SAGO PALM 24: 20−25 (2016)

Polymorph and Crystallinity Disruption ofSago Starch during Gelatinization
Masanori Okazaki1,*, Naoya Katsumi1, Shun Nishiyama1, Tetsuya Yamazaki1,Yuji Honda1, Kenji Matsumoto1, Malcelo A. Quevedo2 and Suzette B. Lina2
Ishikawa Prefectural University, 1-308, Nonoichi, Ishikawa 921-8836, Japan

1

Visayas State University, Baybay, Leyte, The Philippines

2*Corresponding author

Abstract: Sago starch samples were collected from Port Moresby of Papua New Guinea (PNG) and Baybay,Leyte, of the Philippines (PLP) to study the polymorph and crystalline disruption of sago starch during
gelatinization using corn and potato starch as references. Starch granule suspension was transferred onto a glass
slide covered with a cover glass, sealed with nail polish to prevent moisture loss, mounted on a micro-heatplate,and observed using an optical microscope equipped with cross polarizers and a λ-plate. The behavior of sago
starch granules during gelatinization was shown by the granular birefringence (Maltese cross) observed underpolarized light. The initial, middle, and end gelatinization temperatures determined by a hot stage were,respectively, 78° C, 80° C, and 83° C for PNG sago starch and 76 ° C, 81° C, and 89° C for PLP sago starch inwater. Sago starch still exhibited C-type crystallinity from 60 to 75° C. However, the X-ray diffraction peak at 5to 6° for 2 θ was observed to decrease, disappearing with increased heating temperature. At 18 °, the peaks ofPNG and PLP starches began to appear and slightly increase, although the intensity was decreased as a whole.
The disappearance of B-type crystallinity from sago starch occurred during gelatinization.
Keywords: gelatinization, micro-heatplate, optical microscope, sago starch
Introduction

Starch granules consist of mainly linear amylose andhighly branched amylopectin. The branch chain lengthsof amylopectin differ between A-type and B-typegelatinization between those of A and B types. However,there have been few reports on this polymorph and thedisruption of the structure of sago starch that accompanies

gelatinization, although the observation of crystallinity

crystalline starches (Hizukuri, 1985). Starch with longer

disruption patterns during gelatinization for C-type starches(1986) reported the polymodal distribution of the lengthsof starch granules during gelatinization was shown by thebranch chains displays the B type, and starch with shorter

branch chains displays the A-type. Furthermore, Hizukuriof the amylopectins of waxy rice, tapioca, kuzu, andwas carried out using the pea (Bogracheva et al., 1998) andlotus rhizome starches (Cai and Wei, 2013). The behavior

granular birefringence observed under a polarizing

potato. Jane et al. (2003) showed that A-type starches

microscope with a λ-plate in combination with a hot stage.

amylopectin molecules of B-type starches have smallerthat B polymorphs were situated in the center of allpossessed more short branch chains and were more easily

digestible by amylases than were B-type starches. The

molecular weights and less dense dispersed molecules

Bogracheva et al. (1998) concluded that A- and B-type
polymorphs were present in the same pea granules, andgranules. However, the disruption of the crystalline

than do those of A-type starches (Jane et al., 2003).

structure of lotus rhizome C-type starch first occurred on

granules (Sair, 1967). It has intermediate characteristics ofsurface of the eccentric hilum (Cai and Wei, 2013). Cai etSago starch, a C-type starch, is composed of polymorph

structures, A and B types, that occur within the samethe distal surface of the eccentric hilum and propagatedalong granules from the distal surface of the proximal

Polymorph and Crystallinity Disruption of Sago Starch during Gelatinizational. (2014) proposed a model of allomorph distribution and21heating was used: from room temperature to 50°C with aa gelatinization process of lotus rhizome in which the A-

heating rate of 5°C min-1, a holding temperature at 50°C

mixed distribution of the A- and B-type allomorphs.

from 90°C to 25°C with a heating rate of 10°C min-1. A

type allomorph was mainly located in the periphery regionof the hilum end, and the central part of the granule had aThe objectives of this study are to show the polymorphof sago C-type starch and to determine the crystallinity
disruption of sago starch during gelatinization.

Materials and Methods
1. Sago starch samples

Sago starch samples were collected from Port

Moresby of Papua New Guinea (PNG) and Baybay,

for 30 sec, from 50° C to 90° C with a heating rate of
1°C min-1, a holding temperature at 90°C for 5 min, andprocess of cooling was required for the next specimen.

The starch granules during heating were observed with a

400x objective lens and photographed with a camera(Cannon EOS KISS X5).

3. X-ray diffraction analysis of native andgelatinized starch samples

Native and heated starch suspensions (2.5% w/v) were

Leyte, of the Philippines (PLP). PNG samples wereshaken by hand to resuspend the sediment starch inBaybay by the authors in 2011. The annual mean

were heated at 60 to 80° C for 3 min. The heated starch

Island, which is located in 150 km west of Baybay),four times with Milli-Q water and anhydrous ethanol andobtained from a sago starch shop in the Koki Market,

Port Moresby, in 2001. PLP samples were extracted intemperatures of Port Moresby and Baybay are 27.3° Cand 28.0° C (the annual mean temperature of Mactan

respectively. The moisture content of sago starchstocked in the laboratory was 12% for PNG and 13%for PLP. Corn (Kosakai Pharmaceutical Co., Tokyo,accordance with the method of Bogracheva et al. (1998)

and Cai et al. (2014). In a water bath, the starch samples
samples were immediately cooled in an ice bath andcentrifuged (2140 g) for 10 min. The samples were washedthen dried at 40° C for 3 days using a Shibata BV-001
under 0.065 MPa. The dried starch samples were groundinto powder in a mortar and pestle. After pretreatment, theJapan) and potato (Miyazawa Pharmaceutical Co.,moisture contents of the PNG and PLP samples were 4.56

2. Microscopic observation of starch granules

samples were 3.68 % and 5.05 %, respectively.

Tokyo, Japan) starch samples were used as references.

A starch granule suspension was prepared bydissolving 10 mg starch in 1.0 mL distilled water, andwas transferred onto a glass slide covered with acover glass and sealed with nail polish to prevent
moisture loss (Cai et al., 2014). The specimen wasmounted on a micro-heatplate (Kitazato MP-1000H,Shizuoka, Japan) and observed using a polarizing
microscope (Meiji MT 9000, Saitama, Japan)% and 4.61 %, respectively. X-ray diffraction analysis

showed that the moisture contents of the corn and potato
X-ray diffraction (XRD) analysis was performed

using a Rigaku MiniFlex. Copper (Cu) K α radiation

was used with nickel filter. The scanning speed wasrecorded as 2° min-1, and the operation angle was 3° to45° for 2θ. The samples were held on an antireflection

silicon sample holder because of its exclusion of

external X-ray intensities (Katsumi et al., 2015).

equipped with cross polarizers and a λ-plate.

Results

The behavior of sago starch granules during

temple bell shapes, with the eccentric hila at one end

A native starch suspension (2.5% in distilled water)

was shaken by hand to resuspend the sediment starch.

gelatinization was shown using the Meiji MT 9000 toobserve granular birefringence (Maltese cross) underpolarized light on a micro-heatplate. The step mode of1. Morphological characteristics of sago starch

Native sago starch granules had medium oval andof the granules (Figs. 1 and 2, normal, polarized, andλ-plate); these appearances were similar to thoseobserved by Kobayashi (1993).

22M. Okazaki et al.

Fig. 1. Micrographs of PNG sago starch under normal and polarized light in conjunction with a λ-plate during gelatinization
Bar is 50 μ m.
The number in parentheses shows the temperature during gelatinization.

Fig. 2. Micrographs of PLP sago starch under normal and polarized light in conjunction with a λ-plate during gelatinization
Bar is 50 μ m.
The number in parentheses shows the temperature during gelatinization.

Polymorph and Crystallinity Disruption of Sago Starch during Gelatinization

23

Fig. 3. Micrographs of corn starch under normal and polarized light in conjunction with a λ-plate during gelatinization
Bar is 50 μ m.
The number in parentheses shows the temperature during gelatinization.

Fig. 4. Micrographs of potato starch under normal and polarized light in conjunction with a λ-plate during gelatinization
Bar is 50 μ m.
The number in parentheses shows the temperature during gelatinization.

M. Okazaki et al.

24

2. Crystalline structure disruption in sago starch
granules during gelatinization

The behavior of sago starch granules was shown by

the granular birefringence (Maltese cross) observed

under polarized light before gelatinization (Fig. 1,polarized and λ-plate). The blue and yellow areas,indicating radial alignments, represent the regions ofcrystallinity of sago starch. The loss of colors uponheating indicates the disappearance of the radialalignment of crystallinity. The disruption of crystallinity

occurred on the proximate surface of the eccentric

hilum and was propagated from the proximate surface

allomorphs containing different proportions of A- andB-type polymorphs in PNG and PLP sago starches, asseen in Fig. 5, as compared to corn (A type) andpotato (B type) starches. The peak intensity of PNG

sago starch at 60 ° C from 3 ° to 40° was lower thanthat at 21 ° C, which is caused by the gradualprogression of gelatinization (Fig. 1, λ-plate (21) to λplate (60)). This kind of peak-lowering observation

resembled that of the potato sample. The corn sample
showed strong X-ray diffraction peaks at about 17 °,18 °, and 23 ° for Cu K α, and the potato sample

exhibited strong diffraction peaks at about 5.6°, 18°,

to the distal surface of the eccentric hilum. The initial,22 °, and 23 ° for Cu K α. Sago starch samples still

83.0° C for the PNG sago starch (Fig. 1), and 75.9° C,with increasing heat from 65 ° C. The B-type

middle, and end gelatinization temperatures determinedby a hot stage were, respectively, 78.0° C, 80.0° C, and80.9° C, and 89.1° C for the PLP sago starch (Fig. 2).

Figures 3 and 4 show microscopic images of corn andpotato starch during gelatinization, which reveals lower

starting temperatures of gelatinization : 70.0° C for corn

and 69.8°C for potato.

However, the corn sample’s peak intensity decreased

crystallinity disappeared from 70° C. At 17° to 18°, thedouble sharp peaks began to be single clearly, and theclear single peak gradually disappeared. This kind ofalteration also showed that the crystallinity of sago

starch changed from C-type (mixture of A-type and B-

Relative intensity cpstype) to the A-type only, which caused theRelative intensity cps

Relative intensity cps

Relative intensity cps

X-ray diffraction (XRD) showed C-type

showed C-type crystallinity from 60 ° C to 75 ° C.

Fig. 5. Changes in the X-ray diffraction of starch samples during gelatinization

Polymorph and Crystallinity Disruption of Sago Starch during Gelatinization

disappearance of water molecules in the cavity of Btype crystallinity, according to the X-ray diffraction
pattern (Okazaki et al., 2015). The peak intensity at

5.6°, 17°, 18°, 22°, and 23° of all starches significantly
decreased at more than 80°C.
Discussion

1. Type classification of starch structure

disruption using a polarized microscope

The structure disruption of sago starch (C type)

during gelatinization has not yet been completely

discussed. Cai and Wei (2013) proposed that during
gelatinization, starch granules were classified into four

patterns of crystallinity disruption (P1: on the proximate
surface of the eccentric hilum, P2: on the distal surfaceof the eccentric hilum, P3: from the central hilum, and25

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