Table 6.

The effect of conditioning temperature and die speed on SEC of the pellet mill and pellet quality^a

	Conditioning temperature, °						Probability, P <
	74 °C			85 °C			74 °C, die speedb		2 × 2 factorialc
Die speed, rpm	127	190	254	190	254	SEM	Linear	Quad	Temp	RPM	Temp × RPM
SEC,d kWh/MT	10.9	8.9	9.0	9.6	9.1	0.41	0.001	0.001	0.578	0.106	0.074
PDI, %
Std tumblee	85.8	83.9	83.3	91.2	91.2	0.58	0.001	0.082	0.001	0.245	0.313
Mod tumblee	68.6	64.1	61.7	80.3	80.6	1.84	0.001	0.262	0.001	0.198	0.103
NHP 30 sf	78.1	73.1	70.8	87.7	87.8	1.51	0.001	0.207	0.001	0.214	0.175
NHP 60 sf	56.6	46.3	43.3	78.7	78.2	2.46	0.001	0.063	0.001	0.257	0.433

^aDiets were conditioned for approximately 30 s prior to pelleting (Model 3016-4 CPM Co., Crawfordsville, IN) on a 4.8- × 44.5-mm die. Treatments were replicated three times. Date of production served as a random effect to account for any environmental changes that may have influenced pelleting parameters.

^bLinear and quadratic contrasts testing the effect of increasing die speed when conditioning at 74 °C.

^cFactorial analysis consisted of two conditioning temperatures (74 and 85 °C) and two die speeds (190 and 254 rpm).

^dSpecific energy consumption was calculated according to Stark (1994) based on production rate and average pellet mill motor amperage over the run.

^eStandard and modified tumble box methods according to ASAE S269.4 with three 19-mm hex nuts used for modification.

^fHolmen NHP100 (TekPro Ltd, Norfolk, UK) pneumatic pellet tester set at 70 mbar forced air with 30 or 60 s run time.