Flavour and stability of rye grain fractions in relation to their
chemical composition
Wholegrain rye is health-beneficial, but intensive and bitter flavour of rye foods, supposedly caused by specific
phenolic compounds and small peptides, restricts its use. The aim was to study the stability and sensory quality
of rye grain fractions in relation to their chemical composition. In addition to distinctive sensory and chemical
properties of wholegrain flour, endosperm-rich fraction and two differently prepared brans, the rye fractions
had differences in their stability. The endospermfraction had the poorest stability and mildest flavour. The rancid
flavour was related to free fatty acids. The bran, intense and bitter in flavour, but more stable, had the highest
content of phenolic compounds. The high content of phenolic compounds of bran contributing to its bitterness
probably also improved its stability by reducing the formation of flavour-active lipid-derived oxidation products.
Stability of the rye bran made by an air-classification process was inferior to the bran made by a conventional
sieving process, despite similar content of phenolic compounds. Changes in the development rate of rancidity
and intensity of flavour were faster in the air-classified than in the sieved bran. This could be due to different microstructure
and particle size of the brans, influencing oxidation susceptibility.