Iodide reaction times of peroxyhemiacetals (PHAs) in the peroxide value titration; implications for the testing of citrus oils
2020
Calandra, Michael J. | Wang, Ying | Beckett, Courtney
Limonene and linalool are major components in many essential oils, and both may autoxidize under certain conditions to form terpene hydroperoxides (THPs), which are reported to be sensitizers that may cause allergic contact dermatitis. This laboratory previously reported that peroxyhemiacetals (PHAs) may be present in some citrus oils, formed by reaction of THPs with endogenous aldehydes. It was also shown that PHAs can dissociate back to the corresponding THPs in polar solvation environments. Because of this potential for reversion to THPs, the analysis of PHAs is important in the context of measuring peroxide values in products. The fragrance industry currently utilizes iodometric titration to monitor THP levels in many raw materials; the currently accepted method requires that THPs in the sample are allowed to oxidize excess added iodide to molecular iodine for a one‐minute reaction time. The iodine generated is then titrated with thiosulfate to give the peroxide value. This paper reports on the iodide reaction time required for PHAs to be quantitatively measured by such an iodometric titration technique, and on the implications to citrus oil raw material testing.
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