Analysis Research and Service Center, Food Industry Research & Development Institute, Hsinchu, Taiwan, R.O.C.

(Received: January 18, 2007, Accepted: July 24, 2007)

   The fructans, inulin and oligofructose, were known to possess many of the physiologic properties of dietary fiber (DF).  However, they were not listed as DF on labels of foods that contained them, because they cannot be completely recovered by the precipitate of AOAC enzymatic-gravimetric method.  The main goal of this study was therefore to develop a quantitative method for total DF in fructan-containing foods.  Evaluation was carefully done by combining AOAC 985.29 DF method and AOAC 999.03 fructans method.  In addition to three commercial fructan products, asparagus and tea drink samples were selected and spiked with fructans to carry out the method validation.  The results were all in excellent agreement with the expected values. Also, associated precision and measurement uncertainties were evaluated as well.  Recoveries by the proposed method ranged from 97.02% to 101.35%, with coefficients of variation (CVs) of 0.63~1.17%.  Total DF content was more accurate for combined method than either from AOAC 985.29 only or the sum of determining values from AOAC 985.29 plus AOAC 999.03.

Key words: fructans, inulin, fructo-oligosaccharides, dietary fiber, analytical method