The present invention relates to a novel process for producing hemicellulose fractions from cereal crops, comprising pressurized hot water extraction of hemicellulose fractions from cereal crops in combination with subsequent enzymatic treatments and/or subsequent membrane ultrafiltration to further purify the extracts. The novel process described herein allows for sustainable and scalable extraction and isolation of valuable hemicellulose fractions, especially arabinoxylans (AXs), from cereal side products. The process allows the selective fractionation of arabinoxylans based on their molecular structure and inherent functionalities, which can e.g. be used for the preparation of carbohydrate-based materials with functional properties.