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Accepted Manuscript
Effect of ionic gums and dry heating on physicochemical, morphological, thermal andpasting properties of water chestnut starch
Khalid Gul , Charanjit Singh Riar , Anu Bala , Mandeep Singh Sibian
PII: S0023-6438(14)00265-5
DOI: 10.1016/j.lwt.2014.04.060
Reference: YFSTL 3896
To appear in: LWT - Food Science and Technology
Received Date: 25 June 2013
Revised Date: 21 April 2014
Accepted Date: 26 April 2014
Please cite this article as: Gul, K., Riar, C.S., Bala, A., Sibian, M.S., Effect of ionic gums and dry heatingon physicochemical, morphological, thermal and pasting properties of water chestnut starch, LWT -Food Science and Technology (2014), doi: 10.1016/j.lwt.2014.04.060.
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Effect of ionic gums and dry heating on physicochemical, morphological, 1
thermal and pasting properties of water chestnut starch 2
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1,2Khalid Gul*, 1Charanjit Singh Riar, 1Anu Bala, 1Mandeep Singh Sibian 4
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1Department of Food Engineering & Technology, Sant Longowal Institute of Engineering 6
& Technology, Longowal, Punjab, 148106, India 7
2Department of Processing & Food Engineering, Punjab Agricultural University, 8
Ludhiana, 141004, India 9
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*Corresponding Author: 29
Khalid Gul 30
E mail: [email protected] 31
+91-1932-241538 32
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Abstract: 34
Starch from water chestnuts (Trapa natans) was isolated and modified by dry heating and 35
hydrocolloids [Carboxy Methyl Cellulose (CMC) and Sodium Alginate]. Native and modified 36
starches were evaluated for their physicochemical, pasting, thermal and morphological 37
properties. Pasting and thermal properties were studied using Rapid Visco Analyzer (RVA) 38
and Differential Scanning Calorimeter (DSC) respectively. Morphological properties were 39
studied by Scanning Electron Microscopy (SEM). Modification of the starch by dry heating 40
with and without gums reduced paste clarity and increased the water and oil binding capacity; 41
solubility and swelling power decreased. Dry heating of native starch increased peak viscosity; 42
however, with addition of CMC, peak viscosity decreased. Starch modified with CMC and 4 h 43
heating exhibited lowest gelatinization temperature (T0). Pasting characteristics of native water 44
chestnut starch were largely affected by the addition of gums and/or heat treatment. Over all 45
onset gelatinization temperature reduced with heat treatment and addition of gums. 46
Morphological studies revealed no significant variation in starch granule size. Starch granules 47
were seen agglomerated because of leaching of amylose and granule interspacing decreased 48
with addition of gums. 49
Key words: Water chestnut starch, ionic gums, physicochemical properties, pasting, thermal 50
properties 51
1. Introduction: 52
Water chestnut (Trapa natans), locally known as ‘Singhara’, is an edible aquatic 53
angiospermic plant found commonly on the water surfaces of lakes and ponds. Water chestnut 54
kernel, triangular in shape, is covered with dark brown skin with small spikes at the top. The outer 55
cover of the kernel is hard making it difficult to peel off to obtain the white meat (edible portion) 56
inside. Water chestnut is an important commodity in food industry because of its unique taste 57
(Parker & Waldren, 1995). Importance of water chestnut in Kashmir dates back to times of Sir 58
Walter Lawrence; when the main crop of the valley was destroyed due to floods in 1893 the flour 59
of ‘Singhara’ (Water chestnut) saved people from starvation (Lawrence, 1895). The fruit is used as 60
a substitute for cereals in Indian subcontinent during fasting days. The fruits are usually eaten raw 61
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at tender stage and sometimes after boiling and roasting. Lot of research has been carried out on 62
starch from corn, rice, wheat, potato starches (Medcalf & Giles, 1965; Svegmark & Hermanson, 63
1993; Singh & Singh, 2001; Raina, Singh, Bawa & Saxena, 2006; Sandhu, Singh & Lim, 2007), 64
etc. Starch industry is continuously looking for new sources (Kong, Kasapis, Bao & Corke, 2009; 65
Wani, Sogi, Wani, Gill & Shivhare, 2010; Kaur, Ariffin, Bhat & Karim, 2012; Wani, Singh, Shah, 66
Wani, Gotz, Schott & Zacherl, 2013) to offset the production costs and to meet growing demand 67
for novel starches in food, cosmetic and pharmaceutical applications. The demand of starch has 68
increased enormously in recent years as starch is being widely used in production of ethanol and 69
biodegradable plastics (Wani, Singh, Shah, Schweiggeret- Weisz, Gul & Wani, 2012) apart from 70
being used in food processing industries. Hence, search for novel starches is always a focus of the 71
starch industry. 72
Water chestnut an underutilised starch source has been poorly understood for modification 73
and utilization in food industry. Water chestnuts are cheaply available and promising with regards 74
to the starch content. The bulk of the edible region of water chestnut consists of starch-rich thin 75
walled storage parenchyma similar in appearance to potato, interspersed with vascular strands. 76
However, in contrast to other sources like potato and rice, water chestnut is notable for its ability to 77
maintain a firm and crunchy texture after considerable heat treatment during canning or cooking 78
(Singh, Singh, Bawa & Saxena, 2009). Water chestnuts principally having large quantities of 79
starch can be used as a source of starch for industrial applications in food and allied industries. A 80
detailed knowledge of the characteristics of water chestnut starch would facilitate its utilization in 81
industries; enable tailoring of the properties by physical or chemical modification to specific 82
applications and bring economic benefit to the people. Native starch has got some limitations with 83
their use in food industry. To overcome the shortcomings, native starch is modified to increase its 84
usefulness in industrial applications. Therefore, focus of the study was to analyze the effects of 85
modification with ionic gums (CMC & Sodium Alginate) and heat treatment on water chestnut 86
starch. 87
2. Material & Methods 88
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Fully mature water chestnuts were procured from Wular Lake, Asia’s largest fresh water lake 89
in Bandipora, Jammu and Kashmir, India. Samples were collected at the time of harvest and stored 90
at 4˚C till further use. Carboxy methyl cellulose was procured from Central Drug House (CDH) 91
Laboratory Reagents, New Delhi and Sodium Alginate was procured from S. D. Fine Chemicals 92
Ltd, Mumbai, India. 93
2.1 Isolation of starch 94
Starch was isolated from water chestnuts with slight modifications to the method described by 95
Vanna, Khajee & Thanachan, (2004). The hard skin of water chestnuts was removed manually and 96
white kernels obtained were dipped in 0.1g/100g aqueous potassium metabisulphite (KMS) 97
solution for 30 min. After grading to obtain fruits of same size, selected fruits were peeled, washed 98
and cut into small pieces. Representative samples of 1 kg were ground in a blender with 2L of 99
0.2g/100g sodium hydroxide. The homogenate was filtered through a 75µm mesh sieve and 100
centrifuged at 3000 x g for 30 min at 10˚C (C-24, BL; Remi Laboratory Industries, Mumbai, 101
India). 102
The sediment was recovered and again suspended with two volumes of water and centrifuged. 103
Washing steps were repeated until clear supernatant and traces of alkali were no longer found. 104
Starch solution was filtered through a buchner funnel under vacuum to remove the water. The 105
filtered cake obtained was dried in an oven at 40˚C to less than 10 g/100g moisture content. Starch 106
was ground gently with mortar and pestle and passed through 75µm sieve, packed in airtight 107
plastic bags and stored in refrigerated conditions at 4˚C. 108
2.2 Modification of starch 109
Modification of water chestnut starch, shown in Table 1, was carried out by the method as 110
described by Lim, BeMiller, Han & Lim, (2002). Modification of starch was carried out by dry 111
heating of starch with and without ionic gums (Sodium alginate and Carboxy Methyl Cellulose 112
(CMC)). Initially sodium alginate & CMC, (0.4g) was slowly added in distilled water (70ml) 113
separately with vigorous stirring using a magnetic stirrer. Starch (39.6g) was added to the prepared 114
gum solutions, and the dispersion was stirred continuously for 30 min at room temperature. 115
Separately prepared dispersions were transferred into a glass dish and dried at 45˚C in an oven to a 116
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moisture content of <10 g/100g, based on starch. The starch gum mixture was heated in an electric 117
oven at 130˚C for 2 and 4 hours separately in two lots. The starch sample itself was concurrently 118
heat treated without gums under identical conditions. 119
2.3 Physicochemical properties 120
2.3.1 Moisture and ash 121
Moisture content (g/100g) and ash content (g/100g) were determined by A.O.A.C, 1995 122
methods. 123
2.3.2 Total carbohydrate content 124
Total carbohydrate was quantified by phenol sulphuric acid method as described by 125
Dubois, Gilles, Hamilton, Rebers & Smith, (1956) and as modified by Wankhede, & Tharanthan, 126
(1976). 127
Starch sample (0.5g, dry weight basis) was weighed in a test tube and kept in ice water bath 128
for few minutes followed with addition of 2 ml cold sulphuric acid (72ml/100ml) with gentle 129
stirring. The viscous paste was prepared by pinching with glass rod and it was diluted with distilled 130
water (23ml) to obtain a final concentration 2 ml equi/L with respect to acid. It was then 131
hydrolyzed at 98˚C in a water bath for 3-4 h. The sample was filtered and the volume was made to 132
100 ml. One ml was taken and volume make up to 50 ml was done. Further, one ml from 50 ml 133
sample solution was taken and 0.2 ml of 5ml/100ml phenol was added. 134
The Standard glucose solution was prepared by weighing 100 mg of glucose in a beaker in 135
which 25 ml of distilled water were added. The standard working solution was made by diluting a 136
known amount of stock glucose solution to prepare calibration curve. 137
2.3.3 Amylose content 138
The amylose content was determined by using the method described by Scott, Hugh & 139
Colin, (1998). The reagents used were distilled ethanol, 1 ml equi/L NaOH, 0.1ml/100ml 140
Phenolphthalein, Iodine reagent (dissolved 10g KI + 1g iodine in water and made up to 500 ml), 141
potato standard amylose (dissolved 0.1g amylose in 10 ml 1 ml equi/L NaOH made volume up to 142
100 ml with demineralized water). 143
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Starch sample (0.1g) in the powdered form was weighed. To this 1ml of distilled ethanol 144
was added. Then 10ml of 1 ml equi/L NaOH was added and left overnight. On the following day, 145
the volume was made up to 100ml with distilled water. Extract, 2.5 ml, was taken and about 20ml 146
distilled water was added followed by three drops of phenolphthalein indicator. To this, 0.1 ml 147
equi/L HCl drop by drop was added until the pink color just disappeared. One ml iodine reagent 148
was added, volume was made up to 50ml and color was read at 590nm. Standard amylose 0.2, 0.4, 149
0.6, 0.8, and 1 ml was taken and the color was developed as in the case of sample for preparing 150
standard curve. One ml of iodine reagent was diluted to 50ml with distilled water and used as 151
blank. Wavelength was recorded at 590nm on spectrophotometer (I D 5000 HACH, USA). 152
Absorbance corresponds to 2.5ml of the test solution = X g amylose 153
100�������� =�
2.5× 100�������� = �������(�/100�)
2.3.4 Swelling power (g/g H2O) and solubility (g/100g) 154
Swelling power (SP) and solubility were determined with slight modifications to the 155
methods described by Wang, Xie, Shi, Xue, Deng, Wei & Tian, (2010). 156
2. 3.5 Paste clarity 157
The clarity (% transmittance at 650 nm) of starch paste was determined with slight 158
modifications to the method described by Sandhu and Singh, (2007). Aqueous solution of starch, 159
1g/100g, near neutral pH was heated in boiling water bath for 30 min with intermittent shaking. 160
After that the suspension was cooled for 1h to 25˚C. The light transmittance was read at 650 nm 161
against water blank. 162
2.3.6 Water binding/ Oil binding capacity 163
Water binding capacity and oil binding capacity of starch were determined using the 164
method described by Yamazaki (1953), as modified by Medcalf and Giles (1965). 165
2.4 Thermal properties 166
The thermal properties of native and modified water chestnut starches were studied using a 167
Differential Scanning Calorimeter (DSC821, Cryofill and Autosampler, Mettler Toledo) equipped 168
with a thermal analysis data station. Starch (3mg, dry weight basis, dwb) was loaded into a 40µL 169
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capacity aluminium pan, and distilled water was added with the help of a Hamilton micro syringe 170
to achieve a starch– water suspension containing 70ml/100ml water. Pans were hermetically sealed 171
and allowed to stand for 1 h at room temperature before heating in DSC. The DSC was calibrated 172
using indium, and an empty aluminium pan was used as a reference. Sample pans were heated at a 173
rate of 10˚C/min from 20 to 100˚C. The parameters of onset (To), peak (Tp), conclusion (Tc) 174
temperature and enthalpy (∆H) of gelatinization were calculated directly from the DSC curves 175
using thermal analysis data station supplied with the instrument. 176
2.4 Pasting properties 177
Pasting properties were determined using a rapid visco analyzer (RVA Starch Master TM; 178
model N17133; Newport Scientific Pvt. Ltd., Warriewood, Australia). The test profile standard1 179
was used for determination of pasting characteristics. Starch sample (3g) was dispersed in water 180
(25 ml) and stirred in an RVA container initially at 960 rpm for 10 s and finally at 160 rpm for the 181
remaining test. The temperature profile was started from 50˚C for 1 min followed by a linear 182
temperature ramp to 95˚C in 3 min and 42 s, holding for 2 min and 30 s, cooling the system to 183
50˚C in 3 min. The following data were recorded: peak viscosity (PV); temperature at which peak 184
viscosity was reached (Ptemp); viscosity at the end of hold time at 95˚C or hot paste viscosity 185
(HPV); viscosity at the end of the hold time at 50˚C or cold paste viscosity (CPV). 186
2.5 Morphological properties 187
Morphological properties of native and modified water chestnut starch were studied by using 188
a scanning electron microscope (Jeol JSM- 7500, Joel Ltd, Tokyo, Japan). Starch granules were 189
placed on SEM stub using double-sided cellophane tape and then coated with gold. An accelerated 190
potential of 10kV was used during micrography. 191
2.6 Statistical analysis 192
Experimental data was analyzed by analysis of variance (ANOVA), and means were 193
compared using Duncan’s multiple range tests with significance defined at P≤0.05. All statistical 194
analysis was performed using commercial statistical package SPSS (16.0, Chicago, IL, USA). 195
3 Results and Discussions 196
3.1 Physicochemical properties 197
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Physicochemical properties of native and modified water chestnut starches are reported in 198
Table 2. The moisture content of the native starch was found to be 9.8g/100g. However, reduced 199
values of moisture content were observed for modified starches. Overall moisture content in native 200
and modified starches varied from 9.81-4.24g/100g. Starch (with or without gums), which was not 201
exposed to heat treatment showed higher moisture content ranging from 9.12 -9.81 g/100g. 202
Addition of gums influences concentration while heat energy dissipates radiations which penetrate 203
the starch sample. This might have caused decrease in the moisture content of modified starches. 204
There was a significant difference (p<0.05) in ash content among modified starch samples 205
as compared to the control sample. Ash content of the modified starch varied from 0.34-206
0.74g/100g. This may be due to addition of gums to modified samples and leaching of minerals 207
from the blank sample. Starch modified with sodium alginate gum showed higher ash content 208
(0.73-0.74 g/100g) while as starch modified with carboxy methyl cellulose had slightly lesser 209
values of ash content (0.68-0.69g/100g). 210
There was a significant difference (p<0.05) in amylose content among modified starches 211
when compared with the control starch. The amylose content varied from 28.77-24.43 g/100g. 212
Significant difference in carbohydrate content between different modified starches when compared 213
to control starch was seen. The total carbohydrate content varied from 70.01-76.56 g/100g. Starch 214
gum mixtures showed increase in the amount of carbohydrate content while it concomitantly 215
decreased in starch gum mixtures with increase in dry heat treatment. 216
There was a significant difference (p<0.05) in swelling power and solubility among 217
modified starch samples as compared to the control samples. Starch is insoluble in cold water 218
owing to its crystalline structure. Starch swells as it gets dissolved in hot water, swelling being 219
rapid during the first 5-10 min at a certain temperature. The solubility is contributed by the content 220
of amylose, and the swelling power is contributed by the content of amylopectin (Tester and 221
Morrison, 1990); and the amylose and amylopectin ratio has also been attributed to affect the 222
swelling power of starches (Wani, Sogi, Wani, Gill & Shivhare, 2010). Water chestnut, having 223
higher amylose content exhibits higher swelling power. 224
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Figure 1 shows changes in swelling power with heat treatment at different time durations. 225
The heating of the starch with and without gums caused decrease in the swelling power of all 226
starches. The heating of starch at high temperature resulted in starch damage which leads to 227
restricted swelling of the starch thus reduced swelling power (Table 3) as seen in all the starches 228
modified by heat treatment. 229
Changes in solubility index of control and modified starches are shown in Figure 2. 230
Solubility of starch decreased as the heating time increased. Hydrocolloids interacted with the 231
amylose outside the starch granules to produce a more complex matrix of amylose and 232
hydrocolloid surrounding the gelatinized granules (Kruger, Ferrero, & Zaritzky, 2003). The 233
modification caused restricted swelling of starches which could decrease the swelling power of 234
modified starches. The modification of starch with sodium alginate showed significant changes in 235
the solubility and modifications with CMC showed substantial decrease in the solubility of 236
starches. There is a possibility of formation of ester bonds between the starch and CMC when the 237
starch and gum mixture were dry-heated. The swelling inhibiting effect produced by the CMC is 238
more severe than that produced by sodium alginate in case of all the starches. 239
Transmittance is the fraction of incident light (or other electromagnetic radiation) at a 240
specified wavelength that passes through a sample. The percent transmittance (%T) was measured 241
as a function of wavelength for various starch pastes. Stuart, Claduaoldoc, Paul & Hosenney, 242
(1989) observed that more opaque pastes gave a lower %T. There was significant difference 243
(p<0.05) in paste clarity among modified starch samples as compared to control starch. 244
Paste clarity of investigated starches is shown in Figure 3.The paste clarity of native water 245
chestnut starch was 6.9. When the starch was heat treated at 130˚C, paste clarity decreased with 246
increase in heat treatment. Paste clarity decreased from 6.9 to 4.6%. The decrease in paste clarity is 247
attributed to the fact that when starch suspensions were heated with high temperature, the granules 248
rupture and get dispersed causing leaching of amylose. The chain of amylose breaks to shorter 249
chains as the temperature and time of heating increases. Upon cooling the amylose molecules re-250
associate to form a network during retrogradation. This causes cloudiness in the paste and increase 251
in absorbance. Also, the gums bind with the leached amylose outside of the granules thus aid the 252
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opaque paste formation. Similar results were found by Lim, BeMiller, Han & Lim, (2002) for 253
potato and waxy maize starch. 254
Water binding capacity reflects the water absorption of the starch granule and the degree 255
of association of the molecules within the starch granule (Leach McCowen, & Schoch, 1959; 256
Medcalf and Giles, 1965). When starch granules are dispersed in water, the water molecules form 257
a hydrated layer with the hydrophilic hydroxyl groups. Water chestnut starch has large granules 258
and there is increased water binding capacity than other starches. 259
There was significant difference (p<0.05) in water binding capacity among modified 260
starch samples as compared to native ones. Variations in water binding capacity among control 261
and various modified starches are shown in Table 3. Effect of modification on water binding 262
capacity is shown in Figure 4. Dry heating of starch caused starches to show more water binding 263
capacity as compared to the control starches at a significant (p≤0.05) level. The water binding 264
capacity of the starch increased with increase in the heat treatment duration from 2-4 h. The 265
heating might result in exposure of the hydrophilic groups for water binding. Modification of 266
starch with ionic gums caused increase in water binding capacity. Addition of the gums added 267
carboxyl groups in the starches leading to more absorption of water into matrix. During heating of 268
the starch, the alginate and starch interaction increased and provided more surfaces (amorphous 269
region) for the water absorption. 270
Dry heating of starch caused increase in its oil binding capacity. Heating of starch for a 271
long time increased its lipophilic character. There was significant difference (p<0.05) in the oil 272
binding capacity between modified starch samples as compared to control starch samples (Table 273
3). The oil binding capacity of starch increased from 122.32 -167.1 g/g when heated for 4 h. 274
Moisture content of starch before heating, temperature and time duration all affect the oil binding 275
capacity of starch (Seguchi, 1984). Effect of modification on oil binding capacity of water chestnut 276
starch is shown in Figure 5. Modification of starch with gums further increased its oil binding 277
capacity. Sodium alginate and carboxy methyl cellulose are observed to enhance the lipophilic 278
character of the starch. Addition of sodium alginate increased the oil binding capacity of starch to 279
a greater extent as compared to starch modified with carboxy methyl cellulose. Lipophilic 280
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character further increased with increased heating time. Thus oil binding capacity of starch 281
modified with sodium alginate increased from 157.1-167.1 g/g. Oil binding capacity of starch 282
modified with carboxy methyl cellulose followed the similar pattern and increased from 140.1-283
151.1 g/g with increase in heating time duration. 284
3.2 Pasting properties 285
The overall effect of modification on the pasting properties of water chestnut starch is 286
shown in Table 4. There was a significant difference (p<0.05) in pasting properties among 287
modified starches as compared to control starch. 288
Peak viscosity of the starch was affected by the gums, although the presence of gums 289
enhanced the heating affects. Heating of starch resulted in substantial increase in viscosities. The 290
increased paste viscosity might be due to structural disruption of starch granules during heating. 291
When heating time increased from 2 to 4 h the final viscosity, breakdown viscosity and set back 292
viscosity showed a significant increase; this might be due to alteration of amorphous region of 293
granules. However, with addition of gums, there was a significant decrease in the peak viscosity. 294
Heat treatment and addition of ionic gums may cause a change in the packing arrangement of the 295
polymer chains and also cause partial crystal melting in hydrothermally treated starches. Similar 296
results for decrease in viscosity were reported by Tsakama, Mwanwela, Mananai, & Mahungu, 297
(2011) for eleven sweet potato varieties and Lim et al., (2002) for waxy and corn starch. 298
The pasting temperature and time significantly increased (p≤0.05) after modification 299
possibly because of increase in crystallinity. This was possibly initiated by incipient swelling and 300
the resulting mobility of the amorphous granules which facilitated ordering of the amylose double 301
helices. Treatment of starch with carboxy methyl cellulose (CMC) showed significant changes in 302
the pasting properties of starch as compared to native starch. Starch with CMC and without heat 303
treatment exhibited lowest peak viscosity. This might be due to the fact that ionic gums like CMC 304
and sodium alginate get adhered to the starch granules and net negative charge prevails on the 305
surface which prevents water molecules from reaching starch granules, delaying starch granule 306
swelling (Lim et al., 2002; Lim, BeMiller & Lim, 2006; Sim, Cheng & Noor Azia, 2009). After 307
heating starch impregnated with CMC for 2 h at 130˚C the peak viscosity and final viscosity 308
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increased by 664cP and 692cP respectively. The viscosity at 4 h decreased from 2 h heated 309
sample, but was higher than the control (i.e. no drying). Increase in paste viscosity was more 310
significant on addition of gums followed by heating. The reason may be that the CMC being 311
reactive than sodium alginate gets impregnated more into the starch in aqueous solution and thus 312
results in elevated peak and final viscosity (Lim et al., 2006). 313
Addition of sodium alginate without heat treatment increased the peak and final viscosity 314
of starch as compared to control starch to a slight extent. The increase in viscosity by sodium 315
alginate was lesser than that exhibited by the starch modified with CMC. After heating starch 316
impregnated with sodium alginate for 2 h, the peak viscosity increased to 4299cP from 3569cP 317
which was shown by starch impregnated with sodium alginate devoid of any heating treatment. 318
The reason may be that when starch is heated, the residual moisture is driven off and thus 319
facilitates interaction between carboxyl group in alginate and hydroxyl group in starch. 320
3.3 Thermal properties 321
Starch gelatinization is the collapse (disruption) of molecular orders within the starch 322
granule manifested in irreversible changes in properties such as granular swelling, native 323
crystalline melting, loss of birefringence, and starch solubilization (Atwell, Hood, Lineback, 324
Varriano-Marston & Zobel, 1988). There was significant difference (p<0.05) in pasting properties 325
among modified starch samples as compared to control starch. 326
The temperatures and enthalpy of gelatinization of investigated starches is shown in Table 327
5. The heat treatment provided changes in starch gelatinization. When water chestnut starch 328
without gums was heated, gelatinization temperature decreased with increase in heat treatment 329
from 2 h to 4 h (70.53 to 69.46˚C). This might be due to structural disruption of starch granules on 330
heating. Similar results have been reported by Lim et al., (2006). Starch heated for 2 h exhibited 331
lowest gelatinization temperature of 31.51˚C amongst all heated and non heated native starches. 332
There was a deviation that higher enthalpy rate was seen for 4 h heated native starch. When heated 333
to 4 h, the T0 decreased to 69.46˚C and ∆H increased to 17.3 J/g respectively. 334
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In presence of sodium alginate prior to heating, T0 increased by around 1˚C only and 335
increased with application of heat treatment. It is supposed that ionic strength by addition of 336
sodium alginate inhibited gelatinization and thus enhanced gelatinization temperature. It may also 337
be because of the size of gum molecule; the interactions between starch and gum molecules are 338
highly restricted. With addition of carboxy methyl cellulose (CMC), the onset temperatures 339
reduced to lowest value of 31.26˚C in case of 4 h heated sample. Similarly, the lowest enthalpy 340
value of 0.99J/g was exhibited by starch impregnated with CMC and heated to 4 h. The decrease in 341
T0, Tp and ∆H may be due to heat induced disintegration of starch granules. 342
3.4 Morphological properties 343
The micrographs taken from scanning electron microscope for native and modified water 344
chest nut starch are presented in Figure 6. Granule size and distribution of starch are important 345
properties of starch that have an influence on the functionality of starches (Rasper, 1971). The 346
starch granules size varied from 2-27µm and the shape was oval, round, polygonal, round 347
polygonal and bell. There was little effect of modification on granular size of the starch granules. 348
The average granule size in starch treated with Sodium alginate was higher (26µm) than that in 349
starch treated with CMC (21µm). The scanning electron micrographs of modified starch showed 350
no cluster formation, however, loss of the smoothness; development of cracking had occurred 351
which may be due to leaching of amylose and the effect of heating. The surface fracturing of the 352
granules increased with heat treatment. However, no such cracking was seen in starch heated for 2 353
h and impregnated with CMC. All agglomerated starch showed a spherical shape as a result of 354
modification with gums. It was evident that there was no significant loss of surface morphology, 355
except for cracking of granules by modification methods employed. 356
4. Conclusion 357
This study documented the physicochemical, pasting, thermal and morphological 358
properties of water chestnut starch as affected by modification with ionic gums and dry heating. In 359
general, the solubility, swelling power and paste clarity decreased with modification. Dry heating 360
of native starch increased peak viscosity; however, with addition of CMC, there was a decrease in 361
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peak viscosity. Starch sample modified with CMC and 4 h heating exhibited lowest gelatinization 362
temperature. 363
The thermal properties decreased with modification which is in agreement to previous 364
reports for other modified starches. Also reduced pasting parameters were observed which is also 365
in agreement with previously reported studies. 366
Scanning electron micrographs showed surface cracking which had occurred due to heat 367
treatment, starch granules were agglomerated because of leaching of amylose and granule 368
interspacing decreased with addition of gums. 369
Decreased solubility of investigated starch makes it applicable for flavour encapsulation 370
for controlled release while reduced swelling power makes it useful for improvement of texture 371
upon cooking. 372
373
374
Acknowledgements: 375
Authors acknowledge the laboratory facilities provided by National Institute of Pharmaceutical 376
Education & Research, Mohali Chandigarh and University of Kashmir, Hazratbal Srinagar. 377
378
379
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Captions: Table 1: Treatments for modification of starch with ionic gums and dry heating Table 2: Compositional analysis of native and modified water chestnut starch Table 3: Physicochemical properties of native and modified water chestnut starch Table 4: Pasting parameters of investigated starch samples Table 5: Thermal parameters of investigated starch samples
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Table 1
Table 2
Means in the same rows with same small letter superscripts do not differ significantly (p≤0.05) (n=3)
Sample Starch (g)
Treatments
CMC (g/100g)
Sodium Alginate (g/100g)
Heating Temperature
(˚C )
Heating Duration (h)
B0 50 - - - -
B2 50 - - 130 2
B4 50 - - 130 4
C0 39.6 1 - - -
C2 39.6 1 - 130 2
C4 39.6 1 - 130 4
S0 39.6 - 1 - -
S2 39.6 - 1 130 2
S4 39.6 - 1 130 4
Parameter (g/100g)
B0 B2 B4 C0 C2 C4 S0 S2 S4
Moisture 9.12e 4.71d 4.60c 9.81g 4.31b 4.24 b 9.67f 4.69c 3.77a
Ash 0.34a 0.36a 0.35a 0.69b 0.68b 0.69b 0.74c 0.73c 0.73c
Total
Carbohydrates
70.1a 74.56c 74.14b 75.45f 74.91e 74.66d 76.12g 76.56h 75.45f
Amylose 28.77g 28.81h 29.69i 26.78e 27.37f 24.43a 26.56d 25.6c 24.77b
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Table 3
Means in the same rows with same small letter superscripts do not differ significantly (p≤0.05) (n=3)
Table 4
Sample PV (cP)
TV (cP) BV (cP)
FV (cP)
SV (cP)
Peak Time (min)
Pasting Temp (˚C)
B0 3402b 1423b 1980b 4171a 2748a 4.67b 81.7d
B2 3867d 1489d 2429d 4388b 2988b 4.61b 81.21c
B4 4327h 1529f 2798g 4952e 3423e 4.6b 81.8 d
C0 3286a 1384a 1902a 4564d 3180d 4.87c 81.65d
C2 4317g 1442c 2875h 5264h 3822i 4.6b 79.75a
C4 3950e 1647g 2303i 5214f 3567f 4.93c 80b
S0 3569c 1527f 2042c 4518c 2991c 4.8b 81.5d
S2 4299f 1513e 2786f 5251g 3738g 4.6b 80b
S4 4404i 1662h 2742e 5440i 3778h 4.47a 79.95a
Means in the same columns with same small letter superscripts do not differ significantly (p≤0.05) (n=2)
PV= Peak Viscosity, TV= Trough Viscosity, BV= Breakdown Viscosity, FV= Final Viscosity, SV= Set Back Viscosity
Parameter Bo B2 B4 C0 C2 C4 S0 S2 S4
Solubility (g/100g)
19.5 d 19.6 d 18.2c 20e 19.4d 18.8c 17.6b 17.2b 16.5a
Swelling power (g/g)
8.67i 7.78h 7.39e 7.53g 7.45f 7.22d 7.13c 6.97b 6.26a
Water binding capacity (g/g)
106a 120.2b 134d 122.2c 122c 138.1f 136.1e 148.2g 151.1h
Oil binding capacity (g/g)
122.3a 150.2c 153.4e 140.1b 154.3f 151.1d 157.1g 163.2h 167.1i
Paste clarity (% light
transmittance)
6.9c 5.8a 6.4c 5.1a 4.9b 4.6b 6.3c 6.8c 5.4a
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Table 5
Sample To (˚C) Tp (˚C) Te (˚C) ∆H(J/g)
B0 70.53d 79.64d 84.65a 12.9b
B2 31.51a 79.16c 84.33a 11.3a
B4 69.46c 78.54b 85.2d 17.3c
C0 70.82d 79.76e 85.56d 32.6g
C2 65.46b 79.75e 85.98e 27.1e
C4 31.26a 78.06a 84.3a 29.9f
S0 71.09e 79.87f 85.35b 20.7d
S2 71.63f 79.12 c 84.95c 16.9c
S4 72.69f 79.13c 84.41b 20d
Means in the same columns with same small letter superscripts do not differ significantly (p≤0.05) (n=3) T0: Onset gelatinization temperature; Tp: Peak gelatinization temperature; Te: End point temperature, ∆H: Enthalpy
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Captions
Figure 1: Effect of modification on swelling power (g/g) of investigated water chestnuts starches (B CMC SA )
Figure 2: Effect of modification on solubility (g/100g) of investigated water chestnuts starches (B CMC SA )
Figure 3: Effect of modification on paste clarity (% transmittance) of investigated water chestnuts starches (B CMC SA )
Figure 4: Effect of modification on water binding capacity (g/g) of investigated water chestnuts starches (B CMC SA )
Figure 5: Effect of modification on oil binding capacity (g/g) of investigated water chestnuts starches (B CMC SA )
Figure 6: Scanning Electron Micrographs of investigated starches
(A) Native starch sample (B) Starch Sample modified with 2 h heating (C) Starch Sample modified with 4 h heating (D) Starch Sample modified with Carboxy methyl cellulose (E) Starch Sample modified with CMC & 2 h heating (F) Starch Sample modified with CMC & 4 h heating (G) Starch Sample modified with Sodium alginate Only (H) Starch Sample modified with Sodium alginate & 2 h heating (I) Starch Sample modified with Sodium alginate & 4 h heating
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Figure 1
Figure 2
Figure 3
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0 2 4
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Figure 5
0
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g C
ap
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Time (h)
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Bin
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g C
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Figure 6
C
B A
F
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HG
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Highlights
• Water chestnut starch was modified with ionic gums (CMC & SA) and dry heating. • Physicochemical, pasting, thermal and morphological properties were studied. • Paste clarity, solubility and swelling power decreased. • Water and oil binding capacity increased. • SEM showed surface cracking and agglomeration of starch granules.
