Lipid oxidation and volatile compounds of almonds as affected by gaseous chlorine dioxide treatment to reduce salmonella populations

Authors: WANG, WENLI - Zhejiang University; Smith, David; Ngo, Helen; Jin, Zhonglin; MITCHELL, ALYSON - University Of California; Fan, Xuetong

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2023
Publication Date: 3/22/2023
Citation: Wang, W., Smith, D.J., Lew, H.N., Jin, Z.T., Mitchell, A., Fan, X. 2023. Lipid oxidation and volatile compounds of almonds as affected by gaseous chlorine dioxide treatment to reduce salmonella populations. Journal of Agricultural and Food Chemistry. 71(130):5345-5357.

Interpretive Summary: Almonds, which are rich in “good” lipids and other nutrients, have been implicated in several Salmonella outbreaks. Earlier studies conducted by ARS researchers, have demonstrated that gaseous chlorine dioxide is effective in reducing populations of Salmonella on almonds, especially at elevated treatment temperatures. However, whether the treatment leads to undesirable chemical changes in almonds is unclear. The present study was conducted to evaluate effects of gaseous chlorine dioxide fumigation on volatile compounds and lipid oxidation of almonds, during post-fumigation storage. Gaseous chlorine dioxide increased lipid oxidation and the formation of many volatile flavor compounds that originate from lipids. In addition, several chlorine-containing compounds were formed in treated almonds, though most of them decreased to non-detectable levels during storage. The results may help the almond industry in deciding on the application of the technology, in order to improve the safety of almonds.

Technical Abstract: The effects of gaseous chlorine dioxide (ClO2) treatment, applied to inactivate Salmonella, on lipid oxidation, volatile compounds and chlorate levels of dehulled almonds were evaluated during a 3-month accelerated storage at 39 °C. At treatment levels that yielded a 2.91 log reduction of Salmonella, ClO2 promoted lipid oxidation as indicated by increased peroxide values, total acid number, conjugated dienes and thiobarbituric acid-reactive substances. Furthermore, several chlorine-containing volatile compounds including trichloromethane, 1-chloro 2-propanol, 1,1,1-trichloro-2-propanol, and 1,3-dichloro-2-propanol were identified in ClO2 treated samples. However, all the volatile chlorine-containing compounds except trichloromethane decreased to non-detectable levels during the 3 months of storage. Chlorate (26.4±5.1 'g/g) was found on the ClO2-treated samples. The amounts of non-ethanol alcohols, aldehydes and carboxylic acids increased following ClO2 treatments. Some volatiles such as 2,3-butanediol and 2-methyl-1-propanol that were present in non-treated samples became non-detectable during post-ClO2 treatment storage. Overall, our results demonstrated that gaseous ClO2 treatment promoted lipid oxidation, generation of volatiles of lipid origin, and several chlorine-containing compounds.