Table 4.

Number of correct answers, estimated magnitude of sensory differences (d’) and assessors’ confidence level in the 2-AFC test (n = 24) where coffee with increasing concentrations of the five organic acids. Asterisks denote statistically significant differences from control assessed by exact binomial test (*p < 0.05; **p < 0.01; ***p < 0.001).

Acid	Concentration(g/l)	Correct answers(n = 24)	Magnitude of difference (d’)	Not confident	Fairly confident	Completely confident
Acetic	0.16	12	0	0	4	8
	0.20	12	0	3	6	3
	0.25	10	0	3	5	2
	0.31	14	0.3	4	7	3
Citric	0.16	19**	1.1	6	5	8
	0.20	18*	0.9	4	4	10
	0.25	19**	1.1	5	5	9
	0.31	22***	1.9	2	10	10
Lactic	0.16	13	0.1	2	5	6
	0.20	17*	0.8	4	8	5
	0.25	19**	1.1	4	8	7
	0.31	17*	0.8	4	4	9
Malic	0.16	10	0	2	8	5
	0.20	18*	0.9	4	9	4
	0.25	18*	0.9	4	2	12
	0.31	21***	1.6	3	5	13
Phosphoric	0.16	16	0.6	5	4	7
	0.20	13	0.1	3	4	6
	0.25	17*	0.8	3	4	10
	0.31	19**	1.1	3	4	12