Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals

Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals

Accepted Manuscript Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from diff...

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Accepted Manuscript Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals

Harpreet Kaur, Balmeet Singh Gill PII: DOI: Reference:

S0141-8130(18)33730-9 https://doi.org/10.1016/j.ijbiomac.2018.12.149 BIOMAC 11308

To appear in:

International Journal of Biological Macromolecules

Received date: Revised date: Accepted date:

20 July 2018 9 December 2018 16 December 2018

Please cite this article as: Harpreet Kaur, Balmeet Singh Gill , Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals. Biomac (2018), https://doi.org/10.1016/ j.ijbiomac.2018.12.149

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ACCEPTED MANUSCRIPT Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals Harpreet Kaur*, Balmeet Singh Gill

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Department of Food Science and Technology, Guru Nanak Dev University, Amritsar, India *Corresponding author, E mail address: [email protected]

ACCEPTED MANUSCRIPT ABSTRACTs The ultrasonication was applied to four cereal starches namely wheat, barley, rice, and maize for two ultrasonication treatment durations, i. e., 15 and 30 min (T 15 and T 30, respectively) and were evaluated for their in vitro digestibility, XRD, FTIR spectroscopy, morphological and rheological properties. Ultrasonication increased the swelling power and solubility of starches from different cereals. For ultrasonicated starches (both raw and

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cooked), the RDS and RS content exhibited significant (P ≤ 0.05) an increase with an

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increase in treatment duration. RDS content exhibited an increase after both cooking and

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ultrasonication and ranged between 67.8-81.4%, whereas RS content declined with cooking and enhanced with ultrasonication and ranged between 2.3-3.1% after T 30 while SDS

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content decreased with increase in ultrasonication duration. FTIR spectra of ultrasonicated starches showed the characteristic broad peaks at 3351 to 3404 cm-1and to assigned to O-H

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stretching of the hydroxyl group. The rheological properties showed an increase in G′ and G′′ for 15 min ultrasonication and decreased with 30 min ultrasonication. The main effects

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of ultrasonication were led to the formation of depressions and pores on the surface of starch granules, which were appropriately observed in wheat and maize starches.

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Abbrevations 1. NWS- native wheat starch 2. WSS-15- wheat ultrasonicated starch for 15 min 3. WSS-30- wheat ultrasonicated starch for 30 min 4. NRS- native rice starch 5. RSS-15- rice ultrasonicated starch for 15 min 6. RSS-30- rice ultrasonicated starch for 30 min 7. NMS- native ultramaize starch 8. MSS-15- maize ultrasonicated starch for 15 min 9. MSS-30- maize ultrasonicated starch for 30 min 10. NBS- native barley starch 11. BSS-15- barley ultrasonicated starch for 15 min 12. BSS-30- barley ultrasonicated starch for 30 min

Keywords: Crystallinity, Digestibility, Rheological properties, starch morphology, Ultrasonication

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1. Introduction

Starch properties have been under investigation for many years. The desired

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functionality and unique physicochemical properties required for food products are rarely satisfied by native starches. Native starch is usually modified chemically, enzymatically,

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genetically and physically to develop novel food products. In these days, physical modifications are gaining importance in food industries due to the limited use of chemical

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agents [1]. Ultrasound treatment serves as an effective method of starch modification, exhibits various advantages in terms of quality and higher selectivity, limited application of

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chemicals and less processing time, and therefore considered as an environment-friendly processing. Ultrasound is acoustic energy above the frequency than those audible for

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humans limit of 18-20 kHz. This method can be employed either on native starch granules suspended in solution or on gelatinized starch [2]. Ultrasonication mainly disrupts the amorphous region of starch granules, as their shape and size remained unchanged but their surface becomes porous and enhanced the physicochemical properties such as a change in swelling power, solubility and pasting parameters [3]. In food processing and preservation, ultrasonication showed beneficial effects such as higher product yield, reduced operating and maintenance costs with improved quality characteristics, destruction of pathogens etc [4]. However, this treatment not only improves the food quality and safety but also provide the opportunities for developing novel food products with unique properties [5,6,4].

ACCEPTED MANUSCRIPT Compared to other starch modification techniques such as acid hydrolysis, ultrasonication found to be more effective, rapid and did not require any chemical agent. The efficiency of ultrasonication depends on many factors, such as sonication power and frequency, time and temperature of the treatment and properties of the starch suspension i. e., concentration and biological origin of starch. The bubbles of gases formed in the cavities as the pressure decreases which bombard starch granules before they collapse as the

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pressure increased [7]. This process is known as cavitation. The shear forces arise when

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bubbles collapse rapidly which can disrupt the polymers chains such as starch. Also, the

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polymer degradation occurs as the solvent molecules dissociate to form radicals [3]. As a green technology i.e environment-friendly, ultrasonication can greatly influence the

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composition, structure, properties of starches from diverse botanical origins. In most cases, pores and fissures in the granules are caused by ultrasonication. Therefore, the structural

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changes further affect the physicochemical properties of starch. As starch is the major ingredient used in various foods and industrial applications,

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therefore, the focus is ultrasonication of cereal starches which affected the components of starches and altered the properties of food products. The research summarizes the impact of

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ultrasonication on the rheology, physicochemical, functional, in vitro digestibility, morphology and crystalline properties of starches from the different botanical origin.

2.1. Materials

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2. Materials and methods

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Four cereal crops, wheat (Triticum aestivum) (HD-3086), rice (Oryza sativa) (PR-123), maize (Zea mays) (Super-777), barley (Hordeum vulgare) (PL-426) were procured from

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Punjab Agriculture University, Ludhiana, (India). The grains were cleaned to remove dirt, foreign material and any damaged seeds and then stored at 20 °C until further use. The chemical and reagents were used of the analytical grade. All enzymes used in this study were procured from Sigma-Aldrich (Taufkirchen, Germany). Milli-Q water was used for experiments. 2.2. Starch Isolation Starch from different cereals isolated by using different method. Starches from different cereals were isolated using the method proposed by Sandhu et al.[8] Singh et al.[9], Sodhi

ACCEPTED MANUSCRIPT and Singh [10] and Vasanthan and Bhatty [11] from maize, wheat, rice, and barley respectively. 2.3. Ultrasound Treatment The samples for ultrasound treatment with the probe (24 kHz) of 50 mL volume were placed in a flat-bottomed conical flask. Samples were treated for 15 and 30 min with power ultrasound of 100W of nominal power with a constant amplitude of 100%. High intensity

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and low frequency 24 kHz probe was attached to the transducer. The Probe had a vibrating

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titanium tip of 2 mm in diameter and was immersed in the liquid and the liquid is irradiated

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with an ultrasonic wave directly from the horn tip. During treatment, the vessels containing starch samples were held in water bath to prevent any rise in temperature by

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ultrasonication.Then subsequently, the starches were centrifuged (3000 x g) and dried in hot air oven at 45ºC until dried.

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2.4. Swelling Power and Solubility

Swelling power and solubility of different starches were determined according to the

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method of Leach et al. [12]. The aqueous suspension (1%) of starch (100 ml) was heated at 95ºC with constant stirring in a water bath for 1 h. The suspension was allowed to cool at

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30ºC for 30 min. Then the sample was transferred to the preweighed centrifuge tubes, centrifuged for 10 min at 3000 × g and the weight of sediment was measured. To determine

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the solubility, the supernatants were transferred to petridishes and evaporated in hot air oven at 110°C for 12 h, cooled to room temperature in a dessicator and weigh the dry solids.

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2.5. Particle Size Analysis

Particle size distribution of different cereal starches was determined by using laser-light

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particle size analyzer (S3500, Microtrac Inc., USA) provided with a delivery system for dry samples (Microtrac Turbotrac SDC, Microtrac Inc., USA). 2.6. Morphological Characteristics Screening electron micrographs were obtained with a screening electron microscope (Model EVOLS10 ZEISS, Oberkochen, Germany). Starch samples were suspended in ethanol to obtain a 1% suspension. One drop of the starch-ethanol solution was applied on an aluminium stub tape and the starch was coated with gold-palladium (60:10). 2.7. Crystalline properties 2.7.1. X-Ray Diffraction (XRD)

ACCEPTED MANUSCRIPT X-ray diffractograms of different starch samples were measured using an analytical Xray diffractometer (Rigaku Miniflex, Japan) having CuKα source, with a wavelength of λ= 1.54 Å functioning at 45 kV and 40 mA. X-ray diffractograms were obtained at 25ºC in the 2θ angle range of 4-30ºC with a step size of 0.02 and 10s scan speed. The MS Excel data was exported to (OriginPro 8E, OriginLab, USA) software for graph creation. The crystalline index (%) and d-spacing index of different starches were calculated by the

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2.7.2. Fourier Transform Infrared Spectroscopy (FTIR)

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methods followed by Kaur et al.[13]

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FTIR spectrum was performed on Fourier transform spectrophotometer (PerkinElmer FTIR-C92035, USA) with wave number in the range of 400-4000 cm-1 using KBr pellet

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method. 2.8. Dynamic Rheological Properties

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The changes in the viscoelastic properties of starch pastes for retrogradation were determined using rheometer equipped with parallel-plate geometry (PP-40) following the

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method of Shevkani et al. [14]. Gap, stress and frequency were 1.0 mm, 1 Pa and 1.0 rad/s, respectively. These values were within the linear viscoelastic range. For the preparation of

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starch pastes, starch suspensions (20 % w/w) were stirred for 1 h in sealed vials at room temperature and then cooked in a water bath set at 95 °C for 30 min with vortex shaking (10

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s) at an interval of 2 min. The cooked starch pastes were immediately transferred between the plates of the rheometer preheated to 90 °C. The pastes were cooled from 90 to 10 °C at a

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rate of 2.5 °C/min and then held at 10 °C for 30 min. Storage and loss modulus (G′ and G′′ respectively) of the cooked starch pastes were recorded.

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2.9. In Vitro Digestibility of Starches In vitro digestibility of starch was determined according to the method established by Englyst et al. [15] with minor modifications. Then the rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) were analyzed on the basis of their digestion rates. 2.10. Statistical Analysis The data reported in all the tables is averages of triplicate observations. The results were evaluated using Analysis of Variance (ANOVA) and expressed along with the standard error of the mean value. The averages were compared by Fisher's least significant difference

ACCEPTED MANUSCRIPT (LSD) test, and differences at P < 0.05 were considered significant. The data was subjected to statistical analysis using Minitab Statistical Software version 17 (Minitab Inc., USA). 3. Results and discussion 3.1. Swelling power and solubility The swelling power (SP) and solubility of native and modified starches are shown in Table 1. These parameters are attributed to starch granule structure, temperature,

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amylose/amylopectin ratio, their molecular weight, degree of association between their

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chains and phosphorous content [16]. Among native starches, the highest values of SP and

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solubility were observed for rice which could be attributed to the higher content of phosphate groups on amylopectin. In this way, the extent of bonding within the crystalline

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domain gets weakened by phosphate groups and subsequently, increases granule hydration [17]. The ultrasonication significantly (P < 0.05) increased SP and solubility of starches

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from different cereals. This could be caused by the physical and chemical disruption of starch granules leading to higher water uptake and retention. After ultrasonication of 30 min

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different cereals i. e. wheat, barley, rice and maize exhibited SP values of 17.42, 14.46, 18.18 and 17.41 g/g and solubility values of 11.48, 10.11, 9.59 and 13.79%, respectively.

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Similar results were reported by Jambrak et al. [18] for corn starch and Sujka and Jamroz [3] for potato, wheat, corn and rice starches. The amorphous regions of starch granules are

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specifically disrupted by ultrasonication owing to its lower structural integrity, where the amylose is located compared to amylopectin location which is in the crystalline state.

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Therefore, the ultrasonication resulted in the release of amylose to the aqueous medium, thereby increasing solubility that may be attributed to the amylose associated leakage

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outside the granules [18]. The ultrasonication may have caused changes in the physical geometry of pores and channels on the surface of starch granules allowing water molecules to penetrate more easily into the large volume of the granule, thereafter increasing the solubility of the granules. It has been described that the elevation in swelling power induced by ultrasonication may be assigned to the disintegration of intermolecular bonds, disruption of crystalline molecular structure of starch and caused the water molecules to bind with the free hydroxyl groups of amylose and amylopectin by hydrogen bonds [18, 3], breaking clusters of starch granule [2], and structural changes and therefore increasing absorption of starch granules.

ACCEPTED MANUSCRIPT 3.2. Particle size distribution The granular size distribution showed slight changes as compared to their native counterpart as shown in Table 2. The starches from different cereals showed tri-modal granular size distribution revealed the presence of A-type (large), B-type (medium) and C-type (small) starch granules of >15µm, 5-15 µm and <5 µm respectively. The ultrasound treatment results in different size reduction patterns for different cereal starches. The laser light

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diffraction of starches showed the size of starch granules in the range of 3.89 to 52.33µm for

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wheat, 2.75 to 44 µm for rice, 3.89 to 62.23 µm for maize and 3.89 to 88 µm for barley

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starch. The A-type proportion of ultrasonic starches showed only slight variation in their size distribution as compared to their native counterparts. This indicates that there is little or

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no depletion of the size of starch granules. This may be attributed to the large size granules as they present the large surface to confine the ultrasound waves. The B-type proportion of

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starch granules increased after ultrasonication indicating the breakdown of large starch granules by ultrasonic waves. However, this increase was not continuous in case of all the

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lines. This pattern indicates that cavitation and mechanical action by the ultrasonication expanded the structure of starch granules by inducing changes in its physical geometry. It

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was observed that barley starch granules (average particle size = 28 µm) were largest in size followed by maize, wheat and rice starch granules (average particle size was 21.7, 19.27 and

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15.4 µm respectively. These results indicate that ultrasonication caused surface and microstructural changes in the physical geometry of granules with minimum effect on the

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overall integrity of starch granules. 3.3. Morphological characteristics

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The changes in the structure of starch granules due to ultrasonication are shown in Fig. 1. During ultrasonication, the starch granules get ruptured and mechanically damaged by collapse of cavitation bubbles which produce high pressure gradients and high local velocities of liquid layers in their vicinity, therefore shear forces occurs that are capable of breaking polymer chains and damaging granules[19]. The surface of native wheat and barley starch granules were viewed smoother as compared to rice and maize starches. After ultrasonication treatment, the surface of starch granules undergoes the formation of depressions, pores and channels as visualized on the surface of granules. These changes were more intensively found in wheat and maize starches than rice and barley ones. The

ACCEPTED MANUSCRIPT wheat starch showed the small fissures and depressions on the surface of granules. The pitting of maize starch granules was detected after ultrasonication and the pit size increased with increasing the treatment time. In this study, the maize starch is more intensely affected which suggests that maize starch has a relatively weaker granular structural integrity as compared to rice, wheat and barley starches. According to Fannon et al. [20] during sonication, the granules of corn starch easily disrupted by cavitation effect may be attributed

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to the presence of natural pores and cavities in these starch granules. In barley and rice

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starches, there could be less prominent pores or fissures detected under SEM after being

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treated with sonication. 3.4. Crystalline Properties

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3.4.1. X-Ray Diffraction (XRD)

X-ray diffraction measurements were performed to analyse the effect of ultrasound on

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the X-ray pattern and crystalline index (Fig. 2. and Table 3). All starches represent the typical A-type X-ray patterns with characteristic peaks at 15.2º, 17.8º (doublet peak), 18.5º

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and 22.7º. For different cereal starches, X-ray diffraction patterns presented the major peaks with d-spacing around at 5.86, 4.91, 4.45 and 3.87 Å (Table 2), representative of an A-type

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crystalline packing arrangement. The crystalline index of various native starches ranged from 32.08 to 44.39%. The ultrasonication had a little influence on the crystallinity of

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starches as the diffraction patterns of sonicated starches slightly changed, whereas crystalline nature of starch remained unchanged. Ultrasonication had little effect on the

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polymorph type of maize starch (A-type) [21] and potato starch (B-type) [19] as shown by wide-angle X-ray diffraction analysis (WAXS). XRD showed no statistical difference

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(P>0.05) among the ultrasonicated starches. The crystallinity of starch may be either increased or decreased, depending on the conditions of ultrasonication [22]. The variability observed among the native and ultrasonicated starches was insignificant as shown by diffraction intensities. It may thus be assumed that the granules with different packing of the crystalline and amorphous parts give rise to their different susceptibility to the ultrasonication. The crystalline index of different starches was in the order of maize > rice > barley > wheat. 3.4.2. Fourier Transform Infrared Spectroscopy (FTIR)

ACCEPTED MANUSCRIPT FTIR spectra were recorded to study the effect of ultrasound on the structure of different cereal starches (Fig. 3.). FTIR spectra of starches showed the characteristic broad peaks at 3351 to 3404 cm-1 and to assigned to O-H stretching of hydroxyl group. The intensity of this band get strengthen on ultrasound treatment revealed that ultrasonic waves gave more potential to microstructure of starch to retain bound water [13].There was a slight difference observed among the starches from different cereals. The later peaks at 2928 to 1071 cm-1

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attributed to the C-H stretching of glucose unit and is also intensified by ultrasonic

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treatment. Bands due to water located in amorphous region of starch at 1642 to 1652 cm-1.

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Peaks at 1453 to 1465 cm-1, 1153 to 1164 cm-1 and 989 to 1019 cm-1 are assigned to the vibration of C-H stretching, C-H and C-O-H bending, respectively. Furthermore, the bands

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appeared at 923 to 936 cm-1, 761 to 768 cm-1 and 571 to 579 cm-1 related to the thoroughgoing vibrations of anhydrous glucose ring stretching. The deconvoluted FTIR spectra with

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wave numbers from 800-1200 cm-1 (Fig. 3.) depicts the short ranged molecular order of starches from different cereals. The index of crystallinity can be determined from the

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absorbance ratio of R1047/1022 as intensity of 1047 cm-1 divided by the intensity of 1022 cm-1. This ratio indicates the short-range crystallinity associated with the double-helix packing

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enclosed by the inner granule microstructure. For native starches, the intensity ratios of 1047/1022 and 1022/995 cm-1 ranged from 0.8551 to 1.0063 and 0.9408 to 0.9873

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respectively (Table 3 ). The rice starch showed the highest 1047/1022 cm-1 intensity ratio whereas wheat starch had the highest 1022/995 cm-1 absorbance ratio. The absorbance ratio

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1047/1022 cm-1 wavenumbers non-significantly (p < 0.05) related to CI of different native cereal starches. Higher the 1047/1022 cm-1 absorbance ratio higher will be the relative

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crystallinity, and lower the 1022/995 cm-1 absorbance ratio higher will be the double helices of starch granules. [23] Van Soest et al. [24] and Ispas-Szabo et al. [25] also suggested that FTIR study of starch is not able to differentiate between the A and B polymorphs and thus the long-range packing. Hence, correlations between IR (infrared) and X-ray suggested in the literature can be misleading. 3.5. In vitro digestibility The in vitro digestibility of native and ultrasound treated starches are shown in Table 4. The starch fractions i. e., RDS, SDS and RS were affected significantly (P ˂ 0.05) by different durations of ultrasonication (Table 5). For uncooked or raw starches, RDS content

ACCEPTED MANUSCRIPT of different native starches ranged from 34.7 to 54.4% and it exhibited significantly (P ˂ 0.005) increase from 41.8 to 59.3% after 30 min of ultrasonication. Rice starch showed the highest RDS followed by maize and wheat. The variations found in starch digestibility may be attributed to the various factors such as type of cereal from which starch isolated, granular size, degree of crystallinity, physicochemical properties of starches and is affected by various processing and storage conditions [26]. The structural changes in starch granules

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either in molecules or in crystallinity may be attributed to change in starch digestibility. As

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the granules of starch after ultrasonication become porous and tend to be more susceptible

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by enzymatic attack. The disruption of double-helix structure of starches after ultrasonication contributed to the accessibility of enzymes at the sites susceptible to

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digestive enzymes leading to a degradation of amylopectin chains. As the crystalline regions are more compactly ordered than amorphous regions, therefore they are less susceptible of

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attack by digestive enzymes [27]. SDS content ranged from 39.5 to 53.7% among the different native (raw) cereal starches and it significantly (P < 0.005) decreased in case of

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cooked as well as ultrasonicated starches. SDS ranged between 37.5-51.0% and 33.5-45.0% for raw starches after 15 and 30 min of ultrasonication, respectively. RS of various native

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(raw) starches ranged from 6.1 to 11.6%, which exhibited an increase with increase in ultrasonication treatment durations and ranged between 6.8-12.4% and 7.2-13.2%,

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respectively.

In case of cooked (gelatinized) starches, RDS content of native as well as ultrasonicated

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starches increased significantly (P ˂ 0.005) and ranged between 60.5-78.5%, 62.4-80.3%, and 67.8-81.4%, for native, T 15 and T 30, respectively. SDS content of cooked starches

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decreased significantly (P ˂ 0.005) with increasing ultrasonication durations, in addition, it was lower for cooked starches as compared to their raw counterparts. SDS content varied from 18.5 to 35.4% and 16.3 to 29.1%, for T 15 and T 30, respectively. RS content decreased abruptly after gelatinization (cooked starches) of different cereal starches, whereas it increased significantly (P ˂ 0.05) with an increase in ultrasonication durations. RS content for native, 15 min sonicated and 30 min sonicated starches ranged between 0.51.8%, 1.2-2.2%, and 2.3-3.1%, respectively for cooked starches. Rice and barley showed the highest and lowest RS. The size of the granule may affect the digestibility of starch as the smallest granule sized starch i. e., rice, exhibited higher digestibility rate. As granule size

ACCEPTED MANUSCRIPT increases, the surface area decreased for specific volume subsequently, the chances of an enzymatic attack on substrate decreased. 3.6. Rheological properties Fig. 4. shows the changes recorded in the rheological properties after the starches subjected to sonication. From the rheological data of native starches, it was concluded that barley starch has the highest G′ (4930 Pa), G′′ (711 Pa) values at 90º C followed by maize, rice and

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wheat starches. Higher values of G′ than G′′ showed the predominance of solid/elastic

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behavior. During cooling, G′ and G′′ values of starch pastes increased ranging from 1960 to

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6540 Pa and 305 to 821 Pa at 10 º C (no hold) and after 30 min of holding at 10 ºC, the G′ and G′′ values ranged from 1920 to 6310 Pa and 249 to 806 Pa, respectively. The rise in

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moduli may be due to the retrogradation in starch pastes. Ultrasound treatment enhances the degradation of starch granules by cavitational forces and therefore granule becomes more

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permeable to water during the heating phase. The values of G′ and G′′ increases on 15 min of ultrasonic treatment revealed that there is more disruption of starch granules with

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increasing ultrasound power and the crystalline region of the molecule become weakened, therefore causing the molecules to entrapped more water which leads to higher viscosity.

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The values of G′ and G′′ decrease with increasing the duration of ultrasonic treatment for 30 min. This may be attributed to the severe damage to the starch granules under the shear

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forces induced by the ultrasound treatment and thus the straightening out of amylose molecules occurs, the shear action within the fluid layers get reduced, which contribute to

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the decrease of viscosity. When there is a rise in temperature, the molecules absorb translational energy and gradually cease to retain their hydration, which causes the lowering

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of viscosity [28]. The mechanical treatment of starch suspensions by ultrasonic treatment damaged the crystalline structure and hydrogen bonds of starch molecules, their structure becomes loose and disruption occurs more easily. Therefore, it may be concluded that the starch pastes showed shear thinning behaviour, as G′ > G′′, typical characteristic of pseudoplastic fluids i.e. starches showing their highly elastic nature than viscous behaviour. The ultrasonicated starches could be used to achieve a high apparent viscosity in food industry. The trends of gel strength are illustrated by differences in loss tangent (tan δ) as shown in Fig. 5. The strength of gel is related to the tan δ, the lower the value of tan δ, the higher the

ACCEPTED MANUSCRIPT strength of gel. The results revealed that there was slight variation for tan δ and its value was not changed by sonication of starches, except for starches treated for 30 min, which showed lower tan δ values compared to the control and starches ultrasonicated for 15 min. Therefore, it may be concluded that the starches treated for 30 min or higher duration of ultrasonication showed higher strength of gel behaviour. 4. Conclusion

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Ultrasonication is a physical treatment and presents a novel technique that modifies and

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improves the composition, structure and properties of food products. It can be effectively

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utilized in the food industry for diverse starch related food applications to obtain the desired food products with enhanced product yield, shortened processing time, environment-

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friendly and less energy consumption. Starch added to the food products as the functional ingredient as it related to the characteristic properties of the food. Therefore, ultrasonication

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can be applied to create and improve the functionality and stability of starch-based products. In this study, ultrasonication increased the swelling power and solubility of starches from

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different sources. SEM and particle size distribution revealed that ultrasonication caused only surface and microstructural changes in the physical geometry of starch granules with

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minimum effect on their overall integrity. The in vitro digestibility of raw ultrasonicated starches displayed an increase of RDS and RS content, which was attributed to granular

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size, degree of crystallinity, physicochemical properties of starches and changes in the starch structure. In contrary, gelatinized starch suspensions showed a considerable increase

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of RDS and RS content may be caused by the effect of ultrasonic waves due to which shortchained amylose molecules are formed. The gelatinized starch suspensions are particularly

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utilized in the preparation of various food products such as porridges, sauces, and pasta.

Acknowledgements The authors would like to acknowledge support granted through the UGC-BSR Fellowship Scheme, UGC, New Delhi for financial support. References [1] R. Carmona-Garcıa, L.A. Bello-Perez, A. Aguirre-Cruz, A. Aparicio-Saguilan, J. Hernandez-Torres, J. Alvarez-Ramirez, Effect of ultrasonic treatment on the

ACCEPTED MANUSCRIPT morphological, physicochemical, functional, and rheological properties of starches with different granule size, Stach/Star. 68 (2016) 972-979. [2] J,Y. Zuo, K. Knoerzer, R. Mawson, S. Kentish, M. Ashokkumar, The pasting properties of sonicated waxy rice starch suspensions, Ultrasonic. Sonochem. 16 (2009) 462-468. [3] M. Sujka, J. Jamroz,Ultrasound-treated starch: SEM and TEM imaging, and functional behaviour, Food Hydrocoll. 31 (2013) 413-419.

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[4] A. Patist, D. Bates, Ultrasonic innovations in the food industry: from the laboratory to

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commercial production, Innovative Food Sci. Emerg. Technol. 9 (2008) 147-154.

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[5] D. Knorr, M. Zenker, V. Heinz, D.U. Lee, Applications and potential of ultrasonics in food processing, Trends in Food Sci. Technol. 15 (2004) 261-266.

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[6] P. Tomasik, M.F. Zaranyika, Non conventional methods of modification of starch, Advances in Carbohyr. Chem. Biochem. 51 (1995) 243-320.

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[7] T.S. Awad, H.A. Moharram, O.E. Shaltout, D. Asker, M.M. Youssef, Applications of ultrasound in analysis, processing and quality control of food: a Review, Food Res. Int.

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48 (2012) 410-427.

[8] K.S. Sandhu, N. Singh, N.S. Malhi, Physicochemical and thermal properties of starches

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separated from corn produced from crosses of two germ pools, Food Chem. 89 (2005) 541-548.

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[9] S. Singh, N. Singh, N. Isono, T. Noda, Relationship of granule size distribution and amylopectin structure with pasting, thermal, and retrogradation properties in wheat

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starch, Journal of Agri. Food Chem. 58 (2010b) 1180-1188. [10] N.S. Sodhi, N. Singh, Morphological, thermal and rheological properties of starch

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separated from rice cultivars grown in India, Food Chemi. 80 (2003) 99-108. [11] T. Vasanthan, R.S. Bhatty, Starch purification after pin milling and air classification of waxy, normal and high amylose barleys, Cereal Chem. 72 (1995) 379-384. [12] L.W. Leach, L.D. McCowen, T.J. Schoch , Structure of the starch granule. Swelling and solubility patterns of various starches, Cereal Chem. 36 (1959) 534-544. [13] H. Kaur, B.S. Gill, B.L. Karwasra, In vitro digestibility, pasting and structural properties of starches from different cereals, Int. Jx. Food Prop. 21 (2018) 85-100.

ACCEPTED MANUSCRIPT [14] K. Shevkani, N. Singh, S. Singh, A.W. Ahlawat, A.M. Singh, Relationship between physicochemical and rheological properties of starches from Indian wheat lines, Int. J. Food Sci. Technol. 46 (2011) 2584-2590. [15] H.N. Englyst, S.M. Kingman, J.H. Cummings, Classification and measurement of nutritionally important starch fractions, Euro. J. Clinic. Nutri. 46 (1992) S33-S50. [16] R. Hoover, Composition, molecular structure, and physicochemical properties of tuber

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and root starches: A review, Carbohydr. Poly. 45 (2001) 253-267.

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[17] T. Gaillard, P. Bowler, Morphology and composition of starch. In T. Gaillard (Ed.),

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Starch properties and potential, 1987, (pp. 55-78). Chichester: Wiley. [18] A.R. Jambrak, Z. Herceg, D. Subaric, J. Babic, M. Brncic, S.R. Brncic, Ultrasound

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effect on physical properties of corn starch, Carbohydr. Poly. 79 (2010) 91-100. [19] J. Zhu, L. Li, L. Chen, X. Li, Study on supramolecular structural changes of ultrasonic

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treated potato starch granules, Food Hydrocoll. 29 (2012) 116-122. [20] J.E. Fannon, J.M. Shull, J.N. BeMiller, Interior channels of starch granules, Cereal

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Chem. 70 (1993) 611-613.

[21] Q. Huang, L. Li, X. Fu, Ultrasound effects on the structure and chemical reactivity of

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cornstarch granules, Starch/Stark. 59 (2007) 371-378. [22] J. Zheng, Q. Li, A. Hu, L. Yang, J. Lu, X. Zhang, Dualfrequency ultrasound effect on

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structure and properties of sweet potato starch, Starch/Stark. 65 (2013) 621-627. [23] J. Man, Y. Yang, C. Zhang, X. Zhou, Y. Dong, F. Zhang, Structural changes of high-

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amylose rice starch residues following in vitro and in vivo digestion, J. Agri. Food Chemi. 60 (2012) 9332-9341.

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[24] J.J. Van Soest, H. Tournois, D. de Wit, J.F. Vliegenthart, Short-range structure in (partially) crystalline potato starch determined with attenuated total reflectance Fouriertransform IR spectroscopy, Carbohydr. Res. 279 (1995) 201-214. [25] P. Ispas-Szabo, F. Ravenelle, I. Hassan, M. Preda, M.A. Mateescu, Structure–properties relationship in cross-linked high-amylose starch for use in controlled drug release, Carbohydr. Res. 323 (2000) 163-175. [26] K.S. Sandhu, S.T. Lim, Digestibility of legume starches as influenced by their physical and structural properties, Carbohydr. Poly. 71 (2008) 245-252.

ACCEPTED MANUSCRIPT [27] C.F. Pamela, A.R. Cesar, C. Gerardo, J.V. Eduardo, A.B. Luis, A. Jose, In vitro digestibility of ultrasound treated corn starch, Starch/Stark. 69 (2017) DOI 10.1002/star.201700040. [28] N.A. Camino, O.E. Perez, A.M.R. Pilosof, Molecular and functional modification of hydroxypropylmethylcellulose by high-intensity ultrasound,

Food Hydrocoll. 23

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(2009) 1089-1095.

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Legends to figures 1. Scanning electron micrography of native and ultrasonicated starches (A) NMS, (B) MSS-15, (C) MSS-30, (D) NWS, (E) WSS-15, (F) WSS-30 2. X-ray diffraction patterns of native and ultrasonicated starches 3. FTIR spectroscopy of native and ultrasonicated starches: (A) Wheat starch, (B) Rice

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different cereal starches from wave numbers 800 to 1200 cm-1.

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starch, (C) Maize starch (D) Barley starch and (E) Deconvoluted FTIR spectra of

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4. Storage modulus of sonicated and unsonicated starch pastes (A) Storage modulus of native and ultrasonicated starches for 15 min: (A) Wheat starch (B) WSS-15 (C) Rice starch (D) RSS-15 (E) Maize starch (F) MSS-15 (G) Barley starch (H) BSS-15

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(B) Storage modulus of native and ultrasonicated starches for 30 min: (A) Wheat starch (B) WSS-30 (C) Rice starch (D) RSS-30 (E) Maize starch (F) MSS-30 (G) Barley starch

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(H) BSS-30

5. Loss tangent (tan δ) of native and ultrasonicated starch pastes (A) Wheat starch, (B) Rice

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starch, (C) Maize starch (D) Barley starch

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FIGURE 5

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Table 1. Granular distribution of starches from native and ultrasonicated starches C-type (˂5.5µm)

NWS WSS-15 WSS-30 NRS RSS-15 RSS-30 NMS MSS-15 MSS-30 NBS BSS-15 BSS-30

76.42de±1.08 77.16d±1.74 77.08d±1.32 47.88f±0.57 31.43g±1.02 25.99h±0.67 74.3e±1.48 79.25cd±1.17 73.15ef±1.62 84.55a±2.04 82.61b±2.35 83.56ab±1.83

19.6fg±0.43 19.98f±1.85 19.6fg±0.74 32.99c±1.51 43.6b±0.16 47.77a±0.78 23.84e±1.29 19.89±1.54 26.12d±1.14 13.2i±1.27 15.36h±0.59 14.12hi±0.62

3.98d±0.16 2.86e±0.14 3.32de±0.22 19.13c±0.45 24.97b±0.37 26.24a±0.18 1.86h±0.47 0.86hi±0.08 0.73i±0.15 2.25g±0.61 2.03gh±0.32 2.32fg±0.51

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Solubility (%)

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NWS 11.56f±0.30 8.56e±0.19 WSS-15 13.25de±0.43 9.77cd±0.15 b WSS-30 17.42 ±0.29 11.48b±0.18 NRS 12.30e±0.75 6.77gh±0.18 cd RSS-15 14.06 ±0.20 8.29f±0.18 a RSS-30 18.18 ±0.21 9.59d±0.21 NMS 10.29gh±0.14 9.30de±0.20 c MSS-15 14.54 ±0.15 11.51b±0.18 MSS-30 17.41b±0.17 13.79a±0.13 h NBS 9.31 ±0.19 5.97h±0.18 BSS-15 11.18fg±0.21 7.28g±0.21 c BSS-30 14.46 ±0.19 10.11c±0.21 Means ± SD with different superscripts in columns differ significantly (p < 0.05; n = 3).

ACCEPTED MANUSCRIPT Table 3. Structural characteristics of different cereal starches as determined by XRD and FTIR. CI (%)

IR ratio 1047/1022 RDS (%) 32.0±0.56 0.8551±0.02 40.4±0.80 0.8580±0.01 44.3±0.40 1.0063±0.05 33.0±0.20 0.8635±0.04

IR ratio 1022/995 SDS(%) 0.9873±0.03 0.9408±0.02 0.9422±0.05 0.9449±0.03

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Means ± SD (n=3); CI: crystalline index; IR: infrared

Table 4. In vitro digestibility of native and ultrasonicated starches

RS(%)

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Raw Cooked Raw Cooked Raw Cooked h h c c e NWS 42.8 ±1.2 67.9 ±1.1 47.5 ±0.95 30.9 ±0.45 9.7 ±0.65 1.2d±0.71 g g d e d WSS-15 44.8 ±2.1 69.5 ±0.94 44.7 ±1.18 28.3 ±1.78 10.5 ±1.21 2.2bc±1.07 f WSS-30 48.3 ±1.14 74.6d±1.62 40.3g±2.07 22.5g±1.19 11.4c±2.08 2.9a±1.22 NRS 54.4c±0.67 78.5c±1.7 39.5g±0.87 21.0h±0.62 6.1i±0.27 0.5e±0.18 b b h j h RSS-15 55.7 ±1.21 80.3 ±1.35 37.5 ±2.18 18.5 ±1.33 6.8 ±1.09 1.2d±1.35 RSS-30 59.3a±1.47 81.4a±1.26 33.5i±1.12 16.3k±1.18 7.2h±1.32 2.3bc±1.97 f f e de g NMS 47.8 ±0.65 70.1 ±0.71 43.8 ±0.60 28.8 ±0.79 8.4 ±0.55 1.1d±0.12 MSS-15 49.5e±1.27 73.7e±1.14 41.6f±0.87 24.4f±2.41 8.9fg±1.13 1.9c±0.87 d c h i ef MSS-30 52.5 ±0.97 78.2 ±1.42 38.3 ±1.27 19.2 ±1.56 9.2 ±1.28 2.6ab±1.04 NBS 34.7k±0.75 60.5j±0.54 53.7a±0.45 37.7a±0.11 11.6c±1.20 1.8c±0.46 j i b b b BSS-15 36.6 ±1.13 62.4 ±1.07 51.0 ±1.47 35.4 ±1.08 12.4 ±1.79 2.2bc±0.76 BSS-30 41.8i±1.25 67.8h±1.21 45.0d±1.23 29.1d±0.78 13.2a±1.41 3.1a±0.84 Means ± SD with different superscripts in columns differ significantly (p < 0.05; n = 3). RDS: rapidly digestible starch; SDS: slowly digestible starch; RS: resistant starch

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Variety 3 13840.3** 10489.4** 3504.1** 7488.3** 1371.04** 43.42** Cooking 2 2399.2** 2967.9** 1889.5** 3695.4** 132.1** 186.4** Interaction 6 26.81** 126.3** 21.04** 93.1** 3.51* 1.85 df, degree of freedom: * p˂0.05; ** p˂0.005; RDS: rapidly digestible starch; SDS: slowly digestible starch; RS: resistant starch

ACCEPTED MANUSCRIPT Highlights  Effect of ultrasonication on different starches was evaluated. 

There is a formation of cracks, depressions and pores on the surface of starch granules observed under SEM indicating cavitation in starch granules due to ultrasonication.



The rheological properties showed an increase in G′ and G′′ for 15 min ultrasonication and decreased with 30 min ultrasonication.

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In vitro digestibility of raw ultrasonicated starches displayed an increase of RDS and RS

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content while SDS content decreased with increase in ultrasonication duration.

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