Instrumental and sensory analysis of the flavour of French beans (Phaseolus vulgaris) after different rehydration conditions

The influence of rehydration conditions on the flavour of French beans (Phaseolus vulgaris) was evaluated. Dried French beans were rehydrated in closed and open flasks at 100°C for 0, 5, 10, 15, 30, 45 and 60 min. The odour active volatile compounds were released in a mouth model system and determined by gas chromatography/sniffing port analysis (GC/SP) and GC/mass spectrometry. Texture characteristics were analysed by Kramer shear press measurements. Moreover, the flavour of the beans was evaluated by descriptive sensory analysis. In GC/SP, extended rehydration resulted in increases in the intensities of 2-butenal, 2-methyl-2-butenal, 1-octen-3-one and one unknown compound. Intensities of several attributes, such as "chemical", "mealy", "mushroom" and "musty" increased with extended rehydration, while intensities decreased for "grassy" and "citrus" attributes. Instrumental and sensory analysis of the texture of the beans revealed a gradual decrease with extended rehydration. In general, rehydration in open versus closed flasks decreased the odour intensities of volatile compounds as assessed by GC/SP, as well as the intensities of attributes as measured by sensory analysis. Correlation of sensory attributes and volatile compounds showed that these compounds made a major contribution to the difference in flavour of French beans resulting from rehydration conditions.