The Impact of Whirlpool Hop Addition on the Wort Metal Ion Composition and on the Flavor Stability of American Style Pale Ales Using Citra^® Hop Extract and Pellets

Figures & data

Table 1. ICP-OES calibration details.

Element	Wavelength (nm)	R^2	Limit of detection (ng/g)	Max. calibration (ng/g)
Ca	317.933	0.99999	1.91	24000
K	766.491	0.99986	4.02	6000
Mg	279.079	0.99981	13.5	12000
Na	589.592	0.99980	0.799	1200
Cu	324.754	0.99997	0.452	300
Fe	238.204	0.99999	0.385	2400
Mn	257.611	0.99993	0.0960	300
Zn	231.856	0.99928	0.0530	300

Table 2. Overview of the hopping levels and hop products applied for the benchtop wort boiling trials.

Sample	Kettle hop addition		Whirlpool hop addition
	hop product	dosage (g/L)^a	hop product	dosage (g/L)
control	bittering extract	0.09	–	–
ex0.5	bittering extract	0.09	Citra^® extract	0.5
ex1.0	bittering extract	0.09	Citra^® extract	1.0
ex1.5	bittering extract	0.09	Citra^® extract	1.5
ex2.0	bittering extract	0.09	Citra^® extract	2.0
ex3.0	bittering extract	0.09	Citra^® extract	3.0
pe2.9	bittering extract	0.09	Citra^® pellets	2.9
pe5.8	bittering extract	0.09	Citra^® pellets	5.8
pe8.7	bittering extract	0.09	Citra^® pellets	8.7
pe11.6	bittering extract	0.09	Citra^® pellets	11.6
pe17.4	bittering extract	0.09	Citra^® pellets	17.4

a Hop dosage of 0.09 g/L bittering extract targeting 20 IBU in the wort.

Figure 1. Analysis of variance (ANOVA) applied to the concentrations of selected metals quantitated in wort and hot trub samples obtained by benchtop wort boiling trials. Concentrations in hot trub were converted according to determined dry matter. Displayed are means of the three independent replicates, error bars represent standard deviations. *Significant differences (p ≤ 0.05). **Highly significant differences (p ≤ 0.001).

Table 3. Original gravity, real extract, alcohol, degree of fermentation, color, pH, and bitterness in the beer samples.

Sample	Original gravity (°P)	Ereal (%)	Alcohol (% vol.)	ADF (%)^a	Color (EBC)	pH	IBU^b
control	14.65	5.11	6.39	80.6	8.1	4.34	16
ex0.5	14.81	5.28	6.39	79.6	7.4	4.30	24
ex1.0	14.76	5.10	6.47	81.0	7.8	4.40	26
ex2.0	15.09	5.03	6.75	82.5	8.1	4.43	29
pe2.9	14.82	5.08	6.53	81.4	8.6	4.48	32
pe5.8	14.96	5.33	6.46	79.7	8.3	4.51	44

a Apparent degree of fermentation.

b International bitter units.

Table 4. Frequency of the flavor attributes selected by the panelists (N = 16) during CATA sensory evaluation of the beers produced with different whirlpool hop additions.

Attributes	Frequency of attributes for beer samples by sensory panel						Sum	% of max
	ctrl	ex0.5	pe2.9	ex1.0	pe5.8	ex2.0
citrus	5	8	7	3	9	8	40	100
fruity	9	7	8	6	3	4	37	93
resinous*	1^a	8^b	3^ab	5^ab	8^b	7^ab	32	80
sweaty*	1^a	5^ab	0^a	6^ab	9^b	7^ab	28	70
floral	4	5	4	3	6	5	27	68
tropical	2	6	4	5	5	4	26	65
herbal	4	4	4	3	4	6	25	63
grassy	7	2	3	5	4	3	24	60
sweet aromatic	4	3	4	3	3	1	18	45
vegetal	2	0	4	6	2	3	17	43
overripe fruit	1	1	2	5	2	3	14	35
honey	5	1	4	2	1	0	13	33
melon	3	3	1	3	1	1	12	30
woody	2	1	2	2	3	1	11	28
cardboard	0	1	1	1	2	2	7	18
dried fruit	2	1	0	0	0	1	4	10
DMS	2	0	1	1	0	0	4	10
spicy	1	1	2	0	0	0	4	10
caramel	1	1	0	0	0	0	2	5
nutty	0	0	0	1	0	0	1	3

* Significant differences between samples according to Cochran’s Q test (p ≤ 0.05). Samples having the same superscript are not significantly different at p = 0.05.

Figure 2. Radical generation in beer samples at forced oxygen exposure monitored over time by ESR spectroscopy at 60 °C.

Table 5. Cochran’s Q test applied to the beer sensory results obtained by CATA with a trained sensory panel over 12 weeks of forced aging.

Flavor attribute	p-value
caramel*	0.000
cardboard*	0.000
citrus*	0.047
DMS	0.251
dried fruit*	0.000
floral	0.268
fruity	0.436
grassy	0.131
herbal	0.992
melon	0.940
nutty	0.185
overripe fruit	0.070
resinous*	0.011
spicy*	0.048
sweaty*	0.008
sweet aromatic*	0.043
tropical	0.718
vegetal	0.804
woody	0.227
honey*	0.027

* Significant differences according to Cochran’s Q test (p ≤ 0.05).

Figure 3. Overall aging scores of the six beers produced with different whirlpool hop dosages of pellets or extract over the 12 weeks of forced aging at 30 °C displayed in % as calculated with the CATA frequencies of the age-related flavor attributes caramel, cardboard, dried fruit, honey, nutty, overripe fruit, and sweet aromatic.

Figure 4. Correspondence Analysis (CA) and Cochran’s Q test (p ≤ 0.05) applied to the beer sensory results obtained by CATA with a trained sensory panel over 12 weeks of forced aging displayed as factors F1 vs. F2 (left) and factors F1 vs. F3 (right) overall accounting for 57.04% of the total variation.

Table 6. ANOVA and Fisher multiple comparison applied to the beer sensory results obtained by CATA over 12 weeks of forced aging comparing 5 different time points and excluding attributes not exhibiting significant differences between samples or time points according to Cochran’s Q test (p ≤ 0.05).

Comparison of forced aging time points	Flavor attributes exhibiting significant differences between different time points of forced aging or between the beer samples according to Cochran’s Q test (p ≤ 0.05)
	caramel	cardboard	citrus	dried fruit	resinous	spicy	sweaty	sweet aromatic	honey
t = 0 vs t = 12w	*	*	ns	*	ns	*	ns	*	*
t = 0 vs t = 2w	*	*	ns	*	ns	*	ns	ns	*
t = 0 vs t = 4w	ns	*	ns	*	ns	ns	ns	ns	ns
t = 0 vs t = 8w	ns	ns	ns	*	ns	ns	ns	ns	ns
t = 4w vs t = 12w	*	*	ns	*	ns	ns	ns	*	*
t = 4w vs t = 2w	*	*	ns	ns	ns	ns	ns	ns	*
t = 4w vs t = 8w	ns	ns	ns	ns	ns	ns	ns	ns	ns
t = 8w vs t = 12w	*	*	ns	*	ns	ns	ns	ns	*
t = 8w vs t = 2w	*	ns	ns	ns	ns	ns	ns	ns	*
t = 2w vs t = 12w	ns	*	ns	*	ns	ns	ns	ns	ns

*Significant differences according to ANOVA (p = 0.05), ns = no significant differences.

Table 7. ANOVA and Fisher multiple comparison applied to the beer sensory results obtained by CATA over 12 weeks of forced aging comparing 6 different hop dosages and excluding attributes not exhibiting significant differences between samples or time points according to Cochran’s Q test (p ≤ 0.05).

Comparison of beer samples over all time points	Flavor attributes exhibiting significant differences between different time points of forced aging or between the beer samples according to Cochran’s Q test (p ≤ 0.05)
	caramel	cardboard	citrus	dried fruit	resinous	spicy	sweaty	sweet aromatic	honey
ex0.5 vs ctrl	ns	ns	*	ns	*	ns	ns	*	*
ex0.5 vs pe2.9	ns	ns	*	ns	*	ns	ns	*	*
ex0.5 vs ex2.0	ns	ns	*	ns	*	ns	ns	ns	ns
ex0.5 vs pe5.8	ns	ns	*	ns	*	ns	ns	ns	ns
ex0.5 vs ex1.0	ns	ns	ns	ns	*	ns	ns	ns	ns
ex1.0 vs ctrl	ns	ns	*	ns	*	ns	ns	*	*
ex1.0 vs pe2.9	ns	ns	ns	ns	*	ns	ns	ns	ns
ex1.0 vs ex2.0	ns	ns	ns	ns	*	ns	ns	ns	ns
ex1.0 vs pe5.8	ns	ns	ns	ns	*	ns	ns	ns	ns
pe5.8 vs ctrl	ns	ns	ns	ns	*	ns	ns	*	ns
pe5.8 vs pe2.9	ns	ns	ns	ns	ns	ns	ns	ns	ns
pe5.8 vs ex2.0	ns	ns	ns	ns	ns	ns	ns	ns	ns
ex2.0 vs ctrl	ns	ns	ns	ns	*	ns	ns	ns	ns
ex2.0 vs pe2.9	ns	ns	ns	ns	ns	ns	ns	ns	ns
pe2.9 vs ctrl	ns	ns	ns	ns	*	ns	ns	ns	ns

*Significant differences according to ANOVA (p = 0.05), ns = no significant differences.