Residue analysis of nitric oxide fumigation in nine stored grain and nut products

Authors: YANG, XIANGBING - University Of California; Liu, Yong Biao

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2019
Publication Date: 10/25/2019
Citation: Yang, X., Liu, Y.-B. 2019. Residue analysis of nitric oxide fumigation in nine stored grain and nut products. Journal of Stored Products Research. 84:101521. https://doi.org/10.1016/j.jspr.2019.101521.
DOI: https://doi.org/10.1016/j.jspr.2019.101521

Interpretive Summary: Nitric oxide (NO) is a new fumigant for postharvest pest control. NO fumigation must be conducted under ultralow oxygen conditions because NO reacts with O2 to form NO2. NO fumigation potentially results in nitrate, nitrite, and nitrogen dioxide residues in stored products. In this study, nine grain and nut products were subjected to two fumigation treatments with 3% NO for 24 h, where one treatment was terminated with N2 flush and the other with air flush. Unfumigated products were used as controls. Residues were analyzed at different times after fumigation. When NO fumigation was terminated by flushing with N2, there were no significant differences in nitrate levels for all products between the treatment terminated with N2 flush and the control. However, NO fumigation terminated with air flush had significantly higher nitrate levels as compared with the treatment terminated with N2 flush or the control. For most products, nitrite levels for the NO fumigation terminated with N2 flush were not significantly higher than the control but were significantly lower than the NO fumigation terminated with air flush. NO fumigation terminated with air flush also resulted in significantly higher NO2 dissipation rates than the treatment terminated with N2 flush and the control for all products. This study indicated that termination of NO fumigation with N2 flush is important to reduce NO fumigation residue levels in fumigated stored products.

Technical Abstract: : Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control on fresh and stored products. NO fumigation does not leave residues on fresh fruit and vegetables when conducted properly. In this study, we analyzed nitrate (NO3-) and nitrite (NO2-) levels in liquid extracts and nitrogen dioxide (NO2) dissipation rates as residues of NO fumigation at various times after fumigation on nine stored grain and nut products. Each product was fumigated separately with 3.0% NO for 24 h in two treatments: one treatment (NO-N2) was terminated with nitrogen (N2) flush and the other (NO-Air) was terminated with normal air flush. For NO-N2, NO3- concentrations of all fumigated products were not significantly higher than those of untreated controls at 1, 7, and 14 d after fumigation. NO2- concentrations of all fumigated products from N2 flush were not significantly higher than those of control products 14 d after fumigation. NO2 dissipation rates for most products from NO-N2 treatment showed no significant difference from those for the controls 1 d after NO fumigation, except for beans and wheat, which showed no significant difference at =7 d after fumigation. All products from NO-Air treatment, however, had significantly higher NO3-, NO2- ion concentrations in liquid extracts 14 d after fumigation than those from NO-N2 treatment and the control. NO2 dissipation rates in all products from NO-Air treatment were also significantly higher than those from NO-N2 treatment and the control 21 d after fumigation. Therefore, when terminated properly with N2 flush, NO fumigation did not result in significant increases of NO3-, NO2 , or NO2 as residue in nut and grain products.