Changes in aroma profile of musts from grapes cv Pedro Ximenez chamber-dried at controlled conditions destined to the production of sweet Sherry wine

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LWT - Food Science and Technology 59 (2014) 560e565
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Changes in aroma profile of musts from grapes cv. Pedro Ximenez
chamber-dried at controlled conditions destined to the production of
sweet Sherry wine
Maria J. Ruiz, Lourdes Moyano, Luis Zea*
Department of Agricultural Chemistry, University of Cordoba, Campus de Rabanales, Edificio Marie Curie, 14014 Cordoba, Spain
a r t i c l e i n f o
Article history:
Received 4 July 2011
Received in revised form
23 April 2014
Accepted 25 April 2014
Available online 4 May 2014
Keywords:
Controlled-drying
Pedro Ximenez grapes
Aroma
Must
* Corresponding author. Fax: þ34 957212146.
E-mail address: qe1zecal@uco.es (L. Zea).
http://dx.doi.org/10.1016/j.lwt.2014.04.056
0023-6438/� 2014 Elsevier Ltd. All rights reserved.
a b s t r a c t
Changes in odorant compounds of musts from cv. Pedro Ximenez grapes chamber-dried at controlled
temperature of 40 �C and 50 �C were analyzed by GCeMS. The aroma profile of musts was studied by
grouping the compounds into 9 odorant terms according to their odor descriptors. The odor activity
values for the terms were calculated by adding those for the individual compounds grouped in each one
of them. The odorant terms caramelized and floral were the greatest contributors to the aroma profile of
the musts by effect of the presence of phenethyl alcohol and 3-methylbutanoic acid. The results showed
that the musts from grapes dried at 40 �C had a stronger raisiny aroma than the musts obtained at 50 �C.
Accordingly, chamber-drying grapes at a controlled temperature of 40 �C may provide raisins of sub-
stantially improved quality for the production of Pedro Ximenez sweet wines.
� 2014 Elsevier Ltd. All rights reserved.
1. Introduction
In recent years, consumers’ demand for sweet wines made from
cv Pedro Ximenez raisins in the MontillaeMoriles Designation of
Origin (southern Spain) has grown steadily and their production
been virtually sold out every season. The first and foremost step in
their production process involves sun-drying the grapes for 5e10
days depending on the particular weather conditions. This process
develops optimally at high temperatures and low ambient mois-
ture. Further information about the production of Pedro Ximenez
sweet wines can be found in Montedoro & Bertuccioli, 1986.
Sun-drying grapes essentially causes their dehydration and
leads to the obtainment of very dark and sugary musts with an
alcoholic potential usually twice higher than that of the freshly
harvested grapes (Chaves, Zea, Moyano, & Medina, 2007). The
grapes should be dried uniformly and to a moderate extent only;
otherwise, they may be extremely difficult to press or even grind.
To this end, grapes are spread on mats made of esparto or plastic
which are placed on sandy ground usually on a gentle slope
(commonly called “pasera”). Sun-drying grapes requires no costly
equipment, but has substantial labor costs owing to the need for
periodic turnover of the grapes in order to ensure uniform raisin-
ing, and this raises production costs.
In this way, an economic study was made to evaluate the cost of
the chamber drying in compare with sun-drying: Comparing two
loads of 10.000 kg of grapes the costs of the traditional drying and
the chamber drying are similar, including the building of the
chamber and the cost of light and heat station. However, it is
necessary to point out that the real world not only implements a
drying process under the sun on the same area of land, but at least
two sequentially, so when it finishes a drying process a certain
weight of grape, is collected and extends a new weight of fresh
grapes in the same place, doubling the weight of processed grape
and, consequently, the cost of labor. This practice is made also
sequentially in the chamber drying, even though in this case only
doubling energy expenditure, and not the human cost.
Also, the grapes are under a high risk of deterioration by effect of
insect attacks, potential rain and nocturnal dew. In addition, these
ambient conditions can favor the production of fungal toxins such
as Ochratoxin A, which have an adverse impact on the Pedro
Ximenez health safety.
The above-described problems have aroused interest in devel-
oping alternative grape-drying methods such as direct exposure to
the sun of grapes placed on trays or hung onwires to prevent direct
contact with the ground (Mahmutoglu, Emir, & Saygi, 1996; Yaldiz,
Ertekin, & Uzum, 2001), or mechanical drying, which is safe, rapid
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M.J. Ruiz et al. / LWT - Food Science and Technology 59 (2014) 560e565 561
and easily controlled but requires a high yield to be profitable.
These methods can be used jointly with sun-drying in order to
combine their individual advantages (Pangavhane, Sawhney, &
Sarsavadia, 2002). Also, microwave drying under vacuum has
been used to obtain “puffy dried grapes” in California. Chamber
drying at a controlled temperature and moisture provides a fast,
reliable and simplemethod but also requires high production yields
in order to absorb the high energy costs incurred. In any case, the
drying time is short, especially if some pretreatment is applied to
facilitate moisture removal, but requires optimizing the drying
conditions in order to ensure a high efficiency and obtainment of
the expected sensory profile for the resulting wine. Amore detailed
description on the grape hot-drying techniques are described
elsewhere (Esmaiili, Sotudeh-Gharebagh, Cronin, Mousavi, &
Rezazadeh, 2007; Karathanos & Belessiotis, 1996; Margaris &
Ghiaus, 2007; Pangavhane et al., 2002; Vazquez, Chenlo, Moreira, &
Cruz, 1997) Equipment allowing the strict control of drying condi-
tions (temperature, relative humidity and air velocity) has lately
beenmade available to expedite the grape drying process and avoid
contamination and the production of fungal Ochratoxin A. Tunnel
drying has been found to result in increased weight losses and
sugar concentrations, in addition to decreased acidity, relative to
traditional sun-drying methods (Bellincontro, De Santis, Botondi,
Villa, & Mencarelli, 2004). On the other hand, post-harvest
Table 1
Odor descriptors, odorant terms and threshold (mg/L) of the aroma compounds identifie
Compoundf Odor descriptors
Ethyl acetate Pineapple, varnish, anise
1,1-Diethoxyethane Green fruit, licorice
2,3-Butanedione Buttery
Ethyl propanoate Banana, apple
Propyl acetate Glue, celery, Christmas sweet
2-Butanol Vinous
2,3-Pentanedione Buttery
Hexanal Green
Isobutanol Alcohol, wine like, nail polish
Isoamyl acetate Banana
1-Butanol Medicinal
Isoamyl alcohols Alcohol, nail polish
Hexyl acetate Apple, pear, banana
Acetoin Buttery, cream
Ethyl lactate Strawberry, raspberry, buttery
E-3-Hexenol Green, grass
Ethyl heptanoate Sweet, strawberry, banana
1-Hexanol Grass, resinous, cream
Z-3-Hexenol Grass, green
E-2-Hexenol Green
Furfural Burn almond, incense, floral
1-Heptanol Oily
Benzaldehyde Bitter almond, nutty, smoky
5-Methylfurfural Bitter almond, spicy
Isobutanoic acid Rancid butter
g-Butyrolactone Coconut, caramel
3-Methylbutanoic acid Parmesan cheese, rancid
Butanoic acid Rancid, cheese
Methionol Cooked potato, cut hay
Geranial Citrus, sweet
g-Heptalactone Coconut, herbaceous, caramel
Phenethyl acetate Rose, honey
Benzyl alcohol Fruity, walnut
Phenethyl alcohol Rose, honey
Hexanoic acid Cheese
g-Decalactone Peach
Farnesol Fruity, balsamic, floral, clove
a Wine Aroma Wheel terms.
b From Gemert (2003).
c From Da Porto and Nicoli (2002).
d From Lasekan, Buettner, and Christlbauer (2007).
e Determined by authors.
f Thecompounds are arranged by the retention time in GC analysis.
dehydration in a drying chamber has been used to extend ripening
in grapes for various uses as it provides sugar contents and aromas
consistent with those obtained by natural on-vine ripening
(Moreno et al., 2008).
The grape drying process involves two simultaneous transfer
phenomena: heat (energy) transfer to the product and water
(mass) transfer from the inside to its outer surface, followed by
evaporation from it. How fast the process develops depends on
various factors including berry shape and size, the contact surface
area exposed to the transfer medium and the physical properties of
the drying medium. In chemical terms, the energy transfer causes a
general increase in the reaction rates, even activating some
mechanism scarcely significant at lower temperature, such as
Maillard reaction. The water loss leads to a decrease in the water
activity (in its most part determined by the sugar concentration),
which in addition can influence the reaction rates. In any case,
drying results in irreversible deterioration of the cell structure in
the product to an extent that depends essentially on the particular
drying method and conditions (Rahman, 2005; Ramos, Silva,
Sereno, & Aguilera, 2004).
In summary, the grape-drying step, which is the first in the
production of Pedro Ximenez sweet wines, requires careful control.
Ensuring an appropriate aroma profile in these wines entails
establishing the odorant activity of the raisin musts as this dictates
d in musts from cv. Pedro Ximenez raisins.
Odorant termsa Threshold
Tropical fruit, pungent, spicy 3280b
Tree fruit, spicy 42b
Caramelized 128c
Tree fruit 10b
Chemical, canned-cooked, caramelized 2000b
Chemical 3300b
Caramelized 20b
Fresh 9.1b
Chemical, pungent 16,000b
Tropical fruit 2500b
Phenolic 74,000b
Chemical, pungent 3060b
Tree fruit, tropical fruit 115b
Caramelized 800d
Berry, caramelized 250,000b
Fresh 110b
Caramelized, berry, tropical fruit 2b
Fresh, resinous, caramelized 1620b
Fresh 910b
Fresh 100b
Burned, floral 770b
Chemical 4600b
Nutty, burned 4600b
Nutty, spicy 1110b
Lactic 50b
Tropical fruit, caramelized 1000b
Lactic 20b
Lactic 1400b
Canned-cooked, fresh 50e
Citrus, caramelized 410b
Tropical fruit, fresh, caramelized 400b
Floral, caramelized 5000b
Tree fruit, nutty 100,000b
Floral, caramelized 60b
Lactic 1800b
Tree fruit 10b
Tree fruit, fresh, floral, spicy 20b
M.J. Ruiz et al. / LWT - Food Science and Technology 59 (2014) 560e565562
the aroma of the final wine. In this work, it is examined the influ-
ence of temperature during the chamber-drying of cv Pedro Ximenez
grapes on the aroma profile ofmustsmade from themwith a view to
developing an advantageous alternative to the traditional sun-
drying process used in the production of Pedro Ximenez sweet
wines.
2. Material and methods
2.1. Musts
Ripe grapes cv. Pedro Ximenez were collected in the Montillae
Moriles region (southern Spain). Three batches of grapes of 8 kg
each one were distributed uniformly (14 kg/m2) in a single layer
and dried in chamber (Frisol Climatronic, Córdoba, Spain) at air
temperatures of 40 �C and 50 �C, respectively, and humidity of
30%. To obtain a homogeneous drying the grapes were turned 4
times during the process. Samples were periodically collected
and the loss weight of the grapes was measured. The reducing
sugar content (measured as �Brix) was used as tracking criterion
of the grape dehydration process. The drying was concluded
when the sugar concentration was around 450 g/L. Three batches
of not dried grapes of 8 kg were used as control (0 h in Tables 2
and 3).
The grapes were crushed and subsequently pressed in a vertical
press similar to those used at the industrial level (EG-250 Sanahuja,
Castellon, Spain). The highest pressure reached in each pressing
cycle was 3$107 Pa, and each grape batch was pressed in three cy-
cles in a thermostatized chamber at 20 �C. The musts thus obtained
were centrifuged at 4280 g and subjected to the different
determinations.
2.2. Experimental analyses
The �Brix was measured by using a Master-Baume model
refractometer (ATAGO CO, LTD, Tokyo, Japan) previous 1:2 dilution
of the must samples. The pH, titratable and volatile acidities were
determined according to the European Community Official
analytical methods (EEC, 1990). The absorbance values at 420 nm
were obtained in a PerkineElmer Lambda 25 model spectropho-
tometer (Waltham, USA). All the measurements were carried out in
triplicate.
Each aroma compound was identified by means of its reten-
tion time, coeluted with a standard solution of commercial
product (Sigma Aldrich, Munich, Germany), and confirmed by
Mass Spectrometry (HewlettePackard 5972 MSD, Palo Alto, CA,
USA). The conditions of MS were scan mode (EM 1612 V) and
mass range from 39 to 300 amu. The chromatographic column,
injector and oven temperatures, carrier gas and its flow were the
same that those used for the quantification, being described
below.
Table 2
Analytical determinations (n ¼ 3) for the musts from chamber-dried cv. Pedro Ximenez g
Variable Time of drying (h)
0 46 73
40 �C
Weight loss (%) 0 34.5 47.2
Sugars (g/L) 216 � 1 330 � 1 409 �
pH 3.63 � 0.06 3.60 � 0.01 3.56 �
Titratable acidity (g tartaric acid/L) 2.55 � 0.08 3.60 � 0.09 4.13 �
Volatile acidity (mg acetic acid/L) 60.6 � 0.1 126 � 2 246 �
Absorbance (420 nm) 0.519 � 0.007 e e
For the quantification of the aroma compounds, samples of
100 mL of must were adjusted to pH 3.5 (by addition of HCl 0.1 mol/
L), 150 mg of 2-octanol was added as an internal standard and then
extracted with 100 mL of freon-11 (SigmaeAldrich Quimica, S.A.,
Madrid, Spain) in a continuous extractor for 24 h. These compounds
were quantified by GC (HewlettePackard 5890 series II) in a HP-
INNOWax column of 60 m � 0.32 mm � 0.25 mm thickness (Agi-
lent Technologies, CA, USA) after concentration of the freon extracts
in a Kuderna-Danish concentrator to 0.2 mL. Three mL were injected
into the chromatograph equipped with a split/splitless injector and
a FID detector. The oven temperature program was as follows:
5 min at 45 �C, 1 �C/min up to 185 �C and 30 min at 185 �C. Injector
and detector temperatures were 275 �C and 300 �C respectively.
The carrier gas was helium at 0.07 Pa and split 1:100. The quanti-
fication was made by using chromatographic response factors,
calculated for each compound in relation to the internal standard,
in standard solutions of commercial products (purity > 95%) sup-
plied by Sigma Aldrich (Munich, Germany). The analysis was made
by triplicate.
2.3. Odor descriptor, methionol threshold and odor activity values
Direct olfaction of the commercial products on water solutions
of each compound was carried out. A solution of each compound
with a concentration slightly higher than its perception threshold
(10%) was used. This perception threshold was obtained from the
bibliography and it is shown in Table 1. The olfactory assessment
was carried out by direct method in flasks according to the ISO
5496:1992 standard (the specimen answer form used was the
corresponding to the Annex B of this standard). The taste panel
consisted of 20 judges of both sexes (12 female and 8 male) be-
tween 20 and 55 years old (ISO 5496:1992). All judges were trained
in preliminary sessions. Reference standards taken from Sigmae
Aldrich (Munich, Germany) and from “Le nez du vin” (Jean Lenoir,
Provence, France) were presented (five per session). During the
training, judges discussed about odor descriptors andmodified it by
eliminating descriptors they considered irrelevant or redundant.
The responses of the judges were compiled for all aroma com-
pounds and those odor descriptors cited by less than 15% of the
panel were eliminated. The odor descriptors indicated by the
judges for the 38 compounds studied are listed in Table 1. For
determination of methionol threshold (data not found in bibliog-
raphy) five solutions of ascending concentration of this compound
were used.Starting from the lowest concentration solution, the
judges indicated which one of them showed an odorant sensation
different to the perceived in the control (distilled water), according
to the ISO 5495:1983 norm.
The Odor Activity Value (OAV) for each compound was calcu-
lated by dividing its concentration determined in the must by the
concentration corresponding to its odor threshold.
rapes.
96 21 45 70
50 �C
55.0 36.1 45.5 56.4
1 480 � 1 338 � 1 396 � 1 495 � 1
0.06 3.70 � 0.01 3.90 � 0.01 4.01 � 0.01 4.25 � 0.03
0.07 4.35 � 0.07 2.69 � 0.05 2.79 � 0.07 2.93 � 0.08
1 486 � 2 264 � 1 325 � 1 345 � 2
0.815 � 0.019 e e 1.65 � 0.02
Table 3
Mean and standard deviation (n¼ 3) of the contents (mg/L) and the ratio between the initial and final concentration (CR) for the aroma compounds of themusts from chamber-
dried cv. Pedro Ximenez grapes.
Compounda Time of drying (h)
0 46 73 96 21 45 70 CR
40 �C 50 �C 40 �C 50 �C
Ethyl acetate 199 � 20 15,388 � 3020 21,032 � 2926 31,719 � 4686 4135 � 200 8861 � 428 18,627 � 1409 159.4 93.6
1,1-Diethoxyethane 23 � 3 314 � 62 890 � 170 1669 � 247 161 � 8 345 � 17 933 � 70 72.6 40.6
2,3-Butanedione 104 � 15 500 � 72 732 � 19 930 � 70 818 � 94 964 � 199 1434 � 172 8.9 13.8
Ethyl propanoate 5 � 1 21 � 4 27 � 1 29 � 4 13 � 1 16 � 2 19 � 4 5.8 3.8
Propyl acetate nd nd nd nd 9 � 1 22 � 3 16 � 3 e e
2-Butanol 2.6 � 0.4 6 � 2 53 � 5 120 � 9 4.6 � 0.7 8.3 � 0.8 7.9 � 0.9 46.2 3.0
2,3-Pentanedione 7 � 2 18 � 3 25.9 � 0.5 30 � 5 14 � 3 24 � 4 37 � 8 4.3 5.3
Hexanal 4.1 � 0.8 31 � 5 48 � 5 62 � 10 4.5 � 0.3 5.3 � 0.2 21.6 � 0.2 15.1 5.3
Isobutanol 1883 � 160 4141 � 320 10,265 � 434 16,455 � 776 1430 � 52 3065 � 111 6157 � 776 8.7 3.3
Isoamyl acetate 16 � 2 16 � 3 18.2 � 0.5 19 � 1 15 � 1 17 � 3 17 � 2 1.2 1.1
1-Butanol 7 � 1 129 � 17 160 � 19 248 � 40 112 � 16 77 � 4 172 � 35 35.4 24.6
Isoamyl alcohols 2526 � 778 4643 � 311 16,283 � 1306 21,718 � 893 3575 � 516 4777 � 506 7743 � 15 8.6 3.1
Hexyl acetate 5 � 1 3 � 1 5 � 2 2.3 � 0.3 7.6 � 0.9 7.9 � 0.6 6.0 � 0.6 0.5 1.2
Acetoin 209 � 3 16,085 � 1533 58,650 � 15,839 90,518 � 4174 5901 � 1152 9671 � 1279 14,648 � 1387 4331.0 70.1
Ethyl lactate 90 � 15 110 � 19 141 � 22 155 � 26 30 � 3 23 � 3 19 � 4 1.7 0.2
E-3-hexenol 70 � 15 57 � 9 24 � 7 nd nd nd nd e e
Ethyl heptanoate nd nd nd nd 6 � 1 5.1 � 0.5 7 � 2 e e
1-Hexanol 373 � 28 45 � 8 54 � 2 65 � 16 79 � 12 67 � 4 49 � 10 0.2 0.1
Z-3-hexenol 51 � 9 28 � 5 18 � 3 15 � 2 7.5 � 0.6 6.6 � 0.5 4.5 � 0.6 0.3 0.1
E-2-hexenol 48 � 2 nd nd nd 39 � 6 20 � 2 13 � 2 0 0.3
Furfural 14.8 � 0.6 19 � 5 24 � 6 28.2 � 0.1 56 � 7 60 � 4 61 � 3 1.9 4.1
1-Heptanol nd 6 � 2 33.2 � 0.8 37 � 8 16 � 3 17 � 1 13 � 3 e e
Benzaldehyde nd nd nd 13 � 3 nd nd 9 � 2 e e
5-Methylfurfural nd nd nd 5.8 � 1.4 5.3 � 0.8 7.2 � 0.5 8.4 � 0.9 e e
Isobutanoic acid 127 � 15 399 � 40 446 � 34 495 � 95 119 � 4 69 � 5 60 � 5 3.9 0.5
g-Butyrolactone 121 � 16 303 � 32 349 � 20 399 � 43 1759 � 139 3855 � 256 2178 � 251 3.3 18.0
3-Methylbutanoic acid 25 � 5 35 � 4 52 � 1 110 � 30 15 � 2 7.9 � 0.3 2.6 � 0.4 4.4 0.1
Butanoic acid 29 � 5 21 � 4 27.0 � 0.3 40 � 3 16 � 2 11.0 � 0.3 10 � 2 1.4 0.3
Methionol 17 � 2 16 � 3 37 � 3 42 � 1 5.0 � 0.3 7.7 � 0.7 5.9 � 1 2.5 0.3
Geranial 9 � 2 39 � 8 40 � 2 60 � 10 10 � 1 14 � 2 12 � 3 6.7 1.3
g-Heptalactone 7 � 0.7 22 � 5 31 � 4 39 � 3 5.2 � 0.9 4.6 � 0.6 4.1 � 0.7 5.6 0.6
Phenethyl acetate 6 � 1 14 � 3 25 � 4 20 � 4 2.2 � 0.3 2.7 � 0.4 6.1 � 0.6 3.3 1.0
Benzyl alcohol 209 � 31 347 � 22 371 � 34 391 � 12 30 � 2 29 � 2 29 � 2 1.9 0.1
Phenethyl alcohol 1922 � 115 4318 � 395 6106 � 1025 14,193 � 763 2140 � 301 2429 � 210 4609 � 312 7.4 2.4
Hexanoic acid 23 � 4 26 � 4 25 � 6 17 � 3 7.1 � 0.6 4.9 � 0.8 2.8 � 0.3 0.7 0.1
g-Decalactone 19 � 5 14 � 3 17 � 3 20 � 6 5.0 � 0.6 8.7 � 0.8 2.9 � 0.5 1.1 0.2
Farnesol 23 � 2 28 � 6 24 � 3 29 � 3 33 � 1 35 � 43 40 � 6 1.3 1.7
n.d. ¼ not detected.
a The compounds are arranged by the retention time in GC analysis.
M.J. Ruiz et al. / LWT - Food Science and Technology 59 (2014) 560e565 563
2.4. Statistical procedures
ANOVA, Principal Components and Regression Analyses were
carried out by using the Statgraphics� 5.0 (STSC Inc., Rockville, MD,
USA) computer program.
3. Results and discussion
Table 2 shows the results of the analytical determinations car-
ried out on the studied musts. As can be seen, the drying process
was stopped at a weight loss of ca. 55% in the berries, which
occurred about 26 h earlier in the grapes dried at 50 �C than in
those dried at 40 �C. Moisture losses and the increase in sugar
concentration were highly correlated (r ¼ 0.9172) throughout the
drying process. The resulting musts showed large amounts of
sugars (about 500 g/L), it being suitable for making the typical
sweet wines of the MontillaeMoriles region.
The lower pH (i.e. the higher titratable acidity) of themusts from
grapes dried at 40 �C reflected a greater acidity than to those from
grapes dried at 50 �C. However volatile acidity in the musts from
grapes dried at 50 �C was greater except for the musts from grapes
dried during 70 h. The increased musts acidity must have resulted
partly from cell metabolism in the grapes switching from aerobic to
anaerobic during the drying process and ADH activity increasing as
a result, thereby leading to increased formation of ethanol and
subsequent oxidation to acetate (Bellincontro et al., 2004;
Costantini, Bellincontro, De Santis, Botondi, & Mencarelli, 2006).
As reflected in the absorbance at 420 nm, the final musts from
grapes chamber-dried at 50 �C were darker than the others by effect
of Maillard browning reactions, which are temperature-dependent,
occurring to a greater extent in them. In fact, the concentrations of
furfural and 5-methylfurfural (Table 3), two typical products of
chemical browning reactions, increased with drying time and were
obviously higher in the musts from grapes dried at 50 �C.
Table 3 shows the contents in aroma compounds of the musts.
As can be seen, drying at 40 �C raised the means all compounds
studied by exception of hexyl acetate, E-3-hexenol, 1-hexanol, Z-3-
hexenol, E-2-hexenol and hexanoic acid. The results for the musts
from grapes dried at 50 �C were similar except that the compound
E-3-hexenol was not found during the process. In addition, ethyl
lactate, isobutanoic, 3-methylbutanoic and butanoic acids,
methionol, g-heptalactone, benzyl alcohol and g-decalactone
decreased. Also, drying at 50 �C led to musts containing propyl
acetate and ethyl heptanoate, whichwere not detected in themusts
from grapes dried at the lower temperature. The changes observed
could be explained take into account different balances for the
synthesis and/or hydrolysis reactions during the drying process.
Mainly, these reactions develop by chemical pathway although
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Fig. 1. Odorant profiles (OAVs) of musts from not dried grapes and from grapes
chamber-dried at 40 �C and 50 �C during 96 h or 70 h, respectively. The OAVs of the
terms quantitatively higher, caramelized, floral and lactic were divided by 10 to better
observe the figure.
Fig. 2. Principal components analysis carried out on the odorant terms of the musts
from not dried grapes (�) and from grapes chamber-dried at 40 �C (,) and 50 �C (B).
M.J. Ruiz et al. / LWT - Food Science and Technology 59 (2014) 560e565564
enzymatic changes on the metabolism of the grapes should be
considered as above-mentioned.
On the other hand, the results were subjected to ANOVA at
pThe contents of 2,3-pentanedione, E-3-hexenol, 1-hexanol
and benzaldehyde were not affected by the drying temperature;
therefore, these compounds exhibited a similar concentration/loss
balance. The other compounds studied exhibited differences at the
same significance level and may thus be used as key compounds
towards distinguishing themusts obtained at the two temperatures
in terms of aroma.
Table 3 also lists the ratio between the final and initial con-
centrations (CR) obtained by dividing the average concentration of
each compound at the end of the drying process (96 h at 40 �C and
70 h at 50 �C) into its initial concentration. If the weight loss from
the grapes is exclusively ascribed to water evaporation, then, the
initial contents of the grape were roughly 2.3 times concentrated at
the end. Therefore, the compounds with CR > 2.3 must have been
synthesized during the process, whether chemically or biochemi-
cally (10), whereas thosewith CR 50. In
this sense, the odorant activity of fruit, pungent, spicy and cara-
melized notes has been increased, reasonably enriching the aroma
profile of the musts. Also worth noting in terms of CR were 2-
butanol, 1-butanol and hexanal, which contribute vinous, medici-
nal and green notes. On the other hand, E-3-hexenol, E-2-hexenol,
1-hexanol and Z-3-hexenol, which are mainly responsible for
vegetable notes, were the compounds exhibiting the greatest losses
during drying of the grapes. The compounds with the highest CR in
the musts from grapes dried at 50 �C were ethyl acetate and ace-
toin, albeit whichmuch lower values than in themusts from grapes
dried at 40 �C, particularly acetoin. 1,1-Diethoxyethane, 1-butanol,
g-butyrolactone (coconut, caramel), and 2,3-butanedione (buttery)
also exhibited high CR values. In any case, the final musts from
grapes dried at 40 �C contained greater amounts of aroma com-
pounds than did those from grapes dried at 50 �C.
Fig. 1 shows the odorant profiles of the musts from not dried
grapes (0 h) and the final musts obtained from chamber-dried
grapes at 40 �C during 96 h or 50 �C during 70 h, based on the
odorant activity values (OAVs > 1) for the odorant terms. First, the
OAVs for the individual compounds included in each odorant term
were calculated by dividing its concentration in the musts by the
respective threshold. Then, the OAVs of each odorant term repre-
sented in the Fig. 1 were calculated by adding those for the indi-
vidual compounds grouped in each term. Tables 1 and 3 supplies
the necessary information for obtain the OAVs. Although the OAVs
thus obtained do not necessarily represent the arithmetic sum of
the individual aroma perceptions, they facilitate comparison of the
aroma profiles for musts of the same type since the odorant terms
in them include the same compounds.
As can be seen in Fig. 1, the polygonal lines representing the
odorant profiles for themusts were identically shaped but larger for
that from grapes dried at 40 �C. Therefore, both musts possessed a
similar overall aroma, which, however, in odor activity terms was
stronger in that from grapes dried at the lower temperature. All
odorant terms except that for tropical fruit exhibited differences at
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	Changes in aroma profile of musts from grapes cv. Pedro Ximenez chamber-dried at controlled conditions destined to the prod ...
	1 Introduction
	2 Material and methods
	2.1 Musts
	2.2 Experimental analyses
	2.3 Odor descriptor, methionol threshold and odor activity values
	2.4 Statistical procedures
	3 Results and discussion
	4 Conclusions
	Acknowledgments
	References