Extraction of Dietary Fiber from Corn Silk (Zea mays) and Its application in Food Products

Abstract

The purpose of this study was to investigate the possibility of extracting dietary fiber (DF) from corn silk, which is one of the industrial waste products from corn milk processing in Thailand, and to compare the difference in pre-treatment steps before extraction by studying the physico-chemical properties of the resulting fibers. The potential in application to food products was also studied. The pre-treatment steps included overnight drying at 50°C and grinding. After alcoholic extraction, the physico-chemical properties of dietary fiber from dried (pre-treated) corn silk (DDF) and from fresh corn silk (FDF), i.e. water and oil holding capacity (WHC and OHC), emulsifying activity (EA), emulsion stability (ES) and pH were determined. The results showed that the total dietary fiber (TDF) content of DDF and FDF was 50.8 % and 76.9 %, insoluble dietary fiber (IDF) was 44.3% and 65.0% and soluble dietary fiber (SDF) was 11.90% and 6.5%, respectively. WHC of DDF and FDF were significantly different (p≤0.05) with the
values being 4.9 and 9.8 g/g sample, respectively. OHC values of DDF and FDF were also significantly different at 2.8 and 5.4 g/g sample,  respectively. EA of DDF and FDF was 2.1 % and 4.4%, while ES was 4.6% and 13.0%, respectively. The pre-treatment steps before extraction significantly (p≤0.05) affected the physical properties of corn silk fiber. The application of corn silk fiber into foods was examined on cake and deep-fried chicken batter. The results showed that only FDF increased the volume of cake when being used to substitute for wheat flour at 15% level. However, the finished product had a darker color compared to the control, resulting in a decrease of overall acceptability score from the sensory evaluation. Nevertheless, the corn silk fiber-added cakes contained more than 10% of the daily recommendation of dietary fiber intake. For deep-fried chicken batter, addition of DDF and FDF fiber at 3% level in the batter suspension did not significantly increase (p>0.05) the yield and batter pick-up and did not reduce oil absorption while the sensory acceptability scores were not different from those of the control product. Corn silk fiber, especially FDF type, exhibited good physicochemical properties and can be used as an additional fiber ingredient in some food products.