Evaluation of umami taste in mushroom extracts by chemical analysis, sensory evaluation, and an electronic tongue system

Accepted Manuscript Evaluation of umami taste in mushroom extracts by chemical analysis, sensory evaluation, and an electronic tongue system Chanvorleak Phat, BoKyung Moon, Chan Lee PII: DOI: Reference:

S0308-8146(15)01146-2 http://dx.doi.org/10.1016/j.foodchem.2015.07.113 FOCH 17909

To appear in:

Food Chemistry

Received Date: Revised Date: Accepted Date:

20 April 2015 29 June 2015 22 July 2015

Please cite this article as: Phat, C., Moon, B., Lee, C., Evaluation of umami taste in mushroom extracts by chemical analysis, sensory evaluation, and an electronic tongue system, Food Chemistry (2015), doi: http://dx.doi.org/ 10.1016/j.foodchem.2015.07.113

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

1

Evaluation of umami taste in mushroom extracts by chemical analysis, sensory evaluation,

2

and an electronic tongue system

3 4

Running title: Umami taste in mushroom extracts

5

Chanvorleak Phata, BoKyung Moonb, Chan Leea,*

6 7 8 9 10

a

School of Food Science and Technology, Chung-Ang University, Anseong-Si, Gyeonggi-Do 456-756,

11 12

Republic of Korea b

Department of Food and Nutrition, Chung-Ang University, Anseong-Si, Gyeonggi-Do 456-756,

13

Republic of Korea

14 15 16 17 18 19 20

*Corresponding author:

21

Department of Food Science and Technology, Chung-Ang University, Anseong-Si, Gyeonggi-Do

22

456-756, Republic of Korea

23

Phone: +82-31-670-3035

24

Fax: +82-31-676-8865

25

E-mail: [email protected] 1

26

ABSTRACT

27 28

Seventeen edible mushrooms commercially available in Korea were analysed for their

29

umami taste compounds (5′-nucleotides: AMP, GMP, IMP, UMP, XMP; free amino acids:

30

aspartic, glutamic acid) and subjected to human sensory evaluation and electronic tongue

31

measurements. Amanita virgineoides featured the highest total 5′-nucleotide content (36.9 ±

32

1.50 mg/g), while monosodium glutamate-like components (42.4 ± 6.90 mg/g) were highest

33

in Agaricus bisporus. The equivalent umami concentration (EUC) ranged from 1.51 ± 0.42 to

34

3890 ± 833 mg MSG/g dry weight; most mushrooms exhibited a high umami taste. Pleurotus

35

ostreatus scored the highest in the human sensory evaluation, while Flammulina velutipes

36

obtained the maximum score in the electronic tongue measurement. The EUC and the sensory

37

score from the electronic tongue test were highly correlated, and also showed significant

38

correlation with the human sensory evaluation score. These results suggest that the electronic

39

tongue is suitable to determine the characteristic umami taste of mushrooms.

40 41

Keywords: mushrooms, umami taste, equivalent umami concentration, sensory evaluation,

42

electronic tongue

43 44 45 46 47 48 49 50 2

51

1. Introduction

52 53

Mushrooms have been used as food and traditional medicines in Asia for centuries

54

(Kalač, 2012). Generally, mushrooms contain about 57% carbohydrates, 25% protein, 5.7%

55

fat, and 12.5% ash (Kalač, 2009). Moreover, mushroom proteins include all the essential

56

amino acids that cannot be synthesised by our body and therefore must be supplied with the

57

diet. The total fat content of mushroom is low and features a high proportion of

58

polyunsaturated fatty acids, ranging from 72 to 85% (Kalač, 2012). In addition, the strong

59

flavour and taste of mushroom contribute to their extensive consumption as raw food,

60

functional food, and seasoning (Khan, Khan, Hossain, Tania & Uddin, 2011).

61

The characteristic flavour substances or umami tastes in mushrooms, which represent

62

the basic tastes enhanced by free amino acids and 5´-nucleotides, can be analysed as volatile

63

and non-volatile components (Li, Gu, Yang, Zhou, Liu & Zhang, 2014) by high-performance

64

liquid chromatography (HPLC) and other methods. “Umami” was coined as a term for

65

savoury and delicious taste, and was recognised as a basic taste typified by the amino acid

66

glutamic acid and its salt monosodium glutamate (MSG), which yield a savoury, brothy, rich,

67

or meaty taste sensation (Yamaguchi, 1991). The free amino acids, glutamic acid and aspartic

68

acid, and the 5´-nucleotides, inosine 5´-monophosphate and guanosine 5´-monophosphate,

69

were later identified as the main umami substances. Umami substances are naturally found in

70

a variety of foods, including meat, cheese, seafood and vegetables, and they are the

71

predominant flavour substances of mushrooms (Yamaguchi, 1991). Water-soluble taste

72

components, such as free amino acids and 5´-nucleotides, make an important contribution to

73

the typical mushroom flavour (Dermiki, Phanphensophon, Mottram & Methven, 2013) and

74

the combination of free amino acids gives rise to a unique natural flavour (Mau, 2005).

75

Human sensory evaluation has been employed for the determination of the umami 3

76

tastes in mushrooms. Chemical analysis by HPLC offers quantitative data that cannot be

77

explained in terms of overall taste, because this method detects each taste substance

78

separately and cannot reveal taste–substance interactions such as synergistic and suppression

79

effects (Kobayashi, Habara, Ikezazki, Chen, Naito & Toko, 2010). On the other hand, sensory

80

evaluation provides integrated, direct measurements of perceived intensities of target

81

attributes, such as appearance, colour, aroma, taste, and texture (Bleibaum, Stone, Tan,

82

Labreche, Saint-Martin & Isz, 2002). Nevertheless, sensory evaluation is time-consuming,

83

expensive, and might vary depending on daily conditions. Thus, a new method has been

84

developed for the evaluation of many tastes at the same time, using only a taste sensor itself

85

(Tran, Suzuki, Okadome, Homma & Ohtsubo, 2004). These methods can integrate predictive

86

relationships between sensory and instrumental measurements. The electronic tongue

87

measurement offers satisfactory taste results that are close to a human sensory evaluation

88

(Kobayashi et al., 2010). There has been limited information to date regarding the taste

89

characteristics of mushrooms using the electronic tongue.

90

In the present study, we aimed to evaluate the umami taste properties of various

91

mushroom types available in Korean domestic markets in order to provide a complete range

92

of information, which will be very useful for both consumers and industrial applications in

93

the development of natural seasonings or food additives from mushrooms. For this purpose

94

eight umami components were analysed in mushroom extracts through chemical analysis

95

using a high-performance liquid chromatography (HPLC) and liquid chromatography-tandem

96

mass spectrometry (LC-MS/MS) analysis, and their taste was compared by sensory

97

evaluation. Furthermore, the correlations between the human sensory evaluation scores, the

98

electronic tongue test (taste sensing system TS-5000Z), the levels of umami equivalent

99

concentration, and the level of each umami component were investigated by statistical

100

analysis. 4

101

2. Materials and methods

102 103

2.1. Samples

104

Seventeen commercially available mushroom samples (Agaricus bisporus, Amanita

105

virgineoides, Auricularia auricula-judae, Flammulina velutipes, Grifola frondosa, Hericium

106

erinaceus,

107

citrinopileatus, Pleurotus eryngii, Pleurotus ferulae, Pleurotus ostreatus, Pleurotus

108

salmoneostramineus, Polyozellus multiplex, Ramaria botrytis (Pers.) Ricken, Sparassis

109

crispa, and Tremella fuciformis) were collected from the market or artificially cultivated

110

using strains from Rural Development Administration, Republic of Korea. Fresh mushrooms

111

were immediately freeze-dried, milled using a food blender (HR 2860, Ya Horng Ele. Co.,

112

Ltd, Guan Cuangdong, China), and stored at –20 oC until further analysis.

Hypsizigus

marmoreus,

Lentinus

edodes,

Pleurotus

cornucopiae

var.

113 114

2.2. Standards and reagents

115

5´-Nucleotide standards [adenosine 5´-monophosphate sodium salt (AMP), cytidine 5´-

116

monophosphate disodium salt (CMP), guanosine 5´-monophosphate disodium salt (GMP),

117

inosine 5´-monophosphate disodium salt (IMP), and uridine 5´-monophosphate disodium salt

118

(UMP)] were purchased from Sigma-Aldrich, Yongin, Korea. Xanthosine 5´-monophosphate

119

(XMP) was supplied by Santa Cruz Biotechnology (Santa Cruz, CA). Phosphoric acid 85%

120

was obtained from Sam-Cheon chemicals, Jeollanam, Korea. Methanol and water (HPLC

121

gradient grade) were purchased from Burdick & Jackson, Morristown, NJ. Aspartic acid and

122

glutamic acid were obtained from Junsei Chemical Co., Ltd, Tokyo, Japan and Sigma-

123

Aldrich, Yongin, Korea, respectively.

124 125

2.3. Equipment 5

126

A Gilson HPLC system (Middleton, UK) equipped with a binary pump, vacuum

127

degasser, column oven, UV detector (254 nm), and fluorescence detector (335 and 440 nm

128

excitation and emission wavelengths, respectively) was employed for umami taste

129

measurements. Gemini-NX C18 (5 µm, 4.60 × 250 mm, Phenomenex, Torrance, CA) and

130

Eclipse XDB C18 (5 µm, 4.60 × 150 mm; Agilent, Santa Clara, CA) columns were used for

131

this analysis.

132 133

The electronic tongue measurement was conducted with the taste sensing system TS5000Z (Intelligent Sensor Technology, Inc., Kanagawa, Japan).

134 135

2.4. 5´-Nucleotide assay

136

5´-Nucleotides were extracted and analysed as described by Pei et al. (2014). Freeze-

137

dried mushroom powder (500 mg) was extracted with 50 mL of deionised water. This

138

suspension was heated to boiling for 1 min, cooled, and then centrifuged at 4000 rpm for 30

139

min. The extraction was filtered using a 0.22-µm nylon filter, prior to HPLC analysis.

140

5´-Nucleotides were separated with a Gemini-NX 5 µm C18 (250 × 4.60 mm) column

141

using an isocratic mobile phase of 5% A and 95% B for 40 min (A: methanol and B: 0.05%

142

phosphoric acid) at a flow rate of 0.7 mL/min and UV detection at 254 nm. Each 5´-

143

nucleotide was identified by matching its retention time with that of an authentic standard,

144

and quantified using its respective calibration curve.

145 146

2.5. Free amino acid assay

147

Aspartic acid and glutamic acid were analysed and identified using HPLC according to

148

Pereira, Pontes, Câmara, and Marques (2008). Free amino acids were extracted by

149

suspending 500 mg of homogenised sample powder in 50 mL of 0.1 M HCl and shaking for

150

45 min at ambient temperature, followed by filtration through a Whatman No. 4 filter paper. 6

151

This sample did not exhibit any fluorescence; it was derivatised using o-phthalaldehyde

152

(OPA). OPA derivatisation solution was prepared in a 10-mL flask by dissolving 250 mg of

153

reagent in 1.5 mL ethanol and bringing the volume to 10 mL with 0.4 M borate buffer (pH

154

10.5). Finally, 200 µL of 2-mercaptoethanol were added. The reagent solution was left to

155

settle for 90 min and then stored in dark glass vials at 4 oC; it was freshly prepared every 9

156

days. The derivatisation procedure was performed in the sample injection loop according to

157

the following sequence: 10 µL of buffered sample mixture were transferred to the injection

158

loop followed by 10 µL of OPA solution and maintained for 3 min to promote the

159

derivatisation reaction. The flow rate was set to 1 mL/min and the column temperature was

160

maintained at 35 oC. Mobile phase A contained 1% of tetrahydrofuran, 8% methanol, and 91%

161

phosphate buffer (10 mM), and mobile phase B consisted of 80% methanol and 20%

162

phosphate buffer (10 mM). The gradient program used is shown in the supplemented material.

163 164

2.6. LC-MS/MS

165

LC-MS/MS (LTQ velos, Accela HPLC; Thermo, Waltham, MA) equipped with an

166

electrospray ionisation interface (ESI) was applied to confirm the 5´-nucleotides. A C18

167

analytical column (4.60 × 250 m, Phenomenex, CA, USA) was used for the analysis. The

168

liquid chromatography was performed under isocratic conditions as described in the 5´-

169

nucletide assay. A volume of 20 µL was injected for LC-MS/MS, and the molecular weight of

170

each sample was compared with that of the standards. The mass spectrometer was operated in

171

negative electrospray ionisation (ESI–) mode. Mass spectrometry was carried out in scan

172

mode from m/z 50 to m/z 2000. ESI-MS conditions were as follows: capillary voltage of 3 kV,

173

pressure of nebuliser 40 psi, gas (nitrogen) temperature of 350 oC, cone gas and desolvation

174

gas flows of 50 and 600 L/h, respectively.

175 7

176

2.7. Equivalent umami concentration (EUC)

177

The EUC value (mg MSG/g) reflects the concentration of MSG equivalent to the

178

umami intensity given by a mixture of MSG and 5´-nucleotides and is represented by the

179

following equation (Yamaguchi, 1991)

180

Y = Σaibi + 12.18(Σaibi)(Σajbj),

181

where Y is the EUC of the mixture in mg MSG/g; ai is the concentration (mg/g) of each

182

umami amino acid [aspartic acid (Asp) or glutamic acid (Glu)]; aj is the concentration (mg/g)

183

of

184

monophosphate (5´-GMP), 5´-xanthosine monophosphate (5´-XMP), or 5´-adenoshine

185

monophosphate (5´-AMP)]; bi is the relative umami concentration (RUC) for each umami

186

amino acid to MSG (Glu, 1; Asp, 0.077); bj is the RUC for umami 5´-nucelotide to 5´-IMP

187

(5´-IMP, 1; 5´-GMP, 2.3; 5´-XMP, 0.61; 5´-AMP, 0.18); and 12.18 is a synergistic constant

188

based on the concentration (mg/g) used.

each

umami 5´-nucleotide

[5´-inosine

189

2.8. Sensory evaluations

190

2.8.1. Human sensory evaluation

monophosphate

(5´-IMP),

5´-guanosine

191

Ten trained panellists (8 females and 2 males) aged between 24 and 37 years

192

participated in the sensory evaluation. Based on a screening test, the panellists were selected

193

from graduate students at the Department of Food Science and Nutrition at Chung-Ang

194

University, South Korea. All participants were familiar with umami taste and had previous

195

experience with sensory evaluation. During five 1-hour training sessions, the panellists were

196

trained with different concentrations of MSG solutions (0.03, 0.09, 0.15, 0.21, 0.27, or 0.30

197

g/100 mL) to accustom them to the evaluation scales and the intensity of umami taste of the

198

standard solutions.

199

The sensory evaluation of the samples was performed in triplicate on different days.

200

Sample solutions were prepared by extraction of mushroom powders with boiling water (1% 8

201

w/v) for 5 min. The panellists were presented with 30 mL of each sample together with a

202

glass of warm water, a spit cup for expectoration, a paper napkin, and palate cleansers (white

203

bread) in random order in three different sessions. Five to six samples were served in each

204

session and panellists were given a break between each session. In order to avoid temperature

205

differences, all samples were kept and served at 45 oC. Panellists evaluated the intensity of

206

umami taste using an 11-point scale, where 1 means very weak, 6 means medium, and 11

207

means very strong umami taste (He et al., 2009).

208 209

2.8.2. Electronic tongue measurement

210

The electronic tongue system (taste sensing system TS-5000Z, Japan) consists of

211

reference electrodes, multichannel lipid/polymer membrane electrodes, an auto-sampler, an

212

electronic unit for data acquisition, and a personal computer with an advanced chemometric

213

software package (Intelligent Sensor Technology, Inc., Kanagawa, Japan) (Tran et al., 2004).

214

The response intensity of each sensor was measured with an Ag/AgCl reference electrode,

215

which is the most commonly used in this field (Kobayashi et al., 2010). The potentiometric

216

differences between each coated sensor and the reference electrode contribute to the intensity

217

value of the measured samples (Chen, Zhao & Vittayapadung, 2008).

218

Each sample was measured after the electric potentials of all membranes had been

219

stabilised in standard solutions. These standard solutions were prepared by dissolving the

220

respective compound in 1 L of distilled water, and included a salty solution (0.045 g tartaric

221

acid and 22.37 g potassium chloride), sour solution (0.45 g tartaric acid and 2.24 g potassium

222

chloride dissolved in 1 L of distilled water), umami solution (0.045 g tartaric acid, 2.24 g

223

potassium chloride, and 1.87 g monosodium glutamate), a bitter (+) solution (0.045 g tartaric

224

acid, 2.24 g potassium chloride, and 0.04 g quinine hydrochloride), a bitter (–) solution

225

(0.045 g tartaric acid, 2.24 g potassium chloride, and 100 µL iso-α-acid), and an astringent 9

226

solution (0.045 g tartaric acid, 2.24 g potassium chloride, and 0.05 g tannic acid). Sample

227

solutions were prepared by extraction of mushroom powders with boiling water (1% w/v) for

228

5 min and centrifugation for 10 min at 3000 rpm before analysis.

229 230

2.9. Statistical analysis

231

All assays were carried out in triplicate. The results are expressed as mean ± standard

232

deviation (SD). The experimental data were subjected to analysis of variance for a completely

233

randomised design using Statistical Analysis System software (SAS Institute., Cary, NC,

234

USA, 2002). Spearman’s Rank Correlation statistical treatment was conducted using IBM

235

SPSS Statistics version 21 (SPSS Inc., Chicago, IL). A p-value < 0.05 was considered

236

statistically significant.

237 238

3. Results and discussion

239

3.1. 5´-nucleotides

240

The levels of six 5´-nucleotides were analysed in the mushroom extracts. As shown in

241

Table 1, AMP was detected in 15 out of 17 samples. The highest AMP concentration was

242

measured in an extract from P. salmoneostramineus at 30.9 ± 0.01 mg/g. All seventeen

243

samples contained CMP at a concentration ranging from 0.03 ± 0.03 to 21.1 ± 0.76 mg/g with

244

the extract from Ama. virgineoides exhibiting the highest CMP concentration. IMP was

245

detected in sixteen mushroom samples, with the lowest concentration measured in the extract

246

from Auri. auricular-judae, while P. ostreatus contained the highest IMP level. G. frondosa

247

appeared to have the highest UMP concentration among the tested mushrooms. Only one

248

mushroom, P. cornucopiae var. citrinopileatus, did not contain any UMP in its extract. XMP

249

was detected in all samples except for Aga. bisporus, with concentration ranges of 0.01–4.74

250

± 0.15 mg/g. Interestingly, GMP could not be detected in any of the mushroom samples. 10

251

Yang, Lin, and Mau (2001) reported that L. edodes contains 9.51 to 24.2 mg/g of total

252

5´-nucleotides, and the total 5´-nucleotide content in common mushrooms was around 11.35

253

mg/g; this value was similar to that observed in this study. The total 5´-nucleotide content of

254

P. ostreatus extract has previously been reported in different studies worldwide, but the

255

measured values were very low compared to those in our study; this difference might be

256

related to differences in the cultivation conditions between the samples (Beluhan &

257

Ranogajec, 2011; Tsai, Huang, Lo, Wu, Lian & Mau, 2009; Yang et al., 2001). Lee, Jian and

258

Mau (2009) reported an XMP concentration of 0.56 mg/g in Hyp. marmoreus extract, which

259

is very similar to the results in our study.

260

Tsai et al. (2009) identified GMP, IMP, and XMP as the flavour 5´-nucleotides.

261

Mushroom flavour 5´-nucleotide levels have been reported in several studies, ranging from

262

0.54 to 9.00 mg/g (Yang et al., 2001; Tsai et al., 2009; and Beluhan & Ranogajec, 2011).

263

According to Yang et al. (2001), flavour 5´-nucleotides can be classified as low (<1 mg/g),

264

medium (1–5 mg/g) and high (>5 mg/g). Among the 17 mushroom samples tested here, P.

265

ostreatus, H.

266

nucleotides of 14.8 ± 0.05, 10.3 ± 0.28, and 7.54 ± 0.33 mg/g, respectively. Nine mushroom

267

samples were classified in the medium range and five (Auri. auricular-judae, P. ferulae, P.

268

salmoneostramineus, S. crispa, T. fuciformis) were in the low range. As the umami taste of

269

mushrooms is elevated by the level of flavour 5´-nucleotides, the results suggest that our

270

samples promise a good potential for these mushrooms to be employed as food seasonings or

271

food additives.

erinaceus, and Aga. bisporus possessed the highest levels of flavour 5´-

272 273

3.2. Free amino acids

274

According to Yamaguchi (1991), among all free amino acids, only aspartic acid and

275

glutamic acid contribute to the characteristic umami taste. Therefore, we focused on these 11

276

two amino acids instead of profiling all free amino acids in the mushroom samples. Aspartic

277

and glutamic acid were detected in all samples. The highest aspartic acid concentration was

278

found in Aga. bisporus (18.1 ± 2.57 mg/g), while the highest glutamic acid concentration was

279

detected in Ama. virgineoides (35.0 ± 3.66 mg/g; Table 2). Beluhan and Ranogajec (2011)

280

reported that the combination of aspartic acid and glutamic acid contributed to the MSG-like

281

taste or palatable taste. MSG-like components also affect the EUC levels of mushrooms;

282

those with high concentration of MSG-like compounds tend to have high EUC values as well.

283

All 17 mushrooms tested here exhibited wide ranges of MSG-like levels from 0.94 ± 0.17 to

284

42. 4 ± 6.90 mg/g. Aga. bisporus, P. salmoneostramineus, and Ama. virgineoides featured the

285

highest levels of MSG-like compounds at 42.4 ± 6.90, 41.9 ± 3.57, and 41.8 ± 4.45 mg/g,

286

respectively. Various other studies have reported a high content of MSG-like compounds in

287

other edible mushroom types, such as Craterellus cornucopioides (45.85 mg/g), Phellinus

288

linteus (42.43 mg/g), and P. ostreatus (41.26 mg/g) (Beluhan & Ranogajec, 2011; Liang, Tsai,

289

Huang, Liang & Mua, 2010). The MSG-like components in common mushrooms were

290

previously measured at 11.44 mg/g of dry weight (Zhang, Venkitasamy, Pan & Wang, 2013).

291

Tsai, Weng, Huang, Chen and Mau (2006) determined the level of MSG-like compounds in G.

292

frondosa as 6.51 mg/g, which was lower than the results in our study.

293 294

3.3. LC-MS/MS

295

The LC-MS/MS full-scan negative electrospray ion (ESI–) mass spectra for 5´-

296

nucleotides are shown Fig. 1. The mass spectra for CMP, AMP, UMP, IMP, XMP, and GMP

297

showed the protonated molecular ion at m/z 322, 346, 323, 347, 363, and 344, respectively.

298

5´-Nucleotides detected by HPLC were analysed by additional LC-MS/MS and compared

299

with protonated molecular ions of the standards (Supplemented material). According to

300

Lorenzetti, Lilla, Donato and Nucci (2007), the negative-ion mode of ESI-MS seems to be a 12

301

logical starting point for nucleotide analysis because of the presence of one or more

302

negatively charged phosphate groups in the molecules. In their study, the m/z values of AMP

303

and GMP were 348.10 and 364.10, respectively. Mateos-Vivas, Rodriguez-Gonzalo,

304

Dominguez-Alvarez, Garcia-Gomez, Ramirez-Bernabe, and Carabias-Martinez (2015) also

305

reported that the mass-to-charge ratio for AMP was m/z 361, and that for UMP was m/z 334.

306

In a study by Yang, Li, Feng, Hu and Li (2010), it was reported that AMP, GMP, and UMP

307

are corresponding to mass-to-charge m/z 348, 364, and 325, respectively. These findings were

308

similar to the results of our present study. Comparable results were also reported by Wang et

309

al. (2010) and Yamaoka et al. (2010).

310 311

3.4. Equivalent umami concentration (EUC)

312

According to Mau (2005), the EUC values can be grouped into four levels as : (1)

313

>10,000 mg/g dry weight, (2) 1000–10,000 mg/g dry weight, (3) 100–1000 mg/g dry weight,

314

and (4) <100 mg/g dry weight, corresponding to >10, 1–10, 0.1–1 and <0.1 g MSG/g,

315

respectively. As demonstrated in Table 2, the EUC values of the mushrooms determined here

316

ranged from 1.51 ± 0.42 mg MSG/g dry weight in Auri. auricula-judae to 3890 ± 833 mg

317

MSG/g dry weight in P. ostreatus. Six mushroom samples were classified as level (2), and

318

five and six mushrooms samples as levels (3) and (4), respectively. In the study by Beluhan

319

and Ranogajec (2011), the EUC levels of P. ostreatus and F. velutipes were measured at

320

1505.5 ± 21.9 and 737.8 ± 9.1 mg MSG/g, respectively. These results were comparable to

321

those in the present study. Although previous reports have evaluated the EUC levels of

322

mushrooms, only a few mushrooms were evaluated in each study (Cho, Choi & Kim, 2010;

323

Lee, Jian & Mau, 2009). In contrast, our study provided complete information related to the

324

umami taste from a wide range of mushroom samples. Thus, the calculated EUC values in

325

this study will prove helpful for the consideration of these mushrooms as food additives or 13

326

food seasoning components.

327 328

3.5.Sensory evaluations

329

3.5.1. Human sensory evaluation

330

A sensory evaluation was also performed to measure umami intensity in all mushroom

331

samples. Significant differences in the umami taste intensity among the samples were

332

observed (p < 0.05). Table 3 shows that the umami taste intensity was highest in the

333

mushroom extract of P. ostreatus (9.33 ± 1.51), which also exhibited the highest EUC level.

334

The lowest intensity level was observed in the extract from T. fuciformis (2.42 ± 0.62) and

335

Auri. auricular-judae (2.46 ± 1.33), which also showed the lowest EUC levels (Table 2).

336

These results suggest that the human sensory evaluation yields results very similar to those of

337

the umami intensity determination using HPLC.

338

Human sensory test was performed to evaluate the taste of food samples in various

339

studies, including juices, breads, meat, tea, and many more (Bleibaum et al., 2002; He et al.,

340

2009). A study on the quality of bread supplemented with mushroom mycelia by Ulziijargal,

341

Yang, Lin, Chen and Mau (2013) revealed that the umami intensity of all mycelium-

342

supplemented breads was higher than that of white bread, and the sensory profiles of these

343

breads were moderately acceptable in flavor and overall scores. In another study, Dermiki et

344

al. (2013) mentioned that the sensory analysis of meat samples containing shiitake mushroom

345

extract scored higher in umami compared to the control. This result suggests that shiitake

346

mushroom extract could be used to enhance the umami taste of food without significantly

347

changing the flavor attributes of the final products. Bai, Guo, Ma, Guo and Lin (2013) also

348

performed sensory evaluation of fermented tea with medicinal mushrooms and the results

349

revealed that the low-grade tea leaves were significantly upgraded and the flavour of the

350

fermented tea was also improved by fermentation with the medicinal mushroom. 14

351 352

3.5.2. Electronic tongue measurement

353

The sensory evaluation of mushroom extracts was performed using the electronic

354

tongue test. Umami taste intensity based on the electronic tongue measurement ranged from

355

8.45 ± 0.33 to 14.35 ± 0.20. All mushroom samples showed negative scores in saltiness and

356

sourness (Fig. 2). The bitterness of all samples was relatively high. Mushrooms with low

357

umami taste score appeared to have very high bitterness score, whereas mushrooms with high

358

umami taste levels also featured high levels of saltiness. The umami intensity from this

359

evaluation is presented in Table 3. Umami taste intensity significantly differed among the

360

samples of mushroom extracts (p < 0.05). F. velutipes exhibited the highest intensity with a

361

score of 14.35 ± 0.20 and the lowest intensity was observed in Auri. auricula-judae (8.45 ±

362

0.33).

363

The electronic tongue or taste sensing system was also successfully employed in

364

various studies by Chen et al. (2008) and He et al., (2009). Bleibaum et al. (2002) conducted

365

a study in which apple juice quality was compared by both human sensory evaluation and

366

electronic tongue sensors. Results from those studies implied that the electronic tongue

367

system is capable of evaluating taste characteristics of a variety of samples. Tran et al. (2004)

368

applied the electronic tongue system for the taste analysis of brown rice. In their study, the

369

sensory scores for umami and sweetness of cooked brown rice with different milling yields

370

were compared, and it was concluded that the electronic tongue could successfully be

371

employed for the evaluation of rice taste. It is possible to predict rice umami taste using the

372

taste sensing system. Taste differences of brown rice with different milling yields can be

373

determined not only by physicochemical methods but also using the taste sensor. Another

374

application of the electronic tongue test in the food science field was performed by Qiu,

375

Wang and Gao (2015) for evaluation of processed strawberry juice, in which basic tastes such 15

376

as sour, salty, sweet, bitter, and savory were compared between samples. The results from that

377

study proposed that utilisation of the electronic tongue represents a fast and cheap tool for

378

qualitative discrimination between processed strawberry juices.

379 380

3.6. Correlation between sensory evaluations and umami intensity

381

The Spearman’s rank correlation is a non-parametric measure of statistical dependence

382

between two variables. The Spearman’s rank correlation coefficient rs is computed by using

383

rank scores Ri for Xi and Ci for Yj. These rank scores are defined as follows:

384

Ri = ∑  + (ri + 1) / 2 for i = 1, 2, ….., R

385

Cj = ∑  + (cj + 1) / 2 for j = 1, 2, ….., C

386

The formulas for rs and its asymptotic variance can be obtained from the Pearson formulas by

387

substituting Ri and Cj for Xi and Yj, respectively.

388

Correlation is considered significant at a p-value < 0.05. The EUC values of mushroom

389

samples showed a correlation with both the score from the human sensory evaluation and the

390

electronic tongue measurement score (Table 4). Moreover, umami taste intensity based on the

391

human sensory evaluation also significantly correlated with that of the electronic tongue

392

measurement. The human sensory evaluation had a tendency to correlate well with all

393

components of umami taste except for XMP. In the same way, umami taste scores from the

394

electronic tongue measurement exhibited strong correlation with IMP and flavour 5´-

395

nucleotides, and moderate correlation with the AMP level. It can be concluded from these

396

results that all the three analysis methods correlated well with one another and that these

397

methods provide comparable results and can be used equivalently.

398

The correlation between the human sensory evaluation and the electronic tongue

399

measurement was identified by He et al. (2009) in a study assessing Chinese tea. The results

400

showed that electronic tongue sensors were correlated best with human sensory evaluation, 16

401

which is in agreement with the results of our study. Kobayashi et al. (2010) also reported that

402

taste sensors yield results closer to human sensory scores for samples with similar taste but

403

different taste intensity, and the correlation between these two methods was very high,

404

suggesting that the electronic tongue can function as a taste sensor for an objective taste

405

evaluation. In a study by Tran et al. (2004), it was stated that significant differences of umami

406

taste were observed between samples with different milling yields when evaluated by

407

electronic tongue systems, suggesting that differences of brown rice samples can be

408

determined by both physiochemical methods and by electronic tongue systems. Correlation

409

between human sensory evaluation, chemical analysis, and electronic tongue system was also

410

reported in other studies by Bleibum et al. (2002); Dermiki et al. (2013); Jiang, Luo and Ying

411

(2015).

412 413

4. Conclusion

414 415

In this study, the umami taste of mushroom extracts was analysed by HPLC, human

416

sensory evaluation, and electronic tongue measurement. In addition, the correlations between

417

sensory evaluations (human and electronic tongue), EUC, and each umami taste component

418

were measured. The EUC results showed that the levels of umami taste compounds in some

419

mushroom extracts were very high. Based on these findings, mushrooms should be

420

considered as a good raw material and natural source for industrial seasoning manufacture.

421

Correlations between EUC levels and umami taste scores of the electronic tongue

422

measurement, as well as between the score from the human sensory evaluation and the

423

electronic tongue measurement were observed. EUC value was strongly correlated with

424

umami intensity obtained from the electronic tongue measurement suggesting that the

425

electronic tongue is capable of identifying the umami intensity in samples. These results are 17

426

promising in terms of the application of the electronic tongue as an objective measurement

427

for conventional sensory evaluations or chemical analyses of the umami taste of mushrooms.

428

This methodology could therefore potentially play a key role in food processing applications.

429 430 431

Acknowledgements

432 433

This work was supported by the GRRC program of the Gyeonggi province (GRRC-

434

CAU-2012-B01) and the development of mushroom products and related functional

435

resources of the Rural Development Administration (PJ907021102012), Republic of Korea.

436 437 438

Appendix A. Supplementary data Supplementary data associated with this article can be found in the online version.

439 440

References

441 442

Bai, W-F., Guo, X-Y., Ma, L-Q., Guo, L-Q., & Lin, J-F. Chemical Composition and Sensory

443

Evaluation of Fermented Tea with Medicinal Mushrooms. Indian Journal of

444

Microbiology, 53(1), 70-76.

445 446

Beluhan, S., & Ranogajec, A. (2011). Chemical composition and non-volatile components of Croatian wild edible mushrooms. Food Chemistry, 124, 1076-1082.

447

Bleibaum, R. N., Stone, H., Tan, T., Labreche, S., Saint-Martin, E., & Isz, S. (2002).

448

Comparison of sensory and consumer results with electronic nose and tongue sensors

449

for apple juices. Food Quality and Preference, 13, 409-422.

18

450

Chen, Q., Zhao, J., & Vittayapadung, S. (2008). Identification of the green tea grade level

451

using electronic tongue and pattern recognition. Food Research International, 41(5),

452

500-504.

453

Cho, I. H., Choi, H-K., & Kim, Y-S. (2010). Comparison of umami-taste active components

454

in the pileus and stipe of pine-mushrooms (Tricholoma matsutake Sing.) of different

455

grades. Food Chemistry, 118, 804-807.

456

Dermiki, M., Phanphensophon, N., Mottram, D. S., & Methven, L. (2013). Contributions of

457

non-volatile and volatile compounds to the umami taste and overall flavour of shiitake

458

mushroom extracts and their application as flavour enhancers in cooked minced meat.

459

Food Chemistry, 141, 77-83.

460

He, W., Hu, X., Zhao, L., Liao, X., Zhang, Y., Zhang, M., & Wu, J. (2009). Evaluation of

461

Chinese tea by the electronic tongue: Correlation with sensory properties and

462

classification according to geographical origin and grade level. Food Research

463

International, 42(10), 1462-1467.

464

Jiang, T., Luo, Z., & Ying, T. (2015). Fumigation with essential oils improves sensory quality

465

and enhanced antioxidant ability of shiitake mushroom (Lentinus edodes). Food

466

Chemistry, 172, 692-698.

467

Kalač, P. (2012). A review of chemical composition and nutritional value of wild-growing

468

and cultivated mushrooms. Journal of the Science of Food and Agriculture, 93(2), 209-

469

218.

470 471

Kalač, P. (2009). Chemical composition and nutritive value of European species ofwild growing mushrooms. A review. Food Chemistry, 113(1), 9-16.

472

Khan, M. A., Khan, L. A., Hossain, M. S., Tania, M., & Uddin, M. N. (2009). Investigation

473

on the nutritional composition of the common edible and medicinal mushrooms

474

cultivated in Bangladesh. Bangladesh Journal of Mushroom, 3(1), 21-28. 19

475

Kobayashi, Y., Habara, M., Ikezazki, H., Chen, R., Naito, Y., & Toko, K. (2010). Advanced

476

taste sensors based on artificial lipids with global selectivity to basic taste qualities and

477

high correlation to sensory scores. Sensors, 10, 3411-3443.

478

Liang, C.-H., Tsai, S.-Y., Huang, S.-J., Liang, Z.-C., & Mau, J.-L. (2010). Taste quality and

479

antioxidant properties of medicinal mushrooms Phellinus linteus and Sparassis crispa

480

mycelia. International Journal of Medicinal Mushrooms, 12, 141-145.

481 482 483 484

Lee, Y. L., Jian, S.Y., & Mau, J.L. (2009). Composition and non-volatile taste components of Hypsizigus marmoreus. Food Science and Technology, 42(2), 594-598. Li, W., Gu, Z., Yang, Y., Zhou, S., Liu, Y., & Zhang, J. (2014). Non-volatile taste components of several cultivated mushrooms. Food Chemistry, 143, 427-431.

485

Lorenzetti, R., Lilla, S., Donato, J. L., & Nucci G. (2007). Simultaneous quantification of

486

GMP, AMP, cyclic GMP and cyclic AMP by liquid chromatography coupled to tandem

487

mass spectrometry. Journal of Chromatography B, 859, 37-41.

488

Mateos-Vivas, M., Rodriguez-Gonzalo, E., Dominguez-Alvarez, J., Garcia-Gomez, D.,

489

Ramirez-Bernabe, R., & Carabias-Martinez, R. (2015) Analysis of free nucleotide

490

monophosphates in human milk and effect of pasteurization or high-pressure

491

processing on their contents by capillary electrophoresis coupled to mass spectrometry.

492

Food Chemistry, 174, 348-355.

493 494

Mau, J. L. (2005). The umami taste of edible and medicinal mushrooms. International Journal of Medicinal Mushrooms, 7(1&2), 119-125.

495

Pei, F., Shi, Y., Gao, X., Wu, F., Mariga, A. M., Yang, W., Zhao, L., An, X., Xin, Z., Yang,

496

F., & Hu, Q. (2014). Changes in non-volatile taste components of button mushroom

497

(Agaricus bisporus) during different stages of freeze drying and freeze drying

498

combined with microwave vacuum drying. Food Chemistry, 165, 547-554.

20

499

Pereira, V., Pontes, M., Câmara, J. S., & Marques, J. C. (2008). Simultaneous analysis of free

500

amino acids and biogenic amines in honey and wine samples using in loop

501

orthophthalaldeyde derivatization procedure. Journal of Chromatography A, 1189, 435-

502

443.

503

Qiu, S., Wang, J., & Gao, L. (2015). Qualification and quantisation of processed strawberry

504

juice based on electronic nose and tongue. LWT – Food Science and Technology, 60,

505

115-123.

506

Tran, T. U., Suzuki, K., Okadome, H., Homma, S., & Ohtsubo, K. (2004). Analysis of the

507

tastes of brown rice and milled rice with different milling yields using a taste sensing

508

system. Food Chemistry, 88(4), 557-566.

509

Tsai, S. Y., Huang, S. J., Lo, S. H., Wu, T. P., Lian, P. Y., & Mau, J. L. (2009). Flavour

510

components and antioxidant properties of several cultivated mushrooms. Food

511

Chemistry, 113, 578-584.

512

Tsai, S. Y., Weng, C. C., Huang, S. J., Chen, C. C., & Mau, J. L. (2006). Nonvolatile taste

513

components of Grifola frondosa, Morchella esculenta and Termitomyces albuminosus

514

mycelia. LWT-Food Science and Technology, 39(10), 1066-1071.

515 516

Ulziijargal, E., Yang, J-H., Lin, L-Y., Chen, C-P., & Mau, J-L. (2013). Quality of bread supplemented with mushroom mycelia. Food Chemistry, 138, 70-76.

517

Wang, J-M., Chu, Y., Li, W., Wang, X-Y., Guo, J-H., Yang, L-L., Ma, X-H., Ma, Y-L., Yin,

518

Q-H., & Liu, C-X. (2014). Simultaneous determination of creatine phosphate, creatine

519

and 12 nucleotides in rat heart by LC–MS/MS. Journal of Chromatography B, 958, 96-

520

101.

521 522

Yamaguchi, S. (1991). Fundamental properties of umami taste. Journal of the Agricultural Chemistry Society of Japan, 65(5), 903–906.

21

523

Yamaoka, N., Kudo, Y., Inazawa, K., Inagawa, S., Yasuda, M., Mawatari, K-I., Nakagomi,

524

K., & Kaneko, K. (2010). Simultaneous determination of nucleosides and nucleotides

525

in dietary foods and beverages using ion-pairing liquid chromatography–electrospray

526

ionization-mass spectrometry. Journal of Chromatography B, 878, 2054-2060.

527

Yang, F. Q., Li, D. Q., Feng, F., Hu, D. J., & Li, S. P. (2010). Determination of nucleotides,

528

nucleosides and their transformation products in Cordyceps by ion-pairing reversed-

529

phase liquid chromatography–mass spectrometry. Journal of Chromatography A, 1217,

530

5501-5510.

531 532

Yang, J. H., Lin, H. C., & Mau, J. L. (2001). Non-volatile taste components of several commercial mushrooms. Food Chemistry, 72, 465-471.

533

Zhang, Y., Venkitasamy, C., Pan, Z., & Wang, W. (2013). Recent developments on umami

534

ingredients of edible mushrooms – A review. Trend in Food Science & Technology, 33,

535

78-92.

536

537

538

539

540

541

542 543

22

544 545

Figure legend

546

Fig. 1. LC-MS and LC-MS/MS chromatogram for samples (A) P. salmoneostramineus

547

(AMP), (B) Ama. virgineoides (CMP), (C) P. ostreatus (IMP), (D) H. erinaceus (UMP), (E)

548

H. erinaceus (XMP)

549

Fig. 2. Spider plot for the sensory score based on the taste sensing system of mushroom

550

samples (A) F. velutipes, Hyp. marmoreus, P. ostreatus, Aga. bisporus, H. erinaceus, P.

551

ferulae; (B) P. eryngii, G. frondosa, T. fuciformis, P. salmoneostramineus, S. crispa, Ama.

552

virgineoides; and

553

var. citrinopileatus, Auri. auricula-judae

(C) L. edodes, Pol. multiplex, R. botrytis (Pers.) Ricken, P. cornucopiae

554

23

555

(A) MS

556 MS/MS

557 558

(B) MS

559 560 MS/MS

561 562 563 564

(C)

24

MS

565 MS/MS

566 567

(D) MS

568 MS/MS

569 570 571 572

(E)

25

MS

573 574 MS/MS

575 576

Fig. 1. LC-MS and LC-MS/MS chromatogram for samples (A) P. salmoneostramineus (AMP), (B)

577

Ama. virgineoides (CMP), (C) P. ostreatus (IMP), (D) H. erinaceus (UMP), (E) H. erinaceus (XMP)

578 579

26

(A)

Umami

Sourness 20 10 0 -10 -20 -30 -40 -50

Astringency

Flammulina velutipes Bitterness

Hypsizigus marmoreus Pleurotus ostreatus Agaricus bisporus

Saltiness

Hericium erinaceum Pleurotus ferulae

Richness

(B)

Umami

Sourness 20 10 0 -10 -20 -30 -40

Astringency

Pleurotus eryngii Bitterness

Grifola frondosa Tremella fuciformis Pleurotus salmoneostramineus Sparassis crispa

Saltiness

Amanita virgineoides

Richness

(C)

Umami

Sourness 30 20 10 0 -10 -20 -30 -40

Astringency

Lentinus edodes Bitterness

Saltiness

Polyozellus multiplex Ramaria botrytis (Pers.) Ricken Pleurotus cornucopiae var. citrinopileatus Auricularia auriculajudae

Richness

Fig. 2. Spider plot for sensory score based on taste sensing system of mushroom samples (A) F. velutipes, Hyp. marmoreus, P. ostreatus, Aga. bisporus, H. erinaceus, P. ferulae; (B) P. eryngii, G. frondosa, T. fuciformis, P. salmoneostramineus, S. crispa, Ama. virgineoides; (C) L. edodes, Pol. multiplex, R. botrytis (Pers.) Ricken, P. cornucopiae var. citrinopileatus, Auri. auricula-judae

580

Table 1

581

Individual 5´-nucleotides content (mg/g) of mushroom samples samples

AMP

CMP

GMP

IMP

UMP

XMP

flavour

total 5´-

5´-

nucleoti

nucleoti

des

des

Agaricus

1.77 ±

3.46 ±

bisporus

0.60f

0.30f

Amanita

8.67 ±

21.13 ±

virgineoi

c

ND ND

a

0.04

0.76

0.22 ±

0.03 ±

7.54 ±

0.26 ±

0.34b

0.03jk

1.08 ±

5.29 ±

f

d

ND 0.76 ± ef

0.14

0.31

0.14

0.03±

0.05 ±

0.07 ±

7.54 ±

13.03 ±

0.33c

0.56ef

1.84 ±

36.93 ±

f

0.20

1.50a

des Auricular ia

h

ND

k

0.18

0.03

9.79 ±

20.51 ±

0.03

h

k

0.01

j

0.10 ± i

0.40 ±

0.09

0.08

0.27l

0.43 ±

4.94 ±

35.55 ±

auriculajudae Flammul ina

b

1.39

ND

ab

4.51± d

0.95

0.19

0.32 ± 0.03

j

gh

0.12

d

0.24

2.62a

1.46 ±

14.50 ±

velutipes Grifola

0.76 ±

1.88 ±

gh

gh

frondosa

0.10

0.02

Hericiu

2.27 ±

3.47 ±

1.07 f

1.40f

3.71 ±

2.87 ±

m

ND

1.02± f

ND

10.40 ± a

0.44 ± gh

0.06

fg

0.34

0.44e

0.34

0.14

5.57 ±

8.48 ±

4.74 ±

10.31 ±

24.53 ±

0.14c

0.18b

0.15a

0.28b

1.38d

4.18 ±

0.25 ±

0.59 ±

4.76 ±

11.81 ±

erinaceu s Hypsizig us

e

ND

f

0.62

0.14

1.70 ±

4.98 ±

d

jk

0.17

0.13

0.35±

2.38 ±

fgh

0.14

d

0.20

0.83f

marmor eus Lentinus edodes Pleurotu

fg

0.52

ND

s

ND

e

0.14

1.15 ± 0.10

ND

hij

e

2.17 ±

0.08

0.05

0.27

0.82f

0.40±

ND

1.09 ±

1.49 ±

2.64 ±

d

0.14

0.49

e

11.58 ±

0.01

g

b

2.52 ±

g

fg

0.62

0.53j

cornuco piae var. citrinopil eatus Pleurotu s eryngii

0.67 ± h

0.16

19.70 ± b

0.16

ND

3.28± e

0.04

5.50 ± c

0.06

1.49 ± c

0.07

4.77 ± d

0.04

30.65 ± 0.06c

27

Pleurotu

ND

s ferulae Pleurotu s

2.69 ±

ND

fg

0.07 5.44 ± d

9.33 ±

0.01 ND

c

0.55

0.69

30.86 ±

0.98 ±

0.09± h

13.93 ± a

0.12 ± jk

0.00

0.51 ± i

0.05

0.02

0.11 ±

0.87 ±

0.65 ± efg

0.05

0.88 ± de

0.10

0.74 ± 0.06

h

14.81 ± a

0.05

3.55 ± 0.13hi 30.08 ± 0.37c

ostreatu s Pleurotus salmoneost

a

ND

ij

0.01

0.03

0.04 ±

0.26 ±

0.01

h

h

0.03 ± j

0.14 ± i

32.84 ±

0.11

0.00

0.01

0.46b

1.19 ±

0.34 ±

1.39 ±

2.88 ±

ramineus

Polyozell us

h

ND

jk

0.02

0.04

0.64 ±

1.27 ±

1.05± f

g

0.02

0.02

0.96±

1.44 ±

0.05

hi

g

0.07

0.14i

1.08 ±

4.44 ±

multiple x Ramaria botrytis

h

ND

hi

0.36

0.09

0.59 ±

0.37 ±

f

f

0.12 ± ij

0.01

0.08

0.01

0.08±

0.07 ±

0.01 ±

gh

0.04

0.39h

(Pers.) Ricken Sparassi s crispa

0.61

0.25

Tremella

0.13 ±

8.15 ±

fuciformi

0.04h

0.18d

h

ND

jk

ND

k

j

0.09 ± i

1.12 ±

0.03

0.00

0.03

0.62k

0.06±

0.05 ±

0.06 ±

0.12 ±

8.44 ±

0.00h

0.01k

0.01j

0.01i

0.14g

0.04

h

s 582

Values are expressed as mean ± standard deviation of triplicate analysis

583

ND: not detected

584

Flavour 5´-nucleotides = GMP + IMP + XMP

585

a-l

586

different (Duncan, p < 0.05)

Values bearing different superscript lowercase letters within the same column are significantly

587

28

588

Table 2

589

Content of aspartic acid, glutamic acid and equivalent umami concentration (EUC) in mushroom

590

samples aspartic

glutamic

MSG-like

EUC

acid (mg/g)

acid (mg/g)

(mg/g)

(mg MSG/g)

Agaricus bisporus

18.1 ± 2.57a

24.3 ± 4.38bc

42.4 ± 6.90a

2,480 ± 358b

Amanita virgineoides

6.80 ± 0.08cd

35.0 ± 3.66a

41.8 ± 4.45a

1380 ± 55.0c

Auricularia

0.33 ± 0.05g

0.61 ± 0.13h

0.94 ± 0.17f

1.51 ± 0.42d

Flammulina velutipes

1.60 ± 0.36fg

5.83 ± 1.44gh

7.43 ± 1.80f

480 ± 152d

Grifola frondosa

2.48 ± 0.37f

12.2 ± 1.87ef

14.6 ± 2.23de

226 ± 83.2d

Hericium erinaceus

4.76 ± 1.32e

10.3 ± 2.81fg

15.0 ± 4.13cde

1160 ± 395c

Hypsizigus marmoreus

3.09 ± 0.59f

19.7 ± 3.90cd

22.8 ± 4.49bcd

1280 ± 183c

Lentinus edodes

1.95 ± 0.03fg

9.54 ± 2.43fg

11.5 ± 0.51e

243 ± 20.6d

Pleurotus

5.56 ± 1.38de

17.6 ± 4.22de

23.1 ± 5.61bc

252 ± 153d

Pleurotus eryngii

5.74 ± 0.81de

9.50 ± 1.23fg

15.2 ± 2.03cde

532 ± 65.5d

Pleurotus ferulae

2.91 ± 0.36f

12.3 ± 1.93ef

15.2 ± 2.29cde

86.8 ± 11.9d

Pleurotus ostreatus

7.66 ± 1.56c

20.0 ± 4.27cd

27.6 ± 10.38b

3890 ± 833a

Pleurotus

13.9 ± 1.19b

28.0 ± 2.38b

41.9 ± 3.57a

2040 ± 180b

Polyozellus multiplex

2.13 ± 0.15fg

3.38 ± 0.43h

5.51 ± 0.36f

58.3 ± 8.59d

Ramaria botrytis (Pers.)

1.29 ±

2.63 ± 0.37h

3.92 ± 0.52f

41.1 ± 7.04d

Ricken

0.16cfg

Sparassis crispa

2.42 ± 0.68f

11.8 ± 8.12efg

14.2 ± 7.68e

40.4 ± 17.4d

Tremella fuciformis

1.36 ± 0.18fg

3.60 ± 0.44h

4.96 ± 0.69f

8.88 ± 4.32d

samples

auricula-

judae

cornucopiae

var. citrinopileatus

salmoneostramineus

591

Values are expressed as mean ± standard deviation of triplicate analysis

592

MSG-like = aspartic acid + glutamic acid

593

a-h

Values bearing different superscript lowercase letters within the same column are significantly

29

594

different (Duncan, p < 0.05)

595

30

603

Table 3

604

Umami taste intensity based on sensory evaluations by human and electronic tongue test Samples

Human sensory test

Electronic tongue test

Agaricus bisporus

8.60±1.67a

13.81 ± 0.13b

Amanita virgineoides

6.00±1.22b

12.11 ± 0.17f

Auricularia auricula-judae

2.46±1.33d

8.45 ± 0.33j

Flammulina velutipes

4.00±2.68bcd

14.35 ± 0.20a

Grifola frondosa

5.60±2.41bc

12.81 ± 0.05de

Hericium erinaceus

4.83±1.94bcd

13.58 ± 1.61c

Hypsizigus marmoreus

4.80±2.28bcd

14.16 ± 0.03a

Lentinus edodes

4.00±1.22bcd

11.83 ± 0.00g

Pleurotus cornucopiae var. citrinopileatus

4.67±1.03bcd

8.96 ± 0.11i

Pleurotus eryngii

4.40±2.30bcd

12.98 ± 0.12d

Pleurotus ferulae

5.00±2.10bcd

13.41 ± 0.07c

Pleurotus ostreatus

9.33±1.51a

13.81 ± 0.21b

Pleurotus salmoneostramineus

6.00±1.41b

12.61 ± 0.02e

Polyozellus multiplex

3.00±1.22cd

11.75 ± 0.00g

Ramaria botrytis (Pers.) Ricken

3.00±1.87cd

10.96 ± 0.09h

Sparassis crispa

3.60±1.52bcd

12.58 ± 0.12e

2.42±0.62d

12.74 ± 0.00e

Tremella fuciformis 605

Values are expressed as mean ± standard deviation of triplicate analysis

606

a-h

607

different (Duncan, p < 0.05)

Values bearing different superscript lowercase letters within the same row are significantly

608 609 32

596 597

Table 4 Correlation coefficients between sensory evaluations, EUC and each of umami components Variables

Correlation coefficients

p value

EUC and human sensory evaluation***

0.86

< 0.00001

EUC and electronic tongue measurement*

0.57

0.02

Human sensory evaluation and electronic tongue measurement*

0.51

0.04

Human sensory evaluation and AMP*

0.58

0.01

Human sensory evaluation and IMP*

0.57

0.02

Human sensory evaluation and XMP

0.19

0.47

Human sensory evaluation and flavour 5’-nucleotides*

0.54

0.02

Human sensory evaluation and aspartic acid***

0.87

< 0.00001

Human sensory evaluation and glutamic acid***

0.88

< 0.00001

Human sensory evaluation and MSG-like***

0.89

< 0.00001

Electronic tongue measurement and AMP*

0.53

0.03

Electronic tongue measurement and IMP**

0.65

0.004

Electronic tongue measurement and XMP

0.08

0.76

Electronic tongue measurement and flavour 5’-nucleotides**

0.64

0.005

Electronic tongue measurement and aspartic acid

0.38

0.13

Electronic tongue measurement and glutamic acid

0.37

0.15

Electronic tongue measurement and MSG-like

0.40

0.11

598

*

599

**

600 601 602

***

p value < 0.05 p value < 0.01

p value < 0.001 Correlation is significant at p value < 0.05

31

610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625

Highlight

-

Mushrooms were analysed for umami taste characteristic using HPLC and sensory evaluations.

-

Equivalent umami concentration (EUC) was examined, and most mushrooms exhibited high EUC values.

-

The EUC and the sensory score from the electronic tongue test were highly correlated.

-

The EUC also showed significant correlation with the human sensory evaluation score.

-

All three analysis methods provide comparable results and can be used equivalently.

33