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Background: To effectively extend the shelf life of fresh jujube, carbon monoxide (CO), as a small molecular gas, was applied to fumigate fresh jujube. The quality and antioxidant activity of jujubes fumigated with carbon monoxide at concentrations of 0 (control), 5, 10, 20 and 40 µmol L⁻¹ for 1 h under ambient temperature were investigated., Results: The jujube fumigated with 10 µmol L⁻¹ CO showed the best preserving effect amongst all samples. At 30 days, the decay incidence of jujube fumigated with 10 µmol L⁻¹ CO is only two-thirds of that of control sample; its red index and weight loss rate were 22.8% and 19.4% lower, and its firmness, soluble solids content (SSC) and acidity were 18.7%, 5.4% and 12.2% higher than that of control samples, respectively. Its vitamin C and total flavonoid contents were also the highest. However, no significant difference in total polyphenol content was found. The jujubes treated with 10 µmol L⁻¹ CO exhibited the highest antioxidant activity in terms of reducing power and 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical scavenging activity. However, the jujubes fumigated with 40 µmol L⁻¹ CO showed inferior characteristics compared with the control sample., Conclusion: Fumigating jujubes with proper concentration of CO probably is a potential novel method for post-harvest jujube preservation in the future., (© 2013 Society of Chemical Industry.)

Abstract: The effect of carbon monoxide (CO) on enzymatic browning of fresh-cut lotus root slices in relation to phenolic metabolism was investigated. Fresh-cut lotus root slices were fumigated with CO gas at 75, 125, 175 or 225 μL/L for 10, 20, 30 or 40 min, and then stored for 8 days at 5 °C. Changes in color, total phenol, malonaldehyde (MDA), and activities of phenolic-associated enzymes including polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonialyase (PAL) in lotus root slices were measured. The results indicated that fumigating fresh-cut lotus root slices with 175 μL/L of CO for 20 min delayed browning and inhibited increase of MDA. Besides, total phenol also showed higher level from 0 to 4 days. Furthermore, the activities of PPO and POD were inhibited, but PAL activity was increased. The present data suggests that CO has the potential to inhibit browning and maintain quality of fresh-cut lotus root slices. [Copyright &y& Elsevier]

• Postharvest CO treatment effectively controlled Alternaria rot in jujube. • CO did not show any antifungal activity to A. alternata in vitro. • CO treatment enhanced the accumulation of antifungal substances. • CO activated disease resistance-related enzymes (PAL, PPO, CHI and GLU) in jujube. CO is a gas signal molecule involved in various physiological and metabolic regulation processes in plants. In the present study, we evaluated the effects of CO fumigation on the control of Alternaria rot in jujube fruit and explored the mechanism of action. Results showed that CO at 10 μmol L−1 significantly reduced lesion diameter in the fruit inoculated with A. alternata without showing any antifungal activity in vitro. CO treatment enhanced the activities of four representative resistance-related enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, chitinase, and β-1,3-glucanase). Furthermore, CO also led to increase in the content of phenolics, flavonoids, lignin, and H 2 O 2. These results indicate that CO induces resistance to Alternaria rot primarily by activating disease resistance-related enzymes and enhancing accumulation of antifungal substances, and that CO can be a promising elicitor of plant defense responses to resist Alternaria rot in postharvest jujube fruit. [ABSTRACT FROM AUTHOR]