concentrations correlated with low disease incidence regardless of storage temperature. Treatments of chitosan-oil coating also inhibited the activity of polyphenol oxidase and maintained vitamin C and phenolic compounds in wounded jujube fruits. Results suggested that the effect of chitosan coating (1.0%) enriched with cinnamon oil (0.75%) on blue mold in jujube fruits may be associated with fungitoxic properties against the pathogen and the elicitation of biochemical defense responses in fruits.     

Essential oils to control Botrytis cinerea in vitro and in vivo on plum fruits

BACKGROUND: The consequence of misusing chemical biocides in controlling pests and diseases has drawn the attention of policy makers to the development of methods potentially available in nature for this purpose. In the present study the inhibitory effects of black caraway, fennel and peppermint essential oils against Botrytis cinerea were tested at various concentrations in vitro and in vivo. RESULTS: The in vitro results showed that the growth of B. cinerea was completely inhibited by the application of black caraway and fennel oils at concentrations of 400 and 600 µL L^?1 respectively. The in vivo results indicated that black caraway, fennel and peppermint oils at all applied concentrations inhibited B. cinerea growth on plum fruits compared with the control. In addition, all three oils at higher concentrations showed positive effects on fruit quality characteristics such as titrable acidity, total soluble solids, carbohydrate content, pH and weight loss percentage. Thus the oils inhibited the infection of plum fruits by B. cinerea and increased their storage life. CONCLUSION: This research confirms the antifungal effects of black caraway, fennel and peppermint essential oils both in vitro and in vivo on plum fruits postharvest. Therefore these essential oils could be an alternative to chemicals to control postharvest phytopathogenic fungi on plum fruits. Copyright © 2012 Society of Chemical Industry     

Antifungal activity of water‐soluble chitosan against Colletotrichum capsici in postharvest chili pepper

Experimental results proved that the development of Colletotrichum capsici B4 is extremely sensitive to water‐soluble chitosan (WSC) and inhibitory effects increase with increasing concentrations of WSC. In the in vitro test, the results showed that the entire prevention of conidial germination and mycelial diameter development are recognized in a potato dextrose agar medium containing 0.4% and 0.8% WSC, respectively. WSC was more efficient in a potato dextrose broth where it absolutely prevented the mycelial development of C. capsici B4 at a concentration of 0.32%. WSC treatments considerably decreased disease prevalence and the lesion diameter of anthracnose disease on chilli pepper fruits in the in vivo experiments. Experiments in biochemistry indicated that the activities of the key defense‐related enzymes in peel, consisting of chitinase, β‐1,3‐glucanase and total phenolic content, were increased by both C. capsici B4 infection and C. capsici B4 treatment, and was further treated with a 0.5% WSC concentration.

Practical applications

From the present studies we conclude that water‐soluble chitosan (WSC) can directly inhibit the development of C. capsici B4 isolated from infected chili pepper fruits showing typical symptoms of anthracnose in in vitro and effectively control anthracnose in chili pepper fruit in in vivo with concentration‐dependent antifungal effects. These findings suggest that WSC may be recognized as a feasible effective alternative to artificial fungicides for postharvest disease control of chili pepper fruits.     

A novel antifungal peptide from foxtail millet seeds

BACKGROUND: Antifungal proteins (AFP) help plants to combat phytopathogenic fungi and thus protect plants from the devastating damage caused by fungal infections and prevent massive economic losses. To date, several proteins with antibacterial and/or antifungal properties have been isolated and characterized from different plant species and tissues; however, there are no reports concerning the antifungal peptide from foxtail millet seeds. RESULTS: An antifungal peptide with a molecular mass of 26.9 kDa was isolated from dry seeds of the foxtail millet (Setaria italica (L.) Beauv.), using a procedure that involved four chromatographic steps. The antifungal peptide was adsorbed on CM‐Sepharose, Affi‐gel blue gel and Superdex 75. It was further purified by C₁₈ reverse‐phase high‐performance liquid chromatography and submitted for analysis of peptide mass fingerprint. The Mascot peptide mass fingerprint of the isolated protein hit no existing protein (score > 60), and it was proved to be a novel antifungal peptide. It inhibited mycelial growth in Alternaria alternate with an IC₅₀ of 1.3 µmol L^?1, and it also exhibited antifungal activity against Trichoderma viride, Botrytis cinerea and Fusarium oxysporum. Transmission electron microscopy of mold forms of Alternaria alternate after incubation with 20 µg mL^?1 of the antifungal protein for 48 h revealed marked ultrastructural changes in the fungus. CONCLUSION: A novel antifungal peptide with high potency was isolated from foxtail millet seeds. Copyright © 2011 Society of Chemical Industry     

Biological control of Penicillium italicum of Citrus and Botrytis cinerea of Grape by Strain 34–9 of Kloeckera apiculata

The biological control capability of strain 34-9 of Kloeckera apiculata against Penicillium italium (Wehmer), postharvest rot of citrus fruits and Botrytis cinerea, postharvest rot of grape fruits was studied in vitro and in vivo. Strain 34-9 of K. apiculata at 3×10⁸ CFU (colony-forming unit)/ml of washed cells provided complete control of 3×10⁵ spores/ml of P. italium and B. cinerea during storage at 25 °C for 6 d. Antagonist population increased 40, 195 times in citrus fruit wound site and grape fruit wound site at 25 °C for 3 d, respectively, then the population stabilized for the remaining storage period. Cell-free culture filtrate, supernatant fluid and sterilized solution of strain 34-9 of K. apiculata had no antagonist against P. italium of citrus and B. cinerea of grape. These results showed that competition for nutrient, not antibiotic production, played a major role in the biological control capability of strain 34-9 of K. apiculata against P. italium of citrus and B. cinerea of grape.     

Chemical composition of Ocimum basilicum L. essential oil and its efficacy as a preservative against fungal and aflatoxin contamination of dry fruits

The study presents fungal and aflatoxin contamination of some dry fruits and Ocimum basilicum essential oil (EO) as a plant‐based preservative. During mycoflora analysis, 2045 fungal isolates were recorded from dry fruits and 40% isolates of Aspergillus flavus were toxigenic in nature. The EO of O. basilicum exhibited strong fungitoxicity against toxigenic strain of A. flavus. Its minimum inhibitory concentration (MIC) was recorded at 1.0 μL ml^?1, and it completely inhibited aflatoxin B₁ production at 0.5 μL ml^?1. The oil exhibited broad fungitoxic spectrum and considerably reduced A. flavus isolates from dry fruits when used as fumigant in closed storage containers at 1.0 μL ml^?1. The chemical profile of the EO was standardised through GC–MS analysis. Based on antifungal potency, antiaflatoxigenicity and efficacy as fumigant during storage conditions, O. basilicum EO may be recommended as a botanical preservative for enhancing the shelf life of dry fruits and edible products during storage.     

Fabrication of chitosan nanoparticles incorporated with Pistacia atlantica subsp. kurdica hulls’ essential oil as a potential antifungal preservative against strawberry grey mould

Essential oil was extracted from Pistacia atlantica subsp. kurdica hulls and encapsulated in chitosan nanoparticles (NPs) by an emulsion-ionic gelation method. A desirable retention rate (43.3–61.5%) of P. atlantica subsp. kurdica hulls’ essential oil (PAHEO) encapsulated in chitosan NPs was confirmed. In addition, the Fourier transform infrared spectroscopy and X-ray diffraction analysis results revealed the success of PAHEO encapsulation. The formed NPs illustrated a shrunk and spherical shape with a size range of 187.2–632.5 nm as indicated by scanning electron microscopy and dynamic light scattering. The encapsulated PAHEO had a high antifungal activity against Botrytis cinerea under both the in vitro and in vivo conditions. It also significantly decreased the incidence and disease severity of grey mould on strawberries during storage. The spoilage process was postponed by the 8th days of storage at 4 °C in the strawberry fruit treated by PAHEO-incorporated chitosan NPs. These findings imply that NP-encapsulated PAHEO will have promising novel applications in food industries.     

Selected Quality Characteristics of Fresh‐Cut Sweet Potatoes Coated with Chitosan during 17‐Day Refrigerated Storage

ABSTRACT: Selected quality characteristics of fresh‐cut sweet potatoes (FCSP) coated with chitosan were evaluated during 17‐d refrigerated storage. The FCSP cubes were coated with a solution (1%, w/v) of chitosan having 470 or 1110 kDa. Color (L*, a*, b*) values of uncoated and chitosan‐coated FCSP during storage were generally affected by storage time as well as coating treatments (P < 0.05). No significant changes in color lightness (L*) of 470 kDa‐coated FCSP were observed during the 17‐d storage. During days 3 to 17, 470 kDa‐coated FCSP had significantly higher redness (a*) and yellowness (b*) values than did uncoated and 1110 kDa‐coated FCSP. Texture firmness of uncoated and chitosan‐coated FCSP exhibited minimal changes during the 17‐d storage. Although actual weight loss values (%) of uncoated and chitosan‐coated FCSP were not significantly different at day 17, the weight loss difference (%) between day 3 and day 17 for uncoated FCSP (3.02%) was slightly higher compared to those (2.24% to 2.26%) of chitosan‐coated FCSP. The initial total aerobic count was 4.7 log₁₀ CFU/g which then gradually increased to 8.54 and 9.67 log₁₀ CFU/g after 17 d of storage for 470 kDa‐coated and uncoated FCSP, respectively. After day 6, the total aerobic counts of uncoated FCSP were higher than those of 470 kDa‐coated FCSP. The yeast and mold count of chitosan‐coated FCSP was about 2.5 log₁₀ CFU/g at day 17. Overall, consumers could not differentiate between 470 kDa‐coated FCSP at day 17 and uncoated FCSP at day 0.     

Preservation of Strawberries with an Antifungal Edible Coating Using Peony Extracts in Chitosan

Strawberries represent a valuable source of bioactive compounds including vitamin C, E, β-carotene, and phenolic compounds, but they are fruits with an extremely short postharvest life. Therefore, the current study was conducted to investigate the effectiveness of an active coating consisting in antifungal microparticles obtained by spray drying of peony extracts (Paeonia rockii (PPR)) dispersed in chitosan (Ch) and subsequent addition to polysaccharide gels to slow the fungal attack of small highly perishable fruits, such as strawberries. The results of the antimicrobial assays indicate that the peony extracts in chitosan are able to counteract effectively the growth of different fungal isolates from deteriorated strawberries. In conclusion, through the treatment with this antifungal coating, it is possible to prolong the shelf life of delicate fruits, such as strawberries, to about 16 days, slowing down the weight loss, affecting the safeguard of important vitamins and antioxidant capacity during storage, without causing any significant alteration of the nutritional and sensorial properties of the product.     

Biocontrol of postharvest gray and blue mold decay of apples with Rhodotorula mucilaginosa and possible mechanisms of action

The efficacy of Rhodotorula mucilaginosa against postharvest gray mold, blue mold and natural decay development of apples and the possible mechanisms involved were investigated. The decay incidence and lesion diameter of gray mold and blue mold of apples treated by R. mucilaginosa were significantly reduced compared with the control fruits, and the higher concentration of R. mucilaginosa, the better the efficacy of the biocontrol. R. mucilaginosa also significantly reduced the natural decay development of apples following storage at 20 °C for 35 days or at 4 °C for 45 days followed by 20 °C for 15 days. Germination and survival of spores of Penicillium expansum and Botrytis cinerea were markedly inhibited by R. mucilaginosa in an in vitro test. Rapid colonization of the yeast in apple wounds was observed whether stored at 20 °C or 4 °C. In apples, the activities of peroxidase (POD) and polyphenoloxidase (PPO) were significantly induced and lipid peroxidation (malondialdehyde (MDA) content) was highly inhibited by R. mucilaginosa treatment compared with those of the control fruits. All these results indicated that R. mucilaginosa has great potential for development of commercial formulations to control postharvest pathogens on fruits. Its modes of action were based on competition for space and nutrients with pathogens, inducement of activities of defense-related enzymes such as POD, PPO and inhibition of lipid peroxidation (MDA content) of apples, so as to enhance the resistance and delay the ripening and senescence of apples.     

Antifungal Coatings on Fresh Strawberries (Fragaria × ananassa) to Control Mold Growth During Cold Storage

ABSTRACT: Chitosan (2%) -based or hydroxypropyl methylcellulose (HPMC) (1%) -based coatings were applied on fresh strawberries to evaluate their antifungal efficacies against Cladosporium sp. and Rhizopus sp. Potassium sorbate (PS) was also incorporated into coating formulas to evaluate any additional inhibitory effects on mold inhibition. Strawberries were inoculated with Cladosporium sp. or Rhizopus sp. at a level of approximately 10³ log colony-forming units (CFU) /g, coated with 2% chitosan, 2% chitosan containing 0.3% PS, or 1% HPMC containing 0.3% PS, and stored at about 5°C and about 50% RH up to 23 d for enumeration of mold, yeast, total aerobes, and coli forms. To assess antifungal activity of the coating materials in vitro, coating solutions were embedded into agar plates and the diameters of radial mold growth were measured after inoculation. In addition, weight loss of coated strawberries and water vapor permeability of the coatings were measured. No significant combined inhibitory effects between chitosan and PS on fungal growth on fresh strawberries were detected. However, significant combined inhibition activity was observed in in vitro testing when PS was formulated into chitosan. Antifungal activity of chitosan against Cladosporium sp. and Rhizopus sp. was not affected by the autoclaving process of coating solutions. Coating treatment also reduced total aerobic count, coliforms, and weight loss of strawberries during storage. Hence, chitosan can be used as a natural antimicrobial coating on fresh strawberries to control the growth of fungi, thus extending shelf-life of the fruits.     

In vitro and in vivo antifungal properties of cysteine proteinase inhibitor from green kiwifruit

BACKGROUND: Higher plants possess several mechanisms of defense against plant pathogens. Proteins actively synthesized in response to those stresses are called defense‐related proteins which, among others, include certain protease inhibitors. It is of particular relevance to investigate plant natural defense mechanisms for pathogen control which include cystatins—specific inhibitors of cysteine proteases. RESULTS: In this study, a cysteine proteinase inhibitor (CPI), 11 kDa in size, was purified from green kiwifruit to homogeneity. Immuno‐tissue print results indicated that CPI is most abundant in the outer layer of pericarp, near the peel, and the inner most part of the pulp—sites where it could act as a natural barrier against pathogens entering the fruit. The purified protein (15 µmol L^?1) showed antifungal activity against two phytopathogenic fungi (Alternaria radicina and Botrytis cinerea) by inhibiting fungal spore germination. In vivo, CPI (10 µmol L^?1) was able to prevent artificial infection of apple and carrot with spore suspension of B. cinerea and A. radicina, respectively. It also exerted activity on both intracellular and fermentation fluid proteinases. CONCLUSION: Identification and characterization of plant defense molecules is the first step towards creation of improved methods for pathogen control based on naturally occurring molecules. Copyright © 2012 Society of Chemical Industry     

Effect of formulated zimmu (Allium cepa L. × Allium sativum L.) extract in the management of grain mold of sorghum

BACKGROUND: The in vitro antifungal activity of zimmu (Allium cepa L. × Allium sativum L.) extract against Aspergillus flavus Link., Fusarium moniliforme Sheld, Curvularia lunata (Wakker) Boedijn and Alternaria alternata (Fr.) Keissler, the fungi associated with grain mold of sorghum, was evaluated. An emulsifiable concentrate (EC) formulation of zimmu extract was prepared and its efficacy in controlling grain mold was tested under field conditions. RESULTS: The leaf extract of zimmu exhibited strong antifungal activity against A. flavus, F. moniliforme, C. lunata and A. alternata and caused in vitro fungal growth inhibition of 73.3%, 71.1%, 70.0% and 74.4%, respectively. Foliar application of zimmu formulation 50 EC at 3 mLL^?1 (v/v) concentration 60, 75 and 90 days after sowing significantly reduced the incidence of grain mold and increased the grain weight and grain hardness. A significant reduction in the aflatoxin B1 content in sorghum grains was observed when sorghum plants were sprayed with zimmu formulation 50 EC at 0.3% concentration. Western blot analysis revealed that a thaumatin‐like protein (TLP) a molecular mass of 23 kDa that cross‐reacted with zeamatin antiserum was expressed at higher levels in sorghum grains after treatment with zimmu formulations. CONCLUSION: The leaf extract of zimmu exhibited antifungal activity against sorghum grain mold fungi. The formulated zimmu extract was significantly effective in reducing the grain mold incidence in sorghum under field conditions. This formulated zimmu extract offers a novel alternative for eco‐friendly management of grain mold of sorghum. Copyright © 2007 Society of Chemical Industry     

Growth of Botrytis cinerea and Strawberry Quality in Ozone-enriched Atmospheres

Botrytis cinerea cultures were stored on potato dextrose agar in air with or without 1.5 μL/L ozone at 2 °C. Cultures stored in the presence of ozone grew slower. Strawberry fruits (Fragaria×ananassa cv. Camarosa) were stored for 3 d at 2 °C in air with or without 1.5 μL/L ozone and then transferred to room temperature. Each group was inoculated with B. cinerea grown in air with or without ozone. Visible mycelial growth developed more rapidly on fruit previously stored in air. Ozone‐enriched cold storage of naturally infected ‘Camarosa’ fruit reduced decay incidence, weight loss, and fruit softening, but resulted in a reversible loss of fruit aroma.