Abstract:

This study is intended to develop an analytical method to determine polyfructose in milk powder using enzymatic
hydrolysis combined with ion chromatography. Fructanohydrolase and glucose polymerase were added to acetate buffer
and incubate in 60 ℃ water bath for 1 h to completely decompose polyfructose and maltodextrin into glucose and fructose.
The contents of fructose and sucrose before and after the enzymatic hydrolysis were analyzed by ion chromatography
with electrochemical detection so that the content of the polyfructose could be calculated from the measured results.
Chromatographic separation was carried out on a PA-1 column (250 mm×4 mm, 4.6 μm) by gradient elution at a flow rate
of 0.8 mL/min. The calibration curve was y = 0.348 8＋3.694 0x, r = 0.999 9 for fructose, and y = 0.174 8＋4.350 4x,
r = 0.999 7 for sucrose. The average recovery was 97.4% with a relative standard deviation of 3.56%. Limit of
quantification was 1.3 ng/mL for fructose and 1.2 ng/mL for sucrose. This method was simple, sensitive, reproducible and
applicable to determine polyfructose in modified milk powder and infant formula.

Key words: milk powder, fructanohydrolase, polyfructose, ion chromatography