Sensomics-Assisted Elucidation of the Tastant Code of Cooked

Jan 21, 2016 - combinatorial tastant code provides the foundation for the development of more sophisticated crustacean ..... column (Waters, Mancheste...
0 downloads 0 Views 1MB Size
Subscriber access provided by La Trobe University Library

Article

Sensomics-Assisted Elucidation of the Tastant Code of Cooked Crustaceans and Taste Reconstruction Experiments Andreas Dunkel, Stefanie Meyer, and Thomas Hofmann J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.5b06069 • Publication Date (Web): 21 Jan 2016 Downloaded from http://pubs.acs.org on January 27, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 49

Journal of Agricultural and Food Chemistry

1

1

Sensomics-Assisted Elucidation of the Tastant Code of

2

Cooked

3

Experiments

Crustaceans

and

Taste

Reconstruction

4 5 6

Stefanie Meyer1, Andreas Dunkel1,2 and Thomas Hofmann1,2*

7 8

1

Chair of Food Chemistry and Molecular and Sensory Science, Technische

9

Universität München, Lise-Meitner-Str. 34, D-84354 Freising, Germany, and

10 2

11

Bavarian Center for Biomolecular Mass Spectrometry, Gregor-Mendel-Straße 4, D-85354 Freising, Germany.

12

13 14 15 16 17 18 19 20

*

To whom correspondence should be addressed

21

PHONE

+49-8161/71-2902

22

FAX

+49-8161/71-2949

23

E-MAIL

[email protected]

24 25

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

26

ABSTRACT

27 28

Sensory-guided fractionation by means of ultrafiltration and cation exchange

29

chromatography, followed by MS/MS quantitation, and taste re-engineering

30

experiments revealed the key taste molecules coining the characteristic taste profile

31

of the cooked meat of king prawns. Furthermore, quantitative analysis demonstrated

32

that the taste differences between crustaceans are due to quantitative differences in

33

the combinatorial code of tastants, rather than to qualitative differences in the tastant

34

composition. Besides the amino acids glycine, L-proline, and L-alanine, the

35

characteristic seafood-like sweet profile was found to be due to the sweet modulatory

36

action of quaternary ammonium compounds, amongst which betaine, homarine,

37

stachydrin, and trimethylamine-N-oxide were found as the key contributors on the

38

basis of dose-activity considerations. The knowledge of this combinatorial tastant

39

code sets the ground for the development of more sophisticated crustacean flavors

40

that are lacking any heavy metal ions and allergenic proteins present when using

41

crustacean extracts for food flavoring.

42 43 44

Key Words: taste, taste dilution analysis, taste enhancer, prawns, lobster, seafood

45 46 47 48 49 50 51

ACS Paragon Plus Environment

Page 2 of 49

Page 3 of 49

Journal of Agricultural and Food Chemistry

52

INTRODUCTION

53

Due to their alluring aroma profile and their attractive taste centering around a

54

unique sweet-umami balance, cooked crustaceans such as, e.g. shrimps, lobster or

55

king prawns, are intimately linked with a very delicious product in consumers’ minds.

56

Whereas a vast number of studies have been focused in the past on the elucidation

57

of the volatile chemical odor code of foods and beverages,1 the knowledge on the

58

chemical structures and sensory properties of the non-volatile key taste (modulating)

59

molecules in crustaceans is still rather limited.

60

Among the non-volatile constituents, amino acids, nucleotides, organic acids, and

61

minerals were reported as contributors to the taste of fresh as well as thermally

62

processed meat of crustaceans.2-5 Inosine-5ʹ-monophosphate (IMP), adenosine-5ʹ-

63

monophosphate (AMP), and L-glutamic acid have been reported as key molecules

64

determining the characteristic umami taste of crustacean meat,6-7 whereas the typical

65

sweet profile of crustaceans such as, e.g. boiled snow and Chinese mitten crab, has

66

been proposed to be elicited by the amino acids glycine, L-proline, and L-alanine, as

67

well

68

trimethylethanolamine (choline, 2), N-methylpipecolinic acid (homarine, 3), and N-

69

trimethylglycine (betaine, 4), Figure 1, were identified in seafood like crabs, scallop,

70

and lobster,2,8-13 however, their sensory impact remains largely unclear. Only betaine

71

has been reported to affect the sweet profile of seafood,2,14 and to enhance the

72

glycine- and L-alanine-induced response of the amino acid taste receptor in fish.15-17

as

sodium

ions.2,6,8-9

Moreover,

trimethylamine-N-oxide

(1),

N-

73

Driven by the need to discover the key players imparting the typical taste of foods,

74

the research area “sensomics” has made tremendous efforts in recent years in

75

mapping the comprehensive population of sensory active, low-molecular weight

76

compounds, coined sensometabolome, and cataloging, quantifying, and evaluating

77

the sensory activity of metabolites which are present in raw materials and/or are ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 4 of 49

78

produced upon food processing and storage, respectively.18-20 Aimed at decoding the

79

typical taste signature of food products on a molecular level, the so-called taste

80

dilution analysis (TDA) was developed as an efficient screening tool enabling the

81

sensory-directed identification of the comprehensive population of taste-active

82

sensometabolites in foods and beverages such as, e.g. black tea infusions,21 red

83

wine,22 chicken broth,23 and Gouda cheese.24 Moreover, the sensomics approach

84

accomplished the discovery of a series of taste-modulating molecules generated

85

upon food processing by means of “kitchen-type” chemistry such as, e.g. (S)-

86

alapyridaine in beef broth,25 N-(1-methyl-4-oxoimidazolidin-2-ylidene) α-amino acids

87

in stewed beef juice,26 γ-glutamyl dipeptides in matured Gouda cheese,27 N2-lactoyl-

88

guanosine

89

carboxyethyl)guanosine 5’-phosphate in yeast extracts,29 and 5-acetoxymethyl-2-

90

furaldehyde in traditional balsamic vinegar.30

5’-monophosphate

in

fermented

tuna

fish,28

(S)-N2-(1-

91

As the entire nonvolatile sensometabolome of crustacean meat has not yet been

92

fully investigated, the objective of the present investigation was to identify and

93

quantify taste active and taste modulatory compounds in the cooked meat of king

94

prawns (Litopenaeus vannamei), to rank them in their sensory impact based on

95

dose-activity considerations, and to validate their sensory relevance by means of

96

taste re-engineering experiments. Finally, quantitative monitoring of selected taste

97

compounds in cooked lobster (Homarus americanus) and Norway lobster (Nephros

98

norvegicus) should visualize species differences in the combinatorial code of taste

99

molecules.

100 101 102

MATERIALS AND METHODS

ACS Paragon Plus Environment

Page 5 of 49

Journal of Agricultural and Food Chemistry

103

Chemicals and Materials. The following chemicals were purchased from the

104

sources given in parentheses: L-amino acids, organic acids, inorganic salts,

105

nucleosides, nucleotide phosphates, trigonelline hydrochloride, trimethyllysine

106

hydrochloride,

107

iodomethane-d3, picolinic acid (Sigma-Aldrich, Steinheim, Germany); γ-L-glutamyl

108

dipeptides (Bachem, Weil am Rhein, Germany); hydrochloric acid, petrol ether, silver

109

oxide, formic acid (Merck, Darmstadt, Germany); betaine anhydrous, choline

110

chloride, trimethylamine N-oxide dihydrate (TMAO), ammonium hydroxide solution

111

(25%) (Fluka, Neu-Ulm, Germany). Stable isotope labeled compounds such as amino

112

acids, nucleotides, betaine-d11, and choline-d9 used for stable isotope dilution assays

113

(SIDA) were purchased from Cambridge Isotope Laboratories, Inc. (Tewksbury, MA,

114

USA). Solvents were of high-performance liquid chromatography (HPLC) grade (J.T.

115

Baker, Deventer, Netherland), and deuterated solvents were supplied by Euriso-Top

116

(Saarbrücken, Germany). Deionized water used for chromatography was prepared

117

by means of a Milli-Q water gradient A 10 system (Millipore, Schwalbach, Germany).

118

For sensory analysis, bottled water (Evian) was adjusted to pH 6.8 with trace

119

amounts of formic acid. Deep-frozen samples of king prawns (Penaeus vannamei)

120

from aquacultures and Norway lobster (Nephros norvegicus) from the North Atlantic,

121

both containing head and shell, as well as lobster tails (Homarus americanus) from

122

the Northwest Atlantik were obtained commercially from a local vendor.

trifluoroacetic

acid,

chloramine-T

trihydrate,

iodomethane,

123

Kitchen-type Preparation of Cooked King Prawns, Lobster, and Norway

124

Lobster. Deep-frozen crustaceans were thawed by maintaining them for 1.5 h at

125

room temperature. Four king prawns and four Norway lobsters, respectively, were

126

blanched in hot water (4 L, 90°C) for 1 min, while the lobster tail was cooked in water

127

(4 L) for 3 min at 100°C. After cooling to room temperature, intestines and the

128

carcasses were removed. ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

129

Preparation of Crustacean Extracts. Portions (100 g) of crustacean meat were

130

homogenized with water/methanol (80/20, v/v; 200 mL) for 3 min by means of an

131

Ultra-Turrax T 25 basic (Ika Labortechnik, Stauffen, Germany) and, after

132

centrifugation at 9000 rpm for 20 min at 7 °C (Avanti J-E, Beckmann-Coulter, Krefeld,

133

Germany), the residues were re-extracted with water/methanol (80/20, v/v; 100 mL),

134

centrifuged as described above, and lyophilized using a Christ Delta 1-24 LSC

135

freeze-dryer (Martin Christ Gefriertrocknungsanlagen GmbH, Osterode, Germany) to

136

give the non-soluble fraction of king prawns (yield: ~22% of cooked fresh weight),

137

lobster (yield: ~20%), and Norway lobster (yield: ~18%). The pooled liquid

138

supernatants were separated from solvent in vacuum and freeze-dried to give the

139

extracts of king prawns (yield: ~8% of cooked fresh weight), lobster (yield: ~7%), and

140

Norway lobster (yield: ~8%). All fractions were stored at -20 °C until further analysis.

141

Stirred-Cell Ultrafiltration. An aliquot (2 g) of the king prawn soluble extract was

142

dissolved in water (200 mL) and separated into a low molecular (KPLMW; < 1kDa;

143

80% yield) and a high molecular weight fraction (KPHMW; ≥ 1kDa; 20% yield) using an

144

Amicon 8400-type ultrafiltration cell (Amicon, Witten, Germany) equipped with a

145

YM1-type cellulose filter (1 kDa cutoff; Millipore, Bedford, MA, USA) at a nitrogen

146

pressure of 0.2 MPa. Both fractions collected from various separations were pooled

147

accordingly and kept at -20 °C until further analysis.

148

Quantitation of Candidate Basic Taste Compounds. Organic acids, Cations,

149

and Anions. Aliquots (100 mg) of the soluble crustacean extracts were dissolved in

150

water (3 mL), membrane filtered (0.45 µm) and without any further dilution (for

151

organic acids) or after 1:10 dilution (anions, cations) analyzed by high-performance

152

ion chromatography using a Dionex IC 2500 system (Dionex, Idstein, Germany)

153

consisting of a GS50 gradient pump, an AS50 autosampler, an AS50 thermal

154

compartment, and an ED 50 electrochemical detector following the protocol reported ACS Paragon Plus Environment

Page 6 of 49

Page 7 of 49

Journal of Agricultural and Food Chemistry

155

recently.24 For cation analysis, a Dionex ICS-2000 apparatus was used with a digital

156

conductivity detector, a CSRS 300 suppressor cell, an AS autosampler, and an

157

eluent generator equipped with a RFIC EluGen cartridge EGC II MSA (Dionex,

158

Idstein, Germany). Data analysis was performed using the Chromeleon software

159

6.80. The quantitative data are given as the mean of four replicates (RSD for each

160

data point