Real-time detection of (S)VOCs during hazelnut roasting

(S)VOCs - key to the sensory properties of roasted nuts

Hazelnuts are an important raw material for many chocolate products. Before further processing, they are usually roasted after shelling - a crucial step that gives them their nutty aroma and characteristic color. During roasting, typical volatile and semi-volatile organic compounds (VOCs and SVOCs) are formed, which are decisive for the sensory properties of the roasted nuts.

Traditionally, the roasting process is carried out as short-term high-temperature roasting (HTST) or long-term low-temperature roasting (LTLT). In recent decades, the focus of process optimization has primarily been on shortening the roasting time, e.g. through the use of infrared or fluidized bed roasting. While research has so far mainly focused on the microstructure of the nuts, chemical reactions and the formation of (S)VOCs have remained largely unexplored, although these are of central importance for the sensory profile of the roasted nuts.

S(VOCs) as marker compounds for roasting process optimization

The “RöstNuss live” project aims to analyze these (S)VOCs as marker compounds during the roasting of hazelnuts in real time and thus record dynamic changes in concentration. This provides important insights into the formation and degradation of chemical substances. The aim is to be able to control the roasting process in a targeted manner and detect undesirable off-flavors at an early stage.

To make this possible, the analyses are carried out under different roasting conditions. The methodology includes the use of proton exchange reaction mass spectrometry (PTR-TOFMS) for real-time monitoring of (S)VOC release during roasting in a microchamber, as well as comprehensive gas chromatographic analyses to identify the compounds released.

Precise control of the roasting process for better product quality

The economic significance of the project lies in the improvement of raw material processing and quality assurance. Companies benefit from new findings on the release of value-determining roasting markers, which enable more precise control of the roasting process and thus increase product quality. Improved monitoring of the roasting process could create a competitive advantage, reduce quality differences and minimize rejects due to over- or under-roasting.