ORIGINAL PAPER

Study of the suitability of two hop cultivars for makingherb liqueurs: volatile composition, sensory analysis,and consumer study

Laura Vazquez-Araujo Raquel Rodrguez-Solana

Sandra M. Cortes-Dieguez Jose M. Domnguez

Received: 5 April 2013 / Revised: 15 May 2013 / Accepted: 15 June 2013 / Published online: 4 July 2013

Springer-Verlag Berlin Heidelberg 2013

Abstract The suitability of two different cultivars of hop

for making herb liqueurs was evaluated in the present study.

Grape distillate marc was used to macerate the hop

(15 g L-1), and headspace-solid phase microextraction was

conducted to determine which volatile compounds migrated

from the hop flowers to the liqueur. Also, a descriptive

sensory analysis and a consumer study were conducted,

with 7 herb liqueurs which had different percentages of hop

liqueurs, to determine the acceptability of the product and

the liking drivers. Saaz cultivar proved to be a good option

to improve or develop herb liqueurs, because the samples

which had a 10 and 25 % of Saaz liqueur were the most

liked for consumers. Samples which had Nugget liqueur

resulted too bitter and with an excess of herb flavor for

consumers, maybe because of the high concentration of

phenolic compounds or the presence of high amounts of

certain aromatic compounds (e.g., myrcene, humulene).

Saaz hop increased the intensity of aromatic herbs flavor

and decreased the perception of excess of sweetness of the

commercial liqueur. The addition of this cultivar could

contribute with new aromatic notes to a product, bringing to

the liqueur unique characteristics.

Keywords Humulus lupulus L. Nugget Saaz Sensoryanalysis Phenolic compounds HS-SPME

Introduction

Herb spirits have been made and consumed for centuries in

different European countries. These liqueurs are generally

made by macerating different aromatic herbs in fermented

grape marc distillate, distilling the fermented grape marc in

the presence of herbs, adding herbal extracts to the distilled

alcohol, or combining some of these methodologies. Dif-

ferent types and brands can be found across Europe, for

example, Italians Galliano and Strega, German Krauterli-

kor, French Chartreuse, and Spanish Orujo de Hierbas.

In Galicia (Spain), in 2004, the herb liqueurs were

included in the list of the products covered by the Geo-

graphical Designation of the Spirits and Traditional

Liqueurs from Galicia [1]. The regulation which defines

the characteristics of the Traditional Liqueurs from Galicia

includes some physico-chemical and sensory requirements,

highlighting that (1) the liqueur has to be made with at least

3 different aromatic herbs, (2) the liqueur must have

between 20 and 40 % alcohol by volume (abv), and (3) the

liqueur needs to meet certain sensory characteristics:

translucent and clean appearance, color between straw

yellow to greenish yellow; intense, fine, delicate, tasty, and

ample aroma, with floral and balsamic notes, and also

reminding the original grape marc spirit which completes

the herb notes which are characteristic of the product; it

should have absence of musty, burnt, acetic, and dirty

notes [2]. Therefore, to commercialize the herb liqueurs

with the Traditional Liqueur from Galicia label, the

product has to be evaluated by the official tasting panel of

the regulating council.

L. Vazquez-Araujo (&) R. Rodrguez-Solana S. M. Cortes-Dieguez J. M. DomnguezChemical Engineering Department, Faculty of Sciences,

University of Vigo, Campus Ourense, As Lagoas s/n,

32004 Ourense, Spain

e-mail: lvazquezara@uvigo.es

L. Vazquez-Araujo R. Rodrguez-Solana S. M. Cortes-Dieguez J. M. DomnguezLaboratory of Agro-food Biotechnology, CITI-University

of Vigo, Tecnopole-Tecnological Park of Galicia,

San Cibrao das Vinas, Ourense, Spain

123

Eur Food Res Technol (2013) 237:775786

DOI 10.1007/s00217-013-2050-6

Prior to 2012, only some herbs/spices have been

authorized to make the liqueurs: mint, chamomile, lemon

verbena, rosemary, oregano, thyme, coriander, orange

blossom, fennel, licorice, nutmeg, and cinnamon. However,

from 2012, new regulations authorized the use of any kind

of herb which is suitable for human consumption [2].

The aims of the present study are to investigate whether

hop is suitable for making herb liqueurs and to determine

whether the aromatic notes which this ingredient can bring

to the final product are liked or disliked by consumers. Hop

cones, the immature inflorescences of the female plant of

Humulus lupulus L., are widely used to enhance the flavor

and bitterness of beer. With only a small amount of this

ingredient, different aromatic notes could be added to the

liqueur: green and grassy notes which come from different

aldehydes (e.g., hexanal); citrus, floral, and fruity aromas

originated from esters and compounds such as nerol or

linalool; or even typical herbal notes from oxidized ses-

quiterpenes [3].

There are a small number of studies which determine the

volatile composition of aromatic herbs, including hop [46]

and grape marc spirits [7], but no research can be found in

the current literature which details the volatile composition

of herb liqueurs. Some authors have reported different key

odorants of beer which come from hop: linalool (floral),

myrcene (geranium), geraniol (floral), ethyl 2-methylbut-

anoate (citrus, apple-like), ethyl 3-methylbutanoate (citrus,

sweet), and ethyl 2-methylpropanoate (citrus, pineapple)

[8, 9].

It would be interesting to determine whether these vol-

atile compounds can be found in the herb liqueur made

with hop, and also to study whether they have the same

importance. Headspace-solid phase microextraction

(HS-SPME) has been successfully employed in previous

researches to determine the volatile composition of hop

[6, 10] and also raw spirits [11, 12]; therefore, this tech-

nique was chosen for the present study.

Materials and methods

Hop Samples

Hop samples were kindly provided by the company Hijos

de Rivera Inversiones Corporativas S.L (Gambrinus 2-10,

Pol. Ind. Grela. A Coruna, Spain). The samples were the

immature inflorescences of the female plant of Humulus

lupulus L., recently harvested and dried. Two hop cultivars,

which were grown in the same area (A Coruna, Galicia,

NW Spain), were chosen for the study: Nugget and Saaz.

Korfta et al. [13] studied different quality parameters

of some hop varieties, and reported a classification of

cultivars into four groups: fine aroma, aroma, bittering

dual-purpose (aroma and bitterness), and high-alpha hops

(bittering). Saaz can be classified as a fine aroma or

aroma cultivar, and Nugget is an example of high

alpha hop cultivar, although Nugget was reported as

having high concentration of volatile compounds as well

[6].

Herb liqueurs preparation

Twenty-five liters of grape marc distillate (65.5 % abv)

was provided by the company Hijos de Rivera Inversiones

Corporativas S.L., which also gave a similar amount of

commercial herb liqueur (made with the same grape marc

distillate). For the maceration of hop, 15 g of each culti-

var, and also a combination of both cultivars (7.5 g

Saaz ? 7.5 g Nugget), was added per liter of grape marc

distillate (obtaining Nugget liqueur, Saaz liqueur,

and N ? S liqueur). A total of 5 L of each hop liqueur

was macerated during 3 weeks at approximately 21 C,using 3 different jars for liqueur (3 replications), and

avoiding leaving too much headspace in the jars. After

these 3 weeks of maceration, the liqueurs were filtered

(Whatman n81 filter, cellulose, 11 lm) and kept at 4 Cduring 24 h for stabilization. After this time, the liqueurs

were adjusted to 30 % abv and approximately 200 g

sucrose L-1 by adding sucrose and distillate water,

obtaining products with the same characteristics of the

commercial liqueur.

Once the hop liqueurs were made, total phenolic content

(TPC) and headspace-solid phase microextraction were

conducted to characterize all samples (commercial and hop

liqueurs). Then, mixtures of the hop liqueurs with the

commercial sample were prepared to conduct the sensory

analyses.

Total phenolic content

Total phenolic content was measured as indicator of the

antioxidant activity in the liqueurs. TPC was determined by

using the FolinCiocalteu method reported by Vazquez-

Araujo et al. [14], which was based on the one reported by

Skinkard and Singleton [15], with some modifications.

Results were expressed as mg of gallic acid equivalents per

L of liqueur. Experiments were run in triplicate.

Volatile composition of the hop samples

and the liqueurs

Solid phase microextraction

Headspace of the hop cultivar samples, and also of the

different liqueurs, was studied using the semi-quantitative

technique solid phase microextraction (SPME).

776 Eur Food Res Technol (2013) 237:775786

123

The flowers were milled before its study, for 20 s in a

coffee grinder (Moulinex, Groupe SEB, Mexico) guar-

anteeing similar particle size for both samples. A quarter

gram of each sample was placed in a 10 mL vial with a

polypropylene hole cap PTFE/silicone septa. Vials were

equilibrated for 10 min at 40 C in a water bath. After thisequilibration time, a 50/30 lm DVB/CAR/PDMS fiber wasexposed to the sample headspace for 15 min at 40 C.Goncalves et al. [16] reported that the fiber DVB/CAR/

PDMS presented the best extraction efficiency when

studying terpenoid metabolites in hop essential oil, and also

that the addition of salt or agitation of the sample led to a

decrease in the chromatographic peak areas, for that rea-

son, no salt was added and the sample was not stirred. After

sampling, the desorption of analytes from the fiber coating

was made in the injection port of the GC at 250 C, during2 min, in splitless mode. Experiments were run in triplicate

for each cultivar sample.

The herb liqueurs volatile composition was studied

adapting the methodology reported by Plutowska and

Wardencki [11, 12]. Exactly 3.7 mL of liqueur with

1.30 mL of distillate water and 0.5 g NaCl was placed in a

10 mL vial with a polypropylene hole cap PTFE/silicone

septa. Vials were equilibrated for 10 min at 45 C in awater bath and agitated using a magnetic stirrer (600 rpm).

After this equilibration time, a 50/30 lm DVB/CAR/PDMS fiber was exposed to the sample headspace for

40 min, at 45 C, and constantly stirred at 600 rpm. Aftersampling, the desorption of analytes from the fiber coating

was made in the injection port of the GC at 250 C, during2 min, in splitless mode. Experiments were run in triplicate

for each liqueur (commercial, Nugget, Saaz, and N ? S).

Chromatographic analyses

A gas chromatograph (Agilent GC 7820A; Agilent tech-

nologies, Santa Clara, CA, USA), coupled with an Agilent

mass spectrometer detector (5975 Series MSD), was used

to isolate and identify the volatile compounds. The GCMS

system was equipped with a HP-5MS column (30 m 9

0.25 mm 9 0.25 lm film thickness). The temperature ofthe column began at 50 C and held for 1 min, increased1 C per minute to 90 C and then 2 C per minute to140 C. Then, temperature was increased 40 C per minuteto 250 C and held at this temperature during 1.25 min.The constant column flow was 1.2 ml min-1, using

hydrogen as the carrier gas, and the injection port was at

250 C.Most compounds were identified using two different

analytical methods: (1) Kovats indexes and (2) mass

spectra (authentic chemicals and Wiley spectral library

collection). Also, standards of limonene, b-myrcene,a-humulene, ocimene, b-caryophyllene, caryophyllene

oxide, and methyl nonanoate (Sigma-Aldrich Co., St.

Louis, MO) were used to ensure the identification of some

compounds. Identification was considered tentative when

based entirely on mass spectral data.

Sensory analyses

Sensory evaluation with trained panel

Seven highly trained panelists from the Regulating Council

of the Geographical Designation of the Spirits and Tradi-

tional Liqueurs from Galicia participated in this study,

testing the same samples which were evaluated for con-

sumers. Because the traditional herb liqueurs are made with

a combination of at least 3 different herbs, the consumer

study was conducted with the following 7 samples (coded

as indicated):

Sample A: commercial sample (which already have acombination of at least 3 aromatic herbs)

Sample B: mixture of 90 % commercial ? 10 % Saazliqueur samples

Sample C: mixture of 75 % commercial ? 25 % Saazliqueur samples

Sample D: mixture of 90 % commercial ? 10 %Nugget liqueur samples

Sample E: mixture of 75 % commercial ? 25 % Nug-get liqueur samples

Sample F: mixture of 90 % commercial ? 10 %(N ? S) liqueur samples

Sample G: mixture of 75 % commercial ? 25 %(N ? S) liqueur samples

Each panelist had more than 80 h of training in sensory

testing and more than 300 h of testing experience with

grape marc distillates, and herbs and coffee liqueurs. All

samples were poured into the official tasting glass for

evaluation. Each panelist received *15 mL of eachproduct for evaluation. The samples were served at 4 C.Table 1 shows the terms and definitions used for the

evaluation, terms which corresponded to the lexicon

developed by the panel to evaluate herb liqueurs for the

Regulating Council. A numerical scale from 0 (represent-

ing none) to 9 (representing extremely strong) was

used in this study. The testing room was at 21 1 C and55 5 % of RH, and the illumination was a combination

of natural and nonnatural (fluorescent) light.

Consumer study

A group of 153 consumers, aged 1875, were recruited in

two different areas of Spain (NW and SE) to conduct the

study (77 and 76 consumers, respectively). The north-

western area of Spain is well recognized by having an

Eur Food Res Technol (2013) 237:775786 777

123

important tradition in making and consuming grape marc

distillate and its derivatives: herbs and coffee liqueurs. The

southwestern area of Spain was chosen to give a compar-

ison with an area which does not have such a traditional

links with herb liqueurs. The gender ratio was approxi-

mately 45 % females and 55 % males. Ages were distrib-

uted, and all of them were represented in both areas of the

country.

Consumers were recruited from the local areas and were

asked to attend to just one session. Both consumer studies

were carried out in the testing rooms of two universities:

University of Vigo (Ourense, NW Spain) and Miguel

Hernandez University (Escuela Politecnica Superior de

Orihuela, Orihuela, SE Spain); they needed to be willing to

try herb liqueurs and consume distillates or liqueurs at least

34 times/month. Each consumer tested all seven samples

Table 1 Attributes and definitions used by the trained panel

Definition

Flavor

Sweet The fundamental taste factor associated with a sucrose solution

Sour The fundamental taste factor associated with a citric acid solution

Salty The fundamental taste factor of which sodium chloride is typical

Bitter The fundamental taste factor associated with a caffeine solution

Aromatic herbs The aromatics associated with commonly known aromatic herbs such as fennel, mint, and coriander

Mint The aromatics associated with mint

Chamomile The aromatics associated with chamomile

Lemon verbena The aromatics associated with lemon verbena

Rosemary The aromatics associated with rosemary

Oregano The aromatics associated with oregano

Fennel The aromatics associated with fennel

Coriander The aromatics associated with coriander

Thyme The aromatics associated with thyme

Floral Sweet and perfume-like impression associated with flowers such as orange blossom, roses, or hyacinth

Fruity (not citrus) The aromatics associated with pome and stone fruits, such as apple and pear

Fruity (citrus) The aromatics associated with commonly known citrus fruits, such as lemons, limes, or oranges

Spicy The aromatics associated with spices such as cinnamon, nutmeg or licorice

Balsamic The aromatics associated with eucalypt, causing a refreshing sensation in the mouth

Honey-like The aromatics typical of honeys and molasses

Grape marc The aromatics typical of the distillate grape marc used to macerate the herbs

Herbaceous The aromatics caused by the presence of hexanals generated during the marcs storage

Alcoholic Ethanol aroma

Cellulose The aromatics which reminds paper or cardboards

Sulfur compounds The aromatics associated with cooked or spoiled eggs

Mouthfeels

Astringent The dry puckering mouthfeel due to the presence of certain substances such as tannins

or polyphenols in the mouth

Pungent Bitting tactile sensation due to the presence of certain compounds such as ethanol and black pepper

Drying Dry sensation in the mouth due to the presence of ethanol

Alcoholic sensation Ethanolic sensation in the mouth. It could be warm if the sensation is low, to burning

if it is a high sensation

Greasiness Coating sensation in the mouth

Global assessment

Balanced If the product does not have any aromatic note with highlights over the set, it receives a high score

in balance; otherwise, it would receive a low score in the scale

Structured Term used to discern the weight of the liquid and how it feels in the mouth. Light means a low

score in structure; full body means a high score in structure

778 Eur Food Res Technol (2013) 237:775786

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in a single session, carried out in a temperature controlled

room (21 1 C) with a combination of natural andnonnatural (fluorescent) light. The presentation order was

randomized using a modified Williams Latin square

design s. Approximately 8 mL of each sample were served

at 4 C in 100 ml disposable plastic cups, waiting all timerequested by the consumer between samples. Consumers

were instructed to give a sip and answer the questions.

More sample was available for them if requested. Also,

consumers were asked to eat unsalted crackers and drink

deionized water at room temperature for palate cleansing

in-between samples.

The consumers were asked to evaluate the overall liking

of the samples on a 9-point hedonic scale (1 = dislike

extremely to 9 = like extremely) and similar hedonic

scales for some attributes: sweetness, bitterness, and aro-

matic herb flavor. Just-about-right (JAR) questions about

the aforementioned attributes were done as well, using a

9-point scale where 5 corresponded to the JAR score. A

parallel questionnaire about demographic information was

also asked to determine possible relationships or differ-

ences among demographic groups.

Data analyses

All data were subjected to statistical analysis using SPSS

(version 19.0; SPSS Inc., Chicago, Ill.), used for analysis of

variance (ANOVA) and Tukeys honestly significant dif-

ferences (HSD) for post hoc mean separation. Also, inter-

nal preference maps and partial least square regression

(PLS regression map, with the intent of relating consumer

results with descriptive data) were conducted using the

Unscrambler version 9.7 (Camo Software, Oslo, Norway).

Results and discussion

Differences between hop cultivars

Table 2 shows the main differences in the volatile com-

position of the headspace of Nugget and Saaz hop cultivars.

Both cultivars were characterized by having high propor-

tions of terpenes (more than 50 % of the total area of

volatiles was composed by terpenes) and sesquiterpenes

(more than 35 %). Main differences were found in the

esters fraction of both samples, highlighting that Nugget

cultivar had a higher amount of esters: 12.2 % of the total

area of volatiles in Nugget and only 6.38 % in Saaz.

Vazquez-Araujo et al. [6] reported similar results when

studying hop pellet samples, in which Nugget cultivar had

approximately double the content of ester compounds than

Saaz. Proportions of other groups of compounds are not in

agreement with the ones reported previously by these

authors, maybe because the present study was conducted

with hop flowers and Vazquez-Araujo et al. [6] studied hop

pellets. As reported by Krofta [13], and then confirmed by

Vazquez-Araujo et al. [6], results of the present study

showed that there were substantial differences between the

terpenic fraction of these hop cultivars: Saaz (fine aroma

variety) had significant amounts of (Z,Z)-a-farnesene, (E)-b-farnesene (apple, lavender, etc.), b-bisabolene (floral,freesia, etc.), and (E,E)-a-farnesene [17], volatile com-pounds not present in the Nugget sample (bitter variety).

Differences among liqueurs

Regarding the liqueurs, Table 3 shows the differences

among the TPC in the liqueurs used to elaborate the final

herb liqueurs with hop. As shown in the table, all samples

were significantly different (p \ 0.05), being the com-mercial liqueur the one which had the lowest TPC (ca

205 mg gallic acid equivalents L-1). Nugget cultivar

brought the highest amount of phenolic compounds to the

grape distilled marc (ca 332 mg gallic acid equivalents

L-1). Therefore, it is expected that using hop as an ingre-

dient to make herb liqueurs will slightly increase the TPC

and also the antioxidant activity of the end product. Roby

et al. [18] reported that methanol and ethanol were the best

extracting solvents for phenolics in plants such as thyme,

sage, and marjoram. Because of the high amount of ethanol

in the grape distillate marc used to macerate the herbs,

most phenolic compounds migrated from the plant to the

liqueur, providing a high antioxidant activity to the

product.

When looking at the aromatic profile of the liqueurs

made with Nugget or Saaz hop cultivars, significant dif-

ferences were found if when compared with the aromatic

profiles of the flowers (Tables 4, 2). After the maceration

process, Saaz liqueur was characterized by its high pro-

portion of esters (62 %), but Nugget liqueur was charac-

terized by having a high proportion of terpenes (ca 32 %)

and sesquiterpenes (ca 49 %). Vazquez-Araujo et al. [6]

reported that the volatile profile of hop obtained using HS-

SPME or hydrodistillation was different if looking at the

behavior of some chemical groups. Because esters were

pretty instable compounds, a great variation was observed

within the chemical group, and no pattern was observed

when comparing both extraction techniques. Something

similar might be happening in the present study, because

the maceration could be considered a solidliquid extrac-

tion technique. Also, not all hop cultivars have same

amount of essential oil (varying from 0.5 to 2 %), so the

amount of volatile compounds extracted by the ethanol

during the maceration of the hop flowers might vary. If

looking at the total areas accounts of the chromatograms

obtained using GCMS, Saaz cultivar had a significant

Eur Food Res Technol (2013) 237:775786 779

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Table 2 Volatile compounds of the hop flowers (area %)

Compound KIa (NIST) KI (Exp) Nugget Saaz

Esters

1 2-Methyl-, 3-methylbutyl propanoate 1017 1016 1.57 0.19 n.d.

2 2-Methyl-, 2-methylbutyl propanoate 1014 1019 1.86 0.20 n.d.

3 Methyl heptanoate 1026 1025 1.49 0.15 1.58 0.41

4 2-Methyl-, 2-methylbutyl butanoate 1110 1103 0.20 0.03 n.d.

5 3-Methyl-, 2-methylbutyl butanoate 1110 1107 0.40 0.04 n.d.

6 Methyl octanoate 1125 1124 2.68 0.14 1.97 0.06

7 2-Methyl-, hexyl propanoate 1149 1146 0.11 0.01 n.d.

8 Methyl benzeneacetate 1180 1171 0.03 0.01 0.02 0.01

9 Ethyl octanoate 1195 1205 0.04 0.01 n.d.

10 Methyl n-nonenoate 1210 0.14 0.01 0.08 0.01

11 Methyl nonanoate 1225 1224 0.76 0.03 0.64 0.02

12 Methyl n-nonenoate 1227 0.03 0.01 n.d.

13 2-Methyl-, heptyl propanoate 1248 1246 0.05 0.01 n.d.

14 Isopentyl hexanoate 1254 1251 n.d. 0.01 0.01

15 Methyl n-decanoate 1309 1.85 0.11 1.57 0.07

16 Methyl geranate 1331 1322 0.16 0.03 0.11 0.01

17 Methyl decanoate 1326 1327 0.85 0.03 0.40 0.04

12.2 6.38

Terpenes

1 Myrcene 991 998 44.3 2.0 55.0 0.3

2 p-Cymene 1028 1021 0.16 0.04 n.d.

3 Limonene 1034 1024 2.07 0.06 0.80 0.08

4 (E)-b-Ocimene 1044 1034 0.38 0.01 0.18 0.04

5 (Z)-b-Ocimene 1049 1044 3.51 0.07 0.74 0.19

6 c-Terpinene 1064 1050 0.10 0.01 0.13 0.01

7 Allo-ocimene 1130 1134 0.37 0.02 0.14 0.05

50.9 57.0

Terpenoids

1 Linalool 1107 1099 1.32 0.11 0.50 0.01

Sesquiterpenes

1 a-Cubebene 1345 1338 0.16 0.03 0.10 0.01

2 Sativene 1394 1349 0.05 0.01 0.02 0.01

3 a-Ylangene 1370 1357 0.20 0.01 0.14 0.01

4 a-Copaene 1377 1362 0.58 0.03 0.45 0.01

5 (Z)-b-Caryophyllene 1405 1390 0.56 0.12 0.10 0.03

6 (E)-b-Caryophyllene 1418 1403 12.8 0.5 6.97 0.15

7 b-Copaene 1422 1411 1.04 0.15 0.42 0.08

8 (Z,Z)-a-Farnesene 1462 1430 n.d. 1.03 0.10

9 Humulene 1457 1441 16.9 0.6 16.2 0.2

10 Caparratriene 1493 1446 n.d. 0.42 0.19

11 (E)-b-Famesene 1461 1460 n.d. 8.63 0.94

12 b-Selinene 1490 1469 0.87 0.02 0.17 0.01

13 a-Selinene 1498 1478 0.86 0.02 0.14 0.01

14 ()-Cadinene 1523 1486 0.12 0.01 0.08 0.01

15 a-Muurolene 1483 1488 0.13 0.01 0.11 0.01

16 c-Cadinene 1504 1498 0.36 0.01 0.36 0.01

17 b-Bisabolene 1516 1500 n.d. 0.07 0.01

780 Eur Food Res Technol (2013) 237:775786

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lower area counts than Nugget, which seemed to show that

Nugget cultivar brought a higher amount of volatile com-

pounds to the liqueur.

Nance and Setzer [19] reported that, in general, hop oils

rich in monoterpenoids are fruity or citrusy, while those

dominated by sesquiterpenes tend toward earthy, herbal,

woody, or spicy aromas. Nugget and Saaz liqueurs were

similar if looking at the proportion terpenes: sesquiter-

penes, but qualitative differences were found related to the

compounds which were present in one or another sample,

e.g., presence of c-terpinene and allo-ocimene in Nuggetand not in Saaz liqueur, or presence of (E)-b-farnesene andb-bisabolene in Saaz and not in Nugget liqueur. All thosedifferences could be translated into sensory differences of

the liqueurs.

Commercial liqueur was characterized by having a high

proportion of esters (e.g., ethyl octanoate and ethyl de-

canoate), mainly coming from the grape distillate marc

used as raw material [7]. Also, highlighted the presence of

phenyl derivatives such as E-anethole and p-propylanisole,

compounds typically found in fennel [20, 21]. The pres-

ence of certain terpenoids such as isomenthol, levomen-

thol, or eucalyptol suggested the presence of mint as other

ingredient of the commercial liqueur [22].

Sensory analyses results

Figure 1 shows the flavor profiles of 3 of the 7 samples: A

(commercial), C (?25 % Saaz liqueur), and D (?25 %

Nugget liqueur). These samples exhibited the most sensory

significant differences and as such are the only ones rep-

resented in the spider plot. All other samples received

sensory scores between one of the samples showed in the

graph (the % of hop liqueur addition to the commercial

sample was lower). Significant differences (p \ 0.05) werefound for these 3 samples in sweet, bitter, mint, chamo-

mile, lemon verbena, balsamic, herbal, and alcoholic flavor

notes, and also in the astringency and pungency mouthfe-

els. Results seemed to indicate that Nugget hop brought

some negative notes to the product: higher bitterness,

astringency, pungency, herbaceous aromas, and alcoholic

sensation. According to the literature, at least in some

juices, a high content on phenolic compounds is related to

sensory parameters such as astringency and bitterness [23].

Therefore, it was expected that liqueur with a high con-

centration of Nugget hop liqueur had higher intensities of

these attributes (Table 3). Also, although no significant

differences were found (p C 0.05) among samples,

liqueurs with a higher amount of Nugget hop liqueur

received higher scores in the fruity-citrus notes, maybe due

to its high content of terpenes [19]. Commercial liqueur

was characterized by having chamomile, lemon verbena,

and aromatic herbs notes, as well as a higher sweetness

than all other samples (although the sugar content was the

same in all samples).

Results of the consumer study showed no significant

differences (p C 0.05) between consumers from both areas

of the country or between genders, so data were treated as a

unique group. Two groups of samples were observed when

analyzing the results of the overall liking of the products:

samples A, B, C, and F (with scores close to 6 in a 9 points

Table 3 Total phenolic content of the liqueurs

Liqueur Total phenolic content (mg

Gallic acid equivalents L-1)

Commercial 205 9d

Saaz 246 7c

Nugget 332 24a

Nugget ? Saaz 288 6b

Data mean of 3 replications. Values followed by the different letter,

within the same variation source, were significantly different

(p \ 0.05). Tukeys honestly significant differences (HSD)

Table 2 continued

Compound KIa (NIST) KI (Exp) Nugget Saaz

18 (E,E)-a-Farnesene 1508 1504 n.d. 0.14 0.01

19 (E)-Calamenene 1505 1506 0.08 0.01 n.d.

20 (Z)-Calamenene 1520 1508 0.10 0.02 0.10 0.01

21 d-Cadinene 1525 1511 0.61 0.03 0.55 0.01

22 a-Calacorene 1542 1527 0.03 0.01 n.d.

35.5 36.1

Sesquiterpenoids

1 Caryophyllene oxide 1582 1590 0.01 0.01 0.03 0.01

n.d., not detected; n.a., not available for HP5-MS or equivalent column. Retention indexes reported for the HP-5MS or equivalent column. Data

mean of 3 replicationsa NIST [24]

Eur Food Res Technol (2013) 237:775786 781

123

Table 4 Volatile compounds of the commercial sample and the hop liqueurs (area %)

Compound KIa (NIST) KI (Exp.) Commercial Nugget Saaz Nugget ? Saaz

Esters

1 Ethyl hexanoate 996 1002 2.36 0.51 n.d. 3.65 0.20 n.d.

2 2-Methyl-, 3-methylbutyl propanoate 1017 1013 n.d. 0.36 0.02 n.d. 0.25 0.02

3 2-Methyl-, 3-methylbutyl propanoate 1014 1015 n.d. 0.80 0.06 n.d. 0.53 0.01

4 Methyl heptanoate 1026 1022 n.d. 0.62 0.03 0.34 0.02 0.52 0.03

5 Ethyl heptanoate 1097 1099 n.d. 0.08 0.01 0.08 0.01 0.10 0.01

6 2-Methyl-, 2-methylbutyl butanoate 1110 1103 n.d. 0.07 0.01 n.d. n.d.

7 3-Methyl-, 2-methylbutyl butanoate 1110 1107 n.d. 0.16 0.01 n.d. 0.14 0.01

8 Methyl octanoate 1125 1123 0.14 0.02 0.97 0.03 0.60 0.03 0.86 0.02

9 2-Methyl-, hexyl propanoate 1149 1146 n.d. 0.05 0.01 n.d. 0.03 0.01

10 Ethyl octanoate 1195 1205 30.1 0.9 10.5 0.2 24.9 1.0 16.5 0.1

11 Methyl n-nonenoate 1212 n.d. 0.07 0.01 0.04 0.01 0.06 0.01

12 Methyl nonanoate 1225 1224 n.d. 0.42 0.04 0.31 0.01 0.42 0.01

13 2-Methyl-, heptyl propanoate 1248 1246 n.d. 0.04 0.01 n.d. 0.03 0.01

14 Isopentyl hexanoate 1254 1248 0.08 0.01 0.04 0.01 0.12 0.01 0.07 0.01

15 Ethyl n-nonenoate 1285 n.d. n.d. 0.02 0.01 n.d.

16 Menthol, acetate 1294 1288 0.73 0.03 n.d. n.d. n.d.

17 Ethyl nonanoate 1294 1298 0.21 0.01 0.15 0.01 0.44 0.01 0.25 0.01

18 Methyl n-decanoate 1310 n.d. 1.33 0.09 0.80 0.08 1.29 0.05

19 Methyl geranate 1331 1323 n.d. 0.14 0.01 0.12 0.02 0.14 0.01

20 Methyl decanoate 1326 1327 0.16 0.01 0.80 0.06 0.81 0.06 0.87 0.03

21 2-Butyl octanoate n.a. 1351 0.03 0.01 n.d. 0.07 0.01 0.05 0.01

22 Ethyl decanoate 1394 1409 26.7 0.8 1.58 0.03 26.3 1.8 9.52 1.10

23 3-Methylbutyl octanoate 1446 1451 0.27 0.02 0.12 0.01 0.34 0.02 0.20 0.01

24 2-Methylbutyl octanoate 1449 1452 0.08 0.01 n.d. n.d. n.d.

25 Isobutyl n-caproate 1545 1548 0.03 0.01 n.d. n.d. n.d.

26 Ethyl dodecanoate 1576 1600 4.48 0.42 0.91 0.10 3.12 0.54 1.56 0.12

27 3-Methylbutyl pentadecanoate 1644 1650 0.09 0.01 n.d. n.d. n.d.

28 Ethyl tetradecanoate 1793 1797 0.16 0.02 n.d. n.d. n.d.

29 Ethyl hexadecanoate 1993 1970 0.06 0.01 n.d. n.d. n.d.

65.6 19.2 62.0 33.4

Phenyl derivatives

1 E-3-Caren-2-ol 1111 (DB1) 1019 0.44 0.19 n.d. n.d. n.d.

2 Estragole 1196 1189 0.47 0.02 n.d. n.d. n.d.

3 p-Propylanisole n.a. 1199 5.41 0.30 n.d. n.d. n.d.

4 (Z)-Anethole 1258 1243 1.04 0.09 n.d. n.d. n.d.

5 (E)-Anethole 1283 1275 21.9 1.9 0.09 0.03 0.07 0.01 0.05 0.01

6 Dihydrosafrole n.a. 1285 0.37 0.03 n.d. n.d. n.d.

29.7 0.09 0.07 0.05

Terpenes

1 b-Myrcene 991 1000 n.d. 29.9 0.4 13.9 0.7 25.5 0.7

2 p-Cymene 1028 1017 0.31 0.12 n.d. n.d. n.d.

3 Limonene 1034 1021 n.d. 0.31 0.04 0.16 0.01 0.17 0.01

4 (E)-b-Ocimene 1044 1033 n.d. 0.13 0.01 0.05 0.01 0.11 0.01

5 (Z)-b-Ocimene 1049 1042 n.d. 1.33 0.01 0.21 0.01 0.87 0.05

6 c-Terpinene 1064 1049 1.15 0.42 0.04 0.01 n.d. 0.04 0.01

7 Allo-ocimene 1130 1134 n.d. 0.12 0.01 n.d. 0.10 0.01

8 p-Menthone 1153 1141 0.77 0.03 n.d. n.d. n.d.

2.22 31.8 14.3 26.8

782 Eur Food Res Technol (2013) 237:775786

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Table 4 continued

Compound KIa (NIST) KI (Exp.) Commercial Nugget Saaz Nugget ? Saaz

Terpenoids

1 Eucalyptol 1038 1021 0.68 0.13 n.d. n.d. n.d.

2 Terpinolene 1090 1078 0.16 0.04 n.d. n.d. n.d.

3 Linalool 1102 1098 0.32 0.04 n.d. n.d. n.d.

4 Camphor 1138 1130 0.12 0.02 n.d. n.d. n.d.

5 Z-p-Menth-2-en-1-ol 1139 1151 0.18 0.01 n.d. n.d. n.d.

6 Citronellal 1150 1152 0.14 0.01 n.d. n.d. n.d.

7 Levomenthol 1172 1163 0.25 0.09 n.d. n.d. n.d.

8 Isomenthol 1179 1164 0.42 0.08 n.d. n.d. n.d.

9 Isopulegol 1148 1166 0.16 0.05 n.d. n.d. n.d.

2.42 n.d. n.d. n.d.

Sesquiterpenes

1 a-Cubebene 1345 1339 n.d. 0.11 0.01 0.03 0.01 0.05 0.01

2 Sativene 1394 1350 n.d. 0.07 0.01 n.d. 0.04 0.01

3 a-Ylangene 1370 1358 0.02 0.01 0.23 0.01 0.16 0.01 0.17 0.01

4 a-Copaene 1377 1362 n.d. 0.57 0.03 0.32 0.02 0.39 0.01

5 b-Bourbonene 1385 1368 0.03 0.01 n.d. n.d. n.d.

6 (Z)-b-Caryophyllene 1405 1391 n.d. 0.30 0.02 n.d. 0.22 0.01

7 (E)-b-Caryophyllene 1418 1404 n.d. 20.7 0.5 9.62 0.97 15.8 0.5

8 b-Copaene 1422 1416 n.d. 1.17 0.01 n.d. n.d.

9 a-Bergamotene 1434 1432 n.d. n.d. 0.41 0.03 n.d.

10 Humulene 1457 1445 n.d. 18.5 0.5 9.86 0.68 16.3 0.3

11 4,5-di-epi-Aristolochene 1467 (BP1) 1453 n.d. 0.10 0.01 n.d. 0.25 0.02

12 (E)-b-Famesene 1461 1459 n.d. n.d. 1.07 0.12 0.75 0.01

13 c-Muurolene 1477 1466 0.01 0.01 1.27 0.02 n.d. 1.23 0.04

14 b-Selinene 1490 1471 n.d. 1.51 0.01 0.22 0.02 1.02 0.04

15 Eremophilene 1489 1473 n.d. 0.13 0.01 n.d. 0.08 0.01

16 a-Curcumene 1486 1475 0.02 0.01 n.d. n.d. n.d.

17 Gurjunene 1475 1476 n.d. 0.06 0.01 n.d. 0.06 0.01

18 a-Selinene 1498 1480 n.d. 1.59 0.02 0.19 0.01 1.03 0.03

19 c-Gurjunene 1473 1485 0.01 0.01 n.d. n.d. n.d.

20 b-Guaiene 1487 1487 n.d. n.d. 0.03 0.01 0.08 0.01

21 a-Muurolene 1483 1489 0.01 0.01 0.24 0.01 0.17 0.01 0.19 0.01

22 c-Cadinene 1504 1499 n.d. 0.82 0.02 0.64 0.03 0.72 0.01

23 b-Bisabolene 1516 1500 n.d. n.d. 0.05 0.01 n.d.

24 (E)-Calamenene 1505 1506 0.03 0.01 n.d. 0.09 0.01 0.10 0.01

25 (Z)-Calamenene 1520 1509 n.d. 0.11 0.01 0.13 0.01 0.11 0.01

26 d-Cadinene 1525 1512 n.d. 1.05 0.02 0.37 0.02 0.78 0.01

27 Cadinadiene-1,4 1539 1518 n.d. 0.13 0.01 0.07 0.01 0.10 0.01

28 a-Cadinene 1536 1523 n.d. 0.17 0.01 0.11 0.01 0.13 0.01

29 a-Calacorene 1542 1527 n.d. 0.05 0.01 n.d. 0.06 0.01

0.12 48.9 23.5 39.7

Sesquiterpenoids

1 Caryophyllene oxide 1582 1590 n.d. n.d. 0.04 0.01 0.03 0.01

100 100 100 100

n.d., not detected; n.a., not available for HP5-MS or equivalent column. Retention indexes reported for the HP-5MS or equivalent column. Data mean of 3

replicationsa NIST [24]

Eur Food Res Technol (2013) 237:775786 783

123

scale) liked significantly more than samples D, G, and E

(with scores close to 4 in a 9 points scale) (p \ 0.05). Thesample which received the highest punctuation was sample

B (90 % commercial ? 10 % Saaz liqueur), and the sam-

ples which received the lowest scores were the samples

with higher concentration of Nugget hop. Figure 2

Fig. 1 Spider plot showing themain flavor parameters for 3 of

the herb liqueur samples (10

points scale 0 = none,

9 = extremely strong).

Significant differences were

found among these samples for

the flavors: sweet, bitter, mint,

chamomile, lemon verbena,

balsamic, herbal, and alcoholic

(p \ 0.05)

Fig. 2 Internal preference map showing overall liking for the herb liqueur samples. Samples: indicated in bold font. Filled circle NW-Spanishconsumers indicated with G; SE-Spanish consumers indicated with A

784 Eur Food Res Technol (2013) 237:775786

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illustrates the internal preference map showing the overall

liking of consumers.

Also, significant differences (p \ 0.05) were foundwhen looking at sweetness, bitterness, and aromatic herbs

flavor liking. Again, the samples which were more liked for

the three parameters were the ones with Saaz hop liqueur

and also the commercial sample. If studying the JAR

questions for these attributes, the samples in which a higher

frequency of consumers answered JAR or the closest score

(456 in the 9 points JAR scale), were C and B (between

66 and 76 % of consumers marked 4, 5 or 6 for all these

parameter in these samples). Results seemed to indicate

that the commercial sample had a slight excess of sweet-

ness that was not perceived in samples 706 and 153.

Regarding the JAR question about aromatic herb flavor,

76 % of respondents scored 46 in sample C (75 % com-

mercial ? 25 % Saaz liqueur); therefore, the addition of a

small percentage of Saaz hop improved the perception of

this specific attribute. As expected, sample E (75 % com-

mercial ? 25 % Nugget liqueur) was signaled as too

much flavor and too much bitterness for more than

50 % of consumers, and too slight sweetness for 34 % of

respondents.

Figure 3 shows a PLS map which illustrates the drivers

for consumers overall liking. As can be seeing in the map,

67 % of the total variation of the descriptive data explained

37 % of variation of overall liking. As shown in the figure,

consumers tend to like products which have higher inten-

sities in aromatic herbs, lemon verbena, chamomile, and

mint flavors. Also, they liked high sweetness but, as shown

previously (JAR questions results), not in excess. In gen-

eral, consumers liked structured and equilibrated products

which were perceived as unctuous as well. Results of the

present study showed that, contrary as expected, floral or

fruity flavors were not liking drivers, maybe because those

attributes were not associated with herb liqueurs but

with other kind of liqueurs such as limoncello (Italian

lemon liqueur) or similar fruit liqueurs.

Conclusions

Substantial differences were found when studying the suit-

ability of Nugget and Saaz hop cultivars to make herb

liqueurs. Commercial liqueur with Nugget liqueur added

had a higher bitterness, astringency, pungency, herbaceous

Fig. 3 Partial least square map showing overall liking drivers for NW and SE-Spanish consumers. Sensory parameters indicated by thedescriptors in bold and italic font. Filled circle NW-Spanish consumers indicated with G; SE-Spanish consumers indicated with A

Eur Food Res Technol (2013) 237:775786 785

123

notes, and also produced a higher alcoholic sensation

(p \ 0.05). Some of these attributes could be related to thehigher TPC of the Nugget liqueur sample, and also to the

fact that the volatile composition of both cultivars was pretty

different. In general, consumers did not like these herb

liqueurs made with Nugget hop. On the other hand, results

showed that the addition of fine aroma hops (Saaz) to make

herb liqueurs was appreciated by consumers, and maybe

liqueur companies should consider using this herb as a new

ingredient for their products. Adding Saaz hop increased the

liking of aromatic herbs flavor and also decreased the

perception of excess of sweetness for consumers. The

addition of this cultivar could bring new aromatic notes to a

product, giving to the liqueur unique characteristics. The

present study shows a useful example of how to evaluate the

suitability of an aromatic herb as ingredient to make a tra-

ditional product such as herb liqueur.

Acknowledgments Part of financial assistance for this project wasprovided by the Ministry of Research and Science of Spain thought

the Juan de la Cierva subprogram. Also, we are grateful for the

financial support of this work to Diputacion de Ourense and Uni-

versity of Vigo (INOU12-15). In addition, the authors wish to thank

Jose Luis Olmedo Nadal, the company Hijos de Rivera Inversiones

Corporativas S.L., and the panelists of the Regulating Council of the

Geographical Denomination of the Spirits and Traditional Liqueurs

from Galicia for their kind collaboration in this particular study.

Conflict of interest None.

Compliance with Ethics Requirements This article does notcontain any studies with human or animal subjects.

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Reproduced with permission of the copyright owner. Further reproduction prohibited withoutpermission.

c.217_2013_Article_2050.pdfStudy of the suitability of two hop cultivars for making herb liqueurs: volatile composition, sensory analysis, and consumer studyAbstractIntroductionMaterials and methodsHop SamplesHerb liqueurs preparationTotal phenolic contentVolatile composition of the hop samples and the liqueursSolid phase microextractionChromatographic analyses

Sensory analysesSensory evaluation with trained panelConsumer study

Data analyses

Results and discussionDifferences between hop cultivarsDifferences among liqueursSensory analyses results

ConclusionsAcknowledgmentsReferences