Evaluation of the effect of extrusion cooking of jackbean ( Canavalia ensiformis L.) seed on short-term feed intake in chicks

Abstract

Experiments were conducted to investigate the relationship between various extrusion cooking conditions, the chemical composition of jackbean samples and the short-term control of food intake in chicks. All data were analysed using a principal component analysis computerized program. Ground jackbean was extruded on a pilot-scale twin-screw extruder. Water addition at the feed inlet, filling rate of the screws, barrel temperature in the last section of the extruder and reverse-screw element position were tested as operating variables. Three sets of experiments (A, B and C) and a total of 20 trials were performed. Process variables were specific mechanical energy, product temperature measured at the die and resulting pressure exerted on the shafts. Also, colour values were determined on all jackbean samples. Experimental diets containing 300 g kg −1 extruded jackbean were fed to 7-day-old chicks to measure the short-term variations in food intake. Inactivation of the lectin (concanavalin A) was monitored using a haemagglutination assay. In addition, starch solubility, and reactive lysine and canavanine contents were determined on samples from Experiment A. Pilot-scale extrusion cooking of Canavalia appears to be feasible: water addition decreased energy consumption ( r = −0.76), filling rate and position of the reverse-screw element are correlated to product temperature ( r = +0.61 and −0.66, respectively). Food intake inhibition index, used as an expression of toxicity for chicks, was reduced in proportion to a decrease in the amount of water added and to the filling rate ( r = +0.8 and +0.6, respectively). The minimum food intake inhibition index was 70% in Experiment A, 61% in Experiment B and 35% in Experiment C according to our experimental conditions. The lower the food intake inhibition index, the more delayed the inhibition effect on food intake. Lightness and specific mechanical energy appeared to be accurate indicators of the detoxification level ( r = +0.85 and +0.72). No significant relationship was apparent between toxicity and haemagglutination activity of the meal. Additional research is needed to understand the high correlation found among canavanine, reactive lysine content and the reduced feed intake shown by the chicks.