Effect of Thermal Processing, Press Throughput and Roller-Die Gap on Physicochemical Properties of Broiler Feed Pellets

Abstract

Abstract:The present study aimed to evaluate the effect of thermal processing, press throughput and roller-die gap on pellet physical quality, protein solubility and starch gelatinization in a corn-soybean based broiler diet. The different processing factors were combined in a 2 × 5 × 3 factorial arrangement with eight randomized block consisting of eight production series: two thermal processing treatments (conditioning-pelleting or conditioning-expanding-pelleting), five press throughput levels (18, 21, 24, 27 and 30 ton/h) and three roller-die gap (0.50, 0.75 and 1.00 mm), which resulted in 30 different processed feeds. For determination of pellet durability index (PDI), amount of intact pellets, degree of starch gelatinization and protein solubility, one composed feed sample was collected per treatment in each of eight production series, totaling eight replicates per treatment. Data concerning the amount of intact pellet and protein solubility in KOH were transformed using a variation of Box-Cox transformation in order to fit a normal distribution (P > 0.05). Pellet physical quality was enhanced by conditioning-expanding treatment (P < 0.01), narrower roller-die-gap (P < 0.01) and reduced press throughput (P < 0.01). Protein solubility in KOH was impaired (P < 0.01) in the expander treatment and larger roller-die distance (0.75 mm and 1.00 mm) (P < 0.01). Finally, greater starch gelatinization degree was achieved in expanded treatment (P < 0.01) and in 1.00 mm roller-die gap (P < 0.05). The factors evaluated in this study resulted in interactions and significant effects on physicochemical properties of broiler feed pellets.