Abstract:

Total dietary fiber (TDF) was prepared from millet bran by enzymatic-gravimetric method. In order to improve
its in vitro cholesterol-binding capacity, TDF was modified with cellulase. Based on single factor experiments, an L9 (34)
orthogonal array design was employed to optimize four parameters for enzymatic modification. The optimal enzymatic
treatment conditions that provided a 2.40-fold increase in cholesterol-binding capacity compared with the original TDF (14.21
versus 5.91 mg/g) were determined as 3.8, 140 U/g, 55 ℃ and 3 h for initial pH, cellulase amount, hydrolysis temperature
and time, respectively. Comparative studies between the native and modified TDF showed the cellulase treatment changed
the monosaccharide composition of TDF and resulted in formation of more cellobioses in the cellulase-modified dietary fiber
(CMF). Compared with TDF, CMF was rougher and had more hydrophobic groups. These physicochemical changes may be
closely related to high cholesterol-binding capacity of CMF in vitro.

Key words: millet bran, total dietary fiber, cellulase, cholesterol-binding capacity, physicochemical analysis