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Abstract

Digestible glycemic carbohydrates are an important energy source to support the rapid growth and development of young children. The aim of this comprehensive review is to present up-to-date knowledge of starch digestion in the young child. Starchy foods are consumed uncooked (e.g., fruit or vegetable salad) or cooked (e.g., mashed potato), and in granule (insoluble) or gelatinized (soluble) forms. Various aspects of digestive enzymes in the young child are described, including pancreatic α-amylase deficiency and the existence of salivary α-amylase, milk α-amylase, blood α-amylase, and α-glucosidases. The young child can digest starchy foods and absorb dietary glucose. Among the various sources of starches, rice maltodextrin is most digestible because of its unique structural characteristics. Common sources of complementary starches are also described. This review would benefit the food industry in designing complementary foods (also known as beikost), and also health providers, such as pediatricians and dietitians in understanding starch digestion and the difference between granule and gelatinized starch.
REVIEW
The digestion of complementary feeding starches in the young
child
Amy H.-M. Lin
1,2
and Buford L. Nichols
3
1
Bi-State School of Food Science, University of Idaho, Moscow, ID 83844, USA
2
Washington State University, Pullman, WA 99164, USA
3
USDA-ARS Childrens Nutrition Research Center, Baylor College of Medicine, Texas Childrens Hospital, Houston, TX 77030, USA
Digestible glycemiccarbohydrates are an important energy source to support the rapid growth and
development of young children. The aim of this comprehensive review is to present up-to-date
knowledge of starch digestion in the young child. Starchy foods are consumed uncooked (e.g., fruit
or vegetable salad)or cooked (e.g., mashed potato),and in granule (insoluble) or gelatinized(soluble)
forms. Various aspects of digestive enzymes in the young child are described, including pancreatic
a-amylase deciency and the existence of salivary a-amylase, milk a-amylase, blooda-amylase, and
a-glucosidases. The young child can digest starchy foods and absorb dietary glucose. Among the
various sources of starches, rice maltodextrin is most digestible because of its unique structural
characteristics. Common sources ofcomplementary starches are also described. This review would
benet the foodindustry in designing complementary foods (also knownas beikost), and also health
providers, such as pediatricians and dietitians in understanding starch digestion and the difference
between granuley and gelatinized starch.
Received: January 11, 2017
Revised: April 30, 2017
Accepted: May 29, 2017
Keywords:
a-amylase / a-glucosidase / Beikost / Starch digestion / Young children
1 Introduction
For human infants, supplementation of maternal nursing is
called complementary feeding, and the German term, Beikost,
refers to infant foods other than milk or formula. The
introduction of Beikost begins the weaning process, and starchy
foods, especially those of cereal-based, are the rst offered in
most cultures. Currently, the recommended age for introducing
complementary feeding is 6 months; one of the reasons for this
recommendation is the physiologic delay of pancreatic a-
amylaseproductionandsecretioninnormalinfants[1].Thereis
little evidence that human infants can digest complementary
starchy foods at birth. An argument also exists as to the need for
glycemic carbohydrates in humans, including infants or adults.
Studies have shown that starches are digestible in infants, and
glucans (products of starch digestion) are more easily absorbed
than simple sugars (i.e., glucose) [2, 3]. Some studies have shown
that complementary feedings enhance energy intakes and
growth, even in premature infants [47]. Another benetof
feeding complementary starchy foods is to facilitate microbiome
development by which the indigestible portion of starch is used.
In the past decade, several noninvasive techniques, such as
breath test and
13
C-labeling, were developed to examine starch
digestion and fermentation in infants [8]. Digestion is an
enzymatic reaction, and the understanding of starch digestion
has gone beyond a-amylolysis. We have previously revealed the
high digestion capability and specicity of a-glucosidase at the
brush border area in the small intestine [9, 10]. The purpose of
this review is to summarize up-to-date knowledge of starch
digestionintheyoungchildthatwillbenet the food industry in
designing complementary starchy foods, and also health
providers, such as pediatricians and dietitians in understanding
starch digestion and the difference between granule and
gelatinized starch.
2 Starch and starch digestion
Higher plants, such as corn, rice, and potato, store energy
predominantly as starch. Starch and the products derived
Correspondence: Amy Hui-Mei Lin, Bi-State School of Food
Science, University of Idaho, 875 Perimeter Dr. MS2312,
Moscow, Idaho 838433-2312, USA
E-mail: amylin@uidaho.edu
Fax:þ1-208-885-2567
DOI 10.1002/star.201700012Starch/Stärke 2017, 69, 1700012 1700012 (1 of 10)
www.starch-journal.comß2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
from starch, such as maltodextrin, are major digestible
complex carbohydrates in human diets. Most of the starches
for human diets are in grains (or our its processed form)
and vegetables. As humans are the only species to use re,
many starchy foods areconsumed after cooking that gelatinizes
starches. Cooking introduces dramatic changes in the starch
granule structure, molecular properties, and the interaction
between starches and other food components (e.g., lipid and
protein). Thus, the nutritional value of starch is altered.
Starch naturally exists as granules with a semi-crystalline
structure. In most cooking processes, heat and water are
applied to initiate the gelatinization process. Starch granules
absorb water and swell, followed by molecular leaching and
granule breaking. During heating, starch granules gradually
loosen their highly organized structure with the disappear-
ance of birefringence and the Maltese cross. Granule starch
is not soluble in cold water, but gelatinized starch is viscous
and often forms paste or gel. Granule starch and gelatinized
starch interact very differently with other food components
or enzymes. For granule starch, the interaction occurs on the
granule surface or in the pores and channels inside the
granules. Gelatinized starch molecules are more susceptible
to enzymes, and the interaction with enzymes is highly
associated with the number of branches and the length of
molecular chains.
2.1 Digestion of granule starch
2.1.1 The influence of granule size and surface area
on granule starch digestion
Granule starches are mostly present in uncooked vegetable
(e.g., salad) and fruits. Some foods prepared with a low
degree of heating and moisture (e.g., biscuits) also contain
granule starches. The digestibility of granule starches is
related to their structural characteristics, such as size, shape,
number of pores, and channels, types of polymorph,
heterogeneity of granules, and the micro-environment in
plant tissues. The digestion process includes the diffusion of
enzymes to the starch granule surface, followed by
adsorption and catalytic cleavage. The area of granule
surface inuences the rate of enzymatic hydrolysis [11].
Therefore, small granules with a relatively large surface area
per unit weight are more susceptible to enzymatic digestion
[1214]. It has been reported that enzyme hydrolysis rate,
coefcient K, was inverse correlated to the size of a specic
surface area [11], but the Michaelis constant Km values of
various granule starches (e.g., maize, rice, and potato), when
expressed as a function of surface area, were similar [15].
Kim et al. reported the Vmax values attributed to the
deviation from the real value of a specic surface area, vary
among different starches, and this deviation leads to the
difference in the initial hydrolysis rate of various starches
[15]. The relationship between granule size and enzyme
hydrolysis has been investigated in various enzymes,
including a-amylase, amyloglucosidase, b-amylase, and
pullulanase in vitro and in vivo systems [1113, 1618].
The correlation, however, between granule size and
hydrolysis rate only exist in granule starches but not
gelatinized starch molecules [12]. In some plants, such as
wheat, rye, and barley, the size of starch granules has a bi-
model distribution. Wheat starches are classied into A and
B types according to their granule size. Wheat A-type starch
is large with a lenticular shape, and the diameter of granules
is about 1050 mm. Wheat B-type starch is relatively small
with a sphere shape, and the diameter is smaller than 9 mm.
Wheat A- and B-starches also differ in molecular structure
and chemical and physical properties, which leads to the
difference in their hydrolysis rate in addition to the inuence
from their granule size [19].
2.1.2 The influence of pores and channels on granule
starch digestion
Many starches have pores on the surface and channels inside
the granules that allow other molecules, such as enzymes, to
enter the granules. BeMiller et al. [10] used several
microscopic techniques to show the existence of pores
and channels in starch granules, and hypothesized that the
enzyme hydrolysis is inside-out.In this theory, enzymes
slowly penetrate from the external surface into a cavity at the
hilum, which is less organized than other areas in a granule,
and then quickly hydrolyze starch molecules from the hilum
area toward the surface of granules [2023]. The formation of
pores and channels is unclear, but it is a characteristic unique
to each starch from different sources. Some starches, for
example, potato, do not have visible pores and channels, and
those with pores and channels have unique patterns of pores
[2023]. For example, the wheat A-type starch has a high
number of pores distributed in the grove area of the
lenticular-shaped granules. Normal maize (amylose content
26%) and waxy maize starches have pores that are
randomly distributed on the surface. Starches without pores
and channels are more resistant to digestion or modication.
In normal maize starch, pinholes are enlarged by enzymes
and become large round shaped holes. Lotus rhizome starch,
with an elongated oval shape, is always attacked by a-amylase
from a particular end of the starch granules, and the other
end of the granule remains intact [24]. Pores and channels
are weak or vulnerable locations for enzymatic hydrolysis in
granules [25].
2.1.3 The influence of heterogeneity of molecular
organization and polymorphic types on granule starch
digestion
The heterogeneous granule structure and polymorphic types
(crystalline type) are other key characteristics associated with
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granule digestion. Starches are classied into A, B, and C
polymorphic types according to their X-ray diffraction
patterns [26]. This classication is different from that of A
and B granules of wheat, barley, and rye starches. The type of
polymorph is related to the arrangement patterns of the
double helices in the crystalline lamellae. The C-polymorphic
type is a mixture of A- and B-polymorphic types. Using
confocal laser-scattering microscopy (CLSM), Jane et al.
found a substantial amount of voids in A-polymorphic type
starches (e.g., Sugary-2, normal maize, and waxy maize) but
not in solid structures in B-polymorphic type starches (e.g.,
potato, high-amylose maize, and green banana) [27, 28]. The
voids are loosely packed areas and are the sites vulnerable to
enzyme digestion. The void areas in lotus rhizome starch are
near the granule end, which is the same end attacked by a-
amylase [24]. Additional evidence regarding the heteroge-
neous granule structure was obtained by the salt-peeling
gelatinization technique, in which saturated salt solution is
used to gelatinize and remove the starch surface. With this
technique, the granules of normal maize starch (A-
polymorphic type) exhibit ssures, pens, and loosely packed
structures, while those of potato starch (B-polymorphic type)
show a solid structure [27].
The polymorphic type has a strong correlation with
granule starch digestibility. A-type starch has a large
population of short chains (A and B1 Chains), which are
less stable and more susceptible to rearrangement; they also
generate more loosely packed areas of voids. B-type granules
contain more long chains, and the double helices of their B-
chains are aligned in more orderly fashion in the granules,
contributing to a solid granule structure and higher
resistance to digestive enzymes [27]. A-type granules usually
have more openings on the surface, whereas B-type granules
(e.g., potato) seldom have visible pores or channels. Overall,
A-type polymorphic granules are more susceptible to
digestive enzymes [29], but this property disappears after
cooking.
2.1.4 The influence of non-starch components on
starch digestion
In addition to granule structure, the micro-environment in
plant tissues, especially the interaction between starch
granules and other macro-molecules, also plays an important
role in starch digestion. Sorghum is known for its low
digestibility. The hard peripheral endosperm layer in
sorghum kernels is largely responsible for their resistance
to digestive enzymes, and the presence of protein bodies
around sorghum starch granules provides a rigid cover and
barrier to digestive enzymes [30]. After cooking, the protein
interacts with starch in the matrix and restricts the digestion
[30]. Furthermore, the phenolic compounds such as tannins
existing naturally in sorghum, function as inhibitors of
digestive enzymes leading to low digestibility [31]. Potato
starch granules are surrounded by cell walls, and the glycan
composition of cell walls is associated with the strength of
the walls and inuences the accessibility of starches to
digestive enzymes [32]. Enzyme inhibitors, such as calyste-
gine a low toxic glycoalkaloid, are also present in potatoes
[33]. Thus, non-starch molecules in plant tissues or food
systems also inuence starch digestion and glucose
generation. In addition, processing techniques can affect
the degree of gelatinization and the interaction between
starch and other molecules.
2.2 Digestion of gelatinized starch
2.2.1 The influence of amylose on gelatinized starch
digestion
Most starchy foods are consumed after cooking, and gelati-
nized starch digestibility is determinedby molecular structure,
rather than granular structure. In general, a high amount of
amylose is correctedwith low digestibility. Amylosehas a lower
number of branches [a-(1 !6)-glycosidic linkage, approxi-
mately 2%] than amylopectin (approximately 5%). With fewer
branches, the long linear molecular chains can associate
(retrograde) with another linear chain to form a double helical
structure, which has a low susceptibility to digestive enzymes.
Furthermore, the helical structure, with a hydrophobic cavity,
can form a complex with other hydrophobic compounds, such
as a lipid. When amylose and lipid form a complex on the
surface, it restricts granule swelling and increases the
difculty of fully gelatinizing the starch; after gelatinization,
the complex has a lower susceptibility to digestive enzymes.
Not all the studies completely agree with the inverse
correlation between amylose content and digestibility. For
example, rice varieties with similar high-amylose contents can
have different starch digestibility because their gelatinization
condition varies [34]. The nature of amylose structure, such as
chain-length, branch pattern, and its interaction with
amylopectin, also affects starch digestion.
2.2.2 The influence of amylopectin on gelatinized
starch digestion
Amylopectin has a higher number of a-(1 !6)-glycosidic
linkages, but the majority of digestive enzymes (e.g., a-
amylase) only hydrolyze a-(1 !4)-glycosidic linkages. Thus,
a higher number of a-(1 !6)- linkages (i.e., branches) is
associated with a low or slow digestibility. Also, a high
number of a-(1 !6)- linkages results in short chain-length,
which is less susceptible to a-amylase, compared with
molecules with long chain-length. The digestibility of
starches also varies with different processing stages: granule
(before cooking), gelatinized (soon after cooking), and
retrograde (cooling after cooking). When molecule chains
are long enough to form a stable retrogradation during
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cooling, long-chain amylopectin generates a strong associ-
ation between chains, resulting in low digestibility. This
type of molecular association may be changed during
cooking because the melting temperature of this type of
retrogradation is lower than 100°C. Amylopectin retrogra-
dation is more complicated than that of amylose. In
addition to chain-length, the ratio of long-chain to short-
chain molecules affects the strength of retrogradation and
further inuences digestion. Amylopectin can also be
associated with amylose molecules to form a different type
of retrogradation. In addition to the amount of a-(1 !6)-
linkages and chain-length, we have shown that the branch
pattern of the internal amylopectin chains strongly
inuences digestion, especially the glucogenesis by muco-
sal a-glucosidase [35]. When starch molecules are hydro-
lyzed by mammalian a-amylase, a large portion of the
internal amylopectin molecules are protected by branches
and escape from a-amylase hydrolysis. Their susceptibility
to mucosal a-glucosidase is determined by the branch
pattern, that is, the abundance of branches and the distance
between branches.
2.2.3 The influence of incomplete gelatinization on
starch digestion
Cooking transforms starch from granule to a dispersed
molecular form, which is more susceptible to digestive
enzymes than granule form. Starchy foods, however, are not
always fully gelatinized due to insufcient heat and moisture
or changes in structure during processing (e.g., annealing).
Gidley et al. reported that starch ghost, a fragment of granule
structure generated by an incomplete gelatinization at a low
sharing condition, is composed of entangled amylopectin
and some amylose. Such highly branched and large
amylopectin size is resistant to digestion [36].
3 Starch digestive enzymes in the young child
3.1 a-Amylases
Six digestive enzymes are required to break down starch
molecules to absorbable glucose; included two a-amylases
(salivary and pancreatic) and four mucosal a-glucosidase:
N- and C-terminal subunits of maltase-glucoamylase
(MGAM) and sucrase-isomaltase (SI). a-Amylase was
referred to as diastase by Leuchs in 1831 [37], and Kuhn in
1925, renamed it as a-amylase because its endo-amylolytic
products have an a-conguration [38]. Salivary glands and
the pancreas are the two major sources of human
amylases. Multiple isozymes are present in various body
uids such as, plasma and urine. Human a-amylases are
the products of two genes, Amy
1
(salivary-type amylase)
and Amy
2
(pancreatic-type amylase) [3941]. Salivary and
pancreatic a-amylases have a similarity of 95% in amino
acid sequences [42]. a-Amylase can hydrolyze the internal
a-(1 !4)-glycoside linkages in large polymers, such as
starch, glycogen, and dextrin, and the products of a
complete hydrolysis are maltose, maltotriose, and some
branched dextrins [43]. Though salivary and pancreatic a-
amylase have similar amino acid sequences, salivary a-
amylase has a higher specic activity on soluble starch
(gelatinized starch) than pancreatic a-amylase [44, 45]. By
contrast, pancreatic a-amylase has a higher activity on
insoluble starch (granule starch) [44, 45]. Also, salivary a-
amylase can be adsorbed on tooth surface and has a
different hydrolytic pattern from the a-amylase dispersed
in the lumen [46]. Pancreatic a-amylase has been studied
extensively, although it contributes only approximately
30% of the a-amylase activity in humans [47]. It is unclear
how much the salivary a-amylase contributes to the total
starch digestion because gastric acid can inactivate salivary
a-amylase. Salivary a-amylase is re-activated in the
duodenal lumen, as it has an alkaline environment [48].
Blood is another known uid that contains amylase,
probably a result of endocrinesecretion of exocrine
digestiveglands[49].Thetotala-amylolytic activity in the
blood is the sum of activities of several a-amylases of
diverse origins such as salivary glands, pancreas, and liver.
a-Amylases respond quickly and transiently to a variety of
substances (e.g., glucose, fructose, and insulin) and
hormones [49]. Human milk is another important source
of a-amylase in the young child and will be discussed later.
3.1.1 Pancreatic a-amylase
Physicians have long recognized the inability of young
children to digest starch [50] due to the delay in amylase
production and secretion in normal infants under 6
months of age [5053]. The activity of pancreatic
a-amylase at birth is about 3% of that of adult levels,
begins to increase at 78 months, and reaches adult levels
by 5 years [54]. However, Auricchio et al. claimed that the
pancreases of full-term infants have amylase activity
equal to one-tenth of adult levels and suggested that
amylase is produced but is not completely secreted in
infants [55, 56]. In contrast, Track et al. found no amylase
in the pancreatic tissues of fetuses and infants up to
3 wk of age [56, 57]. Another reason for introducing
complementary starch feedings at 6 months is the
inuence of diets, especially starchy diets, on the
exocrine function of the pancreas. It has been shown
that early administration of small amounts of starch after
birth stimulated pancreatic a-amylase production [51].
Also, the rate of a-amylase secretion is determined by the
rate of carbohydrate metabolism and is sensitive to
nutrient intake [58, 59]. Nevertheless, it is unclear if the
delay in pancreatic a-amylase synthesis and secretion is
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the result of delaying complementary feeding of starchy
foods.
3.1.2 Salivary a-amylase
Salivary a-amylase is an important enzyme because it is
synthesized and fully secreted in infants [56]. The activity is
detectable from about 20 wk of gestation and reaches that of
adult levels 3 months after birth [60, 61]. It is a concern, as
mentioned earlier, that salivary a-amylase is inactivated in
the stomach. Rosenblum et al. reported that starch can
protect salivary a-amylase from being inactivated in an
acidic environment [52]. Their data showed that salivary a-
amylase is 56% active at pH 3 in the presence of 1% starch
after 60 min at 37°C. Some sugars, such as high concen-
trations of glucose, maltose, and sucrose, are also
protective. The possible mechanism of such protection is
that starch binds to the active site of salivary a-amylase and
slows the rate of inactivation by acids. Glucose and sucrose
have been shown to protect the catalytic activity of a-
amylase [62].
3.1.3 Milk a-amylase
Milk a-amylase is unique to humans, whereas a-amylase is
not found in the milk of cow, sheep, goat, or swine [63]. Milk
a-amylase has ve isozymes; three of them are the salivary
type, and two of them are different from either salivary or
pancreatic type [6467]. The levels of milk a-amylase are
high when those of other a-amylases in saliva and duodenal
juice are low [68]. Milk a-amylase is not destroyed in the
stomach as the pH is raised sharply after a meal of human
milk and remains between 5.2 and 6.4 for as long as
120 min after th e mea l [69] . It is conceivable that milk a-
amylase is an important enzyme for starch digestion in
infants.
3.1.4 Blood a-amylase
Blood amylase activity is stable in infants; there are no
signicant changes from one to 180 days after birth [70].
When feeding infants with starches (e.g., rice, corn, and
potato starch), blood amylase activity decreases, and blood
glucose concentration increases [70]. This nding sup-
ports the view that there are no adverse effects in feeding
young children starches. a-Amylase activity is also present
in human serum. There are three major amylase
isoenzymes in serum, one originating from the pancreas
and two from the salivary glands. The activity of salivary-
like a-amylase is 32% of adult levels at birth, begins to
increase by 34 months, and reaches adult levels by
19 months [54]. Bossuyt et al. reported that the presence of
a-amylase isozymes in human serum is affected by age,
but the total activity of a-amylase is not age-related. The
fraction of pancreatic type amylase in serum is gradually
increased in children until the levels reach those of adults
(1015 years of age). After age 40, the contribution of
pancreatic type a-amylase to the total amylase activity in
serum decreases rather rapidly [71]. After the age of 65, the
pancreatic-fraction of amylase activity is as low as that of
young children.
3.2 Mucosal a-glucosidase
a-Amylase activity is low in young children, and though not
recommended, this should not preclude feeding them
starchy foods; mucosal a-glucosidase activity is well-
developed even in newborn infants. Both maltase-gluco-
amylase (MGAM) and sucrase-isomaltase (SI) are present in
human fetuses during the rst trimester of gestation, and
their activities increase rapidly, reaching full-term levels as
early as 1016 wk of gestation [7274]. The sucrase and
maltase activities approach 70% of full-term levels by 24
26 wk of gestation, reach adult levels at birth, and remain
relatively constant after birth [75]. Infants of other mammals,
such as rat, calf, pig, lamb, horse, and rabbit, do not have
signicant a-glucosidase activity levels until the end of the
weaning period [7680]. Among the four a-glucosidases, Nt-
MGAM (also known as Maltase II and maltase) and Ct-
MGAM (also known as Maltase III and glucoamylase) are
developed only during the last trimester of gestation in
humans. Ct-MGAM is the last a-glucosidase to develop and
is developed fully only after birth [74, 81]. We have reported
that a-glucosidase is also present in milk, and enables
suckling mouse pups to digest starch [82]. Whether human
milk also has a-glucosidase activity is unknown. We
hypothesized that the a-glucosidase plays an important
role in infants because of its ability to digest starch
molecules and its synergistic relationship with a-amylase
[83]. a-Glucosidases are known to carry maltase activity and
quickly convert a-amylase hydrolysates to glucose. Nt-SI
(also known as isomaltase) and Ct-SI (also known as
sucrase) can also digest branched glucans and sucrose,
respectively.Wehaveshownthata-glucosidase can directly
digest large glucans, such as starch molecules, to glucose,
and that Ct-MGAM alone can quickly release approximately
80% of glucose from gelatinized starch [9, 8487]. Each of
the a-glucosidases has special preference in substrate
structure and digests starch molecules or a-amylase
hydrolysates differently [10]. We have also reported that
a-glucosidase amplied a-amylase hydrolysis and synergis-
tically digested starch to glucose [86, 88]. With insufcient
a-amylase activity in young children, the existence of a-
glucosidase becomes very benecial, because it may also
enhance milk and salivary a-amylase hydrolysis and
synergistically digest starch to glucose.
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4 Starch digestion in the young child
There is a gap in energy supply when there is insufcient
breast milk to support the growth of infants. Although an
adult level of mucosal a-glucosidase is present, the
complementary feeding of starch is a dilemma, because
of the concern over insufcient pancreatic a-amylase
activity. Auricchio et al. measured the total glucosidase
activity in the lumen and calculated that the infant intestine
can digest 107 g maltose, 72 g sucrose, 46 g isomaltose, and
60 g lactose in 24 h [55]. Newborn infants, 460 days of age,
are able to digest thin boiled starch of white waxy sorghum,
slowly and sustainably raising their blood glucose levels
over a period of 21
/
2h [89]. Infants with low birth weight are
also capable of digesting pre-gelatinized corn starch as part
of a formula, 3.55 g/kg bo dy weight/day; feeding them a
small amount of starch signicantly increases their body
weight [90]. Infants younger than 6 months can digest a
portion of amylopectin that is dissolved in cold water, but a
large amount of dextrin with a size more than 30 glucosyl
units is defecated [91]. When feeding meals of cooked rice
and corn, 47 month-old infants can completely digest
them [92]. At the end of the rst year, infants can rapidly
digest amylopectin to glucose, maltose, maltotriose, and
branched dextrins [91], and 12 year-old children can
efciently digest cooked rice and corn [92]. Though infants
can digest starch, starch overload may result in diarrhea. De
Vizia et al. reported that 1-month-old infants can digest
cooked starches as part of a formula of 110 g/m
2
of body
surface per day without diarrhea [90]. After the rst year,
children can absorb almost completely 170 g/m
2
/day of
cooked starch in the form of biscuit or macaroni [90].
Starches from different plant sources are all well
digested by 13 month-old infants. De Vizia et al. cooked
wheat, tapioca, corn, rice, and potato for 10 min in water
and used the starch solutions to dilute cowsmilk.When
fed to the infants in the study, all milks were well-digested.
and fecal excretion of glucose, dextrin, and starch was low
[90]. Potato, however, in the form of biscuit, was less-well
digested in 1-year old children than was wheat in the
forms of biscuit and macaroni [90]. Potato starch is likely
less-well gelatinized in the form of biscuit and maintains
its granule structure, which is more resistant to digestive
enzymes. Starch, after digestion, is better absorbed and
raises blood-glucose sustainably when part of a formula,
compared with the starch solution without other ingre-
dients [93]. Most of the studies discussed above, except
those feeding water soluble amylopectin [91], fed young
children with starch solutions or starchy foods as part of a
formula.
Some researchers raised the concern of incomplete
digestion of starch and amylopectin [89] and suggested that
maltodextrin, a partially hydrolyzed starch product, is a better
choice for infants [94]. Both maltodextrin and maltose can
raise blood glucose concentration in 3-day-old infants [93]. In
addition, glucans (e.g. maltodextrin) are better absorbed than
simple sugars (e.g., glucose) [2, 3]. Glucans are also well-
tolerated in preterm and term neonates and empty from the
stomach quickly [47]. When starch or starch hydrolytic
products from different botanical sources are compared, rice
maltodextrin is found to be digested faster and increases
serum glucose concentration more rapidly than corn
maltodextrin [95]. Rice-based solution for oral rehydration is
also well-tolerated by infants and children with acute diarrhea
[96]. An advantage of rice maltodextrin is the generation of
more short-chain glucans (about 70% of which have a size
smaller than seven glucosylunits) [95] that can be digested and
absorbed faster than glucans with longer chains [2, 3].
5 What complex glycemic carbohydrates
do we feed the young child?
The EU Directive 2006/141/EC of December 22, 2006 and
the amended Directive 1999/21/EC on infant formulae have
established compositional criteria for dietary carbohydrates
(http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELE
X:32006L0141, achieve at https://perma.cc/CX2H-MTPW).
Infant for mula shall have a minimum of 9 g of tota l
carbohydrates/100 kcal and a maximum of 14 g/100 kcal.
Lactose, maltose, sucrose, glucose, maltodextrin, glucose
syrup or dried glucose syrup, precooked starch, and
gelatinized starch can be used in infant formula. Some
modied starch, such as octenyl succinic acid (OSA)
modied starch, is also allowed. (http://apps.who.int/
food-additives-contaminants-jecfa-database/chemical.aspx?
chemID = 340, achieved at https://perma.cc/QV2V-ZB9D)
The maximum amount of precooked and gelatinized starch
is 2 g/100 mL [97]. There have been few r eports about the
sources of starches or starch hydrolysates (e.g., maltodex-
trin) introduced to young children. In general, rice is
consumed in the greatest quantities in Asia and Africa, and
wheat is the main source of carbohydrates in the Western
world. Other cereals that are also important, but less
popular, include rye, barley, oat, and millet [98]. Cereal
products, 23% of the total carbohydrate intake, are the major
starch source of infants aged 612 months in the survey of
488 British infants [97, 99]. Cereal and cereal products
represent 40% of total carbohydrate intake for toddlers
(1.53 years) in the United Kingdom, and pasta, rice, and
miscellaneous cerealsand white bread are the largest
contributors of starch, both at 9% of total carbohydrate
intake [97, 100]. Grain products are the major source of
starch for toddlers in the United States, at least 27% of the
total carbohydrate intake, according to the US Feeding
Infants and Toddlers Study (FITS) of 2002 [100]. Among the
grains, infant cereals made of rice or oat, baby nger foods
made of rice, corn, and wheat are common [101]. Some
1700012 (6 of 10) A. H.-M. Lin and B. L. Nichols Starch/Stärke 2017, 69, 1700012
ß2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.com
starches are consumed in cooked forms, such as sweet
potatoes, potatoes, squash, mixed garden vegetables, peas,
and pea mixtures [101]. Some starches are consumed in
granule form, especially fruits and those of uncooked salad,
such as carrots and apples [101].
6 The future
The early years of life are a period of very rapid growth and
require sufcient energy and nutrients. The brain is especially
demanding of energy, and consumes approximately 60% of
dietary energy intakeduring infancy [97, 102, 103]. The brain is
also sensitive to changes in the supply of dietary glucose,
uctuations in metabolism, and long-term nutrition status
[97]. Digestibleglycemic carbohydratesare the main sources of
energy in this crucial period. The quality of starch digestion is
determined not only by the amount of glucose produced, but
also by the quantity of absorbable glucose. Glucose is not the
only outcome of the digestion, but also a substance that can
facilitate the synthesis and secretion of pancreatic a-amylase.
Each starch is unique in its granulearchitecture and molecular
structure. Thus, the production of glucose from various
starches is different on the basis of their interactions with
digestive enzymesand the micro-environment. Infant foodis a
growing market, but there is a need for additional research to
aid in a better understandingof starch digestion. Only then can
ideal diets for infants be designed.
The authors thank Roseland Klein (Retired assistant professor,
USDA-ARS Childrens Nutrition Research Center and Depart-
ment of Pediatrics, Baylor Collegeof Medicine, Houston, TX, USA)
and Chao-Hung Lee (Professor, Department of Pathology and
Laboratory Medicine, Indiana University School of Medicine,
Indianapolis, IN, USA) for editing the manuscript. Note: Several
typographical corrections were made and the ZIP codes added to
the afliations on July 3, 2017, after initial publication online.
The authors have declared no conicts of interest.
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... Feeding young children starchy foods can create a dilemma, because the children lack sufficient pancreatic a-amylase, the major digestive enzyme that breaks down starch molecules from half a million to 2 to 3 glucosyl units. Young children, however, do have a-glucosidase in amount and activity similar to that in adults; further, a-glucosidase can digest starch to dietary glucose (5). Clinical studies have shown that young children can digest amylopectin and cooked starchy foods (5). ...
... Young children, however, do have a-glucosidase in amount and activity similar to that in adults; further, a-glucosidase can digest starch to dietary glucose (5). Clinical studies have shown that young children can digest amylopectin and cooked starchy foods (5). Maltodextrin, the product of partial hydrolysis of starch, can also be digested by young children (5). ...
... Clinical studies have shown that young children can digest amylopectin and cooked starchy foods (5). Maltodextrin, the product of partial hydrolysis of starch, can also be digested by young children (5). Starch is also used in some clinical applications, that is, ricebased solutions to treat acute diarrhea and oral dehydration. ...
Article
Starch is the major source of dietary glucose for rapid development of children. Starches from various crops naturally differ in molecular structures and properties. Cooking, processing, and storage may change their molecular properties and affect their digestibility and functionality. Starch digestion is affected by its susceptibility to α-amylase and α-glucosidase (maltase), and the susceptibility is determined by starch granule architecture and glucan structures, as well as the interaction between starch and other food components. Starch is given as a complementary feeding to young children in many cultures, and starch or modified starch, is used in special formulae of infant foods or supplements. Although indigestible starch does not provide much energy, it can benefit colonic health.
... Early weaning could be considered to have a positive impact if it was done fulfilled consents and agreement to do so by both of the parents and whole families, even though other experts explained it might not beneficial for the growth and development. Child who was early weaned might not be ready for complementary foods [16,17], and if it was done without the mother's consent, it might leads to mother's unpreparedness to give complementary foods [18]. Negative impact to the child, mother, and whole families might be occurred at not only early age of weaning, but also at prolonged breastfeeding or late age of weaning. ...
... This test helps in the classification of starch into rapidly digestible, slowly digestible, and RS. The results obtained after conducting the study show that amylose content can be related to the glycaemic index of rice, thus making it a simple application in growing of agricultural crops and related industries (Lin & Nichols, 2017). ...
Article
Starch granules from rice and corn were isolated, and their molecular mechanism on interaction with α‐amylase was characterized through biochemical test, microscopic imaging, and spectroscopic measurements. The micro‐scale structure of starch granules were observed under an optical microscope and their average size was in the range 1–100 μm. The surface topological structures of starch with micro‐holes due to the effect of α‐ amylase were also visualized under scanning electron microscope. The crystallinity was confirmed by X‐ray diffraction patterns as well as second‐harmonic generation microscopy. The change in chemical bonds before and after hydrolysis of the starch granules by α‐ amylase was determined by Fourier transform infrared spectroscopy. Combination of microscopy and spectroscopy techniques relates structural and chemical features that explain starch enzymatic hydrolysis which will provide a valid basis for future studies in food science and insights into the energy transformation dynamics. Determine the changes in micro‐scale structure of starch granules (rice and corn) before and after hydrolysis using optical microscope and scanning electron microscope. Investigate the starch crystallinity using X‐ray diffraction spectroscopy and second‐harmonic generation microscopy.
... There are two facts that contradict the old belief that infants are not able to digest starch. Firstly, other enzymes such as glucoamylase-maltase and salivary α-amylase make up for the physiological lower activity of pancreatic α-amylase [155][156][157][158]. Secondly, infants have a higher capacity to ferment the non-digested starch (resistant starch) that reaches the colon, which is also called energy salvage, compared to adults [159,160]. ...
Article
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Infant cereals play an important role in the complementary feeding period. The aim of this study was to review existing research about the quantity, type, and degree of infant cereal processing, with a special focus on whole grain infant cereals. Accumulating evidence shows many benefits of whole grain consumption for human health. Likewise, consumers are frequently linking the term whole grains to healthiness and naturality, and sustainable food production becomes a more important aspect when choosing an infant cereal brand. Whole grain cereals should be consumed as early as possible, i.e., during infancy. However, there are several challenges that food manufacturers are facing that need to be addressed. Recommendations are needed for the intake of whole grain cereals for infants and young children, including product-labeling guidelines for whole grain foods targeting these age stages. Another challenge is minimizing the higher contaminant content in whole grains, as well as those formed during processing. Yet, the greatest challenge may be to drive consumers’ acceptance, including taste. The complementary feeding period is absolutely key in shaping the infant’s food preferences and habits; therefore, it is the appropriate stage in life at which to introduce whole grain cereals for the acceptance of whole grains across the entire lifespan.
... At weaning, salivary α-amylase and pancreatic α-amylase are present at reduced concentrations compared to that of adults [61]. However, glucoamylase (also referred to as amyloglucosidase), a brush border enzyme in the small intestine capable of cleaving α1,4-glycosidic bonds, is produced at 100-150% of adult concentrations at birth, which may compensate for the otherwise minimal starch hydrolysis [62,63]. Non-digestible structures such as HMOs and non-digestible carbohydrates (NDCs) resist complete enzymatic degradation and pass to the large intestine where they become available as a nutrient source for the enteric microbiota [64]. ...
Article
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Complementary feeding transitions infants from a milk‐based diet to solid foods, providing essential nutrients to the infant and the developing gut microbiome while influencing immune development. Some of the earliest microbial colonisers readily ferment select oligosaccharides, influencing the ongoing establishment of the microbiome. Non‐digestible oligosaccharides in prebiotic‐supplemented formula and human milk oligosaccharides promote commensal immune‐modulating bacteria such as Bifidobacterium, which decrease in abundance during weaning. Incorporating complex, bifidogenic, non‐digestible carbohydrates during the transition to solid foods may present an opportunity to feed commensal bacteria and promote balanced concentrations of beneficial short chain fatty acid concentrations and vitamins that support gut barrier maturation and immunity throughout the complementary feeding window.
... Microscopic analysis of various starch granules due to the action of the enzyme (Dhital, Warren, Zhang, & Gidley, 2014) helps to understand the hydrolysis process and result in the consumption of low glycaemic index foods for individuals who are affected by obesity, diabetes and cardiovascular diseases. The food industry will also be benefited by producing complimentary food products for infants as they have lower activity of pancreatic amylase enzyme (Lin & Nichols, 2017). ...
Article
Starch is a polysaccharide that plays an important role in our diet and aids in determining the blood glucose levels and is the main source of energy to humans and plants. Starch is broken down by hydrolases which are present in our digestive system. We have used α‐amylase for investigating the rate of hydrolysis of rice and potato starch granules. It is found that the hydrolysis depends on the morphology and composition of the starch granules by means of the action of α‐amylase. The micro‐scale structure of starch granules was observed under an optical microscope and their average sizes were in the range, 1–100 μm. The surface topological structures of starches with micro holes due to the effect of α‐ amylase were also visualized under scanning electron microscope (SEM). The chemical and structural composition of rice and potato starches before and after hydrolysis is characterized using Fourier‐transform infrared (FTIR) and X‐ray diffraction (XRD) spectroscopy, respectively. The potato starch is more resistant to α‐amylase than rice starch. The XRD spectra of native and hydrolyzed starch granules remain same which suggests that the degradation occurs mostly in amorphous regions but not in crystalline. Compactly bound water in starch was attributed to the sharp band at 1,458 cm−1 in FTIR spectra. Bands at 920–980 cm−1 associated to α‐(1–4) glycosidic linkage (C‐O‐C) and skeletal mode vibrations in both potato and rice starches. Investigate the changes of size and shape of starch granules (rice and potato) before and after hydrolysis using optical microscope and scanning electron microscope Chemical and structural properties of starches using Fourier transform infrared and X‐ray diffraction spectroscopy
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It has been long recognized that fruits are healthy diet compounds as they are excellent sources of health-beneficial bioactive components (polyphenols, minerals, vitamins, organic acids, etc.). The diversification of the consumer’s taste calls for an expansion of food options and novel ingredients. Puddings are a well-known food choice introduced in the human diet at a very early age because of their easy and high digestion. Four formulations with two types of starch (corn and rice) were selected as object of analysis. Nectarines were incorporated as a purée, and lyophilized powder. The nectarine variety “Gergana”, used for the preparations, is a local variety with proven beneficial properties. The study aimed at analyzing the physical (moisture, ash, color, water-holding capacity, water activity, density and syneresis), textural (firmness, gumminess, cohesiveness, springiness, and chewiness), nutritional, and sensory characteristics of the nectarine-enriched puddings. The outcomes obtained from this study provided significant information about the possible application of the formulations in the children’s daily menus. All four formulations had distinct peachy aroma. The formulations prepared with nectarine purée resulted in a better sensory perception about their texture, and better water-holding capacity. At this point, the formulation prepared with lyophilized fruit and rice starch has the most promising results. Sufficient evidence leads to further exploration of the perspective of fruit-enriched puddings in order to improve their technological and health-promoting properties.
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Starch requires six enzymes for digestion to free glucose: two amylases (salivary and pancreatic) and four mucosal maltase activities; sucrase-isomaltase and maltase-glucoamylase. All are deficient in suckling rodents. The objective of this study is to test 13 C-starch digestion before weaning by measuring enrichment of blood 13 C-glucose in maltase-glucoamylase-null and wild-type mice. Maltase-glucoamylase gene was ablated at the N-terminal. Dams were fed low 13 C-diet and litters kept on low 13 C-diet. Pups were weaned at 21 days. Digestion was tested at 13 and 25 days by intragastric feeding of amylase predigested 13 C-α-limit dextrins. Blood 13 C-glucose enrichment was measured by gas chromatography combustion isotope ratio mass spectrometry (GCRMS) using penta-acetate derivatives. Four hours after feeding, blood 13 C-glucose was enriched by 26 × 10 3 in null and 18 × 10 3 in wild-type mice at 13 days and 0.3 × 10 3 and 0.2 × 103 at 25 days (vs. fasting p = 0.045 and p = 0.045). By jejunal enzyme assay, immunohistochemistry, or Western blots, there was no maltase activity or brush border staining with maltase-glucoamylase antibodies at 13 days, but these were fully developed in the wild-type mice by 25 days. In 13-day null mice, luminal contents were stained by maltase-glucoamylase antibodies. Lactating the mammary gland revealed maltase-glucoamylase antibody staining of alveolar cells. Reverse transcription/polymerase chain reaction (RT/PCR) of lactating glands revealed a secreted form of maltase-glucoamylase. (1) 13 C-α-limit dextrins were rapidly digested to 13 C-glucose in 13-day mice independent of maltase-glucoamylase genotype or mucosal maltase activity. (2) This experiment demonstrates that a soluble maltase activity is secreted in mouse mother’s milk which enables suckling pup starch digestion well before brush border enzyme development. (3) This experiment with 13 C-α-limit dextrins needs to be repeated in human breast fed infants.
Article
The digestibility of starchy foods, such as potatoes, can be characterized by the proportion of starch that is rapidly digestible by in vitro hydrolysis (rapidly digestible starch, RDS). This study evaluated the RDS content in a potato germplasm collection consisting of 98 genotypes and identified three advanced lines, Crop39, Crop71 and Crop85, where cooked potato RDS content was significantly lower than that of their respective isolated starches (P < 0.05). In Crop39, Crop71 and Crop85, the properties of their isolated starch did not differ significantly from that of five control lines with higher RDS contents. Cell wall analyses revealed that, compared with other lines tested, Crop39, Crop71 and Crop85 had at least four times the amount of rhamnogalacturonan-I (RG-I) galactan side-chains that were very firmly attached to the wall and requiring 4 M KOH for extraction. Pectin solubilization during cooking was also remarkably low (2-4%) in these three lines compared with other lines tested (7-19%). The findings suggest that possession of higher amounts of RG-I galactan that interact strongly with cellulose may provide a sturdier wall that better resists solubilization during cooking, and effectively impedes access of digestive enzymes for starch hydrolysis in an in vitro model.
Article
The gastric empyting of six infant feedings (20 kcal/oz; whey to casein ratio, 60:40) with varying fat and carbohydrate composition was studied. Feedings contained either predominantly long-chain triglycerides (94%) or predominantly medium-chain triglycerides (94%) as the fat and lactose, glucose, or glucose polymers (Polycose) as the carbohydrate. Eleven premature infants were fed 22 ml/kg body wt of all six feedings over a 3–4-day period, and the volume of gastric contents was measured every 20 min using polyethylene glycol 4000 as the marker. Analysis of variance demonstrated that the use of medium-chain triglycerides resulted in faster gastric emptying than long-chain triglycerides (p < 0.001). Analysis of variance and Tukey's test showed that use of glucose polymers instead of glucose resulted in less volume of gastric contents at 40 min (p < 0.05). Use of glucose polymers instead of lactose resulted in less volume of gastric contents at 60 and 80 min (p < 0.05). Gastric empyting can be altered by changes in nutrient composition. The difference between medium-chain and long-chain triglycerides was more pronounced than the differences between the carbohydrates studied. Feedings with medium-chain triglycerides may be more suitable than long-chain triglycerides in patients with delayed gastric emptying.
Article
The purpose of the present study was to find the variations in average granule size, amylose content, gelatinization properties (onset temperature, To ; gelatinization heat, OH) by differential scanning calorimetry (DSC) and digestibility of raw starch by crude and crystalline glucoamylases for 30 kinds of sweet potato starches . Further, the relationships among these starch properties were also studied to determine the factors relating to digestibility of raw starch by amylase. Significant negative correlations were observed between average granule size and digestibilityby each one of the two glucoamylases. ΔH was also negatively correlated with digestibility by each one of the two glucoamylases . No significant correlations existed between two other properties (amylose content and To) and digestibility by each one of the two glucoamylases.
Article
Pores were observed on maize (corn), sorghum and millet starch granules and hypothesized to be openings to channels that provide access to the granule interior. Later, the existence of channels was established unequivocally, and clear evidence that channels in corn and sorghum starch granules connect an internal cavity and the external environment was presented. It was found that flow of reagents into the matrix of corn and sorghum starch granules occurred primarily from channels and the cavity. Granular reaction patterns were observed by converting derivatives into thallium salts and locating the thallium ions by compositional backscattered electron imaging. A different, but similar, and simpler technique for locating the position of reaction has been developed. It involves conversion of derivatizing groups into silver salts, reduction of the silver ions to silver atoms, and locating the silver atoms by reflectance confocal laser scanning microscopy. Use of this method confirmed that highly reactive reagents react primarily on or near granule surfaces, primarily the surfaces of channels and the cavity, while less reactive reagents diffuse throughout the granule matrix before reacting.
Article
Starch is synthesized in semi-crystalline granular structures. Starches of different botanical origins possess different granular sizes, morphology, polymorphism and enzyme digestibility. These characteristics are related to the chemical structures of the amylopectin and amylose and how they are arranged in the starch granule. In this paper, structures and locations of amylose and amylopectin molecules in the granule are reviewed. The branch structures of amylopectin molecules and their relationship with the polymorphism, structures, and morphology of the starch granules are discussed. Internal structures of starch granules revealed by confocal laser-scattering microscopy and by using a surface-gelatinization method are compared and their effects on surface pinholes and serpentine channels of the starch granules are discussed.