Relationship between sensory perception and flavour-active volatile compounds of germinated, sourdough fermented and native rye following the extrusion process

Relation between sensory profiles and flavour-active volatile compounds was explored on six rye extrudates, representing two rye cultivars (Amilo and Akusti) and three pretreatments (germination, sourdough fermentation and milling), prior to the extrusion cooking. The processing method used before the extrusion cooking was shown to be very decisive for the perception; the germinated, sourdough fermented and milled rye extrudates clustered to cultivar pairs according to their pretreatment on the regression plot including the whole sample set. Germinated, extruded rye was cereal and fresh in flavour, and hard in texture, and dimethyl sulphide and 2-methylbutanal were highly related to these sensory attributes. Sourdough fermented, extruded rye had a sour, intense flavour and aftertaste, and porous texture, the most relevant volatile compounds being furfural, ethyl acetate, 3-methylbutanol and 2-methylbutanol. The extrudates prepared from rye flour were very mild in flavour and somewhat tough in texture, and 2-ethylfuran, 2-methylfuran, hexanal and pentanal were the dominating volatile compounds.

The present study clearly demonstrated the effect of processing on adjusting the flavour of rye. Sensory perception and volatile compounds of germinated, sourdough fermented, and native rye were substantially different, and they remained variable after the second treatment, i.e. the extrusion process. The pretreatment process was shown to be most dominant in the formation of the flavour of the rye extrudates. The rye cultivar had an unsubstantial effect on the sensory profiles.