Improvement in Nutritional Attributes of Rice Starch with Dodecyl

Subscriber access provided by University of South Dakota

Food and Beverage Chemistry/Biochemistry

Improvement in nutritional attributes of rice starch with dodecyl gallate complexation: a molecular dynamic simulation and in vitro study Chengdeng Chi, Xiaoxi Li, Tao Feng, Xiaolan Zeng, Ling Chen, and Lin Li J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b02121 • Publication Date (Web): 16 Aug 2018 Downloaded from http://pubs.acs.org on August 17, 2018

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

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

Page 1 of 40

Journal of Agricultural and Food Chemistry

ACS Paragon Plus Environment


1

Improvement in nutritional attributes of rice starch with dodecyl gallate

2

complexation: a molecular dynamic simulation and in vitro study

3

Chengdeng Chi †, Xiaoxi Li *,†, Tao Feng ‡, Xiaolan Zeng ‡, Ling Chen †, Lin Li †

4 5

†

6

Ministry of Education Engineering Research Center of Starch and Protein

7

Processing, Guangdong Province Key Laboratory for Green Processing of Natural

8

Products and Product Safety, School of Food Science and Engineering, South China

9

University of Technology, Guangzhou 510640, China ‡

10 11

School of Perfume and Aroma Technology, Shanghai Institute of Technology,

No. 100 Haiquan Road, Shanghai 201418, China

12 13 14 15 16 17 18 19

*

20

Fax: +86 20 8711 3252

21

E-mail: [email protected]

Correspondence: Xiaoxi Li

22 23 24 25 26


Page 2 of 40

Page 3 of 40


27

ABSTRACT: To improve starch functionalities such as digestibility and antioxidant

28

activity, rice starch was complexed with antioxidant dodecyl gallate (DG). Molecular

29

dynamics simulation showed that the starch-DG inclusion complex was favorable,

30

and in 50 ns, the dodecyl segment resided in the helix of the amylose cavities, but the

31

gallate tail left outside. This theoretical finding was validated by UV-vis spectroscopy,

32

calorimetric and crystalline measurements, indicating V-type crystalline structures

33

containing type I and type II inclusion complexes can be formed after DG

34

complexation. Meritedly, starch digestibility was mitigated by synchronously

35

increasing slowly digestible starch (5.12%-22.83%) and resistant starch content

36

(8.69%-14.17%), and the antioxidant activity was also significantly increased. Such

37

inclusion complexes thereby acted as a carrier for targeting delivery of DG to human

38

lower gastrointestinal tract with potent antioxidant activity. Complexation with DG

39

synergistically improved starch digestibility and antioxidant activity, favoring the

40

intervention against chronic diseases, by ameliorating the postprandial glycemic

41

response and oxidative stress.

42 43

KEYWORDS: rice starch; digestibility; diabetes; oxidative stress; molecular

44

dynamic simulation

45 46 47 48



49

INTRODUCTION

50

Diabetes mellitus (DM) is claimed as a major public health challenge of the 21st

51

century. According to the data of World Health Organization (WHO), the number of

52

people with diabetes has risen from 108 million in 1980 to 422 million in 2014, and

53

will be rose rapidly in middle- and low-income countries. Suffering diabetes is

54

accompanied by many associated syndromes such as hyperglycemia, increased

55

oxidative stress and even other metabolic disorders 1, which causes people sub-health

56

status and even death.

57

Increasing evidences suggested that long-term consumption of high glycemic

58

index (GI) food was regarded as one of the most fundamental causes or contributors

59

to a wide variety of pathological conditions such as obesity, cardiovascular diseases

60

and type II diabetes 2, 3. Excess ingestion of rapidly digestible starch (RDS) foods will

61

increase the GI value and negatively affect human health, while slowly digestible

62

starch (SDS) and resistant starch (RS) are likely to lower the GI value 4, 5. In addition,

63

excessive caloric intake has been also suggested to increase oxidative stress in

64

different tissues and depletion of antioxidant enzymes with reduced glutathione levels

65

6

66

and participate in the development and progression of DM and its associated

67

complications

68

organelles and enzymes, simultaneous increased lipid peroxidation, and finally

69

promote the development of insulin resistance 1, 10. Evidences suggested consumption

70

of diets which rich with antioxidants and dietary fiber is linked to lower incidence of

. Oxidative stress can result from the imbalance of the antioxidant defense system

7-9

. Disordered free radical levels would lead to damage of cellular


Page 4 of 40

Page 5 of 40


11

71

cardiovascular disease and obesity

. Therefore, food dietary formulated with

72

antioxidants and SDS or RS may reduce the incidences of obesity and DM 12.

73

Reasonable diet recipe is a promising alternative strategy for intervention against

74

obesity and DM. Functional starches and phenolic compounds have been considered

75

as vital roles in regulating glucose homeostasis and insulin secretion, as well as

76

lowering oxidative stress. Dietary fiber (e.g., β-glucan) containing bread would reduce

77

the postprandial glucose level in bloodstream

78

content is also beneficial for controlling glucose concentration in plasma to prevent

79

occurrence of DM

80

suggested that consumption of foods enriched with numerous antioxidants (e.g.,

81

vitamins, phenolic acid and anthocyanins) also has potent ability in ameliorating the

82

development of obesity and DM

83

compounds were demonstrated with potential amelioration of oxidative stress

84

relatively low bioaccessibility and bioavailability in vivo limited its application in

85

intervening type 2 diabetes and its associated metabolic problems

86

with high SDS or RS content and robust antioxidant activities were considered as

87

promising candidates for preventing the incidence of obesity and DM 19.

13

. Starchy foods rich in SDS or RS

14

. On the other hand, recent experimental and clinical studies

15, 16

. However, even though varieties of phenolic 17

,

18

. Starchy foods

88

Rice (Oryza sativa L.) is the most important agricultural cereal, and consumed as

89

the staple food in most Asia countries due to its desirable essential amino acids, lipids

90

and carbohydrate required for human health 20. However, rice is classified as a high

91

GI food

92

through decreasing starch digestibility for avoiding the incidence of chronic diseases.

21

. It is surging a great interest to improve rice starch nutritional attributes



Page 6 of 40

22

93

Based on current knowledge, heat-moisture treatment

and lipid/protein

94

complexation 23, 24 have been widely used to mitigate rice starch digestion. Moreover,

95

improving the antioxidant activity of rice starchy foods is also as an alternative way to

96

ameliorate oxidative stress and decrease the incidences of metabolic syndromes

97

The synergistic effects of starch digestion mitigation and oxidative stress amelioration

98

seem to have potential ability to decrease the risks of chronic disease such as type II

99

diabetes and obesity. However, there is limited available information on

100

starches/starchy foods modification to synergistically improve the functionalities of

101

antioxidant activity and digestibility.

25

.

102

Dodecyl gallate (3,4,5-trihydroxybenzoate, DG) has been studied as a powerful

103

radical scavenger and an antifungal additive in foods. From the chemical structural

104

view, dodecyl gallate contains hydrophilic gallate segment and hydrophobic dodecyl

105

tail. Complexation with DG is likely to increase starch V-type crystalline structure

106

(rice starch-dodecyl tail) and endow the inclusion complexes with high antioxidant

107

activity

108

this work, DG-rice starch inclusion complexes were prepared and determined using

109

both theoretical molecular dynamic (MD) simulation and experimental approaches, to

110

evaluate its enzymatic digestibility and antioxidant activity. The results of this study

111

will provide additional options for nutritional and dietary recommendations on obesity,

112

DM and associated disease risk factors.

113

MATERIALS AND METHODS

114

26-28

, and in turn, significantly increasing rice starch nutritional attributes. In

Materials. Rice starch was purchased from Jinnong biotechnology Co., Ltd.


Page 7 of 40


115

(Jiangxi, China). The moisture content was determined by a moisture analyzer (MA35,

116

Sartorius Stedim Biotech GmbH, Germany). DG in this study was obtained from

117

Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Pancreatin and

118

amyloglucosidase were purchased from Sigma-Aldrich Co. LLC (Santa Clara, USA).

119

A glucose oxidase/peroxidase (GOPOD) used to determine glucose content was

120

obtained from Megazyme International Ireland (Bray Business Park, Bray, Co.

121

Wicklow, Ireland). Other reagents were analytical grade.

122

Preparation of rice starch-DG complexes. Starch slurry (16.67 wt%, dry starch

123

base, dsb) in a three-necked bottle was cooked in boiling water with constant stirring

124

(310 rpm) for 30 min. The gelatinized starch was cooled to 95 °C and added with

125

different amounts of DG (1, 5 and 9 wt%, DG/starch) under continuous stirring (450

126

rpm) for 30 min. After equilibration for desired time, samples were cooled to room

127

temperature and washed three times with 70% ethanol. All samples were air dried at

128

40 °C and smashed by a grinder for further analysis. Cooked rice starch and inclusion

129

complexes prepared with 1%, 5% and 9% DG were referred to CRS, CRS-1, CRS-5

130

and CRS-9, respectively.

131

DG determination. The UV-vis spectra of the samples were determined by a

132

UV-2600 spectrophotometer (Shimazu, Japan) by scanning from 190 to 350 nm. DG

133

content was measured as the Folin-Ciocalteu method described by previous research

134

29

135

completely dissolved in 4.0 mL dimethyl sulfoxide. 0.5 mL of the starch solution was

136

homogeneously mixed 2.0 mL of Folin-Ciocalteu reagent and followed by the

with slight modification. Briefly, 20 mg of the DG-rice starch complex was



137

addition of 20% Na2CO3 (5.0 mL). The mixture was vigorously shook and kept at

138

room temperature for 60 min in the dark. After that, the working solution was

139

centrifuged at 3000 g for 1 min and the absorbance was determined at 760 nm using a

140

UV-2600 spectrophotometer (Shimazu, Japan). Total DG content was calculated using

141

a standard DG curve and expressed as mg of DG equivalent (DE) per milligram of the

142

sample.

143

Differential scanning calorimetry (DSC). The thermal properties of each starch

144

were measured using a PerkinElmer differential scanning calorimeter (DSC)

145

Diamond-I with an internal coolant (Intercooler 1P) and nitrogen purge gas. Before

146

the measurement performed, the starch samples (ca. 70% moisture content) were

147

prepared by premixing the starches with distilled water in a high-pressure

148

stainless-steel pan with a gold-plated copper seal, then scanned from 30 °C to 130 °C

149

with a slow heating rate of 5 °C /min. The onset temperature (To), peak temperature

150

(Tp), end temperature (Te), and enthalpy (∆H) of gelatinization were recorded from the

151

DSC endothermic curve. The enthalpy was calculated based on the weight of dry

152

starch. All the results are reported as the averages of three replicates.

153

X-ray diffraction (XRD). The crystalline structures of the complexes were

154

analyzed with an Xpert PRO diffractometer (Panlytical, Netherlands) operated at the

155

condition of 40 mA and 50 KV. The Samples were scanned with a Cu-Kα radiation (λ

156

= 0.1542 nm) as X-ray source in the range from 4 to 45 ° (2θ, the angle of diffraction)

157

with a scanning step width of 0.033 ° and scanning speed of 10 °/min. The moisture

158

content of each sample was equilibrated at ambient condition before test. The MDI


Page 8 of 40

Page 9 of 40


159

Jade 6.0 software was applied to calculate starch relative crystallinity (RC) by

160

estimating the ratio of crystalline fraction to the total diffraction area based on a linear

161

baseline referring to the Nara and Komiya method

162

according to Scherrer's formula 31: ≈

163 164 165

30

. Crystallite size was estimated

λ × cos

Where L is the crystallite size in Å, λ is the wavelength and FWHM is the Full Width at Half-Maximum. In vitro digestibility. In vitro starch-DG complex digestibility were measured 32

166

based on the Englyst method

with slight modification. Samples (1.0 g, dsb) were

167

dispersed in 20.0 mL of acetate buffer solution (0.1 M, pH 5.2) which contained 4

168

mM CaCl2 and cooked in boiling water for 30 min. The cooked starch suspension

169

(95 °C for 30 min, and then cooled to 37 °C in 37 °C water bath) was incubated with

170

5 mL of enzyme solution (containing 787 USP porcine pancreatin and 3 units

171

amyloglucosidase) in 37 °C water bath with continuous shaking. An aliquot (0.5 mL)

172

of the hydrolysate was removed at time intervals of 20 min and 120 min, and then

173

mixed with 20 mL of 66% ethanol solution to stop the enzymes activity. The samples

174

were centrifuged at 3000 g for 5 min and the hydrolyzed glucose concentration of the

175

supernatant was measured using a GOPOD reagent. Each sample was analyzed in

176

triplicate. The glucose content at intervals of 20 and 120 min was labeled as G20 and

177

G120, and RDS, SDS, RS were calculated as followed equation: = 20 × 0.9 = 120 − 20 × 0.9 = − −



Page 10 of 40

178

In vitro DG release profile. The in vitro starch-DG complexes digestion and the

179

probable DG release profile were performed with a dissolution rate test apparatus

180

(RCZ-8B, Tianda Tianfa Co., Ltd., Tianjin, China) according to our previous study 33.

181

In order to simulate the foods transition in human gastrointestinal tract (GIT), the

182

complexes (1.0 g) were incubated in simulated gastric fluid (SGF) for 2 h, followed

183

by incubation in simulated intestinal fluid (SIF) for another 6 h. All in vitro

184

measurements were kept at 37 °C with gentle stirring (100 rpm). The SGF (pH 1.2)

185

consisted of 0.2 g NaCl, 7.0 mL HCl and 3.2 g pepsin; the SIF (pH 6.8) comprised 6.8

186

g KH2PO4, 190 mL NaOH (0.2 M) and 10.0 g pancreatin. Each 5 mL of sample was

187

collected at pre-set time points to determine the released DG content in vitro. The

188

collected hydrolysate was centrifuged at 10000×g for 20 min and the precipitate was

189

used to determine the DG content of the complexes residues. Particularly, residues

190

after incubation 2 h in SGF and 6 h in SIF were collected to further analyze its

191

antioxidant activity. Digested were CRS-1, CRS-5 and CRS-9 were referred to

192

CRS-1-R, CRS-5-R and CRS-9-R, respectively.

193

Determination of antioxidant activity in vitro. DPPH free radicals scavenging 34

194

activity was measured according to previously reported procedure

195

modifications. Briefly, Vc and rice starch-DG complexes were respectively dispersed

196

in distilled water with a series of concentrations (0.125, 0.25, 0.5, 1.5, 2.0 and 2.5

197

mg/mL). A 0.1 mL sample was added to each screw-cap tube and mixed with 0.4 mL

198

of ethanol DPPH solution (0.4 mM). The mixture was vortexed for 2 min and shaked

199

at 200 rpm on a platform shaker in the dark at room temperature for 90 min. The Abs


with slight

Page 11 of 40


200

was measured at 517 nm by a microplate reader (infinite 200Pro, Austria) and the

201

DPPH radical scavenging activity was calculated as followed: " "# % = 1 −

%& − %' %(

202

Where A0 represents the absorbance of the control (water instead of sample), A1

203

represents the absorbance of the sample, and A2 represents the absorbance of the

204

sample only (ethanol instead of DPPH solution)

205

Particularly, the antioxidant activity of starch-DG complexes residues collected

206

before were also determined in order to investigate the bioaccessibility of DG in

207

human simulated fluids.

208

Molecular dynamic (MD) simulation. MD simulations were performed with

209

the SANDER module of AMBER16. The initial amylose conformation was generated

210

using the GLYCAM_06j-1

211

module of AMBER. The DG module was obtained from http://zinc.docking.org/ and

212

use the GAFF parameter set

213

TIP3P water molecules. The system, DG and amylose (35 glucose residues), was

214

embedded in a dodecahedron box with a 130 Å × 30 Å × 30 Å and filled with 30000

215

water molecules. The time length of each MD steps is 0.002, and a total simulation

216

time of 50 ns with 5000 frames was lasted, to investigate the progression of

217

starch-DG complex formation. This performance was carried out using the Langevin

218

thermostat between the different groups, with a Langevin thermostat collision

219

frequency of 0.1 ps. Berendsen barostat was used for constant pressure simulation.

220

Cutoff distance in Angstroms values for non-bonded interactions was 10.0 Å. The

35

monosaccharide structural data base and the LINK

36

. Periodic boundary conditions were employed, with



221

initial configurations were subjected to 500 cycles of steepest descent energy

222

minimization when the amylose was hold. These initial configurations were then

223

heated from 0 to 368 K, and a constant temperature of 368 K was maintained during

224

the MD simulation process. All hydrogen-containing bond lengths were constrained to

225

their equilibrium values through application of the SHAKE algorithm.

226

Statistical analysis. All tests were conducted at least in triple and data analyzed

227

using IBM SPSS statistics version 21.0 (IBM, Armonk, NY, USA). Analysis of

228

variance (ANOVA) was followed by the Tukey’s HSD test to compare the treatments

229

and the significance level was set as P < 0.05.

230

231

RESULTS AND DISCUSSION

232

MD simulation of the starch-DG complex. Fig. 1(a) shows the theoretical

233

conformational changes of the starch/DG system at 95 °C in 50 ns. Rearrangement of

234

components over time showed a final conformation with hydrophobic dodecyl

235

segment in the cavities of the amylose helix while the gallate fragment outside the

236

cavities. Besides, starch assembly without DG entrapment also reassociated and a

237

more ordered structure was formed. These observations have witnessed the formation

238

of starch-DG complex and starch assemblies. The sequence of the interactions was

239

shown in Fig. 1(a) as follows. In the first 10 ns, amylose and DG were standing

240

separately with the DG molecule outside the amylose-like cavities. At 20 ns, DG

241

molecule was close to starch molecules and entrapped by the amylose-like cavities,

242

indicating an amylose-DG inclusion complex was firstly formed. At 30 and 40 ns,


Page 12 of 40

Page 13 of 40


243

starch molecules self-assembled and the DG was entrapped in the middle of the

244

amylose segment with the assistance of dodecyl fragment. However, the gallate tail

245

was outside the amylose cavities due to its hydrophilic characteristic. Finally, at 50 ns,

246

amylose containing DG inclusion complex was nearly unchanged with the dodecyl

247

fragment entangled in the amylose hydrophobic cavities and the gallate fragment

248

outside the cavity. Such a process indicated inclusion complexes as well as starch

249

assemblies could be formed at 95 °C.

250

To further prove the inclusion complex, root mean square deviation (RMSD) of

251

starch and DG during the simulation was calculated and shown in Fig. 1 (b). In first

252

25 ns, the RMSD value fluctuated intuitively, which implies the drastic changes of

253

DG and starch conformations. However, this unstable state was irreversibly improved

254

at ca. 30 ns, by increasing RMSD of starch but decreasing the counterpart of DG and

255

then keeping a relatively steady RMSD value of both DG and starch. These

256

observations indicated that starch molecules can rearrange with DG molecules to form

257

an inclusion complex to stabilize the system.

258

DG determination and quantification. To verify the interaction of DG to CRS,

259

the UV-vis spectra was determined and presented in Fig. 2. DG exhibited two

260

characteristic absorption bands at 217 and 276 nm, which should be assigned to the

261

π-system of the benzene ring. CRS showed no absorption peak ranging from 190 to

262

350 nm, while absorption bands appeared at 217 and 271 nm for all DG complexed

263

samples. Compared with the absorption peaks of pure DG and the physical mixture of

264

DG and CRS at 276 nm, the UV-vis absorption peak of the complexes shifted toward



265

a shorter wavelength (at 271 nm). This change might attribute to the smaller amount

266

of energy required for the π-π* transition due to the dodecyl insertion into starch

267

hydrophobic cavities and the weakened hyperconjugation between the hydrophilic

268

gallate tail and the hydrophobic dodecyl.

269

CRS-1, CRS-5 and CRS-9 showed significant differences in DG complexation

270

content (P < 0.05). The detailed parameters are summarized in Table 1. Native rice

271

starch and CRS contained ca. 0.09 mg DE/g starch. It was attributed to the certain

272

amount of phenolic compounds contained in native rice starch can be also determined

273

by the Folin-Ciocalteu method. The DG content in the inclusion complexes increased

274

from 7.91 to 48.15 mg/g starch when the available DG concentration was increased

275

from 1% to 9%. Comparing the results with previous study 37, it is noticeable that DG

276

complexation content (7.91-48.15 mg/g starch) in this study is much higher than

277

lauric acid content in the complexes (9-15 mg/g starch) which prepared using swelled

278

normal cornstarch and lauric acid. Granular starch below pasting temperature tented

279

to limit lauric acid access to amylose, while leached amylose/amylopectin from starch

280

granules above pasting temperature is likely to enhance DG complexation index.

281

More available hydrophobic molecules and amylose/amylopectin content favored the

282

formation of inclusion complexes.

283

Molecular ordered structure. The thermal transition parameters of all starch

284

samples are summarized in Table 2. One endotherm (G) was observed for native

285

starch, but two endotherms (Peak I and Peak II) for DG complexed starches (see in

286

Fig. 3). These endotherms are respectively ascribed to the melting of ordered double


Page 14 of 40

Page 15 of 40


287

amylopectin chains and starch-DG complexes. The transition enthalpy ∆H was

288

positively correlated to the amount of double helices or starch-DG inclusion

289

complexes. Native rice starch had a transition peak ranging from 60.13 to 77.57 °C

290

with a ∆H of 15.21 J/g, while CRS rather presented a peak at 98.22-106.68 °C. This

291

change indicated that double helices were completely disrupted under hydrothermal

292

condition, and original lipids formed inclusion complexes with starch molecules.

293

After DG complexation, two endotherms including the first one (Peak I) from 86.96

294

to 114.11 °C and the second endotherm (Peak II) ranging from 109.27 to 122.59 °C

295

were observed. The peak I mostly have resulted from the reassociated starch

296

assemblies and type I inclusion complexes which is similar to the type I starch-lipid

297

inclusion complexes that associated the helical fractions a random behavior, and the

298

peak II could be ascribed to the type II starch-DG inclusion complexes which have a

299

crystalline form and lamellae-like organization of starch-DG complexes. With the DG

300

complexation content increased, the melting temperature of these two endotherms was

301

synchronously increased, indicating the higher thermostability of the complexes. In

302

addition, the ∆H of Peak I followed the order of CRS-1 < CRS-5 < CRS-9, which

303

should correspond to the enhancement of the reassociated starch assemblies and/or

304

type I starch-DG complexes content. High DG available content favored the

305

formation of starch-DG inclusion complexes and increased the orders of

306

DG-contained starch structures. As the type I starch-DG complexes arranged, the type

307

II inclusion complexes can be obtained. Notably, CRS-5 and CRS-9 had higher ∆H of

308

Peak II than that of CRS-1, indicating more crystallites of the inclusion complexes



309

were arranged.

310

Crystalline structures. The diffractograms and crystal parameters of native rice

311

starch and cooked rice starch-DG complexes are respectively shown in Fig. 4 and

312

Table 1. Native rice starch showed a hybrid A+V type crystal structure with main

313

reflections at 15º, 20 º, 23 º and a doublet peaks at 17 º and 18 º (2θ) (Fig. 4). CRS

314

displayed a V-type crystal pattern with diffraction peaks at 13º and 19.8 º (2θ), due to

315

its original lipids entangled with starch molecules and the inclusion complexes were

316

formed. After DG complexation, starches displayed double diffraction peaks at 13º

317

and 19.8 º (2θ), indicating free DG was completely removed and V-type crystalline

318

structure was formed. Notably, the amount of V-type crystal of starches was increased

319

with the ascent of relative crystallinity (RC) from 28.1% to 30.9%. More DG

320

entangled in the complexes increased V-type structures and starch crystallinity. To our

321

knowledge, amylose-lipid forms spherulites through two steps: (i) association of

322

lipids into amylose hydrophobic cavities and (ii) rearrangement of crystalline units

323

into nano-particles. The crystal size of starch-lipids complexes in native rice starch

324

and CRS was 14.44 and 14.47 Å, respectively. It seems that V-type crystallite size

325

were irrelevant with starch conformational structures, since the original lipids content

326

before and after cooking remained unchanged. However, the crystallite size of

327

starch-DG inclusion complexes was increased (ranging from 46.12 to 47.74 Å) as the

328

amount of entangled DG enhanced. This observation was consistent with the DSC

329

results that more DG molecules entangled in the complexes favored the formation of

330

the type II starch-DG complexes. Assembly of starch-DG complexes was readily for


Page 16 of 40

Page 17 of 40


331

crystal nucleus growth and crystallite size enlargement.

332

Effect of DG on starch digestibility. Starch is the most important of

333

carbohydrate source for human dietary. Proper rates of glucose release and glucose

334

absorption from digesting starch in gastrointestinal tract play an important role in

335

human health by maintaining proper blood glucose levels. From the nutritional view,

336

starch-based foodstuffs containing higher amount of SDS or SDS are regarded as

337

functional

338

hyperglycaemia-related diseases. As presented in Table 3, native rice starch possessed

339

high RDS content (93.83%) and low SDS (3.10%) and RS (3.05%) content. CRS

340

showed the same digestibility to that of native rice starch. However, RDS of CRS-DG

341

complexes were significantly reduced to the range of 86.19%-62.70% in comparison

342

with that of CRS (93.83%), by enhancing SDS ranged from 5.12% to 22.83% and RS

343

of 8.16%-14.17%. These changes should be attributed to the formation of starch-DG

344

inclusion complexes, reassociated starch assemblies and DG-contained starch

345

aggregates.

foods

which

may

control

and

prevent

the

incidences

of

Although starch-lipid complex was considered as an undigestible starch fraction

346 347

38

348

CRS-1 had 5.12% of SDS and 8.69% of RS, while CRS-5 possessed 16.74% of SDS

349

and 10.09% of RS. For CRS-9, it contained more SDS fractions (22.83%) and RS

350

content (14.17%). It was indicated that CRS complexed with DG favored the

351

development of functional starchy foods rich in SDS and RS content. Chen, B. et al

352

also reported that lotus seed starch-glycerin monostearate complexes prepared by

, RS as well as SDS fraction were increased in this work when DG was complexed.



Page 18 of 40

39

353

high-pressure homogenization synchronously increased SDS and RS contents

.

354

Although the authors did not explain how the operation of glycerin monostearate

355

complexation combined with high-pressure homogenization treatment increased SDS

356

content, the changes of starch digestibility must result from the structural

357

transformations of lotus seed starch based on their findings. In this study, the

358

structural changes and molecule assembly should contribute to the enhancement of

359

SDS content when DG complexation amount was ascended.

360

In vitro DG release behavior. The release behaviors of DG from starch-DG

361

complexes in human simulated upper GIT were investigated. As displayed in Fig. 5,

362

the release percentage of DG from starch-DG complexes was gradually increased as

363

time went by. Amylose and long branch chains of amylopectin tend to entangle with

364

DG molecules and form starch-DG inclusion complexes, by which DG molecules

365

were entrapped in starch hydrophobic cavities. However, some DG molecules also

366

might be sandwiched between starch short chain molecules through H-bonds and act

367

as a molecular chaperone to assist starch assembly at the existence of abundant DG

368

molecules. Therefore, the DG molecules entrapped in starch-DG sandwich complexes

369

may readily release by the artificial interference (e.g., acidic and enzymatic

370

treatments), contributing to the uptrend of the DG release profile in SGF and SIF. In

371

first 2 h (SGF), ca. 20% of the DG escaped from CRS-1, CRS-5 and CRS-9, which

372

should result from the DG sandwiched between starch short chain molecules.

373

Different DG release behaviors in SIF were observed for these starch-DG complexes,

374

which could result from the different assembly cases of starch molecules and


Page 19 of 40


375

starch-DG complexes. Finally, a total of ca. 60% of DG released from CRS-5 and

376

CRS-9, while only ca. 40% of DG escaped from CRS-1. This observation indicated a

377

relatively high amount of DG in the complexes (more than 40% of the entangled DG)

378

could target to human lower GIT.

379

Antioxidant

activity

of

the

DG-contained

starch

complexes.

The

380

amylose/long amylopectin coils underwent a conformational change and presented a

381

hydrophobic cavity that inclusion complexes can be generated in the presence of guest

382

molecules such as lipids 40, ibuprofen 41, iodine 42, alcohols 42 and dimethyl sulfoxide

383

(DMSO)

384

could reside in the hydrophobic cavities of rice starch chains and inclusion complexes

385

could be formed, while the gallate tail (hydrophilic segment) outside the hydrophobic

386

cavities (see in MD results) would endow the starch-DG inclusion complexes with

387

potent antioxidant activity. Besides, DG molecules entrapped within starch-DG

388

sandwich complexes also enabled starch complexes to scavenge free radicals.

43

. As to the antioxidant DG, the dodecyl group (hydrophobic segment)

389

Complexation DG molecules with starch increased the antioxidant activity of the

390

complexes. It can be found from Fig. 6(a) that all DG-contained starch complexes

391

showed higher scavenging activity on DPPH radicals than that of native rice starch.

392

CRS-5 and CRS-9 showed higher scavenging activity on DPPH radicals than that of

393

the CRS-1, indicating a higher DG content entangled in the DG-contained starch

394

complexes contributed to a stronger antioxidant activity. However, the scavenging

395

activities of those DG-contained starch complexes on DPPH radicals were lower than

396

that of free Vc.



397

Generally, the small intestine shows highly catabolization (glucuronidation,

398

sulfation and methylation) towards phenolic compounds, which attenuates the

399

biological activity (such as antioxidant activity) and bioavailability of polyphenols in

400

human body 44. Hence, the colon is seen as an important organ for the metabolism of

401

phenolic compounds and its derivatives 44. DG assembled with starch molecules tends

402

to reduce DG direct adsorption in intestine and thus decrease the accessibility to

403

enzyme such as uridine 5’-diphosphate glucuronosyltransferases, and then shows low

404

biotransformation in human intestine and relatively strong antioxidant activity in

405

colon. Targeting DG release in colon is a feasible way to improve DG bioavailability.

406

As can be seen from Fig. 5, all starch-DG complexes could target more than 40% of

407

DG which entangled within starch complexes to human lower GIT, which ensured the

408

DG bioaccessibility to colon. All the residues of starch-DG complexes after digestion

409

in SGF and SIF showed relative strong scavenging activity on DPPH radicals (Fig.

410

6b). Unfortunately, due to the loss of DG in simulated upper GIT, the scavenging

411

activity of the residues was much lower than those of native DG-contained starch

412

complexes. The scavenging activity on DPPH radicals is highly dependent on either

413

the concentration of the complexes residues or DG content within the residues.

414

Starch-DG inclusion complex could be used as a practical delivery carrier for

415

antioxidant ingredients in human GIT.

416

Mechanism of the DG influenced starch digestibility and antioxidant activity.

417

Native rice starch underwent conformational changes with starch molecular coils

418

completely stretched when boiling water was treated. MD simulation results indicated


Page 20 of 40

Page 21 of 40


419

that the dodecyl segment would be entrapped within starch hydrophobic cavities, but

420

the gallate tail was left outside the amylose-like cavities (Fig. 1a). Experimental

421

performances, especially the DSC and XRD results, validated the formation of

422

starch-DG inclusion complexes. Apart from the inclusion complexes, ordered starch

423

molecular assemblies can also be reassociated based on the snapshots of MD

424

simulation. Although limited data can be used for the characterization of starch-DG

425

sandwich complex, the release behaviors of DG in SGF indicated that the DG

426

molecules also entrapped between starch chains and formed starch-DG sandwich

427

complexes. Generally, starch-lipids inclusion complexes are undigestible starch

428

fractions 38, however, rice starch complexation with DG in this work increased both of

429

RS and SDS content. This observation indicated that the starch assemblies and

430

starch-DG sandwich complexes may be the critical factors for SDS changes. The

431

related schematic presentation was shown in Fig. 7. Amylose and long branch chains

432

of amylopectin entrapped with DG tended to form enzyme-stable starch-DG inclusion

433

complexes. Starch reassemblies with highly ordered structures may also show with

434

enzymes resistance similar to the type III resistant starch (retrograded starch).

435

However, starch reassemblies arranged with lower orders still can be enzymatic

436

digested and contributed to the SDS enhancement. Our previous study found that

437

gallic acid can act as molecular chaperone to assist the assembly of starch molecules

438

45

439

under acidic and enzymatic treatments, indicating DG may also interact with starch

440

molecules and assist the formation of starch-DG sandwich complexes other than

. In this study, DG molecules were slowly released from DG-contained complexes



441

starch-DG inclusion complexes (schematically showed in Fig. 7). Notably, DG

442

molecules could slowly release in SIF, suggesting those starch-DG sandwich

443

complexes can be slowly digested and contributed to the enhancement of SDS content.

444

Because of these possible scenarios, SDS content of starch was increased after DG

445

complexation, and DG was slowly lost in the upper simulated GIT. These actions

446

enable the DG sustainable release in the upper GIT with efficient biological execution.

447

On the other hand, the residues of the complexes (i.e., the starch-DG inclusion

448

complexes) carried ca. 40%-60% of DG to the lower GIT. It is indicated that the DG

449

molecules can execute their biological activity when the amylose/long branch chains

450

of amylopectin-DG inclusion complexes were fermented by microflora in colon.

451

Therefore, it can be concluded that the SDS, in particular, the starch-DG sandwich

452

complexes, could be considered as a DG sustained released delivery carrier to the

453

upper GIT and RS, the amylose/long branch chains of amylopectin-DG inclusion

454

complexes, could be considered as a delivery carrier to target DG into the colon with

455

relatively potent antioxidant activity.

456

In summary, the in vitro enzymatic digestibility and antioxidant activity of

457

cooked rice starch complexation with DG were evaluated, and the mechanisms

458

involved in the structural changes and functionalities improvement were revealed.

459

MD simulation theoretically confirmed starch-DG inclusion complexes formation, by

460

entangling dodecyl segment in amylose cavities and blocking the gallate tail outside

461

the hydrophobic cavity. Experimental performances such as UV-vis spectroscopy,

462

calorimetric and crystalline measurements validated the favorable synthesis of


Page 22 of 40

Page 23 of 40


463

starch-DG inclusion complexes. Such DG-contained starch complexes showed low

464

susceptibility to enzymes and potent scavenging activity on DPPH radicals, and

465

moreover, acted as a carrier for targeting delivery of DG to human lower

466

gastrointestinal tract with potent antioxidant activity. Taken together, such a

467

DG-contained starch complex suggests a number of potential applications, including

468

ameliorating the postprandial glucose concentration and oxidative stress.

469

ACKNOWLEDGEMENTS The authors would thank the financial support received from the National Key

470 471

Research

472

NSFC-Guangdong Joint Foundation Key Project (U1501214), the NSFC (31771930,

473

31271824),

474

program(201804020036), YangFan Innovative and Entrepreneurial Research Team

475

Project (no. 2014YT02S029), the Science and Technology Program of Guangzhou

476

(201607010109), the Innovative Projects for Universities in Guangdong Province

477

(2015KTSCX006), the R&D Projects of Guangdong Province (2014B090904047),

478

and the Fundamental Research Funds for the Central Universities. Chengdeng Chi

479

also greatly appreciates the inimitable care and support from his lovely girlfriend,

480

Lily.

481

Notes

482

and

the

Development

key

Program

project

of

of

China

Guangzhou

The authors declare no competing financial interest.


(2016YFD0400401),

science

and

the

technology


483

Reference

484

(1) Maritim, A. C.; Sanders, R. A.; Watkins, J. B., Diabetes, oxidative stress, and

485

antioxidants: A review. J. Biochem. Mol. Toxicol. 2003, 17, 24-38.

486

(2) Brand-Miller, J., The glycemic index as a measure of health and nutritional

487

quality: An Australian perspective. Cereal Foods World 2007, 52, 41-44.

488

(3) Brand-Miller, J.; Dickinson, S.; Barclay, A.; Celermajer, D., The glycemic index

489

and cardiovascular disease risk. Current atherosclerosis reports 2007, 9, 479-85.

490

(4) Annison, G.; Topping, D. L., Nutritional role of resistant starch: chemical

491

structure vs physiological function. Annu. Rev. Nutr. 1994, 14, 297-320.

492

(5) Asp, N. G.; van Amelsvoort, J. M.; Hautvast, J. G., Nutritional implications of

493

resistant starch. Nutrition research reviews 1996, 9, 1-31.

494

(6) Noeman, S. A.; Hamooda, H. E.; Baalash, A. A., Biochemical Study of Oxidative

495

Stress Markers in the Liver, Kidney and Heart of High Fat Diet Induced Obesity in

496

Rats. Diabetol. Metab. Syndr. 2011, 3.

497

(7) Ceriello, A., Oxidative stress and glycemic regulation. Metabolism-Clinical and

498

Experimental 2000, 49, 27-29.

499

(8) Baynes, J. W.; Thorpe, S. R., Role of oxidative stress in diabetic complications -

500

A new perspective on an old paradigm. Diabetes 1999, 48, 1-9.

501

(9) Baynes, J. W., Role of oxidative stress in development of complications in

502

diabetes. Diabetes 1991, 40, 405-12.

503

(10) Young, I. S.; Tate, S.; Lightbody, J. H.; McMaster, D.; Trimble, E. R., The effects

504

of desferrioxamine and ascorbate on oxidative stress in the streptozotocin diabetic rat.


Page 24 of 40

Page 25 of 40


505

Free Radic. Biol. Med. 1995, 18, 833-40.

506

(11) Slavin, J. L.; Lloyd, B., Health Benefits of Fruits and Vegetables. Advances in

507

Nutrition 2012, 3, 506-516.

508

(12) Pandey, K. B.; Rizvi, S. I., Plant polyphenols as dietary antioxidants in human

509

health and disease. Oxid. Med. Cell. Longev. 2009, 2, 270-278.

510

(13) Ekström, L. M. N. K.; Henningsson Bok, E. A. E.; Sjöö, M. E.; Östman, E. M.,

511

Oat β-glucan containing bread increases the glycaemic profile. Journal of Functional

512

Foods 2017, 32, 106-111.

513

(14) Zhang, G.; Hamaker, B. R., Slowly Digestible Starch: Concept, Mechanism, and

514

Proposed Extended Glycemic Index. Crit. Rev. Food Sci. Nutr. 2009, 49, 852-867.

515

(15) Shi, M.; Loftus, H.; McAinch, A. J.; Su, X. Q., Blueberry as a source of bioactive

516

compounds for the treatment of obesity, type 2 diabetes and chronic inflammation.

517

Journal of Functional Foods 2017, 30, 16-29.

518

(16) Wojdyło, A.; Nowicka, P.; Carbonell-Barrachina, Á. A.; Hernández, F., Phenolic

519

compounds, antioxidant and antidiabetic activity of different cultivars of Ficus carica

520

L. fruits. Journal of Functional Foods 2016, 25, 421-432.

521

(17) Arun, K. B.; Thomas, S.; Reshmitha, T. R.; Akhil, G. C.; Nisha, P., Dietary fibre

522

and phenolic-rich extracts from Musa paradisiaca inflorescence ameliorates type 2

523

diabetes and associated cardiovascular risks. Journal of Functional Foods 2017, 31,

524

198-207.

525

(18)Velderrain-Rodríguez, G.; Palafox-Carlos, H.; Wall-Medrano, A.; Ayala-Zavala, J.;

526

Chen, C. O.; Robles-Sánchez, M.; Astiazaran-García, H.; Alvarez-Parrilla, E.;



Page 26 of 40

527

González-Aguilar, G., Phenolic compounds: their journey after intake. Food Funct.

528

2014, 5, 189-197.

529

(19) Si, X.; Zhou, Z.; Strappe, P.; Blanchard, C., A comparison of RS4-type resistant

530

starch

531

high-fat-diet-induced obese rats. Food Funct 2017, 8, 232-240.

532

(20) Zhou, Z. K.; Robards, K.; Helliwell, S.; Blanchard, C., Composition and

533

functional properties of rice. Int. J. Food Sci. Technol. 2002, 37, 849-868.

534

(21) Janette Brand Miller; Edna Pang; Bramall, L., Rice: a high or low glycemic index

535

food? Am. J. Clin. Nutr. 1992, 56, 1034-1036.

536

(22) Wang, H.; Liu, Y.; Chen, L.; Li, X.; Wang, J.; Xie, F., Insights into the multi-scale

537

structure and digestibility of heat-moisture treated rice starch. Food Chem. 2018, 242,

538

323-329.

539

(23) Guraya, H. S.; Kadan, R. S.; Champagne, E. T., Effect of rice starch-lipid

540

complexes on in vitro digestibility, complexing index, and viscosity. Cereal Chem.

541

1997, 74, 561-565.

542

(24) Chi, C.; Li, X.; Zhang, Y.; Chen, L.; Li, L., Understanding the mechanism of

543

starch digestion mitigation by rice protein and its enzymatic hydrolysates. Food

544

Hydrocolloids 2018, 84, 473-480.

545

(25) Shih, C.-K.; Chen, S.-H.; Hou, W.-C.; Cheng, H.-H., A high-resistance-starch rice

546

diet reduces glycosylated hemoglobin levels and improves the antioxidant status in

547

diabetic rats. Food Res. Int. 2007, 40, 842-847.

548

(26) Bamidele, O. P.; Duodu, K. G.; Emmambux, M. N., Encapsulation and

to

RS2-type

resistant

starch

in

suppressing


oxidative

stress

in

Page 27 of 40


549

antioxidant activity of ascorbyl palmitate with maize starch during pasting. Carbohydr.

550

Polym. 2017, 166, 202-208.

551

(27) Dries, D. M.; Knaepen, L.; Goderis, B.; Delcour, J. A., Encapsulation of the

552

antioxidant ascorbyl palmitate in V-type granular cold-water swelling starch affects

553

the properties of both. Carbohydr. Polym. 2017, 165, 402-409.

554

(28) Dries, D. M.; Gomand, S. V.; Pycarelle, S. C.; Smet, M.; Goderis, B.; Delcour, J.

555

A., Development of an infusion method for encapsulating ascorbyl palmitate in

556

V-type granular cold-water swelling starch. Carbohydr. Polym. 2017, 165, 229-237.

557

(29) Kaluza, W. Z.; McGrath, R. M.; Roberts, T. C.; Schroeder, H. H., Separation of

558

phenolics of Sorghum bicolor (L.) Moench grain. J. Agric. Food Chem. 1980, 28,

559

1191-1196.

560

(30) S. Nara; Komiya, T., Studies on the relationship between water‐satured state

561

and crystallinity by the diffraction method for moistened potato starch. Starch‐

562

Stärke 1983, 35, 407-410.

563

(31) Marinopoulou, A.; Papastergiadis, E.; Raphaelides, S. N.; Kontominas, M. G.,

564

Structural characterization and thermal properties of amylose-fatty acid complexes

565

prepared at different temperatures. Food Hydrocolloids 2016, 58, 224-234.

566

(32) Englyst, H. N.; Cummings, J. H., Digestion of the polysaccharides of some cereal

567

foods in the human small intestine. Am. J. Clin. Nutr. 1985, 42, 778-787.

568

(33) Pu, H.; Chen, L.; Li, X.; Xie, F.; Yu, L.; Li, L., An oral colon-targeting controlled

569

release system based on resistant starch acetate: synthetization, characterization, and

570

preparation of film-coating pellets. J. Agric. Food Chem. 2011, 59, 5738-45.



Page 28 of 40

571

(34) Xie, M.; Hu, B.; Wang, Y.; Zeng, X., Grafting of gallic acid onto chitosan

572

enhances antioxidant activities and alters rheological properties of the copolymer. J.

573

Agric. Food Chem. 2014, 62, 9128-36.

574

(35) Robert J. Woods; Raymond A. Dwek; Edge, C. J., Molecular mechnical and

575

molecular

576

GLYCAM_93 parameter development. The journal of Physical Chemistry 1995, 99,

577

3832-3846.

578

(36) Homeyer, N.; Horn, A. H. C.; Lanig, H.; Sticht, H., AMBER force-field

579

parameters for phosphorylated amino acids in different protonation states:

580

phosphoserine, phosphothreonine, phosphotyrosine, and phosphohistidine. J. Mol.

581

Model. 2006, 12, 281-289.

582

(37) Chang, F.; He, X.; Huang, Q., Effect of lauric acid on the V-amylose complex

583

distribution and properties of swelled normal cornstarch granules. J. Cereal Sci. 2013,

584

58, 89-95.

585

(38) Dupuis, J. H.; Liu, Q.; Yada, R. Y., Methodologies for Increasing the Resistant

586

Starch Content of Food Starches: A Review. Comprehensive Reviews in Food Science

587

and Food Safety 2014, 13, 1219-1234.

588

(39) Chen, B.; Jia, X.; Miao, S.; Zeng, S.; Guo, Z.; Zhang, Y.; Zheng, B., Slowly

589

digestible properties of lotus seed starch-glycerine monostearin complexes formed by

590

high pressure homogenization. Food Chem. 2018, 252, 115-125.

591

(40) Chang, F.; He, X.; Fu, X.; Huang, Q.; Jane, J. L., Effects of heat treatment and

592

moisture contents on interactions between lauric acid and starch granules. J. Agric.

hynamic

simulations

of

glycoproteins


and

oligosaccharides.

1.

Page 29 of 40


593

Food Chem. 2014, 62, 7862-8.

594

(41) Zhang, L.; Cheng, H.; Zheng, C.; Dong, F.; Man, S.; Dai, Y.; Yu, P., Structural

595

and release properties of amylose inclusion complexes with ibuprofen. J. Drug Deliv.

596

Sci. Technol. 2016, 31, 101-107.

597

(42) Le Bail, P.; Bizot, H.; Ollivon, M.; Keller, G.; Bourgaux, C.; Buleon, A.,

598

Monitoring the crystallization of amylose-lipid complexes during maize starch

599

melting by synchrotron x-ray diffraction. Biopolymers 1999, 50, 99-110.

600

(43) Tusch, M.; Kruger, J.; Fels, G., Structural Stability of V-Amylose Helices in

601

Water-DMSO Mixtures Analyzed by Molecular Dynamics. J. Chem. Theory Comput.

602

2011, 7, 2919-28.

603

(44) Monagas, M.; Urpi-Sarda, M.; Sanchez-Patan, F.; Llorach, R.; Garrido, I.;

604

Gomez-Cordoves, C.; Andres-Lacueva, C.; Bartolome, B., Insights into the

605

metabolism and microbial biotransformation of dietary flavan-3-ols and the

606

bioactivity of their metabolites. Food Funct. 2010, 1, 233-253.

607

(45) Chi, C.; Li, X.; Zhang, Y.; Chen, L.; Li, L.; Wang, Z., Digestibility and

608

supramolecular structural changes of maize starch by non-covalent interactions with

609

gallic acid. Food Funct. 2017, 8, 720-730.

610 611 612 613 614 615 616



617

Figure captions

618

Fig. 1 Snapshots (a) and root mean square deviation (RMSD) (b) of starch/DG system

619

during the simulation.

620

Fig. 2 UV-vis spectra of native rice starch, cooked rice starch (CRS) and CRS-DG

621

complexes. CRS+DG is the physical mixture of DG and starch.

622

Fig. 3 DSC thermograms of native rice starch, cooked rice starch (CRS) and CRS-DG

623

complexes.

624

Fig. 4. X-ray diffraction patterns of native rice starch, cooked rice starch (CRS) and

625

CRS-DG complexes.

626

Fig.5 In vitro DG released from the starch-DG complexes in simulated gastric fluid

627

(SGF) and simulated intestinal fluid (SIF).

628

Fig. 6. DPPH radicals scavenging activity of (a) native DG-starch complexes and (b)

629

residues of DG-starch complexes which were digested in simulated gastric fluids and

630

intestinal fluids.

631

Fig. 7. Schematic representation of rice-DG inclusion complexes.

632 633 634 635 636 637 638 639 640 641 642


Page 30 of 40

Page 31 of 40


643

Fig. 1 (a)

644

dianfen DG

35

(b)

Starch DG

30

RMSD (nm)

25 20 15 10 5 0

645

0

10000 10

20000 20

30000 30

Time(ns) (ps) Time

646 647 648


40000 40

50000 50


Fig. 2

CRS-9 CRS-5 CRS-1 CRS+DG CRS DG

Absorbance(a.u.)

649

Page 32 of 40

200

250

300

350

Wavelength (nm)

650 651 652 653 654 655 656 657 658 659 660 661 662 663


400

Page 33 of 40


Fig. 3

Heat flow endo up (mW)

664

CRS-9 CRS-5

Peak I

Peak II

CRS-1 CRS G Rice starch 60

80

100 o

Temperature ( C)

665 666 667 668 669 670 671 672 673 674 675 676 677 678 679


120


Fig. 4

Intensity (a.u.)

680

CRS-9 CRS-5 CRS-1 CRS rice starch DG 10

681

20

30

2 theta (°)

682 683 684 685 686 687 688 689 690 691 692 693 694


40

Page 34 of 40

Page 35 of 40


695

Fig. 5 80 SIF

DG release percentage (%)

SGF

60

40

20 CRS-1 CRS-5 CRS-9

0 0

2

4

6

Time (h)

696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714


8


715

Page 36 of 40

Fig. 6

Scavenging DPPH radicals (%)

100

80

60

(a) 40

20 rice starch CRS-1 0 0.0

0.5

1.0

CRS-5

1.5

Vc CRS-9

2.0

2.5

Concentration (mg/mL)

716

Scavenging DPPH radicals (%)

100

80

(b) 60

40

20

Vc CRS-5-R

CRS-1-R CRS-9-R

0 0.0

0.5

1.0

1.5

2.0

Concentration (mg/mL)

717 718 719 720 721 722 723 724 725 726


2.5

Page 37 of 40


727

Fig. 7

728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745



Page 38 of 40

746

Table 1. DG content and crystal parameters of native rice starch, cooked rice starch

747

(CRS) and CRS-DG complexes.

748 749

rice starch

CRS

CRS-1

CRS-5

CRS-9

DG content (mg/g)

0.07d#

0.09d#

7.91c

27.93b

48.15a

Crystallinity (%)

26.8d

11.1e

28.2c

29.9b

30.9a

V type crystal (%)

6.91e

13.97d

18.08c

25.81b

28.36a

Crystallite size (Å)

14.44c

14.47c

46.12b

47.61a

47.74a

a,b,c

Values within the same line with different superscript letters are significantly different (P < 0.05).

750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769


Page 39 of 40


770

Table 2. Thermal transition parameters of native rice starch, cooked rice starch (CRS)

771

and CRS-DG inclusion complexes. Peak

Sample

To (°C)

Te (°C)

∆H (J/g)

G

Rice starch

60.13g#

77.56g

15.21a

CRS

98.22e

106.68d

0.79e

CRS-1

86.97f

96.56f

1.18d

CRS-5

87.08f

102.72e

2.12c

CRS-9

102.52d

114.11c

3.23b

CRS-1

109.27c

114.66c

0.33g

CRS-5

112.49b

119.89b

0.65f

CRS-9

118.02a

122.59a

0.67f

Peak I

Peak II

772 773

#

Values within the same column with different superscript letters are significantly different (P < 0.05).

774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790



Page 40 of 40

791

Table 3. Digestibility of rice starch, cooked rice starch (CRS) and CRS-DG

792

complexes. Sample

793 794

RDS%

SDS%

RS%

rice starch

93.83 ± 2.13a

3.10 ± 0.38c

3.05 ± 1.07c

CRS

95.24 ± 3.65a

2.90 ± 1.59c

1.85 ± 1.43c

CRS-1

86.19 ± 2.50b

5.12 ± 2.98c

8.69 ± 2.48b

CRS-5

73.16 ± 1.31c

16.74 ± 1.03b

10.09 ± 1.31b

CRS-9

62.70 ± 3.65d

22.83 ± 3.99a

14.17 ± 1.14a

a,b,c

Values within the same column with different superscript letters are significantly different (P < 0.05).

795


Improvement in Nutritional Attributes of Rice Starch with Dodecyl

Recommend Documents