A novel starch from Pongamia pinnata seeds: Comparison of its thermal, morphological and rheological behaviour with starches from other botanical sources

A novel starch from Pongamia pinnata seeds: Comparison of its thermal, morphological and rheological behaviour with starches from other botanical sources

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Journal Pre-proofs A novel starch from Pongamia pinnata seeds: Comparison of its thermal, morphological and rheological behaviour with starches from other botanical sources Anil Kumar Siroha, Sneh Punia, Maninder Kaur, Kawaljit Singh Sandhu PII: DOI: Reference:

S0141-8130(19)37251-4 https://doi.org/10.1016/j.ijbiomac.2019.10.033 BIOMAC 13437

To appear in:

International Journal of Biological Macromolecules

Received Date: Revised Date: Accepted Date:

7 September 2019 26 September 2019 3 October 2019

Please cite this article as: A. Kumar Siroha, S. Punia, M. Kaur, K. Singh Sandhu, A novel starch from Pongamia pinnata seeds: Comparison of its thermal, morphological and rheological behaviour with starches from other botanical sources, International Journal of Biological Macromolecules (2019), doi: https://doi.org/10.1016/ j.ijbiomac.2019.10.033

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A novel starch from Pongamia pinnata seeds: Comparison of its thermal, morphological and rheological behaviour with starches from other botanical sources Anil Kumar Sirohaa*, Sneh Puniaa*, ManinderKaurb, & Kawaljit Singh Sandhuac aDepartment

of Food Science and Technology, Chaudhary Devi Lal University, Sirsa, India of Food Science and Technology, Guru Nanak Dev University, Amritsar, India cDepartment of Food Science and Technology, Maharaja Ranjit Singh Punjab Technical University, Bathinda, India

bDepartment

Keywords: Pongamia pinnata seed starch; physicochemical; dynamic shear; morphological; thermal properties

*Corresponding author Contact e-mail: [email protected]; [email protected]

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Abstract Pongamia pinnata seed (PPS) starch was studied for its physicochemical, thermal, rheological and morphological properties. As PPS starch is a novel starch, it was compared with corn, mung bean, potato, pearl millet and mango kernel starches. Peak, trough and final viscosity of PPS starch was found the lowest as compared to other starches. Plots of shear stress versus shear rate for starch pastes were plotted and fitted to Herschel-Bulkley model. Yield stress and consistency index value of starch pastes varied between 6.5-58.9 Pa and 1.4-10.6 Pa.s, respectively. During frequency sweep testing, G′ and G′′ values of starch pastes varied between 33-484 Pa and 18-71 Pa, PPSstarch paste had the lowest values. Transition temperatures (Tο, Tp, Tc) for PPS starch was 61.5, 72.1 and 82.9°C, respectively. Scanning electron microscopy of PPS starch showed small to large and round to oval shape starch granules with small pitches on their surface.

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1. Introduction Pongamia pinnata (L.) a multipurpose legume tree belongs to family leguminosae and subfamily papilionaceae. The tree is indigenous to the Indian subcontinent and south East Asia. The Pongamia pinnata tree is adaptive to Indian environmental conditions and grows widely in different regions. Common names of Pongamia pinnata include karanja (India), ki Pahang laut (Indonesia), Kacang kayu laut (Malayasia), and pongam oil tree/malva nut (English language) (Csurhes & Hankamer, 2010). The tree is medium sized, perennial and grows in the littoral regions of South Eastern Asia and Australia (Allen & Allen, 1981; Satyavati, Gupta, & Tandon, 1987). It has an extensive nitrogen fixing ability with high seed production (20,000 seeds/tree) (Belide, Sajjalaguddam, & Paladugu, 2010). It is a multipurpose tree which is used in producing medicine, fuel, fodder, manure, and insecticides (Pavela, 2009; Shivanna & Rajakumar, 2010). Medicinal uses of different parts of Pongamia pinnata tree has been reported by various workers (Prasad & Reshmi, 2003; Muthu, Ayyanar, Raja, & Ignacimuthu, 2006; Pavithra, Shivanna, Chandrika, Prasanna, & Gowda, 2010). Pongamia pinnata also contains various phytochemicals including flavonoid derivatives, sesquiterpine, steroids, amino acid derivatives, disaccharides, fatty acids and esters (Al Muqarrabun, Ahmat, Ruzaina, Ismail, & Sahidin, 2013). Starch from conventional sources has been studied over the years. In recent years, however, starch from non-conventional sources such as mango kernel seed (Kaur, Punia, Sandhu, & Ahmed, 2019; Bello-Perez, Gonzalez-Soto, Sanchez-Rivero, Gutierrez-Meraz, & VargasTorres, 2006), tamarind kernel (Kaur & Singh, 2016), and banana (Bello-Perez, Gonzalez-Soto, Sanchez-Rivero, Gutierrez-Meraz, & Vargas-Torres, 2006) starches has been explored. The reason for exploring the starch from non-conventional sources is to find starch with unique properties which can be used in place of modified starches in food industries for formulating various food products.

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Pongamia pinnata seeds (PPS) has been widely studied for its medicinal properties; however, to the best of our knowledge, starch from PPS has not been previously reported. Therefore, it would be beneficial to explore PPS starch as it might possess some unique properties. The study thus aimed to investigate the physicochemical, pasting, thermal, rheological and morphological properties of starch from PPS seeds. Additionally, properties of PPS starch were compared with corn, mung bean, potato, pearl millet, and mango kernel starches. 2. Materials and methods 2.1 Materials The seeds were collected from Pongamia pinnata (L.) tree (Figure 1) grown at the campus of Chaudhary Devi Lal University, Sirsa, India. Pongamia pinnata variety was wild type while corn, mung bean, potato, pearl millet and mango kernel were taken from cultivars i.e. cv. Parbhat, cv. ML-5, cv. Kufri Ashoka, cv. HC-20 and cv. Dashehari. The chemicals and reagents Potassium iodide (Sigma-Aldrich, USA), Iodine resublimed (Qualigens, Mumbai, India), Hydrochloric acid (Rankem, New Delhi, India), Potassium hydroxide (CDH, New Delhi, India), Sodium metabisulphite (CDH, New Delhi, India)] used were of analytical grade. 2.2 Starch isolation Fully ripen seeds of Pongamia pinnata were collected and their outer covering was removed manually. Seeds were then dipped in sodium metabisulphite (0.1%) for 2 h. Further, grinding, sieving and centrifugation were done following the method described by Sandhu and Singh (2005). After 2 h, the steep water was drained off and grains were ground in laboratory grinder (Maxie Plus, New Delhi, India). About 250 g of steeped seeds were ground with 250 ml of distilled water. The ground slurry was passed through 0.250, 0.150, 0.100, 0.075, 0.045 mm sieve. The starch-protein slurry was then allowed to stand for 4-5 h. The supernatant was removed by suction and the settled starch layer was re-suspended in distilled water and centrifuged in wide mouthed cup centrifuge (Remi, New Delhi, India) at 605 g for 10 min and

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the upper non-white layer was scrapped off. The white layer was re-suspended in distilled water and re-centrifuged 3-4 times. The starch was then collected and dried in an oven (NSW-143, New Delhi, India) at 45 °C for 12 h. Starches from corn, mungbean, pearl millet were isolated followed the method Sandhu and Singh (2005) while potato starch was isolated by following the method described by Alvani, Qi, Tester, & Snape (2011). 2.3 Amylose content, swelling power and solubility The amylose content of starches was determined by using the method described by Williams, Kuzina, & Hlynka (1970). Starch (0.020 g) was thoroughly mixed with 10 ml of 0.5 mol/L KOH. The dispersed sample was transferred to volumetric flask (100 ml) and diluted to the mark with distilled water. An aliquot of test starch solution (10 ml) was pipetted into volumetric flask (50 ml) and 5 ml of 0.1 mol/L HCl was added followed by the 0.5 ml of iodine reagent. The volume was diluted to 50 ml and the absorbance was measured at 625 nm in a spectrophotometer (Systronics, Ahmadabad, India). The measurement of the amylose was determined in triplicate from a standard curve developed using amylose and amylopectin blends. The swelling power and solubility of starches were determined by following the method described by Leach, McCowen, & Schoch (1959). Starch (1 g) was added to distilled water (99 ml) and heated to 90°C for 1 h. The heated samples were cooled rapidly in ice water bath for 1 min, equilibrated at 25°C for 5 min and then centrifuged at 605 g for 30 min. The supernatants were drained into pre-weighed moisture dishes, evaporated to dryness in a hot air oven at 100°C and cooled to room temperature in a desiccator prior to reweighing.

2.4 Pasting properties

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The pasting properties of starches were determined using in-build starch cell of Modular Compact Rheometer (Model-52, Anton Paar, Austria). Starch slurries (1.2 g starch in 13.8 g distilled water) were held at 50oC for 1 min and then heated from 50 to 95oC at a heating rate of 6oC/ min, held for 2.7 min, cooled to 50oC at the same rate and again held at 50oC for 2 min. Each sample was analyzed in triplicate. Peak viscosity, breakdown, setback, final viscosity and pasting temperature were obtained from the pasting graph. 2.5 Morphological properties Scanning electron micrographs were taken by scanning electron microscope (JSM-6100, Jeol, USA). Starch samples were suspended in ethanol to obtain a 1% suspension. One drop of the starch-ethanol solution was applied to an aluminium stub using double-sided adhesive tape. An accelerating potential of 10 kV was used during micrography. 2.6 X-ray diffraction X-ray pattern of PPS starch was recorded with a wavelength of 0.154 nm using X-ray diffractometer (Rigaku Miniflex, Japan). The diffractometer was operated at 45 kV and 40 mA. Diffractograms were acquired at 25oC over a 2θ range of 4-40 with a step size of 0.02 and sampling interval of 10 s. 2.7Rheological properties 2.7.1 Dynamic properties A small amplitude oscillatory rheological measurement was made for starch with a Modular Compact Rheometer (Model-52, Anton Paar, Austria) equipped with parallel plate system (0.04 m diameter). The gap size was set at 1000 m. Linear viscoelastic range (LVR) for strain and angular frequency was measured using starch slurry (6%, w/w) and manually stirred and then heated at 85oC in a water bath followed by 3 min stirring. The sample was allowed to cool at room temperature and then loaded on the ram of rheometer. LVR measurement for strain, angular frequency and temperature (10 rads & 25°C) were remain 6

constant and strain was varied while to detect LVR for angular frequency, strain and temperature (2% & 25%) were constant only angular frequency was varied. From the LVR 2% strain and 10 rad/s angular frequency was used for all determinations. The dynamic rheological properties, such as storage modulus (G′), loss modulus (G″) and loss factor (tan ) were determined for starches. Starch suspensions of 6% (w/w) concentration were loaded onto the ram of the rheometer and covered with a thin layer of low-density silicon oil (to minimize evaporation losses). The starch samples were subjected to temperature sweep testing and were heated from 45 to 95oC at the rate of 2oC/min. For frequency sweep measurement, the starch slurry (6%, w/w) was prepared and manually stirred and then heated at 85oC in a water bath followed by 3 min stirring. The sample was allowed to cool at room temperature and then loaded on the ram of rheometer. Frequency sweep tests from 0.1 to 100 rad/s were performed at 25oC. The storage modulus (G′), loss modulus (G′′), and loss tangent (tan ) were derived at 25oC. 2.7.2 Steady shear measurement Steady shear properties of starch pastes were determined by following the method of Park, Chung, & Yoo (2004) with slight modifications. The sample preparation method has been described in frequency sweep measurement. The sample (6%) was sheared continuously from 1 to 1000 s-1. In order to describe the variation in the rheological properties of samples under steady shear, the data was fitted to Herschel-Bulkley model: σ= σo + K(γ̇)n where σ is the shear stress (Pa), σo is the yield stress, γ̇ is the shear rate (s-1), K is the consistency index (Pa.sn), n is the flow behaviour index (dimensionless). 2.8 Thermal properties Thermal characteristics of PPS starch were studied by using a Differential Scanning Calorimeter (DSC) (Mettler Toledo, Switzerland) equipped with a thermal analysis data 7

station. Starch (3.5 mg, dry weight) was loaded into a 40 ml capacity aluminium pan (Mettler, ME-27331) and distilled water was added with the help of Hamilton microsyringe to achieve a starch-water suspension containing 70 g/100 g water. Samples were hermetically sealed and allowed to stand for 1 h at room temperature before heating in DSC. The DSC analyzer was calibrated using indium and an empty aluminium pan was used as reference. Sample pans were heated at a rate of 5 °C/min from 40 to 100 °C. Thermal transitions of starch samples were defined as To (onset), Tp (peak of gelatinization) and Tc (conclusion), and ΔHgel was referred to enthalpy of gelatinization. Enthalpies were calculated on starch dry basis. These were calculated automatically. The gelatinization temperature range (R) and peak height index (PHI), was calculated as 2(Tp-To) and ΔH/(Tp-To), respectively. 2.9 Statistical analysis The data reported in the tables were carried out in triplicate and they were subjected to oneway analysis of variance (ANOVA) using Minitab Statistical Software version 15 (Minitab, Inc., State College, USA). 3. Results and discussion 3.1 Amylose content (%), swelling power (g/g) and solubility (%) of starches The amylose content of starches from different botanical sources is shown in Table 1. For PPS starch, the amylose content was 17.9%. The amylose content of PPS starch was compared with starches from other botanical sources and mung bean starch showed the highest (27.9%) whereas the lowest value was observed for mango kernel starch (11.5%). Swelling power of starches varied between 15.6-28.8 g/g (Table 1). PPS starch showed the value of 24.4 g/g. The highest swelling power, however, was observed for potato starch. The solubility of starches from different botanical sources varied from 11.4 to 26.5%, the highest was observed for PPS starch. Swelling power and solubility provide an evidence of the magnitude of interaction between starch chains within the amorphous and crystalline domains 8

and is influenced by the ratio of amylose to amylopectin (Blazek & Copeland, 2008) and the way in which amylose and amylopectin are arranged inside the granule affect the swelling and solubility of the starch (Jan, Saxena, & Singh, 2016). 3.2 Pasting properties Pasting properties of starches from different botanical sources are reported in Table 2. Starch suspensions from different botanical sources showed gradual increase in viscosity during heating followed by a decrease and then again increase in viscosity upon cooling. Peak viscosity (PV) of starches ranged between 1306-3328mPa.s, the highest value for potato starch while the lowest value for PPS starch was observed. Rincon-Londono, Vega-Rojas, ContrerasPadilla, Acosta-Osorio, & Rodríguez-García, (2016) reported series of morphological changes in starch granules that takes place during pasting properties of maize starch and defined PV as an indicator of end of the stable hydrogel formation with characteristic morphology (interconnected micro fibrils). Low PV of PPS starch might be due to less stable hydrogel as compared to other starches.The breakdown value of starch paste is defined as difference between the PV and trough viscosity (TV) of starch paste. Breakdown viscosity of starches varied between 142-631 mPa.s, the highest value was observed for potato starch. Final viscosity (FV) of PPS starch was 1972 mPa.s, which was the lowest in comparison toother starches. Pasting temperature (PT) of PPS starch was found the highest, which indicates its more time requirement for cooking as compared to starches from other botanical sources studied. 3.3 Morphological properties Scanning electron micrographs (SEM) of PPS starch are shown in Fig. 2. SEM plays an important role in the understanding of granular structure of starches. Size and shape of starch granules from PPS varied from small to large and round to oval, respectively. Small pitches were also observed on the surface of starch granules. SEM for starches from other botanical 9

sources are not shown as they are widely reported elsewhere. Sandhu, Singh, & Kaur (2004) reported starch granules varying from small to large and oval to polyhedral for different corn types. For mung bean starches, large oval to small round shape granules with smooth surface have been reported (Kaur, Sandhu, Singh, & Lim, 2011). The potato starch granules varied from large to small in size, oval and round in shape (Xia, Gou, Zhang, Li, & Jiang, 2018) and pearl millet starch showed granule size and shape from small to large, spherical and polygonal (Sandhu & Siroha, 2017). Kaur et al. (2004) reported that mango kernel starch granules varying in size and shape from small to large and oval to elliptical. Starch granule size has been reported to affect its physicochemical properties, such as gelatinization and pasting, enzyme susceptibility, crystallinity and solubility (Lindeboom, Chang, & Tyler, 2004). 3.4 X-ray diffraction The crystalline pattern of PPS starch as determined by their X-ray diffractions is shown in Fig. 3. On the basis of X-ray diffraction, crystal structure of starch is of three type’s i.e. A, B, and C. Cereal starch, which consists of A-type starch, has strong diffraction peaks at 2 values (15o, 17o, 18o, and 23o). B-type starch, which is present in tubers and amylose-rich carbohydrates, has one strong diffraction peak (17o) and weak diffraction peaks at 2 values (20o, 22o, and 24o). C-type starch, which is a mixture of both A and B-type patterns, is mainly present in legumes (Zobel, 1988; Liu, Wu, Chen, & Chang, 2009). PPS starch showed A-type diffraction patterns with peaks at 15o, 17o, 18o and 23o (2). Type of X-ray diffraction patterns of starches from other botanical sources studies are well known so they are not shown. Differences in diffraction patterns may be due to different growth conditions and maturity of the parent plant at the time of harvest, biological origin, amylose and amylopectin content (Zhou, Wang, Zhao, Fang, & Sun, 2010). 3.5Rheological properties 3.5.1 Dynamic shear properties 10

Significant (p<0.05) differences in the rheological properties of starch suspensions from different botanical sources during heating were observed (Table 3). For all starches, G′ and G′′ increased progressively during heating. G′ value of starches ranged between 40-700 Pa, the highest and the lowest values were observed for potato and PPS starch, respectively. All starches studied showed the values for G′′ less than G′. tan δ (G′′/G′) for all the starches studies was less than 1 indicating their elastic behaviour. The breakdown in G′, which is the difference between peak G′ at TG′ (temperature at which G′ was maximum) and minimum G′ at 90°C was found the highest for pearl millet starch whereas it was found the lowest for PPS starch, which indicates its more thermal stability as compared to other starches studies. TG′ value of starches varied between 65.7-90.1°C, the highest value was observed for PPS starch. The variation in G', G'' and tan δ during heating cycle may be due to the difference in starch granule structures and amylose content of starches from different botanical sources (Svegmark & Hermansson, 1993). Fig.4 (A-B) and Table 4 show the change in G′, G′′ and tan δ as a function of frequency at 25°C for starch pastes. The magnitude of G′ and G′′ of all starch pastes increased with increase in ω. G′ and G′′ values of starch pastes varied between 33- 484 Pa and 18-71 Pa, the highest G′ and G′′ values were observed for mung bean and potato starch pastes, respectively. G′ values were found much higher than G′′ values at ω (0.1 to 100 rad/s), which shows viscoelastic behaviour of starch pastes. No cross over was observed between two modulii (G′ & G′′) showed that starch pastes were stable during the observed frequency range. The behaviour observed for the starch pastes were similar to those of typical weak gels. tanδ values smaller than 1 indicate elastic behavior, whereas those above 1 indicate viscous behaviour of starch pastes (Siroha & Sandhu, 2018; Punia, Siroha, Sandhu & Kaur, 2019a). Complex viscosity (η*) for all starch pastes decreased with increase in ω. The range for η* at 6.28 rad/s for starch

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pastes varied between 6.0-77.8 Pa.s, the highest and the lowest values were observed for mung bean and PPS starch. 3.5.2 Steady shear properties Steady shear properties of starch pastes are shown in Table 5. The experimental data of flow behaviour for starch pastes were fitted to Herschel-Bulkley model and yield stress (σo), flow behaviour index (n) and consistency index (K) were evaluated. σo, indicative of the minimum force required to initiate flow of starch paste varied between 6.5-58.9 Pa, the highest and the lowest value was observed for starch pastes from potato and PPS, respectively. K value of starch pastes ranged from 1.4 to 10.6 Pa.s, the highest value was observed for potato starch. n values of starch pastes were less than 1 (0.48 to 0.98), indicating shear thinning behaviour of starch pastes. To characterize fluids and semi fluids mostly n value is used; behaviour of pastes with n value of 1 indicates a newtonian fluid, n value of less than 1 show shear thinning, and n value of greater than 1 indicates a shear thinking fluid behaviour (Lee & Chang, 2015). Similar shear thinning behaviour was observed for native barley and sorghum starches (Punia, Siroha, Sandhu & Kaur, 2019b; Siroha, Sandhu & Punia, 2019). Bhandari, Singhal, & Kale (2002) attributed shear thinning behaviour to higher amount of breakage of the intra and inter molecular associative bonding system in starch network micelles due to shearing at high rates. 3.6 Thermal properties The result of thermal analysis for PPS starch is shown in Fig. 5. Transition temperatures (To, Tp & Tc) for PPS starch were 61.5, 72.1 and 82.9°C, respectively. Sandhu and Singh (2007) reported To, Tp and Tc of 65.6-69.0, 69.9-74.0 and 75.1-79.7°C, respectively for different corn cultivars while Kaur et al. (2011) observed To, Tp and Tc in the range of 63.8-69.1, 69.7-74.6 and 76.0-80.3°C, respectively for different mung bean cultivars. To, Tp, and Tc values for potato (60.1℃, 64.0℃, 86.4℃) (Xia et al., 2018), pearl millet (63.4-67.7, 69.3-71.6, 74.5-76.3) (Sandhu & Siroha, 2017) and mango kernel starches (73.4-76.3, 77.9-80.2, 83.0-85.7) (Kaur et

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al., 2004) have been reported. The lower gelatinization temperature of starch shows lesser energy requirement to initiate gelatinization of starch and vice versa. The Enthalpy of gelatinization (ΔHgel) reflects primarily the loss of molecular double-helicalorder (Cooke & Gidley, 1992). ΔHgel, PHI and R values for PPS starch were 10.60 (J/g), 1.0 and 21.1, respectively. ΔHgel value for corn (11.2-12.7J/g) (Sandhu & Singh, 2007), mung bean (8.910.3J/g) (Kaur et al., 2011), potato (19.7J/g) (Xia et al., 2018), pearl millet (10.6-12.4 J/g) (Sandhu & Siroha, 2017) and mango kernel starches (12.0-13.2 J/g) (Kaur et al., 2004) have been reported. 3.7 Conclusions PPS starch showed significant (p<0.05) differences in physicochemical, thermal, rheological and morphological properties in comparison to those from other botanical sources studied. PPS starch showed the lowest pasting parameters (except pasting temperature), G′ and G′′ values during temperature sweep and frequency sweep testing, σo (steady shear properties) in comparison to starches from other botanical sources studied. PPS starch showed small to large and round to oval shape granules with small pitches on their surface. X-ray diffraction pattern of PPS starch was A-type with diffraction peaks at 15°, 17° and 23° (2θ). However, further studies on digestibility properties, molecular weights of starch fractions, chain lengths, and modified starch properties of PPS starch needs to be carried out so that this unique and novel starch can be explored further for its utilization in food and non-food applications.

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Sandhu, K. S., & Singh, N. (2007). Some properties of corn starches II: Physicochemical, gelatinization, retrogradation, pasting and gel textural properties. Food Chemistry, 101(4), 1499-1507. Sandhu, K. S., & Siroha, A. K. (2017). Relationships between physicochemical, thermal, rheological and in vitro digestibility properties of starches from pearl millet cultivars. LWTFood Science and Technology, 83, 213-224. Sandhu, K. S., Singh, N., & Kaur, M. (2004). Characteristics of the different corn types and their grain fractions: physicochemical, thermal, morphological, and rheological properties of starches. Journal of Food Engineering, 64(1), 119-127. Satyavati, G.V., Gupta, A.K., & Tandon, N. (1987). Medicinal plants of India, vol. II. Indian Council of Medical Research, New Delhi, pp. 490. Shivanna, M. B., & Rajakumar, N. (2010). Ethno-medico-botanical knowledge of rural folk in Bhadravathi taluk of Shimoga district, Karnataka. Indian Journal of Traditional Knowledge, 9, 158-162. Siroha, A. K., & Sandhu, K. S. (2018). Physicochemical, rheological, morphological, and in vitro digestibility properties of cross-linked starch from pearl millet cultivars. International Journal of Food Properties, 21(1), 1371-1385. Siroha, A.K., Sandhu, K.S., & Punia, S. (2019). Impact of octenyl succinic anhydride (OSA) on rheological properties of sorghum starch. Quality Assurance and Safety of Crops & Foods, 11, 221-229. Svegmark, K., & Hermansson, A. M. (1993). Microstructure and rheological properties of composites of potato starch granules and amylose: a comparison of observed and predicted structures. Food Structure, 12, 181-193. Williams, P. C., Kuzina, F. D., & Hlynka, I. (1970). Rapid colorimetric procedure for estimating the amylose content of starches and flours. Cereal Chemistry, 47, 411-421. Xia, T., Gou, M., Zhang, G., Li, W., & Jiang, H. (2018). Physical and structural properties of potato starch modified by dielectric treatment with different moisture content. International journal of biological macromolecules, doi:10.1016/j.ijbiomac.2018.06.149 Zhou, H., Wang, J., Zhao, H., Fang, X., & Sun, Y. (2010). Characterization of starches isolated from different Chinese Baizhi (Angelica dahurica) cultivars. Starch‐Stärke, 62(3‐4), 198-204. Zobel, H. F. (1988). Starch importance. Starch‐Stärke, 40(1), 1-7.

crystal

transformations

and

their

industrial

16

17

(A)

(B)

Figure 1(A) Pongamia pinnata tree; (B) Pongamia pinnata seeds

Figure 2 Scanning electron micrographs of Pongamia pinnata seed starch

18

Figure 3 X-ray diffraction patterns of Pongamia pinnata seed starch

19

Figure 4(A) Angular frequency dependence of G′ at 25 °C for different starches; (B)Angular frequency dependence of G′′ at 25 °C for different starches A-Pongamia pinnata seed; B-Corn; C-Mung bean; D-Potato; E-Pearl millet; F-Mango kernel

Figure 5 DSC endotherms of gelatinization of Pongamia pinnata seed starch 20

Table 1 Amylose content, swelling power and solubility of starches Starch

Amylose content (%)

Swelling power (g/g)

Solubility (%)

PPS

17.9±0.3c

24.4±0.6d

26.5±0.6e

Corn

20.6±0.6d

17.3±0.4b

19.4±0.6c

Mung bean

27.9±0.3e

15.6±0.5a

25.2±0.4d

Potato

21.6±0.5d

28.8±0.7e

15.0+0.2b

Pearl millet

14.8±0.2b

16.9±0.3b

11.4±0.1a

Mango kernel

11.5±0.3a

18.6±0.5c

14.8±0.3b

Means followed by same superscript within a column do not differ significantly(p < 0.05). PPS: Pongamia pinnata seed, Mean (±standard deviation) of triplicate analysis.

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Table 2 Pasting properties of starches Starch

PV (mPa.s)

BV (mPa.s)

TV (mPa.s)

SV (mPa.s)

FV (mPa.s)

PT (ºC)

PPS

1306±14a

302±12c

1004±17a

968±11d

1972±17a

77.6±0.3d

Corn

1765±18c

468±17d

1297±14c

937±14c

2234±20c

74.1±0.2c

Mung bean

1879±20d

201±10b

1678±19d

1788±20e

3466±25e

74.9±0.2c

Potato

3328±26f

631±14e

2697±21f

806±12b

3503±30f

65.6±0.3a

Pearl millet

1723±24b

478±13d

1245±19b

769±11a

2014±28b

71.7±0.4b

Mango 1972±20e 142±11a 1830±16e 1139±11f 2969±30d 77.1±0.2d kernel Means followed by same superscript within a column do not differ significantly(p < 0.05). PPS: Pongamia pinnata seed, Mean (±standard deviation) of triplicate analysis.

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Table 3 Rheological properties of starches during heating Starch

Peak G′ (Pa)

Peak G′′ (Pa)

Breakdown in G′(Pa) (Peak G′Value of G′ at 90ºC)

tanδ (G′′/ G′)

TG′ (°C) (Temperature at which G′ is maximum)

PPS

40±2a

18±1a

--

0.44d

90.1±0.5e

Corn

160±6b

85±2c

26±3a

0.52e

85.1±0.3d

Mungbean

433±8d

100±4e

176±7c

0.23c

75.1±0.5b

Potato

700±15f

152±5f

307±5d

0.21c

65.7±0.3a

Pearl millet

592±11e

90±3d

431±4e

0.15a

80.1±0.3c

Mango 382±9c 76±2b 111±3b 0.19b 80.0±0.2c kernel Means followed by same superscript within a column do not differ significantly (p < 0.05). PPS: Pongamia pinnata seed, Mean (±standard deviation) of triplicate analysis.

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Table 4 Storage modulus (G′), loss modulus (G′′), tan δ and complex viscosity (η*) at 6.28 rad/s for starches at 25 ºC Starch

G′ (Pa)

G′′ (Pa)

tan δ

Complex viscosity η* (Pa.s)

PPS

33±1a

18±0.9a

0.5c

6.0±0.2a

Corn

454±7d

45±4b

0.1a

72.7±1d

Mung bean

484±8e

66±3d

0.1a

77.8±2e

Potato

223±6b

71±4e

0.3b

37.3±3b

Pearl millet

256±8c

46±3b

0.1a

41.4±2c

Mango kernel

227±5b

58±3c

0.2b

37.3±3b

Means followed by same superscript within a column do not differ significantly(p < 0.05). PPS: Pongamia pinnata seed, Mean (±standard deviation) of triplicate analysis.

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Table 5 Herschel Bulkey model fitted to starch pastes during steady shear rate Sample

R2

σο(Pa)

K(Pa.s)

n

PPS

6.5±0.2a

5.1±0.2e

0.55±0.009b

Corn

20.5±0.7b

4.5±0.1d

0.48±0.007a

0.99

Mung bean

36.6±0.6c

3.3±0.1c

0.71±0.008d

0.99

Potato

58.9±0.5e

10.6±0.2f

0.66 ±0.005c

0.99

Pearl millet

19.8±0.5b

2.6±0.1b

0.55±0.005b

0.99

Mango kernel

53.4±0.2d

1.4±0.2a

0.98±0.006e

0.99

0.99

Means followed by same superscript within a column do not differ significantly(p < 0.05). PPS: Pongamia pinnata seed, Mean (±standard deviation) of triplicate analysis.

25