D. C. Joyce

Postharvest - An introduction to the physiology and handling of fruit, vegetables and ornamentals

Effective postharvest handling is critical in maintaining the quality and freshness of crops from the time when they are harvested to when they are sold to the consumer. Presented in a new larger format with an expanded colour section, this broad-based introductory level textbook covers the key concepts and practical technologies to slow the inevitable deterioration of harvested produce, including handling, packaging, transport, temperature management and the control of pests and diseases. The 5th edition is updated with current industry developments and practices.

ABA effects on ethylene production, PAL activity, anthocyanin and phenolic contents of strawberry fruit

Effects of exogenously applied abscisic acid (ABA) on ethyleneproduction rate, phenylalanine ammonia-lyase (PAL) enzyme activity, andanthocyanin and phenolic concentrations in harvested strawberry cv. Everestfruit were evaluated. Colouration and firmness were also assessed on fruit held for 3days at 20 °C. ABA treatment accelerated fruit colour andsoftening. Treatment with 10−5 or 10−4 mol ABAl−1 stimulated ethylene production. Anthocyanin and phenoliccontents and PAL activity increased during storage, but more rapidly in ABAtreated fruit. As a result, red colour development was accelerated. EndogenousABA may play a role in strawberry fruit colour development during ripeningthrough up-regulation of ethylene production and PAL activity.

1-Methylcyclopropene treatment affects strawberry fruit decay

Strawberry cv. Everest fruit were treated with 1-methylcyclopropene (I-MCP) at various concentrations from 0 to 1000 nl/l for 2 h at 20 degreesC. They were then kept individually in closed but vented containers for 3 days in the dark at 20 degreesC and 95 - 100% relative humidity. 1-MCP treatment tended to maintain strawberry fruit firmness and colour. However. disease development was accelerated in fruit treated at high (500 and 1000 nl/l) I-MCP concentrations. I-MCP treatment also lowered ethylene production. Treatment with I-MCP inhibited phenylalanine ammmonia-lyase (PAL) activity, and lowered increases in anthocyanin and phenolic contents. Comparatively low levels of phenolics in fruit treated at the highest I-MCP concentration (1000 nl/l) could account for decreased disease resistance of these fruit

Postharvest biology and handling of longan fruit (Dimocarpus longan Lour.)

The mature longan fruit (Diniocarpus longan Lour.) is small (ca. 1.5-2 cm diameter), conical, heart-shaped or spherical in shape and light brown in colour. It has a thin, leathery and indehiscent pericarp surrounding a succulent, edible white aril. The aril contains a relatively large dark brown seed. Maturity can be determined on the basis of fruit weight, skin colour, flesh sugar concentration, flesh acid concentration, sugar:acid ratio, flavour and/or days from anthesis. Longan fruit are non-climacteric with little change in soluble solids concentration (SSC) or titratable acidity (TA) after harvest. Longan fruit deteriorate rapidly unless proper handling techniques are employed. The major factors reducing the storage life and marketability of longan fruit are microbial decay and pericarp browning. Low temperature storage at 1-5 degreesC is used to reduce pathological decay, but has a only limited role in reducing pericarp browning. Moreover, the, fruit deteriorate rapidly when removed from cold storage. Under refrigeration, longan fruit have a storage life of approximately 30 days. Pulp quality and disease development are generally stable during cold storage until such time as fruit become visually unacceptable from pericarp browning. Sulfur dioxide fumigation has been the most effective postharvest treatment for control of pericarp browning in longan fruit, and is used extensively in commercial situations at present. However, there is increasing consumer and regulatory resistance to the use of this chemical. Insect disinfestation has become increasingly important with the expanding export market. Irradiation and heat treatments for insect disinfestation of longan fruit have been found to be alternatives to treatment with insecticides. Recent research has focused on reducing these major postharvest problems in order to produce light-coloured, chemical-free fruit without disease or insect infestation

Extension of the shelf life of banana fruit by 1-methylcyclopropene in combination with polyethylene bags

The effect of the new anti-ethylene compound 1-methylcyclopropene (1-MCP) in combination with polyethylene bags on the ripening of harvested banana fruit was investigated. 1-MCP treatment delayed peel colour change and fruit softening, and extended shelf life in association with suppression of respiration and C2H4 evolution. Banana fruit ripening was delayed when exposed to 0.01-1.0 mu l 1-MCP/l for 24 h, and increasing concentrations of 1-MCP were generally more effective for longer periods of time. Similar results were obtained with fruit sealed in polyethylene bags (0.03 mm thick) containing 1-MCP at various concentrations, but longer delays in ripening were achieved. The greatest longevity of about 58 days was realised by packing fruit in sealed polyethylene bags with 1-MCP at either of 0.5 or 1.0 mu l/l. Analyses of C2H4 and CO2 concentrations within polyethylene bags confirmed that 1-MCP suppressed both C2H4 evolution and respiration. Thus, application of 1-MCP in combination with the use of polyethylene bags can greatly extend the postharvest life of banana fruit

Application of magnetic resonance imaging to pre- and post-harvest studies of fruits and vegetables

As magnetic resonance imaging (MRI) systems with cryomagnets large enough to accommodate samples of interest to postharvest researchers become more accessible, MRI will come to be regarded as an integral component in pre- and post-harvest investigations of physiological changes in fruit and vegetables. The non-invasive, non-destructive attributes of H-1 MRI, and its ability to provide highly resolved spatial information concerning the distribution and magnetic environment of water in soft tissues, makes it an attractive technique for probing such samples. In reports to date, examination of the quality, histology, histochemistry and structural characteristics of samples have been emphasised. These and other applications pertaining to the study of fruits and vegetables are reviewed, as well as recent developments that employ nuclear magnetic resonance principles as on-line sensors in postharvest sorting and processing situations

Role of phenylalanine ammonia-lyase in heat pretreatment-induced chilling tolerance in banana fruit

Increasing evidence suggests that phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) is associated with low temperature stress in plant tissues. Banana fruit are highly susceptible to chilling injury. However, little is known about the role of PAL (i.e. gene expression, protein level and activity) in fruit chilling. In this work, the involvement of PAL induced by heat treatment (38 degrees C for 3 days) prior to storage (8 degrees C) in chilling tolerance was investigated. The PAL inhibitor 2-aminoindan-2-phosphonic acid (AIP) was also used to further study the role of PAL in the chilling tolerance. The results showed that mRNA transcripts (MaPAL1 and MaPAL2) and PAL protein levels increased during storage at chilling temperature. Heat treatment prior to storage alleviated chilling injury and enhanced PAL activity, protein amount and MaPAL1 and MaPAL2 transcript levels. The increases in parameters of PAL upon heat pretreatment were all inhibited by AIP treatment, which resulted in aggravation of chilling injury. Thus, these findings indicate that the induction of PAL by heat pretreatment was regulated at both the transcriptional and the translational levels and that PAL may play a role in heat pretreatment-induced chilling tolerance of banana fruit.

Responses of banana fruit to treatment with 1-methylcyclopropene

Experiments were conducted to determine levels of 1-methylcyclopropene (1-MCP) exposure needed to prevent ethylene-stimulated banana fruit ripening, characterise responses of ethylene-treated fruit to subsequent treatment with 1-MCP, and to test effects of subsequent ethylene treatment on 1-MCP-treated fruit softening. Fruit softening was measured at 20°C and 90% relative humidity. One hour exposure at 20°C to 1000 nl 1-MCP/l essentially eliminated ethylene-stimulated ripening effects. Exposure for 12 h at 20°C to just 50 nl 1-MCP/l was similarly effective. Fruit ripening initiated by ethylene treatment could also be delayed with subsequent 1-MCP treatment. However, 1-MCP treatment only slowed down ripening of ethylene-treated fruit when applied at 1 day after ethylene and was ineffective when applied 3 or 5 days after ethylene treatment. The ripening response of fruit treated with 1-MCP and subsequently treated with ethylene varied with interval time between 1-MCP and ethylene treatments. As time increased, the response of 1-MCP-treated fruit to ethylene was enhanced. Responses to 0.1, 1, 10 or 100 µl ethylene/l concentrations were similar. Enzyme kinetic analysis applied to 1-MCP effects on ethylene-induced softening of banana fruit suggested that 1-MCP inhibition is by noncompetitive antagonism of ethylene binding.

Role of Trichomes in Sunflower Tolerance to Manganese Toxicity

SummaryIn comparison with other crop species, sunflower (Helianthus annuus L.) has been found to be very tolerant of high manganese (Mn) concentrations in nutrient solution. Furthermore, sunflower was able to accumulate high Mn concentrations in plant tops without apparent detrimental effect on growth. The first symptom of excess Mn supply (c. 30μM Mn in solution) was the appearance of small, dark-brown to black spots (<0.5 mm in diameter) on lower stems and on petioles and blades of the lower leaves. The spots were not necrotic and were visibly associated with the trichomes on these plant parts. Electron microprobe techniques demonstrated an accumulation of Mn in and around the trichomes. A compartmentation mechanism is suggested whereby sunflower is able to tolerate high Mn concentrations in its tissues through localization of Mn in a metabolically inactive form.At Mn concentrations approximately 6 times higher than that required to produce the small, dark spots, the upper recently-expanded leaves developed a veinal chlorosis and severe leaf crinkling of the interveinal areas. Dark brown lesions (>2 mm in size) developed on the lower leaves, especially along the veins. A concentration of 2205 μg Mn g−1 in the tops was associated with a 10% reduction in plant dry matter yield.

Postharvest characteristics and handling of litchi fruit - an overview

Litchi ( Litchi chinensis Sonn.) is a tropical to subtropical crop that originated in South-East Asia. Litchi fruit are prized on the world market for their flavour, semi-translucent white aril and attractive red skin. Litchi is now grown commercially in many countries and production in Australia, China, Israel, South Africa and Thailand has expanded markedly in recent years. Increased production has made significant contributions to economic development in these countries, especially those in South-East Asia. Non-climacteric litchi fruit are harvested at their visual and organoleptic optimum. They are highly perishable and, consequently, have a short life that limits marketability and potential expansion of demand. Pericarp browning and pathological decay are common and important defects of harvested litchi fruit. Postharvest technologies have been developed to reduce these defects. These technologies involve cooling and heating the fruit, use of various packages and packaging materials and the application of fungicides and other chemicals. Through the use of fungicides and refrigeration, litchi fruit have a storage life of about 30 days. However, when they are removed from storage, their shelf life at ambient temperature is very short due to pericarp browning and fruit rotting. Low temperature acclimation or use of chitsoan as a coating can extend the shelf life. Sulfur dioxide fumigation effectively reduces pericarp browning, but approval from Europe, Australia and Japan for this chemical is likely to be withdrawn due to concerns over sulfur residues in fumigated fruit. Thus, sulfur-free postharvest treatments that maintain fruit skin colour are increasingly important. Alternatives to SO2 fumigation for control of pericarp browning and fruit rotting are pre-storage pathogen management, anoxia treatment, and dipping in 2% hydrogen chloride solution for 6-8 min following storage at 0 degrees C. Insect disinfestation has become increasingly important for the expansion of export markets because of quarantine issues associated with some fruit fly species. Thus, effective disinfestation protocols need to be developed. Heat treatment has shown promise as a quarantine technology, but it injures pericarp tissue and results in skin browning. However, heat treatment can be combined with an acid dip treatment that inhibits browning. Therefore, the primary aim of postharvest litchi research remains the achievement of highly coloured fruit which is free of pests and disease. Future research should focus on disease control before harvest, combined acid and heat treatments after harvest and careful temperature management during storage and transport.