Table 4. Taste Recognition Threshold Determination ^a .

Number of Volunteers	Concentration, µg/mL
	50	100	150	250	350	450
1	-	-	+	++	+++	+++++
2	-	+	++	+++	++++	+++++
3	-	+	++	++++	+++++	+++++
4	-	+	++	+++	+++	+++++
5	-	±	++	+++	++++	+++++
6	-	+	++	++++	++++	+++++
7	-	±	+	++	++++	+++++
8	-	+	++	++	++++	+++++

^a - = good, ± = tasteless, + = slightly bitter, ++ = moderate bitter, +++ = bitter, ++++ = very bitter, +++++ = awful.