Maintaining postharvest quality of fresh produce with volatile compounds

Evaluation of the efficacy of cinnamon oil on Aspergillus flavus and Fusarium proliferatum growth and mycotoxin production on paddy and polished rice: Towards a mitigation strategy

In the present investigation, the effect of cinnamon oil (CO) (10, 30, 50 and 70 %) on the growth rate (mm/day) and aflatoxin B1 (AFB1) and fumonisin B1 (FB1) production of Aspergillus flavus (AF01) and Fusarium proliferatum (FP01) isolates, respectively was determined at optimum water activities (0.95 and 0.99 aw) and temperatures (25, 30 and 35 °C) on paddy and polished rice grains. The results showed that the growth rate, AFB1 and FB1 production of all the fungal isolates decreased with an increase in CO concentrations on both matrices. AF01 and FP01 failed to grow under all conditions on paddy at 50 % of CO concentration whereas both fungi were completely inhibited (No Growth-NG) at 70 % of CO on polished rice. Regarding mycotoxin production, 30 % of CO concentrations could inhibit AFB1 and FB1 production in both matrices (No Detection-ND). In this study, the production of mycotoxins was significantly influenced by cinnamon oil compared to the growth of both fungi. These results indicated the promising potential of CO in improving the quality of rice preservation in post-harvest; however, further investigations should be evaluated on the effects on the qualitative characteristics of grains. Especially, the prospective application of CO in rice storage in industry scales to mitigate mycotoxin contamination need also to be further researched. Moreover, collaboration between researchers, agricultural experts, and food industry should be set up to achieve effective and sustainable strategies for preserving rice.

Combined application of hot water treatment and eucalyptus leaf extract postpones seneṣcence in harvested green chilies by conserving their antioxidants: a sustainable approach

BACKGROUND

Green chili is the predominant vegetable in tropical and subtropical regions with high economic value. However, after harvest, it exhibits vigorous metabolic activities due to the high moisture level, leading to a reduction in bioactive compounds and hence reduced shelf life and nutritional quality. Low temperature storage results in the onset of chilling injury symptoms. Therefore, developing techniques to increase the shelf life of green chilies and safeguard their nutritional value has become a serious concern for researchers. In this regard, an experiment was conducted to evaluate the impact of the alone or combined application of hot water treatment (HWT) (45 °C for 15 min) and eucalyptus leaf extract (ELE) (30%) on 'Golden Hot' chilies in comparison to the control. After treatment, chilies were stored at 20 ± 1.5 °C for 20 days.

RESULTS

HWT + ELE-treated chilies had a significant reduction in fruit weight loss (14.6%), fungal decay index (35%), red chili percentage (41.2%), soluble solid content (42.9%), ripening index (48.9%), and reactive oxygen species production like H2O2 (55.1%) and O-2 (46.5%) during shelf in comparison to control, followed by the alone application of HWT and ELE. Furthermore, the combined use of HWT and ELE effectively improved the antioxidative properties of stored chilies including DPPH radical scavenging activities (54.6%), ascorbic acid content (28.4%), phenolic content (31.8%), as well as the enzyme activities of POD (103%), CAT (128%), SOD (26.5%), and APX (43.8%) in comparison to the control. Additionally, the green chilies underwent HWT + ELE treatment also exhibited higher chlorophyll levels (100%) and general appearance (79.6%) with reduced anthocyanin content (40.8%) and wrinkling (43%), leading to a higher marketable fruit (41.3%) than the control.

CONCLUSION

The pre-storage application of HWT and ELE could be used as an antimicrobial, non-chemical, non-toxic, and eco-friendly treatment for preserving the postharvest quality of green chilies at ambient temperature (20 ± 1.5 °C).

Assessment of Ocimum basilicum Essential Oil Anti-Insect Activity and Antimicrobial Protection in Fruit and Vegetable Quality

Basil (Ocimum basilicum) is a commonly used herb; it also contains essential oils and other valuable compounds. The basil oil obtained has a pleasant aroma, but also a broad spectrum of biological activity. This work reports on the chemical composition, antioxidant, antimicrobial and anti-insect activity in vitro and in situ of Ocimum basilicum essential oil (OBEO) obtained by steam distillation of fresh flowering plants. Gas chromatography-mass spectrometry, DPPH, agar and disc diffusion and vapor phase methods were used to analyze the OBEO properties. The analysis of the chemical composition of OBEO showed that its main components were methyl chavicol (88.6%), 1,8-cineole (4.2%) and α-trans-bergamotene (1.7%). A strong antioxidant effect was demonstrated at the level of 77.3%. The analysis of antimicrobial properties showed that OBEO exerts variable strength of inhibiting activity against various groups of microorganisms. The growth inhibition zones ranged from 9.67 to 15.33 mm in Gram-positive (G+) and Gram-negative (G-) bacteria and from 5.33 to 7.33 mm in yeast. The lowest measured minimal inhibition concentration (MIC) was 3.21 µL/mL against Gram-negative Azotobacter chrococcum and Gram-positive Micrococcus luteus. The antimicrobial activity of in situ vapor phase of OBEO was also confirmed on apples, pears, potatoes and kohlrabi. The highest insecticidal activity against Pyrrhocorisapterus, observed at the concentration of 100%, caused the death of 80% of individuals. Due to its broad spectrum of activity, OBEO seems an ideal candidate for preserving fruit and vegetables.

Vapour Application of Sage Essential Oil Maintain Tomato Fruit Quality in Breaker and Red Ripening Stages

Consumers seek safe, high-nutritional-value products, and therefore maintaining fresh produce quality is a fundamental goal in the food industry. In an effort to eliminate chemical-based sanitizing agents, there has been a shift in recent decades toward the usage of eco-friendly, natural solutions (e.g., essential oils-EOs). In the present study, tomato fruits (Solanum lycopersicum L. cv. Dafni) at breaker and red ripening stage were exposed to sage essential oils (EO: 50 μL L^-1 or 500 μL L^-1) for 2, 7 and 14 days, at 11 °C and 90% relative humidity (RH). Quality-related attributes were examined during (sustain effect-SE) and following (vapour-induced memory effect-ME; seven days vapours + seven days storage) vapour treatment. In breaker tomatoes, EO-enrichment (sustained effect) retained fruit firmness, respiration rates, and ethylene emission in low EO levels (50 μL L^-1). In contrast, breaker fruit metabolism sped up in high EO levels of 500 μL L^-1, with decreased firmness, increased rates of respiration and ethylene, and effects on antioxidant metabolism. The effects were more pronounced during the storage period of 14 days, comparing to the fruit exposed to common storage-transit practice. In red fruits, the EOs impacts were evidenced earlier (at two and seven days of storage) with increased rates of respiration and ethylene, increased β-carotene, and decreased lycopene content. In both breaker and red ripening fruit, EO application decreased weight losses. Considering the fruits pre-exposed to EOs, quality attributes were more affected in green fruits and affected to a lesser level in the red ones. Furthermore, based on appearance, color, and texture evaluations, organoleptic trials demonstrated an overwhelming preference for EO-treated red fruit during choice tests. EOs had lower effects on total phenolics, acidity, total soluble solids, and fruit chroma, with no specific trend for both breaker and red tomatoes. Natural volatiles may aid to retain fruit quality in parallel with their antimicrobial protection offered during storage and transportation of fresh produce. These effects may persist after the EO is removed from the storage conditions.

Phytochemical and antimicrobial investigation of the leaves of five Egyptian mango cultivars and evaluation of their essential oils as preservatives materials

The sterols, hydrocarbons and fatty acids constituents of the leaves of five mango cultivars locally implanted in Egypt were identified. The effect of their essential oils (EOs) against food borne microorganisms was studied as preservative materials. The chemical constituents of the EOs isolated from mango leaves were identified by Gas Chromatography-Mass spectrometry (GC-MS) technique. Trans-caryophyllene, α-humulene and α-elemene were identified as terpene hydrocarbons, while 4-hydroxy-4-methyl-2-pentanone as oxygenated compounds were recorded in all tested cultivars with variable amounts. Results showed that Staphylococcus aureus and Escherichia coli were the most sensitive microorganisms tested for Alphonso EOs. On the other hand, Salmonella typhimrium was found to be less susceptible to the EOs of the studied cultivars. The EOs of different mango cultivars induced a steady decrease in the activity of amylase, protease and lipase at the minimum inhibitory concentration (MIC). The treatment of the tested bacteria with the EOs of mango cultivars caused a steady loss in enterotoxins even when applied at the sub-MIC. Bacteria-inoculated apple juice treated with minimum bactericidal concentration of Alphonso oil was free from the bacteria after 5 days of incubation at 25 °C. Eighteeen volatile compounds were found to reduce the activity of the amylase enzyme and the most active was cedrelanol (-7.6 kcal mol-1) followed by alpha-eudesmol (-7.3 kcal mol-1) and humulene oxide (-7 kcal mol-1). The binding mode of both of cedrelanol and alpha-eudesmol with amylase enzyme was illustrated.

Post-Harvest Enhancing and Botrytis cinerea Control of Strawberry Fruits Using Low Cost and Eco-Friendly Natural Oils

This work investigates an experimental study for using low-cost and eco-friendly oils to increase the shelf life of strawberry fruit. Three natural oils were used: (i) Eucalyptus camaldulensis var obtuse, (ii) Mentha piperita green aerial parts essential oils (EOs), and (iii) Moringa oleifera seeds n-hexane fixed oil (FO). Furthermore, a mixture of EOs from E. camaldulensis var obtusa and M. piperita (1/1 v/v) was used. The treated fruits were stored at 5 °C and 90% relative humidity (RH) for 18 days. HPLC was used to analyse the changes in phenolic compounds during the storage periods. The effects of biofumigation through a slow-release diffuser of EOs (E. camaldulensis var obtusa and M. piperita), or by coating with M. oleifera FO, were evaluated in terms of control of post-harvest visual and chemical quality of strawberry fruits. The post-harvest resistance of strawberry fruits to Botrytis cinerea fungal infection was also evaluated. As a result, the EO treatments significantly reduced the change in visual and chemical quality of strawberry fruit. Additionally, changes in the titratable acidity of moringa FO-coated strawberry fruits were delayed. EO treatments improved total soluble solids, total phenols, ascorbic acid, antioxidants and peroxidase. E. camaldulensis var obtusa and M. piperita (1/1 v/v) EO-vapour fruit exhibited a slower rate of deterioration, compared to other treatments in all tested, in two experiments. The lowest colour change (ΔE) was observed inthe fruit treated with E. camaldulensis var obtusa EO and M. oleifera FO. HPLC showed changes in phenolic compounds’ concentration, where p-coumaric acid, caffeic acid, gallic acid, ferulic acid and ellagic acid were mostly identified in the fruits treated with the oils. SEM examination confirmed the potential decrease in fungal growth as the fruits were treated with EOs. In conclusion, the treatment of EOs during different storage periods showed promising characterisations for strawberry fruit quality.

Quality Attributes and Storage of Tomato Fruits as Affected by an Eco-Friendly, Essential Oil-Based Product

The preservation of fresh produce quality is a major aim in the food industry since consumers demand safe and of high nutritional value products. In recent decades there has been a turn towards the use of eco-friendly, natural products (i.e., essential oils-EOs) in an attempt to reduce chemical-based sanitizing agents (i.e., chlorine and chlorine-based agents). The aim of this study was to evaluate the efficacy of an eco-friendly product (EP—based on rosemary and eucalyptus essential oils) and two different application methods (vapor and dipping) on the quality attributes of tomato fruits throughout storage at 11 °C and 90% relative humidity for 14 days. The results indicated that overall, the EP was able to maintain the quality of tomato fruits. Dipping application was found to affect less the quality attributes of tomato, such as titratable acidity, ripening index and antioxidant activity compared to the vapor application method. Vapor application of 0.4% EP increased fruit’s antioxidant activity, whereas tomatoes dipped in EP solution presented decreased damage index (hydrogen peroxide and lipid peroxidation levels), activating enzymes antioxidant capacity (catalases and peroxidases). Moreover, higher EP concentration (up to 0.8%) resulted in a less acceptable product compared to lower concentration (0.4%). Overall, the results from the present study suggest that the investigated EP can be used for the preservation of fresh produce instead of the current commercial sanitizing agent (chlorine); however, the method of application and conditions of application must be further assessed for every commodity tested.

In vitro and in vivo antifungal activity of Cuminum cyminum essential oil against Aspergillus aculeatus causing bunch rot of postharvest grapes

Bunch rot in grapes is an aggressive disease and needs to be controlled during the postharvest period. We investigate the antifungal potential of Zanthoxylum bungeanum Maxim., Zanthoxylum rhetsa, Cuminum cyminum, Coriandrum sativum, and Zingiber montanum (J. Koenig) Link ex A. Dietr. essential oils against Aspergillus aculeatus that cause bunch rot disease on postharvest grapes. C. cyminum essential oil exhibited stronger significantly inhibition percentage of 95.08% than other treatments in in vitro assay. Cumin aldehyde (33.94%) and α-terpinen-7-al (32.20%) were identified as major volatile compounds in C. cyminum oil. Antifungal potential of C. cyminum oil was then tested in conidia germination and in vitro tests compared to cumin aldehyde and α-terpinen-7-al. Their EC₅₀ values against the conidial germination were also estimated. Significant reduction of conidia germination was also detected in C. cyminum essential oil and cumin aldehyde at a concentration of 1,000 and 100 μg/mL, respectively. EC₅₀ values of the C. cyminum essential oil, cumin aldehyde, and α-terpinen-7-al were 67.28 μg/mL, 9.31 μg/mL, and 13.23 μg/mL, respectively. In vivo assay, the decrease of the disease severity (0.69%) and incidence (1.48%) percentage of A. aculeatus on grape berries treated at 1,000 μg/mL of C. cyminum essential oil was significantly greater than that obtained from other treatments after 10 days incubation. In addition, grape berries treated with C. cyminum essential oil decreased weight loss and retained fruit firmness. The changing of total soluble solids, total phenolic content, and antioxidant activity are also delayed in treated fruits. Therefore, essential oil of C. cyminum may be applied as a biological antifungal agent to control A. aculeatus in postharvest grapes without any negative effects on its quality.

Assessing the Biostimulant Effects of a Novel Plant-Based Formulation on Tomato Crop

The aim of this research was to evaluate the biostimulant effects of an eco-product (EP) containing essential oils of rosemary and eucalyptus on tomato crop. Experiments were conducted to evaluate EP effects on plant growth and physiological parameters (e.g., chlorophyll content), total phenols and antioxidant activity, enzyme activities (e.g., catalase), plant macronutrient content and fresh tomato fruit quality. The application of an EP once (EP-1x) increased tomato plant height by 19%, stomatal conductance, and chlorophyll content compared to the control (sprayed with water). EP triplicate (EP-3x) application significantly increased yield (0.79 kg plant−1) compared to the control (0.58 kg plant−1). However, application of EP-3x was associated with a higher percentage of fruit cracking in comparison to the control. Total phenols and antioxidant activity were affected from both the use of EP and application frequency. EP application decreased by 27.3% the leaf damage index in comparison to the control. Nutrient content in leaves (N, Mg) was significantly decreased in the case of EP-3x treatment. Fruit firmness was decreased by 19.9% in the case of EP-1x application. Fruit marketability and tomato-like aroma, fresh weight and soluble solids did not differ among the treatments. Further research is required to examine the potential use of essential oils as biostimulants.

Assessment of Mint, Basil, and Lavender Essential Oil Vapor-Phase in Antifungal Protection and Lemon Fruit Quality

There is an increasing interest in developing natural methods to replace the current chemicals used for maintaining postharvest quality of citrus fruits. The essential oil antifungal activity of mint (MEO), basil (BEO), and lavender (LEO) acting as the vapor-phases was tested against Penicillium digitatum. The minimum doses with fungistatic and fungicidal effect, in vitro, acting as the vapor-phases, were set up. The minimum fungicidal dose was 300 μL for BEO and 350 μL LEO, while for MEO only minimal dose with fungistatic effect was reached. The IC50 values were calculated and used (v/v) for testing preservation of lemon fruits, in close space enriched in vapor oil. For this purpose, the following two independent in vivo experiments were carried out: experiment 1, inoculated lemons with P. digitatum stored without chemical treatments 7 days, at 22 ± 2 °C, at two concentrations (C1—IC50 equivalent; C2—half of C1); and experiment 2, the non-inoculated lemons kept under the same conditions and concentrations of EO vapor served to evaluate the lemon quality properties. The results showed that antifungal protective effect was provided in the order of LEO-C1 > BEO-C1 > MEO-C1 > BEO-C2 > MEO-C2 > LEO-C2. The quality indicators like weight loss, pH, and firmness were not negatively influenced.

Sage Essential Oil Improves the Effectiveness of Aloe vera Gel on Postharvest Quality of Tomato Fruit

Edible coating is extensively applied for fresh produce preservation. In the present study, Aloe vera gel (AV) alone or combined with sage essential oil (EO; 0.1% or 0.5%) was used as fruit edible coating in tomatoes. Following treatments, tomatoes were stored at 11 °C and 90% relative humidity (RH) up to 14 days and analyzed for quality maintenance compared with uncoated fruits (control). Results showed that both AV and EO decreased decay symptoms with more pronounced effects on low EO concentration (i.e., 0.1%). The application of 10% of AV coating decreased fruit ethylene emission while EO (0.1% and 0.5%) application increased ethylene emission and respiration rates. AV coating decreased acidity, β-carotene, lycopene content and maintained fruit firmness. High levels of EO (0.5%) increased weight loss but decreased fruits’ redness, chroma, total soluble solids, acidity, β-carotene and lycopene content. Total phenolic content and antioxidants maintained or increased during storage when treated with AV and/or EO. Low levels of EO (0.1%) maintained or improved fruit quality characteristics during storage, and this was mirrored by the sensory evaluation preference (including the AV application) and quality related attributes.

Ethanol treatment improves the sensory quality of cherry tomatoes stored at room temperature

The effects of ethanol treatment on quality characteristics of cherry tomatoes were investigated over 11 days of storage at room temperature (25 °C). Results showed that sensory quality was improved after ethanol treatment, with redder, softer fruits at the edible stage (11 days) compared with control fruit. In addition, the contents of ascorbic acid, sucrose and fructose were elevated after ethanol treatment as well as the concentration of 6-methyl-5-hepten-2-one. Conversely, decreased levels of methyl salicylate (MeSA), guaiacol, (Z)-3-hexenal and (E)-2-hexenal were observed. Selected consumers showed a preference for ethanol-treated cherry tomato fruits compared with controls. Taken together, 0.1% ethanol application has the potential to improve the quality characteristics of cherry tomatoes stored at room temperature.

Antifungal Activity of the Volatile Phase of Essential Oils: A Brief Review

Interest in the antifungal activity of essential oils has increased markedly in recent years. The volatile (vapour) components of several essential oils have been demonstrated to have potent antifungal activity, often in excess of that displayed in direct contact assays. A lack of consistent methodology and reporting, however, hinders direct comparison of publications. A variety of mechanisms have been suggested for the activity of these active volatiles against hyphate fungi. This paper briefly reviews some of the more recent data and identifies areas that require standardization and further study.

Essential oils in vapor phase as alternative antimicrobials: A review

The antimicrobial effectiveness of essential oils (EOs) against many foodborne microorganisms when applied by direct contact has been extensively demonstrated. However, the vapor phase and volatile components present in EOs have not been thoroughly investigated; there are a small number of published reports on the antimicrobial activity of some EOs and a few of their components against selected microorganisms. It is well known that the antimicrobial activity of EOs depends mainly on their chemical composition. It is also important; however, to understand the volatility of these compounds as well as the methodologies used to evaluate the antimicrobial effectiveness of their vapor phase. This review focuses on recent research regarding the chemical composition of EOs, their biological activity and mechanisms of action, the antimicrobial activity of EOs in the vapor phase, the different techniques that have been proposed to evaluate the antimicrobial effects of EOs in the vapor phase, and actual and potential applications of EOs in the vapor phase. Although there is still no standard methodology for determining the activity of EOs in the vapor phase, results reported thus far are encouraging and suggest possible applications in food preservation.

Role of Natural Volatiles and Essential Oils in Extending Shelf Life and Controlling Postharvest Microorganisms of Small Fruits

Small fruits are a multi-billion dollar industry in the US, and are economically important in many other countries. However, they are perishable and susceptible to physiological disorders and biological damage. Food safety and fruit quality are the major concerns of the food chain from farm to consumer, especially with increasing regulations in recent years. At present, the industry depends on pesticides and fungicides to control food spoilage organisms. However, due to consumer concerns and increasing demand for safer produce, efforts are being made to identify eco-friendly compounds that can extend the shelf life of small fruits. Most volatiles and essential oils produced by plants are safe for humans and the environment, and lots of research has been conducted to test the in vitro efficacy of single-compound volatiles or multi-compound essential oils on various microorganisms. However, there are not many reports on their in vivo (in storage) and In situ (in the field) applications. In this review, we discuss the efficacy, minimum inhibitory concentrations, and mechanisms of action of volatiles and essential oils that control microorganisms (bacteria and fungi) on small fruits such as strawberries, raspberries, blueberries, blackberries, and grapes under the three conditions.

Biological, medicinal and toxicological significance of Eucalyptus leaf essential oil: a review

The genus Eucalyptus L'Heritier comprises about 900 species, of which more than 300 species contain volatile essential oil in their leaves. About 20 species, within these, have a high content of 1,8-cineole (more than 70%), commercially used for the production of essential oils in the pharmaceutical and cosmetic industries. However, Eucalyptus is extensively planted for pulp, plywood and solid wood production, but its leaf aromatic oil has astounding widespread biological activities, including antimicrobial, antiseptic, antioxidant, chemotherapeutic, respiratory and gastrointestinal disorder treatment, wound healing, and insecticidal/insect repellent, herbicidal, acaricidal, nematicidal, and perfumes, soap making and grease remover. In the present review, we have made an attempt to congregate the biological ingredients of leaf essential oil, leaf oil as a natural medicine, and pharmacological and toxicological values of the leaf oil of different Eucalyptus species worldwide. © 2017 Society of Chemical Industry.

Characterization of microbial population of breba and main crops (Ficus carica) during cold storage: Influence of passive modified atmospheres (MAP) and antimicrobial extract application

The purpose of this work was to study the changes of bacterial and fungal population of breba fruits such as 'Banane' and 'San Antonio' as well as 'Cuello Dama Negro', 'Cuello Dama Blanco' and 'San Antonio' fig cultivars stored in passive modified atmospheres (MAP) by the use of three different microperforated films (M10 with 16 holes; M30 with five holes and M50 with three holes). Moreover the effects of the application of aqueous soy polyphenolic antimicrobial extract (APE), alone or combined with MAP, were also studied for 'Cuello Dama Negro' and 'Cuello Dama Blanco' fig cultivars. Bacteria and fungi isolates were identified by PCR-RFLP of 16S rRNA and ITS regions, respectively, and subsequently sequence of the different patterns obtained. The results indicated that Pseudomonas gessardii, Pantoea agglomerans and Enterobacter asburiae were the main species of bacteria found in all the treatments studied. The fungal species identified were Aureobasidium pulullans, Cladosporium cladosporioides and Alternaria alternata, which were found in a lower percentage in fruit stored in MAP and fruits treated with antimicrobial extracts, as this treatments allowed to reduce the microbial growth of moulds and yeasts. Thus, the application of treatments such as M30, M50 or the combination of MAP with antimicrobial extract was highly effective to control fruit spoilage in fig and breba crops.

Response of Aspergillus niger Inoculated on Tomatoes Exposed to Vapor Phase Mustard Essential Oil for Short or Long Periods and Sensory Evaluation of Treated Tomatoes

The inhibitory effect of mustard essential oil (EO) in vapor phase against Aspergillus niger was evaluated in vitro and in vivo (in tomatoes). Mold response in tomatoes exposed for short or long periods to selected concentrations of mustard EO was also evaluated. Furthermore, a sensory evaluation was also performed among treated tomatoes and compared with nontreated ones. Minimum inhibitory concentration (MIC) for the studied EO was determined by the inverted Petri dish method. MIC for the in vitro and in vivo tests for mustard EO was of 3.08 μL/Lair. In vitro and in vivo results demonstrate the effectiveness of vapors of mustard EO against A. niger. The studied EO contains highly volatile organic compounds with strong inhibitory effects, even when applied for short periods, and can consequently be considered a good alternative to traditional synthetic antimicrobials without detriment of selected sensory attributes.

Oregano (Lippia graveolens) essential oil added within pectin edible coatings prevents fungal decay and increases the antioxidant capacity of treated tomatoes

BACKGROUND

Tomato is a fruit widely consumed due to its flavor and nutritional value; however, it is susceptible to fungi contamination. Oregano essential oil (OEO) is a fungicide whose constituents are volatile; therefore, their incorporation within edible coatings can protect them and maintain their efficacy. In this context, this study evaluated the effect of OEO applied within pectin coatings on the inhibition of Alternaria alternata growth, antioxidant content and sensorial acceptability of tomatoes.

RESULTS

The major volatile compounds of OEO were carvacrol (47.41%), p-cymene (26.44%) and thymol (3.02%). All the applied OEO concentrations (15.7, 25.9 and 36.1 g L(-1) ) inhibited the in vitro growth of A. alternata, whereas the in vivo effective concentrations were 25.9 and 36.1 g L(-1) . Additionally, there was an increment of total phenols and antioxidant activity in coated tomatoes compared to controls. Aroma acceptability of tomatoes was not affected by the pectin-OEO coating; additionally, the pectin, pectin-OEO 15.7 g L(-1) treatments and control tomatoes showed higher flavor acceptability than those coated with pectin-OEO 25.9 and 36.1 g L(-1) .

CONCLUSION

Pectin-OEO coatings showed antifungal effect and increased the antioxidant activity without negative effects on the sensorial acceptability of tomatoes. © 2015 Society of Chemical Industry.

Application of lemongrass oil in vapour phase for the effective control of anthracnose of 'Sekaki' papaya

AIMS

To evaluate the potential use of lemongrass essential oil vapour as an alternative for synthetic fungicides in controlling anthracnose of papaya.

METHODS AND RESULTS

Lemongrass oil used in the study was characterized using gas chromatography-flame ionization detection (GC-FID) before it was tested against anthracnose of papaya in vitro and in vivo. The GC-FID analysis showed that geranial (45·6%) and neral (34·3%) were the major components in lemongrass oil. In vitro study revealed that lemongrass oil vapour at all concentrations tested (33, 66, 132, 264 and 528 μl l(-1) ) suppressed the mycelial growth and conidial germination of Colletotrichum gloeosporioides. For the in vivo study, 'Sekaki' papaya were exposed to lemongrass oil fumigation (0, 7, 14, 28 μl l(-1) ) for 18 h and at room temperature for 9 days. Lemongrass oil vapour at the concentration of 28 μl l(-1) was most effective against anthracnose of artificially inoculated papaya fruit while quality parameters of papaya were not significantly altered.

CONCLUSIONS

This suggests that lemongrass oil vapour can control anthracnose disease development on papaya without affecting its natural ripening process.

SIGNIFICANCE AND IMPACT OF THE STUDY

The potential practical application of this technology can reduce reliance on synthetic fungicides for the control of postharvest diseases in papaya.

Origanum dictamnus oil vapour suppresses the development of grey mould in eggplant fruit in vitro

Grey mould rot (Botrytis cinerea) development in vitro or in eggplant (Solanum melongena L.) fruit was evaluated after treatment with dittany (Origanum dictamnus L.) oil (DIT) and storage at 12°C and 95% relative humidity during or following exposure to the volatiles. DIT volatiles used in different concentration (0-50-100-250 μL/L) and times of exposure (up to 120 h) examined the effects on pathogen development as well as fruit quality parameters. In vitro, fungal colony growth was inhibited with the application of DIT oil (during or after exposure) and/or time of application. Continuous exposure to oils reduced conidial germination and production with fungistatic effects observed in 250 μL/L. In vivo, fungal lesion growth and conidial production reduced in DIT-treated fruits. Interesting, in fruits preexposed to volatiles before fungal inoculation, DIT application induced fruit resistance against the pathogen, by reduced lesion growth and conidial production. Conidial viability reduced in >100 μL/L DIT oil. Fruits exposed to essential oil did not affect fruit quality related attributes in general, while skin lightness (L value) increased in 50 and 100 μL/L DIT oil. The results of the current study indicated that dittany volatiles may be considered as an alternative food preservative, eliminating disease spread in the storage/transit atmospheres.

Effect of citronella essential oil on the inhibition of postharvest Alternaria alternata in cherry tomato

BACKGROUND

Essential oils such as citronella oil exhibit antifungal activity and are potential alternative inhibitors to chemical synthetic fungicides for controlling postharvest diseases. In this study the antifungal activity of citronella oil against Alternaria alternata was investigated.

RESULTS

In vitro, citronella oil showed strong inhibition activity against A. alternata. The minimum inhibitory concentration in potato dextrose agar and potato dextrose broth medium was determined as 1 and 0.8 µL mL(-1) respectively. In vivo the disease incidence of Lycopersicon esculentum (cherry tomato) treated with citronella oil was significantly (P < 0.05) reduced compared with the control after 5 days of storage at 25 °C and 95% relative humidity. The disease incidence at oil concentrations of 0.2-1.5 µL mL(-1) was 88-48%. The most effective dosage of the oil was 1.5 µL mL(-1), with 52% reduction, and the oil had no negative effect on fruit quality. Scanning electron microscopy observation revealed considerably abnormal mycelial morphology.

CONCLUSION

Citronella oil can significantly inhibit A. alternata in vitro and in vivo and has potential as a promising natural product for controlling black rot in cherry tomato.

The effect of oleum myrtle on the fruit quality of strawberries during MAP storage

Strawberries are known to be significant source of the nutraceuticals; however, rapid perishable property of this fruit is very important issue. Up to now, extension of this fruit is still the focus of scientific and industrial interest in the worldwide. Therefore, of the known nutraceuticals, myrtle essential oil in this study is intended to use for extending the storage of strawberries. Strawberries were individually immersed in the treatment solutions of 0.1 % myrtle oil, 0.5 % myrtle oil and then placed in Modified Atmosphere Packaging (MAP) for 8 days at 5 °C. The control fruits without myrtle oil treatment were also placed in MAP and stored under the same condition. Treatment of myrtle oil decreased the weight and the fruit firmness loss. Furthermore, titratable acidity (TA), pH and colour value did not display significant changes during storage. Fluctuations were observed in the vitamin C, total soluble solids (TSS), TSS/TA content and microbial growth. The O2 concentration in MAP decreased from 21 % to around 15 %, whereas, CO2 concentration varied from 6.0 to 6.9 % in the treatments by the 8th day of storage time. The delay of flesh firmness, weight loss, vitamin C loss and increasing CO2 concentration in MAP, best sensory quality as well as limiting the growth of microbial parameters in concern was attained through the use of 0.5 % myrtle oil, suggesting that 0.5 % myrtle oil showed more pronounced activity than 0.1 % myrtle oil and control in maintaining the fruit quality and shelf life of fruits during MAP storage.

Biocontrol of gray mold disease on strawberry fruit by integration of Lactobacillus plantarum A7 with ajwain and cinnamon essential oils

This study was conducted to evaluate the efficacy of the Lactobacillus plantarum A7 (L. Plantarum), ajwain and cinnamon essential oils (AO and CO, respectively) in suppressing gray mold rot in strawberry fruit. AO and CO showed over 90% inhibition of radial mycelia growth with lower concentration of the oils per plate for all tested pathogens. Combined application of L. plantarum with AO and CO was tested to assess the possible synergistic effects of these 3 elements on the control of tested plant pathogens. In this case both combinations of L. plantarum + AO and L. plantarum + CO inhibited the mycelia growth of the pathogens completely. Results showed that the combined treatment of strawberry fruits with L. plantarum + AO (50 μL) and L. plantarum + CO (100 μL) resulted in remarkably improved control of Botrytis infections, in comparison with application of L. plantarum or essential oils alone. Quality attributes (that is pH, acidity, vitamin C, and total soluble solid) of the strawberry fruits did not change significantly (P < 0.01) when combination of Lactobacillus and essential oils was used. To the best of our knowledge, this is the first report on the effects of combination of a Lactobacillus as an antagonist bacterium with essential oils to increase the shelf life of strawberry.

Impact of decomposing Cinnamomum septentrionale leaf litter on the growth of Eucalyptus grandis saplings

A pot experiment was performed to study the impact of decomposing Cinnamomum septentrionale leaf litter on the growth of Eucalyptus grandis saplings. The experimental design scheme was 0 (CK), 40 (A1), 80 (A2) and 120 g pot(-1) (A3) of E. grandis leaves, and changes in the volatile oil chemical composition during litter decomposition were assessed in the present study. The results showed that C. septentrionale leaf litter inhibited the growth of E. grandis saplings, as determined by the height, basal diameter and chlorophyll content, after 69 d (T1). Five months after transplantation (T2), the height growth rate of the E. grandis saplings increased and then gradually reduced (A1: 40 g pot(-1) > A2: 80 g pot(-1) > A3: 120 g pot(-1) > CK: 0 g pot(-1)). After eleven months (T3), the variations in the height and basal diameter were the same as observed at T2, and the inhibition on leaf, branch, root and stem biomass increased with increasing leaf litter content. Gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compound composition. The results indicated that the C. septentrionale original leaf litter (S1) contained thirty-one volatile compounds, but the treated leaf litter S2 (which was mixed with soil for eleven months to simultaneously plant E. grandis saplings) only possessed fourteen volatile compounds, releasing many secondary metabolites in the soil during decomposition. Most of the volatile compounds were alcohols, monoterpenoids, sesquiterpenes, alkanes, alkene, esters and ketones. Most of the allelochemicals of C. septentrionale might be released during the initial decomposing process, inhibiting the growth of other plants, whereas some nutrients might be released later, promoting the height growth of plants. In conclusion, decomposing C. septentrionale leaf litter release of many allelochemicals in the soil that significantly inhibit the growth of E. grandis.

The antimicrobial effects of cinnamon leaf oil against multi-drug resistant Salmonella Newport on organic leafy greens

There is generally no kill-step when preparing salad vegetables, so there is a greater risk for foodborne illness from contaminated vegetables. Some essential oils have antimicrobial activities and could provide a natural way to reduce pathogens on fresh produce. The objective of this study was to investigate the antimicrobial activity of cinnamon oil wash against Salmonella enterica serotype Newport on organic leafy greens. Organic romaine and iceberg lettuce, and organic baby and mature spinach were inoculated with Salmonella Newport and then dip treated in a phosphate buffered saline (PBS) control and 3 different concentrations (0.1, 0.3, and 0.5% v/v) of cinnamon oil. The treatment time varied at either 1 or 2min, and storage temperature varied at either 4 or 8°C. Samples were collected at days 0, 1, and 3. For romaine and iceberg lettuce, S. Newport was not recovered on day 3 for 2min 0.3% and 0.5% cinnamon oil treatments. For mature spinach, S. Newport was not recovered by day 3 for the 2min 0.3% and 0.5% 4°C treatments. For baby spinach, there was no recovery of S. Newport by day 1 for all 0.5% treatments. Overall, the cinnamon oil treatments were concentration and time dependent with higher concentrations and longer treatment times providing the greatest reduction in S. Newport population on leafy greens. In addition, the treatments had a residual effect with the greatest reduction generally seen on the last day of sampling. Storage temperature did not have a significant effect on the reduction of S. Newport. Based on the results of this study, cinnamon oil has the potential to be used as a treatment option for washing organic baby and mature spinach, and iceberg and romaine lettuces.

In vitro control of post-harvest fruit rot fungi by some plant essential oil components

Eight substances that are main components of the essential oils from three Mediterranean aromatic plants (Verbena officinalis, Thymus vulgaris and Origanum vulgare), previously found active against some phytopathogenic Fungi and Stramenopila, have been tested in vitro against five etiological agents of post-harvest fruit decay, Botrytis cinerea, Penicillium italicum, P. expansum, Phytophthora citrophthora and Rhizopus stolonifer. The tested compounds were β-fellandrene, β-pinene, camphene, carvacrol, citral, o-cymene, γ-terpinene and thymol. Citral exhibited a fungicidal action against P. citrophthora; carvacrol and thymol showed a fungistatic activity against P. citrophthora and R. stolonifer. Citral and carvacrol at 250 ppm, and thymol at 150 and 250 ppm stopped the growth of B. cinerea. Moreover, thymol showed fungistatic and fungicidal action against P. italicum. Finally, the mycelium growth of P. expansum was inhibited in the presence of 250 ppm of thymol and carvacrol. These results represent an important step toward the goal to use some essential oils or their components as natural preservatives for fruits and foodstuffs, due to their safety for consumer healthy and positive effect on shelf life extension of agricultural fresh products.

Vapour phase: a potential future use for essential oils as antimicrobials?

Essential oil (EO) vapours have been known for their antimicrobial properties since the 4th century B.C.; however, it was not until the early 1960s that research into the potential of these volatile oils was explored. More recently, the use of EOs such as tea tree, bergamot, lavender and eucalyptus in vapour form has been shown to have antimicrobial effects against both bacteria and fungi, with range of methods being developed for dispersal and efficacy testing. To date, many applications for EO vapours as antimicrobials have been identified including in the food and clinical arenas.