Search

Melatonin has been reported to alleviate chilling symptoms in postharvest peach fruit during cold storage, however, the mechanism involved is largely unknown. To better understand its role in chilling tolerance, here we investigated the effects of melatonin on oxidative damage in peach fruit subjected to chilling after harvest. Chilling injury of peaches was dramatically reduced by melatonin treatment. Melatonin induced hydrogen peroxide (H 2 O 2 ) content at the early stage of storage but inhibited its accumulation thereafter. Meanwhile, melatonin also up-regulated the expression of genes involved in antioxidant responses in peaches. In addition, compared to the control fruit, peaches treated with melatonin displayed higher transcript abundance of ascorbic acid (AsA) biosynthetic genes and consequently increased the AsA content. Our results suggested that in response to melatonin during chilling, the high H 2 O 2 level in the treated peaches at the initial time of storage, may work as a signaling molecule to induce protective mechanisms via up-regulating the expression of antioxidative genes and increasing AsA content. On the other hand, after the transient increase in the treated peaches, H 2 O 2 was efficiently removed because of the activated antioxidant systems, which was associated with the higher chilling tolerance induced by melatonin.

Two cultivars of loquat fruit were stored at 20°C for 10days to investigate the relationship between disease resistance, and fatty acid composition and activities of endogenous antioxidant enzymes. The results showed that decay incidence increased with storage time in both cultivars. A significantly lower disease incidence was observed in 'Qingzhong' fruit than in 'Fuyang', suggesting 'Qingzhong' had increased disease resistance. Meanwhile, 'Qingzhong' fruit also had lower levels of superoxide radical and hydrogen peroxide, and lower lipoxygenase activity, but higher levels of linolenic and linoleic acids and higher activities of catalase (CAT) and ascorbate peroxidase (APX) compared with 'Fuyang'. These results suggest that the higher levels of linolenic and linoleic acids and the higher activity of CAT and APX have a role in disease resistance of postharvest loquat fruit., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Broccoli deteriorates very quickly after harvest at ambient temperature due to the loss of green colour and the consequent yellowing of florets. To search for an effective method to control quality deterioration, the effect of 1-methylcyclopropene (1-MCP) combined with 6-benzylaminopurine (6-BA) treatment on visual quality, antioxidant enzymes and bioactive compounds in broccoli florets were investigated., Results: A combined treatment of 2.5 µL L⁻¹ 1-MCP and 200 mg L⁻¹ 6-BA significantly reduced the increase of lightness (L*) value, and retained a high level for the hue value (H) and chlorophyll content. Superoxide dismutase, ascobate peroxidase and catalase activities increased while the activity of peroxidase decreased during storage in treated samples in comparison with the controls. The combined treatment enhanced the biosynthesis of glucosinolate and the formation of the anticarcinogen sulforaphane, which improved the health benefit of broccoli., Conclusion: These results indicate that a combined treatment of 1-MCP and 6-BA could be a good candidate for maintaining the visual quality and enhancing the nutritional value in broccoli during storage at 15 °C., (© 2012 Society of Chemical Industry.)

The effects of methyl jasmonate (MeJA) on postharvest decay and antioxidant capacity in harvested Chinese bayberry fruit were investigated. Chinese bayberries were treated with 0, 1, 10, 100, or 1000 micromol L(-1) MeJA at 20 degrees C for 6 h and then stored at 0 degrees C for 12 days. MeJA at 10 micromol L(-1) was most effective in reducing fruit decay; quality parameters including pH value, total soluble solids, and titratable acidity were not significantly affected by MeJA treatment. Fruit treated with 10 micromol L(-1) MeJA exhibited significantly higher phenylalanine ammonia-lyase activity and higher levels of total phenolics, flavonoids, and anthocyanins as well as individual phenolic compounds than control. These fruits also maintained significantly higher antioxidant activity as measured by scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radicals and by the reducing power test compared to the control. These results indicate that MeJA can effectively reduce fruit decay and improve antioxidant capacity of Chinese bayberry fruit.

The influence of high O(2) atmosphere on postharvest decay, quality, total phenolic, total anthocyanin contents, antioxidant enzymes activity, and antioxidant activity of Chinese bayberry fruit was investigated. Freshly harvested Chinese bayberry fruits were placed in jars and ventilated continuously with air or with 80 and 100% O(2) for up to 12 days. Samples were randomly selected initially and at 3-days interval during storage. The fruit exposed to high O(2) was resistant to decay, had high levels of total soluble solids, titratable acidity and ascorbic acid contents, and also reduced the increment of pH value. High O(2) treatment was less stressful as reflected by having the significantly lower malonaldehyde contents and higher catalase, ascorbic acid peroxidase, and peroxidase activities during storage. Both 80% and 100% O(2) treaments had also retained the bioactive contents and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity during storage. These results indicate that elevated O(2) levels may improve the ability of the antioxidative defense mechanism in Chinese bayberry and result in a better control of fruit decay.

Abstract: The effect of 1-methylcyclopropene (1-MCP) on senescence and quality maintenance of green bell pepper fruit was investigated. To explore the optimum concentration of 1-MCP to delay senescence, pepper fruit were treated with 0.5, 1.0 or 1.5μLL−1 1-MCP and then stored for 10d at 20°C. The results showed that the application of 1-MCP at 1.0μLL−1 was most effective in delaying senescence, manifested as chlorophyll degradation and increase in weight loss. 1-MCP treated peppers had higher levels of chlorophyll, protein and vitamin C and lower respiration rates and ethylene production compared with that in control peppers. In addition, 1-MCP enhanced activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase and levels of polyamines including putrescine, spermidine and spermine. These results suggested that the delaying senescence of green bell pepper by 1-MCP treatment is associated with enhanced antioxidant enzyme activities and polyamine contents. [Copyright &y& Elsevier]

Abstract: Two cultivars of loquat fruit with contrasting chilling resistance were stored at 1°C for 35days to investigate the relationship between chilling injury and fatty acid composition and its antioxidant system. No symptoms of chilling injury occurred in the fruit of ‘Qingzhong’ cultivar during the whole storage, whereas in ‘Fuyang’ fruit, chilling injury increased sharply after 21days of storage at 1°C. ‘Qingzhong’ fruit had lower levels of superoxide radical and H2O2, in addition to lower lipoxygenase activity, but higher membrane lipid unsaturation and higher activities of superoxide dismutase and catalase than ‘Fuyang’. Furthermore, the chilling resistant ‘Qingzhong’ fruit also showed higher activities of antioxidant enzymes involved in ascorbate–glutathione cycle and higher levels of ascorbate acid and reduced glutathione. These results suggest that the higher membrane lipid unsaturation and the more efficient antioxidant system were both beneficial in enhancing resistance of loquat fruit to chilling injury. [Copyright &y& Elsevier]

Abstract: Peach fruit were immersed in 5mM γ-aminobutyric acid (GABA) solution for 10min at 20°C and then stored at 1°C for 5weeks to investigate the effect of GABA treatment on chilling injury (CI), antioxidant enzymes and energy status in peach fruit. The results showed that GABA treatment significantly inhibited CI incidence of peaches and enhanced activities of antioxidant enzymes, such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione S-transferase, monodehydroascorbate reductase and dehydroascorbate reductase. The treatment also increased contents of adenosine triphosphate and adenosine diphosphate, but lowered adenosine monophosphate content, which resulted in a higher level of energy charge in treated fruit. These results indicated that GABA increased chilling tolerance of peach fruit through enhancing its enzymatic antioxidant system and maintaining energy status in peach fruit. [Copyright &y& Elsevier]

Abstract: The effect of benzo-thiadiazole-7-carbothioic acid S-methyl ester (BTH), at 0.2g/l, on antioxidant enzymes, radical-scavenging activity and decay development in strawberry (Fragaria×ananassa Duch.) fruit, was investigated. The results showed that BTH treatment enhanced the activities of antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, and glutathione reductase. The treatment increased the contents of phenolic and anthocyanin in strawberry fruit, as well as radical-scavenging capacity, expressed as 1,1-diphenyl-2-picrylhydrazyl and superoxide radical values and reducing power. The treatment also decreased the development of decay compared to control fruit. These results indicated that BTH might increase the disease resistance of strawberry fruits by enhancing their antioxidant systems and their free radical-scavenging capabilities. [ABSTRACT FROM AUTHOR]