Functional properties and optimization of dietary fiber concentrate from sago hampas using response surface methodology

Abstract

Sago hampas, whose major components are fiber and starch, is an underutilized by-product generated from starch extraction of sago stems. In order to increase its added value and applications, sago hampas could be developed into dietary fiber concentrate. This research purposed to obtain the optimum condition of enzymatic hydrolysis process of sago hampas to isolate the dietary fiber components. A central composite design of response surface methodology (RSM) was used to optimize processing variables, namely, sago hampas slurry concentration (0.1–0.2 kg/kg), reaction time (45–135 min), and enzyme concentration in the substrate (10–35 mL/kg). Enzymatic hydrolysis using α-amylase at 108 °C was employed to remove starch components (becoming maltodextrin), escalate dietary fiber content, and modify the crystallinity of fiber. The goals of optimization were to maximize total dietary fiber (TDF), water-holding capacity (WHC), and oil-holding capacity (OHC) of the dietary fiber concentrate and to maximize dextrose equivalent (DE) of the maltodextrin solution obtained. The optimum process condition was found when the variables sago hampas slurry concentration, reaction time, and enzyme concentration were 0.14 kg/kg, 121 min, and 25 mL/kg, respectively. The optimal condition was verified by laboratory experiment resulting in TDF, WHC, OHC, and DE of 92.98 %, 26.34 g of water per g of sample, 5.64 g of oil per g of sample, and 10.37 %, respectively. TDF increased while the starch decreased significantly following conversion to dietary fiber. It is associated with the improvement in the functional properties of dietary fiber. The OHC, cation exchange capacity, emulsifying activity, swelling capacity, and solubility all exhibited significant increases. The morphological structure of the dietary fiber concentrate revealed a fiber matrix degradation with a high level of fiber porosity while the crystallinity was decreased from 61 % to 42 %. The properties of dietary fiber concentrate indicate appropriate parameters for food industry applications.