Control of anthracnose disease via increased activity of defence related enzymes in ‘Hass’ avocado fruit treated with methyl jasmonate and methyl salicylate

Development of anthracnose disease caused by Colletotrichum gloeosporioides Penz. is one of the major issues within the avocado supply chain. Exposure to methyl jasmonate (MeJA) and methyl salicylate (MeSA) vapours 10 and 100 µmol l-1 was investigated as an alternative solution to commercial fungicide - prochloraz® that is currently being used by the industry. The incidence of anthracnose disease was found to be significantly reduced in ‘Hass’ avocado fruit treated with MeJA or MeSA vapours, especially at 100 μmol l-1. The mechanism involved enhanced activity of defence related enzymes, i.e. chitinase, β-1,3-glucanase and PAL, and higher content of epicatechin

Optimisation of O2 and CO2 concentrations to retain quality and prolong shelf life of ‘shelly’ mango fruit using a simplex lattice mixture design

The experimental design and gas mixture selection is of great importance in the definition of optimal gas concentrations for use in storage of fresh produce. The aim of this study was to optimise O2 and CO2 concentrations under controlled atmosphere conditions to understand the effect on quality and shelf life of ‘Shelly’ mango fruit stored at 13 °C for 28 d. This was achieved by designing three experimental points (gas compositions = O2, CO2 and N2) using simplex lattice mixture design to (i) determine single and interaction effects of gas compositions on selected quality parameters and (ii) determine the optimal gas combination in order to maintain quality and prolonging shelf life of ‘Shelly’ mango fruit. The estimated model parameters coefficients successfully categorised the single and interaction effects of O2, CO2 and N2 gas compositions. The selected quality attributes experimental data was fitted well using the canonical Scheffe type special cubic model, resulting in coefficient of Determination, R2 = 0.70 to 0.97. The low O2 and high CO2 in CA-2 managed to retard ripening and mass loss, and reduce fruit softening and chlorophyll degradation. Positive relationship was observed for linear effect in all quality attributes, while binary and ternary interaction effects varied across all the treatments. The optimal gas compositions for storage of ‘Shelly’ mango fruit in terms of selected quality attributes ranged between 5 and 8% O2 + 5–9% CO2 + 86–91% N2. The results highlight the potential use of simplex lattice mixture design to optimise CA storage conditions

Chitosan, a Biopolymer With Triple Action on Postharvest Decay of Fruit and Vegetables: Eliciting, Antimicrobial and Film-Forming Properties

Chitosan is a natural biopolymer from crab shells that is known for its biocompatibility, biodegradability, and bioactivity. In human medicine, chitosan is used as a stabilizer for active ingredients in tablets, and is popular in slimming diets. Due to its low toxicity, it was the first basic substance approved by the European Union for plant protection (Reg. EU 2014/563), for both organic agriculture and integrated pest management. When applied to plants, chitosan shows triple activity: (i) elicitation of host defenses; (ii) antimicrobial activity; and (iii) film formation on the treated surface. The eliciting activity of chitosan has been studied since the 1990’s, which started with monitoring of enzyme activities linked to defense mechanisms (e.g., chitinase, β-1,3 glucanase, phenylalanine ammonia-lyase) in different fruit (e.g., strawberry, other berries, citrus fruit, table grapes). This continued with investigations with qRT-PCR (Quantitative Real-Time Polymerase Chain Reaction), and more recently, with RNA-Seq. The antimicrobial activity of chitosan against a wide range of plant pathogens has been confirmed through many in-vitro and in-vivo studies. Once applied to a plant surface (e.g., dipping, spraying), chitosan forms an edible coating, the properties of which (e.g., thickness, viscosity, gas and water permeability) depend on the acid in which it is dissolved. Based on data in literature, we propose that overall, the eliciting represents 30 to 40% of the chitosan activity, its antimicrobial activity 35 to 45%, and its film-forming activity 20 to 30%, in terms of its effectiveness in the control of postharvest decay of fresh fruit. As well as being used alone, chitosan can be applied together with many other alternatives to synthetic fungicides, to boost its eliciting, antimicrobial and film-forming properties, with additive, and at times synergistic, interactions. Several commercial chitosan formulations are available as biopesticides, with their effectiveness due to the integrated combination of these three mechanisms of action of chitosan

Comparison of the Contents of Bioactive Compounds and Quality Parameters in Selected Mango Cultivars

Mango cultivars Tommy Atkins, Zill, Peach, Sabre, Rosa and Phiva were analyzed for their quality parameters (fruit weight, flesh color chroma, L, h0, total soluble solid [TSS]/titratable acidity [TA], firmness), bioactive compounds (total phenols, carotenoids, ascorbic acid, antioxidant activity) and polyphenol oxidase (PPO) activity. Cv. Sabre showed highest total phenolic content (76.43 mg gallic acid/100 g FW), carotenoids (9.90 mg/100 g of FW), ascorbic acid content (69.71 mg/100 g of FW) and antioxidant activity (1.2 mg of gallic acid/g of FW), whereas cv. Peach mango contained lower bioactive compounds. Multivariate principal component analysis analysis showed higher concentration of bioactive compounds in cv. Sabre mango, whereas cv. Tommy Atkins was firm and heavier. Cv. Rosa and Phiva were moderately rich in bioactive compounds and lower in fruit weight and firmness, whereas cv. Peach was higher in TSS/ TA. The PPO activity was higher in cvs. Rosa and Zill.Instituto de Tecnología de AlimentosFil: Sellamuthu, Periyar Selvam. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; SudáfricaFil: Denoya, Gabriela Inés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimento. Laboratorio de Compuestos Proteicos; ArgentinaFil: Sivakumar, Dharini. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; SudáfricaFil: Polenta, Gustavo Alberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimento. Laboratorio de Compuestos Proteicos; ArgentinaFil: Soundy, Puffy. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; Sudáfric

Expression of pathogenesis-related (PR) genes in avocados fumigated with thyme oil vapours and control of anthracnose

Thyme oil (TO) fumigation (96 ll l 1) to cv. Hass and Ryan avocados significantly reduced anthracnose incidence compared to prochloraz and the untreated control. Also, enhanced activities of b-1,3- glucanase, chitinase were noted in both cultivars. TO fumigation induced the expression of both b-1,3- glucanase and chitinase genes in naturally infected fruit of both cultivars, during storage at 7 or 7.5 C for up to 21 d and during subsequent simulated market shelf conditions at 20 C for 5 d. However, the impact of TO fumigation on the b-1,3-glucanase gene expression was higher in both cultivars. Higher gene regulation and b-1,3-glucanase, chitinase activities were observed in cv. Ryan compared to Hass. Although TO fumigation significantly reduced anthracnose incidence in both naturally infected cultivars, the inhibitory effect was slightly higher in cv. Ryan than Hass. Thus, postharvest TO fumigation had positive effects on enhancing anthracnose disease resistance during storage and also gave a residual effect during the simulated shelf life.National Research Foundation (NRF) under the Technology and Human Resources for Industry Programme (THRIP) Grant.http://www.elsevier.com/locate/foodchem2017-03-31hb201

The efficacy of combined application of edible coatings and thyme oil in inducing resistance components in avocado (Persea americana Mill.) against anthracnose during post-harvest storage

Avocado fruit has high economic value; however, major post-harvest losses are encountered throughout the supply chain mostly due to anthracnose disease caused by the fungus Colletotrichum gloeosporioides. Increasing consumer concern regarding food safety and demand for organically produced fruits makes it necessary to search for natural environmentally friendly alternative products and processes for the fruit industry; particularly in disease control. Antifungal effects of Gum Arabic (GA) (10%), Aloe vera (AL) (2%), chitosan (CH) (1%) alone or in combination with thyme oil (1%) were investigated in vitro. CH + thyme oil and AL + thyme oil [1:1 or 3:1 v/v] showed fungicidal effects while AL, CH, GA and GA + thyme oil [3:1 v/v] showed fungistatic effects on mycelial growth of C. gloeosporioides in vitro. CH and AL coatings alone or in combination with thyme oil [3:1 v/v], either as preventative or curative treatments in comparison with commercial treatment (prochloraz, 0.05%) and untreated control were evaluated on incidence and severity (lesion diameter) of anthracnose in vivo. Preventative CH + thyme oil treatments significantly reduced the severity of anthracnose (8.9 mm) compared to thyme oil (12.7 mm), AL + TO (14.4 mm), CH (17.8 mm), AL (20.6 mm), PZ (18.3 mm) and untreated samples (34.8 mm). As curative method, the CH + thyme oil combination also reduced the severity of anthracnose by at least 4 mm compared to the other treatments. The total phenols, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase, catalase and superoxide dismutase activities, firmness and flesh colour were also determined. Results showed an increase in peroxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, chitinase, catalase and superoxide dismutase activities and total phenolics with reduced loss of firmness and flesh colour following CH + thyme oil treatments. This investigation recommends CH + thyme oil [3:1 v/v] combination treatment as a suitable alternative to the currently adopted prochloraz applications in controlling anthracnose disease in avocado fruit during storage.Post-Harvest Innovation Programme (Fresh Produce Exporter Forum, South Africa and Department of Science and Technology) awarded to the Tshwane University of Technology.http://www.elsevier.com/locate/cropro2015-10-31hb201

Phytochemicals and nutritional composition in accessions of Kei-apple (Dovyalis caffra): Southern African indigenous fruit

Current study was initiated to identify the phytochemicals and the nutritional profile of eleven Kei-apple fruit accessions. Accession FH29 showed the highest level (492.45 mg 100 gfresh weight) of total phenolic content, higher than the referral fruit, blueberry. Pyrogallol was identified as the predominant phenolic compound in all accessions. Accession FH 29 showed the highest (49.75 µmol TEAC gfresh weight) antioxidant capacity. Catechin content was higher in accessions; FH151, FH15, FH14, FH29, FH243, FH 239 and FH 231. Accessions, FH14 and FH232 exhibited higher levels of β-carotene than the referral fruit apples (cv. Top red) and peaches (cv. Excellence). The total sugar (glucose and fructose) was highest (50 mg gfresh weight) in accession FH240. Asparagine (3122.18 mg L) and gamma-aminobutyric (1688.87 mg L) were higher in accessions FH239 and FH243 respectively. Overall, the accession Kei-apple FH236 can be regarded as a good source of essential amino acids

Essential oil vapours suppress the development of anthracnose and enhance defence related and antioxidant enzyme activities in avocado fruit

Anthracnose caused by Colletotrichum gloeosporioides is a major postharvest disease in avocados that causes significant losses during transportation and storage. Complete inhibition of the radial mycelia growth of C. gloeosporioides in vitro was observed with citronella or peppermint oils at 8 μL plate−1 and thyme oil at 5 μL plate−1. Thyme oil at 66.7 μL L−1 significantly reduced anthracnose from 100% (untreated control) to 8.3% after 4 days, and to 13.9% after 6 days in artificially wounded and inoculated ‘Fuerte’ and ‘Hass’ fruit with C. gloeosporioides. GC/MS analysis revealed thymol (53.19% RA), menthol (41.62% RA) and citronellal (23.54% RA) as the dominant compounds in thyme, peppermint and citronella oils respectively. The activities of defence enzymes including chitinase, 1, 3-β-glucanase, phenylalanine ammonia-lyase and peroxidase were enhanced by thyme oil (66.7 μL L−1) treatment and the level of total phenolics in thyme oil treated fruit was higher than that in untreated (control) fruit. In addition, the thyme oil (66.7 μL L−1) treatment enhanced the antioxidant enzymes such as superoxide dismutase and catalase. These observations suggest that the effects of thyme oil on anthracnose in the avocado fruit are due to the elicitation of biochemical defence responses in the fruit and inducing the activities of antioxidant enzymes. Thus postharvest thyme oil treatment has positive effects on reducing anthracnose in avocados.Post-Harvest Innovation Programme (Fresh Produce Exporter Forum, South Africa and Department of Science and Technology).http://www.elsevier.com/locate/postharvbiohb201

Avocado fruit quality management during the postharvest supply chain

Avocados are a popular subtropical fruit of high economic importance, and the European Union is the biggest importer of the bulk of the fruit coming from countries such as South Africa, Chile, and Israel. The fruit is highly nutritious, being rich in vitamins A, B, C, minerals, potassium, phosphorus, magnesium, iron, and antioxidants. The biggest challenge is that the fruit is highly susceptible to qualitative and quantitative postharvest losses. Successful maintenance of avocado fruit quality during the supply chain depends on many aspects, including adequate orchard management practices, harvesting practices, packing operations, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are mostly attributed to flesh softening, decay, physiological disorders, and improper temperature management. Management of the supply chain is solely done to provide the fruit with the most favorable conditions to extend storage life, and retain quality and nutritional attributes of the fruit. The focus of this review is therefore to study the findings that have emanated from research done to retain overall avocado fruit quality and to reduce postharvest losses during the supply chain through the adoption of appropriate and novel postharvest technologies.Post-Harvest Innovation Programme (Fresh Produce Exporter Forum, South Africa, and Department of Science and Technology).http://www.tandfonline.com/loi/lfri202015-06-30hb201

Effect of modified atmosphere packaging on the quality and bioactive compounds of Chinese cabbage (Brasicca rapa L. ssp. chinensis)

BACKGROUND : The perishability of Brassica chinensis poses a major challenge to distribution and marketing. The aim of this work was to select a suitable modified atmosphere packaging to retain the overall quality and bioactive compounds during storage. RESULTS : Four types of biorientated polypropylene packaging (BOPP) – BOPP03, BOPP04, BOPP05 and BOPP06 – with different perforations were evaluated regarding the maintenance of quality parameters (weight loss, leaf yellowing, colour L*, C*, h°), decay, chlorophyll a, chlorophyll b, bioactive compounds (carotenoids, ascorbic acid, total phenolic compounds), antioxidant scavenging activity, overall appearance and odour evaluation, at 10°C at 2, 4, 6, 8 and 10 days. Leaves were packed in BOPP (two 2-mm holes) and packed and unpacked leaves were included for comparison. The modified atmosphere created (2% O2 and 7% CO2) inside the BOPP05 reduced leaf yellowing (higher h°), improved the overall appearance with acceptable odour, moderately maintained chlorophyll a and b, bioactive compounds and antioxidant scavenging activity, and remained marketable for up to 10 days at 10°C. Gas composition within the packages influenced the retention of bioactive compounds and overall quality. CONCLUSION : Application of BOPP05 is a promising method for extending the shelf life of B. chinensis leaves in order to promote its utilisation and commercialisation via urban fresh-produce markets.The National Research Foundation (NRF), South Africa as well as the postgraduate bursary award from the Tshwane University of Technology Research & Innovation Directorate, Pretoria, South Africa, to Ms Bevly Mmakatane Mampholo.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0010hb2016Biochemistr