The effect of different temperatures applied during extrusion on the nutritional value of faba bean and degradation of phytic P isomers

This study determined the effect of varying extrusion processing temperatures on the content of phytic P isomers (InsP6–InsP3), myo-inositol, nutrients, and antinutritional factors in faba beans and went on to estimate the nutritional value of these extrudates and the effect they had on InP6-Insp3 contents in the gastrointestinal tract of birds. The study was performed on 240 male Ross 308 strain broiler chicks (1-day old) which were divided into six experimental groups (20 replications/group; two birds/replication). A maize/soybean meal basal diet was mixed (60:40 ratio) with faba beans that were fed either raw or extruded at 110, 115, 120, or 125 °C. The extrusion process decreased the level of trypsin inhibitors, phytic P and resistant starch and reduced the content of InsP6 and increased InsP5, InsP4, and InsP3 and myo-inositol. Digestibility of dry matter, crude protein, starch and apparent metabolisable energy (AME) and nitrogen-corrected (AMEN) of the beans were optimized when they were extruded between 110 and 115 °C. Increasing the temperature of extrusion had a linear and quadratic negative effect on nutrient (except starch) digestibility and AMEN value. Increasing extrusion temperatures also resulted in the reduction in ileal InsP4 and InsP3 and an increase in myo-inositol concentrations. Thus, it can be concluded that extrusion can enhance the nutritional value of faba bean by improving the digestibility of several nutrients while at the same time degrading some antinutritional factors including InsP isomers. However, higher temperatures can compromise nutrient digestibility. In the current study, we concluded that the optimal temperature of extrusion is 110–115 °C.