Differences in Volatile Ester Composition Between Fragaria Ananassa and F

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Scientia Horticulturae 150 (2013) 47–53

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Differences in volatile ester composition between Fragaria ananassa and F.

ଝ

vesca and implications for strawberry aroma patterns

a,b b c b a,∗

Jing Dong , Yuntao Zhang , Xiaowei Tang , Wanmei Jin , Zhenhai Han

Institute for Horticultural Plants, College of Agronomy and Biotechnology, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, PR China

Institute of Forestry and Pomology, Beijing Academy of Agriculture and Forestry Sciences, No. 12 Ruiwangfen, Xiangshan, Haidian District, Beijing 100093, PR China

Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Sciences, Banjin, Haidian District, Beijing 100097, PR China

a r t i c l e i n f o a b s t r a c t

Article history: Esters are a very important component of strawberry (Fragaria sp.) aroma. In this study, fruit volatiles

Received 8 April 2012

were isolated by solid-phase microextraction and analyzed by gas chromatography–mass spectrometry

Received in revised form 1 November 2012

(SPME/GC–MS). It was found that F. × ananassa had more esters than F. vesca, but there was no signiﬁcant

Accepted 1 November 2012

difference in average relative content of esters. Twenty ﬁve esters were selected as predominant esters,

16 of which were prevalent in F. × ananassa and another 16 in F. vesca. Among them, hexyl acetate,

Keywords:

octyl acetate, ethyl butyrate, ethyl hexanoate, ethyl octanoate, methyl decanoate, and ethyl decanoate

Volatile ester composition

were found in both F. × ananassa and F. vesca, while 1-methyltridecyl acetate, myrtenyl acetate, trans-

Aroma pattern

pinocarvyl acetate, and ethyl dodecanoate were only present in F. vesca. The numbers of carbons of the

F. × ananassa

predominant esters in F. × ananassa were usually smaller than those of F. vesca. Ethyl hexanoate and octyl

F. vesca

acetate were the esters with the highest average concentrations in F. ananassa and F. vesca, respectively.

It was found that hexyl acetate, methyl butyrate, hexyl butyrate, methyl hexanoate, and ethyl hexanoate

≥

were major contributors to the aroma of cultivated strawberry because their odor values were 1 in every

cultivar, however, no ester was found to be so important like that for all of the F. vesca accessions. Most

of the predominant esters of F. ananassa were described as having only fruity odor. Unlike the case of

F. × ananassa, nearly all of the predominant esters of F. vesca have a noticeable ﬂoral odor in addition to a

fruity note. That may contribute to the variations in fruit aroma. The average number and proportion of

acyl and alkyl esters differed between species. Acetate esters predominated in F. vesca, accounting for a

signiﬁcantly higher average proportion of total esters than in F. ananassa. All the differences in volatile

esters are likely to play a key role in the different aroma patterns of F. × ananassa and F. vesca.

1. Introduction Fruit aroma is the result of the presence of various aroma com-

pounds. Researchers have been studying the differences in aroma

Strawberry (Fragaria sp.) is planted throughout the world. One volatiles between the cultivated strawberry (F. × ananassa) and

of the major quality characteristics of strawberry is its aroma. It has wild strawberry species. Staudt et al. (1975) detected 120 volatile

been reported that a large number of volatile compounds such as compounds in fruit of F. nilgerrensis and found that it had a different

esters, terpenes, alcohols, ketones and furans contribute to straw- aroma composition from that of F. × ananassa, with methyl ben-

berry aroma (Pérez et al., 1992; Zabetakis and Holden, 1997). The zoate, benzyl acetate, methyl cinnamate, and ethyl cinnamate being

fruit aroma is inﬂuenced by genotype and environment (Forney the most prominent in the former. Pyysalo et al. (1979) identiﬁed

et al., 2000). Wild strawberries tend to have a more intense aroma butyl formate, octyl acetate, decyl acetate, benzyl acetate, carveyl

than cultivated ones. Fruit aroma patterns vary among Fragaria sp. acetate, decyl butanoate, methyl nicotinate, methyl anthranilate,

(Ulrich et al., 2007). and methyl N-formylanthranilate in wild strawberries, but none in

F. × ananassa. Ulrich et al. (1997) reported that the main sensory

profiles of F. vesca including aromatic, flowery, sweet, and flavor

differed notably from those of cultivated cultivars.

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This study was ﬁnancially supported by the Beijing Science and Technology F. vesca has been extensively investigated because of its intense

Nova Project (2008B36), the Beijing Natural Science Foundation (6122013) and the

aroma (Hirvi and Honkanen, 1982; Pyysalo et al., 1979; Ulrich et al.,

Beijing Science and Technology Project (Z111100056811035-2). We thank Shahrokh

2007). Compared with F. × ananassa, F. vesca has a marked ﬂoral

Khanizadeh for his review for the manuscript.

∗ odor. The esters and terpenes of F. vesca are quite different from

Corresponding author. Tel.: +86 10 62732467; fax: +86 10 62736613.

E-mail address: [email protected] (Z. Han). those of F. ananassa (Zabetakis and Holden, 1997). The major

48 J. Dong et al. / Scientia Horticulturae 150 (2013) 47–53

esters contributing to the aromas of F. vesca and F. × ananassa are Shenzhen, China) into a 15 mL sample vial, and sealed hermeti-

also different. Methyl anthranilate is a major aroma compound of F. cally. Volatiles were extracted using solid-phase microextraction

vesca, whereas methylbutanoate, ethyl butanoate, ethyl hexanoate, (SPME). An SPME ﬁber coated with 100 ␮M polydimethylsiloxane

and methyl 2-methylbutanoate are among the most important (Supelco Inc., Bellefonte, USA) was inserted into the headspace of

◦

odorants of F. × ananassa (Larsen and Poll, 1992; Schieberle and each sampling vial. The vials were then heated in a 35 C water bath

Hofmann, 1997). for 25 min to facilitate the release of volatile compounds from the

Esters, the largest group of aroma compounds in strawberry, sample to the headspace. The SPME ﬁber was removed from the

account for approximately 25–90% of the volatiles of this fruit, giv- vial and immediately injected into the gas chromatograph (GC).

ing it fruity and ﬂowery odors (Beekwilder et al., 2004; Douillard

and Guichard, 1990; Jetti et al., 2007; Pérez et al., 1992, 1997; 2.4. GC–MS analysis

Schieberle and Hofmann, 1997). The content of esters is thought to

be an important basis for the classiﬁcation of aroma patterns (Ulrich SPME ﬁbers were desorbed in the injection port of a Shi-

et al., 1997, 2007). In the related papers which have been reported, madzu QP2010 gas chromatograph–mass spectrometer (GC–MS)

◦

single aroma components including esters were compared among (Shimadzu Co., Kyoto, Japan) at 250 C for 1 min, in splitless

different species or cultivars (Aharoni et al., 2004; Pyysalo et al., mode. A DB-5MS column (J & W Scientiﬁc Inc., Folsom, USA)

× × ␮

1979; Zabetakis and Holden, 1997). However, no reports compared (30 m 0.25 mm i.d. 0.25 m ﬁlm thickness) was used. The car-

a certain type of volatile compounds to analyze the differences rier gas was ultra-high purity helium (99.999%). The injection port

further. This study focused on esters and their impact on aroma was subjected to a pressure of 51.3 kPa, and the GC oven tem-

◦

patterns for the ﬁrst time to help researchers understand why perature program consisted of an initial temperature of 40 C for

◦ ◦ −1

strawberry fruits have different types of aroma. 2 min, increasing to 220 C with a rate of 8 C min , and holding

◦

Before this experiment was carried out, a preliminary test had at 220 C for the ﬁnal 6 min. Mass spectra in the range m/z 30–550

been done. It was resulted that there were little differences in ester were obtained by electron ionization (EI) at 70 eV. The ion source

◦ ◦

composition between Japanese cultivars and European & USA cul- temperature was 200 C, and the interface temperature was 250 C.

tivars. It was also concluded that though planting pattern could Identiﬁcation of the compounds was achieved by comparing

inﬂuence esters on number, type, proportion, etc., the data of green- their mass spectra with those in the NIST (National Institute of

house showed good consistency in continuous years. Standards and Technology) library and the Wiley library. Standard

Among modern cultivars, Japanese cultivars of F. × ananassa compounds were analyzed in the same conditions as the samples.

usually have a stronger aroma than other cultivars. Considering that Compounds were tentatively identiﬁed by searching for matches

it is an important trend to breed more aromatic strawberries and in the mass spectral libraries, and then had their identities con-

Japanese cultivars and wild species (esp F. vesca) certainly will play ﬁrmed by comparing their GC retention times with those of

a valuable role in future aroma breeding, we focused on compar- authentic compounds. The identities of most compounds were

ing volatile esters between Japanese cultivars and F. vesca strains conﬁrmed.

in this study. The volatile ester composition of seven Japanese

F. × ananassa cultivars and six accessions of F. vesca, which were 2.5. Data processing

selected out of nearly 100 collections on the basis of cluster analy-

sis of fruit volatiles in the preliminary test, were compared to seek The total ester content was calculated using the peak areas, and

to explain the different aroma patterns of the strawberries in terms expressed as percentage of the total volatiles. The peak areas were

of esters. also used to calculate the proportion of each type of ester relative

to the total esters.

2. Materials and methods Calibration curves were constructed for the quantitative analy-

sis of individual esters. In the absence of standard compounds, an

2.1. Plants approximate quantitative method using the calibration curves of

compounds with similar chemical structures and carbon numbers

Seven F. × ananassa cultivars, ‘Harunoka’, ‘Kunouwase’, ‘Beni- was applied.

hoppe’, ‘Hokowase’, ‘Kitanokagayaki’, ‘Toyonoka’ and ‘Sachinoka’, Odor values of eight esters were calculated. Each ester’s average

along with six F. vesca accessions, ‘UC4’, ‘UC5’, ‘Jinchuan’, ‘Maox- odor value in F. ananassa or F. vesca was expressed as the average

ian’, ‘Northeast Wild’, and ‘Fifteen Kuang’ were planted in an open of odor values of tested accessions.

ﬁeld. Twenty plants with consistent growth vigor were selected SAS software (version 8.0, SAS Institute Inc., Cary, NC) was used

from each accession. The first and second fruit of the first inflo- for the statistical analysis (t test at P < 0.05, 0.01).

rescence of each plant were collected when fully ripe. The berries

3. Results

were immediately placed in sealable bags, deep frozen and stored

◦

at −40 C until analysis.

3.1. Ester content

2.2. Chemicals

A total of 97 esters were identiﬁed in fruit of F. × ananassa, while

Authentic standards of hexyl acetate, octyl acetate, nonyl 57 esters were detected in F. vesca. The average number of esters

acetate, myrtenyl acetate, ethyl butanoate, hexyl butanoate, octyl in F. ananassa cultivars was higher than in F. vesca accessions

butanoate, methyl hexanoate, ethyl hexanoate, hexyl hexanoate, (P < 0.01, Table 1). ‘Kitanokagayaki’ had the most esters (41), and

methyl octanoate, ethyl octanoate, methyl decanoate, and ethyl ‘Maoxian’ the least (only 9). Although the average relative content

decanoate were purchased from Sigma–Aldrich (St. Louis, MO, of esters was 54.44% of total volatiles for F. ananassa and 39.32%

USA). for F. vesca, the difference was not signiﬁcant.

2.3. SPME extraction 3.2. Predominant esters and their contribution to the aroma

Fruits were thawed and homogenized, then 8 g of homogenate From all the identiﬁed esters, we selected 25 predominant

were quickly transferred from the blender (PHILIPS, HR2094, esters based on the criterion that they should be present in

J. Dong et al. / Scientia Horticulturae 150 (2013) 47–53 49

Table 1

so their odor values were far higher than those of the other

Number and relative content of esters, expressed as % total volatiles, detected in

esters. The odor values of hexyl acetate, methyl butanoate, hexyl

accessions of F. × ananassa and F. vesca.

butanoate, methyl hexanoate, and ethyl hexanoate were ≥1 in

Sources Number of esters Relative content

every cultivar. Therefore, these ﬁve esters are considered to be

of esters (%)

important to the aroma of cultivated strawberry. In addition, ethyl

F. ananassa acetate was found to be a major aroma compound for ‘Beni-

Harunoka 23 65.05

hoppe’, ‘Kitanokagayaki’, and ‘Sachinoka’, while ethyl butanoate

Kunouwase 37 61.37

was important for six cultivars, except ‘Harunoka’. Unlike the

Benihoppe 25 62.59

case of F. × ananassa, none of these eight esters was a major

Hokowase 25 40.09

Kitanokagayaki 41 59.67 aroma compound for all of the F. vesca accessions. However,

Toyonoka 29 59.91

hexyl acetate, ethyl butanoate, and ethyl hexanoate were very

Sachinoka 34 32.39

z important for ‘UC4’, ‘UC5’, ‘Jinchuan’, ‘Northeast Wild’, and ‘Fifteen

Mean ± SE 30.6 ± 2.6A 54.44 ± 4.8a Kuang’.

F. vesca

UC4 10 7.99

UC5 26 62.96 3.3. Ester classiﬁcation

Jinchuan 23 46.41

Maoxian 9 16.21

Each ester molecule is composed of an acyl fraction and an alkyl

Northeast Wild 23 61.52

fraction (Pelayo-Zaldívar et al., 2007), a fact that can be useful for

Fifteen Kuang 23 40.85

Mean SE 19.0 ± 3.0B 39.32 ± 9.3a ester classiﬁcation. In this study, we found that acetate, butanoate,

z hexanoate, octanoate, and decanoate were the ﬁve major acyl frac-

Means in the same column followed by different lowercase letters are signiﬁ-

cantly different at P < 0.05 between F. × ananassa and F. vesca, while means followed tions in strawberries (Tables 4 and 5). In F. ananassa, the contents

by different uppercase letters are signiﬁcantly different at P < 0.01. of acetate, butanoate, hexanoate and octanoate esters were higher

than those of decanoate esters. In ‘Harunoka’, ‘Kunouwase’ and

‘Benihoppe’, acetates represented the highest proportion of esters.

no less than half of the accessions of F. × ananassa or F. vesca.

The same was true for butanoates in ‘Kitanokagayaki’, and hex-

Their concentrations were calculated and compared (Table 2). Six-

anoates in ‘Hokowase’, ‘Toyonoka’, and ‘Sachinoka’. In contrast,

teen of these esters were prevalent in F. × ananassa and another

acetates were predominant in F. vesca, accounting on average for

16 in F. vesca. Among them, hexyl acetate, octyl acetate, ethyl

81.92% of total esters, with proportions ranging from 77.50% to

butanoate, ethyl hexanoate, ethyl octanoate, methyl decanoate,

95.70%. The average proportion of acetates in F. ananassa was

and ethyl decanoate were found in both F. ananassa and F.

signiﬁcantly lower than in F. vesca (P < 0.01). However, the aver-

vesca. In addition, some esters were speciﬁc to one or the other.

age number and proportion of butanoate, hexanoate and octanoate

For example, methyl butanoate, hexyl butanoate, methyl hex- ×

esters in F. ananassa were signiﬁcantly higher than in F. vesca

anoate, 3-methylbutyl hexanoate, and methyl octanoate were

(P < 0.01). Based on the proportions of each type of alkyl ester,

present in all F. × ananassa cultivars, but in F. vesca they were

methyl, ethyl and hexyl esters were predominant in F. × ananassa,

detected in only one accession or not detected at all. Similarly, 1-

while ethyl, hexyl, 1-methyltridecyl and myrtenyl esters were

methyltridecyl acetate, myrtenyl acetate, trans-pinocarvyl acetate,

predominant in F. vesca. In ﬁve F. × ananassa cultivars (exclud-

and ethyl dodecanoate were prevalent in F. vesca, but nonexist-

ing ‘Harunoka’ and ‘Hokowase’), ethyl esters accounted for the

ent in F. × ananassa. We also found that the number of carbons

highest proportion. In contrast, in F. vesca, ethyl esters were

of the predominant esters in F. × ananassa were ≤10, while those

≥ predominant in ‘UC4’, whereas hexyl esters were predominant

in F. vesca were 10. This is similar to the results obtained by

in ‘UC5’; 1-methyltridecyl esters accounted for the highest pro-

Pyysalo et al. (1979), who reported that 2-alkanones and 2-alkanols

portion of alkyl esters in ‘Jinchuan’ and ‘Northeast Wild’, and

in F. vesca had more carbons than those in the cultivar ‘Senga

myrtenyl esters accounted for the highest proportion in ‘Maox-

Sengana’.

ian’ and ‘Fifteen Kuang’. Furthermore, the average number and

In F. × ananassa cultivars, the concentration of ethyl hexanoate

−1 −1 proportion of methyl and hexyl esters in F. ananassa were sig-

ranged from 6.82 mg kg for ‘Harunoka’ to 145.08 mg kg for

−1 niﬁcantly higher than in F. vesca (P < 0.01). It should be noted

‘Toyonoka’, with a mean value of 48.98 mg kg . In contrast, in F.

−1 that 1-methyltridecyl and myrtenyl esters were undetectable in

vesca, the concentration of ethyl hexanoate ranged from 0 mg kg

−1 F. ananassa.

for ‘Maoxian’ to 14.75 mg kg for ‘Northeast Wild’, with a mean

−1

value of 5.61 mg kg . Octyl acetate was the ester found in the

−1 4.

highest concentration (18.79 mg kg ) in F. vesca. Ethyl hexanoate, Discussion

methyl hexanoate, methyl butanoate, ethyl butanoate and ethyl

octanoate were the esters with the highest average concentrations Esters are the most abundant volatiles in strawberries and con-

in F. × ananassa, whereas in F. vesca, the esters with the highest tribute a lot for fruit fragrance (Beekwilder et al., 2004; Jetti et al.,

concentrations were octyl acetate, ethyl acetate, 1-methyltridecyl 2007; Pérez et al., 1992, 1997; Schieberle and Hofmann, 1997).

acetate, ethyl octanoate and ethyl hexanoate. By comparing the In this study, the average number of esters in F. × ananassa culti-

concentrations of esters that were abundant in both F. × ananassa vars was signiﬁcantly higher than in F. vesca accessions. The aroma

and F. vesca, we found that the mean concentrations of hexyl of F. vesca was regarded to be stronger than cultivated cultivars

acetate, ethyl butanoate, ethyl hexanoate, and ethyl octanoate were (Hirvi and Honkanen, 1982). Although we found F. × ananassa had

higher in F. × ananassa than in F. vesca. However, the levels of more esters than F. vesca, it was apparent that other characteris-

octyl acetate, methyl decanoate, and ethyl decanoate were lower tics of esters may inﬂuence fruit aroma to a greater extent than the

in F. ananassa. number.

We calculated the odor values (the ratio of concentration to In the 25 predominant esters, seven esters were found in

odor threshold) for eight esters whose odor thresholds were both F. ananassa and F. vesca, and some other esters were spe-

found in the literature (Table 3). Compounds with an odor value ciﬁc to one or the other. It was showed that the predominant

≥ ×

1 are considered to be major contributors to the aroma. Ethyl esters that are common to both F. ananassa and F. vesca may

butanoate and ethyl hexanoate had very low odor thresholds, provide a similar odor background, and the species-speciﬁc esters

50 J. Dong et al. / Scientia Horticulturae 150 (2013) 47–53 0.085 0.27 0.68 0.077 0.078 0.00 0.061 0.00 0.00 0.21 0.42 2.28 2.21 1.11 1.18 4.05 1.24 5.61 8.98 4.49 1.01 1.03 10.84 Mean 14.94 18.79

Kuang

0.1 0.35 0.21 0.45 0 0 0 0 0 0 0 0 0 0 0.68 0 2.95 5.47 1.68 3.94 6.48 1.52 3.36 1.7 Fifteen 45.77

Wild

0 0.13 0.85 0.9 0.35 0 0 0 0 0.096 0 0 0.86 5.02 3.14 5.32 2.12 1.23 8.01 2.73 1.24 Northeast 12.98 39.47 14.75 16.76

0 0 0 0.14 0 0.084 0 0.36 0 0 0 0 0 0 0 0 0 0 0 0.66 0 0.18 0 2.49 5.49 Maoxian

0.17 0.75 0 0.46 0 0 0 0 0 0 0 0.77 2.94 9.73 1 5.82 4.05 2.03 7.58 2.46 1.01 20.26 Jinchuan 17.62 11.81 14.53

0 0.11 0 0 0 0 0.47 0 0.27 0 0 0 0.14 0.26 1.74 4.77 3.57 1.2 1.74 1.53 4.41 80.34 10.93 10.7 UC5 19.74

vesca

0 0 0 0 0 0 0 0 0 0.46 0 0 0 0 0 0 0 0 0 0 1 1.72 2.23 1.13 F. UC4 26.27

0.056 0.051 0.05 0.00 0.00 0.00 0.79 0.40 0.44 0.19 0.10 0.00 7.23 7.66 3.42 6.41 1.41 9.10 1.91 Mean 13.81 16.62 13.67 19.98 48.98 11.43

0 0.085 0 0.11 0 0 0 0 0.55 0.58 0.12 0 0 2.99 3.58 6.87 7.77 4.01 1.5 1.16 Sachinoka 15.65 14.54 29.05 12.4 13.05

0 0 0.12 0.24 0 0 0 0.76 0.31 0 0 4.48 2.02 2.51 3.37 1.19 3.06 1.59 1.85 . Toyonoka 21.11 13.49 41.53 16.53 21.61 145.08

vesca

and

0 0 0 0 0 0.19 0.65 0.26 0 0.081 0 0 9.53 3.64 4.59 6.14 50.93 50.73 30.25 32.89 18.66 21.11 13.59 72.33 ananassa ×

0 0 0 0 0 0 0 0 0.98 0.32 0 0.055 0 0 3.95 3.03 4.8 3.14 3.53 5.02 10.56 14.65 14.11 33.96 accessions

0 0 0 0 0.43 0.074 0.054 0.95 0.08 0 0.055 0 0 2.25 3.61 1.79 8.67 10.58 48.13 12.65 31.31 42.22 13.47 detected

esters

0 00.24 0 0 0 00 00.64 0.11 0.23 0 0.18 0.6 0.52 0 2.32 7.82 7.99 4.6 9.77 8.83 20.76 19.32 13.42

predominant ananassa

0 0 0 0 0 0.13 0.56 0.046 0.18 0 1.38 7.09 2.88 1.56 25 .

F Harunoka Kunouwase Benihoppe Hokowase Kitanokagayaki 25.04 the

) 1 −

acetate 0

kg acetate

acetate 0

hexanoate

acetate 3.08

(mg

dodecyl tridecyl ethyl butyl acetate 0 0 0

butanoate hexanoate octanoatedecanoate dodecanoate 3.44

acetate 0.075 acetate 5.28 butanoate hexanoate acetate

acetate butanoate acetate butanoatehexanoate 0octanoate 6.82 6.24 decanoatedodecanoate 0.074

Ester Ethyl Hexyl Nonyl Octyl 1-Methyl 1-Methyl Myrtenyl Trans-pinocarvyl Hexyl Hexyl Methyl Ethyl Methyl Ethyl Decyl Methyl Ethyl Octyl Methyl Ethyl 1-Methyl 3-Methyl Methyl Ethyl 2-Hexen-1-ol, Table Concentrations

J. Dong et al. / Scientia Horticulturae 150 (2013) 47–53 51

Table 3

Odor threshold, average odor value, and odor value range (in parentheses) of 8 predominant esters found in F. ananassa and F. vesca.

−1

Ester Odor threshold (mg kg ) Odor value

F. × ananassa F. vesca

Ethyl acetate 0.905 15.3 (0–53.2) 16.5 (0–50.6)

Hexyl acetate 0.002 3615 (1125–9330) 1140 (0–2510)

Methyl butanoate 0.005 3324 (502–10,186) 136 (0–810)

Ethyl butanoate 0.00001 1,367,000 (0–5,073,000) 124,000 (0–212,000)

Hexyl butanoate 0.25 25.6 (1.7–56.4) 0.3 (0–1.8)

Methyl hexanoate 0.087 229.7 (52.9–477.4) 0

Ethyl hexanoate 0.0003 163266.7 (22733.3–483,600) 18700 (0–59733.3)

Hexyl hexanoate 64 0.006 (0.0008–0.02) 0.001 (0–0.004)

Larsen and Poll (1992).

Flath et al. (1967).

Schieberle and Hofmann (1997).

Echeverrá et al. (2004).

Takeoka et al. (1992).

may explain part of the differences in overall aroma. We also gardenia or rose (Table 6). F. vesca is characterized by an intense

found that the distribution of esters was more consistent in ﬂowery smell (Ulrich et al., 2007). In the absence of methyl

F. × ananassa than in the accessions of F. vesca, which may be anthranilate, these predominant esters may contribute to the ﬂo-

related to the narrow germplasm base of the cultivated straw- ral notes perceived in F. vesca. In contrast, most of the predominant

berry (Stegmeir et al., 2010). In addition, methyl anthranilate is esters of F. ananassa were described as having only fruity odor

found to be abundant in F. vesca (Olbricht et al., 2008), although resembling pineapple apple, banana, orange, pear or grape. Marked

we did not detect it in any of the accessions, possibly due to differences such as these may contribute to the variations in fruit

differences in the genotypes analyzed and their geographical aroma.

origin. Our results show that F. ananassa and F. vesca differ quali-

The contribution of a given compound to the aroma depends on tatively and quantitatively in their ester compositions. Previous

its odor value. The higher the odor value, the more important the studies reported that both the concentrations and the relative

compound is for the aroma (Zabetakis and Holden, 1997). In this proportions of volatile compounds have an effect on aroma pat-

study, it was indicated that not one individual ester but several terns. It is thought that different concentrations and ratios of key

esters were important contributors to the aroma of strawberries. It aroma compounds result in different fruit ﬂavors (Zabetakis and

appears that the major odorants have a collective effect on straw- Holden, 1997). Speirs et al. (1998) increased hexanol and (Z)-3-

berry aroma. Minor esters may have an inﬂuence on background hexenol levels by elevating ADH activity in tomato, and found that

odor. However, we could not ﬁnd odor threshold values in the lit- this changed tomato ﬂavor. Wang et al. (2011) found that high-

erature for octyl acetate, decyl acetate, myrtenyl acetate, methyl ﬂavor kiwifruit had a higher proportion of acetate esters and a

dodecanoate, or ethyl dodecanoate, which were detected only in F. lower proportion of butanoate esters than low-ﬂavor kiwifruit. In

vesca or were found at higher concentrations in this species than in the present study, the proportion of acetate esters was higher in

F. × ananassa. It is not known whether these compounds are impor- F. vesca than in F. × ananassa. This may explain why F. vesca has

tant odorants for F. vesca. a more pronounced ‘ﬂoral’ aroma in comparison with cultivated

Most of the predominant esters of F. vesca had not only fruity strawberries.

notes but also noticeable ﬂoral odors resembling neroli, jasmine,

Table 4

Number of esters containing the corresponding acyl and alkyl fractions in accessions of F. × ananassa and F. vesca.

Sources Acyl fractions Alkyl fractions

Acetate Butanoate Hexanoate Octanoate Decanoate Methyl Ethyl Hexyl Octyl 1-Methyl tridecyl Myrtenyl

F. × ananassa

Harunoka 6 3 6 2 1 6 3 4 0 0 0

Kunouwase 9 9 5 3 2 5 7 5 3 0 0

Benihoppe 9 5 4 2 1 5 7 3 2 0 0

Hokowase 4 8 6 2 1 3 4 6 0 0 0

Kitanokagayaki 11 9 6 2 1 6 6 3 5 0 0

Toyonoka 6 6 8 2 2 4 4 4 6 0 0

Sachinoka 7 10 9 2 2 5 6 3 1 0 0

Mean ± SE 7.4 ± 0.9a 7.1 ± 1.0A 6.3 ± 0.6A 2.1 ± 0.1A 1.4 ± 0.2a 4.9 ± 0.4A 5.3 ± 0.6a 4.0 ± 0.4A 2.4 ± 0.9a 0.0 ± 0.0B 0.0 ± 0.0B

F. vesca

UC4 5 1 1 1 0 0 3 2 1 0 0

UC5 8 5 5 1 3 3 5 3 4 1 1

Jinchuan 11 2 1 1 2 3 6 1 1 1 1

Maoxian 5 0 0 0 1 2 0 0 1 0 1

Northeast Wild 11 2 2 2 1 3 5 2 1 2 1

Fifteen Kuang 17 1 1 1 0 2 5 1 1 1 1

Mean SE 9.5 ± 1.9a 1.8 ± 0.7B 1.7 ± 0.7B 1.0 ± 0.3B 1.2 ± 0.5a 2.2 ± 0.5B 4.0 ± 0.9a 1.5 ± 0.4B 1.5 ± 0.5a 0.8 ± 0.3A 0.8 ± 0.2A

Means in the same column followed by different lowercase letters are signiﬁcantly different at P < 0.05 between F. × ananassa and F. vesca, while means followed by

different uppercase letters are signiﬁcantly different at P < 0.01.

52 J. Dong et al. / Scientia Horticulturae 150 (2013) 47–53

Table 6

0.01. Odor description of 21 predominant esters found in F. ananassa and F. vesca.

13.56a 0.00b

Ester Odor description at ± ±

a,b

Ethyl acetate Fruity, brandy, pineapple-like 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.72 8.78 b,c

Myrtenyl 14.56 85.18 45.15 26.07 Hexyl acetate Apple, cherry, pear, ﬂoral, sweetish

different Octyl acetate Neroli, jasmine, fruity

Nonyl acetate Floral, mushroom, gardenia

a Decyl acetate Floral, orange, rose-like

b,c

2-Hexen-1-ol, acetate Pleasant, fruity, green tridecyl

Myrtenyl acetate Herbaceous, pleasant, fresh, sweet, woody, 11.40 0.00b

signiﬁcantly

b,c ± ±

minty

are

Methyl butanoate Fruity, apple, banana, pineapple, ester-like, 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8.14 b,c 50.25 1-Methyl 64.83 11.52 22.46 green

b,c

Ethyl butanoate Fruity, sweet, pineapple letters

a,b

Hexyl butanoate Fruity, apricot

Octyl butanoate Herbaceous, green, orange, parsley, melon 3.45a 3.02a

b,c

Methyl hexanoate Fruity, ether-like, pineapple ± ±

b,c

Ethyl hexanoate Fruity, pineapple, banana, green apple, winy uppercase

0.00 0.00 1.88 1.50 7.62 3.49 1.99 2.23 1.80 2.86 5.49 Hexyl hexanoate Herbaceous 10.28 20.55

Octyl 21.79 17.91 b

1-Methyl ethyl hexanoate Sweet, fruity, pineapple

3-Methyl butyl hexanoate Fruity, apple, pineapple, green, sweet

different

Methyl octanoate Winy, fruity, orange by

a,b

4.66a 0.48b Ethyl octanoate Pleasant, fruity, ﬂoral, wine-apricot

± ±

Ethyl decanoate Fruity, grape, oily, brandy

Methyl dodecanoate Floral, fatty, wine 0.43 0.00 0.65 4.62 7.44 1.19 9.82 5.47 8.96 3.30 1.64 1.17 1.20

followed b 10.78 Hexyl 37.94

Ethyl dodecanoate Floral, fruity

Surburg and Panten (2006).

means b

Burcock (2010).

Olbricht et al. (2008). 5.26a 10.70a

while

± ±

, esters.

0.00 6.10 8.84 vesca total Ethyl 26.78 45.63 31.34 33.20 48.07 36.65 32.54 73.76 17.55 13.52 19.99 22.28

F. %

5. Conclusion

and

Large differences in fruit volatile esters were found between 9.75a 1.38b

± ±

fractions

F. ananassa and F. vesca. The predominant esters and their con- expressed ananassa

, centrations, proportions, odor descriptions and contributions to the 0.00 3.26 9.60 3.51 6.89 6.45 4.95 ×

20.44 10.81 Alkyl Methyl 83.24 43.24 17.05 14.87 18.81 29.78

aroma varied between the two species. It is suggested that these vesca

F. factors have a collective inﬂuence on fruit aroma. This is likely to

be a key reason for the different aroma patterns of strawberries. and

1.24a 2.39a between

± ±

0.05

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