From feed to food production – Cereal side streams can be utilised as sources of protein and dietary fibre

Brans and other cereal side streams, which currently are mainly used as feed or in energy production, could be utilised as raw materials for protein-rich and highly functional raw materials for foods. They may be suited, for example, to beverages and spoonable products.

Every year, the food industry generates substantial amounts of side streams, such as cereal brans. Instead of using them for food, they are primarily utilised as feed or in energy production. 

“We are wasting high-quality protein and dietary fibre. Using brans in food production would improve resource sufficiency, and they would be viable for healthy diets,” says Pia Silventoinen, who recently defended her doctoral thesis at the Faculty of Agriculture and Forestry, University of Helsinki.

However, the performance of plant-based ingredients, proteins in particular, is often poorer in food applications compared with their animal-derived counterparts. Silventoinen developed in her doctoral research project, carried out at VTT Technical Research Centre of Finland, techniques for producing protein-rich, nutritionally balanced and highly functional raw materials targeted for beverages and spoonable products from cereal side streams – wheat, rice and rye brans as well as barley endosperm fraction.

In her doctoral thesis, Silventoinen optimised sustainable and environmentally friendly dry separation techniques, including dry milling and air classification. They were used to produce protein- and dietary fibre-rich hybrid ingredients, functional properties of which exceeded those of the raw material side streams. Moreover, these properties could be further improved through enzymatic and ultrasound treatment.

“Enzyme-treated protein-rich rice bran fraction could be used as a raw material, for example, in spoonable food products which deliver protein to consumers. It also contains so high amount of dietary fibre that a nutritional claim ‘source of fibre’ could be displayed on the packaging. Similarly, ultrasound-treated barley protein ingredients could be applied in the production of plant-based milk substitutes,” Silventoinen envisions.



Pia Silventoinen's doctoral dissertation "Dry fractionation and functionalisation of cereal side streams for their improved food applicability"


Dry separation techniques

In dry milling, the samples are mechanically crushed in a mill so that proteins, starch, dietary fibre and other components of the material are separated, reducing the sample’s particle size. In other words, the end product of dry milling is a powder that is finer than the raw material.

In air classification, the milled powder is divided into two fractions based on the size, density and shape of the particles in the powder. The separation takes place in an air classification chamber where a fast-spinning classifier wheel allows only the smallest and lightest particles to pass it. In the case of cereal materials, the smallest particles usually contain a lot of protein, whereas larger particles are separated into another fraction.