Effect of gamma irradiation on some physicochemical properties and bioactive compounds of jujube (Ziziphus jujuba var vulgaris) fruit

• The effects of gamma irradiation on bioactive compounds of jujube fruit were studied.
• Total phenolic and anthocyanin contents increased by irradiation.
• A considerable decrease of organic acids contents was observed at high doses.
• Irradiation affected significantly the water-soluble vitamins contents.
• Irradiation protected the main bioactive compounds of jujube fruit up to 2.5 kGy.

Interest in the protection of bioactive compounds and a safe alternative method for preservation of processed fruits and fruit juices has recently increased significantly throughout the world. There is a distinct lack of information on the profile of bioactive compounds in jujube fruit (e.g. organic acids, anthocyanins, and water-soluble vitamins) and their changes during processing (e.g. gamma irradiation). Therefore, in this study, the effect of gamma irradiation at different doses (0.0, 0.5, 1.0, 2.5 and 5.0 kGy) on some physicochemical properties and the bioactive compounds of jujube fruit was investigated. The total soluble solids (TSSs) values remained unaffected at various doses, while the level of total acidity (TA) showed a slight increase at doses ≥≥2.5 kGy (p  ≤≤0.05). Irradiation up to 2.5 kGy caused a significant increase in the total monomeric anthocyanin and the total phenolic content (about 12% and 6%, respectively), but a significant decrease was observed in both parameters immediately after irradiation at 5 kGy. Moreover, irradiation treatment caused a significant decrease in L* value and a significant increase in a* and b* values (P  ≤≤0.05); however, changes of color were slight until the dose of 5 kGy. Gamma irradiation up to 2.5 kGy had no significant effect on the concentration of malic, citric and succinic acids, while the level of ascorbic acid decreased significantly at all irradiation doses (0–5 kGy). Cyanidin-3, 5-diglucoside was determined as the major anthocyanin in the jujube fruit studied (about 68%), which was reduced significantly when 5 kGy of irradiation was applied (degradation percentage: 27%). The results demonstrated that vitamins C, B2 and B1 are the most water-soluble vitamins in jujube fruit, respectively. Vitamins C and B1 content significantly decreased at all applied doses (0–5 kGy), whereas B2 content at doses ≤≤2.5 kGy was not significantly affected. The results of this study indicate that gamma irradiation at doses below 2.5 kGy can be successfully used for improving the quality the jujube fruit.