Integration of inulin determination in the AOAC method for measurement of total dietary fibre.

A suitable modification of the standard AOAC method for the measurement of dietary fibre is proposed to quantitatively include beta-fructans in the determination of the soluble dietary fibre fraction and as a consequence in the related total dietary fibre fraction. The standard AOAC method is modified by including a preheated commercial inulinase, Novozym SP 230, to the amyloglucosidase incubation step. It was previously outlined that this commercial inulinase contains some pectolytic activity. It is now demonstrated that a heat pretreatment of this enzyme preparation at 60 degrees C for 2 h eliminates this pectolytic activity while keeping sufficient activity to hydrolyse all the inulin from the soluble fibre fraction.