Mango Surface Research Articles

Surfactant-enhanced chitosan coating extends postharvest shelf-life of Keitt mango

The surface properties of Keitt mango and wettability of chitosan (CH) coatings containing ethyl lauroyl arginate (LAE, an ionic surfactant), and sucrose monolaurate (SML, a non-ionic surfactant) were investigated. The Keitt mangoes were coated with different chitosan-based solutions and stored at room temperature (25.0 ± 0.6 °C) for 35 days. The Keitt mango surface had low surface energy (<100 mN/m) with high dispersive component (17.70 ± 1.49–22.86 ± 1.02 mN/m). SML and LAE surfactants significantly (P < 0.05) lowered the surface tension of the CH coating solution by 6.94, and 24.13 mN/m, respectively. As a result, the wettability of CH based coating on mangoes was improved to −68.37 ± 0.01 mN/m (CH-SML), and −30.29 ± 0.00 mN/m (CH-LAE) compared with CH (−76.45 ± 0.04 mN/m), resulting in smooth and homogeneous coatings. The storage test results indicated a significant reduction (P < 0.05) in disease incidence and weight loss by the CH-SML and CH-LAE coatings and the coated mangoes were firmer with lower pH values compared with the control. This study suggests that CH-LAE and CH-SML coatings can effectively extend the shelf-life of Keitt mangoes by 10 and > 15 days, respectively.

Mango (Mangifera indica cv. Sein Ta Lone) ripeness level prediction using color and textural features of combined reflectance-fluorescence images

Sein Ta lone mango of different maturity level images has been obtained using reflectance and fluorescence imaging systems. It has been found that fluorescence images show interesting patterns in correlation with the accumulation of bluish fluorescence compounds in the lenticel spots on the mango surface. Color and textural features of both reflectance and fluorescence images have been evaluated to develop a ripeness prediction model. The results show that combining color features of reflectance image and textural features could increase the R2 of the Partial Least Square Regression (PLSR) model up to 0.97 for Brix prediction and 0.99 for pH prediction with Root Mean Square Error (RMSE) of 0.5 for both. These results show the potential of the combined reflectance-fluorescence imaging system for mango ripeness assessment.

Dynamics of bacterial and fungal communities of mango: From the tree to ready-to-Eat products

Processing, such as fresh cutting and drying, is essential to enhance profitability; therefore, to limit waste and reduce losses in fruit production such as mangoes. Metabarcoding and microbial enumeration methods were utilized to explore the structure of mango microbiota, as well as their evolution after processing. Two mango ripening stages of cv. Cogshall were selected and processed into fresh-cut pieces or dried slices. Microbiological and physicochemical parameters were monitored during product storage, in order to assess the dynamics of quantitative and qualitative variations of the microbial flora. Proteobacteria was the dominant bacterial phylum of the mango surface and accounted for 73.16%, followed by Actinobacteria (10.16%), Bacteroidetes (7.82%) and Firmicutes (6.68%). Aureobasidium and Cladosporium were the only two genera shared between all types of samples (peel surface, dried slices and mango fresh-cut). However, the bacterial genera Lactobacillus and Pantoea were the most abundant in fresh-cut mango after 14 days of storage. Ascomycota was the dominant fungal phylum in the mango surface and accounted for 90.76% of the total number of detected sequences, followed by Basidiomycota (9.21%). In total, 866 microbial genera were associated with mango surface (562 bacterial and 304 fungal). Among detected yeast genera, Saccharomyces, Candida and Malassezia prevailed in mango flesh and were replaced by Wickerhamomyces after 14 days of storage. Alpha and beta diversity analyzes revealed differences in fungal and bacterial communities on fruit peel, in fresh-cut, dried slices, and during conservation (fresh-cut and dried slices). Mango processing (washing, peeling, cutting and drying) reduced the richness and the microbial diversity (bacterial and fungal) associated to the fruit, and drying limits the development of cultivable microorganisms during storage in comparison to fresh-cuts mangoes.

Inactivation of Salmonella enterica and Colletotrichum gloeosporioides on Whole Mangoes by Application of an Antimicrobial Coating Containing Oregano Essential Oil

Mangoes are susceptible to bacterial and fungal contamination during storage and transportation. This study investigated the effectiveness of pectin-based coatings containing oregano essential oil (OEO) to reduce Salmonella enterica contamination and decrease anthracnose disease on whole mangoes. A cocktail of five strains of Salmonella spp. and Colletotrichum gloeosporioides strains was spot inoculated in mangoes to verify the antibacterial and antifungal activity of OEO. The inoculated mangoes were coated with pectin-based coatings containing 0, 0.5, 0.7, and 0.9% OEO. Coated fruits were stored for 11 days at 25 °C and 90% of relative humidity. All treatments with OEO effectively inhibited the growth of Salmonella, causing a reduction of 2.5 CFU/cm2 compared to the control treatment (0% OEO). In addition, coatings effectively inhibited the growth of C. gloeosporioides on the mango surface after 9 days of storage to the same extent as the traditional Prochloraz fungicide. The efficacy of coatings treatments was between 88.06 and 96.68% compared to the control treatment. Sensory analysis showed that the OEO did not affect the quality attributes of coated mango. Results showed the potential benefits of applying the pectin-based coatings with OEO as an alternative to control S. enterica and C. gloeosporioides in whole mangoes.

Terroir Is the Main Driver of the Epiphytic Bacterial and Fungal Communities of Mango Carposphere in Reunion Island.

The diversity of both bacterial and fungal communities associated with mango surface was explored using a metabarcoding approach targeting fungal ITS2 and bacterial 16S (V3-V4) genomic regions. Fruits were collected in Reunion Island from two different orchards according to a sampling method which allowed the effect of several pre-harvest factors such as geographical location (terroir), cultivars, fruit parts, tree position in the plot, fruit position on the tree (orientation and height), as well as the harvest date to be investigated. A total of 4,266,546 fungal and 2,049,919 bacterial reads were recovered then respectively assigned to 3,153 fungal and 24,087 to bacterial amplicon sequence variants (ASVs). Alpha and beta diversity, as well as differential abundance analyses revealed variations in both bacterial and fungal communities detected on mango surfaces depended upon the studied factor. Results indicated that Burkholderiaceae (58.8%), Enterobacteriaceae (5.2%), Pseudomonadaceae (4.8%), Sphingomonadaceae (4.1%), Beijerinckiaceae (3.5%), and Microbacteriaceae (3.1%) were the dominant bacterial families across all samples. The majority of fungal sequences were assigned to Mycosphaerellaceae (34.5%), Cladosporiaceae (23.21%), Aureobasidiaceae (13.09%), Pleosporaceae (6.92%), Trichosphaeriaceae (5.17%), and Microstromatales_fam_Incertae_sedis (4.67%). For each studied location, mango fruit from each cultivar shared a core microbiome, and fruits of the same cultivar harvested in two different locations shared about 80% fungal and bacterial family taxa. The various factors tested in this study affected bacterial and fungal taxa differently, suggesting that some taxa could act as geographical (terroir) markers and in some cases as cultivar fingerprints. The ranking of the factors investigated in the present study showed that in decreasing order of importance: the plot (terroir), cultivar, fruit parts, harvest date and the position of the fruits are respectively the most impacting factors of the microbial flora, when compared to the orientation and the fruit position (height) on the tree. Overall, these findings provided insights on both bacterial and fungal diversity associated with the mango surface, their patterns from intra-fruit scale to local scale and the potential parameters shaping the mango microbiota.

New Bacterial Agents to Limit &amp;lt;i&amp;gt;Colletotrichum gloeosporioides&amp;lt;/i&amp;gt; Development on Mango

Mango anthracnose disease forms typical irregular-shaped black necrotic spots on the fruit peel of mature fruit and is caused by Colletotrichum gloeosporioides. In order to improve the disease control with a limited use of fungicides, new microbial agents able to limit the growth of the pathogen were searched in the indigenous natural flora of mango surface. In order to find a suitable biocontrol agent, a screening was applied to 305 epiphytic bacteria isolated from the carposphere of 17 mango cultivars sampled from eight locations on Reunion Island. The screening approach involved a first step based on the ability of the isolates to form a biofilm, to grow under fruit storage conditions, and to interfere with the development of C. gloeosporioides. In a second step, the capability of selected isolates to limit C. gloeosporioides in vitro mycelial growth and conidia germination was assessed and species identified. The most effective bacteria belonged to the Enterobacter, Pantoea, Kosakonia and Leuconostoc genera, but for some of them, their safe use has to be demonstrated. Efficacy in vivo, performed on wounded mature mango fruit, was limited, probably because of the wounding inoculation strategy favoring the pathogen. Future biocontrol treatments should focus on preharvest applications to enhance the protective benefit.

Effect of Chitosan- and Alginate-Based Coatings Enriched with Cinnamon Essential Oil Microcapsules to Improve the Postharvest Quality of Mangoes.

During this study, fresh mangoes were packed into multilayer coatings made from chitosan containing cinnamon essential oil microcapsules and alginate solutions that were alternately deposited on the mango surfaces by electrostatic interaction. We then compared the physical and chemical indexes to examine the changes in the mangoes during 14 d of storage. The results showed that the microcapsules prepared in the experiment were of uniform size, with the sustained release of essential oil exceeding 168 h. Compared with uncoated mangoes, the mangoes coated with the coatings could effectively inhibit the decrease of the titratable acid, soluble solids, and vitamin C contents; slow down the increase of the weight loss and pH; delay the appearance of mango respiration peaks; and preserve the firmness at storage conditions of 25 °C and 50% RH. Our findings revealed that mangoes without treatment showed losses in their edible and commercial value after 14 days in storage, and the mangoes coated with five layers still retained food and commercial value. Cross-sectional scanning electron microscopy images of the coatings showed that they had distinct layers and were of good uniformity and tight binding, and they also had good adhesion to the mango surface. These findings provide important insights into the use of coatings for the packaging of fruits during storage, which is essential for promoting the application of coatings for packaging preservation without big cost and expensive equipment.

Potential of reflected UV imaging technique for detection of defects on the surface area of mango.

Surface defects such as mechanical damage, black lesion, latex stains and shriveling of mango fruit are very common and responsible for lowering of market prices as well as postharvest losses. Current research, thus, focused on the study of reflected ultraviolet imaging (UV) technique, its potential of detecting defected mangoes and to develop a computer vision system which could find the reflected area on injured or defected mango's surface. The visual visualization of the bruised areas was noticed different when viewed under 15W fluorescent UV tube (100-400nm) light by UV camera. Hidden defects on fruit's surface detected just after the image acquisition by UV camera and brightness enhancement. Defected or injured surface of mangoes recognized easily by reflected UV imaging at 400nm band-pass filter. The seriousness of injuries which were not detected by RGB color camera, detected by reflected UV imaging technique exactly.

Mechanisms of action of the yeast Debaryomyces nepalensis for control of the pathogen Colletotrichum gloeosporioides in mango fruit

The yeast Debaryomyces nepalensis was evaluated for effectiveness against Colletotrichum gloeosporioides in mangoes (Mangifera indica L.) cv. ‘Tainong No. 1’, and possible mechanisms of action involved in the inhibition were identified. The results showed that D. nepalensis could survive in mango wounds and produce a hydrolytic enzyme (β-1,3-glucanase). Scanning electron microscopy showed that the yeast produced biofilms on the mango surface and yeast cells attached to each other and became embedded in the pathogen hyphal walls. In addition, D. nepalensis competed for nutrients (FeCl3) and competed for space with the pathogen (p < 0.05). Morever, D. nepalensis enhanced defense-related enzymes of wounded mangoes, including peroxidase, β-1,3-glucanase, chitinase and phenylalanine ammonia-lyase. In addition, gas chromatographic-mass spectrometry (GC–MS) analysis of volatile compounds (VOCs) produced by the yeast showed that VOCs can play important roles over short distances in the suppression of C. gloeosporioides. The solid-phase microextraction (SPME) coupled with GC–MS technique analysis revealed phenylethyl alcohol (29.62% relative peak area, RA) as the dominant VOC mainly produced by D. nepalensis, and it had a significant inhibitory effect on fungal mycelia. According to the results obtained here, the combination of different mechanisms of action of the yeast increases their ability to control C. gloeosporioides. The use of antagonistic yeast to control C. gloeosporioides may contribute to the integrated management of disease caused by this pathogen.

Rapid Prediction of Microbial Load on Intact Mango Surface Using Spectroscopy

Agriculture industries are continuously in search of new user friendly techniques for evaluating overall quality(microbial and biochemical) of fruits as per quarantine requirements. In the current study, the potential of visibleand near-infrared (NIR) spectroscopy in the wavelength range of 299-1100 nm and 900-1700 nm was evaluatedto determine total microbial population on the surface of seven major cultivars of mangoes collected from fourstates of India. NIR models were developed based on multiple-linear regression (MLR) and partial least square(PLS) regression employing pre-processing technologies (baseline correction, smoothening, multiplicative scattercorrection (MSC) and second-order derivatives). Wavelength range of 299-1100 nm was found to be more suitablefor determination of microbial load on the mango surface as compared to wavelength range of 900-1700 nm.PLS models were found to be the best with multiple correlation coefficients of 0.66 and 0.56, for calibration andvalidation, respectively, in the wavelength range 504.80-533.17 nm. The standard errors of calibration, predictionand differences in them were low, which demonstrated the potential of NIRS to predict microbial load on the surfaceof mango non-destructively in the wavelength range of 504.806-533.176 nm.

Estimation of total bacteria on mango surface by using ATP bioluminescence

This paper presents a rapid ATP assay for monitoring the total bacterial load associated with mango fruit surface. Conventional methods such as total plate count for the determination of total microbial counts are time consuming and prone to contamination resulting in low accuracy. Thus the need for quick and accurate methods for determination of total microbial count has led to development of many rapid techniques such as ATP bioluminescence. In this study the potential of ATP bioluminescence method for the determination of total bacterial count on mango surface has been evaluated using two types of luminescence techniques based on fluorescence spectroscopy and bioluminescence. Various mechanical and chemical extraction processes were employed for the extraction of ATP from bacterial cells and the best extraction was achieved with 0.03M TCA. Minimum level of detection of ATP using fluorescence spectrophotometer and bioluminometer was found to be 10−8M and 10−13M, respectively. This ATP concentration was correlated with the number of bacterial cells present on mango surface. The minimum level of detection of bacterial cells in fluorescence spectroscopy and bioluminescence was found to be 107cfu/ml and 102cfu/ml, respectively.

Influence of collapsed structure on stability of β-carotene in freeze-dried mangoes

This study aimed to investigate the effect of structural collapse of freeze-dried mangoes on stability of β-carotene. Three different freeze-drying protocols were performed to produce collapse and non-collapse structures of freeze-dried mangoes. Thermal transitions of samples were determined using a differential scanning calorimeter. β-carotene content was monitored during storage using high-performance liquid chromatography. The β-carotene degradation followed first-order kinetics. Mangoes freeze-dried at above ice melting temperature revealed structural collapse which decreased β-carotene degradation rate. These dense and collapsed structures formed prevented oxygen penetration through the solids. Liquid nitrogen freezing also gave structural collapse coincided with surface cracking on freeze-dried mangoes. Such structure showed no protective effect on β-carotene as similar degradation rate to non-collapsed systems was observed. The cracking on mango surface potentially allows high oxygen penetration through the solids thus promoting β-carotene loss. These findings give benefit to the production of freeze-dried fruits to increase storage stability of β-carotene.

Post-harvest micro-flora on major cultivars of Indian mangoes

This study examined the surface micro-flora on nine major mango varieties collected from nine states of India in three different harvesting stages (early, mid and late). Mango surface supported substantial microbial component, including various species of bacteria, filamentous fungi and yeasts. Total microbial population was in the range of 10 5–10 8 and was significantly different in different cultivars as well as harvesting stages. However, all the mango varieties invariably showed highest microbial population in third harvesting stage. Comparative microbial population of yeast, mold and bacteria showed significant variation in different mango varieties at the third harvesting stage except for Alphonso from Maharashtra and Karnataka. Microbial population on mango fruit surface was strongly influenced by climatic factor, stages of fruit development and varietal specificity.

EFFECT OF THE LACTOPEROXIDASE SYSTEM AGAINST CAUSAL AGENTS OF POST HARVEST MANGO DISEASES

The purpose of our study was to evaluate the effect of the lactoperoxidase system (LPS) on fungus Colletotrichum spp. responsible of mango alterations as well as on the quality of the fruit storage. In vitro study using LPS showed a negative effect on the growth of Colletotrichum spp. selected and isolated from mango. This fungus was grown at pH 5,5 with optimised culture medium at 30°C. We found that the LPS was able to inhibit its growth with the best efficacy at this pH. Following the in vitro study, the LPS effect was directly evaluated on fresh mangoes of KEITT variety. The mangoes were soaked in the LPS solution at 35°C. The bacterial charge on the mango surface was cut down in comparison to the reference, after 120 min at 35°C However, after two or three weeks storage at 12°C and 80% relative humidity, the mangoes treated at 35°C (120 min) were not significantly different the reference ones. Finally, we studied the LPS effect on the mangoes of KEITT variety, which were infected by the in vitro selected fungus. We observed that the soaking treatment in the LPS solution at 35°C for 120 min decreased the disease symptom in respect to the references. These results clearly showed the interest of LPS treatment for the storage of fresh mangoes. Nevertheless, further studies should be carried out to consider an industrial application. (Resume d'auteur)

Forced Hot-Air Quarantine Treatment for Mangoes Infested with West Indian Fruit Fly (Diptera: Tephritidae)

Quarantine efficacy for mangoes against the West Indian fruit fly, Anastrepha obliqua (Macquart), was demonstrated using a forced hot-air system. Extrapolation from the probit model fitted to preliminary experimental data indicated a 99.9968% mortality at pulp temperature of 48.1°C. The probit analysis showed that goodness-of-fit was poor, but that this was caused by large errors at the lower temperatures rather than systematic departure from the model. We killed an estimated 109,839 larvae with no survivors in 2,221 mangoes giving >97% confidence that the mortality was greater than the probit 9 level. By running air temperature at 50°C, air speed at about 0.4 m3/s, and increasing humidity at a rate such that the dew point was always at least 2°C lower than the mango surface temperature, we were able to heat :the mangoes at a rapid rate without surface scald or other phytotoxic effects. We recommend that mangoes be heated until seed-surface temperatures reach 48°C and that air temperatures, air speeds, load sizes, and other factors determining rate of heating be determined for individual commercial systems. In our confirmatory tests, treatment time ranged from 101 to 213 min depending on mango sizes and numbers of boxes treated. Consumer panels, in the laboratory and made up of the public, found no difference in taste, odor, or overall acceptability but frequently judged treated mangoes superior to controls for appearance factors. Position of mangoes in the chamber was frequently a significant factor in panel ratings. More even heat distribution by such means as a reversible fan system may decrease this variation.