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From: International Food Research Journal (ifrj@upm.edu.my) To: a_pahira@yahoo.com

Date: Thursday, July 23, 2015, 10:59 PM PDT

Dear Abdul, Noted with thanks Best regards Son Radu Editor

--- Original Message ---

From: Abdul Rahim <a_pahira@yahoo.com>

To: ifrj@upm.edu.my <ifrj@upm.edu.my>

Cc:

Date: Friday, July 24 2015 11:23 AM

Subject: Manuscript to publication in the International Food Research Journal (IFRJ)

Dear Professor Dr. Son Radu Editor

International Food Research Journal Faculty of Food Science and Technology Universiti Putra Malaysia

43400 UPM Serdang Selangor, Malaysia

I want to publish my research paper in the International Food Research Journal.

I would be very grateful if you could accepted my manuscript entitled ?

The influence degree of substitution on the physicochemical properties of acetylated arenga starches? for publication. The names and full contact of four potential reviewers for the manuscript as follow :

1. Dr. Ir. Damat, MP., Universiti Muhammadiyah Malang, Indonesia, email:

damat@umm.ac.id; damatumm@yahoo.co.id

2. Dr. Ir. Nur Aini, Universiti Soedirman Purwokerto, Indonesia, email:

nuraini_munawar@yahoo.com

3. Prof. Dr. Dzulkifly Mat Hashim, Universiti Putra Malaysia, email:

dzulkifly@food.upm.edu.my

4. Assoc. Prof. Dr. Sharifah Kharidah Syeh Muhammad, Universiti Putra Malaysia, email: kharidah@putra.upm.edu.my

I am looking forward to hearing from you. Thank you very much.

Sincerely yours, Abdul Rahim

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I nternational F ^ood R ^esearch J ^ournal

(ISSN 22317546) Tel: 603-89468419 // Fax: 603-89423552 Email: ifrj@upm.edu.my Website: http://www.ifrj.upm.edu.my 24

^th

July 2015

Authors: Abdul Rahim, Syahraeni Kadir and Jusman

Manuscript title: The influence degree of substitution on the physicochemical properties of acetylated arenga starches

Manuscript ID: IFRJ-2015-337 Dear Abdul Rahim,

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Kind regards,

Son Radu, Ph.D.

Editor, International Food Research Journal

(Indexed in SCOPUS, EBSCO, CHEMICAL ABSTRACT, CABI, ProQuest and

World Islamic Science Citation)

1

The influence degree of substitution on the physicochemical

1

properties of acetylated arenga starches

2

1*

Abdul Rahim,

¹

Syahraeni Kadir and

²

Jusman

3

4

1

Faculty of Agricultural, Tadulako University,

5

Jl. Soekarno Hatta Km 9 No.32 Palu, Central Sulawesi, 94118

6

Indonesia

7

8

2

Faculty of Mathematics and Natural science, Tadulako University,

9

Jl. Soekarno Hatta Km 9 No.32 Palu, Central Sulawesi, 94118

10

Indonesia

11

12 13 14 15 16 17 18

*Corresponding author:

19

Email: a_pahira@yahoo.com

20

Tel.: 62451 429738; Fax: +62451 429738

21

2

Abstract

22

Chemical modification is usually carried out to overcome the

23

unstable properties of native arenga starch and improve its

24

physicochemical properties during processing. In this study,

25

acetylation of arenga starch was carried out. Native arenga starch

26

was acetylated with acetic anhydride at 5, 10, 15 and 20% (starch

27

basis, sb) in aqueous slurry at pH 7, 8, 9 and 10. Acetyl percentage

28

(Ac%), degree of substitution (DS), fourier transform infrared

29

spectroscopy (FT-IR) spectra, crystallinity, water and oil holding

30

capacity (WHC and OHC), swelling power and solubility of the native

31

and modified arenga starches were investigated. The results

32

indicated that Ac% and DS of acetylated arenga starches prepared

33

with 15% (sb) at pH 8 combination was 6,221% and 0.249, which

34

was the highest value among those prepared at any others. The

35

FTIR spectra of modified starches resulted in the acetyl group

36

incorporation with the starch as shown by absorption of the ester

37

carbonyl group at band 1720 cm

^-1

. The X-ray diffraction revealed that

38

increasing DS was related to decreasing crystallinity. The WHC,

39

OHC, swelling power and solubility of acetylated arenga starches

40

increased with increasing DS indicating increase in both

41

hydrophilicity and hydrophobicity of the starches.

42

Keywords: Arenga starch, physicochemical, acetylation, degree of

43

substitution.

44

3

Introduction

45

Starch is the major raw material in the food industry because of its

46

good thickening and gelling properties, which make it an excellent

47

ingredient for the manufacture of various food products (Betancur et

48

al., 2002). Native starches, irrespective of their sources are

49

undesirable for many applications because of their inability to

50

withstand processing conditions, so there is a need to improve

51

desirable functional properties. In order to meet the requirements of

52

specific industrial processes, starches are modified chemically by

53

degradation, substitution or cross-bonding.

54 55

Chemical modifications improved the physicochemical and functional

56

characteristics of the starch and tailored it to specific food

57

applications. Chemical modification is generally achieved through

58

derivatization such as etherification, esterification, cross-linking and

59

acid hydrolysis (Santacruz et al., 2002). In acetylation, hydrophilic

60

hydroxyl groups are substituted with hydrophobic acetyl groups. It

61

makes starch more hydrophobic and prevents the formation of

62

hydrogen bonding between hydroxyl groups and water molecules

63

(Owolabi et al., 2014).

64 65

4

Acetylated starch exhibits increased stability in food applications

66

compared to its native counterpart; therefore, it has been used to

67

increase the stability and resistance of food products to

68

retrogradation (Singh et al., 2004). Starch acetates are prepared

69

commercially with a low (0.1-0.3) degree of substitution (DS) through

70

the reaction of an aqueous suspension of starch granules with acetic

71

anhydride (Biswas et al., 2008; Shogren, 2003; Shogren and Biswas,

72

2006).

73 74

Arenga starch is an important source of starch in tropical countries. It

75

is prepared from the pith of palm Arenga (species Arenga pinnata).

76

Arenga starch obtained from A. pinnata is an economically important

77

palm species in Indonesia. Chemical modifications by acetylation in

78

arenga starch have not yet been reported in literature, although they

79

have been applied to starch and other polymers. Starch acetylation

80

promotes the introduction of the acetyl group in amylose and

81

amylopectin molecules forming a granular starch ester which has

82

superior properties when compared to its native form. In fact, it has

83

been used to confer higher thermal stability and resistance to

84

retrogradation (Singh et al., 2004). According to Colussi et al. (2014),

85

acetylation in rice starch reduces crystallinity and increases thermal

86

stability. The objective of this study was to obtain an acetylated

87

5

arenga starch with an acetylation percentage suitable and degree of

88

substitution (DS) for use in food, and to evaluate the influence of the

89

DS on the physicochemical properties of acetylated arenga starches.

90 91

Materials and Methods

92

Materials

93

Arenga starch (Arenga pinnata Merr.) used for this study was

94

obtained from Sigi, Central Sulawesi Provinsi, Indonesia. High-purity

95

acetic anhydride 98% was purchased from Sigma-Aldrich Chemical

96

Co. (St. Louis, MO, USA). The Sodium hydroxide (NaOH) and

97

hydrochloric acid (HCl) were purchased from Merck. The chemicals

98

for analysis used in the study were of analytical grade purchased at

99

local agent.

100 101

Acetylated of arenga starch

102

Acetylated starch was prepared by a modified procedure of Phillips

103

et al. (1999) with slight modification. Starch (100 g) was dispersed in

104

225 ml of distilled water and stirred for 60 min at 25

^o

C. The acetic

105

anhydride of 5, 10, 15, 20 % (starch basis, sb) was added drop-wise

106

to the stirred slurry, while maintaining the pH 7, 8, 9 and 10 using

107

3.0% NaOH solution. The reaction was allowed to proceed for 60 min

108

after the completion of acetic anhydride addition. The slurry was then

109

6

adjusted to pH 4.5 with 0.5 N HCl. After sedimentation, it was

110

washed free of acid, twice with distilled water and once with 95%

111

ethanol, and then oven-dried at 40

^o

C.

112 113

Determination of acetyl percentage and degree of substitution

114

The percentage of acetyl groups (Ac%) and degree of substitution

115

(DS) were determined titrimetrically, following the method by

116

Sanchez et al. (2010). Acetylated starch (1.0 g) and 50 ml of 75%

117

aqueous ethanol were placed in a 250 ml flask. The loosely stopper

118

flask was agitated, warmed to 50 ◦C for 30 min, cooled and 40 ml of

119

0.5 M KOH were added. The excess alkali was back-titrated with 0.5

120

M HCl using phenolphthalein as an indicator. The solution was left to

121

stand for 2 h, and then the alkali leached from the sample was

122

titrated. A blank, using the original unmodified starch, was also used.

123

Initially, the acetyl (%) was calculated as:

124

Acetyl % = [(Blank – Sample) x Molarity of HCl x 0.043 x 100]

Sample weight

125

Blank and sample were titration volumes in ml, sample weight was in

126

g. DS is defined as the average number of sites per glucose unit that

127

possess a substituent group.

128 129

DS = (162 x Acetyl %) [4300 – (42 x Acetyl %)]

130

7

Fourier transform infrared spectroscopy (FT-IR) spectra analysis

131

Sample preparation and analysis parameters were performed

132

according to Diop et al. (2011). Tablets were prepared from the

133

mixture of the sample with KBr at a ratio of 1:100 (sample: KBr).

134

Infrared spectra of native and acetylated starches samples were

135

obtained by a Fourier Transform Spectrometer (IR Prestige 21,

136

Shimadzu) in the 5000–400 cm

^-1

region.

137 138

XRD analysis

139

X-ray diffraction of native and acetylated starches was measured

140

using method of Miao et al. (2011). X-ray diffraction analysis was

141

performed with an X’ Pert PRO X-ray powder diffractometer

142

(PANalytical, Almelo, The Netherlands) operating at 40 kV and 30

143

mA with Cu Kα radiation (λ = 1.5406 Å). The starch powders were

144

packed tightly in a rectangular glass cell (15 x 10 mm, thickness 0.15

145

cm) and scanned at a rate of 2

^o

/min from the diffraction angle (2θ) 3

^o 146

to 80

^o

at room temperature. The crystallinity was calculated

147

according to the equation below:

148

Xc = Ac (Aa + A𝑐)

149

where Xc is the crystallinity, A

c

is the crystalline area and Aa is the

150

amorphous area on the X-ray diffractogram.

151

8

Water and oil holding capacity

152

Water and oil holding capacity (WHO, OHC) of native and acetylated

153

starches was measured using method of Larrauri et al. (1996).

154

Twenty-five ml of distilled water or commercial olive oil were added

155

to 250 mg of dry sample, stirred and left at room temperature for 1 h.

156

After centrifugation, the residue was weighed WHC and OHC were

157

calculated as g water or oil per g of dry sample, respectively.

158 159

Swelling power and solubility

160

The method of Adebowale et al. (2009) was employed to determine

161

the swelling power and solubility of the starch. Five hundred (500)

162

mg of starch sample was weighed into a centrifuge tube and it was

163

reweighed (W

1

). The starch was then dispersed in 20 ml of water. It

164

was then heated at temperature of 80

^o

C for 30 min in a thermostated

165

water bath. The mixture was cooled to room temperature and

166

centrifuged at 3000g for 15 min. Supernatant was decanted carefully

167

and residue weighed for swelling power determination. The weight of

168

dry centrifuge tube and the residue and the water retained was taken

169

as W

2

.

170

Swelling power = W

₂

– W

₁

Weight of starch

171

172

9

Aliquots (5 ml) of the supernatant were dried to a constant weight at

173

110

^o

C. The residue obtained after drying of the supernatant

174

represented the amount of starch solubilized in water. Solubility was

175

calculated as g per 100 g of starch on dry weight basis.

176 177

Statistical analysis

178

The data reported were the means of triplicate measurements.

179

Statistical analysis were carried out with Duncan’s multiple test (P <

180

0.05) using SPSS version 18 software (SPSS Institute Inc., Cary,

181

NC).

182 183

Results and Discussion

184

Acetyl percentage (Ac%) and degree of substitution (DS)

185

Table 1 shows rates of the percentage of acetyl groups and degree

186

of substitution of the acetylated arenga starch at different levels of

187

acetic anhydride (5%, 10%, 15% and 20%) and pH (7, 8, 9 and 10)

188

combination. The acetylation of arenga starch promoted the

189

incorporation of acetyl groups in the molecule, resulting in an acetyl

190

percentage and degree of substitution between 0.858 to 6.221% and

191

DS 0.033 to 0.249 respectively, allowing food application. The

192

highest Ac% (6.221%) and DS (0.249) was reached by acetylation at

193

concentration of acetic anhydride 15% - pH 8 combination. Some

194

10

studies on acetylated starches were used to evaluate the effect of

195

the concentration of acetic anhydride and pH, since both molecules

196

were composed of anhydroglucose. The molecule of arenga strach

197

had a favorable effect on diffusion and absorption of acetyl groups

198

when compared to starch molecules. This is due to the fact that

199

starch molecules are arranged in the form of granules which hinder

200

access to acetic anhydride, although arenga starch showed similar

201

levels of acetylated starches in the same reaction conditions

202

replacement.

203 204

The effect of adding different levels of acetic anhydride (2–12%) on

205

acetyl and the degree of substitution of potato and corn starches was

206

studied by Singh et al. (2004). These authors reported that the

207

increase of the substitution degree of acetylated starch was

208

dependent on the acetic anhydride concentration. In the case of

209

potato starch, the DS ranged from 0.18 to 0.24, while corn starch

210

showed a lower DS, ranging from 0.13 to 0.18.

211 212

FTIR spectra

213

The chemical structure of native and acetylated arenga starches

214

samples was studied by means of Fourier transform infrared

215

spectroscopy. The collected spectra are included in Figure 1.

216

11

Acetylation lead to the substitution of hydroxyl groups in the starch

217

molecules with carbonyl containing groups. The characteristic peaks

218

at 3700-3000 cm

⁻¹

and 3000-2800 cm

⁻¹

are the hydroxyl groups (O–

219

H) and methylene (C–H) stretching vibration of the glucose unit,

220

respectively. The absorption at about 1651 cm

⁻¹

is due to residual

221

bound water (H

2

O). Compared to that of the native starch curve

222

(Figure 1a), new absorption band at 1720 cm

⁻¹

appeared in

223

acetylated arenga starches curves (Figure 1b; 1c; 1d). The band

224

occurred at 1720 cm

⁻¹

is C=O stretching vibration of an ester group.

225

The intensity of those bands increased with the esterification level,

226

whereas the intensity of the band assigned to the stretching of

227

hydroxyl groups of starch (3700–3000 cm

^-1

) gradually decreased as

228

a consequence of the increasing number of hydroxyls which were

229

replaced by ester groups.

230 231

Acetylated barley starches had strong absorption bands at 1735–

232

1740 cm

^-1

(C=O stretching of acetyl group), 1368 cm

^-1

(C-H in acetyl

233

group) and 1234 cm

^-1

(C-O stretching of acetyl group) with evidence

234

of acetylation. On the other hand, since the intensity of the hydroxyl

235

group peak at 3000–3600 cm

^-1

decreased, it has been suggested

236

that the hydroxyl groups in the starch molecules were converted into

237

acetyl groups (Halal et al., 2015). The structures of butyrylated corn

238

12

starch were characterized and the results indicated a new absorption

239

peak at 1749 cm

^-1

(Garg and Jana, 2011), butyrylated high amylose

240

maize starch at band of 1740 cm

^-1

(Lopez et al., 2009) which were

241

assigned to the C=O stretching vibration and butyrylated arenga

242

starch at band of 1728 cm

^-1

(Rahim et al., 2012).

243 244

Crystallinity

245

The X-ray diffraction patterns of native and acetylated arenga starch

246

samples are shown in Figure 2. The peaks observed in present study

247

showed that native and butyrylated arenga starches displayed typical

248

A-type pattern with main peaks at 2θ = 15

^o

, 17

^o

, 18

^o

and 23

^o

. The X-

249

ray diffraction patterns of the native, acetylated andoxidized barley

250

starches presented strong peaks at 15

^o

, 17

^o

, 18

^o

, 19 and 23

^o

(2Ɵ),

251

characteristic of type A cereal starches, as reported in corn, barley

252

and rice starches (Chavez et al., 2008; Zavareze et al., 2010) These

253

results suggested that esterification did not change the crystalline

254

pattern of acetylated arenga starches up to DS 0.249. These were

255

agreed with the findings of Song et al. (2006), who mentioned that

256

the esterification occurred primarily in the amorphous regions and did

257

not change the crystalline pattern of starches.

258 259

13

Esterification reduced the relative crystallinity of acetylated arenga

260

starches when compared to native arenga starch. Ac% and DS

261

increase of acetylated arenga starches (Table 1) reduced the relative

262

crystallinity. This indicated that the granules of acetylated arenga

263

starches had been damaged to some extent by the modification

264

processes. Intra and intermolecular hydrogen bonds were

265

responsible for the highly ordered crystalline structure. The results

266

were in accordance with those of the earlier report of Lopez et al.

267

(2010), that degree of crystallinity of the acetylated corn starch

268

granules was lower than that of the native starch. The results were

269

consistent with X-ray diffraction results that showed lower crystallinity

270

when compared to that of native barley starch (Halal et al., 2015).

271 272

Water and oil holding capacity

273

WHC and OHC of the acetylated arenga starches increased with the

274

relative increase DS (Figure 3). These data indicate that either

275

hydrophilicity or hydrophobicity tend to improve after acetylation.

276

Improvement in water and oil absorption was a result of introduction

277

of functional groups to the starch molecules, which facilitated a more

278

enhanced holding capacity.

279 280

14

At low level of DS, the acetyl groups were not sufficient to change

281

the behavior of hydroxyl groups. There was weakening of

282

intermolecular hydrogen bonds in starch with the introduction of

283

acetyl groups. Adebowale et al. (2006) found that WHC of the

284

acetylated sword bean starch at DS 0.14 was higher than that of the

285

native starch, while Teli and Valia (2013) reported that the OHC of

286

the acetylated banana was higher than that of the raw banana.

287

Working with acetylated sweet potato starches by Das et al. (2010)

288

reported that the water and oil binding capacity increased with

289

increasing DS (0.018 – 0.058).

290 291

Swelling power and solubility

292

The swelling power and solubility of native and acetylated arenga

293

starches are given in Figure 4. Swelling power of the acetylated

294

arenga starches tended to increase with increasing DS (Figure 4).

295

This phenomenon was probably caused by a weakening of

296

intermolecular association force due to introduction of acetyl groups

297

that reduced the hydroxyl groups. These were similar to the results of

298

Souza et al. (2015) that swelling power of the acetylated oat β-glucan

299

was higher than native starch, and increased with rise in acetic

300

anhydride and DS. Das et al. (2010) showed that swelling power of

301

15

acetylated sweet potato starch increased with increasing DS from

302

0.018 to 0.058.

303 304

Solubility of the acetylated arenga starches tended to increase along

305

with the increase in DS. The results were similar to the earlier report

306

of Kapelko et al. (2015) that solubility of the acetylation of acetylated

307

potato starches preparations increased their solubility in water and

308

water absorbability was than native starch.

309 310

Conclusion

311

The acetylation of arenga starch promoted the incorporation of acetyl

312

groups in the molecule, resulting in a degree of substitution between

313

0.033 to 0.249, allowing food application. Acetylation of the arenga

314

starch molecule decreased the of crystallinity and increased the

315

WHC, OHC, swelling power and solubility along with the increase in

316

DS indicating that acetylation improved physicochemical properties

317

of the starch. This report will be useful to promote the use of the

318

acetylated arenga starch for industrial applications in food

319

production.

320 321 322 323

16

Acknowledgement

324

This research was funded by “Grand Research Program of National

325

strategic” with contract number: 040/SP2H/PPM/DIT.LITABMAS/II/

326

2015 from the Ministry of National Education of Republic of

327

Indonesia.

328 329

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398

Sánchez-Rivera, M. M., Flores-Ramírez, I., Zamudio-Flores, P. B.,

399

González-Soto, R., Rodríguez-Ambríz, S. L., and Bello-Pérez, L.

400

A. 2010. Acetylation of banana (Musa paradisiaca L.) and maize

401

(Zea mays L.) starches using a microwave heating procedure

402

and iodine as catalyst: Partial characterization. Starch/Stärke 62:

403

155–164.

404

Santacruz, S., Koch, K., Svensson, E., Raules, J. and Eliasson, A.S.

405

2002. Three underutilized sources of starch from the andean

406

region in ecuador part I. Physico-chemical Characterization.

407

Journal Carbohydrate Polymers 49: 63-70.

408

Shogren, R. L. 2003. Rapid preparation of starch esters by high

409

temperature/pressure reaction. Carbohydrate Polymers 52: 319–

410

326.

411

20

Shogren, R. L. and Biswas, A. 2006. Preparation of water soluble

412

and water swellable starch acetates using microwave heating.

413

Carbohydrate Polymer 64: 16–21.

414

Singh, N., Chawla, D. and Singh, J. 2004. Influence of acetic

415

anhydride on physicochemical, morphological and thermal

416

properties of corn and potato starch. Food Chemistry 86: 601–

417

608.

418

Song, X. Y., He, G. Q., Ruan, H. and Chen, Q. H. 2006. Preparation

419

and properties of octenyl succinic anhydride modified early

420

indica rice starch. Starch/Stärke 58: 109–117.

421

Souza, N.L., Bartz, J., Zavareze, E.R., Oliveira, P.D., Silva, W.S.V.,

422

Alves, G.H. and Dias, A.R.G. 2015. Functional, thermal and

423

rheological properties of oat b-glucan modified by acetylation.

424

Food Chemistry 178: 243–250.

425

Teli, M.D. and Valia, S.V. 2013. Acetylation of banana fibre to

426

improve oil absorbency. Carbohydrate Polymers 92: 328– 333.

427

Zavareze, E. R., Storck, C. R., Castro, L. A. S., Schirmer, M. A. and

428

Dias, A. R. G. 2010. Effect of heat moisture treatment on rice

429

starch of varying amylose content. Food Chemistry 121: 358–

430

365.

431 432 433

21

List of Table

434

Table 1. Percentage of acetyl groups (Ac%) and degree of

435

substitution (DS) at different concentrations of acetic

436

anhydride (AA) and pH combination

437

438

List of Figures

439

Figure 1. FTIR spectra of native arenga starch (a) and acetylated

440

arenga starches at different of DS: 0.066 (b), 0.208 (c)

441

and 0.249 (d).

442

Figure 2. X-ray diffractograms and cristallinity of native arenga

443

starch (a), and acetylated arenga starches with different

444

DS: 0.066 (b), 0.091 (c), 0.208 (d) and 0.249 (e).

445

Figure 3 Effects of DS on the water and oil holding capacities of

446

acetylated arenga starches. Numbers in the graph

447

followed by the same letter in common are not

448

significantly different at p < 0.05.

449

Figure 4. Effects of DS on the swelling power and solubility of

450

butyrylated arenga starches. Numbers in the graph

451

followed by the same letter in common are not

452

significantly different at p < 0.05.

453 454 455

22 456

457 458 459 460 461

Table 1.

462

Treatments Ac (%) DS

5% AA - pH 7 5% AA - pH 8 5% AA - pH 9 5% AA - pH 10 10% AA - pH 7 10% AA - pH 8 10% AA - pH 9 10% AA - pH 10 15% AA - pH 7 15% AA - pH 8 15% AA - pH 9 15% AA - pH 10 20% AA - pH 7 20% AA - pH 8 20% AA - pH 9 20% AA - pH 10

1.931 2.560 1.924 1.717 1.395 2.361 1.288 0.858 5.039 6.221 2.576 1.284 5.775 5.232 5.991 5.678

0.074 0.099 0.074 0.066 0.053 0.091 0.049 0.033 0.199 0.249 0.099 0.049 0.232 0.208 0.239 0.227 463

Figure 1.

464 465 466 467 468 469

23 470

471 472 473 474 475

Figure 2.

476

477

Figure 3.

478

24 479

Figure 4.

480

481

1.87a 1.86a 1.88a

2.53b 2.53b

3.00c

1.89p

2.28q 2.19pq

2.20pq 2.18pq 2.33q

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Native starch

DS 0.033 DS 0.066 DS 0.091 DS 0.208 DS 0.249

OHC (g/g)

WHC (g/g)

Degree of substitution

WHC OHC

5.73ab 5.67a 6.68ab 6.10ab 7.03ab 7.12b

4.00p

7.21p

16.57q 16.31q 17.56q

29.52r

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Native starch

DS 0.033 DS 0.066 DS 0.091 DS 0.208 DS 0.249

Solubility (%)

Swelling Power (g/g)

Dergree of substitution

Swelling power Solubility

9/7/2021 Yahoo Mail - Re: Status of my manuscript with ID: IFRJ-2015-337

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Cc:Date: Sunday, March 20 2016 12:16 PM

Subject: Re: Status of my manuscript with ID: IFRJ-2015-337

Dear Professor Dr. Son Radu

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Herewith I am sending file the prepared my manuscript (ID: IFRJ-2015-337) according to IFRJ guidelines.

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From: International Food Research Journal <ifrj@food.upm.edu.my>

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Cc:Date: Thursday, March 17 2016 09:41 AM

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Dear Professor Dr. Son Radu

Editor International Food Research Journal

How to the status of my manuscript with ID: IFRJ-2015-337.

I am looking forward to hearing from you. Thank you very much.

1 The influence degree of substitution on the physicochemical properties 1

of acetylated arenga starches 2

3

4

5

1*Abdul Rahim, ¹Syahraeni Kadir and ²Jusman 6

7

8

1 Faculty of Agriculture, Tadulako University, 9

Jl. Soekarno Hatta Km 9 No.32 Palu, Central Sulawesi, 94118 Indonesia 10

11

2 Faculty of Mathematics and Natural science, Tadulako University, 12

Jl. Soekarno Hatta Km 9 No.32 Palu, Central Sulawesi, 94118 Indonesia 13

14 15 16 17 18 19

*Corresponding author:

20

Email: a_pahira@yahoo.com 21

Tel.: 62451 429738; Fax: +62451 429738 22

2 Abstract

23

Chemical modification is usually carried out to overcome the unstable 24

properties of native arenga starch and improve its physicochemical properties 25

during processing. In this study, acetylation of arenga starch was carried out.

26

Native arenga starch was acetylated with acetic anhydride at 5, 10, 15 and 27

20% (starch basis, sb) in aqueous slurry at pH 7, 8, 9 and 10. Acetyl 28

percentage (Ac%), degree of substitution (DS), fourier transform infrared 29

spectroscopy (FT-IR) spectra, crystallinity, water and oil holding capacity 30

(WHC and OHC), swelling power and solubility of the native and modified 31

arenga starches were investigated. The results indicated that Ac% and DS of 32

acetylated arenga starches prepared with combination of acetic anhydride 33

15% (sb) and pH 8 was 6,221% and 0.249, which was the highest value 34

among those prepared at any others. The FTIR spectra of modified starches 35

resulted in the acetyl group incorporation with the starch as shown by 36

absorption of the ester carbonyl group at band 1720 cm^-1. The X-ray 37

diffraction revealed that increasing of DS was related to decreasing of 38

crystallinity. The WHC, OHC, swelling power and solubility of acetylated 39

arenga starches increased with increasing of DS indicate increasing in both 40

hydrophilicity and hydrophobicity of the starches.

41

Keywords: Arenga starch, physicochemical, acetylation, degree of 42

substitution.

43 44

Introduction 45

Starch is the major raw material in the food industry because of its good 46

thickening and gelling properties, which make it an excellent ingredient for the 47

manufacture of various food products (Betancur et al., 2002). Native starches, 48

3 irrespective of their sources are undesirable for many applications because of 49

their inability to withstand processing conditions, so there is a need to 50

improve desirable functional properties. In order to meet the requirements of 51

specific industrial processes, starches are chemically modified by 52

degradation, substitution or cross-bonding.

53 54

Chemical modifications improved the physicochemical and functional 55

characteristics of the starch and tailored it to specific food applications.

56

Chemical modification is generally achieved through derivatization such as 57

etherification, esterification, cross-linking and acid hydrolysis (Santacruz et 58

al., 2002). In acetylation, hydrophilic hydroxyl groups are substituted with 59

hydrophobic acetyl groups. It makes starch more hydrophobic and prevents 60

the formation of hydrogen bonding between hydroxyl groups and water 61

molecules (Owolabi et al., 2014).

62 63

Acetylated starch exhibits increased stability in food applications compared to 64

its native counterpart; therefore, it has been used to increase the stability and 65

resistance of food products to retrogradation (Singh et al., 2004). Starch 66

acetates are prepared commercially with a low (0.1-0.3) degree of substitution 67

(DS) through the reaction of an aqueous suspension of starch granules with 68

acetic anhydride (Biswas et al., 2008; Shogren, 2003; Shogren and Biswas, 69

2006).

70 71

Arenga starch is an important source of starch in tropical countries. It is 72

prepared from the pith of palm Arenga (species Arenga pinnata). Arenga 73

4 starch obtained from A. pinnata is an economically important palm species in 74

Indonesia. Chemical modifications by acetylation in arenga starch have not 75

yet been reported in literature, although they have been applied to starch and 76

other polymers. Starch acetylation promotes the introduction of the acetyl 77

group in amylose and amylopectin molecules forming a granular starch ester 78

which has superior properties when compared to its native form. In fact, it has 79

been used to confer higher thermal stability and resistance to retrogradation 80

(Singh et al., 2004). According to Colussi et al. (2014), acetylation in rice 81

starch reduces crystallinity and increases thermal stability. The objective of 82

this study was to obtain an acetylated arenga starch with an acetylation 83

percentage suitable and degree of substitution (DS) for use in food, and to 84

evaluate the influence of the DS on the physicochemical properties of 85

acetylated arenga starches.

86 87

Materials and Methods 88

Materials 89

Arenga starch (Arenga pinnata Merr.) used for this study was obtained from 90

Sigi, Central Sulawesi Provinsi, Indonesia. High-purity acetic anhydride 98%

91

was purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). The 92

Sodium hydroxide (NaOH) and hydrochloric acid (HCl) were purchased from 93

Merck. The chemicals for analysis used in the study were of analytical grade 94

purchased at local agent.

95 96 97 98

5 Acetylated of arenga starch

99

Acetylated starch was prepared by a modified procedure of Phillips et al.

100

(1999) with slight modification. Starch (100 g) was dispersed in 225 ml of 101

distilled water and stirred for 60 min at 25^oC. The acetic anhydride of 5, 10, 102

15, 20 % (starch basis, sb) was added drop-wise to the stirred slurry, while to 103

maintain the pH 7, 8, 9 and 10 using 3.0% NaOH solution. The reaction was 104

allowed to proceed for 60 min after the completion of acetic anhydride 105

addition. The slurry was then adjusted to pH 4.5 with 0.5 N HCl. After 106

sedimentation, it was washed free of acid, twice with distilled water and once 107

with 95% ethanol, and then oven-dried at 40^oC.

108 109

Determination of acetyl percentage and degree of substitution 110

The percentage of acetyl groups (Ac%) and degree of substitution (DS) were 111

determined titrimetrically, following the method by Sanchez et al. (2010).

112

Acetylated starch (1.0 g) and 50 ml of 75% aqueous ethanol were placed in a 113

250 ml flask. The loosely stopper flask was agitated, warmed to 50 ◦C for 30 114

min, cooled and 40 ml of 0.5 M KOH were added. The excess alkali was 115

back-titrated with 0.5 M HCl using phenolphthalein as an indicator. The 116

solution was left to stand for 2 h, and then the alkali leached from the sample 117

was titrated. A blank, using the original unmodified starch, was also used.

118

Initially, the acetyl (%) was calculated as:

119

Acetyl % =[(Blank – Sample) x Molarity of HCl x 0.043 x 100]

Sample weight 120

6 Blank and sample were titration volumes in ml, sample weight was in g. DS is 121

defined as the average number of sites per glucose unit that possess a 122

substituent group.

123

DS = (162 x Acetyl %) [4300 – (42 x Acetyl %)]

124

125

Fourier transform infrared spectroscopy (FT-IR) spectra analysis 126

Sample preparation and analysis parameters were performed according to 127

Diop et al. (2011). Tablets were prepared from the mixture of the sample with 128

KBr at a ratio of 1:100 (sample: KBr). Infrared spectra of native and 129

acetylated starches samples were obtained by a Fourier Transform 130

Spectrometer (IR Prestige 21, Shimadzu) in the 5000–400 cm^-1 region.

131 132

XRD analysis 133

X-ray diffraction of native and acetylated starches was measured using 134

method of Miao et al. (2011). X-ray diffraction analysis was performed with an 135

X’ Pert PRO X-ray powder diffractometer (PANalytical, Almelo, The 136

Netherlands) operating at 40 kV and 30 mA with Cu Kα radiation (λ = 1.5406 137

Å). The starch powders were packed tightly in a rectangular glass cell (15 x 138

10 mm, thickness 0.15 cm) and scanned at a rate of 2^o/min from the 139

diffraction angle (2θ) 3^o to 80^o at room temperature. The crystallinity was 140

calculated according to the equation below:

141

Xc = Ac (Aa + A𝑐) 142

where Xc is the crystallinity, Ac is the crystalline area and Aa is the 143

amorphous area on the X-ray diffractogram.

144

7 Water and oil holding capacity

145

Water and oil holding capacity (WHO, OHC) of native and acetylated starches 146

was measured using method of Larrauri et al. (1996). Twenty-five ml of 147

distilled water or commercial olive oil were added to 250 mg of dry sample, 148

stirred and left at room temperature for 1 h. After centrifugation, the residue 149

was weighed WHC and OHC were calculated as g water or oil per g of dry 150

sample, respectively.

151 152

Swelling power and solubility 153

The method of Adebowale et al. (2009) was employed to determine the 154

swelling power and solubility of the starch. Five hundred (500) mg of starch 155

sample was weighed into a centrifuge tube and it was reweighed (W1). The 156

starch was then dispersed in 20 ml of water. It was then heated at 157

temperature of 80^oC for 30 min in a thermostated water bath. The mixture 158

was cooled to room temperature and centrifuged at 3000g for 15 min.

159

Supernatant was decanted carefully and residue weighed for swelling power 160

determination. The weight of dry centrifuge tube and the residue and the 161

water retained was taken as W2. 162

Swelling power = W₂ – W₁ Weight of starch 163

164

Aliquots (5 ml) of the supernatant were dried to a constant weight at 110^oC.

165

The residue obtained after drying of the supernatant represented the amount 166

of starch solubilized in water. Solubility was calculated as g per 100 g of 167

starch on dry weight basis.

168 169

8 Statistical analysis

170

The data reported were the means of triplicate measurements. Statistical 171

analysis were carried out with Duncan’s multiple test (P < 0.05) using SPSS 172

version 18 software (SPSS Institute Inc., Cary, NC).

173 174

Results and Discussion 175

Acetyl percentage (Ac%) and degree of substitution (DS) 176

Table 1 shows rates of the percentage of acetyl groups and degree of 177

substitution of the acetylated arenga starch at different levels with 178

combination of acetic anhydride (5%, 10%, 15%, 20% (sb)) and pH (7, 8, 9 179

and 10). The acetylation of arenga starch promoted the incorporation of acetyl 180

groups in the molecule, resulting in an acetyl percentage and degree of 181

substitution between 0.858 to 6.221% and DS 0.033 to 0.249 respectively, 182

allowing food application. The highest Ac% (6.221%) and DS (0.249) was 183

reached by acetylation with combination of acetic anhydride 15% (sb) and pH 184

8. Some studies on acetylated starches were used to evaluate the effect of 185

the concentration of acetic anhydride and pH, since both molecules were 186

composed of anhydroglucose. The molecule of arenga starch had a favorable 187

effect on diffusion and absorption of acetyl groups when compared to starch 188

molecules. This is due to the fact that starch molecules are arranged in the 189

form of granules which hinder access to acetic anhydride, although arenga 190

starch showed similar levels of acetylated starches in the same reaction 191

conditions replacement.

192 193

9 The effect of adding different levels of acetic anhydride (2–12%) on acetyl 194

and the degree of substitution of potato and corn starches was studied by 195

Singh et al. (2004). These authors reported that the increase of the 196

substitution degree of acetylated starch was dependent on the acetic 197

anhydride concentration. In the case of potato starch, the DS ranged from 198

0.18 to 0.24, while corn starch showed a lower DS, ranging from 0.13 to 0.18.

199 200

FTIR spectra 201

The chemical structure of native and acetylated arenga starches samples was 202

studied by means of Fourier transform infrared spectroscopy. The collected 203

spectra are included in Figure 1. Acetylation lead to the substitution of 204

hydroxyl groups in the starch molecules with carbonyl containing groups. The 205

characteristic peaks at 3700-3000 cm⁻¹ and 3000-2800 cm⁻¹ are the hydroxyl 206

groups (O–H) and methylene (C–H) stretching vibration of the glucose unit, 207

respectively. The absorption at about 1651 cm⁻¹ is due to residual bound 208

water (H2O). Compared to that of the native starch curve (Figure 1a), new 209

absorption band at 1720 cm⁻¹ appeared in acetylated arenga starches curves 210

(Figure 1b; 1c; 1d). The band occurred at 1720 cm⁻¹ is C=O stretching 211

vibration of an ester group. The intensity of those bands increased with the 212

esterification level, whereas the intensity of the band assigned to the 213

stretching of hydroxyl groups of starch (3700–3000 cm^-1) gradually decreased 214

as a consequence of the increasing number of hydroxyls which were replaced 215

by ester groups.

216 217

10 Acetylated barley starches had strong absorption bands at 1735– 1740 cm^-1 218

(C=O stretching of acetyl group), 1368 cm^-1 (C-H in acetyl group) and 1234 219

cm^-1 (C-O stretching of acetyl group) with evidence of acetylation. On the 220

other hand, since the intensity of the hydroxyl group peak at 3000–3600 cm^-1 221

decreased, it has been suggested that the hydroxyl groups in the starch 222

molecules were converted into acetyl groups (Halal et al., 2015). The 223

structures of butyrylated corn starch were characterized and the results 224

indicated a new absorption peak at 1749 cm^-1 (Garg and Jana, 2011), 225

butyrylated high amylose maize starch at band of 1740 cm^-1 (Lopez et al., 226

2009) which were assigned to the C=O stretching vibration and butyrylated 227

arenga starch at band of 1728 cm^-1 (Rahim et al., 2012).

228 229

Crystallinity 230

The X-ray diffraction patterns of native and acetylated arenga starch samples 231

are shown in Figure 2. The peaks observed in present study showed that 232

native and butyrylated arenga starches displayed typical A-type pattern with 233

main peaks at 2θ = 15^o, 17^o, 18^o and 23^o. The X-ray diffraction patterns of the 234

native, acetylated andoxidized barley starches presented strong peaks at 15^o, 235

17^o, 18^o, 19 and 23^o (2Ɵ), characteristic of type A cereal starches, as reported 236

in corn, barley and rice starches (Chavez et al., 2008; Zavareze et al., 2010) 237

These results suggested that esterification did not change the crystalline 238

pattern of acetylated arenga starches up to DS 0.249. These were agreed 239

with the findings of Song et al. (2006), who mentioned that the esterification 240

occurred primarily in the amorphous regions and did not change the 241

crystalline pattern of starches.

242

11 Esterification reduced the relative crystallinity of acetylated arenga starches 243

when compared to native arenga starch. Ac% and DS increase of acetylated 244

arenga starches (Table 1) reduced the relative crystallinity. This indicated that 245

the granules of acetylated arenga starches had been damaged to some 246

extent by the modification processes. Intra and intermolecular hydrogen 247

bonds were responsible for the highly ordered crystalline structure. The 248

results were in accordance with those of the earlier report of Lopez et al.

249

(2010), that degree of crystallinity of the acetylated corn starch granules was 250

lower than that of the native starch. The results were consistent with X-ray 251

diffraction results that showed lower crystallinity when compared to that of 252

native barley starch (Halal et al., 2015).

253 254

Water and oil holding capacity 255

WHC and OHC of the acetylated arenga starches increased with the relative 256

increase DS (Figure 3). These data indicate that either hydrophilicity or 257

hydrophobicity tend to improve after acetylation. Improvement in water and oil 258

absorption was a result of introduction of functional groups to the starch 259

molecules, which facilitated a more enhanced holding capacity.

260 261

At low level of DS, the acetyl groups were not sufficient to change the 262

behavior of hydroxyl groups. There was weakening of intermolecular 263

hydrogen bonds in starch with the introduction of acetyl groups. Adebowale et 264

al. (2006) found that WHC of the acetylated sword bean starch at DS 0.14 265

was higher than that of the native starch, while Teli and Valia (2013) reported 266

that the OHC of the acetylated banana was higher than that of the raw 267

12 banana. Working with acetylated sweet potato starches by Das et al. (2010) 268

reported that the water and oil binding capacity increased with increasing DS 269

(0.018 – 0.058).

270 271

Swelling power and solubility 272

The swelling power and solubility of native and acetylated arenga starches 273

are given in Figure 4. Swelling power of the acetylated arenga starches 274

tended to increase with increasing DS (Figure 4). This phenomenon was 275

probably caused by a weakening of intermolecular association force due to 276

introduction of acetyl groups that reduced the hydroxyl groups. These were 277

similar to the results of Souza et al. (2015) that swelling power of the 278

acetylated oat β-glucan was higher than native starch, and increased with rise 279

in acetic anhydride and DS. Das et al. (2010) showed that swelling power of 280

acetylated sweet potato starch increased with increasing DS from 0.018 to 281

0.058.

282 283

Solubility of the acetylated arenga starches tended to increase along with the 284

increase in DS. The results were similar to the earlier report of Kapelko et al.

285

(2015) that solubility of the acetylation of acetylated potato starches 286

preparations increased their solubility in water and water absorbability was 287

than native starch.

288 289 290 291 292

13 Conclusion

293

The acetylation of arenga starch promoted the incorporation of acetyl groups 294

in the molecule, resulting in a degree of substitution between 0.033 to 0.249, 295

allowing food application. Acetylation of the arenga starch molecule 296

decreased the of crystallinity and increased the WHC, OHC, swelling power 297

and solubility along with the increase in DS indicating that acetylation 298

improved physicochemical properties of the starch. This report will be useful 299

to promote the use of the acetylated arenga starch for industrial applications 300

in food production.

301 302

Acknowledgement 303

We gratefully acknowledged the Directorate of Research and Community 304

Service, Directorate General of Higher Education, Ministry of Education and 305

Culture of the Republic of Indonesia, for providing fiancial support from the 306

National Strategic Research Grant Program in 2015.

307 308

References 309

Adebowale, K.O., Afolabi, T.A. and Olu-Owolabi, B.I. 2006. Functional, 310

physicochemical and retrogradation properties of sword bean (Canavalia 311

gladiata) acetylated and oxidized starches. Carbohydrate Polymers 65:

312

93–101.

313

Adebowale, K.O., Henle, T., Schwarzenbolz, U. and Doert, T. 2009.

314

Modification and properties of African yam bean (Sphenostylis 315

stenocarpa Hochst. Ex A. Rich.) Harms starch I: Heat moisture 316

treatments and annealing. Food Hydrocolloids 23: 1947–1957.

317