Shifeng Cao

Effect of high oxygen atmosphere storage on quality, antioxidant enzymes, and DPPH-radical scavenging activity 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.

Effect of exogenous γ-aminobutyric acid treatment on proline accumulation and chilling injury in peach fruit after long-term cold storage.

The effect of exogenous γ-aminobutyric acid (GABA) on chilling injury of peach fruit was investigated. Freshly harvested peaches were treated with 1, 5, or 10 mM GABA at 20 °C for 10 min and then stored at 1 °C for up to 5 weeks. The results showed that all of the GABA treatments could reduce chilling injury of peach fruit with 5 mM being the most effective concentration. GABA treatment significantly enhanced the accumulation of endogenous GABA and proline, which resulted from the increased activities of glutamate decarboxylase, Δ(1)-pyrroline-5-carboxylate synthetase, and ornithine δ-aminotransferase and decreased proline dehydrogenase activity. Our results revealed that GABA treatment may be a useful technique to alleviate chilling injury in cold-stored peach fruit, and the reduction in chilling by GABA may be due to the induction of endogenous GABA and proline accumulation. These data are the first evidence that exogenous GABA induced chilling tolerance in postharvest horticultural products.

Methyl jasmonate reduces decay and enhances antioxidant capacity in Chinese bayberries.

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.

Combined salicyclic acid and ultrasound treatments for reducing the chilling injury on peach fruit.

The effects of salicylic acid (SA; 1 mmol L(-1)) and ultrasound treatment (40 kHz, 10 min) either separately or combined on the chilling injury (CI) in cold-stored peach fruit ( Prunus persica Batsch cv. Baifeng) were investigated. The results showed that SA treatment alone alleviated CI during storage. Ultrasound alone had no influence, but when it was combined with SA, it resulted in greater inhibition of CI than SA alone. The activities of antioxidant enzymes, such as catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, were induced by a combination of SA with ultrasound. In addition, the combined treatment also increased the endogenous SA concentrations in peaches. These results suggested that the induced tolerance against CI by the combination of ultrasound and SA treatment in cold-stored peach fruit was related to the induction of antioxidant enzymes and the increase in the SA concentration.

Blue Light Irradiation Affects Anthocyanin Content and Enzyme Activities Involved in Postharvest Strawberry Fruit

Blue light irradiation was applied to postharvest strawberry fruit to explore its influence on anthocyanin content and anthocyanin biosynthetic enzyme activities. Strawberry fruit was irradiated with blue light at 40 μmol m(-2) s(-1) for 12 days at 5 °C. The results indicated that blue light treatment improved total anthocyanin content in strawberry fruit during storage. Meanwhile, the treatment increased the activities of glucose-6-phosphate, shikimate dehydrogenase, tyrosine ammonia-lyase, phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate/coenzyme A ligase, dihydroflavonol-4-reductase, chalcone synthase, flavanone-3-β-hydroxylase, anthocyanin synthase, and UDP-glycose flavonoid-3-O-glycosyltranferase, which suggested that the enhancement of anthocyanin concentration by blue light might result from the activation of its related enzymes. Blue light might be proposed as a supplemental light source in the storage of strawberry fruit to improve its anthocyanin content.

Domestic cooking methods affect the nutritional quality of red cabbage

The aim of this work is to investigate the effects of domestic cooking methods, including steaming, microwave heating, boiling and stir-frying on the nutritional quality of red cabbage. Compared with fresh-cut red cabbage, all cooking methods were found to cause significant reduction in anthocyanin and total glucosinolates contents. Moreover, steaming resulted in significantly greater retention of vitamin C and DPPH radical-scavenging activity, while stir-frying and boiling, two popular Chinese cooking methods, led to significant losses of total phenolic, vitamin C, DPPH radical-scavenging activity, and total soluble sugar as well as reducing sugars. Normally, red cabbage consumed fresh in salads could maintain the highest nutrition. However, considering the habits of Asian cuisine, it is recommended to use less water and less cooking time, such as steaming based on our present results, so as to retain the optimum benefits of the health-promoting compounds.

Effect of hot air treatment on postharvest mould decay in Chinese bayberry fruit and the possible mechanisms

The effect of hot air treatment (HAT) on reducing natural fungal decay and green mould decay caused by Leptographium abietinum on postharvest Chinese bayberry fruit and the possible mechanisms were investigated. Freshly harvested Chinese bayberry fruit were firstly pretreated with hot air at 36-60 degrees C for 1-3h, and then stored at 20 degrees C for 3d or at 1 degrees C for 12d to investigate the optimum condition of hot air treatment (HAT) for inhibiting decay development. Results demonstrated that HAT at 48 degrees C for 3h was the most effective in reducing natural decay without impairing quality. This treatment also enhanced the resistance of Chinese bayberry fruit against green mould rot caused by L. abietinum and reduced the severity of the disease. The activities of defense-related enzymes including chitinase, beta-1, 3-glucanase, peroxidase and polyphenol oxidase were significantly enhanced by HAT. In addition, the in vitro experiment showed that HAT significantly inhibited spore germination, germ tube elongation and mycelial growth of L. abietinum. These results indicate that HAT can effectively reduce fruit decay possibly by directly inhibiting pathogen growth and indirectly inducing disease resistance.

Effect of MeJA treatment on polyamine, energy status and anthracnose rot of loquat fruit

The effect of methyl jasmonate (MeJA) on changes in polyamines content and energy status and their relation to disease resistance was investigated. Freshly harvested loquat fruit were treated with 10 μmol l(-1) MeJA and wound inoculated with Colletotrichum acutatum spore suspension (1.0 × 10(5) spores ml(-1)) after 24h, and then stored at 20 °C for 6 days. MeJA treatment significantly reduced decay incidence. MeJA treated fruit manifested higher contents of polyamines (putrescine, spermidine and spermine) compared with the control fruit, during storage. MeJA treatment also maintained higher levels of adenosine triphosphate, and suppressed an increase in adenosine monophosphate content in loquat fruit. These results suggest that MeJA treatment may inhibit anthracnose rot by increasing polyamine content and maintaining the energy status.

Respiratory activity and mitochondrial membrane associated with fruit senescence in postharvest peaches in response to UV-C treatment

The effect of 3.0kJ/m(2) ultraviolet-C (UV-C) treatment on respiratory activity and mitochondrial membrane associated with fruit senescence in peach fruit stored at 20°C for 8days was investigated. UV-C treatment could reduce senescence development, as evidenced by higher fruit firmness due to inhibition of respiration rate via reducing succinic dehydrogenase and cytochrome C oxidase activity. Meanwhile, the activities of superoxide dismutase, catalase and ascorbate peroxidase in the UV-C-treated fruit were much higher than those in control fruit, resulting in lower levels of superoxide radicals (O2(-)) and hydrogen peroxide (H2O2). In addition, this treatment maintained a higher level of mitochondrial membrane fluidity and inhibited opening of mitochondrial permeability transition pore. Our results suggest that the induction of antioxidant enzymes to scavenge O2(-) and H2O2 by UV-C treatment was associated with the maintenance of mitochondrial membrane integrity, which also played an important role in senescence retardation in peach fruit.

Improved control of anthracnose rot in loquat fruit by a combination treatment of Pichia membranifaciens with CaCl2

The beneficial effect of 2% CaCl(2) (w/v) on the antagonistic yeast Pichia membranifaciens for control of anthracnose rot caused by Colletotrichum acutatum in postharvest loquat fruit (Eriobotrya japonica L.) and the possible mechanisms involved were investigated. The results showed that treatment with P. membranifaciens at 1x10(8) CFU ml(-1) or 2% CaCl(2) alone both resulted in significantly smaller lesion diameter and lower disease incidence of anthracnose rot on loquat fruit wounds compared with the controls. The biocontrol activity of P. membranifaciens on the disease was enhanced by the addition of 2% CaCl(2), the combined treatment of P. membranifaciens with CaCl(2) resulted in a remarkably improved control of the disease in comparison with the treatment of P. membranifaciens or CaCl(2) alone. P. membranifaciens in combination with CaCl(2) induced higher activities of two defense-related enzymes chitinase and beta-1,3-glucanase in loquat fruit than applying the yeast or CaCl(2) alone. The in vitro experiment showed that the addition of 2% CaCl(2) in the suspensions of P. membranifaciens significantly inhibited spore germination and germ tube elongation of C. acutatum than the yeast or CaCl(2) alone. However, adding CaCl(2) did not significantly influence the population of P. membranifaciens in NYDB medium or fruit wounds. These results suggest that CaCl(2) could improve the biocontrol activity of P. membranifaciens on anthracnose rot in loquat fruit. It is postulated that the improved control of the disease is directly because of the higher inhibitory effect on pathogen growth and indirectly because of the enhanced disease resistance in loquat fruit by the combination treatment.