QUANTITATION OF ALLYL ESTERS, LINALOOL, CITRAL, AND LINALYL ACETATE IN YOGURT AND SOFT DRINKS BY MEANS OF GC-MS

The pineapple and tropical fruit flavor of fruit yogurts and soft drinks is often supported by the addition of allyl esters - especially allyl hexanoate [1]. Allyl esters belong to the group of carboxylic acid esters and can be hydrolyzed to allyl alcohol. Allyl alcohol may be hepatotoxic because it is metabolized by alcohol dehydrogenase to acrolein [2]. Therefore, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has set a group ADI of 50 μg/kg body weight per day for allyl alcohol for three compounds (allyl hexanoate, allyl heptanoate and allyl isovalerate), which was confirmed for other allyl esters in subsequent studies [3]. In addition to allyl esters, the flavoring substances linalool, citral and linalyl acetate also contribute to the fruity and citrus-like aroma of foods and have a low group ADI value of 500 μg/kg body weight per day, expressed as citral [4]. Despite the toxicological assessment and potential health risks, there is still no validated method for the quantitation of allyl esters and the other flavorings. For this reason, the German National Reference Laboratory for Food Additives and Flavorings developed a GC-MS-based stable isotope dilution analysis for the quantitative determination of 22 allyl esters as well as linalool, citral (neral and geranial) and linalyl acetate.

First, suitable extraction methods were developed for the matrices “yogurt” and “soft drink”. The chromatographic and mass spectrometric parameters were then optimized in order to study all compounds as selectively as possible. Validation parameters such as linearity, limit of detection and limit of quantification, repeatability and trueness were tested. Finally, the newly developed approach was applied to real samples. For instance, levels of 1‑12 mg/kg (yogurt) and 1‑24 mg/l (soft drinks) were determined for the compounds allyl hexanoate, linalool, allyl cyclohexane propionate and allyl phenoxy acetate. For the first time, a GC-MS-based analytical method was developed for the quantitative determination of allyl esters in yogurt and soft drinks. This will provide a powerful tool for estimating dietary exposure to allyl esters and ensuring the monitoring of these compounds in certain food stuff.