Journal of Food Measurement and Characterization (2021) 15:2805–2820

https://doi.org/10.1007/s11694-021-00862-5

ORIGINAL PAPER

Physicochemical, morphological, functional, and pasting properties

of potato starch as a function of extraction methods
Neeraj1 · Saleem Siddiqui1 · Nidhi Dalal1 · Anuradha Srivastva2 · Ashok Kumar Pathera3

Received: 11 August 2019 / Accepted: 23 February 2021 / Published online: 11 March 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021

Abstract
The potato starch extracted by physical, chemical, and enzymatic methods were analyzed for physicochemical, morphologi-
cal, functional, and pasting properties. In the physical extraction methods, T
­ 1 (water at 30 °C) was found better in starch
yield, water absorption capacity (WAC), and whiteness. In the chemical extraction methods, starch from ­T5 (NaOH-0.25%)
had higher WAC, and lower ash content. The starch from T ­ 7 (SDS-ME-2%) had higher amylose, starch purity, and lower
amylopectin, moisture, fat content. The starch from T­ 11 (NaOCl-5.25%) had higher starch whiteness value. In the enzymatic
extraction methods, starch from ­T13 (cellulase-0.15%) had higher starch yield. Further, the physical ­(T1), chemical ­(T5, ­T7
and ­T11) and enzymatic (­ T13) methods were used in combination and had shown the better physicochemical and morphologi-
cal characteristics of starch. The starch from combined method ­(T14) had significantly higher yield (12.4%), WAC (259%),
swelling power (40.3%), solubility (23.6%), purity (87.3%), and whiteness (95.2%). The starch from combined method also
had significantly lower phosphorus (81.7%), protein (0.30%), fat (0.29%), ash (0.26%), crude fiber (0.15%) content, and
syneresis (18.8%). The starch from combined method had resulted in the better starch granule structure, pasting properties
than most of the other treatments. So, the physical, chemical, and enzymatic treatments in combination can be used for
extraction of high-quality starch from potato.

Keywords Potato starch · Extraction methods · Functional properties · Pasting properties

Introduction amylose and amylopectin chain, phosphate ester groups on

amylopectin, ability to form a thick viscoelastic gel upon
Starch is a polysaccharide found in grains, tubers, roots, heating and subsequent cooling in water, and poor thermal
and unripe fruits. Being abundant, cheap, biodegradable, and shear stability of this gel make it unique compared to
renewable, and generally recognized as safe, starch is of par- cereal starches [2]. Although potato starch has good textural,
ticular interest for food and industrial applications. Starch stabilizing properties in food systems but has limitations like
has been widely used as a thickener, colloidal stabilizer, low shear and thermal resistance, thermal decomposition,
gelling agent, bulking agent, and water retention agent and poor freeze–thaw stability, very cohesive gel texture and the
has been broadly used in brewing industries [1]. Potato high tendency of retrogradation which limit its industrial use
consists of 70 to 80% water and 16 to 24% starch. Potato in food applications.
starch characteristics like purity, larger granule size, long The process of starch extraction consists of lysing the
plant cell to release the starch stored in the amyloplast
stroma and then removing impurities such as proteins, lipids,
* Ashok Kumar Pathera
apathera@gmail.com and minerals. Methods of starch extraction are broadly cate-
gorized into physical, chemical, enzymatic and may combine
1
Centre of Food Science and Technology, CCS Haryana more than one category. Extraction procedures affect the
Agricultural University, Hisar, Haryana 125004, India chemical and physical properties of starch [3]. The cooking,
2
ICAR- Directorate of Mushroom Research, Himachal textural and rheological properties of starch are related to its
Pradesh, Chambaghat, Solan 173213, India physicochemical, morphological, and functional properties
3
School of Bioengineering and Food Technology, Shoolini [4].
University of Biotechnology and Management Sciences,
Solan, Himachal Pradesh 173229, India

13
Vol.:(0123456789)
2806 Neeraj et al.

To overcome the inherent deficiencies of native starches, niger) and protease (from Bacillus licheniformis) were pro-
different treatments were carried out to meet the industrial cured from Sigma-Aldrich Chemicals Pvt Ltd.
requirement to find out a profitable method of starch extrac-
tion. Sandhu et al. [5] observed that NaOCl treated waxy Physical methods of extraction
starch had significantly higher peak (PV), trough (TV),
breakdown (BV), final (FV) and setback viscosity (SV), light Extraction using water at 30 °C
transmittance. Alkali-treated sago (Metroxylon sagu) starch
had significantly higher swelling power and water solubility The method described by Peshin [15] with some modifica-
[6]. The alkali-treated corn starches exhibited lower past- tions was used for starch extraction. Potatoes were peeled,
ing temperatures, higher peak viscosity than the wet-milled diced, and ground in a blender (Sujata, J.K. Electricals Pvt.
starch. The higher alkali concentration in starch isolation Ltd., Noida, India) for 3–4 min with 1 L of distilled water at
resulted in stronger gel formation than the starch isolated 30 °C temperature. The resulting slurry was filtered through
at lower alkali concentration [7]. With sodium dodecylsul- a piece of muslin cloth. The residue left on the muslin was
fate (SDS) treatment amylose content, swelling power and washed repeatedly with distilled water until the filtrate began
peak viscosity were significantly increased, peak time and to yield only small quantities of starch. All the filtrate was
peak temperature decreased for waxy starches [8]. Vasanthan collected in a glass beaker and the residue left on the mus-
and Hoover [9] reported that swelling factor and amylose lin was discarded. The suspension in the beaker was stood
leaching of defatted starches increased on defatting with undisturbed for 2 h, by which time a solid layer of starch
solvent mixture n-propanol/water (3:1 v/v); thermal stabil- had settled to the bottom of the beaker as sediment. This
ity increased, hot paste consistency and pasting temperature sediment was washed 3–4 times with distilled water and
decreased [10]. The 1% bisulphite treated potato starch had then sieved through a 120-mesh sieve until the wash water
an acidic pH, higher number of short chains in the amy- was clear and free of any suspended impurities. The pure
lopectin molecules and had a lower peak viscosity as well starch thus extracted was dried overnight in an oven (NSW-
as general pasting [11]. Freeze–thaw stability, pasting tem- 143, Narang Scientific Works Pvt. Ltd., New Delhi, India)
perature, paste clarity and swelling of the starch granules at 40 ± 5 °C, ground, and sieved through a 150-mesh screen.
increased, whereas solubility and viscosity decreased and no
damage to starch granule surface with the enzymatic method Extraction using hot water (60 °C)
of starch extraction using protease enzyme [12]. Correia
et al. [13] observed that protease treated chestnut starches Starch was extracted by using the method described by
had high amylose and resistant starch contents and produced Singh and Singh [16] with some modifications. Potatoes
strong, elastic, and stable gels. It also had lower consistency were peeled, diced, and dipped in hot water (60 °C) for
values and gelling ability, whereas setback values and tur- 10 min and then ground in a blender to get a fine slurry.
bidity were higher. The slurry was filtered through a muslin cloth and washed
Although much research has been carried out on the repeatedly as described above. The filtrate was collected in a
characterization of physicochemical properties of potato glass beaker and the suspension was stood undisturbed until
starch [10, 14] but very few information is available about the supernatant became clear. The supernatant was decanted,
comparative analysis of various extraction methods, their and the layer of starch that had settled to the bottom was
merits, and drawbacks. Therefore, this study was designed to suspended once again in fresh distilled water. This process
investigate the effect of different extraction methods on the was repeated 4–5 times until the supernatant became fully
physicochemical, morphological, and functional properties transparent. The starch was dried overnight in an oven at
of potato starch. 40 ± 5 °C, cooled to room temperature, ground, and sieved
through a 150-mesh screen.

Materials and methods Extraction using cold water (10 °C)

Materials Starch was extracted, with some modifications, by the

method described by Collado and Corke [17]. Potatoes were
The fresh potato tubers of Kufri Bahar harvested from Veg- washed, brushed, peeled, pitted, and grated. To the grated
etable Farm, CCS Haryana Agricultural University, Hisar mass was added 5 L of cold (10 °C) water and the mix was
were used for extraction of starch by various methods. All left to stand, with occasional stirring, for 1 h. The mix was
chemicals were procured from Sigma-Aldrich Chemicals macerated in a blender for 2 min at medium speed and fil-
Pvt. Ltd. New Delhi, India, and Central Drug House (P) Ltd., tered through a muslin cloth. The filtrate was put through a
New Delhi, India. The enzymes cellulase (from Aspergillus blender once again, mixed with water, and passed through

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2807

a 250-mesh sieve. The starch in the filtrate was settled for piece of muslin. The filtrate stood undisturbed for 2–3 h,
2–3 h at room temperature. The supernatant was decanted after which the supernatant was decanted off. The starch
and discarded, the starch resuspended in water, filtered sediment was washed twice with distilled water, suspended
through a 250-mesh sieve, and allowed to settle yet again at in 100 mL of hot solvent (n-propanol:water, 3:1 v/v), the
room temperature. The last step was repeated once without suspension stirred for 30 min using a magnetic stirrer, cen-
the sieving. The sediment was dried overnight in an oven at trifuged at 252 g for 10 min, and the supernatant carefully
40 ± 5 °C, cooled to room temperature, ground, and sieved removed. The pellet was washed three times, resuspended in
through a 150-mesh screen. distilled water, centrifuged, and dried in an oven at 40 ± 5 °C
for 12 h. The dried starch was sieved through a 150-mesh
Chemical methods of extraction screen.

Removing proteins using sodium hydroxide Extraction using sodium bisulfite as a bleaching agent

Starch was extracted by the method described by Muazu Starch was extracted by using, with some modifications,
et al. [18] with some modifications. Potatoes were washed the method described by Abegunde et al. [20]. Potatoes
in tap water and chopped into thin slices. Then, separately were washed, chopped, and soaked in a solution of sodium
soaked in 0.1% (­ T4 treatment) and 0.25% (­ T5 treatment) bisulfite, in a 0.1% (w/v) solution for 10 min in T
­ 9 treatment
sodium hydroxide solution for 10 min and macerated with and in a 1.7% (w/v) solution for 5 min in ­T10 treatment.
added distilled water in a blender. The slurry was filtered The mass was then mixed for 3–4 min and the resulting
through a piece of muslin and the residue was washed slurry was passed through a piece of fine muslin, sieved
repeatedly to recover the maximum amount of starch. The three times through a 150-mesh sieve, and allowed to settle
filtrate was collected in a tub, left undisturbed for 2–5 h, the 2 h at room temperature. The residue left on the muslin cloth
supernatant decanted off, and the starch sediment washed was washed repeatedly with distilled water until the filtrate
repeatedly (4–5 times) with distilled water until the superna- began to yield only small quantities of starch. The filtrate
tant was fully transparent. The starch was dried in an oven at was then collected in a glass beaker and kept undisturbed
40 ± 5 °C until dry, ground, and sieved through a 150-mesh for 2 h. The supernatant was decanted off, the starch sedi-
screen. ment resuspended in distilled water, and the starch allowed
to settle again. This process was repeated 4–5 times until
Removing lipids using a mix of sodium dodecylsulfate the supernatant was fully transparent. The collected starch
(SDS) and mercaptoethanol (ME) was dried in an oven at 40 ± 5 °C for 24 h, ground fine, and
sieved through a 150-mesh screen.
Starch was extracted according to the method described
by Chan et al. [19] with some modifications. Potatoes Extraction using sodium hypochlorite as a bleaching agent
were washed, chopped, macerated in a blender, and sieved
through a piece of muslin. The filtrate was left to stand for Starch was extracted using, with some modifications, the
2–5 h, after which the supernatant was decanted off, the method described by Sira and Amaiz [21]. Potatoes were
starch sediment washed twice with distilled water and sus- washed, chopped, and macerated. The mass was then soaked
pended in 100 mL of SDS-ME solvent (1% in ­T6 treatment in a 5.25% solution (v/v) of sodium hypochlorite solution for
and 2% in ­T7 treatment) at room temperature. The suspen- 7 min to avoid browning, the slurry was filtered through a
sion was stirred for 30 min using a magnetic stirrer (Remi piece of muslin, and washed with distilled water. The residue
2-MLH, Remi Elektrotechnik Ltd., Thane, India), centri- of starch was washed four times and allowed to settle for
fuged (MP 400 R, Elektrocraft (India) Pvt. Ltd., Thane, 2 h. The starch sediment was dried overnight in an oven at
India) at 252 g for 10 min, and the supernatant was carefully 40 ± 5 °C, ground, and sieved through a 150-mesh screen.
removed. The pellet was washed three times, resuspended in
distilled water, centrifuged, and dried in an oven at 40 ± 5 °C Enzymatic methods of extraction
for 12 h. The dried starch was ground and sieved through a
150-mesh screen. Extraction using neutral protease

Removing lipids using a mix of n‑propanol and water Starch was extracted using protease, with some modifica-
tions, the method described by Wang and Wang [22]. Pota-
Starch was extracted by using, with some modifications, the toes were washed, cut into small pieces without peeling,
method described by Vasanthan and Hoover [9]. Potatoes mixed with 200 mL of distilled water, and stored at 50 °C
were washed, chopped, macerated, and sieved through a in a circulator after adjusting the pH of the slurry to 7.0

13
2808 Neeraj et al.

with 1.0 M NaOH. Then 10 mL of neutral protease solution distilled water and the starch allowed to settle yet again. This
(0.01%) was added to the mixture. The mixture was kept for process was repeated 4–5 times until the supernatant became
5 h with constant stirring at 150 rpm in a water bath. After fully transparent. The starch slurry was then suspended in
this process of digestion with protease, the slurry was mac- 100 mL of SDS-ME solvent (2% w/v) at room temperature,
erated in a blender, sieved through a 120-mesh screen, and stirred for 30 min using a magnetic stirrer, and centrifuged at
centrifuged at 219 g for 10 min. The pellet was washed three 252 g for 10 min. The pellet was washed three times, resus-
times with distilled water. The starch was dried in an oven pended in distilled water, centrifuged, and dried in an oven
at 40 ± 5 °C for 48 h and sieved through a 150-mesh screen. at 40 ± 5 °C for 12 h. The dried starch was sieved through a
150-mesh screen.
Extraction using cellulase The extracted starch irrespective of methods was oven-
dried at 40 ± 5 °C for 12 h. Dry starch was sieved through a
Starch was extracted using, with some modifications, the 150-mesh screen, weighed, packed in LDPE bags then stored
method described by Kallabinski and Balagopalan [23]. at room temperature for further use.
The procedure was the same as that described in extraction
using neutral protease except that the enzyme solution was
Physicochemical properties
prepared by mixing 1.5 g of cellulase in 10 mL of distilled
water so that the final strength of enzyme was 0.15%. The
Starches were analyzed for moisture, fat, crude protein, ash
mixture was kept for 4.5 h at 45 °C with constant stirring at
and crude fiber content following the AOAC [24] methods.
125 rpm. After incubation, the slurry was sieved through a
Crude starch content also represented starch yield (%). The
250-mesh and the filtrate collected into a plastic container.
starch purity (%) was calculated by using the following
The residue was washed twice with distilled water. The fil-
formula:
trate was kept undisturbed for 1 h and the sediment was
centrifuged at 219 g for 10 min. The brown layer at the top
[ ]
Purity(%) = 100 − (Moisture + fat + crude protein + ash + crude fiber)
of the pellet was removed by scraping and the remaining
starch washed with water and centrifuged again. The lower The amylose content was determined using the method
starch layer was re-suspended in water and the suspension described by Williams et al. [25]. The amylopectin content
washed with distilled water three times. The final residue of was determined by subtracting amylose content from 100.
starch was dried in an oven at 40 ± 5 °C for 24 h, ground, The whiteness value was determined by using the method
and sieved through a 150-mesh screen. of Thao and Noomhorm [26]. The color of starches in terms
of L* (whiteness or blackness), a* (redness or greenness)
Extraction using a combination of physical, and b* (yellowness or blueness) values were measured by
chemical, and enzymatic methods color measurement instrument (Color Flex, Hunter Associ-
ates Laboratory, Inc., Reston, USA). The whiteness value
The best of the above methods evaluated based on yield, was obtained by the following equation
purity, WAC, and light transmittance, swelling power, ]1∕2
Whiteness = 100 − (100 − L)2 + a2 + b2
[
lower phosphorus content and lower syneresis of starch,
were selected. The combination thus comprised 30 °C Total phosphorus content was determined by vanadomo-
temperature, 0.25% of NaOH, 2% w/v mix of SDS-ME, lybdophosphoric yellow color method [27]. Total phospho-
sodium hypochlorite, and cellulase. Potatoes were washed, rus content (%) in sample = A × 0.05 (Where A = absorbance
brushed, pitted, chopped into 4 ­cm2 pieces, and soaked in of the sample at 440 nm).
0.25% sodium hydroxide solution for 10 min. Pieces with
dark spots were discarded and the rest were macerated in
a blender. The enzyme solution (10 mL) was added to the Morphological properties
mix to make the final strength at 0.15%, and the slurry was
diluted by adding 200 mL of water. The suspension was The shape and size of starch particles were taken by an
incubated at 45 °C with constant stirring at 125 rpm for upright microscope (CX41, Olympus Corporation, Tokyo,
4.5 h. After the incubation, the mix was exposed to 5.25% Japan) equipped with a digital camera facility at × 10 power
sodium hypochlorite solution for 7 min to avoid browning lens. The particle size was measured using a diluted crystal
and then filtered through a 120-mesh sieve. The residue was violet dye (1% aqueous solution). Narrow pointed spatula or
washed repeatedly with distilled water until the filtrate began dissecting needle was used to transfer 1 mg of starch sam-
to yield only small quantities of starch. The filtrate was col- ple on to the crystal violet dye. This was mixed thoroughly
lected in a glass beaker and allowed to stand undisturbed for to disperse the starch in the dye solution. A coverslip was
2–3 h. The sediment of the starch layer was re-suspended in placed over the suspension and observed under a compound

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2809

microscope fitted with a digital camera. The photograph of India). The per cent water separated after each freeze–thaw
each slide was taken. The same slide was further observed cycle was measured in terms of syneresis.
for size using a calibrated ocular scale fitted on the lens. The
particles were divided into two groups based on the size. Pasting properties
The particles having size lesser than 30 µm were grouped
as small size particles and particles having size more than The pasting properties of the starch were determined by
30 µm were grouped as large size particles. The percent- using the Rapid Visco Analyzer (Perten Instruments, Häger-
age of small and large size particles was calculated for the sten, Sweden). In a canister, 2.25 g of the starch sample
starch of each treatment. The particle shape was subse- (14% moisture) was mixed with 25 mL of distilled water for
quently observed from the photograph using the standard analysis. A paddle was placed into the canister and jogged
shape chart. to ensure uniform distribution of starch particles. The pad-
dle and the canister were placed into the analyzer. A pro-
Functional properties grammed heating and cooling cycle was used at a constant
shear rate and consisted of holding the sample at 50 °C for
WAC of starch was determined using the method of Beuchat 1 min, heating it to 95 °C in 7.5 min, holding at 95 °C for
[28] with slight modification. One gram of starch sample 5.5 min, cooling to 50 °C in 7.5 min, and then holding it at
was mixed with 50 mL of water in a centrifuge tube. The 50 °C for 5 min. Each test was replicated three times. Peak
mixture was shaken in incubator cum shaker at temperature viscosity, time to reach peak viscosity ­(Ptime), temperature at
(30 ± 2 °C) for 1 h and centrifuged at 1006 g for 10 min. peak viscosity ­(Ptemp), hot-paste viscosity (viscosity after the
The volume of water on the sediment was measured and holding time at 95 °C), and cool-paste viscosity (viscosity at
was decanted. The weight of wet starch paste (sediment) the end of the holding time at 50 °C) was recorded. Peak vis-
was taken, and the water absorbed by starch was expressed cosity, trough viscosity, breakdown viscosity, final viscosity,
as g/g water absorption based on the original sample weight. setback viscosity, peak time, and pasting temperature were
The swelling power and solubility of potato starch were recorded from the thermocline windows.
measured as described by Waliszewski et al. [29] with slight
modification. Starch sample (1 g) was mixed in 50 mL of Statistical analysis
distilled water and the obtained slurry was heated for 30 min
at 90 °C temperature with constant stirring. The mixture The web-based agricultural statistics software package
was cooled and centrifuged at 1006 g for 15 min. The resi- (WASP 2.0) developed by ICAR Central Coastal Agricul-
due obtained after centrifugation in the centrifuged tube tural Research Institute, Goa was used for statistical analysis
was weighed. Aliquots of the supernatant were dried into of variance (ANOVA). The experiment was set up under
an evaporating dish of known weight to a constant weight at a completely randomized design with three replications.
110 °C. The supernatant represented the amount of starch Means were separated by critical difference (CD) at the 5%
solubilized in water. level of significance.

Weight of wet sediment paste (g)

Swelling power (g∕g) =
Weight of dry starch (g) Results and discussion

Weight of dried supernatant (g) Physicochemical properties

Solubility (%) = × 100
Weight of dry starch (g)
The physicochemical properties of the potato starches are
The light transmittance of starch paste from potato starch presented in Tables 1, 2 and 3; Figs. 1 and 2. The lowest
was measured by Craig et al. [30] method with slight modifi- moisture content (10.9%) was found in starch from treatment
cation. The prepared samples were stored for 5 days at 4 °C ­T7 (SDS-ME- 2%) and the highest moisture content (14.8%)
in a refrigerator and transmittance was determined every was observed in starch from treatment ­T12 (Protease). The
24 h with a VIS spectrophotometer at 640 nm (LT-39, Lab- combined treatment (­ T14) had 11.7% moisture content in
tronics, Panchkula, India). starch. The difference in moisture content due to the differ-
The freeze–thaw stability (syneresis) of potato starch was ent method used and extent of drying and humidity in the
measured using the method of Kaur et al. [31] with slight surrounding atmosphere. Same results were also reported
modifications. The prepared starch samples were subjected in potato starch [4]. Similarly, Yusuf et al. [32] observed
to five freeze–thaw cycles (frozen at − 18 °C) in a deep that native Jack bean starches have more moisture, protein,
freezer (Blue Star Engineering & Electronics Ltd., Mumbai, fat and ash contents than chemically treated starches. Pro-
tein was varying from 0.30 to 0.77%. Lower protein content

13
2810 Neeraj et al.

Table 1  Effect of extraction methods on moisture, protein, fat, ash, and crude fiber of potato starch
Treatments Moisture (%) Protein Fat Ash Crude fiber (%)
(%) (%) (%)

Physical treatments
­T1 Control (Water-30 °C) 13.5 ± 0.27b 0.70 ± 0.08ab 0.56 ± 0.04bcde 0.42 ± 0.03bc 0.28 ± 0.03abc
­T2 Cold Water-10 °C 12.6 ± 0.25cd 0.77 ± 0.05a 0.68 ± 0.04a 0.40 ± 0.03bc 0.25 ± 0.04bcde
­T3 Hot Water-60 °C 14.7 ± 0.30a 0.67 ± 0.03bc 0.61 ± 0.08ab 0.44 ± 0.06ab 0.22 ± 0.05cde
Chemical treatments
­T4 NaOH-0.1% 11.4 ± 0.19fg 0.47 ± 0.06d 0.47 ± 0.09fg 0.21 ± 0.04hi 0.20 ± 0.03ef
­T5 NaOH-0.25% 11.3 ± 0.12g 0.37 ± 0.02ef 0.45 ± 0.06fg 0.20 ± 0.03i 0.19 ± 0.03ef
­T6 SDS-ME-1% 12.8 ± 0.20c 0.41 ± 0.06de 0.31 ± 0.03hi 0.34 ± 0.04de 0.24 ± 0.03bcde
­T7 SDS-ME-2% 10.9 ± 0.15h 0.38 ± 0.06ef 0.28 ± 0.01i 0.30 ± 0.02efg 0.21 ± 0.03de
­T8 Propanol-water 12.4 ± 0.21de 0.64 ± 0.04bc 0.39 ± 0.02gh 0.48 ± 0.03a 0.26 ± 0.01bcd
­T9 Na-bisulphite-0.1% 12.2 ± 0.09e 0.69 ± 0.07ab 0.52 ± 0.05cdef 0.42 ± 0.04bc 0.33 ± 0.04a
­T10 Na-bisulphite-1.7% 13.3 ± 0.08b 0.61 ± 0.06bc 0.49 ± 0.03def 0.40 ± 0.02bc 0.29 ± 0.05ab
­T11 Na-hypochlorite 11.4 ± 0.26fg 0.59 ± 0.04c 0.47 ± 0.07ef 0.28 ± 0.04fg 0.25 ± 0.04bcde
Enzymatic treatments
­T12 Protease 14.8 ± 0.17a 0.39 ± 0.06de 0.57 ± 0.06bcd 0.38 ± 0.04cd 0.33 ± 0.05a
­T13 Cellulase 12.8 ± 0.16c 0.64 ± 0.07bc 0.59 ± 0.05bc 0.33 ± 0.03def 0.22 ± 0.03cde
Combined treatment
­T14 Combined treatment 11.7 ± 0.23f 0.30 ± 0.03f 0.29 ± 0.02i 0.26 ± 0.02gh 0.15 ± 0.02f
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.339 0.092 0.086 0.057 0.061

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5% level of significance when compared
with Fisher’s Least Significant Difference are followed by the same superscript letters

Table 2  Effect of extraction methods on amylose, amylopectin, phosphorus, and water absorption capacity (WAC) of potato starch
Treatments Amylose Amylopectin (%) Phosphorus (mg/100 g) WAC​
(%) (%)

Water treatments
­T1 Control (Water-30 °C) 21.9 ± 0.19c 78.1 ± 0.19i 113.1 ± 0.39a 226 ± 0.37i
­T2 Cold Water-10 °C 16.3 ± 0.17i 83.7 ± 0.17c 106.3 ± 0.49c 222 ± 0.74j
­T3 Hot Water-60 °C 19.1 ± 0.14f 80.9 ± 0.14f 86.1 ± 0.15h 205 ± 0.82m
Chemical treatments
­T4 NaOH-0.1% 21.4 ± 0.25d 78.6 ± 0.25h 105.6 ± 0.58c 241 ± 1.06f
­T5 NaOH-0.25% 20.3 ± 0.34e 79.7 ± 0.34g 97.9 ± 0.17e 281 ± 1.23a
­T6 SDS-ME-1% 22.8 ± 0.33b 77.2 ± 0.33j 73.6 ± 0.25k 235 ± 0.57g
­T7 SDS-ME-2% 24.1 ± 0.28a 75.9 ± 0.28k 70.1 ± 0.32l 275 ± 0.46b
­T8 Propanol-water 17.6 ± 0.38h 82.4 ± 0.38d 109.9 ± 0.42b 213 ± 1.08l
­T9 Na-bisulphite-0.1% 14.1 ± 0.24j 85.9 ± 0.24b 87.5 ± 0.20g 218 ± 0.93k
­T10 Na-bisulphite-1.7% 11.4 ± 0.10k 88.6 ± 0.10a 90.9 ± 0.34f 199 ± 0.70n
­T11 Na-hypochlorite 18.3 ± 0.11g 81.7 ± 0.11e 63.2 ± 0.29m 261 ± 0.89c
Enzymatic treatments
­T12 Protease 19.3 ± 0.37f 80.7 ± 0.37f 99.1 ± 0.45d 231 ± 1.01h
­T13 Cellulase 19.5 ± 0.35f 80.5 ± 0.35f 84.2 ± 0.39i 244 ± 0.48e
Combined treatment
­T14 Combined treatment 20.9 ± 0.62d 79.1 ± 0.62h 81.7 ± 0.37j 259 ± 0.43d
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.51 0.51 0.60 1.3

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5% level of significance when compared
with Fisher’s Least Significant Difference are followed by the same superscript letters

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2811

Table 3  Effect of extraction Treatments Color values

methods on color values of
potato starch L*(D65) a*(D65) b*(D65) Whiteness

Water treatments
­T1 Control (Water-30 °C) 92.9 ± 0.33e 0.48 ± 0.03de 4.09 ± 0.21ef 91.8 ± 0.23fg
­T2 Cold Water-10 °C 92.7 ± 0.42e 0.51 ± 0.02d 4.23 ± 0.16de 91.5 ± 0.18g
­T3 Hot Water-60 °C 90.5 ± 0.37gh 0.75 ± 0.06c 5.08 ± 0.23b 89.2 ± 0.13ij
Chemical treatments
­T4 NaOH-0.1% 91.7 ± 0.20f 0.68 ± 0.04c 3.92 ± 0.13fg 90.8 ± 0.20h
­T5 NaOH-0.25% 90.9 ± 0.30g 0.86 ± 0.09b 5.23 ± 0.15ab 89.5 ± 0..31i
­T6 SDS-ME-1% 95.5 ± 0.32c 0.45 ± 0.04def 4.48 ± 0.17cd 94.2 ± 0.16d
­T7 SDS-ME-2% 95.6 ± 0.35c 0.41 ± 0.04efg 4.41 ± 0.19cd 94.2 ± 0.34d
­T8 Propanol-water 90.4 ± 0.31 h 1.34 ± 0.07a 5.42 ± 0.11a 88.9 ± 0.31i
­T9 Na-bisulphite-0.1% 96.8 ± 0.21ab 0.41 ± 0.08efg 3.74 ± 0.18gh 94.5 ± 0.21cd
­T10 Na-bisulphite-1.7% 96.9 ± 0.24ab 0.38 ± 0.06 fg 3.71 ± 0.16gh 94.6 ± 0.24c
­T11 Na-hypochlorite 97.3 ± 0.35a 0.29 ± 0.03h 3.37 ± 0.15i 95.7 ± 0.17a
Enzymatic treatments
­T12 Protease 93.8 ± 0.16d 0.46 ± 0.03def 5.05 ± 0.20b 92.0 ± 0.15f
­T13 Cellulase 94.2 ± 0.14d 0.48 ± 0.06de 4.52 ± 0.14c 92.7 ± 0.14e
Combined treatment
­T14 Combined treatment 96.8 ± 0.18b 0.35 ± 0.03gh 3.58 ± 0.12hi 95.2 ± 0.26b
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.48 0.087 0.281 0.37

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5%
level of significance when compared with Fisher’s Least Significant Difference are followed by the same
superscript letters

Fig. 1  Effect of extraction methods on yield of potato starch. Data represent the mean ± standard deviation. Means that did not differ signifi-
cantly at 5% level of significance when compared with Fisher’s Least Significant Difference are followed by the same superscript letters

13
2812 Neeraj et al.

Fig. 2  Effect of extraction methods on purity of potato starch. Data represent the mean ± standard deviation. Means that did not differ signifi-
cantly at 5% level of significance when compared with Fisher’s Least Significant Difference are followed by the same superscript letters

(0.30%) was observed in starch from combined treatment sago starch) without damaging the starch molecular struc-
­(T14) and higher protein content (0.77%) was found in starch tures without prominent fissures or pores. Ash content in
from cold water ­(T2) treatment. Since NaOH is considered starch was varying from 0.20 to 0.48%. Treatments contain-
as a good solvent and it can solubilize the major protein ing alkali (NaOH) resulted in lower ash content in starch.
encapsulating the starch, therefore alkaline steeping method Lower ash content (0.20%) was observed in starch from ­T5
soften the protein–starch matrix and produced a starch that (NaOH-0.25%) followed by ­T4 (NaOH-0.1%), ­T14 (Com-
was low in protein and lipids [33]. The lower protein con- bined treatment) and T ­ 11 (Na-hypochlorite). The higher ash
tent in combined treatment could be due to the action of content (0.48%) was recorded in T ­ 8 (Propanol-water) treat-
alkali (soften the protein-starch matrix), SDS (removal the ment. NaOH treatment resulted in lower ash content because
surface protein of starch granules as reported by Blake et al. it caused chemical degradation of starch [34]. The lower
[8] and Chan et al. [19]) and protease (hydrolysed protein crude fiber (0.15%) was recorded in starch from combined
on starch granule surfaces as reported by Wang and Wang, treatment ­(T14) and the higher crude fiber content (0.33%)
[12] present in it). The physical method of starch extraction was found in starch from Na-bisulphite-0.1% ­(T9) treatment.
containing cold water ­(T2) treatment retained the maximum The crude fiber and ash contents of starch were significantly
protein in the potato starch because it did not remove the affected by extraction methods. A similar reduction in crude
protein of potato starch. The treatment SDS-ME-2% ­(T7) fiber content of the native starch by chemical treatments was
resulted in lower fat content (0.28%) in starch followed by reported in mucuna bean [35].
­(T14) combined treatment (0.29%). The T ­ 2 (cold water) treat- The potato starch yield (fresh weight basis) was varying
ment resulted in higher fat content (0.68%) in the potato from 10.7 to 13.5% (Fig. 1) in different extraction meth-
starch. The fat content in starch was significantly reduced by ods. In the present investigation, cellulase treatment ­(T13)
SDS treatments because it removes surface and inner lipids resulted in significantly higher starch yield (13.5%). Fur-
which makes inclusion complexes present in starch granules ther, treatment ­T10 (Na-bisulphite-1.7%) produced a lower
[19]. After exclusion of the surface lipid, the starch granule starch yield (10.7%). The combined treatment ­(T14) had
interior becomes loose which allow deeper penetration of significantly higher starch yield (12.4%) than physical ­(T1,
the extracting solvent [10]. The cold water ­(T2) treatment ­T2 and ­T3) and chemical treatments ­(T8, ­T9 and ­T10). The
resulted in higher fat in the potato starch because low-tem- starch releases after the breakdown of hemicelluloses and
perature water did not remove fat from starch granules. The celluloses. Therefore, enzymatic methods have been used to
lower fat content in starch from combined treatment could complete rupture of the cell walls and increase the recovery
be due to the action of alkali and SDS present in it. Chan of starch from roots and tubers [36]. Similar results that cel-
et al. [19] found that SDS treatment efficiently removes the lulase increased the extraction of starch have earlier been
surface protein of starch granules (potato, mung bean, and reported in cassava [36]. The effect of various methods of

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2813

extraction on the purity of starch is presented in Fig. 2. The was observed by Na-hypochlorite due to acid hydrolysis of
starch purity was varying from 83.3 to 87.9%. Maximum amylose and amylopectin chains, reducing the ash content
purity (87.9%) was observed in starch from treatment T ­7 of starch and hence its mineral content. NaOCI may have
(SDS-ME-2%) followed by treatment T ­ 5 (NaOH-0.1%) and caused oxidative degradation of amylopectin and amylose
­T14 (Combined treatment). The lower purity (83.3%) was chain and thereby reducing the phosphorus content [37].
recorded in hot water (­ T3) treatment. These results are in Similar results have also reported by Sandhu et al. [5] in
accordance with the reported findings of the present investi- corn starches. The combined treatment consisted of chemi-
gation for moisture, fat, protein and ash contents of starches cals and cellulase treatment that caused degradation in both
by various extraction methods. The starches with lower pro- amylose and amylopectin chains and hence lower phospho-
tein, fat and ash contents are considered as relatively pure rus content.
[34, 37]. The starches with minimum non-starch components The color of starch extracted from different treatments
make them suitable for some industrial applications. The was found significantly different in terms of lightness (L*),
low protein content in starch is suitable for the production of yellowness (b*) and greenness (a*) which also resulted in
syrups with high glucose content [6]. Yadav and Patki [38] significant differences in whiteness (Table 3). The light-
reported that after chemical treatment, the protein and fat ness (L*) value of starch ranged from 90.4 to 97.3. The
proportions were further reduced due to repeated washing higher lightness value was observed in starch from T ­ 11
and other process-related treatments. (Na-hypochlorite) followed by ­T10 (Na-bisulphite-1.7%),
The relative contents of amylose and amylopectin were combined treatment ­(T14) and ­T9 (Na-bisulphite-0.1%). The
significantly affected by methods of starch extraction. The lower lightness value (90.4) was observed in starch from
amylose content in the starch was in the range of 11.4 to ­T8 (Propanol-water). The greenness (a*) value of starch
24.1% (Table 2). The lower amylose content (11.4%) was ranged from 0.29 to 1.34. The lower greenness value (0.29)
found in starch from T ­ 10 (Na-bisulphite-1.7%) whereas, was observed in starch T ­ 11 (Na-hypochlorite) followed by
starch from treatment SDS-ME- 2% (­ T7) had higher amyl- combined treatment (­ T14), ­T10 (Na-bisulphite-1.7%) and ­T9
ose content (24.1%). The combined treatment ­(T14) resulted (Na-bisulphite-0.1%). The higher greenness value (1.34) was
in significantly lower amylose content (20.9%) than amyl- observed in starch from T ­ 8 (Propanol-water). The yellowness
ose content obtained in ­T1, ­T6 and ­T7. Amylopectin con- (b*) value of starch ranged from 3.37 to 5.42. The lower
tent followed just the opposite trend to that of amylose. yellowness value (3.37) was observed in starch from ­T11
The decrease in amylose by Na-bisulphite could be due to (Na-hypochlorite) followed by combined treatment (­ T14),
hydroxonium ion ­(H3O+) attacks the glycosidic oxygen atom ­T10 (Na-bisulphite-1.7%) and ­T9 (Na-bisulphite-0.1%). The
and hydrolyses the glycosidic linkage [39]. With a decrease higher yellowness value (5.42) was observed in starch from
in the concentration of Na-bisulphite, there was lesser ­T8 (Propanol-water).
degradation for hydrolysis in amylose region. Starch from The whiteness value of starch ranged from 88.9 to 95.7%
Treatment SDS-ME-2% ­(T7) had higher amylose content. (Table 3). The higher whiteness value (95.7%) was observed
The increase in amylose content can be attributed to partial in starch from ­T11 (Na-hypochlorite) followed by combined
depolymerisation of amylopectin, which in turn increased treatment ­( T 14), ­T 10 (Na-bisulphite-1.7%) and ­T 9 (Na-
the amount of linear chain. Chan et al. [19] reported lower bisulphite-0.1%). The lower whiteness value (88.9%) was
polymerization in the starch subjected to SDS:ME treat- observed in starch from ­T8 (Propanol-water). Any form of
ments. High amylose starches provide high gelling strength pigmentation on starch will negatively affect its acceptability
so, it will be suitable for the production of bakery products and that of its products [18]. A high value of lightness is
like pasta, bread and coating in fried products. desired for starches. Pre-isolation bleaching by alkali and
The phosphorus content in starch was ranging from sodium hypochlorite treatment had been reported to improve
63.2 mg/100 g to 113.1 mg/100 g (Table 2). Lower phospho- the appearance of isolated potato [18] and sorghum [21]
rus content (63.2 mg/100 g) was observed in starch from T ­ 11 starches. Sira and Amaiz [21] also observed that sodium
(Na-hypochlorite) followed by ­T7 (SDS-ME-2%), ­T6 (SDS- bisulphite and NaOCl used to bleach dark sorghum grains
ME-1%) and T ­ 14 (Combined treatment). Higher phospho- before isolation improved the whiteness of starch. Other
rus content (113.1 mg/100 g) was found in starch from ­T1 workers reported that increase in whiteness and decrease
(water-30 °C) treatment followed by ­T8 (Propanol-water), ­T2 in yellowness may be due to the washing out of residual
(cold water) and T­ 4 (NaOH- 0.1%). Phosphorus is present as starch pigments upon the acid treatment, as well as the
phosphate monoesters in potato starches [2]. The phosphate washing steps followed to neutralise the acid [40]. Sulphit-
monoesters are covalently bound to the amylopectin frac- ing improves the appearance of starch during processing by
tion of the starch [37]. The phosphorus content in potato preventing chemical reactions that cause coloration and it
starch has been reported to be influenced by the amylose/ also bleaches the colored impurities present in cell debris
amylopectin ratio [14]. The decrease in phosphorus content during starch extraction, thereby improving whiteness [20].

13
2814 Neeraj et al.

Morphological properties combined treatment ­(T14) had intact granules and smooth
surface without any crack inside granules. The maximum
It is evident from the data presented in Table 4 that dif- particle size (25.9 µm) was observed in starch from ­T7 (SDS-
ferent extraction treatments had a significant effect on the ME-2%) and minimum (18.2 µm) in starch from T ­ 9 (Na-
shape and size of potato starch granules. The shape of the bisulphite-0.1%). The relative percentages of small and large
starch granules varied from oval to spherical. There were size particles also varied to a considerable extent among the
cracks evident in starch particles extracted by ­T8 and T­ 10 starches extracted by various methods. The percentage of
treatments. The starch extracted by ­T1 treatment had intact small size particles was ranging from 35 to 56%. The higher
granules with smooth surfaces while granules of starches percentage of small size particles was observed in treatments
from ­T10 (Na-bisulphite-1.7%) and T ­ 8 (Propanol-water) ­T10 and ­T9 (Na-bisulphite), both being at par with each other.
treatment had slightly rough and pitted surfaces and cracks The percentage of large size particles was ranging from 44
was found inside the granules (Fig. 3). The starch from to 65%. The higher percentage of large size particles was

Table 4  Effect of extraction Treatments Particle size (µm) Starch particles (%) Shape
methods on size and shape of
starch particles extracted from Small Large
potato (1–30 µm) (> 30 µm)

Water treatments
­T1 Control 24.6 ± 0.52b 44 56 Oval
(Water-30 °C)
­T2 Cold Water-10 °C 19.9 ± 0.32g 43 57 Spherical
­T3 Hot Water-60 °C 21.5 ± 0.36de 44 56 Spherical
Chemical treatments
­T4 NaOH-0.1% 23.5 ± 0.62c 41 59 Spherical
­T5 NaOH-0.25% 23.0 ± 0.44c 42 58 Spherical
­T6 SDS-ME-1% 25.3 ± 0.32a 44 56 Oval
­T7 SDS-ME-2% 25.9 ± 0.26a 44 56 Spherical
­T8 Propanol-water 20.5 ± 0.14fg 35 65 Oval
­T9 Na-bisulphite-0.1% 18.2 ± 0.41h 52 48 Spherical
­T10 Na-bisulphite-1.7% 18.6 ± 0.34h 56 44 Oval
­T11 Na-hypochlorite 20.9 ± 0.20ef 47 53 Oval
Enzymatic treatments
­T12 Protease 21.9 ± 0.39d 40 60 Spherical
­T13 Cellulase 21.9 ± 0.60d 41 59 Spherical
Combined treatment
­T14 Combined treatment 23.0 ± 0.44c 44 56 Oval
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.69 7 6

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5%
level of significance when compared with Fisher’s Least Significant Difference are followed by the same
superscript letters

Fig. 3  Effect of various methods of extraction on potato starch granule

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2815

observed in starch from treatments ­T8 and ­T12, both being at plays an important role because during retorting of freez-
par with each other. It was proposed that the different alco- ing, it stabilizes them against effects such as syneresis [12].
hols cause hydrolysis of the glycosidic linkage exclusively Higher WAC in alkali-treated starch could be attributed to
inside the granule with the granule-bound water [41]. Lin ions ­(Na+) in alkali solution diffusing into the amylose rich
et al. [41] also reported that alcohol treatment caused not amorphous regions of the granules, breaking intermolecular
only the disappearance of the ‘Maltese cross’ pattern in the bonds, disrupting the crystalline structure of the starch and
centre of granule but also the occurrence of cracks inside causing the granules to absorb water to a higher degree. It
the granule. Betancur et al. [42] suggested that Na-bisul- was reported that the WAC of starch increased due to the
phite treatment resulted in acid hydrolysis, hydroxonium ion hydrogen bonds to the free hydroxyl groups of amylose and
attacking the glycosidic oxygen atom and hydrolysing the amylopectin [2, 14]. The reduction in WAC by Na-bisulphite
glycosidic linkage that resulted in changes the physicochem- treatment could be due to starch granule disintegration. The
ical properties of starch and development of some cracks on disintegrated starch molecules did not retain the water mol-
the starch surface. ecules because of the reduction of the amorphous region in
the starch granules. Kaur et al. [43] also reported that sul-
Functional properties phite caused acid hydrolysis (acid thinning) which reduced
the water-binding capacity of starch. The present results are
WAC of starches was varied from 199 to 281% under vari- in agreement with the observations reported on WAC of
ous extraction methods (Table 2). Higher WAC (281%) was Bambara groundnut starch [37].
recorded in starch from treatment ­T5 (NaOH-0.25%) fol- The swelling power of potato starch increased when the
lowed by ­T7 (SDS-ME-2%), T ­ 11 (Na-hypochlorite) and ­T14 temperature increased from 80 to 90 °C for all the treat-
(Combined treatment), whereas starch from treatment T ­ 10 ments (Table 5). The higher swelling power (44.2 g/g) was
(Na-bisulphite-1.7%) had lower WAC (199%). The differ- recorded by starch from T ­ 5 (NaOH-0.25%) treatment fol-
ences in WAC of various starches were due to the differences lowed by T ­ 7 (SDS-ME-2%), while it was lower swelling
in the degree of availability of the water binding sites in their power (26.8 g/g) in starch from ­T10 (Na-bisulphite-1.7%)
granules. In commercial starches, the water binding capacity treatment. The starch from combined treatment ­(T 14)

Table 5  Effect of extraction Treatments Swelling power (g/g) Solubility (%)

methods on swelling power and
solubility of potato starch 80 °C 90 °C 80 °C 90 °C

Water treatments
­T1 Control (Water-30 °C) 25.6 ± 0.44i 33.5 ± 0.25h 3.9 ± 0.11l 14.5 ± 0.16k
­T2 Cold Water-10 °C 23.7 ± 0.59j 32.5 ± 0.15i 3.1 ± 0.12m 12.5 ± 0.11l
­T3 Hot Water-60 °C 19.6 ± 0.14m 28.4 ± 0.34l 1.6 ± 0.10n 7.5 ± 0.09m
Chemical treatments
­T4 NaOH-0.1% 30.4 ± 0.74f 38.4 ± 0.52e 5.9 ± 0.09i 19.2 ± 0.20h
­T5 NaOH-0.25% 37.7 ± 0.51a 44.2 ± 0.50a 10.4 ± 0.13d 28.0 ± 0.32b
­T6 SDS-ME-1% 28.1 ± 0.18g 37.4 ± 0.45f 5.4 ± 0.08j 17.5 ± 0.22i
­T7 SDS-ME-2% 36.1 ± 0.27b 42.9 ± 0.64b 9.2 ± 0.16e 25.7 ± 0.25c
­T8 Propanol-water 20.9 ± 0.38l 29.3 ± 0.42k 11.2 ± 0.06c 19.8 ± 0.19g
­T9 Na-bisulphite-0.1% 23.0 ± 0.17k 30.1 ± 0.44j 12.5 ± 0.10b 21.1 ± 0.13f
­T10 Na-bisulphite-1.7% 18.5 ± 0.21n 26.8 ± 0.38 m 16.5 ± 0.07a 29.2 ± 0.06a
­T11 Na-hypochlorite 35.0 ± 0.47c 41.5 ± 0.36c 7.5 ± 0.12f 24.7 ± 0.15d
Enzymatic treatments
­T12 Protease 26.8 ± 0.26h 34.6 ± 0.32g 4.3 ± 0.15k 15.6 ± 0.12j
­T13 Cellulase 32.6 ± 0.37e 39.9 ± 0.48d 6.2 ± 0.19h 21.2 ± 0.26f
Combined treatment
­T14 Combined treatment 34.0 ± 0.30d 40.3 ± 0.30d 7.1 ± 0.05g 23.6 ± 0.18e
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.67 0.71 0.19 0.31

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5%
level of significance when compared with Fisher’s Least Significant Difference are followed by the same
superscript letters

13
2816 Neeraj et al.

resulted in significantly higher swelling power (40.3 g/g) the greater starch-chain depolymerisation and incorpora-
than other treatments except for treatments ­T5, ­T7 and ­T11. tion of the hydrophilic groups into the starch structures.
Alkali treatment is believed to remove surface protein and The extent of leaching of soluble mainly depends on the
lipids. The removal of protein and lipids during NaOH lipid content of the starch and the ability of the starch to
treatment would then open up the starch granules to more form amylose–lipid complexes, as the amylose involved in
accessibility of water [18, 33]. Also, Uthumporn et al. [6] complex formation with lipids prevented from leaching out
suggested that the presence of NaOH increases the affinity [11]. With sulphite channels present in starch granules may
of a starch granule to water, making it birefringent. As a also be responsible for aiding permeation and increase the
consequence, swelling occurs more quickly and results in potential surface area available for reaction and penetration
enlargement of granules. The starch from combined treat- hydroxonium ion (­ H3O+) attacks glycosidic O ­ 2 atom and
ment ­(T14) in the present investigation also resulted in sig- hydrolyse glycosidic linkage, therefore acid preferentially
nificantly higher swelling power due to the combined effect attacks at amorphous regions, causing increased solubility
of various chemicals present in the treatment. index of sulphite treated starches [40, 43]. The lower solubil-
The solubility of potato starch increased when the ity of starch extracted by hot water could be due to structural
temperature increased from 80 to 90 °C for all the treat- changes within the starch granules leading to either crystal-
ments (Table 5). The solubility of starches ranged from lite growth or perfection of already existing crystallite and
7.5 to 29.2% at 90 °C temperature. At 90 °C, the higher thus showing a reduction in starch solubility [35].
solubility (29.2%) was observed in starch from T ­ 10 (Na- The light transmittance of extracted potato starch with
bisulphite-1.7%) treatment followed by ­T5 (NaOH-0.25%), time trend (0, 1st, 2nd, 3rd, 4th and 5th day) showed that it
­T7 (SDS-ME-2%) and ­T11 (Na-hypochlorite) treatment at declined from 0 day to 5th day in all the treatments (Table 6).
90 °C. Lower solubility (7.5%) was recorded in starch from The changes in turbidity during storage of starch pastes were
­T3 (Hot Water). However, the starch from combined treat- consistent with rapid retrogradation of amylose [5]. This
ment ­(T14) resulted in significantly higher solubility (23.6%) decreased light transmittance can be also be attributed to
than all physical and enzymatic treatments. The increased the interaction between leached amylose and amylopectin
solubility observed after chemical treatments were due to chains, resulting in the development of function zones,

Table 6  Effect of extraction methods on light transmittance (%) of potato starch

Treatments Day
0 1st 2nd 3rd 4th 5th

Water treatments
­T1 Control (Water-30 °C) 29.6 ± 0.14j 26.6 ± 0.12j 25.8 ± 0.16h 24.2 ± 0.08g 23.9 ± 0.18f 19.1 ± 0.09e
­T2 Cold Water-10 °C 29.7 ± 0.13j 25.1 ± 0.11k 22.8 ± 0.19j 20.9 ± 0.20j 19.3 ± 0.32j 18.7 ± 0.25f
­T3 Hot Water-60 °C 37.4 ± 0.19e 33.7 ± 0.17d 27.9 ± 0.22f 24.7 ± 0.13f 21.0 ± 0.25 h 17.4 ± 0.17g
Chemical treatments
­T4 NaOH-0.1% 32.2 ± 0.26i 30.2 ± 0.25h 25.5 ± 0.16h 20.3 ± 0.27k 18.4 ± 0.19k 16.1 ± 0.27h
­T5 NaOH-0.25% 21.3 ± 0.32l 19.1 ± 0.28m 16.6 ± 0.21l 15.3 ± 0.39m 14.9 ± 0.17m 12.6 ± 0.19k
­T6 SDS-ME-1% 36.5 ± 0.18f 31.3 ± 0.18g 30.0 ± 0.18d 28.1 ± 0.16d 27.5 ± 0.28c 24.8 ± 0.14b
­T7 SDS-ME-2% 34.1 ± 0.15 g 32.9 ± 0.15e 29.5 ± 0.24e 27.7 ± 0.21e 26.4 ± 0.12d 24.7 ± 0.31b
­T8 Propanol-water 18.4 ± 0.08 m 16.6 ± 0.12n 15.6 ± 0.32 m 14.4 ± 0.26n 13.4 ± 0.10n 10.9 ± 0.22 l
­T9 Na-bisulphite-0.1% 39.1 ± 0.22d 34.9 ± 0.20c 27.5 ± 0.22g 23.5 ± 0.13h 22.4 ± 0.17g 15.9 ± 0.11h
­T10 Na-bisulphite-1.7% 33.3 ± 0.14h 29.8 ± 0.13i 24.6 ± 0.40i 21.7 ± 0.27i 19.7 ± 0.13l 14.0 ± 0.10i
­T11 Na-hypochlorite 42.1 ± 0.29b 37.2 ± 0.34b 32.7 ± 0.13b 30.4 ± 0.34b 29.9 ± 0.37b 26.6 ± 0.18a
Enzymatic treatments
­T12 Protease 24.5 ± 0.15k 20.5 ± 0.18l 18.6 ± 0.11k 17.3 ± 0.14l 16.0 ± 0.18l 13.1 ± 0.12j
­T13 Cellulase 40.1 ± 0.21c 32.1 ± 0.14f 30.9 ± 0.31c 29.2 ± 0.36c 25.3 ± 0.31e 21.9 ± 0.27d
Combined treatment
­T14 Combined treatment 43.7 ± 0.19a 40.4 ± 0.13a 36.7 ± 0.17a 34.4 ± 0.17a 30.7 ± 0.40a 23.5 ± 0.29c
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.37 0.32 0.39 0.40 0.42 0.34

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5% level of significance when compared
with Fisher’s Least Significant Difference are followed by the same superscript letters

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2817

reflecting or scattering a significant amount of light [44]. changes that may occur during freezing and thawing. In the
Light transmittance (%) of starch on the 5th day ranged from present investigation, higher syneresis by starch from T ­ 10
10.9 to 26.6%. At the 5th day, higher light transmittance (Na-bisulphite-1.7%) treatment could be due to the acid-
(26.6%) was recorded by starch from T ­ 11 (Na-hypochlorite) thinning process leading to an increased proportion of linear
followed by ­T6 (SDS-ME-1%), ­T7 (SDS-ME-2%) and ­T14 chains in the sample that increases the tendency to retro-
(Combined treatment) treatment; whereas, lower (10.9%) grade. The tendency to retrogradation is directly related to
was observed by starch from T ­ 8 (Propanol-water) (Fig. 4). the proportion of linear chains and the time needed for align-
Overall, the starch from combined treatment (­ T14) had sig- ment of these linear chains [12]. Lower syneresis in starch
nificantly higher light transmittance than starch from all from combined treatment was due to the effect of chemicals
physical and enzymatic treatments. Na-hypochlorite treated SDS:ME, NaOH, NaOCl contained in the treatment that
starches showed higher initial transmittance than native resulted in lesser retrogradation in amylose and amylopectin
starch because the oxidized starch had a lower tendency chains and hence lower syneresis. SDS:ME form a complex
for molecular re-association. The presence of hydrophilic with the amylose component and thus make the amylopectin
functional groups, especially carboxyl groups, in oxidized component independent of the amylose, at least in the low
starches might be responsible for the higher transmittance amylopectin region.
[5].
The syneresis (%) increased from 1st day to 5th day of Pasting properties
starch paste storage. Syneresis (%) on the 5th day ranged
from 18.8 to 48.2% (Table 7). At the 5th day of starch The highest PV was recorded in the starch from T ­ 1, followed
paste storage at low temperature, the lower value (18.8%) by that in the starch from combined treatment; the lowest
was recorded in starch from combined treatment ­(T14) PV was observed in starch from ­T10 (Na-bisulfite-1.7%)
and higher (48.2%) in treatment T ­ 10 (Na-bisulphite-1.7%) (Table 8). Similar results have been reported by Jyothi et al.
(Fig. 5). Throughout the period of observation, the starch [45]. Peak viscosity is a measure of the water-binding capac-
extracted with combined treatment recorded lower syner- ity of starch and of the ease with which the starch gran-
esis than the other treatments. On the 5th day, the higher ules disintegrate; often correlates with the quality of the
syneresis (48.2%) was recorded in starch from treatment final product [5]. The higher PV noted in the starch from
­T10 (Na-bisulphite-1.7%). Thus, freeze–thaw stability of treatment ­T1 was due to the greater rigidity and integrity
starch was better for combined treatment (­ T14), while Na- of the granules, which, in turn, was due to the presence of
bisulphite-1.7% extracted starch showed poor freeze–thaw amylose [14]. However, the starch from combined treatment
stability. The amount of syneresis is a useful indicator of also maintained the PV due to the presence of NaOH that
the tendency of starch to retrograde [31]. Freeze–thaw enhanced starch swelling, causing an increase in viscosity.
stability is an important property that is used to evaluate The highest trough viscosity (5328 cP) was observed in
the ability of starch to withstand the undesirable physical starch from combined treatment (­ T14) and the lowest (2913

Fig. 4  Effect of extraction methods on transmittance of potato starch when compared with Fisher’s Least Significant Difference are fol-
at 5th day of observation. Data represent the mean ± standard devia- lowed by the same superscript letters
tion. Means that did not differ significantly at 5% level of significance

13
2818 Neeraj et al.

Table 7  Effect of extraction methods on syneresis (%) of potato starch

Treatments Day
1st 2nd 3rd 4th 5th

Water treatments
­T1 Control (Water-30 °C) 4.1 ± 0.48f 7.3 ± 0.24g 12.9 ± 0.27g 23.7 ± 0.22e 27.1 ± 0.25h
­T2 Cold Water-10 °C 6.9 ± 0.29d 10.6 ± 0.43f 14.2 ± 0.42f 20.8 ± 0.38f 34.1 ± 0.62e
­T3 Hot Water-60 °C 9.0 ± 0.36b 13.7 ± 0.48d 22.3 ± 0.12d 31.1 ± 0.14c 41.1 ± 0.19c
Chemical treatments
­T4 NaOH-0.1% 5.3 ± 0.17e 12.5 ± 0.40e 15.5 ± 0.66e 24.9 ± 0.19d 29.9 ± 0.23g
­T5 NaOH-0.25% 2.4 ± 0.29h 6.9 ± 0.15g 15.3 ± 0.53e 23.5 ± 0.21e 31.7 ± 0.28f
­T6 SDS-ME-1% 1.6 ± 0.10i 4.7 ± 0.12i 9.7 ± 0.33i 17.8 ± 0.14b 23.4 ± 0.21k
­T7 SDS-ME-2% 0.3 ± 0.04j 3.8 ± 0.18j 5.5 ± 0.11k 15.5 ± 0.31c 20.0 ± 0.40m
­T8 Propanol-water 20.5 ± 0.53a 29.8 ± 0.15a 35.8 ± 0.40a 38.7 ± 0.45b 45.7 ± 0.51b
­T9 Na-bisulphite-0.1% 7.9 ± 0.38c 15.7 ± 0.57c 25.9 ± 0.22c 31.0 ± 0.27c 38.5 ± 0.33d
­T10 Na-bisulphite-1.7% 20.4 ± 0.25a 25.4 ± 0.89b 30.9 ± 0.23b 40.7 ± 0.31a 48.2 ± 0.36a
­T11 Na-hypochlorite 3.4 ± 0.47g 5.8 ± 0.36h 11.6 ± 0.15h 15.7 ± 0.21i 22.0 ± 0.29l
Enzymatic treatments
­T12 Protease 2.8 ± 0.13h 3.3 ± 0.15jk 8.7 ± 0.57j 13.0 ± 0.11j 25.7 ± 0.17i
­T13 Cellulase 1.7 ± 0.20i 2.9 ± 0.10k 4.9 ± 0.14k 19.1 ± 0.33g 24.6 ± 0.42j
Combined treatment
­T14 Combined treatment 0.2 ± 0.03j 0.7 ± 0.14l 1.6 ± 0.17l 6.3 ± 0.12k 18.8 ± 0.36n
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 0.52 0.63 0.59 0.44 0.58

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5% level of significance when compared
with Fisher’s Least Significant Difference are followed by the same superscript letters

Fig. 5  Effect of extraction methods on syneresis of potato starch at when compared with Fisher’s Least Significant Difference are fol-
5th day of observation. Data represent the mean ± standard devia- lowed by the same superscript letters
tion. Means that did not differ significantly at 5% level of significance

cP), in starch from 1.7% Na-bisulfite ­(T10) treatment. The combined treatment was significantly lower than that in the
highest breakdown viscosity (892 cP) was observed in the treatment ­T1. The breakdown is a measure of the response
starch from cold-water treatment ­(T2) followed by that in the of starch paste to shear-thinning during the holding period at
starch from T­ 1 and the lowest (82 cP) in starch from 0.01% 95 °C [14]. These results are consistent with the findings of
protease ­(T12). The breakdown viscosity of the starch from Kaur et al. [31], who reported that the extent of breakdown

13
Physicochemical, morphological, functional, and pasting properties of potato starch as a… 2819

Table 8  Effect of extraction methods on the pasting and viscosity properties of potato starch
Treatment Peak viscosity Trough viscos- Breakdown Final viscosity Setback vis- Peak time Pasting temp. Gelatinization
(cP) ity (cP) viscosity (cP) (cP) cosity (cP) (min.) (°C) temp (°C)

Physical
­T1 Control (Water-30 °C) 5673 ± 49.1a 4815 ± 44.1e 858 ± 14.6b 5807 ± 50.3e 991 ± 34.3h 6.3 ± 0.13c 69.8 ± 0.62c 95.1 ± 0.03
d g a j k d
­T2 Cold Water-10 °C 5193 ± 55.3 4301 ± 37.2 892 ± 10.1 4831 ± 30.2 530 ± 15.3 6.0 ± 0.09 68.4 ± 0.78d 95.1 ± 0.02
­T3 Hot Water-60 °C 4108 ± 35.0h 3900 ± 29.5i 207 ± 8.4jk 5738 ± 43.3ef 1838 ± 20.7d 7.0 ± 0.09a 70.3 ± 0.53bc 95.0 ± 0.05
Chemical
­T4 NaOH-0.1% 5355 ± 66.9c 5123 ± 46.9bc 232 ± 11.1hi 7726 ± 59.7b 2603 ± 36.1b 7.0 ± 0.08a 66.6 ± 0.69f 95.0 ± 0.05
b b f a a a
­T5 NaOH-0.25% 5509 ± 38.2 5192 ± 59.0 317 ± 15.4 7875 ± 54.6 2683 ± 24.7 7.0 ± 0.05 66.9 ± 0.50f 95.0 ± 0.08
­T6 SDS-ME-1% 3823 ± 74.6i 3607 ± 33.1k 216 ± 6.9ij 4688 ± 49.4k 1072 ± 21.9g 6.0 ± 0.12d 68.3 ± 0.52d 95.0 ± 0.03
­T7 SDS-ME-2% 4341 ± 58.7g 3731 ± 50.5j 609 ± 16.4c 4988 ± 56.7i 1257 ± 14.3f 5.1 ± 0.02f 67.9 ± 0.42de 95.2 ± 0.06
­T8 Propanol-water 4940 ± 37.3f 4659 ± 56.5f 281 ± 12.3g 5527 ± 62.8g 868 ± 17.3i 7.0 ± 0.14a 71.6 ± 0.75a 95.0 ± 0.05
­T9 Na-bisulphite-0.1% 5490 ± 42.2b 5099 ± 32.5c 391 ± 13.2d 5683 ± 87.3f 584 ± 23.9j 5.7 ± 0.07e 68.4 ± 0.43d 95.1 ± 0.03
­T10 Na-bisulphite-1.7% 3280 ± 29.3j 2913 ± 26.7 l 367 ± 12.1e 4509 ± 69.4l 1596 ± 37.8e 5.2 ± 0.04f 67.0 ± 0.42ef 95.2 ± 0.03
­T11 Na-hypochlorite 5065 ± 61.8e 4947 ± 40.3d 118 ± 4.4l 5363 ± 37.3h 416 ± 5.6m 7.0 ± 0.03a 67.1 ± 0.54ef 95.1 ± 0.00
Enzymatic
­T12 Protease 4291 ± 52.0g 4209 ± 28.9h 82 ± 5.6m 6437 ± 73.1c 2228 ± 25.3c 7.0 ± 0.08a 71.1 ± 0.33ab 95.0 ± 0.03
­T13 Cellulase 5282 ± 34.5c 4787 ± 61.8e 193 ± 7.1k 5336 ± 40.3h 549 ± 9.4jk 6.7 ± 0.05b 70.7 ± 0.64bc 95.0 ± 0.03
Combined
­T14 Combined treatment 5574 ± 80.2b 5328 ± 42.6a 246 ± 10.4h 5997 ± 64.2d 469 ± 29.7l 6.2 ± 0.05c 68.6 ± 0.47d 95.0 ± 0.03
(T1 + ­T5 + ­T7 + ­T11 + ­T13)
CD at 5% 88.6 72.1 18.6 96.4 40.9 0.15 0.94 NS

Data represent the mean ± standard deviation. Means within a column that did not differ significantly at 5% level of significance when compared
with Fisher’s Least Significant Difference are followed by the same superscript letters

in hydrolyzed starches was lower than that seen in non- readily ruptured by mechanical shear. Adebowale et al. [48]
hydrolyzed starches. Low breakdown viscosity is favour- attributed such decrease in SBV of NaOCl-treated starch to
able for pasta noodles with the improvement of the texture partial cleavage of glycosidic linkages from oxidation result-
quality of noodles. ing in a decrease in chain length of the starch molecules.
The highest final viscosity (FV) was observed in starch The peak time was varied from 7.0 to 5.1 min in starch from
from NaOH treatments (­ T4, ­T5) and the lowest in starch from different treatments. Pasting temperature is the temperature
­T10 (Na-bisulfite-1.7%). Final viscosity is a measure of the at which starch begins to thicken. The strengthening of intra-
water-binding capacity of starch, and the treatments with granular bonds makes the starch more resistant to heat: it
NaOH enhanced the swelling, thereby increasing the viscos- takes higher temperatures to disintegrate the structure and
ity probably because of the presence of the anions ­(OH−), therefore to form a paste [31]. In the present investigation,
which attach themselves to specific sites on the granules and the highest pasting temperature (71.6 °C) was observed in
create a large hydration sphere [46]. The increase in FV may starch from ­T8 (propanol and water) and the lowest (66.6 °C)
be due to the aggregation of amylose molecules, and similar in starch from T ­ 4 (0.1% NaOH). The pasting temperature
results have been reported by other workers also [47]. of the starch from combined treatment was 68.6 °C. These
Setback viscosity (SBV) is the difference between the FV results match with findings obtained by Singh et al. [49],
and the trough (hot) viscosity in the pasting curve and is a who attributed the lowering of peak pasting temperatures
measure of the degree of re-association among the starch in SDS and NaOH treatments to their efficacy in removing
molecules during cooling: the process involves amylose [29] surface lipids, which makes the granules more permeable to
leached from the swollen starch granules. The highest SV water during heating.
was observed in the starch from treatments involving NaOH
­(T4, ­T5) and the lowest in the starch from sodium hypochlo-
rite treatment (Table 8). The value recorded in the combined Conclusion
treatment was significantly lower than the values of all the
treatments except treatment T­ 11. The higher values observed Overall, a single method was not sufficient for extracting
in the NaOH-treated starch indicate that failure of the granu- starch with desirable characteristics. So, a combination of
lar structure was minimal in those treatments: granules of physical, chemical, and enzymatic treatments was needed
starch obtained by the surface treatment tend to swell or to produce starch having improved physicochemical and
gelatinize at low temperatures, and the swollen granules are functional properties. Therefore, a combined method for

13
2820 Neeraj et al.

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