Table 4.
Polynomial equation calculated by RSM program for air-classified fraction of wheat bran

	Response	The second order polynomial1)	R2
Fine fraction	Classification Ratio (%)	Y1=-60.28889-0.0279X1+0.10662X2-0.052X3+0.000005X12-0.000019X22+0.000049X32	0.9105
	Average particle size (µm)	Y2=228.2783+0.0102X1-0.0067X2- 0.7074X3+0.0000004X12+0.0000001X22+0.000693X3 2	0.9364
	Total dietary Fiber (g/100 g)	Y3=-6.7915-0.005860X1+0.0354X2-0.0034X3	0.8461
Coarse fraction	Classification Ratio (%)	Y4=161.6555+0.028X1-0.0177X2+0.0516X3-0.000005X12+0.000019X22-0.00005X32	0.9113
	Average particle size (µm)	Y5=2098.299-0.1488X1-0.177X2-0.0215X3+0.00002X12+0.000153X22-0.000073X32	0.9327
	Total dietary Fiber (g/100 g)	Y6=89.2924+0.00088X1-0.0188X2-0.0374X3	0.8170

1)X₁: Mill grinding speed (rpm), X₂: Separate reverse wheel speed (rpm), X₃: Air classification reverse wheel speed (rpm), Y=b₀+b₁X₁+b₂X₂+b₃X₃+b₁₂X₁X₂+b₁₃X₁X₃+b₂₃X₂X₃+b₁₁X₁²+b₂₂X₂²+b₃₃X₃²