Influence of processing conditions on flavour compounds of custard apple (Annona squamosa L.)

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LWT 41 (2008) 236–243 www.elsevier.com/locate/lwt

Influence of processing conditions on flavour compounds of custard apple (Annona squamosa L.) Mysore N. Shashirekhaa, Revathy Baskarana, Lingamallu Jaganmohan Raob, Munusamy R. Vijayalakshmia, Somasundaram Rajarathnama, a Department of Fruit and Vegetable Technology, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India Department of Plantation Products Spices and Flavour Technology, Central Food Technological Research Institute, Mysore 570 020, Karnataka, India

b

Received 10 November 2006; received in revised form 6 March 2007; accepted 6 March 2007

Abstract Changes in volatile compounds of fruit pulp of Annona squamosa, as influenced by the conditions of processing, were studied. Sweet and pleasant flavored pulp from mature ripe fruits was subjected to treatments such as frozen and stored (for 12 months), heated to 55 1C (critical temperature) and 85 1C (pasteurization temperature) for 20 min each, and spray dried with skim and whole milk powders. Volatiles from these samples were extracted into dichloromethane and n-pentane (1:1), and were subjected to gas chromatograph (GC) and gas chromatograph–mass spectrometer (GC–MS) analysis for identification and quantification of chemical constituents. Terpenes such as a-pinene, b-pinene, linalool, germacrene-D and spathulenol, esters like sec-butylbutanoate, and methyllinolenate, along with benzyl alcohol and two oxygenated sesquiterpenes were found to be the major volatiles of the fresh pulp. The 12-month-stored frozen pulp did not differ from the fresh pulp in the flavour spectrum. Heating fresh pulp at 55 and 85 1C, tended to produce increased flavour spectrum, the compounds relatively being more at 85 1C. At 55 1C, significant increase in the quantities of a-pinene, b-pinene, linalool, germacrene and spathulenol were observed; higher quantities of cineole, limonene, a-cubebene and a-copaene, caryophyllene, a-farnecene and d-cadenene were formed, while these were totally absent in fresh pulp. Significant increase in quantities of a-pinene, b-pinene, 1,8-cineole, limonene, aromadendrene, a-farnecene, g-cadenene, d-cadenene and spathulenol were found by heating pulp at 85 1C. Spray-dried samples, showed increased flavor note with the use of whole milk powder as compared to the skim milk powder. r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Keywords: Annona squamosa; Custard apple; Pulp; Heat; Spray dried; Frozen; Flavours; Gas chromatography; Mass spectrometry

1. Introduction The family Annonaceae contains a considerable number of plants of economic significance because of their edible fruits (Idstein, Herres, & Schreier, 1984; Le Boeuf, Cave, Bhaumik, Mukherjee, & Mukherjee, 1982).These crops represent the fruits of tropical America, Australia, Africa, India and Malaysia (Bartley, 1987; Wong & Khoo, 1993). Annona atemoya is reported to dominate the commercial market in Australia (Wyllie, Cook, Brophy, & Richter, Abbreviations: GC, gas chromatograph; GC–MS, gas chromatograph– mass spectrometer; FID, flame ionisation detector; SS, stainless steel Corresponding author. Tel.: +91 0821 2515653; fax: +91 0821 2517233. E-mail address: [email protected] (S. Rajarathnam).

1987). The fruit volatiles of A. atemoya (the hybrid between Annona squamosa, L. and Annona cherimolia, Mill.) are identified. A. squamosa is a popular fruit of the tropical states of India, with a very sharp and short season, lasting for about 3 months a year. This fruit is popularly known as sweet sop, is heart shaped weighing about 150 g, with a very bumpy skin. When ripe, pulp is creamy, very sweet and pleasantly flavoured. It is usually eaten as a dessert fruit and finds immense applications in the preparations of beverages and ice creams (Chikhalikar, Sahoo, Singhal, & Kulkarni, 2000). Storage of the fresh fruits of A. squamosa, has limitations, since it is perishable, and cold storage is not promising because of the development of an unattractive brown colour on the skin which decreases the market value (Purohit, 1995). The fruit pulp due to its richness in free

0023-6438/$30.00 r 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2007.03.005

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sugars, minerals and vitamins is known to serve as blood tonic (Rao, 1974). Custard apple grows with little agronomic care and excessive production during the season, very often perishes owing to inadequate preservation techniques. Canning of the custard apple pulp is problematic because of the development of bitterness and browning on heating beyond 55 1C (Bhatia, Sastry, Krishnamurthy, Nair, & Lal, 1961; Martinez, Medina, Fans, & Gill, 1988; Salunkhe & Desai, 1984). In addition, an unpleasant off-flavour develops in the pulp when heated beyond 65 1C (Nanjunda Swamy & Mahadevaiah, 1993). Information on the success of development of heat-processed products of A. squamosa fruit pulp is not available in literature. The pulp when exposed to air undergoes discolouration due to polyphenol-oxidase activity. Discolouration occurs during storage in frozen state and continues throughout thawing, and causes loss of quality and value (Pardede, Buckle, and Srzednicki, 1994). Prospero (1993) has observed that frozen custard apple pulp without any additives displayed discoloration in 2 h after exposure to ambient temperature. Through concerted research efforts, a range of processed products could be developed in this laboratory, through deviated steps of processing. Starting from fresh/frozen fruit pulp (Shashirekha, Rajarathnam, Vijayalakshmi, & Revathy, 2003a) jam (Vijayalakshmi, Shashirekha, Revathy, & Rajarathnam, 2003) jelly (Shashirekha, Rajarathnam, Vijayalakshmi, & Revathy, 2003b), fruit mix (Revathy, Rajarathnam, Shashirekha, & Vijayalakshmi, 2003), dehydrated (Rajarathnam, Shashirekha, Vijayalakshmi, & Revathy, 2003a), cereal flakes (Vijayalakshmi, Rajarathnam, Shashirekha, & Revathy, 2003) spray-dried powder (Revathy, Vijayalakshmi, Shashirekha, & Rajarathnam, 2003), nectar (Rajarathnam, Shashirekha, Vijayalakshmi, & Revathy, 2003b), and RTS beverage (Singh, Vijayalakshmi, Shashirekha, Revathy, & Rajarathnam, 2002) with storage life of 6 months were obtained. Pulp in frozen state was able to be stored for 12 months without discolouration (Shashirekha et al., 2003a). Their details are filed as national and international patents. Though several articles have dealt with characterization of flavour constituents of fresh pulp of Annona species (Bartley, 1987; Wong & Khoo, 1993; Wyllie et al., 1987), no information is available on the changes induced in flavour compounds due to processing conditions with respect to A. squamosa. The present paper describes the characterization of the volatile compounds of the fresh fruit pulp of A. squamosa and changes during processing as compared to 12 months stored frozen pulp. The effect of heating to 55 and 85 1C, and spray drying of the fresh pulp on the volatile compounds is dealt in this study.

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were procured from the orchards 100 km from Mysore. The fruits were allowed to ripen at room temperature (25–31 1C) and the ripe fruits were used for extraction of pulp. 2.2. Extraction of pulp The mature ripe fruits were opened approximately into two equal halves and the sweet pulp was scooped using stainless-steel spoons. The pulp was deseeded in the pilot plant using the pulper (M/S APV India, Calcutta: capacity: 1 ton/h; sieve size 1/80 cm) and the pulp obtained was stored and used for further processing. 2.3. Solvents All solvents used were analytical grade, procured from M/s. E-Merck, Bombay. 2.4. Isolation of flavor volatiles One hundred grams of fresh pulp or material equal to 100 g fresh custard apple pulp (in the case of other samples) was subjected to flavor extraction at room temperature using a mixture of dichloromethane and n-pentane in 1:1 ratio, (150 ml  3 times), previously chilled overnight at 25 1C. The collections were pooled and passed over anhydrous sodium sulphate. The anhydrous flavor extract was collected and concentrated using vigreux column to 1.0 ml. Ethyl caproate (250 mg) was used as the internal standard. Procedure for extraction of flavor volatiles is depicted in Fig. 1. 2.5. Freezing of pulp and storage Fresh custard apple pulp was packed in 1 kg quantities in 50  32 cm polyethylene bags (50 m) and sealed immediately after expelling air. The sealed bags were immediately transferred to blast freezer (M/S Foster and Co., England) at 20 1C. The frozen pulp was stored in deep freezers (M/S Blue Star, India) at 2571 1C for 12 months. The stored frozen pulp after thawing at room temperature was used for extraction of flavor volatiles as described earlier. 2.6. Heat treatments of pulp One hundred gram quantities of fresh pulp taken in 250 ml Erlenmeyer flasks were heated separately in a water bath held at 55 and 85 1C for 20 min each. The heated pulp after cooling to room temperature was used for extraction of flavor volatiles.

2. Materials and methods 2.7. Preparation of spray-dried powder 2.1. Fruits Mature fruits of custard apple (A. squamosa L.) measuring about 10 cm (dia) with density 1000–1100 g/l

Fresh pulp after supplementation with suitable binding, sweetening and anti-caking agents, passed through the colloidal mill and the feed material obtained was subjected

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Ripe fruits

Splitting into two halves

Scooping of seeded pulp Peel Seeded pulp

Pass through pulper

Pulp Fresh/stored/heated 100 g ( fresh weight)

Extract in chilled dichloromethane: n-pentane (1:1) 150ml×3 times Pool the extracts

Pass over anhydrous sodium sulphate

Concentration in vigreux column (< 35ºC) Flavour extract (1 ml) Fig. 1. Flow diagram for extraction of flavour volatiles from custard apple fruit.

to spray drying (Spray drier model: M/S Bowen BLSA; Bowen Engineering, USA; with an evaporative capacity of 15–80 kg water per hour), with an inlet temperature of 140 1C and outlet temperature of 110 1C. The details of processing conditions to obtain a powder free of bitterness, discoloration and off-flavour are covered under IPR (Revathy, Vijayalakshmi et al., 2003). 2.8. Gas chromatography Pre gas chromatograph (GC) analysis of volatiles of custard apple was carried out using Fison 8000 gas chromatograph fitted with FID and SE-30 (10% on chromosorb-W) S.S. column (100  1/800 ). The GC analytical conditions were: detector port temperature 250 1C; injection port temperature 250 1C; carrier gas nitrogen at 30 ml/min and oven temperature prog. 50 (2)–4/min–250 1C and 5 min held at 250 1C; 1 ml of flavour extract was injected at a time. 2.9. Gas chromatography–mass spectrometry (GC–MS) GC–MS analyses of the volatiles from custard apple samples were carried out using Shimadzu-17A gas chro-

matograph equipped with a QP-5000 quadrupole mass spectrometer. A fused silica SPBTM1 column [30 m  0.33 mm] of film thickness 0.25 mm (coated with polydimethyl siloxane) was used and the parameters used for the analysis were carrier gas helium with a flow rate of 1 ml/min, injection port temperature 250 1C, detector temperature 250 1C and the initial oven temperature was 50 1C for 2 min, then, it was increased to 250 1C at the rate of 2 1C/min and maintained at 250 1C for 5 min, ionisation voltage 70 eV. Retention indices of all the constituents were determined according to Kovats method by Jennings and Shibamoto (1980) using n-alkanes as standards. The compounds were identified by comparison of Kovat’s indices with those reported (Davies, 1990; Jennings & Shibamoto, 1980) and by comparison of their mass spectra with the published mass spectra (Adams, 1989; Jennings & Shibamoto, 1980) or from NIST-MS library. Ethyl caproate was used as internal standard for quantification. 3. Results and discussion The volatile components of fresh pulp were predominantly shared by the terpenes (Table 1). a-pinene, b-pinene, linalool, germacrene-D, and spathulenol were the major terpenoid compounds. Ester such as sec-butylbutonate, was also identified. In addition, octane, palmitic acid and methyllinolenate were identified. Benzyl alcohol also contributed to the spectrum of flavor compounds. Terpenoid compounds constituted 88.5% of the sweetsop volatiles (Wong & Khoo, 1993). Of the 13 monoterpenoid constituents identified, the most abundant were a-terpineol (5.1%), bornylacetate (1.8%), 1–8-cineole (1.4%), and b-pinene (1.3%). The sesquiterpene alcohols, spathulenol, globulol, viridifloral, T-cadinol, T-muurolol, and farnesol together accounted for 65.6% of the total volatiles. However, the A. atemoya volatiles were found to contain 7.4% limonene (not found in the A. squamosa volatiles) and higher concentrations of a- and b-pinene (25.6% and 21.0%, respectively) (Wyllie et al., 1987). Germacrene-D has been postulated to be the probable biogenic precursor of spathulenol-, globulol- and cadinene-type sesquiterpenes (Nishimura, Shinoda, & Hirose, 1969; Taskinen, 1974; Tressl, Engel, Kossa, & Koppler, 1983). It has been observed that the tropical fruits can be classified into two broad categories determined by whether esters or terpenoids predominate in the volatiles (Mac Leod & Ames, 1990). Accordingly, A. atemoya belongs to the first category, which also includes fruits like papaya (Mac Leod & Pieris, 1983). Similarly, A. squamosa and Annona reticulata falls into the second category of terpenoid flavours that includes mango too (Mac Leod & Pieris, 1984). Terpenoid compounds as flavour substances in Cinnamomum zeylanicum (Jayaprakasha, Jaganmohan Rao, & Sakaria, 1997, 2003), in sap of Mangifera indica (John, Jaganmohan Rao, Bhat, & Prasada Rao, 1999) and Citrus aurantifolia (Ramesh Yadav, Chauhan, Rekha, Jaganmohan Rao, & Ramteke, 2004) are studied from this lab.

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Table 1 Volatile components of fresh and processed custard apple pulp Sl. no.

RT (min)

Compounda

Quantity (mg) Fresh

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

4.24 8.48 9.19 10.29 12.50 12.97 13.13 17.29 34.11 35.67 38.12 39.45 41.91 42.85 43.99 44.61 47.26 51.59 53.35 67.43 69.81 75.21

Octane a-Pinene sec-Butylbutanoateb b-Pinene Benzyl alcohol 1,8-Cineole Limonene Linalool a-Cubebene a-Copaene Caryophyllene Aromadendrene Germacrene-D a-Farnesene g-Cadinene d-Cadinene Spathulenol Oxygenated sesquiterpeneb Oxygenated sesquiterpeneb Dibutylphthalatec Palmitic acid Methyl linolenate

7.270.34 6.370.31 9.470.41 6.870.35 15.970.78 Tr Tr 13.870.65 Tr Tr Tr Tr 15.770.63 Tr Tr Tr 42.872.02 9.870.46 8.770.41 70.070.37 186.974.4 14.970.74

Kovats indices Pulp heated

Spray-dried powder

55 1C

85 1C

Skim

Whole

tr 16.870.81 18.670.92 15.970.77 26.470.58 13.270.66 13.270.59 15.570.79 16.470.84 132.376.47 16.470.89 tr 132.373.98 25.970.57 Tr 17.770.32 66.871.34 Tr 14.170.41 75.073.02 291.475.03 15.070.66

tr 29.5571.01 17.0570.82 34.6671.13 22.7370.91 36.9371.20 19.3270.73 tr tr tr tr 19.3270.88 104.5472.92 30.1170.83 16.4870.80 28.4170.97 89.2071.89 tr tr 58.5271.25 101.7072.78 tr

25.3870.86 26.6570.78 36.8070.93 tr tr tr tr tr tr tr tr tr 144.6771.75 71.0771.04 tr tr 116.7572.23 tr tr 78.6871.89 81.2272.25 tr

14.6370.51 tr 25.8270.84 tr tr tr 17.6470.70 12.4870.39 12.0570.43 tr 14.6370.62 tr 186.3273.17 83.0571.88 tr tr 53.3671.54 tr tr 120.4972.99 63.2571.76 tr

800 927 943 965 1004 1013 1016 1084 1336 1360 1395 1416 1456 1471 1488 1497 1542 1613 1645 1907 1956 2067

a

Compounds identified from KI and MS. Tentatively identified. c It could be a contaminant. b

Flavor volatiles of Annona muricata (sour sop) during ripening are reported (Mac Leod & Pieris, 1981; Paull, Deputy, & Chen, 1983). (Z)-3-hexen-1-ol has been identified as the main volatile present in mature green sour sop, while methyl (E)-2-hexenoate, methyl (E)-2-butenoate, methyl butanoate and methyl hexanoate were the main volatiles present in ripe fruit (Iwaoka & Zhang, 1993). Flavour volatiles of A. cherimolia are reported to be composed of esters, especially various butonoates, 3-methyl butyl esters. Alcohols like 1-hexanol formed as enzymic degradation products of unsaturated fatty acids (Galliard, 1975), and terpenoids were oxygenated such as linalool, p-terpeniol, 4-terpeniol, carvone, 1,8-cineole. More information on the diversity of flavour volatiles of the Annonaceae is reviewed (Le Boeuf et al., 1982; Herrmann, 1981, 1983). The odor quality/flavour note of the volatile flavours is dealt (Mac Leod & Pieris, 1981). Esters as fruity/floral, alcohols as green and hydrocarbons as odorless are described. In order to recommend the conditions for frozen storage of pulp, it was required to ascertain the changes or similarities in the spectrum of flavour components between the fresh and the frozen stored. Since any temperature above 55 1C appears to act critically in influencing the quality of pulp (Bhatia et al., 1961), in terms of development of bitterness, discoloration and off-flavor development, the changes induced in flavor profile com-

pared to the fresh pulp were considered here. During processing, since 85 1C for 20 min is a critical temperature to achieve pasteurization, its effect on the flavor changes of pulp was undertaken. Finally, surprisingly a very good quality of spray-dried powder of custard apple (Revathy, Vijayalakshmi et al., 2003), starting with fresh/frozen pulp could be developed using selected binder, sweetening and anticaking agents, that was free of bitterness, discoloration and off-flavor. Sensorially, there was an improvement in the flavor taste of the spray-dried powder using whole milk powder compared to the skim milk. Total ion chromatograms of GC–MS of the volatiles are depicted in Figs. 2–6 The volatile flavour components of frozen pulp stored for 12 months (Shashirekha et al., 2003a) resembled the fresh pulp without changes in their transformation similar to that of fresh pulp depicted in Table 1. Hence, presentation of this data in figure/table was not implicated. This result upholds the identified conditions to recommend a process for the storage of fresh pulp, to possess native flavour in frozen stored form as long as a period of 12 months. Interesting changes in the nature of flavour volatiles were observed by heating the pulp at 55 or 85 1C compared to the fresh fruit pulp. At 55 1C, significant increase in the quantities of p-pinene, b-pinene, linalool, germacrene and spathulenol were observed; higher quantities of cineole, limonene, a-cubebene and a-copaene, caryophyllene,

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Fig. 2. Total ion chromatogram profile of volatiles of fresh pulp.

Fig. 3. Total ion chromatogram profile of volatiles of pulp heated at 55 1C for 20 min.

Fig. 4. Total ion chromatogram profile of volatiles of pulp heated at 85 1C for 20 min.

a-farnecene and d-cadinene were formed, while these were totally absent in fresh pulp. Oxygenated sesquiterpenes were also formed. Palmitic acid and benzyl alcohol showed a marginal increase compared to the fresh pulp. Some more transformations in the flavour components were evident by heating the pulp at 85 1C. Here, linalool, cubenene, copaene, caryophyllene and oxygenated sesquiterpenes were totally absent. Significant increase in quantities of

Fig. 5. Total ion chromatogram profile of volatiles of spray-dried powder (using skim milk).

Fig. 6. Total ion chromatogram profile of volatiles of spray-dried powder (using whole milk).

a-pinene, b-pinene, 1, 8-cineole, limonene, aromadendrene, a-farnecene, g-cadenene, d-cadenene and spathulenol were found by heating pulp at 85 1C compared to 55 1C. The pulp sample heated to 55 1C though was just acceptable, the pulp heated to 85 1C had developed bitterness and offflavor too; these sensorial changes are obviously to be ascribed to the above transformations in the flavour volatiles. Dramatic differences were observed in the flavour spectrum of the spray-dried powder as compared to the fresh pulp and also between the use of skim and whole milk powders for the preparation of spray-dried powder. Spray drying of custard apple pulp using skim milk powder served to significantly increase the a-pinene, butylbutonoate, germacrene-D and spathulenol; a-farnecene totally created new, whereas b-pinene, benzyl alcohol and linalool disappeared as compared to the fresh pulp. There was an increase in the spectrum of flavour volatiles with the use of whole milk powder compared to the skim; generation of limonene, linalool, a-cubebene and caryophyllene, and also there was an increase in the relative constituents of germacrene and a-farnecene. The comparison of flavour compounds of spray-dried powder with skim and whole milk powders eventually reflect on enhancement of the

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In plants and animals, dihydro cinnamic acids are the important precursors of benzoic acids (for the formation of benzoic acid derivatives from shikimic acid). The biogenesis of shikimic acid from D-erythrose-4-phosphate was well established with 14C and 18O studies (Torssell, 1997). It was reported that the activated benzoic acid derivatives (viz., CoA esters) can be reduced to benzaldehyde and benzyl alcohol derivatives (Torssell, 1997). Hence, formation of benzyl alcohol might have originated from the dihydro cinnamic acids. Acetic acid or its biosynthetic equivalent, acetyl CoA contributes significantly in the synthesis of fatty acids and also aromatic compounds. Linear Claisen condensation leads to b-keto esters, which either by reduction and repeated condensation give fatty acids or by further direct condensation, give polyketides, e.g., the biosynthesis of palmitic acid occurs with one unit of acetyl CoA as a starter, seven melanoyl CoA along with 14 NADPH units are needed. It is rather remarkable that in most organisms the chain elongation practically stops at C16. The enzyme readily accepts a C14 CoA ester as starter but reluctantly a C16 CoA. The successive addition of two carbon units to acetyl CoA explains commonness of even numbered acids; e.g., palmitic acid and methyl linolenate, etc. might have formed in the similar pathway (Torssell, 1997).

flavour profile by the use of the latter and, thus, possibly the fat/fatty acid contents to react and interact for the quantitative generation and expression of flavour components, ultimately attributing to the increased acceptability of the spray-dried powder with the use of whole milk powder. The differences in the flavor compounds due to heating of the pulp at 55 and 85 1C are interesting and thus brought out in Table 2, with reference to their structures being depicted in Fig. 7. Further, the possible pathways of their formation are enumerated below. Generally, terpenoids are the primary flavour and fragrance impact molecules found in the volatiles of higher plants. Significant among them are mono- and sesquiterpenoids. Plants produce large amounts of mono- and sesquiterpenoids, and acetyl CoA is the starting material for terpenoids through isoprenoids. In a branched condensation, the keto function of acetyl CoA reacts with another acetyl CoA molecule to form b-hydroxy-b-methyl glutaryl CoA, which is transformed into the active isoprene unit and ultimately to the terpenoids (Torssell, 1997). Majority of the constituents present in the volatiles of these fruits are mono- and sesquiterpenoids and their derivatives, and might have formed in the similar (Newman, 1972) pathway.

Table 2 Differences in flavor compounds due to heating of custard apple pulp at 55 and 85 1C (compared to flavor compounds of fresh pulp) Sl. No Flavor compounds

55 1C

85 1C

Newly formed Compounds disappeared 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Octane a-Pinene sec-butyl butanoate b-Pinene Benzyl alcohol 1,8-Cineole Limonene Linalool a-Cubebene a-Copaene Caryophyllene Aromadendrene Germacrene-D a- Farnesene g-Cadinene d-Cadinene Spathulenol Oxygenated sesquiterpene Oxygenated sesquiterpene Dibutylphthalate Palmitic acid Methyl linolenate

19 20 21 22 a

Absent in fresh pulp also. Intensity decreased. c Same as fresh. b

Intensity increased

Newly formed Compounds disappeared

O

Intensity increased

O O O O O

O O

O O O O O O

O

O O O

O a a a

O O

O

O O O O

O O

O

O

O O

O Could be a contaminant

O

b

c

O

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CH3(CH2)6CH3

α -Pinene

Octane

β-Pinene

CH2OH CH3CH2CH2COOCH2CH(CH3)2

sec-butylbutanoate

Benzyl alcohol

OH O

Limonene

1,8-Cineole

Linalool

H

H

H

α-Cubebene

Aromadendrene

α-Copaene

Germacrene-D

δ -Cadinene

Caryophyllene

α-Farnesene

γ - Cadinene

H CH3(CH2)14COOH OH Spathulenol

Palmitic acid

CH3CH2CHCHCH2CHCHCH2CHCHCH2CH2CH2CH2CH2CH2CH2COOCH3

Methyl linolenate Fig. 7. Structures of the volatile compounds identified from fruit pulp of Annona squamosa.

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