Effects of extruding Persian acron, Quercus brantii flour under different temperature and humidity conditions on its biochemical indices, phenolic compounds and digestibility by common carp, Cyprinus carpio

Extrusion process is widely used in food processing. This process is effective on the anti-nutritional factors present in food raw materials and their digestibility. In treatments 1, 2 and 3 acorn flour with particles less than 250 microns in diameter was mixed with tap water at the rate of 200, 100 and 200 mL per kg of flour and then extruded by a single-axis extruder under the temperature of 135, 135 and 100 °C, respectively. Treatment 4 (control) was not subjected to the conditions of dough preparation and then extruded. Extruding exhibited no significant effect on ash content and non-tannin phenolic compounds of oak flour (p>0.05). However, it significantly decreased the contents of crude protein, crude fat, total phenolic compounds and condense tannins, while led to the elevation in  the digestibility of carbohydrate and protein (p<0.05). In extruded treatments, there were no significant differences in crude protein, crude fat, ash, total phenolic compounds, non-tannin phenolic compounds and condensed tannins. The highest carbohydrate digestibility was observed in treatments 1 and 2, and the highest protein digestibility in treatment 2 (p<0.05). In total, treatment 2 (135 °C and 100 mL tap water per kg flour) was recognized as the best treatment for extruding oak acorn flour for common carp.