A process for manufacturing transglycosylation products. According to the process, a starch derivative is reacted at acidic conditions with an alkanol containing 1-6 hydroxyl groups and the reaction product is recovered as such or it is subjected to further processing. According to the method, the transglycosylation reaction between the starch derivatives and the alkanol is carried out in a reactive extrusion process, whereby the reaction can essentially be performed in the absence of liquid media at high yield. The invention also relates to new transglycosylation products of starch derivative, containing anions derived from a phosphorus-containing acid, which are chemically bonded to the product.