Assessment of dietary exposure to flavouring substances via consumption of flavoured teas. Part II: transfer rates of linalool and linalyl esters into Earl Grey tea infusions.

The assessment of dietary exposure via the consumption of flavoured foods is a key element of the safety evaluation of flavouring substances. Linalyl acetate and linalool are the major flavouring substances in Earl Grey teas; the objective of this study was to determine their transfer rates from the tea leaves into the tea beverage upon preparation of a hot water infusion. Spiking experiments revealed a transfer rate of 66% for linalool. In contrast, the transfer rate for linalyl acetate was only 1.9%; in turn, the hydrolysis product linalool (17.0%) and a spectrum (19.9%) of degradation and rearrangement products (monoterpene alcohols, esters and hydrocarbons) were present in the tea beverage. The transfer rates were shown to be proportional to the length of the infusion. The impact of the hot water treatment on the enantiomeric compositions of linalyl acetate and linalool was determined, and structure-dependent experiments were performed by variation of the acyl and the alcohol moiety of the monoterpene ester. Comparative dietary exposure assessments demonstrated the need to take correction factors based on the experimentally determined transfer rates into account. Based on tea consumption data from the UK National Diet and Nutrition Survey (2000/2001), the exposure to linalyl acetate ranges from 0.2 mg day(-1) (average) to 1.8 mg day(-1) (high). The corresponding values for linalool are 4.2 mg day(-1) (average) and 46.6 mg day(-1) (high). The exposure of linalool via consumption of the tea beverage is approximately 26 times higher than that of linalyl acetate, although in the flavoured tea leaves the median content of linalyl acetate is approximately 1.8 times higher than that of linalool.

Assessment of dietary exposure to flavouring substances via consumption of flavoured teas. Part 1: occurrence and contents of monoterpenes in Earl Grey teas marketed in the European Union.

Estimations of dietary exposure via the consumption of flavoured foods play a central role in the safety evaluation of flavouring substances. To assess uncertainties, actual data regarding the occurrence and concentration levels of flavouring substances were determined in commercially available flavoured foods, using Earl Grey tea as an example. The contents of the consistently occurring monoterpenes linalyl acetate, linalool, limonene, ß-pinene and γ-terpinene were determined in 90 tea samples purchased in 10 European Union member states. Rather narrow frequency distributions were observed for the major compounds linalyl acetate and linalool. The factors (1) country of purchase, (2) source of the products (national/international brands versus private label brands versus speciality tea shops), and (3) enantiomeric purities of the flavouring substances had no significant impact on the contents of the flavouring substances. Only in teas sold as loose leaves were the median contents of linalyl acetate and linalool (66% and 39%, respectively) higher than in teas offered in tea bags. Significant losses of flavouring substances were observed on storage of teas, indicating an impact of the type of packaging and the flavouring technology on the contents of flavouring substances in the product finally consumed.