An Insight in Key Volatile Compounds in Goat Milk Based on their Odor Active Values

Article Information

Rita de Cássia R Egypto Queiroga1, Maria Terezinha Santos Leite Neta2, Rafael Donizete Dutra Sandes2, Narendra Narain2*, Mércia de Sousa Galvão1, Marta Suely Madruga1, Roberto Germano Costa3

1Universidade Federal da Paraíba, Food Engineering Department, João Pessoa-PB, Brazil

2Universidade Federal de Sergipe, Laboratory of Flavor and Chromatographic Analysis, São Cristóvão-SE, Brazil

3Universidade Federal da Paraíba, Farming Department, Bananeiras-PB, Brazil

*Corresponding Author: Narendra Narain, Universidade Federal de Sergipe, Laboratory of Flavor and Chromatographic Analysis, CEP: 49100-000, São Cristóvão-SE, Brazil

Received: 08 March 2019; Accepted: 18 March 2019; Published: 21 March 2019

Citation:

Rita de Cássia R Egypto Queiroga, Maria Terezinha Santos Leite Neta, Rafael Donizete Dutra Sandes, Narendra Narain, Mércia de Sousa Galvão, Marta Suely Madruga, Roberto Germano Costa. An Insight in Key Volatile Compounds in Goat Milk Based on their Odor Active Values. Journal of Food Science and Nutrition Research 2 (2019): 049-060.

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Abstract

Goat milk is known to possess an off-flavor generally known as ‘goaty flavor’, which is not appreciated by consumers. Mostly the short-chain fatty acids are responsible for this undesirable sensory attribute. The objective of the present work was to identify the volatile compounds present in goat milk and to relate their impact on aroma characteristics. Volatile compounds from the milk were obtained by using a simultaneous distillation and extraction technique utilizing Likens and Nickerson’s apparatus. Two hundred milliliter of milk was used and extraction was carried out at 55°C for 120 min by using a mixture of pentane-ethyl ether (2:1) solvent. The extracts were concentrated and analyzed for the identification of volatile compounds using a system of high resolution gas chromatograph coupled with mass spectrometer. Better separation was achieved in a non-polar capillary column. A total of 91 volatile compounds were positively identified and these represented mostly the classes of compounds belonging to esters, aldehydes, alcohols, fatty acids, ketones and aromatics. The main compounds and their concentrations were hexanol (9481.92 µg/L), pentanoic acid (3040.08 µg/L), 2-pentanone (1651.03 µg/L), methyl 9-octadecenoate (1613.88 µg/L), methyl hexadecanoate (1060.61 µg/L) and 2-pentanol (1683.28 µg/L), while the compounds with their OAVs of 5 and higher that contribute in goat milk aroma were decanal (88), (E)-2-hexenal (72), hexanol (47), octanal (40), ethyl hexanoate (35), pentanal (34), nonanal (30), 2-pentanone (24), heptanal (23), methyl hexanoate (20), γ-dodecalactone (11), 2-heptanone (10), heptanol (9), ethyl octanoate (9), 2-pentadecanone (9), β-ionone (8), α-pinene (5), 2-methylthiophene (5), octadecanal (5).

Keywords

Goat milk, Volatile Compounds, Aldehydes, Alcohols, Esters, Lactones, Carboxylic acids

Article Details

1. Introduction

The main components of the milk, which contribute to the flavor and other sensory attributes, are proteins and fats. Goat milk has more nutritional qualities that are better for human consumption than cow’s milk, such as less lactose levels, more quantity of vitamins and reduced lipids amount. Other characteristic of goat milk is its distinctive aroma and flavor, which are derived from their lipid fraction and it varies widely based on principal factors such as genetic diversity of breed, feeding practices, season of obtaining milk and lactation stage. Goat milk is different from cow’s milk due to its “goaty” flavor and aroma classified in off-flavor attributes, which are not quite appreciated by consumers. Scientific knowledge on precursors leading to the formation of characteristic goat milk flavor is limited. Mostly the short-chain (C6, C8 and C10) fatty acids are held responsible for this undesirable sensorial attribute [1]. Ha and Lindsay reported the triglyceride composition of goat, sheep and cow milks, attributing the presence of minor branched chain compounds in goat milk, including 4-methyl octanoic acid which has an extremely low odor threshold value. Moreover, the goat milk flavor is the result of the lipolytic action of the milk lipoprotein lipase, which in goat milk is largely bound to the fat [2].

Very few publications are available which deal with identification and quantification of volatile compounds present in goat milk [1, 3, 4, 5] and these relate mostly to the feeding systems and their effect on the composition and flavor quality of goat milk. Fedele et al. [3] reported the presence of β-caryophyllene and α-copaene as dominant terpenes in goat milk. Queiroga et al. [6] detected 174 volatile compounds from goat milk, such as phenols, acids, lactones, ketones, alcohols, esters and terpenes. The presence of terpenic compounds is related to the plant species utilized for the feeding systems. Yang et al. [1] identified the compounds responsible for the “goaty” flavor in goat milk as being short fatty acids (C6:0 to C9:0). Flavor of dairy products is a critical parameter affecting consumer acceptance, shelf life, and other attributes [7, 8]. Since goat milk has gained economic importance and is classified as a functional food, it participates in health maintenance and reduces disease. Of late, there is an increase in goat milk production due to its utilization in cheese making. In the Mediterranean and many eastern European countries, it is important to elucidate the aroma composition to help to avoid the development of products with off-flavor in order to increase its consumption [9-11]. Thus, the objective of the present work was to identify the volatile compounds present in goat milk and to acquire an in depth knowledge on key volatile compounds as related to their odor active values contributing to the milk’s overall aroma characteristics.

2. Material and Methods

The goat milk was collected from 20 animals of Saanen breed, which were confined in the Sector of Caprinoculture of Federal University of Paraíba, located in city of Bananeiras. The animals were fed with a feed containing grass Tiffton mixed with a balanced diet.

2.1 Volatiles isolation

The volatile compounds were extracted by using Likens and Nickerson’s [12] apparatus, which uses the simultaneous distillation and extraction technique. The extraction conditions were optimized by Queiroga et al. [6] in which 200 mL of goat milk was diluted with 100 mL of distilled water and extraction was performed with 20 mL of pentane:ether (2:1) for 120 min. The extracts were concentrated to a final volume of 0.3 mL under the flow of nitrogen gas.

2.2 High resolution gas chromatography/mass spectrometry

A combined system of gas chromatograph (Shimadzu GC 17A) coupled with a mass spectrometer (GC/MS-QP5050A) was used. One microliter of the concentrated volatile extract was injected in the column in a splitless mode. Capillary GC investigations were carried out on non-polar capillary column HP-5MS (30 m × 0.25 mm; 0.25 µm). The carrier gas used was helium and column head pressure was maintained at 11.5 psi having a flow rate of 1 mL/min. The oven temperature was programmed: initiation at 30°C for 5 min, increased at 5°C/min to 80°C, maintained at 80°C for 30 min, increased at 5°C/min to 220°C, wherein maintained for 45 min. The temperatures of the injection port and the GC/MS interface were 200°C and 230°C, respectively. The mass spectrometer was operated in the electron ionization mode with an electrical energy of 70 eV and an ion source temperature of 250°C. The mass spectrum was scanned between 30 and 350 atomic mass units at 0.1 sec interval. The identification of compounds was done by using the linear retention index (LRI) values, determined on retention time data obtained by analyzing a series of normal alkanes (C8-C21). Volatile components were positively identified by matching their LRI values and mass spectra with those of standards, also run under identical chromatographic conditions in the laboratory.

2.3 Quantification of volatile compounds

The volatile compounds were quantified using the analytical curves prepared from the results obtained on chromatographic analysis of aroma compound standards of different classes of organic compounds such as esters, alcohols, ketones, aldehydes and terpenes, also performed under identical analytical conditions as that of the samples.

2.4 Statistical analysis

All chromatographic data were analyzed in triplicate and the results were expressed as mean ± standard deviation values.

3. Results and Discussion

3.1 Volatile profiles of goat milk

Table 1 lists the volatile compounds identified in goat milk. The data cites the retention indices and the concentration of the identified compounds, which are organized according to their organic classes. It was observed that some compounds have the superscript letter a, which signifies that the compound was tentatively identified since there was no pure standard compound available, which could be run under the identical analytical conditions. Thus the identification was considered tentative when it was based mainly on matching an unknown mass spectrum with a spectrum available of NIST (National Institute of Standards and Technology, USA) mass spectral data system or the literature [13, 14]. In a typical chromatogram analyzed for the volatile extracts obtained from goat milk, a total number of 91 components were separated out of which, 63 compounds were positively and 28 tentatively identified. The other constituents could not be identified. Among the identified components in the goat milk of Saanen breed, the largest number of compounds belonged to esters, being 29 compounds, followed by alcohols (13), aldehydes (12), terpenes (11), carboxylic acids (8), ketones (6), lactones (5), aromatics (5) and sulfur compounds (2).

Others authors like Sant’Ana et al. [16], Queiroga et al. [6] and Siefarth and Buettner reported the presence of 19, 174 and 54 compounds, respectively. The main compounds identified in this study, such as hexanol (9481.92 µg/L), pentanoic acid (3040.08 µg/L), 2-pentanone (1651.03 µg/L) were previously reported by these authors. However, in this paper we are reporting the presence of the following compounds in goat milk: Esters (isobutyl acetate, isopropyl butanoate, ethyl tridecanoate, butyl 10-undecenoate, isoamyl cinnamate, benzyl benzoate, butyl dodecanoate, isopropyl tetradecanoate, methyl (Z)-9-hexadecenoate, octadecanol acetate, butyl heptadecanoate), alcohols (2-methyl-1-hexanol, tridecanol, 1,2-dodecanediol, pentadecanol), terpenes (cumene, camphor, β-ionone, β-farnesene, cubenol, α-cadinol, farnesol), ketone (2,3-hexanedione), sulfur compounds (butanethiol, 2-methylthiophene). The prominent sulfur compound found in milk is dimethyl trisulfide that has been reported previously as a flavor compound in both yogurt and cow’s milk [15]. However, in this work on goat’s milk, the presence of 2-methylthiophene (23.46 µg/L) was detected and its presence was reported by Bendall [15] in cow milk and products like yogurt.

The volatile compounds identified which were in higher concentrations in goat milk were hexanol (9481.92 µg/L), pentanoic acid (3040.08 µg/L), 2-pentanone (1651.03 µg/L), methyl 9-octadecenoate (1613.88 µg/L), methyl hexadecanoate (1060.61 µg/L) and 2-pentanol (1683.28 µg/L). Fedele et al. [3] reported the dominant presence of terpenes such as β-caryophyllene and α-copaene. However in this work on goat’s milk, these compounds were not found, although other terpenic compounds such as β-farnesene (80.16 µg/L), α-terpinene (31.28 µg/L), β-ionone (26.39 µg/L), δ-cadinene (23.46 µg/L), α-cadinol (20.53 µg/L) and α-pinene (12.71 µg/L) were found. The presence of terpenes in milk are related to the animal diet, since such compounds can pass from the plants to the milk and can be used as biomarkers in a feeding animal system (Sant’Ana et al., 2019). The goat milk from the breed Saanen grown in the Northeast region of Brazil had more presence of terpenes, which is related to animals feeding with a forage support of Tiffton hay.

Compounds

LRIexp.

LRIlit.

Concentration in milk (µg/L)

Odor notes

Carboxylic acids

3-methylbutanoic acid

860

875

50.83 ± 10.24

cheesy, dairy

pentanoic acid

897

900

3040.08 ± 612.15

cheesy, milky

heptanoic acid

1088

1085

591.40 ± 80.11

cheesy, waxy

octanoic acid

1198

1197

493.65 ± 76.09

fatty, rancid

dodecanoic acid

1526

1529

11.73 ± 2.00

fatty, coconut

pentadecanoic acid

1827

1842

145.65 ± 23.51

-

heptadecanoic acid

2058

2059

212.12 ± 12.72

-

octadecanoic acida

2168

2164

139.78 ± 33.44

odorless, mild fatty

Esters

butyl acetate

816

816

2.219 ± 0.17

fruity, banana

isobutyl acetatea*

823

782

171.07 ± 14.29

fruity, sweet, banana

isopropyl butanoate*

827

820

66.47 ± 5.78

fruity, pineapple

methyl hexanoate

911

911

201.37 ± 21.36

fruity, sweet

ethyl hexanoate

1000

1000

30.30 ± 2.99

fruity, sweet

butyl butanoate

1003

1002

91.89 ± 17.18

fruity, banana

ethyl octanoate

1193

1201

43.99 ± 9.35

fruity, waxy, sweet

methyl nonanoate

1266

1227

20.53 ± 2.97

fruity, sweet, pear

ethyl nonanoate

1297

1296

11.73 ± 1.62

fruity, sweet, waxy

ethyl tridecanoate*

1698

1695

66.47 ± 8.03

-

butyl 10-undecenoatea*

1663

1660

4.89 ± 0.51

fatty, buttery

methyl tetradecanoate

1721

1722

160.31 ± 21.21

fatty, balsamic

isoamyl cinnamate*

1732

1719

4.89 ± 0.82

floral, cocoa

benzyl benzoate*

1744

1757

110.46 ± 25.88

sweet balsamic oily

butyl dodecanoate*

1771

1772

99.71 ± 16.07

-

isopropyl tetradecanoate*

1797

1813

32.26 ± 2.18

-

ethyl tetradecanoate

1801

1803

274.68 ± 54.07

waxy, sweet

methyl (Z)-9-hexadecenoatea*

1891

1890

107.53 ± 34.62

-

methyl hexadecanoate

1925

1925

1060.61 ± 81.62

waxy, fatty, oily

butyl tetradecanoate

1979

1977

138.81 ± 20.73

oily, fatty

methyl heptadecanoate

2024

2028

311.83 ± 15.45

-

butyl pentadecanoate

2079

2080

409.58 ± 69.36

-

methyl 9-octadecenoatea

2098

2087

1613.88 ± 173.04

-

methyl octadecanoate

2122

2123

745.85 ± 53.85

oily, waxy

ethyl 9-octadecenoate

2158

 

907.14 ± 89.01

-

butyl hexadecanoate

2181

2174

186.71 ± 13.77

-

ethyl octadecanoate

2197

2197

443.79 ± 79.42

waxy

octadecanol acetatea*

2216

2209

115.35 ± 10.39

-

butyl heptadecanoate*

2285

2269

86.00 ± 27.01

-

Alcohols

2-methyl-1-propanola

643

647

7.82 ± 1.34

etheral, winey

butanol

656

655

575.76 ± 36.11

fermented, sweet

2-pentanol

700

700

1683.28 ± 242.48

fermented, sweet

hexanol

861

863

9481.92 ± 802.13

herbal, alcoholic

2-methyl-1-hexanola*

886

886

24.44 ± 2.56

-

heptanol

931

946

28.35 ± 1.78

green, herbal

benzyl alcohol

1082

1082

86.00 ± 23.18

green, rose

tridecanola*

1599

1586

79.18 ± 25.39

musty

1,2-dodecanediola*

1753

 

52.79 ± 13.63

-

pentadecanol*

1786

1789

151.52 ± 32.2

-

hexadecanol

1844

1841

553.27 ± 75.03

waxy, floral

heptadecanol

1986

1982

267.84 ± 49.12

-

octadecanol

2089

2089

543.50 ± 67.42

-

Aldehydes

pentanal

695

698

402.74 ± 54.15

fermented, fruity

hexanal

797

798

2.93 ± 0.73

green, fresh

(E)-2-hexenal

859

856

1231.67 ± 156.45

green, banana

heptanal

888

882

69.40 ± 6.90

green, fresh, fatty

octanal

987

983

56.70 ± 8.83

waxy, citrus

nonanal

1100

1103

30.30 ± 4.61

waxy, rose

decanal

1201

1202

8.80 ± 1.78

sweet, waxy

pentadecanal

1704

1701

37.15 ± 2.00

fresh, waxy

hexadecanal

1813

1815

85.04 ± 16.47

cardboard

heptadecanal

1908

1903

61.58 ± 9.01

-

9-octadecenala

2004

1999

529.81 ± 35.35

fatty

octadecanal

2031

2024

409.56 ± 80.93

oily

Terpenes

cumenea*

920

920

4.89 ± 1.09

-

α-pinene

933

931

12.71 ± 1.21

herbal

α-terpinene

1016

1017

31.28 ± 5.66

-

camphora*

1141

1146

9.78 ± 3.17

campherous

β-ionone*

1450

1462

26.39 ± 6.12

floral, sweet

β-farnesenea*

1464

1462

80.16 ± 9.59

 

γ-cadinenea

1543

1543

4.89 ± 0.43

 

δ-cadinenea

1552

1522

23.46 ± 5.27

 

cubenol*

1647

1642

4.03 ± 0.78

spicy, green, herbal

α-cadinola*

1674

1676

20.53 ± 4.82

 

farnesol*

1712

1710

9.77 ± 1.89

 

Lactones

δ-undecalactonea

1572

1579

156.40 ± 28.33

 

γ-dodecalactonea

1657

1655

4.89 ± 1.02

lactone; fruity

δ-dodecalactone

1686

1677

20.53 ± 2.14

sweet, fruity

γ-hexadecalactonea

2147

 

61.58 ± 11.78

 

δ-hexadecalactonea

2165

2154

254.15 ± 40.37

lactone; smooky

Ketones

2-pentanone

682

684

1651.03 ± 309.21

fruity, sweet

2,3-hexanedionea*

794

781

24.44 ± 1.29

buttery, caramelic

2-heptanone

880

882

9.77 ± 0.11

cheesy, spicy, fruit

2-pentadecanone

1709

1702

61.58 ± 13.27

floral, jasmin, fatty

2-hexadecanone

1809

1809

123.17 ± 35.00

fruity

benzophenonea

1594

1590

9.78 ± 2.09

 

Aromatics

toluenea

760

760

120.23 ± 12.71

sweet

ethylbenzenea

857

857

78.20 ± 10.13

-

m-ethyltoluenea

956

957

9.78 ± 2.54

-

p-ethyltoluenea

963

963

1.96 ± 0.02

-

phenola

979

979

1.95 ± 0.91

phenolic

Compostos Sulfurados

butanethiol*

710

713

14.66 ± 3.15

sulfurous, roasted

2-methylthiophene*

775

773

23.46 ± 5.30

 milk, cooked vegetables

LRIExp-Linear retention index experimental; LRILit-Linear retention index literature; a-Tentatively identified compounds; *-Compounds reported for the first time in this work on goat milk aroma

Table 1: Volatile compounds identified in goat milk along with their characteristic odor notes.

There are various chemical and biochemical routes for generation of aroma compounds. The free fatty acids are formed due to the enzymatic processes involving lipase action which hydrolyzes and produces short chain fatty acids. A series of 2-ketones such as 2-pentanone, 2-pentadecanone, 2-heptanone and 2-hexadecanone have been found in fresh milk, which are produced from β-ketoacid glycerides by hydrolytic and decarboxylation mechanism. In this study a very high concentration of 2-pentanone (1651.03 µg/L) was found in milk. The oxidative flavor of milk fat is originated, primarily from linoleic and linolenic acids and gets substantiated by other polyunsaturated fatty acids. Twelve aldehydes (pentanal, hexanal , (E)-2-hexenal, heptanal, octanal, nonanal, decanal, pentadecanal, hexadecanal, heptadecanal and 9-octadecenal) were detected in goat milk. The main aldehyde concentration was that of (E)-2-hexenal (1231,67 µg/L). However, Sant’Ana et al. [16] could not find any aldehyde when analyzing goat milk volatiles. In general, aldehydes are formed by oxidative processes involving microorganisms and enzymes like lipoxygenase [17].

3.2 Key volatile aroma compounds in goat milk

Table 2 lists the key volatile compounds which had odor activity values (OAV) higher than 1 and hence considered to contribute to the overall aroma in the goat milk matrix. The volatile compounds hexanol and (E)-2-hexenal are known to be associated with the formation of rancid odor while 2-pentanone contributes to a strong fatty odor. Methyl 9-octadecenoate and isopropyl tetradecanoate are known to be the principal compounds responsible for the odor of goat milk. According to OAV’s the most important compounds contributing to goat milk aroma were decanal (88), (E)-2-hexenal (72), hexanol (47), octanal (40), ethyl hexanoate (35), pentanal (34), nonanal (30), 2-pentanone (24), heptanal (23), methyl hexanoate (20), γ-dodecalactone (11), 2-heptanone (10), heptanol (9), ethyl octanoate (9), 2-pentadecanone (9), β-ionone (8), α-pinene (5), 2-methylthiophene (5), octadecanal (5). In the sensorial analysis of goat milk, Sant’Ana et al. [16] reported the principal odor notes that characterized goat milk were “buttery” and “herbaceous”. In this work hexanol, heptanol and α-pinene were detected which have high OAV’s and their odor notes are characterized as “herbal”. Other compounds with odor notes similar to “buttery” found in this work, and which also possessed a high OAV’s were aldehydes like heptanal, decanal, octanal and nonanal that have odor notes classified as “fatty” and “waxy”.

Yang et al. [1] reported that “goaty” aroma in goat milk is due to presence of straight-chain fatty acids like C6:0 to C9:0 and some branched-chain C9:0 and C10:0 and that its participation in aroma depend mainly on their concentrations. In this study on aroma profile of goat milk, the compounds which had OAV>1 were octanoic acid (C8:0) (3), pentanoic acid (C5:0) (3), heptanoic acid (C7:0) (1) characterizing with odor notes of “cheesy”, “fatty”, “rancid” and “milky”. In other publications, hexanoic acid (C6:0) is described as having pungent, goaty, sweaty, and blue cheese flavor notes; octanoic acid has waxy, soapy, goaty, musty, rancid, and fruity notes; and decanoic acid (C10:0) is described as soapy, bitter, goaty and rancid notes.

In this study, lactones which could contribute to the characteristic aroma of goat milk were γ-dodecalactone (11), δ-dodecalactone (4), δ-hexadecalactone (1). For goat milk, Sienfart and Buettner [18] reported the presence of γ-octalactone, γ-nonalactone, δ-nonalactone, δ-decalactone, γ-undecalactone and γ-dodecalactone as potent odor participants in goat milk aroma. Bendall, [15] also described these compounds as responsible for fruity and sweet characteristics in cow milk aroma. According to Chilliard [2], the compounds which contribute to milk flavor formation could be classified according to their origin: compounds originated from animal metabolism and/or feed forage, compounds produced by chemical reactions, enzymatic activity or from microbial flora before its processing, compounds generated by thermal treatment or the ones developed during storage. Although interpreting the characteristic aroma of foods is an extremely complex matter, the initial step is to identify the odor-impact compounds and then to evaluate the concentration of the major compounds present in the matrix.

Compounds

Concentration in milk (µg/L)

Odor Threshold (µg/L in Water)

OAV

Odor notes

decanal

8.80 ± 1.78

0.1a

88

sweet, waxy

(E)-2-hexenal

1231.67 ± 156.45

17a

72

green, banana

hexanol

9481.92 ± 802.13

200b

47

herbal, alcoholic

octanal

56.70 ± 8.83

1.4b

40

waxy, citrus

ethyl hexanoate

30.30 ± 2.99

0.87c

35

fruity, sweet

pentanal

402.74 ± 54.15

12a

34

fermented, fruity

nonanal

30.30 ± 4.61

1a

30

waxy, rose

2-pentanone

1651.03 ± 309.21

70b

24

fruity, sweet

heptanal

69.40 ± 6.90

3a

23

green, fresh, fatty

methyl hexanoate

201.37 ± 21.36

10b

20

fruity, sweet

γ-dodecalactone

4.89 ± 1.02

0.43d

11

-

2-heptanone

9.77 ± 0.11

1b

10

cheesy, spicy, fruit

heptanol

28.35 ± 1.78

3b

9

green, herbal

ethyl octanoate

43.99 ± 9.35

5e

9

fruity, sweet

2-pentadecanone

61.58 ± 13.27

7b

9

jasmin, fatty

β-ionone

26.39 ± 6.12

3.5d

8

floral, sweet

α-pinene

12.71 ± 1.21

2.5b

5

herbal

2-methylthiophene

23.46 ± 5.30

5f

5

-

octadecanal

409.56 ± 80.93

83.1c

5

oily

δ-dodecalactone

20.53 ± 2.14

4.6g

4

-

3-methylbutanoic acid

11.73 ± 2.00

12h

4

cheesy, dairy

isobutyl acetate

171.07 ± 14.29

58c

3

fruity, banana

octanoic acid

591.40 ± 80.11

190i

3

fatty, rancid

pentanoic acid

50.83 ± 10.24

1207g

3

cheesy, milky,

isopropyl butanoate

66.47 ± 5.78

43b

2

fruity, pineapple

hexanal

2.93 ± 0.73

2.4d

1

green, fresh

hexadecanal

85.04 ± 16.47

62c

1

cardboard

butyl butanoate

91.89 ± 17.18

87b

1

fruity, banana

δ-undecalactone

156.40 ± 28.33

150b

1

-

butanol

575.76 ± 36.11

405c

1

fermented, sweet

heptanoic acid

3040.08 ± 612.15

500g

1

cheesy, waxy

methyl hexadecanoate

1060.61 ± 81.62

852c

1

waxy, fatty, oily

aButtery et al. [19]; bBurdock [20]; cPino and Quijano [21]; dCzerny et al. [22]; eSaberi et al. [23]; fPuvipirom and Chaiseri [24]; gKaragul-Yuceer et al. [25]; gOng and Acree [26]; iWagner et al. [27].

Table 2: Key volatile compounds (OAV>1) present in goat milk along with their characteristic odor notes.

Sieffart and Buettner [18] reported that six compounds were associated with goat-like odor characteristics accompanied by the attributes stable-like, fecal, or leather-like, and these were saturated acids like nonanoic acid, decanoic acid, dodecanoic acid. Although these compounds were found in the volatile profile of goat milk analyzed in this study, but they characterized for lower aroma impact as these compounds had their OAV’s less than 1. Sieffart and Buettner [18] classified 3-methylbutanoic acid as a potent odorant in goat milk with notes as “sweety” and “cheesy”; in this study the same compound was found having OAV of 4, and hence corroborates with authors previously published work.

4. Conclusion

This work reports the presence of main volatile compounds identified in milk obtained from Saanen breed of goat, grown in the northeast region of Brazil. A total of 91 volatile compounds were identified and a majority of them belonged to esters, alcohols, aldehydes and terpenes. The work also reports the most promising odorous compounds viz. decanal (88), (E)-2-hexenal (72), hexanol (47), octanal (40), ethyl hexanoate (35), pentanal (34), nonanal (30), 2-pentanone (24), heptanal (23), methyl hexanoate (20), γ-dodecalactone (11), 2-heptanone (10), heptanol (9), ethyl octanoate (9), 2-pentadecanone (9), β-ionone (8), α-pinene (5), 2-methylthiophene (5), octadecanal (5), which could be responsible for goat milk aroma and its over-all flavor.

Acknowledgements

Authors (MTSLN) gratefully acknowledges the financial support in the form of a post-doc fellowship received from CAPES (Ministry of Education, Brazil).

Notes

The authors declare that there is no conflict of interest.

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