- Email: [email protected]
Unripe mango kernel starch: Partial characterization
Journal Pre-proof Unripe mango kernel starch: partial characterization
Omar Patiño-Rodríguez, Edith Agama-Acevedo, Gonzalo Ramos-Lopez, Luis A. Bello-Pérez PII:
S0268-005X(19)31933-2
DOI:
https://doi.org/10.1016/j.foodhyd.2019.105512
Reference:
FOOHYD 105512
To appear in:
Food Hydrocolloids
Received Date:
22 August 2019
Accepted Date:
12 November 2019
Please cite this article as: Omar Patiño-Rodríguez, Edith Agama-Acevedo, Gonzalo Ramos-Lopez, Luis A. Bello-Pérez, Unripe mango kernel starch: partial characterization, Food Hydrocolloids (2019), https://doi.org/10.1016/j.foodhyd.2019.105512
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
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Unripe mango kernel starch: partial characterization
Omar Patiño-Rodríguez1,*, Edith Agama-Acevedo2, Gonzalo Ramos-Lopez3, and Luis A. Bello-Pérez2
1
CONACyT-Instituto Politécnico Nacional, CEPROBI, Km. 6.5 Carr. Yautepec-Jojutla
Col. San Isidro, Calle CEPROBI No. 8, Yautepec, Morelos, México. 2
Instituto Politécnico Nacional, CEPROBI, Km. 6.5 Carr. Yautepec-Jojutla Col. San
Isidro, Calle CEPROBI No. 8, Yautepec, Morelos, México. 3
Instituto Politécnico Nacional, CICATA Unidad Queretaro, Cerro Blanco 141, Queretaro,
México.
*Corresponding author: CONACyT-Instituto Politécnico Nacional, Centro de Desarrollo de Productos Bióticos (CEPROBI). Carretera Yautepec-Jojutla, Km. 6, calle CEPROBI No. 8. Yautepec, Morelos, México. C.P. 62731, Apartado Postal 24. Telephones: (735) 394 20 20, 394 18 96, Ext. 28 25 88. E-mail: [email protected]
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Abstract Although a rich source of polyphenols, starch and dietary fibre, unripe mango has been identified as a functional ingredient. The kernel of unripe mango is rich in starch and certain compounds such as non-starch polysaccharides (components of dietary fibre), polyphenols and lipids. The isolation of starch from unripe mango kernel can be an alternative to obtain non-conventional ingredients to diverse end-uses. The aim of this study was the isolation of starch from unripe mango kernel and its partial characterization. The isolated starch was studied in morphology with microscopic methods, X-ray diffraction, thermal properties, pasting profile, and in vitro digestibility. The starch granules were distinguished as oval and round- with a mean size of 50 m and some debris of lipids in the surface. The amylose content of the starch granule was 23 g/100 g and A-type diffraction pattern was observed. The temperature and enthalpy of gelatinization are similar to conventional starch as maize with a low tendency to retrogradation. The pasting profile of mango kernel starch was identified as typical of native starch with gel formation upon cooling. The in vitro enzymatic hydrolysis of mango kernel starch was different from that of conventional starches with slow digestion rate in the cooked sample. The starch from unripe mango kernel can be an alternative to starchy raw materials like as cereals or pulses in food and non-food applications.
Keywords: unripe mango; kernel; starch; characterization; in vitro digestibility.
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Introduction Mango is a climacteric fruit that is harvested at a physiologically mature green stage and allowed to ripen for industrial use (mango concentrate) and market (Evans, Ballen, & Siddiq, 2017). The pulp of unripe mango was used for starch separation, with a granule size between 5-10 µm, apparent amylose content of 31.1 %, the molecular weight of amylopectin 5.013 Mw x 108 g/mol, and gyration radius of 298 nm (Espinosa-Solis, Jane, & Bello-Perez, 2009). The industrial processing of ripe mango (12-15 °Brix) produces a concentrate and by-product, kernel and peel, respectively. With the objective to decrease pollution generated by the final deposition of the mango by-products, the use of mango kernel was proposed (Saeaurng, & Kuakpetoon, 2018). The main components of a mango kernel are starch and bioactive compounds such as phenolics, vitamins, minerals, as well as oil (Ashoush, & Gadallah, 2011). Starch of the mango kernel (in physiological maturity) was isolated and characterized; the starch granule size was approximately 13 µm with an amylose content of 33% and crystallinity level of 41%. The average gelatinization temperature (80.3 °C), enthalpy of gelatinization (18.4 J/g) and pasting temperature (83 °C) were higher than maize starch (Saeaurng, & Kuakpetoon, 2018), even though the digestibility of starch from mango kernel was not reported. The presence of phenolic compounds in the raw materials produced a decrease in the hydrolysis rate of starch due to diverse mechanisms as interactions phenolics-starch that is not recognized by the digestive enzymes (Bordenave, Hamaker, & Ferruzzi, 2014; Ribeiro, Barbosa, Queiroz, Knödler, & Schieber, 2008), that is important in the development of starchy foods with low glycemic response. The use of the unripe mango to produce a flour with high dietary fiber content has been suggested to decrease the postharvest loss. In a study by Vergara-Valencia et al. (2007), a flour of unripe mango was prepared and used as an ingredient in crackers- the 3
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unripe mango flour showed a balance in the insoluble and soluble dietary fibre with antioxidant capacity-; the crackers presented a 54.9 % of hydrolysis index (HI) and 55.59 % of predicted glycemic index (pGI) with acceptability by consumers. To the best of our knowledge, the use of the kernel (rich in starch) from the unripe mango has not been reported. In the unripe stage of development of the fruit, the kernel presents the intact energy reserves before beginning with the physiological maturation, which suggests that the starch has physicochemical and functional characteristics different from the kernel starch in the mature state (Zafar, & Sidhu, 2017). In this sense, the starch is the main storage nutrient to embryo development (kernel); also, contributes to the control of seed germination and dormancy (Dubreucq et al., 2010). The aim of this study was the isolation of starch from unripe mango kernel and its characterization.
Materials and methods Reagents The reagents were acquired at Sigma Aldrich (Sigma Chemicals Co., St Louis, MO, USA), Fermont (Productos Químicos Monterrey, Monterrey, Mexico) and JT Baker (Avantor Performance Materials, Center Valley, PA, USA).
Raw materials In May 2018, whole mangos were collected in the state of Morelos, Mexico. The mango fruits in the green stage (unripe mango) were manually cleaned and peeled. After peeling, the pulp and seeds were separated to obtain the mango kernel. The kernel was cut in 0.5 cm
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slices and dried in a convection oven at 40°C for 48 h. The material was later milled to obtain flours.
Flour characterization The chemical composition of mango kernel flour was determined according to AACC methods as follows: moisture (AACC methods 44-15.02), protein (AACC methods 4613.01), fat (AACC methods 30-25.01), ash (AACC methods 08-01.01), and crude fibre content (AACC methods 32-10.01).
Starch isolation The mango kernel flours were suspended in 1 % of sodium bisulphite solution (ratio 1:8) and subjected to magnetic stirring for 4 h at room temperature. The mixture was liquefied in a commercial blender and then filtered through meshes of 100, 200, and 325 US, after which the residue was washed with distilled water. The filtrate was centrifuged at 10800 g to precipitate the starch. The starch was dried in a convection oven at 40°C for 24 h. The purity of the starch was determined as the total starch content.
Total starch The starch purity and starch content in flour were measured as the total starch content. The total starch content was determined with a kit from Megazyme International Ireland Ltd., and analyzed according to the described procedure in the supplier’s manual.
Amylose content
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The amylose content was determined using the amylose/amylopectin assay kit (Megazyme International Ireland Limited, Bray, Ireland) by the precipitation of amylopectin chains with Concavanalin A (Con A).
Granule size distribution The size of the starch granules was determined by laser diffraction analysis using a Mastersizer 2000 (Malvern Instruments Ltd., Malvern, Worcestershire, UK). The samples were analyzed using the Hydro 2000S accessory. The powders were diluted in water to obtain a final concentration of 0.001% (to achieve saturation between 14 and 16%). The samples were sonicated during analysis to avoid aggregation of the granules.
Thermal properties Gelatinization parameters were evaluated with differential scanning calorimeter (DSC). In brief, a 2.2 mg of sample (dry basis) was placed directly into the DSC aluminium pan and 7 µL of deionized water was added. The temperature was ramped from 30°C to 120°C with a heating rate of 10°C/min. An empty DSC aluminium pan was used as a reference. For the retrogradation study, the gelatinized samples were stored at 4°C for 7- 14 days, after which they were analyzed under the same conditions as the gelatinization study in a differential scanning calorimeter (DSC) (TA Instruments, Q20, New Castle, NJ, USA). For both assays, the onset (T0), peak (TP), and conclusion temperatures (TC) as well as the enthalpy (ΔH) were calculated from the TA analysis software.
Pasting properties
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The pasting properties of mango kernel starch were assessed in a stress rheometer (Ar1500ex, TA Instruments, SA) using a starch pasting cell (SPC) with a rod rotor at 500 s-1. The temperature profile, initiated with a heating ramp of 5°C/min from 50°C to 95°C, was held at 95°C for 10 min, cooled at 5°C/min from 95 to 60°C, and was finally held at 60°C for 10 min. The sample concentration was recorded as 8 % (db).
In vitro starch digestion The in vitro digestibility of raw and cooked starch was performed according to the report described by Bello-Perez, Agama-Acevedo, Garcia-Valle, & Alvarez-Ramirez in 2019. In brief, starch was cooked for 20 min at 100°C and was later cooled until 37°C. An artificial saliva containing porcine α-amylase (250 U per mL of carbonate buffer, pH 7) was added for 15-20 s before 5 mL of pepsin (1 mg per mL in 0.02M HCl, pH 2). After, the digesting process (stomach) was performed with a mixture of pancreatin (2 mg/mL) and amyloglucosidase (28 U/mL) in distilled water to 37°C. Samples were withdrawn at the time interval of 5, 10, 15, 20, 30, 40, 50, 60, 90, 120, 240 and 360 min before the addition of 300 μL of stop hydrolysis solution (0.3M Na2CO3) to prevent further amylase activity. The glucose concentration in the supernatant was determined using a D-Glucose Assay Kit (GOPOD Format from Megazyme, International, Bray, Ireland) according to supplier instruction. Results were presented as g digested starch/100 g dry starch.
Statistical analysis All results are presented as the mean ± SE (standard error) of three or more replicates. Differences among means from each determination were evaluated by one-way analysis of
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variance (ANOVA) with a significance level of α = 0.05 using the Minitab 15 statistics package (Minitab Inc., State College, PA, USA).
Results and discussion Chemical composition of mango kernel flour Flour was produced from the unripe mango kernel with the objective of starch isolation. Mango kernel has high lipid content and dietary fibre-components (Table 1) that are important if a mango kernel flour is used in diverse food and feed products. Moreover, lipid and dietary fibre should be considered during starch isolation as both hinder the process due to the physical barrier of the non-starch polysaccharides of the dietary fibre or the amyloselipid complexes that can be produced. The mango kernel flour presents around 49 g/100 g of starch (Table 1), which is potentially extractable. Other components of the unripe mango kernel as protein, which are mainly enzymes, and ash (minerals) were also present (Table 1).
Starch characterization The total starch content indicates the purity of the sample after the isolation. The total starch content was 74 g/100 g due to the presence of other components in the mango kernel flour (Table 1) such as lipids, proteins and non-starch polysaccharides- that were not completely removed. Interactions between starch with lipids, polyphenols and proteins has been reported (Bordenave, 2012; Li, Ndiaye, Corbin, Foegeding & Ferruzzi, 2020). The light polarized microscopy showed intact starch granules with a well-defined Maltase cross (Fig. 1) that were not damaged during the isolation. The starch granules were oval and round with a mean size of 50 m. The scanning electron microscopy showed granules with 8
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some debris of macromolecules in the surface of the starch granules that can affect the physicochemical, functional and digestibility characteristics. The distribution of the unimodal size of granule was identified as an important issue during the gelatinization of mango kernel starch. The amylose content in the mango kernel starch was 23 g/100 g, which is the range of the normal starches. In this sense, mango kernel starch can substitute normal corn starch in some applications.
Gelatinization and retrogradation properties The gelatinization properties of the kernel starch are shown in Table 2. The gelatinization temperatures and the range of gelatinization temperature are related to the arrangement of starch components in the granule as well as the granule size distribution. Gelatinization temperature of unripe mango kernel starch can be compared to commercial starches such as maize (76.3 °C), potato (69.2 °C) and rice (82.6 °C) (Gelencsér, Juhász, Hódsági, Gergely, & Salgó, 2008; Liu & Xu, 2019), which are similar to this non-conventional starch. Enthalpy value is associated with the arrangement of the double helices of amylopectin that are present in the crystalline areas of the starch granule. The enthalpy value of mango kernel starch is lower than those determined in the native starches (10.44 J/g) (Lopez-Silva, Bello-Pérez, Agama-Acevedo, & Alvarez-Ramirez, 2019) of diverse botanical sources; the low enthalpy value indicates that during the purification of starch a disorganization of some double helices can be producing. The storage of gelatinized starches produces a reorganization of the starch components, mainly amylose- in the first days of storage, and amylopectin- at longer storage times. The retrogradation temperatures (Table 2) were lower than its gelatinization temperatures and the enthalpy value increased during longer storage times, indicating higher reorganization 9
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of starch components. In the retrogradation of starch, small or imperfect crystals are produced, that are observed with the range of temperature in the transition phase. Retrogradation is a phenomenon that affects the texture and digestibility of starchy products.
X-ray diffraction pattern The X-ray diffraction of the mango kernel starch is displayed in Fig. 2. The X-ray diffraction pattern is a typical A-type pattern, with four characteristic peaks at 2 15°, 17°, 18° and 23°, which is similar to that reported in the mango kernel starch isolated from ripe fruits (Guo, Lin, Fan, Zhang, & Wei, 2018; Saeaurng, et al., 2018). Additionally, the X-ray diffraction pattern showed a peak at 2 19° that indicate the presence of amylose-lipid complex, suggesting the presence of stearic and palmitic acids in the mango kernel (Kittiphoom, 2012). The amylose-lipid complexes are resistant to enzymatic hydrolysis and are reported as resistant starch type 5 (RS5) (Hasjim, Lavau, Gidley, & Gilbert, 2010), which is important in the use of mango kernel starch in foods and drugs.
Pasting profile Mango kernel starch showed a typical pasting profile (Fig. 3), with a peak viscosity similar to normal corn starch that is related to the granule size and the organization level of the starch components. However, the breaking and final viscosity value of the mango kernel starch was lower than that reported in normal maize starch (Chavez-Murillo et al., 2008). Both variables can be important during cooking of the starch dispersion to produce a gel.
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In vitro digestion properties The raw starch showed a slow increase in the hydrolysis extent with the time, inverse to the cooked sample where in the first 50 min of reaction around 45% of hydrolysis was obtained (Fig. 4). The hydrolysis rate of the cooked sample reached a plateau after 175 min of hydrolysis (around 67%), which is considered to be low compared with normal (BelloPerez et al., 2019). High-amylose corn starches did not show a plateau and the hydrolysis rate reached around 90% at 350 min (Bello-Perez et al., 2019). The hydrolysis pattern showed by mango kernel starch is different to that of conventional starches; the remnants of lipids, polyphenols and non-starch polysaccharides can affect the hydrolysis rate due to amylose-lipid complexes (Hasjim et al., 2010), interactions between starch-polyphenols (Camelo-Mendez, Flores-Silva, Agama-Acevedo, Tovar, & Bello-Pérez, 2018), inhibition of the amylases by polyphenols (Camelo-Mendez et al., 2018), and the presence of nonstarch polysaccharides restrict the hydrolysis of starch by the digestive enzymes (PatiñoRodríguez, Bello-Pérez, Flores-Silva, Sánchez-Rivera, & Romero-Bastida, 2018). The constant rate between the two samples was different (Table 3) with low rapidly digestible starch (RDS) content and high RS content in the raw sample, which increase and decrease, respectively, in the cooked starch. Interestingly, the slowly digestible starch (SDS) in the cooked starch had the highest value of the three fractions, an important issue due to the beneficial effect associated with the consumption of foods with a high content of SDS (Magallanes-Cruz, Flores-Silva, & Bello-Perez, 2017). The results of the hydrolysis extent in the cooked starch can suggest its use in foods where cooking is mandatory.
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Conclusions The kernel of the unripe mango is an alternative source of starch with gelatinization characteristics similar to maize starch, and low tendency to retrogradation. The in vitro enzymatic hydrolysis that mimic the gastrointestinal starch digestion showed slow digestion rate in the cooked sample, which indicate a sustained liberation of glucose. Unripe mango kernel is a by-product that can be used to produce starch with physicochemical and functional characteristics similar to commercial starches.
Conflicts of interest The authors declare no conflicts of interest.
Acknowledgment The experimental support of CNMN-IPN in the execution of the presented work is also acknowledged. The study was carried out under financial support by CONACyT (Cátedra No. 04-2016, Atención a Problemas Nacionales No. 2016-2140), SIP-IPN, COFAA-IPN and EDI-IPN.
References AACC International approved methods of analysis (2010). 11th edition. St Paul, MN, USA: AACC International. Ashoush, I. S. & Gadallah, M. G. E. (2011). Utilization of mango peels and seed kernels powders as sources of phytochemicals in biscuit. World Journal of Dairy and Food Science, 6, 35–42.
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Bello-Perez, L. A., Agama-Acevedo, E., Garcia-Valle, D. E., & Alvarez-Ramirez, J. (2019). A multiscale kinetics model for the analysis of starch amylolysis. International Journal of Biological Macromolecules, 122, 405-409. Bordenave, N., Hamaker, B. R., & Ferruzzi, M.G. (2014). Nature and consequences of noncovalent interactions between flavonoids and macronutrients in foods. Food & Function, 5, 18-34. Bordenave, N. (2012). In vitro assessment of food functionality. Food Science and Technology, 26, 16-18. Camelo-Méndez, G.A., Flores-Silva, P.C., Agama-Acevedo, E., Tovar, J., & Bello-Pérez, L.A. (2018). Incorporation of whole blue maize flour increases antioxidant capacity and
reduces
in
vitro
starch
digestibility
of
gluten-free
pasta.
Starch, 70,1700126. Chávez-Murillo, C. E., Wang, Y. J., Bello-Pérez, L. A. (2008). Morphological, physicochemical and structural characteristics of oxidized barley and corn starches. Starch/Staerke, 60, 634-645. Dubreucq B., Baud S., Debeaujon I., Dubos C., Marion-Poll A., Miquel M., North H., Rochat C., Routaboul J. M., & Lepiniec L. (2010). Seed Development. Plant Developmental Biology-Biotechnological Perspectives: Volume 1. Chapter 17. E.C. Pua and M.R. Davey (eds). Espinosa-Solis, V., Jane J. L., & Bello-Perez, L. A. (2009). Physicochemical characteristics of starches from unripe fruits of mango and banana. Starch, 61, 291–299. Evans, E. A., Ballen F.H., & Siddiq M. (2017). Mango Production, Global Trade, Consumption Trends, and Postharvest Processing and Nutrition. Handbook of Mango Fruit: Production, Postharvest Science, Processing Technology and 13
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Nutrition, First Edition (Chapter 1, pp. 10-12). Edited by Muhammad Siddiq, Jeffrey K. Brecht and Jiwan S. Sidhu. John Wiley & Sons Ltd. Gelencsér, T., Juhász, R., Hódsági, M., Gergely, S., & Salgó A. (2008). Comparative study of native and resistant starches. Acta Alimentaria, 37. Guo, K., Lin, L., Fan, X., Zhang, L., & Wei C. (2018). Comparison of structural and functional properties of starches from five fruit kernels. Food chemistry, 257, 75-82. Hasjim, J., Lavau, G.C., Gidley, M.J., & Gilbert, R.G. (2010). In vivo and in vitro starch digestion: are current in vitro techniques adequate? Biomacromolecules, 11, 36003608. Li, M., Ndiaye, C., Corbin, S., Foegeding, E.A., & Ferruzzi, M.G. (2020). Starch-phenolic complexes are built on physical CH-π interactions and can persist after hydrothermal treatments altering hydrodynamic radius and digestibility of model starch-based foods. Food Chemistry, 308, 125577. Kittiphoom, S. (2012). Utilization of Mango seed. International Food Research Journal, 19, 1325-1335. López-Silva, M., Bello-Pérez, L. A., Agama-Acevedo, E., & Alvarez-Ramirez, J. (2019). Effect of amylose content in morphological, functional and emulsification properties of OSA modified corn starch. Food Hydrocolloids. 97, 105212. Liu J., & Xu B. (2019). A comparative study on texture, gelatinisation, retrogradation and potentialfood application of binary gels made from selected starches and edible gums. Food Chemistry, 296, 100-108. Magallanes-Cruz, P.A., Flores-Silva, P.C., & Bello-Perez, L.A. (2017). Starch Structure Influences Its Digestibility: A Review. Journal of Food Science, 82, 2016-2023.
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Patiño-Rodríguez, O., Bello-Pérez, L. A., Flores-Silva, P. C., Sánchez-Rivera, M. M., & Romero-Bastida, C. A. (2018). Physicochemical properties and metabolomic profile of gluten-free spaghetti prepared with unripe plantain flours. LWT-Food Science and Technology, 90, 297-302. Ribeiro, S.M.R., Barbosa, L.C.A., Queiroz, J.H., Knödler, M., & Schieber, A. (2008). Phenolic compounds and antioxidant capacity of Brazilian mango (Mangifera indica L.) varieties. Food Chemistry, 110, 620–626. Saeaurng, K., & Kuakpetoon, D. (2018). A comparative study of mango seed kernel starches and other commercial starches: the contribution of chemical fine structure to granule crystallinity, gelatinization, retrogradation, and pasting properties. Journal of Food Measurement and Characterization, 12, 2444–2452. Vergara-Valencia, N., Granados-Pereza, E., Agama-Acevedo, E., Tovar, J., Ruales, J., & Bello-Pérez, L. A. (2007). Fibre concentrate from mango fruit: Characterization, associated antioxidant capacity and application as a bakery product ingredient. LWT-Food Science and Technology, 40, 722-729. Zafar TA, & Sidhu JS. Composition and nutritional properties of mangoes. In: Siddiq M, Brecht JK, Sidhu JS, editors. Handbook of mango fruit: production, postharvest science, processing technology and nutrition. 1st ed. New York: Wiley-Blackwell Publishing Co; 2017. 217–236.
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Tables Table 1. Chemical composition of flour produced from unripe mango kernel (g/100 g, dry basis)* Flour
Moisture
Protein#,&
Fat#
Ash#
Dietary Fibre#
Total Starch
Kernel
3.16 ± 0.29
4.29 ± 0.12
11.33 ± 0.06
2.09 ± 0.01
12.03
48.79 ± 1.66
*Mean ± standard error, n=4, DWB. #, dry basis.
Table 2. Gelatinization and retrogradation properties of isolated starch from unripe mango kernel by differential scanning calorimetry.
Mango starch
T0 (°C)
TP (°C)
TC (°C)
TC – T0 (°C)
ΔH (J/g)
RD (%)
Gelatinization
69.89 ± 0.59a
75.89 ± 0.38a
86.30 ± 2.18a
16.40 ± 1.92b
9.04 ± 0.48a
-
0.17b
0.41b
0.00c
0.17c
0.09c
10.92 ± 0.61b
3.33 ± 0.23b
35.93 ± 1.01a
Retrogradation (7 d)
53.85 ±
Retrogradation (14 d)
47.13 ± 0.00c
61.31 ±
59.25 ± 1.58c
68.70 ±
70.65 ± 0.00b
9.89 ±
23.51 ± 0.00a
1.01 ±
T0, onset temperature; TP, peak temperature; TC, conclusion temperature; TC – T0, temperature range; ΔH, enthalpy; RD, retrogradation degree, (retrogradation ΔH/gelatinization ΔH) * 100. Mean of three measurements ± standard deviation, in a column with the same letter are not significantly different (p ≤ 0.05).
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Table 3. Kinetics constant and digestibility fractions of raw and cooked mango starches.
1
Sample
×103 (min-1)
RDS (%)
SDS (%)
RS (%)
Raw
7.09 ± 0.45b
6.35 ± 1.71b
19.92 ± 1.23b
73.73 ± 1.92a
Cooked
21.73 ± 0.49a
29.07 ± 1.53a
42.18 ± 3.17a
28.75 ± 1.78b
Notation: kinetics constant. RDS: rapidly digestible starch; SDS: slowly digestible starch, RS:
resistant starch. 2
Values are means ± standard error, of three replicates. Superscripts with different lower-case letters
at different concentrations indicate significant differences (P ≤ 0.05).
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Figures
Figure 1. Mango kernel starch, A; under white and, B; polarized light microscopy (40 X), C; scanning electron micrographs (scale in micrograph) and D; particle size distribution.
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Figure 2. X-ray diffractograms of starch isolated from mango kernel.
Figure 3. Starch pasting profile of mango kernel.
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80 70
Hydrolysis (%)
60 Raw Cooked
50 40 30 20 10 0 0
50
100
150
200
250
300
350
Time (min) Figure 4. Hydrolysis kinetics of raw and cooked mango starches. The continuous line denotes the least-squares fitting by the first-order exponential model.
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Not applicable
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Highlights 1. The amylose content in the mango kernel starch was in the range of the normal starches. 2. The mango kernel starch showed low trend to retrogradation at 14 days of storage. 3. The X-ray diffraction pattern indicated the presence of amylose-lipid complex. 4. The in vitro starch hydrolysis of the cooked sample reached at 67%.
Omar Patiño-Rodríguez, Edith Agama-Acevedo, Gonzalo Ramos-Lopez, Luis A. Bello-Pérez PII:
S0268-005X(19)31933-2
DOI:
https://doi.org/10.1016/j.foodhyd.2019.105512
Reference:
FOOHYD 105512
To appear in:
Food Hydrocolloids
Received Date:
22 August 2019
Accepted Date:
12 November 2019
Please cite this article as: Omar Patiño-Rodríguez, Edith Agama-Acevedo, Gonzalo Ramos-Lopez, Luis A. Bello-Pérez, Unripe mango kernel starch: partial characterization, Food Hydrocolloids (2019), https://doi.org/10.1016/j.foodhyd.2019.105512
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
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Unripe mango kernel starch: partial characterization
Omar Patiño-Rodríguez1,*, Edith Agama-Acevedo2, Gonzalo Ramos-Lopez3, and Luis A. Bello-Pérez2
1
CONACyT-Instituto Politécnico Nacional, CEPROBI, Km. 6.5 Carr. Yautepec-Jojutla
Col. San Isidro, Calle CEPROBI No. 8, Yautepec, Morelos, México. 2
Instituto Politécnico Nacional, CEPROBI, Km. 6.5 Carr. Yautepec-Jojutla Col. San
Isidro, Calle CEPROBI No. 8, Yautepec, Morelos, México. 3
Instituto Politécnico Nacional, CICATA Unidad Queretaro, Cerro Blanco 141, Queretaro,
México.
*Corresponding author: CONACyT-Instituto Politécnico Nacional, Centro de Desarrollo de Productos Bióticos (CEPROBI). Carretera Yautepec-Jojutla, Km. 6, calle CEPROBI No. 8. Yautepec, Morelos, México. C.P. 62731, Apartado Postal 24. Telephones: (735) 394 20 20, 394 18 96, Ext. 28 25 88. E-mail: [email protected]
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Abstract Although a rich source of polyphenols, starch and dietary fibre, unripe mango has been identified as a functional ingredient. The kernel of unripe mango is rich in starch and certain compounds such as non-starch polysaccharides (components of dietary fibre), polyphenols and lipids. The isolation of starch from unripe mango kernel can be an alternative to obtain non-conventional ingredients to diverse end-uses. The aim of this study was the isolation of starch from unripe mango kernel and its partial characterization. The isolated starch was studied in morphology with microscopic methods, X-ray diffraction, thermal properties, pasting profile, and in vitro digestibility. The starch granules were distinguished as oval and round- with a mean size of 50 m and some debris of lipids in the surface. The amylose content of the starch granule was 23 g/100 g and A-type diffraction pattern was observed. The temperature and enthalpy of gelatinization are similar to conventional starch as maize with a low tendency to retrogradation. The pasting profile of mango kernel starch was identified as typical of native starch with gel formation upon cooling. The in vitro enzymatic hydrolysis of mango kernel starch was different from that of conventional starches with slow digestion rate in the cooked sample. The starch from unripe mango kernel can be an alternative to starchy raw materials like as cereals or pulses in food and non-food applications.
Keywords: unripe mango; kernel; starch; characterization; in vitro digestibility.
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Introduction Mango is a climacteric fruit that is harvested at a physiologically mature green stage and allowed to ripen for industrial use (mango concentrate) and market (Evans, Ballen, & Siddiq, 2017). The pulp of unripe mango was used for starch separation, with a granule size between 5-10 µm, apparent amylose content of 31.1 %, the molecular weight of amylopectin 5.013 Mw x 108 g/mol, and gyration radius of 298 nm (Espinosa-Solis, Jane, & Bello-Perez, 2009). The industrial processing of ripe mango (12-15 °Brix) produces a concentrate and by-product, kernel and peel, respectively. With the objective to decrease pollution generated by the final deposition of the mango by-products, the use of mango kernel was proposed (Saeaurng, & Kuakpetoon, 2018). The main components of a mango kernel are starch and bioactive compounds such as phenolics, vitamins, minerals, as well as oil (Ashoush, & Gadallah, 2011). Starch of the mango kernel (in physiological maturity) was isolated and characterized; the starch granule size was approximately 13 µm with an amylose content of 33% and crystallinity level of 41%. The average gelatinization temperature (80.3 °C), enthalpy of gelatinization (18.4 J/g) and pasting temperature (83 °C) were higher than maize starch (Saeaurng, & Kuakpetoon, 2018), even though the digestibility of starch from mango kernel was not reported. The presence of phenolic compounds in the raw materials produced a decrease in the hydrolysis rate of starch due to diverse mechanisms as interactions phenolics-starch that is not recognized by the digestive enzymes (Bordenave, Hamaker, & Ferruzzi, 2014; Ribeiro, Barbosa, Queiroz, Knödler, & Schieber, 2008), that is important in the development of starchy foods with low glycemic response. The use of the unripe mango to produce a flour with high dietary fiber content has been suggested to decrease the postharvest loss. In a study by Vergara-Valencia et al. (2007), a flour of unripe mango was prepared and used as an ingredient in crackers- the 3
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unripe mango flour showed a balance in the insoluble and soluble dietary fibre with antioxidant capacity-; the crackers presented a 54.9 % of hydrolysis index (HI) and 55.59 % of predicted glycemic index (pGI) with acceptability by consumers. To the best of our knowledge, the use of the kernel (rich in starch) from the unripe mango has not been reported. In the unripe stage of development of the fruit, the kernel presents the intact energy reserves before beginning with the physiological maturation, which suggests that the starch has physicochemical and functional characteristics different from the kernel starch in the mature state (Zafar, & Sidhu, 2017). In this sense, the starch is the main storage nutrient to embryo development (kernel); also, contributes to the control of seed germination and dormancy (Dubreucq et al., 2010). The aim of this study was the isolation of starch from unripe mango kernel and its characterization.
Materials and methods Reagents The reagents were acquired at Sigma Aldrich (Sigma Chemicals Co., St Louis, MO, USA), Fermont (Productos Químicos Monterrey, Monterrey, Mexico) and JT Baker (Avantor Performance Materials, Center Valley, PA, USA).
Raw materials In May 2018, whole mangos were collected in the state of Morelos, Mexico. The mango fruits in the green stage (unripe mango) were manually cleaned and peeled. After peeling, the pulp and seeds were separated to obtain the mango kernel. The kernel was cut in 0.5 cm
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slices and dried in a convection oven at 40°C for 48 h. The material was later milled to obtain flours.
Flour characterization The chemical composition of mango kernel flour was determined according to AACC methods as follows: moisture (AACC methods 44-15.02), protein (AACC methods 4613.01), fat (AACC methods 30-25.01), ash (AACC methods 08-01.01), and crude fibre content (AACC methods 32-10.01).
Starch isolation The mango kernel flours were suspended in 1 % of sodium bisulphite solution (ratio 1:8) and subjected to magnetic stirring for 4 h at room temperature. The mixture was liquefied in a commercial blender and then filtered through meshes of 100, 200, and 325 US, after which the residue was washed with distilled water. The filtrate was centrifuged at 10800 g to precipitate the starch. The starch was dried in a convection oven at 40°C for 24 h. The purity of the starch was determined as the total starch content.
Total starch The starch purity and starch content in flour were measured as the total starch content. The total starch content was determined with a kit from Megazyme International Ireland Ltd., and analyzed according to the described procedure in the supplier’s manual.
Amylose content
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The amylose content was determined using the amylose/amylopectin assay kit (Megazyme International Ireland Limited, Bray, Ireland) by the precipitation of amylopectin chains with Concavanalin A (Con A).
Granule size distribution The size of the starch granules was determined by laser diffraction analysis using a Mastersizer 2000 (Malvern Instruments Ltd., Malvern, Worcestershire, UK). The samples were analyzed using the Hydro 2000S accessory. The powders were diluted in water to obtain a final concentration of 0.001% (to achieve saturation between 14 and 16%). The samples were sonicated during analysis to avoid aggregation of the granules.
Thermal properties Gelatinization parameters were evaluated with differential scanning calorimeter (DSC). In brief, a 2.2 mg of sample (dry basis) was placed directly into the DSC aluminium pan and 7 µL of deionized water was added. The temperature was ramped from 30°C to 120°C with a heating rate of 10°C/min. An empty DSC aluminium pan was used as a reference. For the retrogradation study, the gelatinized samples were stored at 4°C for 7- 14 days, after which they were analyzed under the same conditions as the gelatinization study in a differential scanning calorimeter (DSC) (TA Instruments, Q20, New Castle, NJ, USA). For both assays, the onset (T0), peak (TP), and conclusion temperatures (TC) as well as the enthalpy (ΔH) were calculated from the TA analysis software.
Pasting properties
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The pasting properties of mango kernel starch were assessed in a stress rheometer (Ar1500ex, TA Instruments, SA) using a starch pasting cell (SPC) with a rod rotor at 500 s-1. The temperature profile, initiated with a heating ramp of 5°C/min from 50°C to 95°C, was held at 95°C for 10 min, cooled at 5°C/min from 95 to 60°C, and was finally held at 60°C for 10 min. The sample concentration was recorded as 8 % (db).
In vitro starch digestion The in vitro digestibility of raw and cooked starch was performed according to the report described by Bello-Perez, Agama-Acevedo, Garcia-Valle, & Alvarez-Ramirez in 2019. In brief, starch was cooked for 20 min at 100°C and was later cooled until 37°C. An artificial saliva containing porcine α-amylase (250 U per mL of carbonate buffer, pH 7) was added for 15-20 s before 5 mL of pepsin (1 mg per mL in 0.02M HCl, pH 2). After, the digesting process (stomach) was performed with a mixture of pancreatin (2 mg/mL) and amyloglucosidase (28 U/mL) in distilled water to 37°C. Samples were withdrawn at the time interval of 5, 10, 15, 20, 30, 40, 50, 60, 90, 120, 240 and 360 min before the addition of 300 μL of stop hydrolysis solution (0.3M Na2CO3) to prevent further amylase activity. The glucose concentration in the supernatant was determined using a D-Glucose Assay Kit (GOPOD Format from Megazyme, International, Bray, Ireland) according to supplier instruction. Results were presented as g digested starch/100 g dry starch.
Statistical analysis All results are presented as the mean ± SE (standard error) of three or more replicates. Differences among means from each determination were evaluated by one-way analysis of
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variance (ANOVA) with a significance level of α = 0.05 using the Minitab 15 statistics package (Minitab Inc., State College, PA, USA).
Results and discussion Chemical composition of mango kernel flour Flour was produced from the unripe mango kernel with the objective of starch isolation. Mango kernel has high lipid content and dietary fibre-components (Table 1) that are important if a mango kernel flour is used in diverse food and feed products. Moreover, lipid and dietary fibre should be considered during starch isolation as both hinder the process due to the physical barrier of the non-starch polysaccharides of the dietary fibre or the amyloselipid complexes that can be produced. The mango kernel flour presents around 49 g/100 g of starch (Table 1), which is potentially extractable. Other components of the unripe mango kernel as protein, which are mainly enzymes, and ash (minerals) were also present (Table 1).
Starch characterization The total starch content indicates the purity of the sample after the isolation. The total starch content was 74 g/100 g due to the presence of other components in the mango kernel flour (Table 1) such as lipids, proteins and non-starch polysaccharides- that were not completely removed. Interactions between starch with lipids, polyphenols and proteins has been reported (Bordenave, 2012; Li, Ndiaye, Corbin, Foegeding & Ferruzzi, 2020). The light polarized microscopy showed intact starch granules with a well-defined Maltase cross (Fig. 1) that were not damaged during the isolation. The starch granules were oval and round with a mean size of 50 m. The scanning electron microscopy showed granules with 8
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some debris of macromolecules in the surface of the starch granules that can affect the physicochemical, functional and digestibility characteristics. The distribution of the unimodal size of granule was identified as an important issue during the gelatinization of mango kernel starch. The amylose content in the mango kernel starch was 23 g/100 g, which is the range of the normal starches. In this sense, mango kernel starch can substitute normal corn starch in some applications.
Gelatinization and retrogradation properties The gelatinization properties of the kernel starch are shown in Table 2. The gelatinization temperatures and the range of gelatinization temperature are related to the arrangement of starch components in the granule as well as the granule size distribution. Gelatinization temperature of unripe mango kernel starch can be compared to commercial starches such as maize (76.3 °C), potato (69.2 °C) and rice (82.6 °C) (Gelencsér, Juhász, Hódsági, Gergely, & Salgó, 2008; Liu & Xu, 2019), which are similar to this non-conventional starch. Enthalpy value is associated with the arrangement of the double helices of amylopectin that are present in the crystalline areas of the starch granule. The enthalpy value of mango kernel starch is lower than those determined in the native starches (10.44 J/g) (Lopez-Silva, Bello-Pérez, Agama-Acevedo, & Alvarez-Ramirez, 2019) of diverse botanical sources; the low enthalpy value indicates that during the purification of starch a disorganization of some double helices can be producing. The storage of gelatinized starches produces a reorganization of the starch components, mainly amylose- in the first days of storage, and amylopectin- at longer storage times. The retrogradation temperatures (Table 2) were lower than its gelatinization temperatures and the enthalpy value increased during longer storage times, indicating higher reorganization 9
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of starch components. In the retrogradation of starch, small or imperfect crystals are produced, that are observed with the range of temperature in the transition phase. Retrogradation is a phenomenon that affects the texture and digestibility of starchy products.
X-ray diffraction pattern The X-ray diffraction of the mango kernel starch is displayed in Fig. 2. The X-ray diffraction pattern is a typical A-type pattern, with four characteristic peaks at 2 15°, 17°, 18° and 23°, which is similar to that reported in the mango kernel starch isolated from ripe fruits (Guo, Lin, Fan, Zhang, & Wei, 2018; Saeaurng, et al., 2018). Additionally, the X-ray diffraction pattern showed a peak at 2 19° that indicate the presence of amylose-lipid complex, suggesting the presence of stearic and palmitic acids in the mango kernel (Kittiphoom, 2012). The amylose-lipid complexes are resistant to enzymatic hydrolysis and are reported as resistant starch type 5 (RS5) (Hasjim, Lavau, Gidley, & Gilbert, 2010), which is important in the use of mango kernel starch in foods and drugs.
Pasting profile Mango kernel starch showed a typical pasting profile (Fig. 3), with a peak viscosity similar to normal corn starch that is related to the granule size and the organization level of the starch components. However, the breaking and final viscosity value of the mango kernel starch was lower than that reported in normal maize starch (Chavez-Murillo et al., 2008). Both variables can be important during cooking of the starch dispersion to produce a gel.
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In vitro digestion properties The raw starch showed a slow increase in the hydrolysis extent with the time, inverse to the cooked sample where in the first 50 min of reaction around 45% of hydrolysis was obtained (Fig. 4). The hydrolysis rate of the cooked sample reached a plateau after 175 min of hydrolysis (around 67%), which is considered to be low compared with normal (BelloPerez et al., 2019). High-amylose corn starches did not show a plateau and the hydrolysis rate reached around 90% at 350 min (Bello-Perez et al., 2019). The hydrolysis pattern showed by mango kernel starch is different to that of conventional starches; the remnants of lipids, polyphenols and non-starch polysaccharides can affect the hydrolysis rate due to amylose-lipid complexes (Hasjim et al., 2010), interactions between starch-polyphenols (Camelo-Mendez, Flores-Silva, Agama-Acevedo, Tovar, & Bello-Pérez, 2018), inhibition of the amylases by polyphenols (Camelo-Mendez et al., 2018), and the presence of nonstarch polysaccharides restrict the hydrolysis of starch by the digestive enzymes (PatiñoRodríguez, Bello-Pérez, Flores-Silva, Sánchez-Rivera, & Romero-Bastida, 2018). The constant rate between the two samples was different (Table 3) with low rapidly digestible starch (RDS) content and high RS content in the raw sample, which increase and decrease, respectively, in the cooked starch. Interestingly, the slowly digestible starch (SDS) in the cooked starch had the highest value of the three fractions, an important issue due to the beneficial effect associated with the consumption of foods with a high content of SDS (Magallanes-Cruz, Flores-Silva, & Bello-Perez, 2017). The results of the hydrolysis extent in the cooked starch can suggest its use in foods where cooking is mandatory.
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Conclusions The kernel of the unripe mango is an alternative source of starch with gelatinization characteristics similar to maize starch, and low tendency to retrogradation. The in vitro enzymatic hydrolysis that mimic the gastrointestinal starch digestion showed slow digestion rate in the cooked sample, which indicate a sustained liberation of glucose. Unripe mango kernel is a by-product that can be used to produce starch with physicochemical and functional characteristics similar to commercial starches.
Conflicts of interest The authors declare no conflicts of interest.
Acknowledgment The experimental support of CNMN-IPN in the execution of the presented work is also acknowledged. The study was carried out under financial support by CONACyT (Cátedra No. 04-2016, Atención a Problemas Nacionales No. 2016-2140), SIP-IPN, COFAA-IPN and EDI-IPN.
References AACC International approved methods of analysis (2010). 11th edition. St Paul, MN, USA: AACC International. Ashoush, I. S. & Gadallah, M. G. E. (2011). Utilization of mango peels and seed kernels powders as sources of phytochemicals in biscuit. World Journal of Dairy and Food Science, 6, 35–42.
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Bello-Perez, L. A., Agama-Acevedo, E., Garcia-Valle, D. E., & Alvarez-Ramirez, J. (2019). A multiscale kinetics model for the analysis of starch amylolysis. International Journal of Biological Macromolecules, 122, 405-409. Bordenave, N., Hamaker, B. R., & Ferruzzi, M.G. (2014). Nature and consequences of noncovalent interactions between flavonoids and macronutrients in foods. Food & Function, 5, 18-34. Bordenave, N. (2012). In vitro assessment of food functionality. Food Science and Technology, 26, 16-18. Camelo-Méndez, G.A., Flores-Silva, P.C., Agama-Acevedo, E., Tovar, J., & Bello-Pérez, L.A. (2018). Incorporation of whole blue maize flour increases antioxidant capacity and
reduces
in
vitro
starch
digestibility
of
gluten-free
pasta.
Starch, 70,1700126. Chávez-Murillo, C. E., Wang, Y. J., Bello-Pérez, L. A. (2008). Morphological, physicochemical and structural characteristics of oxidized barley and corn starches. Starch/Staerke, 60, 634-645. Dubreucq B., Baud S., Debeaujon I., Dubos C., Marion-Poll A., Miquel M., North H., Rochat C., Routaboul J. M., & Lepiniec L. (2010). Seed Development. Plant Developmental Biology-Biotechnological Perspectives: Volume 1. Chapter 17. E.C. Pua and M.R. Davey (eds). Espinosa-Solis, V., Jane J. L., & Bello-Perez, L. A. (2009). Physicochemical characteristics of starches from unripe fruits of mango and banana. Starch, 61, 291–299. Evans, E. A., Ballen F.H., & Siddiq M. (2017). Mango Production, Global Trade, Consumption Trends, and Postharvest Processing and Nutrition. Handbook of Mango Fruit: Production, Postharvest Science, Processing Technology and 13
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Nutrition, First Edition (Chapter 1, pp. 10-12). Edited by Muhammad Siddiq, Jeffrey K. Brecht and Jiwan S. Sidhu. John Wiley & Sons Ltd. Gelencsér, T., Juhász, R., Hódsági, M., Gergely, S., & Salgó A. (2008). Comparative study of native and resistant starches. Acta Alimentaria, 37. Guo, K., Lin, L., Fan, X., Zhang, L., & Wei C. (2018). Comparison of structural and functional properties of starches from five fruit kernels. Food chemistry, 257, 75-82. Hasjim, J., Lavau, G.C., Gidley, M.J., & Gilbert, R.G. (2010). In vivo and in vitro starch digestion: are current in vitro techniques adequate? Biomacromolecules, 11, 36003608. Li, M., Ndiaye, C., Corbin, S., Foegeding, E.A., & Ferruzzi, M.G. (2020). Starch-phenolic complexes are built on physical CH-π interactions and can persist after hydrothermal treatments altering hydrodynamic radius and digestibility of model starch-based foods. Food Chemistry, 308, 125577. Kittiphoom, S. (2012). Utilization of Mango seed. International Food Research Journal, 19, 1325-1335. López-Silva, M., Bello-Pérez, L. A., Agama-Acevedo, E., & Alvarez-Ramirez, J. (2019). Effect of amylose content in morphological, functional and emulsification properties of OSA modified corn starch. Food Hydrocolloids. 97, 105212. Liu J., & Xu B. (2019). A comparative study on texture, gelatinisation, retrogradation and potentialfood application of binary gels made from selected starches and edible gums. Food Chemistry, 296, 100-108. Magallanes-Cruz, P.A., Flores-Silva, P.C., & Bello-Perez, L.A. (2017). Starch Structure Influences Its Digestibility: A Review. Journal of Food Science, 82, 2016-2023.
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Patiño-Rodríguez, O., Bello-Pérez, L. A., Flores-Silva, P. C., Sánchez-Rivera, M. M., & Romero-Bastida, C. A. (2018). Physicochemical properties and metabolomic profile of gluten-free spaghetti prepared with unripe plantain flours. LWT-Food Science and Technology, 90, 297-302. Ribeiro, S.M.R., Barbosa, L.C.A., Queiroz, J.H., Knödler, M., & Schieber, A. (2008). Phenolic compounds and antioxidant capacity of Brazilian mango (Mangifera indica L.) varieties. Food Chemistry, 110, 620–626. Saeaurng, K., & Kuakpetoon, D. (2018). A comparative study of mango seed kernel starches and other commercial starches: the contribution of chemical fine structure to granule crystallinity, gelatinization, retrogradation, and pasting properties. Journal of Food Measurement and Characterization, 12, 2444–2452. Vergara-Valencia, N., Granados-Pereza, E., Agama-Acevedo, E., Tovar, J., Ruales, J., & Bello-Pérez, L. A. (2007). Fibre concentrate from mango fruit: Characterization, associated antioxidant capacity and application as a bakery product ingredient. LWT-Food Science and Technology, 40, 722-729. Zafar TA, & Sidhu JS. Composition and nutritional properties of mangoes. In: Siddiq M, Brecht JK, Sidhu JS, editors. Handbook of mango fruit: production, postharvest science, processing technology and nutrition. 1st ed. New York: Wiley-Blackwell Publishing Co; 2017. 217–236.
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Tables Table 1. Chemical composition of flour produced from unripe mango kernel (g/100 g, dry basis)* Flour
Moisture
Protein#,&
Fat#
Ash#
Dietary Fibre#
Total Starch
Kernel
3.16 ± 0.29
4.29 ± 0.12
11.33 ± 0.06
2.09 ± 0.01
12.03
48.79 ± 1.66
*Mean ± standard error, n=4, DWB. #, dry basis.
Table 2. Gelatinization and retrogradation properties of isolated starch from unripe mango kernel by differential scanning calorimetry.
Mango starch
T0 (°C)
TP (°C)
TC (°C)
TC – T0 (°C)
ΔH (J/g)
RD (%)
Gelatinization
69.89 ± 0.59a
75.89 ± 0.38a
86.30 ± 2.18a
16.40 ± 1.92b
9.04 ± 0.48a
-
0.17b
0.41b
0.00c
0.17c
0.09c
10.92 ± 0.61b
3.33 ± 0.23b
35.93 ± 1.01a
Retrogradation (7 d)
53.85 ±
Retrogradation (14 d)
47.13 ± 0.00c
61.31 ±
59.25 ± 1.58c
68.70 ±
70.65 ± 0.00b
9.89 ±
23.51 ± 0.00a
1.01 ±
T0, onset temperature; TP, peak temperature; TC, conclusion temperature; TC – T0, temperature range; ΔH, enthalpy; RD, retrogradation degree, (retrogradation ΔH/gelatinization ΔH) * 100. Mean of three measurements ± standard deviation, in a column with the same letter are not significantly different (p ≤ 0.05).
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Table 3. Kinetics constant and digestibility fractions of raw and cooked mango starches.
1
Sample
×103 (min-1)
RDS (%)
SDS (%)
RS (%)
Raw
7.09 ± 0.45b
6.35 ± 1.71b
19.92 ± 1.23b
73.73 ± 1.92a
Cooked
21.73 ± 0.49a
29.07 ± 1.53a
42.18 ± 3.17a
28.75 ± 1.78b
Notation: kinetics constant. RDS: rapidly digestible starch; SDS: slowly digestible starch, RS:
resistant starch. 2
Values are means ± standard error, of three replicates. Superscripts with different lower-case letters
at different concentrations indicate significant differences (P ≤ 0.05).
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Figures
Figure 1. Mango kernel starch, A; under white and, B; polarized light microscopy (40 X), C; scanning electron micrographs (scale in micrograph) and D; particle size distribution.
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Figure 2. X-ray diffractograms of starch isolated from mango kernel.
Figure 3. Starch pasting profile of mango kernel.
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80 70
Hydrolysis (%)
60 Raw Cooked
50 40 30 20 10 0 0
50
100
150
200
250
300
350
Time (min) Figure 4. Hydrolysis kinetics of raw and cooked mango starches. The continuous line denotes the least-squares fitting by the first-order exponential model.
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
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Highlights 1. The amylose content in the mango kernel starch was in the range of the normal starches. 2. The mango kernel starch showed low trend to retrogradation at 14 days of storage. 3. The X-ray diffraction pattern indicated the presence of amylose-lipid complex. 4. The in vitro starch hydrolysis of the cooked sample reached at 67%.