The objective of this collaborative study was to evaluate the Total Dietary Fiber (TDF) contents in extruded food products containing different levels of grape pomace (GP), the residue of grapes after wine making, using enzymatic and gravimetric procedures. The products were formulated with yellow corn grits, GP and water. The grape pomace contents in the formulas were 5, 10 and 15%. The products without GP were used as controls.  At each GP level, the mixture were extruded at moisture level of 15, 17 and 19% and at constant temperature120°C. Twelve extruded samples were ground to smaller particles, then digested with heat stable α-amylase, protease and amyloglucosidase at the optimal pH and temperature of each enzyme. Ethanol was added to precipitate the soluble dietary fiber. The residue was filtered and washed with ethanol and acetone. After drying, the residue was weighed and the ash content of the residue was determined. The TDF determination of each sample was conducted in duplicate. Results: The TDF content of the extruded product increased with increasing amount of GP almost linearly, and was affected by the moisture of formula. The TDF of extruded product was 6.6-6.8% without GP, 8.2-9.1% with 5% GP, 10.7-13.4% with 10% GP and 14.4-16.2% with 15%GP, depending on the moisture of formula. The TDF content of Coefficient of Variation (CV) values range from 0.9-6.6% for the 9 out of 12 samples, but the CV for 3 samples were in the range of 20.0-26.9%, respectively. The study suggests that GP could serve as a dietary fiber source in extruded food products.<br/>

Determination of total dietary fiber in extruded food products containing grape pomace

251st National Meeting (2016)

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