Physical properties of starch of Asian-adapted potato varieties
Transcript of Physical properties of starch of Asian-adapted potato varieties
Physical properties of starch of Asian-adaptedpotato varietiesZenaida N Ganga1 and Harold Corke2*1NPRCRTC, Benguet State University, La Trinidad, Benguet, 2601 Philippines2Cereal Science Laboratory, Department of Botany, University of Hong Kong, Pokfulam Road, Hong Kong
Abstract: Starch was puri®ed from 24 potato (Solanum tuberosum L) genotypes (varieties and
breeding selections) intended for production in Philippine conditions. Genotypes varied widely in their
thermal, pasting and other physicochemical properties. The locally bred Philippine varieties and
selected advanced clones had comparable starch qualities to the more widely grown commercial
varieties from Europe and the USA. The genotypes B71-240.2, LBR 1±5, and the three TPS hybrids
(Serrana�LT-7, HPS 7/67 and HPS II/67) had some starch properties that could make them suitable
for processing and starch production. Other genotypes have unique properties that could be useful for
industrial or other purposes. The addition of 10g litreÿ1 NaCl solution signi®cantly decreased and
stabilized starch pasting values of all the potato genotypes, but genotypes varied in their relative
response to 10g litreÿ1 NaCl.
# 1999 Society of Chemical Industry
Keywords: starch; potato; processing quality; Solanum tuberosum; thermal properties; pasting properties; texture
INTRODUCTIONPotato (Solanum tuberosum L) production has signi®-
cantly increased in recent years in many developing
countries, particularly in Asia where it has became
more important as a food and industrial crop. One of
the major reasons for this is the opening up and
expansion of markets for processed potatoes,1 as a
result of changing lifestyles and eating habits including
development of the fast food sector and production of
varied snack items. The potential for processed potato
is great, and several multinational and local companies
have already established processing plants in some
Asian countries. There is also interest in producing
starch from the large amounts of trim waste and reject
potatoes from these processing plants.
Potato starch is preferred over other starches in
many food, adhesive and oil-®eld applications as well
as in papermaking because it can give high consistency
on pasting, and it excels in ®lm-forming and binding
characteristics, with these properties also carried
through to its derivatives.2 In East Asia, there is great
potential for use of potato in the manufacture of starch
noodles. Previous reports showed that some potato
starch noodles are superior to or comparable with
other types of starch noodle (eg mung bean, rice or
sweetpotato). In many cases, potato is preferred over
corn and cereal starches for its neutral taste, and
higher noodle transparency and ¯exibility.3 Potato
starch is also used as stabilizer or as a binder in the
production of wheat-¯our-based instant noodles,4 or
as a texturizer to improve the eating quality of wheat
noodles, a common practice in Japan.5
One of the limiting factors in potato production in
these Asian areas is the lack of appropriate processing
varieties that meet the standards for the speci®c
industry uses since most of the varieties grown in Asia
are table or cooking types for the fresh market. The
objective of this study was to evaluate the starch
properties of diverse potato genotypes grown in the
Philippines including introduced varieties and selected
advanced clones, and thus to be able to identify
varieties that are suitable for processing and/or starch
production.
MATERIALS AND METHODSGermplasmThree sets of potato genotypes either introduced or
commercially grown in the Philippines were evaluated
(Table 1). Set A and set B consisted of introduced
commercial varieties from the Netherlands and the
USA, respectively. Set C are varieties and TPS hybrid
selections introduced through the International Potato
Center (CIP), Lima, Peru, and have been selected and
recommended in the Philippines. The entries I-1035
and LBR 1±5 (locally known as Montanosa and BSU
Po-3, respectively) and B71-240.2 are recommended
highland varieties which are resistant to late blight
Journal of the Science of Food and Agriculture J Sci Food Agric 79:1642±1646 (1999)
* Correspondence to: H. Corke, Cereal Science Laboratory, Department of Botany, The University of Hong Kong, Pokfulam Road, HongKongE-mail: [email protected](Received 23 April 1998; revised version received 22 December 1998; accepted 6 May)
# 1999 Society of Chemical Industry. J Sci Food Agric 0022±5142/99/$17.50 1642
(Phytophthora infestans Mont de Bary); while the clone
385130.8 is heat-tolerant and was selected for lowland
potato production areas. The clone B71-240.2, locally
known as Dalisay in the Philippines, is also a
recommended variety widely grown in China. The
variety Granola, a cooking-type potato from Germany,
is the most popular variety in the Philippines. The true
potato seed (TPS) hybrids, HPS 7/67, and HPS II/67
are from India while Serrana � LT-7 was bred at CIP.
The ®rst two hybrids are also being grown/promoted
in Vietnam, Sri Lanka and Indonesia.
Starch extraction and purificationPotato starch was extracted following Kim et al6
(1995) with a few modi®cations. This method
provides a high yield of clean starch with little loss.
Tubers were thoroughly washed, peeled and cut into
2±3-cm cubes. A 400-g batch was macerated at low
speed using a Kenwood Table Mixer (Major 250
Model) (Kenwood, England) with 400ml distilled
water for 45s and the mixture was left to stand for
20min. The liquid was decanted and the remaining
solids were macerated for another 45s. The mixture
was added back to the sediment and held at room
temperature for 40min. The liquid was decanted and
discarded, and a further 500ml of water was added to
the sediment before sieving with a 250-mm sieve. The
remaining sediment in the sieve was washed off with
200ml water and resuspended with 400ml water; after
which it was macerated for 45s and sieved (250-mm
sieve). The starch in the ®ltrate and the rinse water
were allowed to settle for 30 to 45min and the liquid
decanted and discarded. The starch was resuspended
in a litre of water and passed through a 250-mm sieve.
The remaining solids on the sieve were rinsed with
another litre of water before they were discarded. The
starch in the ®ltrate and the rinse water was allowed to
settle for 30 to 45min and the liquid decanted and
discarded. The starch was dried in a convection oven
at 35°C for two days and then ground with a mortar
and pestle and passed through a 250-mm sieve.
Samples were stored in air-tight containers at room
temperature until use.
Amylose content, swelling volume and solubilityDuplicate starch samples were analysed for amylose
content following an iodine-binding spectrophoto-
metric procedure;7 swelling volume was done follow-
ing Crosbie8 using 200mg of starch instead of the
standard 350mg; and solubility was expressed as the
Table 1. Amylose content, solubility,swelling volume, and thermalproperties of starch of 24 potatogenotypes
Genotype
Amylose
(%)
Solubility
(%)
Swelling
(mlgÿ1) To (°C) Tp (°C) Tc (°C) DH Jgÿ1
Set A
Baraka 25.7 7.5 45.3 62.9 68.0 77.6 15.3
Bimonda 24.1 6.6 42.9 66.2 71.8 83.1 15.2
Columbus 22.6 7.3 47.4 61.9 68.0 78.0 16.2
Diamant 22.3 7.7 45.9 61.5 67.5 77.4 14.8
Donald 27.6 7.3 45.3 62.8 68.4 78.4 15.5
Hertha 21.8 7.6 43.5 62.6 69.2 78.6 15.5
Remarka 20.1 7.6 44.1 63.8 68.6 76.9 13.5
Serenade 29.9 7.6 45.9 64.1 68.7 77.9 14.7
Signal 24.9 7.8 45.6 63.4 68.5 77.7 14.3
Van Gogh 34.5 7.7 44.4 65.2 71.1 81.0 14.7
Set B
Russet
Burbank
35.1 8.1 47.5 61.5 66.6 77.5 15.0
Chipetah 32.8 7.9 46.5 62.2 68.0 78.3 14.8
Granchip 32.3 8.1 48.6 62.1 68.1 69.6 13.7
Itasca 33.1 7.5 44.4 62.5 67.3 69.9 13.7
Norchip 31.2 8.1 49.3 59.6 65.4 75.2 14.4
Shepody 29.8 8.2 42.9 62.3 67.9 77.9 15.0
Set C
B71-240.2 32.9 7.8 47.8 63.9 68.4 77.9 15.5
I-1035 33.4 7.6 48.0 60.1 65.4 75.2 14.8
Ser � LT-7 22.9 7.7 41.6 66.0 71.5 82.2 15.0
HPS 7/67 26.8 8.0 43.8 67.2 70.8 80.9 14.6
HPS II/67 27.8 8.4 44.2 64.8 69.7 79.2 16.0
385130.8 31.8 8.4 42.7 63.2 69.0 78.3 14.6
LBR 1±5 32.9 7.9 45.3 61.8 66.4 76.2 14.2
Granola 34.3 7.7 45.4 61.4 67.7 77.2 14.2
Mean 28.7 7.8 45.3 63.1 68.4 77.7 14.9
SD 4.6 0.38 2.01 1.9 2.6 3.1 0.8
J Sci Food Agric 79:1642±1646 (1999) 1643
Quality of potato starch
amount of starch leached out into the supernatant in
the swelling volume test.
Starch thermal propertiesThe gelatinization properties of triplicate samples of
the different potato starch genotypes were determined
using a Mettler DSC-20 Differential Scanning Calori-
meter (Mettler-Toledo AG Instruments, Naenikon-
Uster, Switzerland) equipped with a Mettler TC11
data analysis station. Starch samples (2±3mg dwb)
were placed in aluminum crucibles and distilled water
was added to make a 1:3 (w:w, dwb) starch:water
mixture. The crucible was hermetically sealed and
allowed to equilibrate for about 1h before analysis. An
empty aluminum crucible was used as a reference. The
sample was heated from 30°C to 120°C at a heating
rate of 10°C minÿ1. The gelatinization temperature
parameters in°C of To±onset, Tp±peak, Tc±conclu-
sion and enthalpy (DH, Jgÿ1) were determined.
Starch pasting propertiesThe pasting properties of starch samples were deter-
mined using a Rapid Visco-Analyzer Model 3D (RVA)
(Newport Scienti®c Pty Ltd Warriewood, Australia).
A suspension of 2gm starch in 25g accurately weighed
distilled water or 10g litreÿ1 NaCl solution was
subjected to a 13-min continuous controlled heating
and cooling cycle (see Fig 1) under constant shear.
The peak viscosity (peak), holding or hot paste
viscosity (HPV), and ®nal or cool paste viscosity
(CPV) (Fig 1) were recorded. Stability ratio was
calculated as HPV/peak. Duplicate tests were done for
each starch sample.
Starch texture analysisAfter the Rapid Visco-Analyzer (RVA) test the starch
pastes were kept at room temperature for 3±4h then
evaluated for their gel texture properties using a
Texture Analyzer TA.XT2 (Stable Micro Systems,
Godalming, England). A cylindrical ¯at-ended 5-mm
probe was used in a standard two-cycle program at a
testing speed of 10mm minÿ1. Hardness was reported.
RESULTS AND DISCUSSIONAmylose content, solubility and swelling propertiesRelatively wide variation was observed in the amylose
content of the different genotypes with values ranging
from 20.1% to 35.1% (Table 1). High values were
exhibited by Russet Burbank, Van Gogh and Granola.
Some genotypes had higher amylose contents than
previously reported by Wiesenborn et al9 who used the
same method of analysis. The higher values could be
attributed to differences in starch extraction and
variation in growing conditions.
The variety Norchip had the highest swelling
volume (Table 1) while the TPS hybrid, Serrana �LT-7 had the lowest. The variation among the
genotypes, however, was quite low. The results of
the solubility test (Table 1) showed a similar pattern
among the genotypes with very little variation (SD of
�2.01). The variety Bimonda had the lowest solubility
while the highest value was observed in TPS hybrid
HPS II/67 and the clone 385130.8. Correlation
analysis showed that amylose was signi®cantly corre-
lated with swelling volume but not with solubility
(Table 2). On the other hand, solubility was negatively
correlated with setback and stability ratios and
positively correlated with peak values of the RVA test.
Thermal propertiesEvaluation of thermal properties (Table 1) showed
that variation in To was very slight; with TPS hybrid
HPS 7/67 and the variety Norchip having the highest
and the lowest values, respectively. However, a fairly
substantial range in Tp values from 65.4°C to 71.8°C,
and Tc from 69.6°C to 83.1°C was found. Bimonda
and Van Gogh (Set A) and Ser. � LT-7 and HPS 7/67
(Set C) had Tp above 70°C. The variety Bimonda had
the highest Tc while varieties Granchip and Itasca had
the lowest. Reasons for variation in gelatinization
temperatures include variation in degree of crystal-
linity which imparts structural stability,10 or a more
stable amorphous region or variation in degree of
chain branching.11 High gelatinization enthalpy values
were observed in the genotypes Columbus and HPS
11/67. Gelatinization enthalpy may be high when the
granular structure is more stable because of greater
crystallinity.11
Pasting characteristicsStarch pasting characteristics (Table 3, Fig 1) showed
a wide range among genotypes in distilled water, with
peak viscosity values ranging from 253 to 752,
although only 7.4% starch was used. It is well known
that unmodi®ed potato starch has an exceptionally
high cooked viscosity per dry weight of starch; partly
attributed to its high content of starch phosphate
esters. Gelatinized starch granules however, are readily
disrupted by shear during conveying and mixing
operations, resulting in greatly reduced viscosity.9
(Wiesenborn et al. 1994). There was a rapid increase
of viscosity to the peak viscosity after the onset of
Figure 1. Representative Rapid Visco-Analyzer pasting profiles of74g litreÿ1 potato starch in water for four genotypes (in order of decreasingpeak viscosity, TPS A, 385130.8, Baraka, and Diamant). Pastingparameters of Peak, HPV and CPV are indicated.
1644 J Sci Food Agric 79:1642±1646 (1999)
ZN Ganga, H Corke
pasting for most of the genotypes tested. Similar
results were obtained by Kim et al6 in their evaluation
of potato starch. The highest pasting peak values were
exhibited by two TPS hybrids, Serrana x LT-7 and
HPS II/67 and the clone B71-240.2. Some of the
European (Set A) and US (Set B) varieties which were
bred for processing either for chipping and/or fries had
also exhibited high peak values. Genotypic differences
contributed to the wide variation in paste characteris-
tics of the 24 entries.
Higher viscosity was generally observed using
distilled water, but this was signi®cantly decreased to
a more uniform value (ie more stable pasting curve)
using 10g litreÿ1 NaCl solution (Table 3). The pasting
peak values in salt solution ranged from only 192 to
239, much lower than the values observed in distilled
water. Potato starch is highly affected by electro-
lytes.2,12±14 Pasting viscosity is higher in distilled water
than in hard water containing calcium salts or in saline
solution. Muhrbeck and Eliasson15 reported that the
Table 2. Correlation coefficients forphysical parameters of potato starchdata (pasting parameters in water)
CPV HPV Peak
Stability
ratio Amylose Solubility Swelling
CPV 1.00
HPV 0.68*Peak ÿ0.44* ÿ0.19
Stability ratio 0.64* 0.46* ÿ0.92*Amylose ÿ0.17 ÿ0.34 0.12 ÿ0.26
Solubility ÿ0.01 ÿ0.16 0.51* ÿ0.54* 0.40
Swelling ÿ0.29 ÿ0.48* ÿ0.07 ÿ0.16 0.41* 0.11
To 0.23 0.36 0.07 0.16 ÿ0.34 ÿ0.18 ÿ0.66*Tp 0.06 0.16 0.22 ÿ0.05 ÿ0.24 0.02 ÿ0.67*Tc 0.21 0.21 ÿ0.12 0.29 ÿ0.36 ÿ0.21 ÿ0.54*DH ÿ0.20 ÿ0.32 0.07 ÿ0.08 ÿ0.24 ÿ0.17 ÿ0.05
* Signi®cant at p<0.05; n =24.
Table 3. Pasting parameters and gel hardness in water, and pasting parameters in 10g litreÿ1 NaCl of 24 potato genotypes
Genotype In distilled water In 10g litreÿ1 NaCl
Peak HPV CPV Stability ratio Hardness Peak HPV CPV Stability ratio
Set A
Baraka 425 227 253 0.53 60.9 271 199 233 0.73
Bimonda 301 266 241 0.88 37.0 208 176 223 0.84
Columbus 390 219 249 0.56 64.2 200 167 254 0.83
Diamant 275 218 288 0.79 62.1 195 168 276 0.86
Donald 253 212 281 0.84 57.0 198 159 223 0.80
Hertha 338 261 324 0.77 60.7 197 176 257 0.89
Remarka 368 299 341 0.81 61.4 192 178 292 0.92
Serenade 306 267 352 0.87 66.4 197 170 278 0.86
Signal 392 241 272 0.62 38.2 213 183 258 0.86
Van Gogh 295 246 358 0.83 35.0 186 157 249 0.84
Set B
Russet Burbank 478 229 258 0.48 47.9 235 173 237 0.74
Chipetah 268 222 283 0.83 35.6 228 172 244 0.75
Granchip 583 219 243 0.38 44.3 234 177 232 0.76
Itasca 459 235 260 0.51 36.9 217 177 256 0.82
Norchip 519 222 252 0.43 49.9 198 164 251 0.83
Shepody 585 222 245 0.38 38.3 219 179 258 0.82
Set C
B71-240.2 637 215 240 0.34 36.0 218 175 232 0.80
I-1035 401 196 228 0.49 34.2 239 170 215 0.71
TPS A 752 229 262 0.31 35.6 198 162 272 0.82
TPS B 352 222 261 0.63 39.0 201 167 255 0.83
TPS C 636 221 253 0.35 38.3 213 184 256 0.86
385130.8 574 270 298 0.47 36.0 218 181 271 0.83
LBR 1±5 365 233 267 0.64 48.2 222 187 266 0.84
Granola 372 228 261 0.61 40.9 209 179 253 0.86
Mean 423 235 80 0.61 46.0 212 173 253 0.82
SD 136 24 39 0.19 11.3 19 10 19 0.49
J Sci Food Agric 79:1642±1646 (1999) 1645
Quality of potato starch
reduction in swelling volume with sodium chloride
explains the large reduction in the dynamic viscosity of
potato starch pastes on addition of low levels of
electrolytes. The effects of 0.1g litreÿ1 sodium chlor-
ide and 0.1g litreÿ1 sulphite on the swelling and
solubility of potato starch were similar.16 Different
genotypes varied in their reactions to NaCl, eg the
TPS hybrid Serrana � Lt-7 which had unusually high
peak viscosity of 752 in distilled water was greatly
reduced to 198 with the use of 10g litreÿ1 NaCl
solution while in the variety Chipetah, very little effect
was observed with its peak value of 268 in distilled
water reduced to 228 (Table 3). The change on CPV
value was not so dramatic except for some Dutch
varieties (Set A) like Donald, Hertha, Remarka,
Serenade and Van Gogh which had decreased CPV
in 10g litreÿ1 NaCl solution. Likewise the HPV values
were signi®cantly reduced with the use of 10g litreÿ1
NaCl solution in varieties Baraka, Bimonda, Hertha,
Remarka and Serenade. The stability ratio followed
the same pattern with most of the genotypes exhibiting
higher values in 10g litreÿ1 NaCl.
Gel hardnessThe hardness of the gel formed by the starch after
pasting varied by genotypes (Table 3). The Set A or
the Dutch varieties showed more variability than the
rest of the entries. The highest value was observed in
the genotype Serenade while varieties Bimonda, Signal
and Van Gogh had low values. Variation within the
other two sets (B and C) of genotypes was less. Set C
genotypes, which are mostly table-type potatoes, had
lower values.
CONCLUSIONKnowledge of the starch viscosity characteristics of
incoming raw material is important in industrial potato
processing for several reasons. Monitoring and control
of incoming raw material enables appropriate deter-
mination of suitability for particular uses. It enables
selection of suitable varieties for speci®c end-uses, and
more informed speci®cations in contracting with
farmers for supply of material. The impact of proces-
sing variables (such as variation in water quality which
may impart signi®cant differences in viscosity beha-
vior) can also be assessed. We have shown that wide
variation exists in starch properties of Philippine-
adapted potato genotypes. Breeders and processors
should consider these differences in formulating
strategies for the future development of the crop.
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