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Aroma profiles of pineapple fruit (Ananas comosus [L.] Merr.) and pineapple products
ARTICLE IN PRESS
LWT 38 (2005) 263–274 www.elsevier.com/locate/lwt
Aroma profiles of pineapple fruit (Ananas comosus [L.] Merr.) and pineapple products S. Elss, C. Preston, C. Hertzig, F. Heckel, E. Richling, P. Schreier Lehrstuhl fu¨r Lebensmittelchemie, Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany Received 9 December 2003; received in revised form 25 May 2004; accepted 20 July 2004
Abstract The flavour profile of juices made from fresh-cut pineapple fruits (n ¼ 19; Costa Rica, Ghana, Honduras, Ivory Coast, Philippines, La Re´union, South Africa, Thailand) was studied in comparison to that of commercial water phases/recovery aromas (n ¼ 16), juice concentrates (n ¼ 10) as well as commercially available juices (n ¼ 17). In addition, pineapple jams (n ¼ 6; market samples) were investigated. HRGC-MS analysis of juices made from fresh-cut fruit revealed the known prevalence of esters, with methyl 2-methylbutanoate, methyl 3-(methylthio)-propanoate, methyl butanoate, methyl hexanoate, ethyl hexanoate and ethyl 3(methylthio)-propanoate, as well as 2,5-dimethyl-4-methoxy-3(2H)-furanone (mesifurane) and 2,5-dimethyl-4-hydroxy-3(2H)furanone (furaneol) as major constituents. A corresponding flavour profile was rarely found in water phases/recovery aromas under study. In most cases, the characteristic methyl esters and hydroxy or acetoxy esters were lacking completely or appeared only in minor amounts in these products. Whereas a few of the commercial single strength juices revealed fruit-related flavour profiles, juices produced from concentrates mostly exhibited a flavour composition similar to that of concentrates, i.e. they were predominantly determined by their contents of furaneol and did not show the fruit-related ester distribution. Similarly, the jams under study were poor in typical pineapple constituents. r 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Keywords: Ananas comosus; Aroma profile; HRGC-MS; Methyl esters; Furaneol; Mesifurane; Pineapple; Volatile compounds
1. Introduction Native to Central and South America, pineapples (Ananas comosus [L.] Merr.) grow in several tropical countries such as Hawaii, India, Malaysia, the Philippines and Thailand. Pineapple varieties are plentiful, but only a few leading types are sold commercially. The large, firm ‘Smooth Cayenne’ variety, grown in Thailand and the Philippines as well as in the Hawaiian islands, is perhaps the most commonly available. ‘Queen’ pineapples, mainly produced in South America and Australia, are smaller, a little drier and less sweet than the ‘Smooth Cayenne’. The medium-sized ‘Red Spanish’ pineapples, grown in the Caribbean, have purple-hued Corresponding author. Tel.: +49-931-888-5481; fax: +49-931-8885484. E-mail address: [email protected] (P. Schreier).
skin and light yellow flesh. Among the other varieties found at the market are the medium-sized ‘Pernambuco’, the large, heavy ‘Sugarloaf’, the white-fleshed ‘Variegated’, and the very sweet ‘Baby’. In Europa, in addition, a variety called ‘MD2’ (‘Extra Sweet’ or ‘Golden Ripe’) is sold as fresh fruit (Ti, 2000; Bartholomew, Pauli, & Rohrbach, 2003). Pineapple juice is a byproduct in the course of the production of canned pineapples. The out-flowing juice, the pulp from the peel and the pineapple core are the starting materials for the juice production. These pineapple parts are squeezed with the help of mills and screw-presses resulting in so-called single strength juice after pasteurization (Askar & Treptow, 2001). However, the majority of commercial pineapple juice is made from concentrate. Usually, thermal concentration is employed resulting in the flavourless concentrate and the flavour containing aqueous water phase. The volatiles from the
0023-6438/$30.00 r 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2004.07.014
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latter can be further enriched by techniques common in flavour technology leading to pineapple recovery aroma. In order to reconstitute the juice, legislation requires to combine concentrate and recovery aroma under dilution with water. From previous studies carried out on pineapple flavour (Takeoka et al., 1989; Engel, Heidlas, & Tressl, 1990; Takeoka, Buttery, Teranishi, Flath, & Guentert, 1991; Wu, Kuo, Hartman, Rosen, & Ho, 1991; Umano, Hagi, Nakahara, Shoji, & Shibamoto, 1992; Spanier et al., 1998; Teai, Claude-Lafontaine, Schippa, & Cozzolino, 2001) information about its composition and the contribution of several constituents to the overallflavour was provided. In addition, the sensitivity of the genuine pineapple fruit flavour, which can be easily modified in the course of fruit processing, i.e. from the post-harvest storage until thermal procedures, is wellknown. However, detailed information is still lacking; thus, we came back to pineapple flavour with the following aims, i.e. (i) to elaborate the variations in the aroma profile of pineapple fruits originating from various cultivars and regions, and (ii) to compare the aroma profile of fresh fruit with that of commercial pineapple products, i.e. juices and jams. Novel information about d13C and d2H isotope data of pineapple volatiles has already been provided elsewhere (Preston et al., 2003).
2. Materials and methods 2.1. Chemicals All chemicals used were of analytical grade. Solvents were distilled before use. Authentic reference aroma compounds were available from our laboratory collection.
2.3. Sample preparation Sample preparation was carried out within 1–2 days storage (25 1C) after the arrival of pineapple fruits. After peeling, slicing and homogenizing, the pulp was centrifuged (3000g) to deliver the juice (average yield, 70%). Separation of the volatiles was achieved, as also done with the commercial juices, by continuous liquid–liquid extraction (LLE; 48 h, 30 1C) using pentane–dichloromethane mixture (2+1, v/v). Juice concentrates and jams as well as water phases/recovery aromas were diluted with distilled water (1:4 and 1:40, respectively) before LLE. The extracts were dried over anhydrous sodium sulphate, filtered, and carefully concentrated to 1 ml using a Vigreux column (45 1C). As external standard 2methyl-1-pentanol was used. 2.4. Capillary gas chromatography-mass spectrometry (HRGC-MS) An HP Agilent 6890 Series gas chromatograph with split injection (220 1C; 1:20) was directly coupled to an HP Agilent 5973 Network mass spectrometer. The volatiles were separated on a J & W DB-Wax fused silica capillary column (30 m 0.25 mm i.d., df=0.25 mm). The temperature program was 3 min isothermal at 50 1C, then 50–240 1C at 4 1C/min. The temperatures of the injector and the connection parts was 220 1C. Electron impact mode at 70 eV was used. Identifications were carried out by comparison of mass spectral and chromatographic retention data of the target compounds with that of authentic reference substances. Standard controlled relative quantification was performed by double determinations using extraction/response factors F ¼ 1:0:
3. Results and discussion 2.2. Samples Various cultivars of pineapple fruit (n ¼ 19) from different regions (Costa Rica, Ghana, Honduras, Ivory Coast, Philippines, La Re´union, South Africa, Thailand) were purchased from the fruit market and were kindly provided from fruit companies. Commercial pineapple single strength juices (n ¼ 6) and juices made from concentrate (n ¼ 11) as well as commercial pineapple jams (n ¼ 6), all from German producers, were purchased from local supermarkets. Pineapple juice concentrates (n ¼ 10); water phases/recovery aromas (n ¼ 8) and pineapple aromas (n ¼ 8) were obtained from flavour houses and the Schutzgemeinschaft der Fruchtsaftindustrie e.V. (SGF), Nieder-Olm, Germany.
HRGC-MS analysis of fresh pineapple fruit volatiles revealed more than 130 constituents (Fig. 1a); most of them are listed, together with the ranges of their amounts and the corresponding mean values, in Table 1. The qualitative pineapple fruit flavour profile obtained in our present study agreed with previous information already provided by others, such as, e.g. Engel et al. (1990), who have reported several methyl esters and some characteristic sulphur-containing esters, various hydroxy esters and their corresponding acetoxy esters, as well as a number of lactones being responsible for the typical pineapple flavour profile. Quantitatively, however, the pineapple cultivars under study showed an extremely wide range of variations in their amounts of volatiles (Table 1). We found methyl 2-methylbutanoate (7; 0.16–6.0 mg/l), methyl 3-(methylthio)-propanoate
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Fig. 1. Total ion chromatograms (TIC) of pineapple volatiles in representative examples of (a) juice self-made from fresh-cut fruit; (b) commercial waterphase; and (c) commercial concentrate. The peak numbers correspond to that given in Tables 1–3.
Table 1 Aroma compounds identified by HRGC-MS in juices self-made from fresh-cut pineapple cultivars from various regions (n ¼ 19) Peak no.
Aroma compound
Range (mg/l)
Mean (mg/l)
1
Ethyl propanoate Ethyl methylpropanoate Propyl acetate Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Ethyl butanoate Ethyl 2-methylbutanoate Ethyl 3-methylbutanoate Butyl acetate 2-Methyl-1-propanol Methyl pentanoate 3-Pentanol
0–130 0–30 0–3500 10–1800 0–130 160–6000 0–5 0–480 0–1050 0–500 0–10 0–20 0–80 0–5
25 5 350 490 15 1500 1 100 190 30 2 2 25 1
5 6 7 10 11 12 15
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266 Table 1 (continued ) Peak no.
19 21 22 23 24 27 29 30
32 33 34 35 36
39 40 42 43 44 47 48 49 50 53 56 58 60 63 65 66 68 69
73 75 77 78 79
83 85 86 89 91
Aroma compound Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate Ethyl pentanoate Methyl hexanoate Limonene 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol Z-Ocimene 3-Methyl-2-buten-1-yl acetate Methyl Z-3-hexenoate Methyl E-3-hexenoate Hexyl acetate 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard Ethyl 2-hydroxy-2-methylbutanoate Ethyl E-3-hexenoate Methyl 2-hydroxypropanoate 3-Methyl-2-buten-1-ol Ethyl heptanoate Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal Methyl (methylthio)acetate Methyl Z-3-octenoate Ethyl octanoate Ethyl (methylthio)acetate Methyl E-3-octenoate Methyl 3-hydroxybutanoate Ethyl Z-3-octenoate Dimethyl malonate Methyl 3-(methylthio)-propanoate Methyl 3-acetoxybutanoate Ethyl 3-(methylthio)-propanoate Ethyl 3-acetoxybutanoate 2,5-Dimethyl-4-methoxy-3(2H)furanone Dimethyl succinate Methyl decanaote g-Butyrolactone Methyl benzoate 3-(Methylthio)propyl acetate Methyl Z-4-decenoate Methyl 3-hydroxyhexanoate Ethyl decanoate Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate 3-(Methylthio)-1-propanol Ethyl 5-oxohexanoate Ethyl 3-acetoxyhexanoate Ethyl phenylacetate d-Hexalactone Methyl 5-acetoxyhexanoate g-Heptalactone Ethyl 5-acetoxyhexanoate Methyl 5-hydroxyhexanoate d-Heptalactone
Range (mg/l) 0–60 0–15 0–620 0–45 15–3800 0–5 0–380 0–3500 0–10 0–3 t t t t 0–3 0–18 t 0–3 0–95 t t 0–15 0–2 0–5 0–80 0–5 0–230 0–200 0–120 0–80 0–450 0–10 0–10 0–50 0–80 15–1200 40–7100 0–380 15–2700 0–55 20–9200 0–10 0–20 0–700 0–5 0–40 0–60 1–570 0–50 0–460 0–3600 0–1500 0–95 0–10 0–340 0–5 0–1500 15–1700 0–130 0–320 0–200 0–60
Mean (mg/l) 10 2 70 10 1300 1 40 500 2 t t t t t 1 5 t t 15 t t 2 t 1 10 1 50 10 15 15 40 1 1 20 10 380 1500 120 470 5 1500 2 1 100 1 5 5 205 5 75 715 460 10 1 60 1 250 700 15 55 50 5
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Table 1 (continued ) Peak no.
Aroma compound
93 94
Methyl 3-hydroxyoctanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate d-Octalactone 2,5-Dimethyl-4-hydroxy-3(2H)furanone Ethyl 5-acetoxyoctanoate g-Decalactone d-Decalactone 4-Vinylguaiacol Solerone g-Dodecalactone d-Dodecalactone
96 97 102 103 104 105
Range (mg/l) 0–30 0–410 0–80 0–400 0–780 5–4700 0–15 0–20 0–160 0–30 0–80 0–60 0–52
Mean (mg/l) 5 90 5 60 100 960 2 4 15 5 20 10 6
t=trace o1 mg/l. For each component ranges of amounts and mean values are given.
Table 2 Aroma compounds identified by HRGC-MS in commercial pineapple water phases/recovery aromas (n ¼ 8) Peak no.
4 5 7 9 10 11
13 14 17 19
22 24 25 27 29
32 33 35
Aroma compound Ethyl propanoate Ethyl methylpropanoate Propyl acetate 2,3-Butandione Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Methyl 3-methylbutanoate Ethyl butanoate Ethyl 2-methylbutanoate Ethyl 3-methylbutanoate Butyl acetate Hexanal 2-Methyl-1-propanol Methyl pentanoate Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate 1-Butanol Ethyl pentanoate 1-Penten-3-ol Ethyl 2-butenoate 1,4-Cineol 2-Heptanone Methyl hexanoate Limonene 2-/3-Methyl-1-butanol E-2-Hexenal Ethyl hexanoate 1-Pentanol Z-Ocimene 3-Methyl-2-buten-1-yl acetate Methyl Z-3-hexenoate Methyl E-3-hexenoate Hexyl acetate 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard
Range (mg/l) 0–3.5 0–1.5 0–9.0 0–40 0–72 0–0.1 0–610 0–11.5 0–3.0 0–109 0–300 0–1.0 0–0.2 0–0.1 0–400 0–0.4 0–23 0–0.8 0–240 0–0.4 0–0.4 0–0.6 0–12 0–0.5 0–0.04 0–1730 0–12 0–95 0–0.8 0–1110 0–0.05 0–2.9 0–0.4 0–0.35 0–0.5 0–0.03 0–2.9 0–18 0–0.04
Mean (mg/l) 0.70 0.25 1.5 6 12 0.01 85 1.9 0.50 17 45 0.16 0.03 0.02 57 0.1 3.3 0.1 32 0.1 0.14 0.08 1.6 0.06 0.005 220 1.7 21 0.1 145 0.005 0.4 0.1 0.08 0.12 0.005 1.1 4.2 0.005
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268 Table 2 (continued ) Peak no.
Aroma compound
Range (mg/l)
Mean (mg/l)
36 37
Ethyl 2-hydroxy-2-methylbutanoate Ethyl E-3-hexenoate Methyl 2-hydroxypropanoate 3-Methyl-2-buten-1-ol Ethyl heptanoate Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal Methyl 2-hydroxy-3-methylbutanoate Methyl (methylthio)acetate E-2-Hexen-1-ol Ethyl 2-hydroxy-3-methylbutanoate Methyl Z-3-octenoate Ethyl octanoate Ethyl (methylthio)acetate Furfural Acetic acid Methyl 3-hydroxybutanoate Ethyl Z-3-octenoate 1-Decanol Decanal Methyl 2-octenoate Dimethyl malonate Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butandiol Methyl 3-acetoxybutanoate Linalool Ethyl 3-(methylthio)-propanoate Ethyl 3-acetoxybutanoate 2,5-Dimethyl-4-methoxy-3(2H)furanone 4-Terpinenol Dimethyl succinate Ethyl 2-hydroxyhexanoate g-Butyrolactone 3-(Methylthio)propyl acetate Methyl Z-4-decenoate Methyl 3-hydroxyhexanoate Ethyl decanoate Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate a-Terpineol 3-(Methylthio)-1-propanol Ethyl 5-oxohexanoate Ethyl 3-acetoxyhexanoate Ethyl phenylacetate d-Hexalactone Methyl 5-acetoxyhexanoate g-Heptalactone Ethyl 5-acetoxyhexanoate 2-Phenylethyl acetate Methyl 5-hydroxyhexanoate p-Cymen-8-ol Geraniol Methyl 3-hydroxyoctanoate Ethyl 3-hydroxyoctanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate
0–2.5 0–95 0–0.1 0–0.25 0–15 0–1.5 0–1.4 0–1.7 0–2.7 0–77 0–0.7 0–0.01 0–1.1 0–0–05 0–0.5 0–30 0–107 0–1.5 0–1.2 0–2.2 0–0–6 0–34 0–0.45 0–0.1 0–0.6 0–25 0–0.1 1–750 0–2.2 0–14 0–0.28 0.5–700 0–17 0–58 0–0.5 0–10 0–0.08 0–0.36 0–21 0–9.6 0–27 0–18 0–7.1 0–74 0–18 0–0.5 0–1.4 0–2.5 0–5.9 0–0.16 0–4.3 0–6.9 0–6.2 0–13 0–270 0–6.9 0–0.12 0–0.9 0–3.1 0–0.05 0–49 0–1.9 0–3.0
0.4 12 0.01 0.06 1.8 0.24 0.26 0.24 0.6 10 0.1 0.005 0.2 0.005 0.1 3.8 13.5 0.3 0.16 0.4 0.11 4.3 0.06 0.02 0.09 3.4 0.01 112 0.3 2.1 0.07 109 2.2 10 0.17 2 0.01 0.05 2.8 1.4 5.1 2.3 2.1 9.9 7.8 0.11 0.25 0.36 2.4 0.03 0.6 2.2 0.9 2.4 34 1.0 0.02 0.14 0.45 0.01 6.4 0.3 0.44
40 41 42 43 45 47
50
53
56 58 60 63 66 67
73 75 77 78 79 81 82 83 85 86 88 89 91
93 94 96
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Table 2 (continued ) Peak no.
Aroma compound
97 102
d-Octalactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone Ethyl 5-acetoxyoctanoate Ethyl cinnamate g-Decalactone d-Decalactone g-Dodecalactone d-Dodecalactone
103 105
Range (mg/l) 0–0.02 0–7.5 0–0.13 0–0.06 0–5.9 0–0.04 0–5.6 0–0.03
Mean (mg/l) 0.005 1.1 0.02 0.01 0.78 0.007 0.7 0.004
For each component ranges of amounts and mean values are given.
Table 3 Aroma compounds identified by HRGC-MS in commercial pineapple concentrates (n ¼ 10) Peak no.
32 35
45 46 51 52
54 55 57 58
64 69 74 76 78 81 84 85
Aroma compound 3-Methyl-2-butanone 2-Pentanone 2-Methyl-3-butene-2-ol Hexanal 2-Methyl-1-propanol 3-Pentanol 2-Pentanol 1-Butanol Methyl hexanoate Limonene 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol 3-Hydroxy-2-butanone Standard 3-Methyl-2-buten-1-ol 1-Hexanol 6-Methyl-5-hepten-2-one Z-3-Hexen-1-ol Nonanal 2-Methyl-2(3H)-furanone E-Linalooloxid 3-(Methylthio)-propanal Furfural Z-Linalooloxid Acetic acid Methyl 3-hydroxybutanoate 2,5-Dimethyl-3(2H)-furanone 2-Furylmethylketone Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butanediol Linalool 5-Methylfurfural g-Butyrolactone Phenylacetaldehyde Methyl 3-hydroxyhexanoate Furfurylalcohol g-Hexalactone Methyl 3-acetoxyhexanoate 3-(Methylthio)-1-propanol Methyl nicotinate d-Hexalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate
Range (mg/kg) 0–250 0–45 0–5 0–25 0–270 0–20 0–75 0–10 0–15 0–25 0–430 0–10 0–90 0–140 0–50 0–10 0–25 0–5 0–50 0–25 0–150 10–170 50–6500 0–60 0–2000 0–20 0–1500 0–120 0–50 0–200 0–200 0–30 0–200 0–250 3–400 0–50 0–60 0–260 0–230 0–130 0–40 0–340 0–40 0–400
Mean (mg/kg) 25 5 1 4 30 2 10 2 1 3 50 1 9 40 8 1 4 1 10 10 30 90 2500 20 350 2 400 35 15 40 30 6 50 60 230 10 25 40 30 15 10 40 7 60
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270 Table 3 (continued ) Peak no.
98
102 104
106 107
Aroma compound d-Octalactone Maltol 3-Hydroxy-(2H)-pyran-2-one Pantolactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone 4-Vinylguaiacol Solerone Solerol 4-Vinylphenol 5-(Hydroxymethyl) furfural
Range (mg/kg) 0–2 0–25 0–80 0–180 0–13500 0–1200 0–600 0–260 0–640 0–350
Mean (mg/kg) 1 5 15 40 1600 450 60 30 150 70
For each component ranges of amounts and mean values are given.
Fig. 2. Total ion chromatograms (TIC) of pineapple volatiles in representative examples of (a) commercial single strength juice; (b), (c) commercial juices made from concentrate. The peak numbers correspond to that given in Table 4.
(58; 0.04–7.1 mg/l), 2,5-dimethyl-4-methoxy-3(2H)-furanone (66, mesifurane; 0.02–9.2 mg/l), and 2,5-dimethyl4-hydoxy-3(2H)-furanone (102, furaneol, 0.005–4.7 mg/l)
as the major compounds of pineapple fruits. Amounts of 41 mg/l were also reached by methyl butanoate (5, 0.01–1.8 mg/l), methyl hexanoate (22, 0.015–3.8 mg/l),
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Table 4 Aroma compounds identified by HRGC-MS in commercial pineapple single strength juices (A; n ¼ 6) and pineapple juices made from concentrates (B; n ¼ 11) Peak no.
Aroma compound
A (mg/l) Range
3 4 5 6 7 8 10 11
14 15
19 20 22 23 24 27
32 33 35 38 40 41 42 44 45 46 47 51 52 53 54 55 56 57 58 59 60 63 65
69 71
Ethyl propanoate 3-Methyl-2-butanone 2-Pentanone Propyl acetate 2,3-Butanedione Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Ethyl butanoate Ethyl 2-methylbutanoate Butyl acetate Hexanal 2-Methyl-1-propanol Methyl pentanoate Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate 1-Butanol b-Myrcene Methyl hexanoate Limonene 1,8-Cineol 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol p-Cymene 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard Ethyl 2-hydroxy-2-methylbutanoate 3-Methyl-2-buten-1-ol Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal 2-Methyl-3(2H)-furanone Methyl (methylthio)acetate 3-(Methylthio)-propanal Furfural Acetic acid Methyl 3-hydroxybutanoate 2,5-Dimethyl-3(2H)-furanone 2-Furylmethylketone Dimethyl malonate Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butanediol Methyl 3-acetoxybutanoate Ethyl 3-(methylthio)-propanoate 5-Methylfurfural Ethyl 3-acetoxybutanoate Linalool 2,5-Dimethyl-4-methoxy-3(2H)furanone g-Butyrolactone 3-(Methylthio)-propyl acetate
B (mg/l) Mean
Range
Mean
0–3 nd 0–20 0–700 0–30 0–250 0–160 0–800 0–18 0–90 0–80 t nd 4–10 0–10 0–3 0–5 0–12 0–7 nd 1–900 0–10 nd 20–100 0–80 0–2 nd 30–1800 0–100 nd
1 nd 3 170 10 60 30 180 4 30 25 t nd 10 2 1 2 6 4 nd 200 3 nd 50 25 1 nd 850 25 nd
0–1 0–7 0–6 nd 0–2 0–7 0–115 0–6 0–37 0–10 0–50 0–5 0–4 0–28 nd nd 0–3 0–6 0–13 0–2 0–15 0–135 0–6 0–150 0–9 0–1 0–44 8–230 0–3 0–3
1 1 1 nd 1 1 20 2 6 3 10 1 1 4 nd nd 1 3 4 1 3 35 1 18 2 t 4 60 t t
0–2 0–6 0–10 0–10 0–40 0–35 0–40 0–15 nd 0–50 2–50 20–2000 0–330 0–70 0–240 0–19 0–400 0–6 25–2200 0–130 0–100 0–400 nd 0–5 nd 0–400 0–200 0–4
1 3 3 4 10 10 8 3 nd 10 15 450 55 20 60 5 110 1 550 40 35 130 nd 2 nd 110 75 2
0–1 0–2 0–2 0–3 nd nd nd 0–1 0–18 nd 0–60 7–1300 0–340 0–3 4–750 0–33 0–4 0–5 1–29 0–500 0–4 0–50 0–35 nd 0–4 0–11 0–64 nd
t 1 t 1 nd nd nd t 2 nd 7 173 31 1 150 8 1 3 12 77 1 12 3 nd 1 1 33 nd
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272 Table 4 (continued ) Peak no.
Aroma compound
A (mg/l) Range
72 74 75 76 77 78 79 81 83 85 86 89 94 95 96 97 98 99 101 102 103 104 106 107
Butanoic acid Phenylacetaldehyde Methyl 3-hydroxyhexanoate Furfurylalcohol Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate a-Terpineol 3-(Methylthio)-1-propanol Ethyl 3-acetoxyhexanoate d-Hexalactone Methyl 5-acetoxyhexanoate Ethyl 5-acetoxyhexanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate d-Octalactone Maltole 3-Hydroxy-(2H)-pyran-2-one Pantolactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone g-Decalactone d-Decalactone 4-Vinylguaiacol g-Dodecalactone 4-Vinylphenol d-Dodecalactone 5-(Hydroxymethyl)furfural
0–20 0–170 0–110 0–28 0–50 0–870 0–110 nd 0–90 0–36 0–360 0–250 0–24 0–370 0–55 0–13 0–131 0–3 0–1700 0–34 0–3500 0–58 0–22 0–230 0–9 8–190 0–10 0–450
B (mg/l) Mean
Range
Mean
6 30 44 6 27 230 50 nd 26 13 80 86 14 70 38 5 31 t 330 7 1000 11 7 40 6 70 4 86
0–6 0–132 0–4 0–16 0–4 8–53 0–30 0–8 0–80 0–7 0–41 0–7 0–2 0–11 0–65 0–3 0–15 0–9 nd 0–93 0–1005 t nd 0–190 0–16 0–200 0–7 0–60
1 13 2 3 1 22 6 2 10 1 15 2 t 2 9 t 4 2 nd 22 305 t nd 17 7 30 2 24
t=trace o1 mg/l; nd=not detectable. For each component ranges of amounts and mean values are given.
ethyl hexanoate (27, 0–3.5 mg/l), ethyl 3-(methylthio)propanoate (63, 0.015–2.7 mg/l), g-hexalactone (78, 0–3.6 mg/l), d-hexalactone (85, 0–1.5 mg/l), and methyl 5-acetoxyhexanoate (86, 0.015–1.7 mg/l). Only a part, i.e. 20% of the water phases/recovery aromas under study contained a high number of the typical volatiles as found in the juices made from freshcut pineapple fruits. In comparison to the fruit flavour profile, however, also in these cases differences were obvious, as shown in the representative example of Fig. 1b. Methyl hexanoate (22, 0–1730 mg/l), ethyl hexanoate (27, 0–1110 mg/l), methyl-3-(methylthio)-propanoate (58, 1–750 mg/l) and ethyl 3-(methylthio)-propanoate (63, 0.5–700 mg/l) were observed as major constituents (Table 2). In most cases, the characteristic methyl esters and hydroxy or acetoxy esters were lacking completely or appeared only in minor amounts. There are many reasons which might be discussed to explain these findings: they mainly comprise the selection of inappropriate fruit varieties and flavour losses or modifications during post-harvest handling (Elss, Preston, Hertzig, Richling, & Schreier, 2003) or in the course of distillation and flavour recovery. However, as obviously a part of the producers is able to provide appropriate
qualities, the problem should be rather an economic than a technological one. As expected, the flavour profile of pineapple juice concentrates was determined by thermally formed compounds such as, e.g. furfural (52; 0.05–6.5 mg/kg) and 4-vinylguaiacol (104; 0.3–1.2 mg/kg), and nondistillable substances, as typically furaneol (102, 0–13.5 mg/kg) (Fig. 1c and Table 3). From these compounds enriched in the concentrates, furaneol determines their sensory character. Many years ago, its ‘pineapple-caramel’ note has led to its detection in pineapple and its structural elucidation (Rodin, Himel, Silverstein, Leeper, & Gortner, 1965; Willhalm, Stoll, & Thomas, 1965). In addition, the aroma profile of a number of commercial pineapple juices was analysed; they comprised both single strength juices and products made from concentrates. As representative examples, Fig. 2 shows the flavour profiles of a single strength juice (2a) and two samples of juices made from concentrate (2b and c). In Table 4 the identified constituents and their range of amounts determined in the samples under study are outlined. At a first glance, it is obvious that much less compounds were detectable and, quantitatively, also
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the amounts of aroma constituents comprised only a small part of that found in juices made from fresh-cut fruits (Table 1). The quantities (ranges and mean values) of selected pineapple volatiles as determined in juices from fresh-cut fruits and the two kinds of commercial juices are graphically compared in Fig. 3. Compared to the juices made from concentrates, the volatile profiles of the single strength juices match better with the genuine fruit profiles. As expected, they showed also some components caused by thermal treatment (pasteurization), such as, e.g. furfural (52), 3-hydroxy[2H]-pyran-2-one (99), pantolactone (101), furaneol (102) and 5-(hydroxymethyl)furfural (107). Surprisingly, their acetoin (32) content was rather high, i.e. surpassing approximately 10 times that of the juices made from concentrates (Table 4). In addition, in one case 2ethylhexanoic acid was detected as chemical contaminant in amounts of about 0.5 mg/l. Its teratogenic effects are known (Lampen, Zimnik, & Nau, 2003). The contamination is probably due to migration from the gasket of the metal lid (Elss, Gru¨newald, Richling, & Schreier, 2004). The flavour profile of the pineapple juices made from concentrates under study were mainly characterized by the profile found for concentrates. Similar to the juice concentrates, furaneol (102) and furfural (52) were found as major compounds in these products. None of the samples under study showed the characteristic genuine pineapple flavour composition or that of the waterphase/recovery aromas. Obviously, the typical ‘pineapple’-like aroma of furaneol (102) constitutes the sensorical acceptance of the products more or less lacking the pineapple fruit-typical flavour profile. In addition, juices made from concentrates showed small amounts of some terpenes, probably caused by contamination in the course of the industrial production chain. Thus, in a few samples terpenes such as 1,8cineol, p-cymene, b-myrcene, a-terpineol or linalool were found; none of them were observed in the juices made from fresh-cut fruits. Small amounts of limonene (up to 5 mg/l) were detectable in the fruits, but commercial juices from concentrates exhibited amounts of limonene up to 135 mg/l (mean 35 mg/l). Similar results as found for commercial juices made from concentrates were obtained for the pineapple jams under study (individual data not shown). Their profiles were determined by the Maillard reaction products furfural (0.08–0.6 mg/kg) and 5-(hydroxymethyl)furfural (0.02–1.6 mg/kg). Characteristic esters were lacking completely or appeared just in traces, furaneol and the pineapple lactones were found in low total amounts of p0.06 and p0.13 mg/kg, respectively. In conclusion, in spite of the limited number of samples and the restriction to the German market, the present studies stress (i) the high variability in the amounts of pineapple fruit volatiles depending on
273
7 11 22 27 58 63 66 69 75 77 78 79 83 85 94 97 102 0
500
1000
1500
2000
µg/L
Fig. 3. Comparison of the amounts (ranges and mean values, mg/l) of selected pineapple volatiles identified by HRGC-MS in juices self-made from fresh-cut fruits ( ), commercial single strength juices ( ), and commercial juices made from concentrates (&). The numbers correspond to that given in Tables 1 and 4. 7 Methyl 2-methylbutanoate 11 Ethyl 2-methylbutanoate 22 Methyl hexanoate 27 Ethyl hexanoate 58 Methyl 3-(methylthio)-propanoate 63 Ethyl 3(methylthio)-propanoate 66 Methoxyfuraneol 69 g-Butyrolactone 75 Methyl 3-hydroxyhexanoate 77 Ethyl 3-hydroxyhexanoate 78 gHexalactone 79 Methyl 3-acetoxyhexanoate 83 Ethyl 3-acetoxyhexanoate 85 d-Hexalactone 94 g-Octalactone 97 d-Octalactone 102 Furaneol.
the cultivar (origin), (ii) the problems of pineapple flavour stability during post-harvest handling, flavour recovery and fruit juice technology, as well as (iii), the
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need of product quality control to be intensified in future.
Acknowledgements The financial support kindly provided by the Forschungskreis der Erna¨hrungsindustrie e.V. (FEI), Bonn, the Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) and the Ministry of Economics and Labour (project no. 13203N) is gratefully acknowledged. Lena Gru¨newald is thanked for skilful technical support. References Askar, A., & Treptow, H., 2001. Verarbeitung von tropischen Fru¨chten. In: Schobinger, U. (Ed.), Frucht- und Gemu¨sesa¨fte (3. Aufl., pp. 242–245). Stuttgart: Ulmer. Bartholomew, D., Pauli, R. E., & Rohrbach, K. (2003). The pineapple. Botany, production and uses, Cambridge, MA, USA: CABI Publ. Engel, K. H., Heidlas, J., & Tressl, R. (1990). The flavor of tropical fruits (banana, melon, pineapple). In I. D. Morton, & A. J. MacLeod (Eds.), Developments in food science 3C (food flavours) (pp. 195–219). Amsterdam: Elsevier. Elss, S., Preston, C., Hertzig, C., Richling, E., & Schreier, P. (2003). U¨ber das Aromaprofil der Ananas (Ananas comosus [L.] Merr.) Eine Nachernte-Studie. Flu¨ssiges Obst, 70, 734–737. Elss, S., Gru¨newald, L., Richling, E., & Schreir, P. (2004). Occurrence of 2-ethylhexanoic acid in foods packed in glass jars. Food Additives and Contaminants, 21, 811–814. Lampen, A., Zimnik, S., & Nau, H. (2003). Teratogenic phthalate esters and metabolites activate the nuclear receptors PPARs and induce differentiation of F9 cells. Toxicology and Applied Pharmacology, 188, 14–23. Preston, C., Richling, E., Elss, S., Appel, M., Heckel, F., Hartlieb, A., & Schreier, P. (2003). On-line gas chromatography combustion/
pyrolysis isotope ratio mass spectrometry (HRGC-C/P-IRMS) of pineapple (Ananas comosus) volatiles. Journal of Agricultural and Food Chemistry, 51, 8027–8031. Rodin, J. O., Himel, C. M., Silverstein, R. M., Leeper, R. W., & Gortner, W. A. (1965). Volatile flavor and aroma components of pineapple. I. Isolation and tentative identification of 2,5-dimethyl4-hydroxy-3[2H]-furanone. Journal of Food Science, 30, 280–284. Spanier, A. M., Flores, M., James, C., Lasater, J., Lloyd, S., & Miller, J. A. (1998). Fresh-cut pineapple (Ananas sp.) flavor. Effect of storage. In E. T. Contis, C. T. Ho, C. J. Mussinan, T. H. Parliament, F. Shahidi, & A. M. Spanier (Eds.), Food flavors: formation, analysis and packaging influence, developments in food science, Vol. 40 (pp. 331–343). Amsterdam: Elsevier. Takeoka, G., Buttery, R. G., Flath, R. A., Teranishi, R., Wheeler, E. L., Wieczorek, R. L., & Guentert, M. (1989). Volatile constituents of pineapple (Ananas comosus [L.] Merr). In R. Teranishi, R. G. Buttery, & F. Shahidi (Eds.), Flavor chemistry. Trends and developments. ACS Symposium Series 388 (pp. 223–237). Washington: American Chemical Society. Takeoka, G., Buttery, R. G., Teranishi, R., Flath, R. A., & Guentert, M. (1991). Identification of additional pineapple volatiles. Journal of Agricultural and Food Chemistry, 39, 1848–1851. Teai, T., Claude-Lafontaine, A., Schippa, C., & Cozzolino, F. (2001). Volatile compounds in fresh pulp of pineapple (Ananas comosus [L.] Merr.) from French Polynesia. Journal of Essential Oil Research, 13, 4–318. Ti, T. C. (2000). The global pineapple economy FAO keynote address. Acta Horticulturae (ISHS), 529, 4–52. Umano, K., Hagi, Y., Nakahara, K., Shoji, A., & Shibamoto, T. (1992). Volatile constituents of green and ripened pineapple (Ananas comosus [L.] Merr.). Journal of Agricultural and Food Chemistry, 40, 599–603. Willhalm, B., Stoll, M., & Thomas, A. F. (1965). 2,5-Dimethyl-4hydroxy-2,3-dihydrofuran-3-one. Chemistry & Industry (London), 18, 1629–1630. Wu, P., Kuo, M. C., Hartman, T. G., Rosen, R. T., & Ho, C. T. (1991). Free and glycosidically bound aroma compounds in pineapple (Ananas comosus [L.] Merr.). Journal of Agricultural and Food Chemistry, 39, 170–172.
LWT 38 (2005) 263–274 www.elsevier.com/locate/lwt
Aroma profiles of pineapple fruit (Ananas comosus [L.] Merr.) and pineapple products S. Elss, C. Preston, C. Hertzig, F. Heckel, E. Richling, P. Schreier Lehrstuhl fu¨r Lebensmittelchemie, Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany Received 9 December 2003; received in revised form 25 May 2004; accepted 20 July 2004
Abstract The flavour profile of juices made from fresh-cut pineapple fruits (n ¼ 19; Costa Rica, Ghana, Honduras, Ivory Coast, Philippines, La Re´union, South Africa, Thailand) was studied in comparison to that of commercial water phases/recovery aromas (n ¼ 16), juice concentrates (n ¼ 10) as well as commercially available juices (n ¼ 17). In addition, pineapple jams (n ¼ 6; market samples) were investigated. HRGC-MS analysis of juices made from fresh-cut fruit revealed the known prevalence of esters, with methyl 2-methylbutanoate, methyl 3-(methylthio)-propanoate, methyl butanoate, methyl hexanoate, ethyl hexanoate and ethyl 3(methylthio)-propanoate, as well as 2,5-dimethyl-4-methoxy-3(2H)-furanone (mesifurane) and 2,5-dimethyl-4-hydroxy-3(2H)furanone (furaneol) as major constituents. A corresponding flavour profile was rarely found in water phases/recovery aromas under study. In most cases, the characteristic methyl esters and hydroxy or acetoxy esters were lacking completely or appeared only in minor amounts in these products. Whereas a few of the commercial single strength juices revealed fruit-related flavour profiles, juices produced from concentrates mostly exhibited a flavour composition similar to that of concentrates, i.e. they were predominantly determined by their contents of furaneol and did not show the fruit-related ester distribution. Similarly, the jams under study were poor in typical pineapple constituents. r 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Keywords: Ananas comosus; Aroma profile; HRGC-MS; Methyl esters; Furaneol; Mesifurane; Pineapple; Volatile compounds
1. Introduction Native to Central and South America, pineapples (Ananas comosus [L.] Merr.) grow in several tropical countries such as Hawaii, India, Malaysia, the Philippines and Thailand. Pineapple varieties are plentiful, but only a few leading types are sold commercially. The large, firm ‘Smooth Cayenne’ variety, grown in Thailand and the Philippines as well as in the Hawaiian islands, is perhaps the most commonly available. ‘Queen’ pineapples, mainly produced in South America and Australia, are smaller, a little drier and less sweet than the ‘Smooth Cayenne’. The medium-sized ‘Red Spanish’ pineapples, grown in the Caribbean, have purple-hued Corresponding author. Tel.: +49-931-888-5481; fax: +49-931-8885484. E-mail address: [email protected] (P. Schreier).
skin and light yellow flesh. Among the other varieties found at the market are the medium-sized ‘Pernambuco’, the large, heavy ‘Sugarloaf’, the white-fleshed ‘Variegated’, and the very sweet ‘Baby’. In Europa, in addition, a variety called ‘MD2’ (‘Extra Sweet’ or ‘Golden Ripe’) is sold as fresh fruit (Ti, 2000; Bartholomew, Pauli, & Rohrbach, 2003). Pineapple juice is a byproduct in the course of the production of canned pineapples. The out-flowing juice, the pulp from the peel and the pineapple core are the starting materials for the juice production. These pineapple parts are squeezed with the help of mills and screw-presses resulting in so-called single strength juice after pasteurization (Askar & Treptow, 2001). However, the majority of commercial pineapple juice is made from concentrate. Usually, thermal concentration is employed resulting in the flavourless concentrate and the flavour containing aqueous water phase. The volatiles from the
0023-6438/$30.00 r 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2004.07.014
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latter can be further enriched by techniques common in flavour technology leading to pineapple recovery aroma. In order to reconstitute the juice, legislation requires to combine concentrate and recovery aroma under dilution with water. From previous studies carried out on pineapple flavour (Takeoka et al., 1989; Engel, Heidlas, & Tressl, 1990; Takeoka, Buttery, Teranishi, Flath, & Guentert, 1991; Wu, Kuo, Hartman, Rosen, & Ho, 1991; Umano, Hagi, Nakahara, Shoji, & Shibamoto, 1992; Spanier et al., 1998; Teai, Claude-Lafontaine, Schippa, & Cozzolino, 2001) information about its composition and the contribution of several constituents to the overallflavour was provided. In addition, the sensitivity of the genuine pineapple fruit flavour, which can be easily modified in the course of fruit processing, i.e. from the post-harvest storage until thermal procedures, is wellknown. However, detailed information is still lacking; thus, we came back to pineapple flavour with the following aims, i.e. (i) to elaborate the variations in the aroma profile of pineapple fruits originating from various cultivars and regions, and (ii) to compare the aroma profile of fresh fruit with that of commercial pineapple products, i.e. juices and jams. Novel information about d13C and d2H isotope data of pineapple volatiles has already been provided elsewhere (Preston et al., 2003).
2. Materials and methods 2.1. Chemicals All chemicals used were of analytical grade. Solvents were distilled before use. Authentic reference aroma compounds were available from our laboratory collection.
2.3. Sample preparation Sample preparation was carried out within 1–2 days storage (25 1C) after the arrival of pineapple fruits. After peeling, slicing and homogenizing, the pulp was centrifuged (3000g) to deliver the juice (average yield, 70%). Separation of the volatiles was achieved, as also done with the commercial juices, by continuous liquid–liquid extraction (LLE; 48 h, 30 1C) using pentane–dichloromethane mixture (2+1, v/v). Juice concentrates and jams as well as water phases/recovery aromas were diluted with distilled water (1:4 and 1:40, respectively) before LLE. The extracts were dried over anhydrous sodium sulphate, filtered, and carefully concentrated to 1 ml using a Vigreux column (45 1C). As external standard 2methyl-1-pentanol was used. 2.4. Capillary gas chromatography-mass spectrometry (HRGC-MS) An HP Agilent 6890 Series gas chromatograph with split injection (220 1C; 1:20) was directly coupled to an HP Agilent 5973 Network mass spectrometer. The volatiles were separated on a J & W DB-Wax fused silica capillary column (30 m 0.25 mm i.d., df=0.25 mm). The temperature program was 3 min isothermal at 50 1C, then 50–240 1C at 4 1C/min. The temperatures of the injector and the connection parts was 220 1C. Electron impact mode at 70 eV was used. Identifications were carried out by comparison of mass spectral and chromatographic retention data of the target compounds with that of authentic reference substances. Standard controlled relative quantification was performed by double determinations using extraction/response factors F ¼ 1:0:
3. Results and discussion 2.2. Samples Various cultivars of pineapple fruit (n ¼ 19) from different regions (Costa Rica, Ghana, Honduras, Ivory Coast, Philippines, La Re´union, South Africa, Thailand) were purchased from the fruit market and were kindly provided from fruit companies. Commercial pineapple single strength juices (n ¼ 6) and juices made from concentrate (n ¼ 11) as well as commercial pineapple jams (n ¼ 6), all from German producers, were purchased from local supermarkets. Pineapple juice concentrates (n ¼ 10); water phases/recovery aromas (n ¼ 8) and pineapple aromas (n ¼ 8) were obtained from flavour houses and the Schutzgemeinschaft der Fruchtsaftindustrie e.V. (SGF), Nieder-Olm, Germany.
HRGC-MS analysis of fresh pineapple fruit volatiles revealed more than 130 constituents (Fig. 1a); most of them are listed, together with the ranges of their amounts and the corresponding mean values, in Table 1. The qualitative pineapple fruit flavour profile obtained in our present study agreed with previous information already provided by others, such as, e.g. Engel et al. (1990), who have reported several methyl esters and some characteristic sulphur-containing esters, various hydroxy esters and their corresponding acetoxy esters, as well as a number of lactones being responsible for the typical pineapple flavour profile. Quantitatively, however, the pineapple cultivars under study showed an extremely wide range of variations in their amounts of volatiles (Table 1). We found methyl 2-methylbutanoate (7; 0.16–6.0 mg/l), methyl 3-(methylthio)-propanoate
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265
Fig. 1. Total ion chromatograms (TIC) of pineapple volatiles in representative examples of (a) juice self-made from fresh-cut fruit; (b) commercial waterphase; and (c) commercial concentrate. The peak numbers correspond to that given in Tables 1–3.
Table 1 Aroma compounds identified by HRGC-MS in juices self-made from fresh-cut pineapple cultivars from various regions (n ¼ 19) Peak no.
Aroma compound
Range (mg/l)
Mean (mg/l)
1
Ethyl propanoate Ethyl methylpropanoate Propyl acetate Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Ethyl butanoate Ethyl 2-methylbutanoate Ethyl 3-methylbutanoate Butyl acetate 2-Methyl-1-propanol Methyl pentanoate 3-Pentanol
0–130 0–30 0–3500 10–1800 0–130 160–6000 0–5 0–480 0–1050 0–500 0–10 0–20 0–80 0–5
25 5 350 490 15 1500 1 100 190 30 2 2 25 1
5 6 7 10 11 12 15
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266 Table 1 (continued ) Peak no.
19 21 22 23 24 27 29 30
32 33 34 35 36
39 40 42 43 44 47 48 49 50 53 56 58 60 63 65 66 68 69
73 75 77 78 79
83 85 86 89 91
Aroma compound Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate Ethyl pentanoate Methyl hexanoate Limonene 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol Z-Ocimene 3-Methyl-2-buten-1-yl acetate Methyl Z-3-hexenoate Methyl E-3-hexenoate Hexyl acetate 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard Ethyl 2-hydroxy-2-methylbutanoate Ethyl E-3-hexenoate Methyl 2-hydroxypropanoate 3-Methyl-2-buten-1-ol Ethyl heptanoate Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal Methyl (methylthio)acetate Methyl Z-3-octenoate Ethyl octanoate Ethyl (methylthio)acetate Methyl E-3-octenoate Methyl 3-hydroxybutanoate Ethyl Z-3-octenoate Dimethyl malonate Methyl 3-(methylthio)-propanoate Methyl 3-acetoxybutanoate Ethyl 3-(methylthio)-propanoate Ethyl 3-acetoxybutanoate 2,5-Dimethyl-4-methoxy-3(2H)furanone Dimethyl succinate Methyl decanaote g-Butyrolactone Methyl benzoate 3-(Methylthio)propyl acetate Methyl Z-4-decenoate Methyl 3-hydroxyhexanoate Ethyl decanoate Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate 3-(Methylthio)-1-propanol Ethyl 5-oxohexanoate Ethyl 3-acetoxyhexanoate Ethyl phenylacetate d-Hexalactone Methyl 5-acetoxyhexanoate g-Heptalactone Ethyl 5-acetoxyhexanoate Methyl 5-hydroxyhexanoate d-Heptalactone
Range (mg/l) 0–60 0–15 0–620 0–45 15–3800 0–5 0–380 0–3500 0–10 0–3 t t t t 0–3 0–18 t 0–3 0–95 t t 0–15 0–2 0–5 0–80 0–5 0–230 0–200 0–120 0–80 0–450 0–10 0–10 0–50 0–80 15–1200 40–7100 0–380 15–2700 0–55 20–9200 0–10 0–20 0–700 0–5 0–40 0–60 1–570 0–50 0–460 0–3600 0–1500 0–95 0–10 0–340 0–5 0–1500 15–1700 0–130 0–320 0–200 0–60
Mean (mg/l) 10 2 70 10 1300 1 40 500 2 t t t t t 1 5 t t 15 t t 2 t 1 10 1 50 10 15 15 40 1 1 20 10 380 1500 120 470 5 1500 2 1 100 1 5 5 205 5 75 715 460 10 1 60 1 250 700 15 55 50 5
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267
Table 1 (continued ) Peak no.
Aroma compound
93 94
Methyl 3-hydroxyoctanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate d-Octalactone 2,5-Dimethyl-4-hydroxy-3(2H)furanone Ethyl 5-acetoxyoctanoate g-Decalactone d-Decalactone 4-Vinylguaiacol Solerone g-Dodecalactone d-Dodecalactone
96 97 102 103 104 105
Range (mg/l) 0–30 0–410 0–80 0–400 0–780 5–4700 0–15 0–20 0–160 0–30 0–80 0–60 0–52
Mean (mg/l) 5 90 5 60 100 960 2 4 15 5 20 10 6
t=trace o1 mg/l. For each component ranges of amounts and mean values are given.
Table 2 Aroma compounds identified by HRGC-MS in commercial pineapple water phases/recovery aromas (n ¼ 8) Peak no.
4 5 7 9 10 11
13 14 17 19
22 24 25 27 29
32 33 35
Aroma compound Ethyl propanoate Ethyl methylpropanoate Propyl acetate 2,3-Butandione Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Methyl 3-methylbutanoate Ethyl butanoate Ethyl 2-methylbutanoate Ethyl 3-methylbutanoate Butyl acetate Hexanal 2-Methyl-1-propanol Methyl pentanoate Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate 1-Butanol Ethyl pentanoate 1-Penten-3-ol Ethyl 2-butenoate 1,4-Cineol 2-Heptanone Methyl hexanoate Limonene 2-/3-Methyl-1-butanol E-2-Hexenal Ethyl hexanoate 1-Pentanol Z-Ocimene 3-Methyl-2-buten-1-yl acetate Methyl Z-3-hexenoate Methyl E-3-hexenoate Hexyl acetate 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard
Range (mg/l) 0–3.5 0–1.5 0–9.0 0–40 0–72 0–0.1 0–610 0–11.5 0–3.0 0–109 0–300 0–1.0 0–0.2 0–0.1 0–400 0–0.4 0–23 0–0.8 0–240 0–0.4 0–0.4 0–0.6 0–12 0–0.5 0–0.04 0–1730 0–12 0–95 0–0.8 0–1110 0–0.05 0–2.9 0–0.4 0–0.35 0–0.5 0–0.03 0–2.9 0–18 0–0.04
Mean (mg/l) 0.70 0.25 1.5 6 12 0.01 85 1.9 0.50 17 45 0.16 0.03 0.02 57 0.1 3.3 0.1 32 0.1 0.14 0.08 1.6 0.06 0.005 220 1.7 21 0.1 145 0.005 0.4 0.1 0.08 0.12 0.005 1.1 4.2 0.005
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268 Table 2 (continued ) Peak no.
Aroma compound
Range (mg/l)
Mean (mg/l)
36 37
Ethyl 2-hydroxy-2-methylbutanoate Ethyl E-3-hexenoate Methyl 2-hydroxypropanoate 3-Methyl-2-buten-1-ol Ethyl heptanoate Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal Methyl 2-hydroxy-3-methylbutanoate Methyl (methylthio)acetate E-2-Hexen-1-ol Ethyl 2-hydroxy-3-methylbutanoate Methyl Z-3-octenoate Ethyl octanoate Ethyl (methylthio)acetate Furfural Acetic acid Methyl 3-hydroxybutanoate Ethyl Z-3-octenoate 1-Decanol Decanal Methyl 2-octenoate Dimethyl malonate Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butandiol Methyl 3-acetoxybutanoate Linalool Ethyl 3-(methylthio)-propanoate Ethyl 3-acetoxybutanoate 2,5-Dimethyl-4-methoxy-3(2H)furanone 4-Terpinenol Dimethyl succinate Ethyl 2-hydroxyhexanoate g-Butyrolactone 3-(Methylthio)propyl acetate Methyl Z-4-decenoate Methyl 3-hydroxyhexanoate Ethyl decanoate Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate a-Terpineol 3-(Methylthio)-1-propanol Ethyl 5-oxohexanoate Ethyl 3-acetoxyhexanoate Ethyl phenylacetate d-Hexalactone Methyl 5-acetoxyhexanoate g-Heptalactone Ethyl 5-acetoxyhexanoate 2-Phenylethyl acetate Methyl 5-hydroxyhexanoate p-Cymen-8-ol Geraniol Methyl 3-hydroxyoctanoate Ethyl 3-hydroxyoctanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate
0–2.5 0–95 0–0.1 0–0.25 0–15 0–1.5 0–1.4 0–1.7 0–2.7 0–77 0–0.7 0–0.01 0–1.1 0–0–05 0–0.5 0–30 0–107 0–1.5 0–1.2 0–2.2 0–0–6 0–34 0–0.45 0–0.1 0–0.6 0–25 0–0.1 1–750 0–2.2 0–14 0–0.28 0.5–700 0–17 0–58 0–0.5 0–10 0–0.08 0–0.36 0–21 0–9.6 0–27 0–18 0–7.1 0–74 0–18 0–0.5 0–1.4 0–2.5 0–5.9 0–0.16 0–4.3 0–6.9 0–6.2 0–13 0–270 0–6.9 0–0.12 0–0.9 0–3.1 0–0.05 0–49 0–1.9 0–3.0
0.4 12 0.01 0.06 1.8 0.24 0.26 0.24 0.6 10 0.1 0.005 0.2 0.005 0.1 3.8 13.5 0.3 0.16 0.4 0.11 4.3 0.06 0.02 0.09 3.4 0.01 112 0.3 2.1 0.07 109 2.2 10 0.17 2 0.01 0.05 2.8 1.4 5.1 2.3 2.1 9.9 7.8 0.11 0.25 0.36 2.4 0.03 0.6 2.2 0.9 2.4 34 1.0 0.02 0.14 0.45 0.01 6.4 0.3 0.44
40 41 42 43 45 47
50
53
56 58 60 63 66 67
73 75 77 78 79 81 82 83 85 86 88 89 91
93 94 96
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269
Table 2 (continued ) Peak no.
Aroma compound
97 102
d-Octalactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone Ethyl 5-acetoxyoctanoate Ethyl cinnamate g-Decalactone d-Decalactone g-Dodecalactone d-Dodecalactone
103 105
Range (mg/l) 0–0.02 0–7.5 0–0.13 0–0.06 0–5.9 0–0.04 0–5.6 0–0.03
Mean (mg/l) 0.005 1.1 0.02 0.01 0.78 0.007 0.7 0.004
For each component ranges of amounts and mean values are given.
Table 3 Aroma compounds identified by HRGC-MS in commercial pineapple concentrates (n ¼ 10) Peak no.
32 35
45 46 51 52
54 55 57 58
64 69 74 76 78 81 84 85
Aroma compound 3-Methyl-2-butanone 2-Pentanone 2-Methyl-3-butene-2-ol Hexanal 2-Methyl-1-propanol 3-Pentanol 2-Pentanol 1-Butanol Methyl hexanoate Limonene 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol 3-Hydroxy-2-butanone Standard 3-Methyl-2-buten-1-ol 1-Hexanol 6-Methyl-5-hepten-2-one Z-3-Hexen-1-ol Nonanal 2-Methyl-2(3H)-furanone E-Linalooloxid 3-(Methylthio)-propanal Furfural Z-Linalooloxid Acetic acid Methyl 3-hydroxybutanoate 2,5-Dimethyl-3(2H)-furanone 2-Furylmethylketone Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butanediol Linalool 5-Methylfurfural g-Butyrolactone Phenylacetaldehyde Methyl 3-hydroxyhexanoate Furfurylalcohol g-Hexalactone Methyl 3-acetoxyhexanoate 3-(Methylthio)-1-propanol Methyl nicotinate d-Hexalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate
Range (mg/kg) 0–250 0–45 0–5 0–25 0–270 0–20 0–75 0–10 0–15 0–25 0–430 0–10 0–90 0–140 0–50 0–10 0–25 0–5 0–50 0–25 0–150 10–170 50–6500 0–60 0–2000 0–20 0–1500 0–120 0–50 0–200 0–200 0–30 0–200 0–250 3–400 0–50 0–60 0–260 0–230 0–130 0–40 0–340 0–40 0–400
Mean (mg/kg) 25 5 1 4 30 2 10 2 1 3 50 1 9 40 8 1 4 1 10 10 30 90 2500 20 350 2 400 35 15 40 30 6 50 60 230 10 25 40 30 15 10 40 7 60
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270 Table 3 (continued ) Peak no.
98
102 104
106 107
Aroma compound d-Octalactone Maltol 3-Hydroxy-(2H)-pyran-2-one Pantolactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone 4-Vinylguaiacol Solerone Solerol 4-Vinylphenol 5-(Hydroxymethyl) furfural
Range (mg/kg) 0–2 0–25 0–80 0–180 0–13500 0–1200 0–600 0–260 0–640 0–350
Mean (mg/kg) 1 5 15 40 1600 450 60 30 150 70
For each component ranges of amounts and mean values are given.
Fig. 2. Total ion chromatograms (TIC) of pineapple volatiles in representative examples of (a) commercial single strength juice; (b), (c) commercial juices made from concentrate. The peak numbers correspond to that given in Table 4.
(58; 0.04–7.1 mg/l), 2,5-dimethyl-4-methoxy-3(2H)-furanone (66, mesifurane; 0.02–9.2 mg/l), and 2,5-dimethyl4-hydoxy-3(2H)-furanone (102, furaneol, 0.005–4.7 mg/l)
as the major compounds of pineapple fruits. Amounts of 41 mg/l were also reached by methyl butanoate (5, 0.01–1.8 mg/l), methyl hexanoate (22, 0.015–3.8 mg/l),
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271
Table 4 Aroma compounds identified by HRGC-MS in commercial pineapple single strength juices (A; n ¼ 6) and pineapple juices made from concentrates (B; n ¼ 11) Peak no.
Aroma compound
A (mg/l) Range
3 4 5 6 7 8 10 11
14 15
19 20 22 23 24 27
32 33 35 38 40 41 42 44 45 46 47 51 52 53 54 55 56 57 58 59 60 63 65
69 71
Ethyl propanoate 3-Methyl-2-butanone 2-Pentanone Propyl acetate 2,3-Butanedione Methyl butanoate Ethyl 2-propenoate Methyl 2-methylbutanoate 2-Methyl-3-butene-2-ol Ethyl butanoate Ethyl 2-methylbutanoate Butyl acetate Hexanal 2-Methyl-1-propanol Methyl pentanoate Diethyl carbonate 2-Pentanol 2-/3-Methylbutyl acetate 1-Butanol b-Myrcene Methyl hexanoate Limonene 1,8-Cineol 2-/3-Methyl-1-butanol Ethyl hexanoate 1-Pentanol p-Cymene 3-Hydroxy-2-butanone Methyl 2-hydroxy-2-methylbutanoate Methyl heptanoate Standard Ethyl 2-hydroxy-2-methylbutanoate 3-Methyl-2-buten-1-ol Ethyl 2-hydroxypropanoate 1-Hexanol Methyl 3-hydroxy-3-methylbutanoate Z-3-Hexen-1-ol Methyl octanoate Nonanal 2-Methyl-3(2H)-furanone Methyl (methylthio)acetate 3-(Methylthio)-propanal Furfural Acetic acid Methyl 3-hydroxybutanoate 2,5-Dimethyl-3(2H)-furanone 2-Furylmethylketone Dimethyl malonate Benzaldehyde Methyl 3-(methylthio)-propanoate 2,3-Butanediol Methyl 3-acetoxybutanoate Ethyl 3-(methylthio)-propanoate 5-Methylfurfural Ethyl 3-acetoxybutanoate Linalool 2,5-Dimethyl-4-methoxy-3(2H)furanone g-Butyrolactone 3-(Methylthio)-propyl acetate
B (mg/l) Mean
Range
Mean
0–3 nd 0–20 0–700 0–30 0–250 0–160 0–800 0–18 0–90 0–80 t nd 4–10 0–10 0–3 0–5 0–12 0–7 nd 1–900 0–10 nd 20–100 0–80 0–2 nd 30–1800 0–100 nd
1 nd 3 170 10 60 30 180 4 30 25 t nd 10 2 1 2 6 4 nd 200 3 nd 50 25 1 nd 850 25 nd
0–1 0–7 0–6 nd 0–2 0–7 0–115 0–6 0–37 0–10 0–50 0–5 0–4 0–28 nd nd 0–3 0–6 0–13 0–2 0–15 0–135 0–6 0–150 0–9 0–1 0–44 8–230 0–3 0–3
1 1 1 nd 1 1 20 2 6 3 10 1 1 4 nd nd 1 3 4 1 3 35 1 18 2 t 4 60 t t
0–2 0–6 0–10 0–10 0–40 0–35 0–40 0–15 nd 0–50 2–50 20–2000 0–330 0–70 0–240 0–19 0–400 0–6 25–2200 0–130 0–100 0–400 nd 0–5 nd 0–400 0–200 0–4
1 3 3 4 10 10 8 3 nd 10 15 450 55 20 60 5 110 1 550 40 35 130 nd 2 nd 110 75 2
0–1 0–2 0–2 0–3 nd nd nd 0–1 0–18 nd 0–60 7–1300 0–340 0–3 4–750 0–33 0–4 0–5 1–29 0–500 0–4 0–50 0–35 nd 0–4 0–11 0–64 nd
t 1 t 1 nd nd nd t 2 nd 7 173 31 1 150 8 1 3 12 77 1 12 3 nd 1 1 33 nd
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272 Table 4 (continued ) Peak no.
Aroma compound
A (mg/l) Range
72 74 75 76 77 78 79 81 83 85 86 89 94 95 96 97 98 99 101 102 103 104 106 107
Butanoic acid Phenylacetaldehyde Methyl 3-hydroxyhexanoate Furfurylalcohol Ethyl 3-hydroxyhexanoate g-Hexalactone Methyl 3-acetoxyhexanoate a-Terpineol 3-(Methylthio)-1-propanol Ethyl 3-acetoxyhexanoate d-Hexalactone Methyl 5-acetoxyhexanoate Ethyl 5-acetoxyhexanoate g-Octalactone 2-Phenylethanol Methyl 5-acetoxyoctanoate d-Octalactone Maltole 3-Hydroxy-(2H)-pyran-2-one Pantolactone 2,5-Dimethyl-4-hydroxy-3(2H)-furanone g-Decalactone d-Decalactone 4-Vinylguaiacol g-Dodecalactone 4-Vinylphenol d-Dodecalactone 5-(Hydroxymethyl)furfural
0–20 0–170 0–110 0–28 0–50 0–870 0–110 nd 0–90 0–36 0–360 0–250 0–24 0–370 0–55 0–13 0–131 0–3 0–1700 0–34 0–3500 0–58 0–22 0–230 0–9 8–190 0–10 0–450
B (mg/l) Mean
Range
Mean
6 30 44 6 27 230 50 nd 26 13 80 86 14 70 38 5 31 t 330 7 1000 11 7 40 6 70 4 86
0–6 0–132 0–4 0–16 0–4 8–53 0–30 0–8 0–80 0–7 0–41 0–7 0–2 0–11 0–65 0–3 0–15 0–9 nd 0–93 0–1005 t nd 0–190 0–16 0–200 0–7 0–60
1 13 2 3 1 22 6 2 10 1 15 2 t 2 9 t 4 2 nd 22 305 t nd 17 7 30 2 24
t=trace o1 mg/l; nd=not detectable. For each component ranges of amounts and mean values are given.
ethyl hexanoate (27, 0–3.5 mg/l), ethyl 3-(methylthio)propanoate (63, 0.015–2.7 mg/l), g-hexalactone (78, 0–3.6 mg/l), d-hexalactone (85, 0–1.5 mg/l), and methyl 5-acetoxyhexanoate (86, 0.015–1.7 mg/l). Only a part, i.e. 20% of the water phases/recovery aromas under study contained a high number of the typical volatiles as found in the juices made from freshcut pineapple fruits. In comparison to the fruit flavour profile, however, also in these cases differences were obvious, as shown in the representative example of Fig. 1b. Methyl hexanoate (22, 0–1730 mg/l), ethyl hexanoate (27, 0–1110 mg/l), methyl-3-(methylthio)-propanoate (58, 1–750 mg/l) and ethyl 3-(methylthio)-propanoate (63, 0.5–700 mg/l) were observed as major constituents (Table 2). In most cases, the characteristic methyl esters and hydroxy or acetoxy esters were lacking completely or appeared only in minor amounts. There are many reasons which might be discussed to explain these findings: they mainly comprise the selection of inappropriate fruit varieties and flavour losses or modifications during post-harvest handling (Elss, Preston, Hertzig, Richling, & Schreier, 2003) or in the course of distillation and flavour recovery. However, as obviously a part of the producers is able to provide appropriate
qualities, the problem should be rather an economic than a technological one. As expected, the flavour profile of pineapple juice concentrates was determined by thermally formed compounds such as, e.g. furfural (52; 0.05–6.5 mg/kg) and 4-vinylguaiacol (104; 0.3–1.2 mg/kg), and nondistillable substances, as typically furaneol (102, 0–13.5 mg/kg) (Fig. 1c and Table 3). From these compounds enriched in the concentrates, furaneol determines their sensory character. Many years ago, its ‘pineapple-caramel’ note has led to its detection in pineapple and its structural elucidation (Rodin, Himel, Silverstein, Leeper, & Gortner, 1965; Willhalm, Stoll, & Thomas, 1965). In addition, the aroma profile of a number of commercial pineapple juices was analysed; they comprised both single strength juices and products made from concentrates. As representative examples, Fig. 2 shows the flavour profiles of a single strength juice (2a) and two samples of juices made from concentrate (2b and c). In Table 4 the identified constituents and their range of amounts determined in the samples under study are outlined. At a first glance, it is obvious that much less compounds were detectable and, quantitatively, also
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the amounts of aroma constituents comprised only a small part of that found in juices made from fresh-cut fruits (Table 1). The quantities (ranges and mean values) of selected pineapple volatiles as determined in juices from fresh-cut fruits and the two kinds of commercial juices are graphically compared in Fig. 3. Compared to the juices made from concentrates, the volatile profiles of the single strength juices match better with the genuine fruit profiles. As expected, they showed also some components caused by thermal treatment (pasteurization), such as, e.g. furfural (52), 3-hydroxy[2H]-pyran-2-one (99), pantolactone (101), furaneol (102) and 5-(hydroxymethyl)furfural (107). Surprisingly, their acetoin (32) content was rather high, i.e. surpassing approximately 10 times that of the juices made from concentrates (Table 4). In addition, in one case 2ethylhexanoic acid was detected as chemical contaminant in amounts of about 0.5 mg/l. Its teratogenic effects are known (Lampen, Zimnik, & Nau, 2003). The contamination is probably due to migration from the gasket of the metal lid (Elss, Gru¨newald, Richling, & Schreier, 2004). The flavour profile of the pineapple juices made from concentrates under study were mainly characterized by the profile found for concentrates. Similar to the juice concentrates, furaneol (102) and furfural (52) were found as major compounds in these products. None of the samples under study showed the characteristic genuine pineapple flavour composition or that of the waterphase/recovery aromas. Obviously, the typical ‘pineapple’-like aroma of furaneol (102) constitutes the sensorical acceptance of the products more or less lacking the pineapple fruit-typical flavour profile. In addition, juices made from concentrates showed small amounts of some terpenes, probably caused by contamination in the course of the industrial production chain. Thus, in a few samples terpenes such as 1,8cineol, p-cymene, b-myrcene, a-terpineol or linalool were found; none of them were observed in the juices made from fresh-cut fruits. Small amounts of limonene (up to 5 mg/l) were detectable in the fruits, but commercial juices from concentrates exhibited amounts of limonene up to 135 mg/l (mean 35 mg/l). Similar results as found for commercial juices made from concentrates were obtained for the pineapple jams under study (individual data not shown). Their profiles were determined by the Maillard reaction products furfural (0.08–0.6 mg/kg) and 5-(hydroxymethyl)furfural (0.02–1.6 mg/kg). Characteristic esters were lacking completely or appeared just in traces, furaneol and the pineapple lactones were found in low total amounts of p0.06 and p0.13 mg/kg, respectively. In conclusion, in spite of the limited number of samples and the restriction to the German market, the present studies stress (i) the high variability in the amounts of pineapple fruit volatiles depending on
273
7 11 22 27 58 63 66 69 75 77 78 79 83 85 94 97 102 0
500
1000
1500
2000
µg/L
Fig. 3. Comparison of the amounts (ranges and mean values, mg/l) of selected pineapple volatiles identified by HRGC-MS in juices self-made from fresh-cut fruits ( ), commercial single strength juices ( ), and commercial juices made from concentrates (&). The numbers correspond to that given in Tables 1 and 4. 7 Methyl 2-methylbutanoate 11 Ethyl 2-methylbutanoate 22 Methyl hexanoate 27 Ethyl hexanoate 58 Methyl 3-(methylthio)-propanoate 63 Ethyl 3(methylthio)-propanoate 66 Methoxyfuraneol 69 g-Butyrolactone 75 Methyl 3-hydroxyhexanoate 77 Ethyl 3-hydroxyhexanoate 78 gHexalactone 79 Methyl 3-acetoxyhexanoate 83 Ethyl 3-acetoxyhexanoate 85 d-Hexalactone 94 g-Octalactone 97 d-Octalactone 102 Furaneol.
the cultivar (origin), (ii) the problems of pineapple flavour stability during post-harvest handling, flavour recovery and fruit juice technology, as well as (iii), the
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need of product quality control to be intensified in future.
Acknowledgements The financial support kindly provided by the Forschungskreis der Erna¨hrungsindustrie e.V. (FEI), Bonn, the Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) and the Ministry of Economics and Labour (project no. 13203N) is gratefully acknowledged. Lena Gru¨newald is thanked for skilful technical support. References Askar, A., & Treptow, H., 2001. Verarbeitung von tropischen Fru¨chten. In: Schobinger, U. (Ed.), Frucht- und Gemu¨sesa¨fte (3. Aufl., pp. 242–245). Stuttgart: Ulmer. Bartholomew, D., Pauli, R. E., & Rohrbach, K. (2003). The pineapple. Botany, production and uses, Cambridge, MA, USA: CABI Publ. Engel, K. H., Heidlas, J., & Tressl, R. (1990). The flavor of tropical fruits (banana, melon, pineapple). In I. D. Morton, & A. J. MacLeod (Eds.), Developments in food science 3C (food flavours) (pp. 195–219). Amsterdam: Elsevier. Elss, S., Preston, C., Hertzig, C., Richling, E., & Schreier, P. (2003). U¨ber das Aromaprofil der Ananas (Ananas comosus [L.] Merr.) Eine Nachernte-Studie. Flu¨ssiges Obst, 70, 734–737. Elss, S., Gru¨newald, L., Richling, E., & Schreir, P. (2004). Occurrence of 2-ethylhexanoic acid in foods packed in glass jars. Food Additives and Contaminants, 21, 811–814. Lampen, A., Zimnik, S., & Nau, H. (2003). Teratogenic phthalate esters and metabolites activate the nuclear receptors PPARs and induce differentiation of F9 cells. Toxicology and Applied Pharmacology, 188, 14–23. Preston, C., Richling, E., Elss, S., Appel, M., Heckel, F., Hartlieb, A., & Schreier, P. (2003). On-line gas chromatography combustion/
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