Climacteric Fruit Research Articles

Identification and Profiling Analysis of microRNAs in Guava Fruit (Psidium guajava L.) and Their Role during Ripening.

The guava (Psidium guajava L.) is a climacteric fruit with an accelerated post-harvest overripening. miRNAs are small RNA sequences that function as gene regulators in eukaryotes and are essential for their survival and development. In this study, miRNA libraries were constructed, sequenced and analyzed from the breaker and ripe stages of guava fruit cv. Siglo XXI. One hundred and seventy-four mature miRNA sequences from 28 miRNA families were identified. The taxonomic distribution of the guava miRNAs showed a high level of conservation among the dicotyledonous plants. Most of the predicted miRNA target genes were transcription factors and genes involved in the metabolism of phytohormones such as abscisic acid, auxins, and ethylene, as revealed through an ontology enrichment analysis. The miRNA families miR168, miR169, miR396, miR397, and miR482 were classified as being directly associated with maturation, whereas the miRNA families miR160, miR165, miR167, miR3930, miR395, miR398, and miR535 were classified as being indirectly associated. With this study, we intended to increase our knowledge and understanding of the regulatory process involved in the ripening process, thereby providing valuable information for future research on the ripening of guava fruit.

Flexible waterborne polyurethane nanocomposite foams incorporated with halloysites as fresh-keeping packaging inserts for fresh fruits

Food losses due to the deterioration of fresh fruits and related economic problems can be prevented by the use of active food packaging materials. Here, waterborne polyurethane (WPU)/halloysite nanotube (HNT) nanocomposite foams with ethylene and moisture absorption properties are presented, which can be inserted into existing food packages as fresh-keeping packaging materials for the improvement of the shelf life of fruits. WPU with moisture absorption properties has been utilized as a carrier for HNTs, which have a large capacity to absorb ethylene gas, the plant hormone responsible for the ripening of climacteric fruits. HNTs were incorporated into WPUs during a foaming process, resulting in open-cell foams with average pore sizes of 316 µm and a density of 0.136 g/cc. The resulting WPU-HNT foams were shown to absorb moisture by 7 % when they were incubated in a closed container of 100 % relative humidity for 14 days. The WPU-HNT foams were also demonstrated to absorb 2.5 ppm of ethylene gas per gram of foam when kept in a sealed container injected with 90 ppm ethylene gas for 3 days. Tomatoes stored together with the nanocomposite foams in plastic boxes at 4 °C for 14 days presented significantly higher firmness values than the tomatoes stored without the foams. Similarly, bananas stored in polyethylene bags containing the nanocomposite foam remained firmer and free of brown spots for at least 2 days longer than the bananas stored without the nanocomposite foam. The WPU-HNT foams have a strong potential as low-cost, environmentally friendly food packaging inserts that can prevent spoilage of fruits.

Effect of Postharvest Treatments on Physiological, Chemical, Microbial and Sensory Qualities of Fruits of Papaya Variety Surya

Background: Papaya is a climacteric fruit which is highly perishable due to rapid ripening and softening and susceptibility to biotic or abiotic stresses, resulting in large losses during storage. Traditionally, people resort to the application of synthetic chemical fungicides on to the crop plant and to the fruits during storage, to control the anthracnose caused by the fungus Colletotrichum gloeosporioides on fruits. But their repeated use has caused resistance in microorganisms and toxicity for humans. Hence, nowadays there has been increasing interest in using natural alternatives instead of chemical treatment. Methods: Fruits of papaya variety Surya collected at fully mature green stage were subjected to different postharvest management practices namely precooling, surface sanitization, treatment with chitosan and were packaged in corrugated fibre board boxes and stored till the end of shelf life under ambient condition. Untreated fruits (control) were also used in the study. Result: Fruits coated with chitosan (1%) registered an improved shelf life of 6.33 days as against 4.33 days in control in ambient storage and it further improved the sensory score for all the organoleptic parameters, after six days of storage. 1% chitosan coating also reported significantly lowest physiological loss in weight (3.51 %), ion leakage (60.47%), total soluble solids (12.13 °Brix), total carotenoids (2.34 mg 100g-1), total sugar (7.26%) and reducing sugar (6.34%) and least disease index (16.67%), bacterial count (22.33 cfu/ml × 106) and fungal count (7.33 cfu/ml × 103) after three days of storage when compared with control.

Quality management in the import and sale of tropical and subtropical fruits

An analysis of the dynamics of the market for fruits imported to Russia has been carried out. The market volume, exporters, and sales volume of tropical fruits in Russia have been studied. The factors shaping the quality of tropical fruits are considered. When ensuring logistics, customs clearance, and storage in distribution centers, it is necessary to take into account the actual degree of maturity of climacteric fruits and manage technological regimes at all stages of product distribution, with regard to the physiological state of the product. The work studies the influence of temperature conditions of storage and ripening of avocado fruits on the duration of storage of fruits and the intensity of the processes responsible for their ripening. The values of respiration intensity and ethylene concentration during storage of avocado fruits, which make it possible to determine the degree of ripeness of the fruit and control the duration of their storage, have been established.

Dynamic shifts in primary metabolism across fruit development stages in Capsicum chinense (cv. Habanero)

The development of fleshy fruits involves changes in size and mass, followed by cell differentiation, which is associated with anatomical and histological changes. Parallel to these changes, metabolic alterations lead to the production of osmolytes and energy that modify cell turgor pressure, thereby promoting cell expansion and fruit growth. Detailed information is known about these processes in climacteric fruits (e.g. tomato); however, the regulation of metabolism and its association with anatomical changes in non-climacteric fruit development are poorly understood. In this study, we used detailed anatomical and histological analyses to define three developmental phases of chili pepper (Capsicum chinense cv. Habanero): cell division, cell expansion, and ripening. We showed that each was marked by distinct metabolic profiles, underpinning the switches in energy metabolism to support cellular processes. Interestingly, mitochondrial activity was high in the early stages of development and declined over time, with a modest increase in O2 consumption by pericarp tissues at the beginning of the ripening stage. This respiratory-like burst was associated with the degradation of starch and malate, which are the sources of energy and carbon required for other processes associated with fruit maturation.

Preservation of Quality and Bioactive Compounds in Mangoes Using Chitosan-Graphene-Oxide-Based Biodegradable Packaging

Mango is a climacteric fruit that requires efficient postharvest technologies to maintain quality during storage and transportation. This study aimed to investigate the effect of biodegradable packaging from chitosan (CS) incorporated with graphene oxide (GO) on the quality, bioactive compounds and antioxidant activity of cold-stored ‘Tommy Atkins’ mangoes. Mangoes harvested at physiological maturity were stored without packaging or in CS, CS-GO or non-biodegradable polyethylene (PE) packaging at 12.0 °C and 89% relative humidity for 42 days. The results show that GO improved the water barrier and mechanical properties of CS packaging. All packaging delayed fruit ripening by reducing the respiration rate, mass loss, softening and changes in color, soluble solids, titratable acidity and beta-carotene content, also preserving the mangoes’ visual appearance. In addition, all packaging maintained higher ascorbic acid, yellow flavonoid, phenolic compounds and antioxidant activity levels in the fruit, compared to non-packed ones. Chitosan packaging is a promising, eco-friendly alternative for the preservation of quality, bioactive compounds and antioxidant activity of cold-stored ‘Tommy Atkins’ mangoes, extending their postharvest life by at least 14 days.

A hydroxypropyl methylcellulose (HPMC)-based coating inhibits ethylene-dependent quality changes and reduces superficial scald incidence and blue mould severity during postharvest handling of two apple varieties

The search of new alternatives to substitute postharvest treatments based on synthetic chemicals has gained attention on recent years due to social pressure and stricter legislative policies. Consequently, edible coatings from natural sources have risen as potential solutions to retain postharvest fruit quality. Among these, coatings based on hydroxypropyl methylcellulose (HPMC) have shown potential in preserving fruit quality after harvest. However, scarce studies have explored into their effects on the physiology of climacteric fruits. In this context, the effect of a novel HPMC-based edible coating on fruit postharvest physiology and quality was evaluated in two apple cultivars: ‘Golden Reinders’ and ‘Granny Smith’. In both cultivars, the HPMC-based coating was able to preserve some initial quality attributes, such as firmness and colour, while reducing superficial scald and the severity of blue mould caused by Penicillium expansum. Coated fruit showed reduced ACS activity and ethylene production, delaying changes in ethylene-dependent parameters such as colour and firmness during two different postharvest scenarios: shelf life after harvest and after 3 months of cold storage. Other ripening-associated traits such as starch index, soluble solids content (SSC), and total titratable acidity (TTA) were not affected by the coating application. The coating altered the levels and composition of volatile organic compounds (VOCs), yet without affecting the overall consumer acceptance in most of the studied scenarios. Changes in fruit physiology promoted by the coating, including the decrease of α-farnesene levels and its oxidation products, together with enhanced accumulation of ethanol may reduce the superficial scald incidence in ‘Granny Smith’ and the severity of blue mould rot in the two studied cultivars. Overall, the use of the HPMC-based coating in apples could be useful for maintaining fruit quality and reducing postharvest losses related to mould development and physiological disorders without compromising taste perception.

Pengaruh Arang Aktif Bidara dalam Menunda Kematangan Buah Klimakterik Tomat (Solanum lycopersicum)

Tomato (Solanum lycopersicum) is classified as a climacteric fruit that is easily damaged, especially during the storage and shipping process, so proper postharvest management is needed. Postharvest management of climacteric fruit can be overcome by inhibiting the process of respiration and transpiration using activated charcoal. Activated charcoal works by absorbing ethylene gas during the respiration process. This study aims to analyze the use of bidara activated charcoal variations as an inhibitor of tomato ripeness and to examine changes in fruit quality during the 10day storage. The research used One Way Anova analysis with one factor of variation of activated charcoal with control treatment, 1gr, 3gr, and 5gr. Parameters tested were weight loss, Total Soluble Solid, and vitamin C. The use of bidara activated charcoal on tomatoes got the best results in the 5gr treatment with a weight loss value of 0.46%, 0.10 obrix total dissolved solids, and 18.93% vitamin C. Bidara activated charcoal had an effect on weight loss and total soluble solids but had no effect on vitamin C content. Bidara wood activated charcoal can be developed into an absorbent material for tomatoes.

Postharvest Melatonin Application Preserves Quality and Imparts Chilling Tolerance in Peaches

Peach being a climacteric fruit has a limited shelf life. Cold storage of peaches is an essential measure to maintain their quality. However, prolonged exposure to cold temperatures causes chilling injury in peaches, resulting in significant economic losses. Approximately, 40% of the produced commodity is lost in postharvest handling in which chilling injury contributes to about 25%. Melatonin can be a green solution and plays a key role in protecting peaches from chilling injury. Therefore, this experiment aimed to determine the effect of melatonin on the “Silver King” peaches by dipping them in 100 μM melatonin for 2 hours followed by storing them at chilling temperatures of 2 ± 1°C and 90–95% relative humidity for 21 d. The results showed that while control fruit experienced chilling injury and poor fruit quality, increased respiration rate, and enhanced senescence, 100 μM melatonin treatment was successful in preserving the fruit quality at chilling temperatures and was associated with the delayed respiration rate and lower malondialdehyde levels, along with the preservation of certain physicochemical parameters, namely, total soluble solids, pH, fruit firmness, and titratable acidity. Moreover, a 1.5 times higher proline concentration was observed in melatonin-treated peaches when compared to that of nontreated peaches. This rise was linked to the enhanced activity of Δ1-pyrroline-5-carboxylate synthetase and ornithine-δ-aminotransferase along with a decrease in the activity of proline dehydrogenase during 21 d of storage.

Beeswax: A review on the recent progress in the development of superhydrophobic films/coatings and their applications in fruits preservation.

Recently, the design and fabrication of bio-inspired superhydrophobic materials using natural lipid additives such as beeswax (BW) have aroused great attention in food packaging as they can minimize the transfer rate of water molecules and have effective moisture barriers. This review discusses the recent progress in the design and fabrication of BW-containing edible films/coatings (e.g., emulsion and blend films, bilayer materials, bionanocomposites, and antimicrobial materials) and their potential applications on the postharvest life and quality attributes of various fruits. Incorporation of BW into polysaccharides- and proteins-based emulsion films effectively improved their hydrophobicity, water vapor, and UV/visible light barrier properties, as well as the film tensile properties. The addition of nanoparticles to BW-based polymeric matrices often results in improved physico-mechanical properties. BW coatings have been also applied to prolong the shelf-life of various climacteric fruits, however, optimization of the wax concentration can be further investigated to develop targeted food storage systems.

Characterization of MicroRNAs and Gene Expression in ACC Oxidase RNA Interference-Based Transgenic Bananas.

Banana (Musa acuminata, AAA group) is a typically respiratory climacteric fruit. Previously, genes encoding ACC oxidase, one of the key enzymes in ethylene biosynthesis, Mh-ACO1 and Mh-ACO2 in bananas were silenced individually using RNAi interference technology, and fruit ripening of transgenic bananas was postponed. Here, the differential expression of miRNAs and their targeted mRNAs were analyzed in the transcriptomes of fruits at the third ripening stage, peel color more green than yellow, from the untransformed and RNAi transgenic bananas. Five significantly differentially expressed miRNAs (mac-miR169a, mac-miR319c-3p, mac-miR171a, mac-miR156e-5p, and mac-miR164a-5p) were identified. The predicted miRNA target genes were mainly enriched in six KEGG pathways, including 'sulfur relay system', 'protein digestion and absorption', 'histidine metabolism', 'pathogenic E. coli infection', 'sulfur metabolism', and 'starch and sucrose metabolism'. After ethylene treatment, the expression of ACC oxidase silencing-associated miRNAs was down-regulated, and that of their target genes was up-regulated along with fruit ripening. The evolutionary clustering relationships of miRNA precursors among 12 gene families related to fruit ripening were analyzed. The corresponding expression patterns of mature bodies were mainly concentrated in flowers, fruits, and leaves. Our results indicated that ethylene biosynthesis is associated with miRNAs regulating the expression of sulfur metabolism-related genes in bananas.

A carrageenan-based edible coating incorporating with peppermint essential oils to increase shelf life of bananas (Musa acuminata cavendish)

Ambon bananas (Musa acuminata cavendish) are nutritious and economically valuable fruits. Bananas, being a climacteric fruit, have the potential to undergo deterioration subsequent to the harvesting process. The utilization of an edible coating on bananas has demonstrated potential in delaying spoilage, whereas the substantial use of peppermint oil has been observed in the preservation of fruit freshness. This research investigated how a carrageenan-based coating and peppermint essential oil enhance banana shelf life. This research compares uncoated bananas, carrageenan-coated bananas, and carrageenan-peppermint-coated bananas. Weight loss, total soluble solids (TSS), pH, colour, and water activity were tested. In this study, it was observed that the application of a carrageenan edible coating resulted in a reduction in weight loss and TSS as compared to bananas that were not coated. Duncan's test shows statistically significant discrepancy in weight loss among bananas that have undergone different treatments, thereby influencing the overall weight loss outcome. There are variations in pH levels and aw values. Meanwhile, pH and water activity of coated and uncoated bananas were relatively the same and stable during storage, so the carrageenan edible coating treatment and the addition of peppermint essential oil had no effect. The findings indicate that edible coatings made from carrageenan have the ability to inhibit the ripening process of bananas. Nevertheless, the efficacy of this inhibition decreases when peppermint essential oil is given as a supplementary constituent.

Effect of different active packaging materials on storage of persimmon cv. Fuyu

Persimmon is a high value climacteric fruit and deteriorate rapidly after harvest. Therefore, an investigation on extending storage life of persimmon fruits using active packaging technology was done with the following treatments viz., T1 (Control), T2 (Cloth bag + 3g activated charcoal), T3 (Non-woven pp bag + 3g Activated charcoal), T4 (Butter paper bag + 3g Activated charcoal), T5 (Polypropylene + 3g Activated charcoal), T6 (Cloth bag + 6g KMnO4), T7 (Non-woven pp bag + 6g KMnO4), T8 (Butter paper bag + 6g KMnO4) and T9 (Polypropylene + 6g KMnO4). These were stored at 4±1°C and 85-90% RH and analyzed for different physiochemical properties at 10-day intervals. Polypropylene packaging with 3g Activated charcoal or 6g KMnO4 resulted in the longestshelf life and good quality fruits at more than 50 days of storage. Modified packaging with polypropylene + 3g Activated charcoal preserved fruit firmness, greater β-carotene content in pulp and lowest PLW (%), while fruits packed in Polypropylene + 6g KMnO4 resulted in the highest pH, ascorbic acid, peel β-carotene and pectin content and lowest TSS, total and reducing sugar content. The highest BCR amongst various treatment combinations was found in fruits packaged in Polypropylene + 6g KMnO4 on the 70th day of storage

Effect of 1-methylcyclopropene on jackfruit with marketing simulation at 8°C

Jackfruit is a tropical fruit and competes with traditional crops such as mango, banana, and pineapple with regard to the quantity exported from the state of Nayarit, Mexico. Because jackfruit is a climacteric fruit with a high respiration rate and ethylene production, it has a limited market due to its short shelf life. The effect of the application of 1-methylcyclopropene (1-MCP) post-harvest to extend the shelf life of jackfruit was studied. Physiologically mature fruits were used and 1-MCP was applied at concentrations of 300, 600, and 1000 nL·L−1; control fruit without treatment was also evaluated. The fruits were stored for 5 days at 8°C and then were stored at 25°C to simulate the commercialization of the fruit. An absolute control group stored permanently at 25°C was used. The following analyses were carried out: physiologic and physicochemical factors, antioxidant capacity, vitamin C, total carotenoids, total soluble phenols, and sensory evaluation of the fruits when ripe. The climacteric peak for the absolute controls and fruit treated with 1-MCP (300, 600, and 1000 nL·L−1) occurred on days 3, 14, 17, and 17 respectively, prolonging the climacteric peak by an average of 13 days. The maximum rates of ethylene production were reported on days 3, 15, 17, and 17 in the same order, prolonging this by an average of 13 days. The treatment with 1-MCP (600 nL·L−1) extended the shelf life of jackfruit by 9 days compared with the absolute control, preserving the physicochemical, phytochemical, and sensory characteristics for up to 17 days of storage, confirming that the application of 1-MCP post-harvest is effective, providing the opportunity to increase the export destinations of Mexican jackfruit.
 Keywords: Jackfruit; 1-Methylcyclopropene; Marketing conditions; Physiologic and physicochemical parameters; Total soluble phenols; Antioxidant capacity

MaMADS1-MaNAC083 transcriptional regulatory cascade regulates ethylene biosynthesis during banana fruit ripening.

The hormone ethylene is crucial in the regulation of ripening in climacteric fruit, such as bananas. The transcriptional regulation of ethylene biosynthesis throughout banana fruit ripening has received much study, but the cascaded transcriptional machinery of upstream transcriptional regulators implicated in the ethylene biosynthesis pathway is still poorly understood. Here we report that ethylene biosynthesis genes, including MaACS1, MaACO1, MaACO4, MaACO5, and MaACO8, were upregulated in ripening bananas. NAC (NAM, ATAF, CUC) transcription factor, MaNAC083, a ripening and ethylene-inhibited gene, was discovered as a potential binding protein to the MaACS1 promoter by yeast one-hybrid screening. Further in vitro and in vivo experiments indicated that MaNAC083 bound directly to promoters of the five ethylene biosynthesis genes, thereby transcriptionally repressing their expression, which was further verified by transient overexpression experiments, where ethylene production was inhibited through MaNAC083-modulated transcriptional repression of ethylene biosynthesis genes in banana fruits. Strikingly, MaMADS1, a ripening-induced MADS (MCM1, AGAMOUS, DEFICIENS, SRF4) transcription factor, was found to directly repress the expression of MaNAC083, inhibiting trans-repression of MaNAC083 to ethylene biosynthesis genes, thereby attenuating MaNAC083-repressed ethylene production in bananas. These findings collectively illustrated the mechanistic basis of a MaMADS1-MaNAC083-MaACS1/MaACOs regulatory cascade controlling ethylene biosynthesis during banana fruit ripening. These findings increase our knowledge of the transcriptional regulatory mechanisms of ethylene biosynthesis at the transcriptional level and are expected to help develop molecular approaches to control ripening and improve fruit storability.

Edible Coating Formulated by Optimization from Aloe vera, Starch, and Arabic Gum Improved the Conservation of Banana (Musa acuminata) Fruits.

Banana is a very perishable climacteric fruit with consequence of large postharvest losses. The objective of the present study was to improve the postharvest shelf life of bananas. Fruits from the Melong locality were treated with coating solutions formulated with a mixture of Aloe vera, starch, and Arabic gum at different concentrations. These concentrations were obtained using the response surface methodology in order to establish the relationship between independent variables (ripening parameters) and dependent variable (Aloe vera, starch and Arabic gum), which led to the generation of experimental design as well as the prediction of result model. The effects of the coating solutions were evaluated on firmness, percentage of ripening, weight loss, chlorophyll a, chlorophyll b, and total soluble solid contents. The results showed that the combination of Aloe vera, starch, and Arabic gum extended the shelf life of banana by slowing down the chlorophyll degradation, the loss of firmness, the weight loss, and the synthesis of total soluble solids. The coefficients of determination (R2) of the responses were all above 80% indicating that the experimental data fit well with the predicted responses. The interactions that influenced most of the responses were those between Aloe vera-starch and Aloe vera-Arabic gum. The optimum concentrations obtained for the mixture of the final solution were 286.799 ml.l-1 (v/v), 102.589 g.l-1 (m/v), and 1.0888% (m/v) for Aloe vera, starch, and Arabic gum, respectively.

Prevalent Variability among Jackfruit Genotypes: An Assessment on Fruit and Flake Characteristics

Jackfruit (Artocarpus heterophyllus Lam) belongs to the family Moraceae is a tropical climacteric fruit and known to be the world’s largest edible fruit. Tropical Asia is regarded as origin of jackfruit. India is considered as the mother land of jackfruit with the production of 1.4 million tonnes per year. All parts of jackfruit is consumable, the flesh of jackfruit in unripen stage can be used as vegetable and in fully ripen stage can be used as fruit. Seeds can be used for making curries. Jackfruit bulbs are rich in sugars and contain fair amounts of carotene, protein and minerals. Jackfruit is rich in dietary fiber, which makes it a good bulk laxative. Jacalin content present in seeds has anti-cancer abilities. Finding a jackfruit genotype with high nutritional composition is highly recommended. An experiment was conducted during the year 2022-2033 at Department of Fruit Science, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Periyakulam. Biometric parameters of 25 jackfruits genotypes, collected from diverse locations were evaluated for variations observed in their morphological features and sensory attributes. The results showed that AH 2, AH 7, AH 11 genotypes sampled from Theni, Cuddalore, Pondicherry district exhibited impressive results with high recovery percentage and proved to be economical in comparison to other genotypes. Based on flake quality AH 2 found to be suitable for table purpose and AH 7, AH 11 for culinary purpose. These findings will come handy in studying the variation among genotypes for future hybridization programme to develop superior varieties.

Effect of Ethrel Concentration on Avocado Fruit Running (Persea americana mill)

Avocado is a climacteric fruit, which is usually harvested when it is still unripe. One way to accelerate the maturity of climacteric fruit is by ripening. Ripening treatment with ethrel can accelerate fruit ripening. This study aims to determine the effect of proper ethrel concentration on the avocado ripening process. The experimental design used was RAL (Completely Randomized Design) 1 Factor with 5 treatments and 4 replications. The treatment consisted of P0 control without ethrel treatment, then added ethrel solution P1 = 0.25 ml/L, P2 = 0.50 ml/L, P3 = 0.75 ml/L and P4 = 1.00 ml/L. Variables observed included weight loss, color, texture/hardness, water content, total dissolved solids and fat content. The data obtained were analyzed for variance and if there were significant differences in the treatment then it was further tested with Duncan's test at the 5% level. Based on the results of research on adding the right ethrel solution to the avocado ripening process found in P4 with the addition of 1.00 ml/L ethrel with a fat content of 15.34%, water content 88.99%, total dissolved solids 2.10 mg/L, texture 968.85grf, color 80.44 and weight loss 10.51%.

Effect of Edible Coatings of Cassava Starch Incorporated with Clove and Cinnamon Essential Oils on the Shelf Life of Papaya.

Applying edible coatings added with plant essential oils is a strategy used to delay ripening processes in climacteric fruits such as papaya. Formulations comprising 3% or 4% cassava starch (w/v), added with clove or cinnamon essential oils (2 mL/L), were tested for microbial inhibition (in vitro) purposes. Moreover, these fruits' physicochemical and microbiological aspects were assessed at 25 °C, for 12 days. Slight variations in pH and Brix values were observed during storage. On the other hand, there were no significant variations in carotenoid contents over storage time. The papaya fruits' coating contributed to reducing their weight loss from 40.66% (uncoated sample) to 24.10% on the 12th storage day, as well as delayed changes often observed during the ripening process. The 4% cassava starch coatings added with essential oils were more efficient in reducing microbiological levels. The herein proposed treatments reduced aerobic mesophilic bacteria, as well as molds and yeast counts, by 1.48 and 1.95 log CFU/g, on average, respectively, in comparison to the control sample. The assessed microorganism counts were higher in the uncoated sample than in the coated papaya fruits, after 12 days of storage. Thus, the tested coatings can potentially delay the emergence of post-harvest changes; consequently, they can help improve the quality of papaya fruits and extend their shelf life.

Effects of D-Limonene Nanoemulsion Coating on Post-Harvest Quality and Physiology of Papaya

Papaya (Carica papaya L.) is a climacteric fruit, and its quality will rapidly decrease after ripening. Hence, the storage life of its fruit is short. D-limonene is a terpene compound in citrus essential oil and has antibacterial and antioxidant properties. The addition of D-limonene in edible coating can delay volatilization, prevent microorganism and pathogen invasion, decrease water loss, inhibit softening, decrease gas exchange, and extend the storage life of fruits. In this study, 0.25%, 0.5%, and 1% D-limonene nanoemulsion coatings were used for post-harvest immersion treatment of “Tainung No. 2” papayas and its effects on appearance, chlorophyll content, respiration rate, ethylene production, pectin methylesterase, polygalacturonase activity, decay loss, firmness, total soluble solid, titratable acidity, ascorbic acid, and total plate count were investigated. After the papayas were treated with 0.5% D-limonene nanoemulsion coating, polygalacturonase and pectin methylesterase activities decreased, fruit firmness was maintained, and ascorbic acid content was high. On the last day of storage, polygalacturonase and pectin methylesterase activities were 0.01 and 0.02 U/kg FW lower than the control group, respectively; firmness was higher than the control group by 1.75 N, and ascorbic acid content was higher than the control group by 31.97 mg/100 g FW. On Day 2, the treatment showed delay in total soluble solid accumulation and chlorophyll degradation, consequently delaying the color change in fruits. The coating decreased decay loss by 40% on Day 2, decreased respiration rate by 97.0 mg CO2 kg−1 h−1, and ethylene production by 5.7 µL kg−1 h−1 on Day 2. Simultaneously, the coating decreased the total plate count and resulted in a good appearance. Fruits coated with a 1% D-limonene nanoemulsion coating showed defects in color change. In summary, 0.5% D-limonene nanoemulsion coating delayed “Tainung No. 2” papaya ripening and decreased microbial infection, consequently extending its storage life.