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Polyamines (PAs) are natural compounds involved in many growth and developmental processes in plants, and, specifically in fruits, play a vital role regulating its development, ripening and senescence processes. Putrescine (PUT), spermine (SPE), and spermidine (SPD) are prominent PAs applied exogenously to extend shelf life of fruits. They also originate endogenously during developmental phases of horticultural crops and simultaneously affect the quality attributes and shelf life. Their anti-ethylene nature is being exploited to enhance the shelf life when exogenously applied on fruits. In growth and development of fruits, PA levels generally fall, which marks the beginning of senescence at postharvest phase. PUT, SPE and SPD treatments are being applied during postharvest phase to prolong the shelf life. They enhance the shelf life of fruits by reducing respiration rate, ethylene release and enhance firmness and quality attributes in fruits. PAs have a mitigating impact on biotic and abiotic stresses including chilling injury (CI) in tropical and sub-tropical fruits. PAs are environment friendly in nature and are biodegradable without showing any negative effect on environment. Biotechnological interventions by using chimeric gene constructs of PA encoding genes has boosted the research to develop transgenic fruits and vegetables which would possess inherent or in situ mechanism of enhanced biosynthesis of PAs at different stages of development and thereby will enhance the shelf life and quality in fruits. Internal and external quality attributes of fruits are improved by modulation of antioxidant system and by strengthening biophysical morphology of fruits by electrostatic interaction between PAs and phospholipids in the cell wall. [ABSTRACT FROM AUTHOR]

Pomegranate is a subtropical and tropical fruit of great importance from a health point of view. Despite increasing consumer awareness of the health benefits of pomegranate, consumption of the fruit is still limited owing to poor postharvest handling, storage recommendations, short shelf life and quality deterioration during transportation, storage and marketing. The occurrence of physiological disorders such as husk scald, splitting and chilling injury is another challenge reducing marketability and consumer acceptance. Recently, notable work on postharvest biology and technology has been done. Pomegranate is highly sensitive to low-oxygen (<5 kPa) atmospheres, chilling injury and decay. One of the major problems associated with pomegranate fruit is excessive weight loss, which may result in hardening of the husk and browning of the rind and arils. To reduce chilling injury incidence and to extend storability and marketing of pomegranates, good results were obtained with polyamine, heat, salicylic acid, methyl jasmonate or methyl salicylate treatments prior to cold storage. This article reviews the maturity indices, changes during maturation and ripening, postharvest physiology and technology of pomegranate fruit as well as the various postharvest treatments for maintaining fruit quality. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The efficacy of pre-storage application of 100 µM melatonin on conferring chilling tolerance in fruit of four mango cultivars stored at 5 ± 1 ºC for 28 d was investigated. 'Langra' and 'Gulab Jamun' mangoes had maximum and minimum chilling tolerance, respectively. Accumulation of endogenous polyamines and γ-aminobutyric acid (GABA) in the peel and the pulp of 'Langra' fruit treated with melatonin was a possible reason for its chilling tolerance. Accumulation of endogenous polyamines was associated with higher arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), and lower diamine oxidase (DAO) and polyamine oxidase (PAO) activities in the peel and pulp. Additionally, higher GABA shunt (Glutamate decarboxylase and GABA-transaminase) activity was associated with elevated GABA content in 'Langra' mangoes. The limited effectiveness of melatonin treatment for chilling injury alleviation in 'Chaunsa' was probably due to higher polyamines accumulation accompanied with lower PAO and DAO activity in the peel and pulp of the fruit, in addition to higher ADC and ODC in the peel. • Melatonin treatment (MTT) confers chilling tolerance (CT) in mango fruit. • MTT enhances polyamines accumulation and γ-aminobutyric acid shunt pathway activity. • MTT is effective in inhancing CT in 'Langra' mango. • MTT is moderately effective in inhancing CT in 'Chaunsa' and 'Dashehari' mangoes. • MTT is ineffective in inhancing CT in 'Gulab Jamun' mango. [ABSTRACT FROM AUTHOR]

Background The effect of storage temperature on physiological responses in Indian jujube ( Ziziphus mauritiana Lamk. cv. Gola) fruit was investigated. Freshly harvested fruits at physiological maturity characterised by colour-turning stage were stored at ambient temperature, 12 and 6 °C for 21, 35 and 35 days respectively. Headspace O2, CO2 and C2H4, moisture content, respiration, ethylene production, firmness, tristimulus colour, chroma, hue angle and chilling injury index were monitored during fruit storage. RESULTS Rates of respiration and ethylene production increased after 1 week of storage at ambient temperature, while peaks were observed after 2 weeks at 12 and 6 °C. Headspace O2 decreased continuously during storage, while CO2 and C2H4 increased at all storage temperatures. Moisture content and firmness also decreased during storage. Hunter L* values increased during storage, which correlated with the darkening of fruit colour. Fruit stored at ambient temperature did not show any chilling injury symptoms, while chilling injury appeared on day 28 under 12 °C storage and on day 21 under 6 °C storage. CONCLUSION Indian jujube fruit showed high rates of respiration and ethylene production that were significantly affected by different storage temperatures. Lower temperatures increased the shelf life of the fruit, but chilling injury was a problem under 6 °C storage. Indian jujube fruit could be stored at 6 °C for up to 35 days if chilling injury could be alleviated. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Melatonin confers cultivar-dependent chilling tolerance in mango fruit. • Melatonin maintained postharvest quality parameters like firmness, pH, TSS, and TA. • Changes to proline-metabolising enzymes promoted its increased concentration. • Effects of melatonin treatment were based on regulating proline metabolism. Exogenous melatonin (100 μM) was applied to four mango fruit cultivars, namely, 'Langra', 'Dashehari', 'Chaunsa', and 'Gulab Jamun', and subsequently stored at 5 ± 1 °C for 28 d. 'Langra' mangos responded best to melatonin treatment by increasing their chilling tolerance during storage, while 'Gulab Jamun' mangos did not experience any significant effect. MT reduced chilling injury index by 4.8, 1.8, 1.7 and 1.1 times in 'Langra', 'Chaunsa', 'Dashehari' and 'Gulab Jamun', respectively, as compared to non-treated mangos, after 28 d of storage at 5 ± 1 °C. This efficacy of MT on quality preservation at chilling temperatures was associated with delayed ethylene production and respiration rate, a lower concentration of malondialdehyde, as well as maintenance of physicochemical properties like firmness, pH, total soluble solids, and titratable acidity in most cultivars, except for 'Gulab Jamun'. Additionally, MT treated 'Langra' mangos showed 1.39 times higher proline content, as compared to non-treated mangos. This was likely due to higher activities of Δ1-pyrroline-5-carboxylate synthetase and ornithine-δ-aminotransferase, in addition to lower proline dehydrogenase activity at 28 d of storage. This effect was not apparent on 'Gulab Jamun' mangos, whereas 'Chaunsa' and 'Dashehari' mangos showed a moderate response to the MT treatment on their physiochemical properties and proline metabolism. Thus, our data suggests that MT treatment exerted a cultivar-dependent control on signs of chilling injury. [ABSTRACT FROM AUTHOR]