Effect of phytosanitary irradiation on the quality of two varieties of pummelos (Citrus maxima (Burm.) Merr.)

Authors: JAIN, A - Chapman University; PAZ, J - Centro De Investigacion En Alimentaction Y Desarollo; Obenland, David - Dave; RODRIGUEZ, K - Chapman University; PRAKASH, A - Chapman University

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2017
Publication Date: 1/23/2017
Citation: Jain, A., Paz, J., Obenland, D.M., Rodriguez, K., Prakash, A. 2017. Effect of phytosanitary irradiation on the quality of two varieties of pummelos (Citrus maxima (Burm.) Merr.). Scientia Horticulturae. 217:36-37. doi:10.1016/j.scienta.2017.01.029.

Interpretive Summary: Pummelo is an increasingly important citrus crop that may require a quarantine treatment to enable export from the United States, although little is known regarding its response to the potential treatments. Irradiation is increasingly being considered an alternative to chemical phytosanitary treatments, such as methyl bromide. In this study, the effect of 150 Gy or 1000 Gy gamma irradiation doses on pummelo quality was evaluated following storage at 12°C for 3 weeks and also after one additional week at 20°C. Neither irradiation nor storage affected juice content, organic acids, sugars, peel or pulp color, or consumer sensory preference, although numerous volatiles increased in concentration as a result of irradiation treatment and fruit were somewhat softer. Peel pitting was increased in the irradiated fruit, especially in the fruit stored at 15°C, although it was found that the pitting was largely prevented if physical handling of the fruit was kept to a minimum after irradiation. The results suggest that irradiation could serve as a potential phytosanitary treatment for Chandler and Sarawak pummelos, provided that the fruit is subjected to minimal handling and not temperature abused.

Technical Abstract: Phytosanitary treatments prevent the introduction of pests such as fruit flies into pest free zones, and are often required for international trade. Irradiation is increasingly being considered an alternative to cold and chemical phytosanitary treatments, such as methyl bromide. While 400 Gy is the generic dose for all insects except the adults and pupae of Lepidoptera, 150 Gy is sufficient to control most species of Bacterocera and 1000 Gy is the upper limit of treatment for fresh produce. In this study, the effect of low dose gamma irradiation on the post-harvest quality of two varieties of pummelos (Citrus maxima (Burm.) Merr.), an emerging crop of interest in the US was evaluated. Two varieties of pummelos grown in California were irradiated at target doses of 150 Gy and 1000 Gy and stored at 12°C for 3 weeks and at 20°C for the 4th week to reflect three weeks of sea shipment at the ideal temperature for storage of pummelos and an additional week of retail under ambient conditions. Neither irradiation nor storage affected juice content, organic acids, sugars, peel or pulp color, or consumer sensory preference, although numerous volatiles increased in concentration as a result of irradiation treatment. Irradiation caused an immediate reduction in whole fruit and pulp firmness in ‘Chandler’ but not ‘Sarawak’ pummelos at both 150 Gy and 1000 Gy. Physical handling and exposure to higher temperature resulted in increased peel pitting of irradiated fruit, whereas quality of irradiated pummelos stored at refrigerated temperature for 3 weeks was almost similar to untreated pummelos. Pitting and mold growth in the experimental group increased as the storage time and temperature increased. The results suggest that irradiation can serve as a potential phytosanitary treatment for Chandler and Sarawak pummelos, provided that the fruit is subjected to minimal handling and not temperature abused.