Impact of ultra-fine milling and air classification on biochemical and techno-functional characteristics of wheat and rye bran

Pia Silventoinen, Anni Kortekangas, Dilek Ercili-cura (Corresponding Author), Emilia Nordlund

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19 Citations (Scopus)
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Dry milling and air classification were applied to produce three different ingredients from wheat and rye brans. Dried and pin disc-milled brans having particle size medians of 89–131 µm were air classified to produce protein- and soluble dietary fibre-enriched hybrid ingredients (median particle size 7–9 µm) and additionally brans were ultra-finely milled (median particle size 17–19 µm). The samples were characterised in regard to their composition and techno-functional properties. In air classification, protein content increased from 16.4 and 14.7% to 30.9 and 30.7% for wheat and rye brans, which corresponded to protein separation efficiencies of 18.0 and 26.9%, respectively. Concurrently, the ratio between soluble and insoluble dietary fibre increased from 0.22 to 0.85 for wheat and from 0.56 to 1.75 for rye bran. The protein- and soluble dietary fibre-enriched wheat bran fraction showed improved protein solubility at alkaline pH when compared to pin disc- and ultra-finely-milled wheat bran, whereas less difference between the wheat ingredients was observed at native and acidic pH. The protein- and soluble dietary fibre-enriched rye bran fraction exhibited lower solubility than the pin disc- or ultra-finely-milled rye brans at all the studied pH-values. Ultra-fine milling alone decreased protein solubility and increased damaged starch content when compared to the pin disc-milled brans. Both protein enrichment and ultra-fine milling improved colloidal stability in comparison to the pin disc-milled raw materials. The lowest water and oil binding capacities were obtained for the protein-enriched fractions. Ultrasound-assisted emulsification of the protein- and soluble dietary fibre-enriched fractions and the ultra-finely-milled brans revealed no major differences in the visual quality or stability of the emulsions. The results suggest that modification of the techno-functional properties of cereal brans may be acquired via both air classification and ultra-fine milling.
Original languageEnglish
Article number109971
JournalFood Research International
Publication statusPublished - 1 Jan 2021
MoE publication typeA1 Journal article-refereed


  • cereal
  • protein
  • fiber
  • Dry fractionation
  • Particle size
  • Protein solubility
  • Pasting properties
  • emulsion


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