Physicochemical Properties of Extruded Chestnut Fruit at Various Conditions

Abstract

The effects of extrusion conditions on the physicochemical properties of extruded chestnut fruit were determined by analyzing expansion index, specific length, bulk density, water solubility index (WSI), water absorption index (WAI), reducing sugar, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging activity, total phenolic compound, flavonoid content and tannin content. The extrusion conditions contained moisture contents of 22, 25 and 28%, screw speeds of 200 and 250 rpm, melt temperatures of 110, 120 and 130C. The expansion index decreased as the moisture content increased from 22% to 25%. In contrast, the specific length and bulk density increased along with increasing moisture content. WSI and WAI were found to increase through the extrusion process. The reducing sugar, DPPH radical-scavenging activity, total phenolic compound and flavonoid content all decreased. The tannin content of the extruded chestnut fruit was 2.94 to 4.23 mg/g lower than the non-extruded chestnut. Based on these results, extrusion-cooking may be useful for tannin reduction and applied in value-added chestnut related products such as snacks, noodles and beverages etc.