Twin Screw Extrusion Processing of Diet for Mass Rearing the Pink Bollworm

The use of a long barreled twin screw extruder (L/D = 39.7) for continuous processing of diet (63% moisture, w.b.) for mass rearing of the pink bollworm moth (Pectinora gossypiella) was studied. Heating to obtain sterile to near-sterile product (T > 134°C) required the use of a two-step process. Feed at 45 to 50% moisture was heated to the treatment temperature; then additional water was added to 63% moisture. One or more pairs of restriction discs were required between the heating and dilution sections. Products with rough surfaces were formed by steam expansion or air atomization. No significant losses of thiamine occurred during processing. The process is now in operation in a large scale mass rearing facility.