J Food Sci Technol

DOI 10.1007/s13197-015-1984-z

ORIGINAL ARTICLE

Enzymatically hydrolysed, acetylated and dually modified

corn starch: physico-chemical, rheological and nutritional
properties and effects on cake quality
Mouna Sahnoun 1 & Nouha Ismail 1 & Radhouane Kammoun 1

Revised: 13 July 2015 / Accepted: 28 July 2015

# Association of Food Scientists & Technologists (India) 2015

Abstract Corn starch was treated by enzymatic hydrolysis Keywords Corn starch, α-amylase . Aspergillus oryzae S2 .
with Aspergillus oryzae S2 α-amylase, acetylation with vinyl Acetylated . Dual modification . Cake properties
acetate, and dual modification. The dual modified starch
displayed a higher substitution degree than the acetylated
starch and lower reducing sugar content than the hydrolysed Introduction
starch. The results revealed that the cooling viscosity and am-
ylose content of those products decrease (P < 0.05). An in- Starch is an agricultural raw material and essential dietary
crease in moisture, water, and oil absorption capacity was carbohydrate for human nutrition (Maarel and Leemhuis
observed for the acetylated starch and, which was less pro- 2013). Three categories of digestible starches are distin-
nounced for the enzymatically hydrolysed starch but more guished by the rate at which glucose is formed and absorbed
pronounced for the enzymatically hydrolysed acetylated prod- in the blood (Zhang and Hamaker 2009). Rapidly digestible
uct. The latter product underwent an increase in resistant starches (RDS) are hydrolysed in the small intestine within the
starch content, which is induced by a rise in hydrolysis time first 20 min of digestion, whereas slowly digestible starches
to attain about 67 % after 1 h of reaction. The modified starch (SDS) acquire more time to degrade. Resistant starch (RS)
samples were added to cake formulations at 5 and 10 % con- generally escapes digestion in the small intestine and passes
centrations on a wheat flour basis and compared to native through the large intestine as dietary fiber for fermentation by
starch. The results revealed that when applied at 5 % concen- bacteria, where it helps to maintain colon health and protect
trations, the modified starches reduced the hardness, cohesion, against disease (Miao et al. 2014; Jiang et al. 2014). RDS can
adhesion and chewiness of baked cakes and enhanced their induce a rapid increase in blood glucose and insulin levels,
elasticity, volume, height, crust color, and appearance as com- which can lead to various health complications, such as obe-
pared to native starch. These effects were more pronounced sity, diabetes and cardiovascular diseases. The literature
for the cake incorporating the dually modified starch. broadly classifies RS into three different types, namely RS1,
RS2, and RS3 (Hoover and Zhou 2003). RS1 resistant starch
is physically inaccessible to digestive enzymes due to attach-
ment in structures such as intact cells in legumes. RS2 consists
of native crystalline regions of starch granules and retrograded
* Mouna Sahnoun
amylopectin. RS3 has been reported to consist predominantly
mouna.sahnoun@yahoo.fr of retrograded amylose. An additional type of RS, type RS 4,
Nouha Ismail
has been identified as resulting from chemical modifications
(Fuentes-Zaragoza et al. 2011).
Radhouane Kammoun
Native starches have been used in various food and non-
food industries for decades. They have often been reported to
1
Laboratory of Microbial Biotechnology and Engineering Enzymes,
present a number of undesired properties, including is insolu-
Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, bility in cold water, crumbling after heating, and loss of vis-
Road Sidi Mansour 6 km, 3018 Sfax, Tunisia cosity (Sandhu et al. 2015). Moreover, the cooling of a heated
 J Food Sci Technol

native starch suspension often leads to the formation of a extensibility attribute to the modification of gluten wheat
disordered, firm and opaque gel due to hydrogen bonding protein.
between parallel oriented amylose and or long side chains of Considering the promising opportunities that starch modi-
amylopectin and syneresis. The latter process, termed as ret- fication might offer for the production of starch with tailored
rogradation, is irreversible and causes the loss of gel structure properties, this study was undertaken to investigate corn
(Luchese et al. 2015). starch modification by acetylation with vinyl acetate, enzy-
Several methods have been proposed to solve the inconve- matic hydrolysis with Aspergillus oryzae S2 α-amylase, and
niences caused by the inherent limitations of native starch, dual modification. It also aimed to evaluate the effect of those
particularly through the modification of its chemical and/or starch modifications on the physico-chemical properties and
physical profile to maximize its positive attributes and mini- rheological attributes of the final starch end-products. The
mize its negative properties. Acetylation is one of the most modified corn starches were assayed in cake preparations,
common methods used for starch modification; it involves the and the changes they brought in terms of the texture and prop-
substitution of some hydroxyl groups by acetates groups (Xie erties of the baked cakes were investigated.
et al. 2005). Corn acetate starch, which contains 0.5 to 2.5 %
acetyl content, has a lower gelatinization temperature and a
higher peak viscosity than unmodified starch (Raina et al.
Materials and methods
2006; Wickramasinghe et al. 2009; Colussi et al. 2014).
Acetylation also improves the stability and clarity of native
Materials
starches by increasing the degree of swelling and dispersion of
starch granule in the cooling cycle, and also reduces retrogra-
The experimental assays of the present study were performed
dation (Han et al. 2013; Luchese et al. 2015). Because of their
using Amyloglucosidase (3300 U/ml) (Sigma Chemical, St.
desirable properties, acetate starches have been used as
Louis, USA) and 181,481.48 U/g of Aspergillus oryzae S2
binders in soups, snacks, canned, and refrigerated foods.
concentrated crude extract that was free from aflatoxins
However, acetate starches generally lack resistance to high
(Sahnoun et al. 2011) and formulated with dried starch as
temperature, acidity, and shear stress, which is undesirable
previously described elsewhere (Sahnoun et al. 2013).
for several food applications (Xie et al. 2005).
Commercial corn (Zea maize) starch, purchased from the
Various enzymes can be used in starch hydrolysis to alter
Egyptian starch and glucose company, Cairo, was used as
starch structure and achieve desired functionality (Maarel and
native starch. It contained 0.76 % protein (N × 5.70), 0.71 %
Leemhuis 2013; Caliari et al. 2014). Alpha-amylases (EC
ash, 0.58 % lipid, and 91 % carbohydrates. Salt (sodium chlo-
3.2.1.1), key additives for dough and bakery products, are
ride), sugar milk, shortening egg, baking powder and wheat
endo-acting amylases that randomly hydrolyse α-(1–4) gly-
flour, containing 10.47 % protein (N × 5.70), 0.61 % ash,
cosidic bonds of starch polymers, resulting in oligosaccha-
14 % moisture, and 24 % moist gluten, were purchased from
rides with varying lengths and different α-limit dextrins
the local market of Sfax, Tunisia, and used for cake
(Sahnoun et al. 2015). They increase the level of fermentable
preparation.
sugars in the dough, thus promoting the fermentation of yeast
and the formation of Maillard reaction products, which, in
turn, intensify the flavour and crust colour of bakery products Methods
(Goesaert et al. 2005; Sahnoun et al. 2013). Alpha-amylases
also increase dough resistance, elasticity, and softness (Patel Starch characterization
et al. 2012) and decrease dough crumb firmness and hardness
(Kim et al. 2006; Hemalatha et al. 2010; Raghu and Total carbohydrates were determined after total acid hydroly-
Bhattacharya 2010; Gomes-Ruffi et al. 2012). They have, sis (Israilides et al. 1978). Protein content was evaluated by
however, been reported to reduce dough stability and extensi- the Kjeldahl method (Pearson 1970). Lipid content was deter-
bility, which may be attributed to the presence of high mined gravimetrically after Soxhlet extraction using hexane
amounts of amylase-reducing polysaccharides. The latter solvent (Riedel-De Haën, Germany) (AOAC 1984). Dry mat-
break gluten disulphide bridges and, hence, contribute to the ter was determined by oven drying at 105 °C to constant
modification of wheat protein. The addition of oxidizing weight, and ash content was estimated by the combustion in
agents would, therefore, be necessary (Kim et al. 2006; a muffle furnace at 550 °C for 12 h. All contents were
Sahnoun et al. 2013). Nevertheless, and to the authors’ knowl- expressed as matter weight/weight. Tests were performed in
edge, no studies have so far investigated the optimization of triplicates. Moisture content of natives and modified starches
the improver mixture of both oxidizing and reducing agents. was evaluated as weight loss after drying at 105 °C until
Acetyl groups incorporated in starch could act as electron constant weight, and pH was measured by a pH-meter
donors (oxidant) and, hence, improve dough stability and (Eutech Cyberscan 1000, Singapore). Amylose content was
J Food Sci Technol

measured by the colorimetric method of iodine binding capac- In vitro digestion

ity as described by Dura et al. (2014).
The digestibility of the starch was analyzed according to a
slightly modified version of the procedure described by
Acetylation with vinyl acetate Jiang et al. (2014). In brief, Amyloglucosidase (solution I)
(2.16 ml) was diluted to 6.0 ml. Alpha amylase (solution II)
Vinyl acetate was used in accordance with the specifications was prepared by suspending Aspergillus oryzae S2 alpha am-
issued by the Food and Drug Administration (FDA) for the ylase (6.6 g) in water (80.0 ml) under magnetic stirring for
preparation of organic and inorganic monoesters of starch 10 min and then centrifuging the mixture for 10 min at
intended for use in food (Xie et al. 2005). Corn starch acety- 1500×g. A fraction (54.0 ml) of the supernatant was trans-
lation (esterification) was performed according to a slightly ferred into a beaker. Solution III was prepared by mixing
modified version of the method described by Saartrat et al. solution I (6.0 ml), solution II (54.0 ml) and water (4.0 ml).
(2005). In brief, native corn starch (100 g, dry basis) was A starch sample (200 mg) was dispersed into 15 ml of phos-
placed in a 500 ml beaker, and 225 ml of distilled water were phate buffer (0.2 M, pH 5.2) by vortexing, and the solution
added at 25 °C. The mixture was stirred for 1 h until a was equilibrated at 37 °C for 5 min. Enzyme solution III
homogeneous slurry was formed. The pH was adjusted (5.0 ml) was then added, and the whole mixture was shaken
to 8.0 by the drop-wise addition of a 3 % aqueous sodium at (37 °C, 150 rpm). Hydrolysed solution (0.5 ml) was taken at
hydroxide solution. After that, 6 g of vinyl acetate were different time intervals and mixed with 4 ml of absolute eth-
added drop-wise, with the concurrent addition of 3 % so- anol to denature the enzymes. The glucose content of the
dium hydroxide under continuous stirring to keep the pH hydrolysate was determined using the DNS method.
at 8.0–8.4. When the addition of the vinyl acetate was Hydrolysed starch (%) was calculated by multiplying the glu-
complete, the pH was adjusted to 4.5 with 0.4 N HCl to cose content by a factor of 0.9. Each sample was analyzed in
stop the reaction. The slurry was filtered under vacuum, triplicate. The values of different carbohydrate nutritional
washed with twice volumes of distilled water, and dried at fractions (RDS, SDS and RS) were calculated by combining
45 °C for about 24 h. the values of G20 (glucose liberated after 20 min), G120 (glu-
cose liberated after 120 min), FG (free glucose), and TG (total
glucose) using the following formulas:
Preparation of enzymatically hydrolysed of native
and acetylated starch %RDS ¼ ðG20 − FGÞ  0:9  100
%SDS ¼ ðG120 − G20 Þ  0:9  100
%RS ¼ ðTG− FGÞ  0:9  100 − %RDS − %SDS
The slurry was preheated at 10 % (w/w) of (native or acetylat-
ed starch maize) under stirring condition until reaching the
optimal active temperature (50 °C) of Aspergillus oryzae S2
Acetyl content and the degree of substitution (DS)
alpha amylase, which was added at 5800 U/g dry weight of
starch. The pH of the mixture was fixed at optimal pH activity
The acetyl content (expressed as % on dry basis) and degree of
(pH 5.6). After a 10-min hydrolysis phase, the reaction was
substitution (DS) of the corn acetylated starch were deter-
stopped by heating at 70 °C for 10 min, and the solution was
mined as described by Saartrat et al. (2005). An amount of
then cooled to room temperature. The starch was collected by
5 g of starch sample was transferred to a 250 ml beaker and
centrifugation at 5000 × g for 10 min, and dried at 45 °C for
dispersed in 50 ml distilled water. A few drops of phenol-
24 h.
phthalein indicator were added and titrated with sodium hy-
The reducing sugars (ReS) of the product (1 %) were de-
droxide 0.1 N till the appearance of pink color. An amount of
termined as glucose equivalents by the DNS method (Miller
25 ml of 0.45 N NaOH was then added, and the whole mixture
1959) using a calibration curve of glucose solutions with dif-
was shaken for 30 min. The excess alkali was titrated with
ferent concentrations.
0.2 N HCl till the disappearance of the pink color. The 25 ml
of 0.45 N NaOH was titrated as blank. The acetyl content (%)
and degree of substitution (DS) were calculated using the fol-
Rheological properties analysis
lowing equations:
The starch suspension (6 %, v/v) was solubilised in a boiling ðb−sÞ  N  0:043  100
water bath for 30 min. Viscosity (Pa.s) was determined with a % Acetyl content ¼
W ðdry basisÞ
Stress Tech Rheologica Rheometer (reologica instruments
AB, Lund, Sweden) using a steel cone plate (C40/4) under a Where b refers to the volume of 0.2 N HCl utilized to titrate
constant shear rate of 100 s−1 after cooling to 20 °C. blank (ml), s to the volume of 0.2 N HCl utilized to titrate
 J Food Sci Technol

sample (ml), N to the normality of 0.2 N HCl, and W to the Add egg white and 0.5 g salt
mass of the sample (g).

ð162*%ACÞ Mix for 5min

DS ¼
½4300−ð42*%ACÞ
Add sugar

Water holding capacity (WHC)

Mix for 3min
An amount of 1 g of starch was vigorously mixed with 30 ml
of distilled water in a pre-weighed 50 ml polypropylene cen- Add milk
trifuge tube for 1 min. The tube was placed at 30 °C for 1 h,
followed by cooling in ice bath, and then centrifuged for Mix for 4min
15 min at 10,000×g. The supernatant was removed, and the
tube with the precipitate was weighed (Mi et al. 2014). The
WHC was calculated as g of water bound per g of sample on a Add semi-solid margarine and egg
dry basis. yolk

Oil absorption capacity (OAC) Mix for 4min

Oil absorption capacity (OAC) was determined according to a Add flour and dry baker’s yeast
slightly modified version of the De la Hera et al. (2013) meth-
od. In brief, 0.5 g of starch sample was mixed with 6 ml of
Mix for 10min
corn oil in pre-weighed centrifuge tubes. The contents were
stirred for 1 min to diffuse the sample in the oil. After a hold-
ing phase of 30 min, the tubes were centrifuged for 25 min at Final mix
4000×g. The separated oil was removed with a pipette, and the
tubes were inverted for 25 min to drain the oil before Fig. 1 flowchart for cake process conditions
reweighing. Fat absorption capacity was calculated as g of
oil bound per g of sample on a dry basis. respectively. The final mix (60 g) was placed in greased pans
and baked in an oven for 28 min at 180 °C.
Preparation of cake
Evaluation of cake texture
Cake samples were prepared using a slightly modified version
of the procedure described by Karaoglu et al. (2001). The cake
Cake texture was evaluated by the texture profile analysis
mix and preparation method are listed in Table 1, and Fig. 1,
method using a texture analyzer (Lloyd Instruments,
Table 1 Cake Fareham, UK) set at a 0.05 (N) detection range and equipped
preparation formula Ingredients (%) with an aluminium 19-mm diameter cylindrical probe and
1000 (N) load cell. Sample slices of 2 cm thickness were
Flour * 29.42
compressed to 50 % of their initial height at a 10 mm/s speed
Sugar 26.48
in a ‘texture profile analysis’ (TPA) double compression test
Milk 17.65
with a 30 s delay between the 1st and 2nd compression. The
Semisolid margarine 11.77
samples were cut by an electric knife to ensure uniform
Egg white 11.77 shapes. Primary attributes [hardness, cohesion, and springi-
Egg yolk 2.35 ness] and secondary mechanical properties [adhesion and
dry baker’s yeast 0.50 chewiness] were determined from the TPA curves in ac-
Salt 0.05 cordance with well established procedures (Nishinari et al.
Starch** 2013). Hardness refers to the peak force of the first com-
*% Flour levels decreased when amount of
pression cycle; cohesiveness corresponds to the ratio of
starch was added the positive areas of the second cycle to the area of the
**Amount of starch was determined as first cycle; adhesion designates the work necessary to pull
stated in trial plan the compressing plunger away from the sample. The
J Food Sci Technol

height during the time that elapses between the end of the Loaf specific volume
1st compression cycle and the start of the 2nd compres-
sion cycle is defined as springiness. Chewiness is the The specific volume of cake was determined by rapeseed dis-
product of hardness X cohesiveness X springiness. placement as previously described elsewhere (Sahnoun et al.
Assays were performed after cooling for 2 h at room tem- 2013). Specific volume corresponded to the quotient of bread
perature. The TPA values expressed the averages of three volume (cm3)/bread weight (g). Improvement of bread loaf
different determinations. specific volume was calculated as follows:

Improvement ¼ ½1‐ðspecific volume of breadÞ=ðspecific volume of control sampleÞ  100

All determinations were performed in triplicates, and re- underwent a decrease in terms of reducing sugars content
sults were expressed as mean values. compared to the hydrolysed starch. This decrease could be
ascribed to the acetylation effect of starch free hydroxyl func-
Statistical analysis tions responsible to the reducing power.
The moisture contents of the acetylated and dual modified
For the statistical analysis, we applied the statistical package starches increased significantly (p < 0.05) compared to native
SPSS program (version 17). To ensure the equality of the starch (Table 2). This increase could be related to the percentage
variances, a Levene test was accomplished. The normal dis- of acetylation and presumably attributed to the introduction of
tribution was then checked by the P-Plot function. A one-way hydrophilic groups into the native starch. This result is in agree-
ANOVA test was performed to analyze differences between ment with previous reports on rice (Raina et al. 2006) and new
the means. The data were then submitted to a Duncan’s LSD cocoyam (Olayide 2004) starches. The increase recorded for the
test to evaluate the critical differences between the groups. moisture of starch samples treated with Aspergillus oryzae S2
Significance was set at (P < 0.05) in all cases. alpha amylase could be attributed to the release of hydrolysis
products with different degrees of polymerization, freer OH
groups, and higher water absorption capacity than native starch.
Result and discussion The dual modified starch exhibited a more pronounced mois-
ture content increase, which could be ascribed to the hydrophil-
Physiochemical properties of modified starch ic synergistic power given by each modification step.
A significant (p < 0.05) decrease in amylose content was
The results revealed that the degrees of substitution (DS) and observed for the starch treated by enzymatic hydrolysis
acetyl content (% AC) displayed for the dual modified starch (Table 2). This decrease was a normal consequence of α-
was higher than the acetylated one (Table 2). This increase in amylase hydrolysis of α-(1, 4) linkages inside the starch amy-
(% AC) and (DS) recorded for the hydrolysed acetylated lose and amylopectin polymers (Sahnoun et al. 2011). With 6 %
starch could be attributed to the increase of the free hydroxyl vinyl acetate, acetylation was noted to induce a marked decrease
groups likely to be involved in acetylation by the preliminary in amylose content (Table 2). This decrease was presumably due
alpha-amylase hydrolysis. Furthermore, the results presented to the disruption of intermolecular starch granules and helical
in Table 2 revealed that the hydrolysed acetylated starch structure of amylose. Similar results were previously reported

Table 2 Physicochemical characteristics of native, enzymatically hydrolysed, acetylated, and enzymatically hydrolysed and acetylated corn starch.
Data expressed as means ± SD. n = 3. Means followed by the same letter within column are non-significantly different (P < 0.05)

Starch sample Viscosity (Pa⋅s) Moisture (%) Amylose ReS (g/L)*10−2 Acetyl content (%) RS (%) DS*10−2
(g/100 g DM)

Native 1 ± 0.01a 13 ± 0.13a 26 ± 0.33c 0.21 ± 0.01a 0 ± 0a 1 ± 0.25a 0 ± 0a

Enzymatically hydrolysed 0.70 ± 0.04c 15.30 ± 0.14b 20.30 ± 0.24a 23.10 ± 0.20c 0 ± 0a 1.20 ± 0.21a 0 ± 0a
Acetylated 0. 30 ± 0.02b 17.50 ± 0.12c 21 ± 0.26b 0.18 ± 0.01a 1.83 ± 0.01b 12 ± 0.34b 7.00 ± 0.10b
Enzymatically hydrolysed 0.12 ± 0.02d 19.20 ± 0.13d 20 ± 0.37a 12.60 ± 0.30b 2.14 ± 0.01c 25 ± 0.28c 8.20 ± 0.10c
and acetylated

Superscripts letters were defined by Duncan’s multiple range test

DM: dry matter, ReS: reducing sugars content, RS: resistant starch content, DS: degree of substitution
 J Food Sci Technol

Fig. 2 water holding capacity of

native, enzymatically hydrolysed, k

acetylated, and enzymatically j

i i
hydrolysed acetylated corn starch
at 60, 70, 80 and 90 °C. Values gh
h
with the same letter are non- g
significantly different (P < 0.05) f
f
ef de
d c
b b
a

(Xie et al. 2005; Wickramasinghe et al. 2009) for acetyl concen- (Wickramasinghe et al. 2009; Mi et al. 2014). The increase
tration of 5 %. A controversial effect was, however, described in observed for the WHC values of the enzymatically hydrolysed
the work of Singh et al. (2004) which involved acetyl concen- starch could be ascribed to the generation of large amounts of
trations of less than 4 %. In fact, the substitution starts in the polysaccharides-reducing products having a better
more amorphous regions and proceeds to the more crystalline solubilisation and water absorption than the native starch
regions of the granule (Chen et al. 2005; Gray and BeMiller (Dura et al. 2014). The strong WHC recorded for the hydro-
2004; Huang et al. 2007). The decrease in the amylose content lysed acetylated starch at 90 °C was a novel attractive feature
for the case of the hydrolysed acetylated starch was the result of that supported its promising candidacy for potential application
a synergistic effect of the two modifications. in various food industries, including the confectionary industry.
The results recorded for the water holding capacity (WHC) The oil absorption capacity of the hydrolysed acetylated
of the native and modified starches heated at a temperature corn starch underwent a 2.3 fold improvement compared to
range of 60 to 90 °C are shown in Fig. 2. The findings revealed that of native starch (Fig. 3). This provided further support for
that the WHC values of the native and modified corn starches its promising candidacy for application as an alternative sub-
increased with the increase of temperature. In fact, at high tem- stitute to emulsifiers in the food industry. The improvement
peratures, the hydrogen bridges stabilizing the semi-crystalline observed in oil absorption could be due to the modification of
structure of starches are broken and replaced by water mole- the structural arrangement of starches following the fixing of
cules (Tester and Karkalas 1996). The hydrolysed acetylated acetyl groups and hydrolysis of the native starch, respectively.
starch displayed the highest WHC value. This could presum- In this context Konował et al. (2012) showed that the enzy-
ably be attributed to the modification effect. Certainly, acetyla- matically hydrolysed derivatives of acetylated potato starch
tion induced repulsion between the starch molecules by steric induced a reduction in the surface/interfacial tension of both
effects, thus facilitating the weakening of starch granules the air/water and toluene/water interfaces.
(Raina et al. 2006). Furthermore, the bulky acetyl groups could The results also revealed that the modified starches
have prevented the inter-chain association and improved the underwent a decrease in their final viscosity after cooling,
access of water to the amorphous area, thus enhancing the which was more pronounced for the enzymatically hydrolysed
leaching of amylose and the swelling and hydration of starch acetylated starch derivatives, followed by the acetylated and

Fig. 3 Oil absorption capacity of c

native, enzymatically hydrolysed,
acetylated, and enzymatically
hydrolysed acetylated corn starch.
Values with the same letter are
b
non-significantly different a
(P < 0.05) a
J Food Sci Technol

containing the desired amount of RS could be produced by

controlling the reaction time of the Aspergillus oryzae S2 α-
amylase hydrolysis. The increase observed for the resistance
to digestibility of the dual modified starch could be attributed
to the abundance of the bulky acetyl group attached to the C2
position in the glucose unit of starch. This particular attach-
ment was enhanced by the preliminary enzymatic hydrolysis
time, which reflected the exposure of starch C2-glucose free
site. In fact, this typical substitution would sterically hinder
the correct positioning of the dual modified starch into the
active site of α-amylase during its digestion treatment. It
Fig. 4 Kinetics of resistant starch formation as a function of the duration
of the preliminary enzymatically hydrolysis step of the dual modified would also hamper the proton donation from the catalytic
corn starch glutamic acid residue belonging to the amylase cleavage site
into the glycosidic bond oxygen during hydrolysis.
then the hydrolysed starches. The decrease in the viscosity of Furthermore, the powerful electron-withdrawing of the car-
corn acetate starch after cooling could presumably be attribut- bonyl oxygen of the acetyl group would result in the creation
ed to starch depolymerisation due to acetate mutual repulsion of a positive charge on C2. Thus, on the glucose unit, there
among polymer chains and decrease in their to water absorp- would be two electron deficient poles (positively charged C1
tion ability. Various studies have previously reported on a and C2) toward the nucleophilic carboxylate anion.
similar decrease in the viscosity of acetylated starch as com- Consequently, the α-retaining double dislocation hydrolysis
pared to native starch (Colussi et al. 2014; El Halal et al. mechanism that starts from the proton donation by glutamic
2015). The reduction observed for the viscosity of enzymati- acid to the glycosidic oxygen and from the carboxylate anion
cally hydrolysed starch after cooling could be ascribed to en- nucleophilic attack of aspartate on C1 (Coutinho and
zyme digestibility. In fact, the viscosity of starch after cooling Henrissat 1999) would take place more slowly.
was inversely related to the digestibility of enzymatically hy-
drolysed starches (Miao et al. 2014). Application and effect of modified starch on cake
The resistant starch content of the acetylated starch was properties
noted to increase by up to 12 %, reaching the desired range
for starch use on an industrial scale (Than et al. 2007). The Given their attractive properties and attributed, the modified
combination between enzymatic hydrolysis and acetylation starches presented in this work were assayed in the cake mak-
showed an increase in resistance to digestibility, reaching ing process at two concentrations, namely 5 %, and 10 %. The
67 % of resistant starch content after 1 h of preliminary hy- effects on the cake samples were compared to those of native
drolysis phase (Fig. 4). Accordingly, a tailored starchy food starch using the protocol described in the Materials and

Table 3 Effect of modified addition on textural properties, physical (5 % and 10 %) proportions. Data expressed as means ± SD. n = 3.
characteristic of cake prepared with native, enzymatically hydrolysed, Means followed by the same letter within column are non-significantly
acetylated and enzymatically hydrolysed and acetylated corn starch at different (P < 0.05)

Starch sample Hardness Cohesiveness Elasticity Adhesion Chewiness Firmness Volume Height
(N) (mm) (N) (Nmm) (N/mm) (cm3) (cm)

5%
Native 4.04 ± 0.05d 0.32 ± 0.02c 9.28 ± 0.08a 2.08 ± 0.08a 18.68 ± 0.09d 0.87 ± 0.02d 560 ± 2a 4.3 ± 0.1a
Enzymatically hydrolysed 2.58 ± 0.08b 0.26 ± 0.02b 10.58 ± 0.05b 1.37 ± 0.04b 13.29 ± 0.05c 0.68 ± 0.03c 592 ± 3b 5.8 ± 0.1b
Acetylated 3.23 ± 0.01c 0.25 ± 0.01b 10.88 ± 0.07c 1.27 ± 0.05b 11.98 ± 0.07b 0.62 ± 0.01b 598 ± 4c 6.4 ± 0.2c
Enzymatically hydrolysed 2.01 ± 0.07a 0.20 ± 0.01a 11.64 ± 0.05d 0.67 ± 0.09c 10.34 ± 0.07a 0.57 ± 0.01a 626 ± 2d 6.9 ± 0.2d
and acetylated
10 %
Native 7.63 ± 0.04d 0.41 ± 0.02d 8.09 ± 0.06a 2.43 ± 0.04d 24.53 ± 0.04d 1.17 ± 0.04c 530 ± 1a 3.7 ± 0.3a
Enzymatically hydrolysed 4.83 ± 0.03c 0.36 ± 0.01c 10.09 ± 0.05c 1.80 ± 0.03c 16.42 ± 0.09c 1.01 ± 0.01b 571 ± 1b 5.1 ± 0.1b
Acetylated 4.34 ± 0.03b 0.32 ± 0.02b 9.89 ± 0.03b 1.66 ± 0.03b 15.55 ± 0.04b 0.96 ± 0.02b 577 ± 2c 5.8 ± 0.1c
Enzymatically hydrolysed 4.23 ± 0.08a 0.29 ± 0.01a 10.22 ± 0.07d 1.53 ± 0.05a 14.31 ± 0.03a 0.86 ± 0.03a 581 ± 1d 5.6 ± 0.1c
and acetylated

Superscripts letters were defined by Duncan’s multiple range test

 J Food Sci Technol

10% 5%
5% 10%
5% 5%
10%
10%

a b c d
Fig. 5 Cake prepared with a native, b enzymatically hydrolysed c, acetylated, and d enzymatically hydrolysed acetylated corn starches at 5 % and 10 %
concentrations

Methods section. The effects of the different starch composi- amylase breaks down starch into lower molecular weight dex-
tions on the textural parameters of wheat flour cake are pre- trins and polysaccharides with lower cohesive forces than am-
sented in Table 3. The results revealed that the application of ylose and amylopectin constituent chains (Grabowski et al.
the modified starches at a concentration of 5 % induced a 2006). The decrease in the cohesion of the cake samples
decrease in the hardness, chewiness, cohesion, and adhesion cooked with acetylated starch was presumably due to the sub-
of the baked cakes (Table 3). This decrease was more pro- stituent effect which reduced the interaction between starch
nounced for the cake incorporating hydrolysed acetylated, molecules and, hence, induced swelling power
acetylated, and hydrolysed starches, respectively. (Wickramasinghe et al. 2009).
The decrease observed in the hardness of the modified The results also revealed a decrease in the adhesion of the
starches is consistent with the results previously reported by cake samples containing hydrolysed starch. This decrease
Khalil et al. (2001) who found a significant and negative cor- could be ascribed to a reduction in the polysaccharide external
relation between the moisture and water retention power of interaction chains due to high water-holding and moisture. In
starch and the hardness of the cooked product. The decrease in fact, water interferes in the formation of gluten-starch com-
cohesion is generally related to the loss of intramolecular in- plexes of wheat flour, which are responsible for main-
teraction ingredients. The reduction recorded for the cohesion taining crumb adhesion and hardening. This may happen
of the cake baked with hydrolysed starch was expected since in analogy to emulsifiers that fix to protein with their

Fig. 6 Aspects of crumb

prepared with native (a),
enzymatically hydrolysed (b),
acetylated (c), and enzymatically
hydrolysed acetylated (d) corn
starches at a concentration of 5 %
J Food Sci Technol

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