Reduced-Pressure Boiling Extraction of Oleuropein Coupled with Ultrasonication from Olive Leaves (Olea europaea L.)

Table 1

Design of factors and levels coded table.

Independent variables	Units	Symbol		Coded levels
			−1	0	1
Temperature	°C		40	50	60
Ultrasonic power	W		480	600	720
Ethanol concentration	% (v/v)		65	75	85
Ratio of solid to liquid	g/mL		1 : 20	1 : 30	1 : 40