Determination of the odor threshold concentrations and partition coefficients of isothiocyanates from Brassica vegetables in aqueous solution

Abstract

Isothiocyanates (ITCs) are products of the enzymatic breakdown of glucosinolates and may cause pungent flavor notes in vegetables. Limited data on odor threshold concentrations (OTCs) and odor quality descriptors of ITCs exist in literature. These parameters were determined in aqueous samples for 19 isothiocyanates found mainly in Brassica vegetables. Thresholds and odor quality descriptors were ascertained by panelists using flavor profile analysis (FPA). The odor threshold concentrations of ITCs range from 0.005 × 10−3 (octyl ITC) to 0.2 × 10−3 (ethyl ITC) g/L and ITCs were mainly characterized by sulfur, garlic, and Brassica vegetable-like notes. Correlation coefficients were between 0.946 (octyl ITC) and 0.996 (3-(methylthio)propyl ITC) and proved convincing results of OTCs using FPA.Partition coefficients were determined in water, artificial saliva and human saliva to provide an insight into behavior of ITCs in two-phase liquid/air systems. Partition coefficients (K) for human saliva are significantly different from other matrices nevertheless the profile of ITCs K values in water and saliva buffer solution were similar. In human saliva the highest K values were observed for octyl, hexyl and cyclohexyl ITCs, and the lowest for cyclopropyl, benzyl, allyl ITCs. Obtained data provide essential and previously unknown sensory properties for future flavor studies.