Table 5. Multiple regression models for resistance ratio of six metal sensors of electronic nose using the measured peak area of volatile groups as covariate

Sensor	Intercept	Covariate			r²	p-value
Sensor	Intercept	Aldehydes	Hydrocarbons	Pyrazines	r²	p-value
T30/1	<0.001	<0.001^*	<0.001^***	<0.001^***	0.60	<0.001
P10/1	<0.001	<0.001^*	<0.001^***	<0.001^***	0.57	<0.001
P10/2	<0.001	<0.001^*	<0.001^***	<0.001^***	0.59	<0.001
P40/1	<0.001	<0.001^*	<0.001^***	<0.001^***	0.58	<0.001
T70/2	<0.001	<0.001^*	<0.001^***	<0.001^***	0.60	<0.001
PA2	<0.001	<0.001^*	<0.001^***	<0.001^***	0.62	<0.001

Sample size for each quality grade (n=6).
p<0.05
p<0.001.