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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2020 Apr 15;57(10):3801–3813. doi: 10.1007/s13197-020-04412-7

Diversity and relationship among grain, flour and starch characteristics of Indian Himalayan colored corn accessions

Shalini Trehan 1, Narpinder Singh 1, Amritpal Kaur 1,✉
PMCID: PMC7447731  PMID: 32903906

Abstract

The present study examined the diversification and relationship among grain, flour and starch characteristics of thirty eight differently coloured corn accessions. The differences among accessions were more pronounced due to heterogeneity in genetic traits than color. Colour properties were positively related with phenolics and antioxidant activity. K, Ca, Zn, Mg, Na, Cu, Fe and Mn were the prominent minerals present in accessions. Accumulation of 10 polypeptides, ranging from 10 to 95 kDa was also evaluated. HPLC analysis showed the presence of gallic acid, Catechin, caeffic acid, chlorogenic acid, protocatechuic acid, p-coumaric acid, vanillic acid, quercetin, sinapic acid, ferulic acid, reservatrol and luteolin in flours. Accessions had higher proportions of amino acids, citrulline, arginine, GABA, phenylalanine, isoleucine, tyrosine, threonine, glycine. Starch granules with different particle size showed angular structure. Final viscosity, set back viscosity and crystallinity positively related to amylose content of starch. Starches with A-type crystalline pattern showed variability in thermal properties. The results of this study showed significant relationship between DPPH and total phenolic content, thermal properties, amylose content and crystallinity among various corn germplasm. These will be helpful for selection of appropriate accessions having required characteristics not only for food applications but also for non-food ones.

Electronic supplementary material

The online version of this article (10.1007/s13197-020-04412-7) contains supplementary material, which is available to authorized users.

Keywords: Corn accessions, Amino acids, Protein profile, Polyphenols, Differential scanning calorimetry (DSC), Minerals

Introduction

Corn/Maize (Zea mays) is world’s highest growing cereal crop and consumed globally next to rice and wheat. It’s utility as a food and feed resources make it acceptable for consumption. The composition of corn includes starch (70–75%), protein (8–10%), lipid (4–5%), sugar (1–3%) and ash (1–4%) (Narpinder et al. 2014). Corn has physicochemical characteristics that include having large content of starch, low α-gliadin fraction in protein, lipids, flavonoids and microelements which make it vital source of human consumption (Wojtowicz et al. 2013). Phytochemical compounds may act as nutraceutical in the form of enzymes, antioxidants and its cofactors and therefore having health benefits in promoting effects such as anticarcinogenic and vasodilatory effects (H€ansch and Mendel 2009). Phytosterols present in it, help in reducing the cholesterol levels and can be utilized for manufacturing of various food items of domestic and industrial use such as flour, tortilla, snacks, porridge, gruel, beverages and corn flakes (Bello-Pérez et al. 2015). The pigmented corn (mainly blue) has received the most interest for the development due to the presence of phenolic compounds prominently anthocyanins (Del Pozo-Insfran et al. 2006). The three classes in which it can be categorized are: (1) high amylose corn containing higher amylose content between 40 and 70%; (2) waxy corn with 100% amylopectin; and (3) sugary corn containing higher level of sucrose with low starch content (Nelson and Pan 1995). On the basis of different proportions of horny (vitreous) and floury endosperm corn has classified into different types viz. dent, flint, floury, waxy, popcorn and sweet corn (Knott et al. 1995). Gluten free products are being developed for the population suffering from coeliac disease as they cannot tolerate some peptides found in wheat, rye and barley (de la Hera et al. 2013). The characteristic feature of corn amylose such as resistant starch content has many health benefits while other properties; degree of polymerization, film formation characteristics supports it in the formation of biodegradable films and electronic chips (Guan et al. 2011). Although corn is widely grown and researched in India, yet the analyses of grain, flour and starches of Himalayan corn genetic pool needs further exploration. In particular, the relationship between various corn germplasm will be helpful by selection of appropriate accession having required characteristics not only for food applications but also for non food ones. Therefore, this investigation was done to characterise the corn accessions grown in India Himalayan based on their physicochemical, thermal, pasting, polyphenolic, amino acid profile and morphological properties of grain, flour and starch.

Materials and methods

Materials

Germplasm of Thirty eight (38) corn accessions varying in color i.e. yellow (IC-347386, IC-427129, IC-397828, IC-397956, IC-397957, IC-397958, IC-361709, IC-362129, IC-362130, IC-361726, IC-447627, IC-447645, IC-447646, IC-447641, IC-447648) white (IC-447511, IC-447638, IC-447632, IC-447660, IC-447639, IC-447328, IC-550370, IC-550365, IC-447626, IC-447501, IC-447509, IC-361712, IC-361714, IC-447632, IC-361719) and purple (IC-361727, IC-447636, IC-447648, IC-447649, IC-447667, IC-447647, IC-447643, IC-447644) were procured from NBPGR, Regional Station, Pagli, Shimla (India) and were harvest of 2012–2013.

Grain color

Color characteristics (L*, a* and b*) of corn grains from various accessions were measured using a colorimeter (Hunter Labs, USA) as described by Trehan et al. (2018).

Flour characteristics

Physicochemical and pasting properties of flours

50 g of grains of different corn accessions were ground to pass through sieve no. 72 (BSS) in order to get uniform particle sized flour that was kept in airtight PET jars for future analyses. Flours were examined for proximate composition using the AOAC standard methods (1990). Pasting properties of the flour were ascertained by the method adopted by Trehan et al. (2018).

Total phenolic content and antioxidant activity of flours

Total phenolic content (TPC) and antioxidant activity was determined as described earlier (Trehan et al. 2018) with minor changes. The results obtained were described as μg GAE/g and μM trolox/mg, respectively.

Mineral composition

Mineral content of flours was examined with the help of an Atomic Absorption Spectrometer (Agilent Technologies) as described earlier (Ghumman et al. 2017).

Amino acid (AA) determination

The amino acids (AAs) were characterized using the method described in our previous report (Ghumman et al. 2017).

SDS-PAGE analysis

Total proteins present in corn flour (milled whole grain) were separated and SDS-PAGE analyses were performed as described earlier by Thakur et al. (2015).

HPLC analysis of flours

Extraction of phenolics was done from defatted twice with hexane. HPLC analysis of corn accessions as described earlier by Thakur et al. (2017). The identification and quantification of phenolic compounds was done by comparison of the retention time with a known standard. The calibration curve equations, coefficient of determination of linearity, limits of detection and quantitation obtained for different polyphenols are provided in (Supplementary Table S2).

Starch characteristics

Physicochemical characteristics of starch

Starches from selected corn accessions were obtained as described earlier by Thakur et al. (2015). Amylose content and Blue value of corn starch was measured using the method described by Thakur et al. (2015). The iodine-absorption spectra (λmax) were ascertained by determining the maximum absorbing wavelength in the visible region.

Granule size distribution and morphology

Morphological characteristics of corn starch were studied using scanning electron microscope (ZEISS, Germany) using methodology of Bajaj et al. (2018). Granule size of starch was detemined using particle size analyzer, (Microtrac S3500 Ins. Ltd., USA).

X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy

X-ray diffractograms of fully saturated (100% RH) starch samples were developed by an analytical diffractometer (XRD-7000; X-Ray Diffractometer Shimadzu, Japan) as described earlier by Bajaj et al. (2018). The crystalline structures of starches (dried to constant weights) were ascertained using a FTIR (Vertex70, Bruker, Germany) by analysing average Spectra of 200 scans. Absorbance intensity of the bands at 1047 cm−1, one thousand thirty five, and 1022 cm−1 were used to evaluate relative crystallinity.

Pasting characterisrics

Pasting characteristics of corn starches were measured using rheometer (Anton Paar Rheo Plus/32 Model MCR-301) as described earlier by Thakur et al. (2015).

Thermal properties

Thermal characteristics of starches were examined with a differential scanning calorimeter (DSC-822e, Mettler Toledo, Greinfense, Switzerland) as described earlier by Bajaj et al. (2018).

Statistical analysis

Results were observed as mean of triplicate readings ± standard deviation. Data was subjected to one way ANOVA using Minitab Statistical Software (MINITAB 14.12.0, USA). PCA loading plot (Supplementary Figure S1) gave an outline of the relationships among different evaluated parameters.

Results and discussion

Grain color

Various corn accessions showed significant differences in grain colour characteristics. Hunter color characteristics of grains from different colored corn accessions are given in Table 1. The results of ANOVA showed a significant difference in L*, a* and b* values owing to both accessions and colour, where the differences were more pronounced due to accessions than colour (Supplementary Table S1). Among the various accessions the highest L* (indicative of lightness) value was recorded for IC 550370 (74.24) and the lowest for IC 447647 (43.72). IC 361719 had the lowest a* value and IC 361727 showed the highest value of a* while b* values varied from 32.33 (IC 447646) to 7.04 (IC 447647). IC 550370, IC 447328, IC 447511, IC 447501 and IC 361719 showed significantly higher L* than other accessions indicating a higher degree of lightness. Thakur et al. (2015) reported high L* value of grit and flour from corn. IC 447644, IC 447667, IC 447649, IC 447647, IC 361727 and IC 447641 had comparatively higher a*, indicating presence of higher redness as compared to other accessions. IC 361714, IC 347386, IC 427129, IC 447646 and IC 447645 showed higher b* value than other accessions indicating presence of more yellow pigment. Sandhu et al. (2007) documented the larger b* values for flour, which may be owing to high levels of carotenoid present in it. Shevkani et al. (2014) also witnessed these results for various fractions produced from corn dry milling. PCA revealed a positive relation between L* and DPPH and the same was observed for a* and TPC (Supplementary Figure S1).

Table 1.

Color characteristics of grains from different colored corn accessions

S. no Colour Accessions L* a* b*
1 White IC 447511 70.19 ± 2.54de 2.52 ± 0.72ab 19.06 ± 0.95c
2 White IC 447638 65.70 ± 0.98cd 4.15 ± 0.47bc 20.15 ± 0.40cd
3 White IC 447632 68.68 ± 1.92d 2.97 ± 0.24b 19.63 ± 1.03c
4 White IC 447660 68.23 ± 2.00d 3.11 ± 0.31b 21.59 ± 0.52de
5 White IC 447639 69.15 ± 0.98de 4.78 ± 0.34c 22.68 ± 0.42de
6 White IC 447328 71.82 ± 0.69de 3.07 ± 0.09b 20.25 ± 1.20bc
7 White IC 550370 74.24 ± 1.90e 1.98 ± 0.16ab 17.72 ± 0.14c
8 White IC 550365 70.16 ± 1.88de 3.23 ± 0.03b 19.13 ± 0.92c
9 White IC 447626 70.51 ± 0.71de 2.38 ± 0.13ab 19.23 ± 0.15c
10 White IC 447501 73.68 ± 1.93e 1.92 ± 0.13ab 20.19 ± 0.62cd
11 White IC 447509 65.25 ± 0.82cd 3.18 ± 0.19b 19.40 ± 0.70c
12 White IC 361712 70.74 ± 1.75de 2.56 ± 0.23ab 18.95 ± 1.09c
13 White IC 361714 67.99 ± 0.80d 5.32 ± 0.57c 25.01 ± 1.08e
14 White IC 447632 66.65 ± 1.61d 4.44 ± 0.22bc 21.02 ± 1.00d
15 White IC 361719 72.46 ± 1.54e 1.68 ± 0.25a 17.05 ± 0.84b
16 Yellow IC 347386 62.26 ± 0.73c 12.15 ± 1.07f 24.45 ± 0.90e
17 Yellow IC 427129 62.50 ± 1.17c 12.78 ± 0.45fg 24.34 ± 0.78e
18 Yellow IC 397828 58.35 ± 0.83bc 13.25 ± 0.15fg 23.43 ± 0.65de
19 Yellow IC 397956 64.57 ± 0.89cd 12.46 ± 0.13f 24.28 ± 0.42e
20 Yellow IC 397957 63.84 ± 1.82c 14.69 ± 1.45g 29.67 ± 1.17g
21 Yellow IC 397958 63.12 ± 0.79c 10.62 ± 0.91f 26.83 ± 0.60f
22 Yellow IC 361709 68.29 ± 1.20d 9.67 ± 0.36ef 23.97 ± 0.49e
23 Yellow IC 362129 68.28 ± 1.20d 9.38 ± 0.28e 23.78 ± 0.92e
24 Yellow IC 362130 61.38 ± 1.04c 10.78 ± 1.33ef 22.26 ± 1.60d
25 Yellow IC 361726 63.28 ± 1.36c 7.68 ± 0.43de 20.67 ± 0.67cd
26 Yellow IC 447627 67.78 ± 0.52d 9.10 ± 0.66e 26.37 ± 1.09f
27 Yellow IC 447645 68.11 ± 0.55d 11.42 ± 0.41ef 29.02 ± 0.68g
28 Yellow IC 447646 66.96 ± 0.59d 11.96 ± 0.82f 32.33 ± 0.57f
29 Yellow IC 447641 63.72 ± 0.65c 14.05 ± 0.30g 27.72 ± 0.79fg
30 Yellow IC 447648 66.13 ± 1.80cd 12.05 ± 0.92f 27.64 ± 0.70fg
31 Purple IC 361727 60.71 ± 0.33bc 16.15 ± 0.16h 26.73 ± 0.25f
32 Purple IC 447636 58.78 ± 4.73bc 11.74 ± 1.49f 19.55 ± 1.80c
33 Purple IC 447648 67.35 ± 1.93d 6.44 ± 1.14d 18.82 ± 0.81c
34 Purple IC 447649 62.17 ± 0.28c 9.65 ± 0.67ef 21.92 ± 0.71d
35 Purple IC 447667 45.65 ± 1.91a 9.93 ± 1.13ef 7.05 ± 1.21a
36 Purple IC 447647 43.72 ± 0.72a 9.66 ± 0.19ef 7.04 ± 0.68a
37 Purple IC 447643 67.00 ± 1.02d 8.85 ± 0.41e 22.65 ± 0.91de
38 Purple IC 447644 56.93 ± 1.93b 12.03 ± 0.85f 16.18 ± 0.70b
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Values are mean ± SD. Means with similar superscript in a column did not differ significantly (P ≤ 0.05)

Flour characteristics

Physicochemical characteristics of flours

ANOVA showed a considerable difference in the flour proximate content (Table 2). These were primarily owing to the accessions than colour. This suggested that amongst the flours there were differences within the genotypes (Supplementary Table S1). Protein, fat, moisture and ash contents ranged from 6.18 to 11.83%, 1.67 to 7.06%, 9.17 to 11.96% and 0.67 to 2.29%, respectively (Table 2). The results observed proved that flour moisture contents in various accessions were in the range of safe storage limits. IC 447644 purple corn showed the lowest and IC 397957 yellow corn presented the largest moisture content. IC 447645 with yellow colour had the largest protein level, while the smallest was observed for IC 347386 yellow corn. IC 361714 white corn showed the smallest, while IC 447648 purple corn showed the largest ash content. Fat levels were the smallest for IC 447648 purple corn against IC 397956 yellow corn which showed the lowest value. IC 447644 purple corn showed the lowest and IC 397957 yellow corn presented the largest moisture content. Shevkani et al. (2014) also documented similar results for various corn fractions. PCA illustrated a positive relation among ash and fat levels for flours, suggesting that flours having larger amounts of lipids also contained large amounts of inorganic material (Supplementary Figure S1).

Table 2.

Proximate composition, total phenolic content (TPC) and antioxidant activity of flour from different colored corn accessions

S. no Colour Accessions Fat (%) Ash (%) DPPH inhibition (µg trolox/g) TPC (µg GAE/g) Moisture (%) Protein (%)
1 White IC 447511 3.88 ± 0.02de 1.57 ± 0.05fg 555.94 ± 10.38hi 1083 ± 12c 11.21 ± 0.43d 7.75 ± 0.13b
2 White IC 447638 4.15 ± 0.05e 1.50 ± 0.06f 582.22 ± 1.49i 1087 ± 17c 11.08 ± 0.08d 11.82 ± 1.31e
3 White IC 447632 5.76 ± 0.16h 1.70 ± 0.03g 607.94 ± 9.57j 1551.3 ± 32.5ef 10.10 ± 0.47bc 8.31 ± 0.44bc
4 White IC 447660 3.42 ± 0.02d 0.82 ± 0.03b 568.62 ± 0.68hi 1343 ± 72.0de 10.73 ± 0.11cd 8.06 ± 0.19bc
5 White IC 447639 5.56 ± 0.02gh 1.91 ± 0.13hi 671.00 ± 22.80k 1207 ± 37cd 11.76 ± 0.18de 10.06 ± 2.19d
6 White IC 447328 3.98 ± 0.07de 1.91 ± 0.04hi 543.52 ± 6.52h 1151.7 ± 27.5cd 10.76 ± 0.31cd 8.31 ± 0.44bc
7 White IC 550370 5.27 ± 0.09gh 1.22 ± 0.02de 536.68 ± 11.37h 772.3 ± 6.5a 10.79 ± 0.21cd 10.94 ± 0.44de
8 White IC 550365 5.27 ± 0.15gh 1.36 ± 0.01ef 517.18 ± 9.51gh 1060.3 ± 5.5c 11.61 ± 0.05de 8.75 ± 0.00cd
9 White IC 447626 4.44 ± 0.23ef 1.31 ± 0.06e 369.44 ± 6.40cd 1129.7 ± 89.5cd 11.67 ± 0.19de 9.63 ± 1.75cd
10 White IC 447501 4.55 ± 0.08f 1.13 ± 0.24d 311.10 ± 2.61b 1246.0 ± 91.0d 9.53 ± 0.70ab 8.30 ± 0.45bc
11 White IC 447509 2.04 ± 0.45b 1.72 ± 0.03g 401.50 ± 35.85d 880.7 ± 75.5b 11.71 ± 0.03de 10.60 ± 0.10de
12 White IC 361712 4.95 ± 0.59fg 1.40 ± 0.05ef 331.04 ± 10.62b 1338.3 ± 59.5de 9.42 ± 0.12ab 8.35 ± 0.38bc
13 White IC 361714 2.62 ± 0.14c 0.67 ± 0.08a 328.19 ± 11.37b 1518.0 ± 29.0ef 9.73 ± 0.24ab 10.77 ± 0.08de
14 White IC 447632 5.77 ± 0.12h 1.24 ± 0.04de 355.33 ± 17.52c 1693.7 ± 62.5fg 9.37 ± 0.29ab 8.75 ± 0.00bc
15 White IC 361719 2.88 ± 0.09c 1.44 ± 0.04f 328.37 ± 7.46b 1123.0 ± 69.0cd 10.40 ± 0c 9.59 ± 0.3cd
16 Yellow IC 347386 5.11 ± 0.20fg 1.55 ± 0.03f 351.79 ± 0.43c 938 ± 96b 11.68 ± 0.10de 6.18 ± 0.05a
17 Yellow IC 427129 3.74 ± 0.22de 1.12 ± 0.02d 347.01 ± 0.62c 1563.7 ± 24.5ef 9.79 ± 0.25b 11.82 ± 0.43e
18 Yellow IC 397828 2.83 ± 0.09c 1.39 ± 0.05ef 353.84 ± 0.75c 1059 ± 167c 10.48 ± 0.27cd 8.62 ± 0.04bc
19 yellow IC 397956 1.67 ± 0.18a 1.65 ± 0.03fg 355.65 ± 1.93c 1332 ± 80.0de 9.43 ± 0.05ab 8.36 ± 0.14bc
20 yellow IC 397957 6.98 ± 0.53i 1.73 ± 0.02g 258.04 ± 2.11a 1163.7 ± 39.0cd 11.96 ± 0.05e 8.85 ± 0.01bc
21 yellow IC 397958 4.65 ± 0.10f 1.56 ± 0.03f 429.45 ± 8.51e 769.3 ± 76.5a 11.64 ± 0.30de 8.27 ± 0.05bc
22 yellow IC 361709 2.86 ± 0.11c 1.43 ± 0.04ef 389.01 ± 1.37d 1623.7 ± 104.5f 10.24 ± 0.06bc 8.45 ± 0.03cd
23 yellow IC 362129 4.38 ± 0.13ef 0.89 ± 0.50bc 407.40 ± 6.59d 1401 ± 243e 9.72 ± 0.01ab 9.41 ± 0.22cd
24 yellow IC 362130 3.57 ± 0.12d 1.03 ± 0.05c 455.79 ± 2.30f 1438.7 ± 10.5e 10.63 ± 0.40cd 8.94 ± 0.02cd
25 yellow IC 361726 3.63 ± 0.18d 2.16 ± 0.08i 488.54 ± 4.72g 1221.7 ± 63.5cd 11.76 ± 0.18de 9.80 ± 0.00cd
26 yellow IC 447627 3.83 ± 0.12de 1.92 ± 0.03h 494.25 ± 1.49g 1106.7 ± 117.5e 9.77 ± 0.05b 9.50 ± 0.05cd
27 yellow IC 447645 4.52 ± 0.18f 1.61 ± 0.10fg 506.18 ± 2.36g 1694 ± 10fg 10.69 ± 0.11cd 11.83 ± 0.02e
28 yellow IC 447646 4.10 ± 0.20e 1.58 ± 0.03f 501.46 ± 14.79g 1275 ± 55.5d 9.84 ± 0.32bc 9.06 ± 0.05cd
29 Yellow IC 447641 4.27 ± 0.19ef 2.08 ± 0.14i 529.04 ± 1.12h 1176 ± 10.5cd 10.60 ± 0.01cd 8.44 ± 0.13bc
30 Yellow IC 447648 5.23 ± 0.13g 1.31 ± 0.04e 258.04 ± 2.11a 1608 ± 84f 11.28 ± 0.15de 8.70 ± 0.14bc
31 Purple IC 361727 5.70 ± 0.22gh 1.85 ± 0.05gh 471.58 ± 13.36f 995 ± 37bc 10.38 ± 0.35c 7.92 ± 0.05b
32 Purple IC 447636 4.35 ± 0.26ef 1.41 ± 0.15ef 535.63 ± 20.50h 1531 ± 9.0ef 10.23 ± 0.46bc 9.74 ± 0.11cd
33 Purple IC 447648 7.06 ± 0.63i 2.29 ± 0.09ij 496.43 ± 1.55g 1467.7 ± 39.5e 9.23 ± 0.05a 8.70 ± 0.05cd
34 Purple IC 447649 4.71 ± 0.15f 1.56 ± 0.03f 517.55 ± 10.38gh 1603 ± 102f 10.39 ± 0.44c 9.01 ± 0.09cd
35 Purple IC 447667 3.77 ± 0.21de 1.71 ± 0.03g 505.19 ± 1.24g 1884 ± 24g 10.06 ± 0.23a 9.88 ± 0.08d
36 Purple IC 447647 4.61 ± 0.09f 1.54 ± 0.05f 518.73 ± 7.58gh 1226 ± 14d 9.21 ± 0.56a 9.54 ± 0.27d
37 Purple IC 447643 1.70 ± 0.11a 1.58 ± 0.03f 516.62 ± 5.96gh 1830 ± 63.5g 10.72 ± 0.37cd 9.54 ± 0.08d
38 Purple IC 447644 4.53 ± 0.16f 1.06 ± 0.07c 509.41 ± 1.99g 1616 ± 83f 9.17 ± 0.07a 9.88 ± 0.08d
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Values are mean ± SD. Means with similar superscript in a column did not differ significantly (P ≤ 0.05). All values are reported on dry weight basis

Pasting properties of flours

Pasting characteristics of flours in various corn accessions had considerable differences, which ranged from 461.7 to 1938 cP, 722 to 2932 cP, 5.17 to 1346 cP, 259.3 to 2918 cP, 72.55 to 81.95 °C, respectively for PV, FV, BDV, SBV and PT (Supplementary Table S3, Fig. 1). When the heating process was going on, the starch granule gelatinization took place where these granules had undergone swelling, which led to their crystalline structure breakage and leaching of amylose. Pasting temperature (PT), indicating the lowest temperature for cooking of flours. It was the highest for IC 362130 yellow corn, while the lowest value was observed for IC 361714 white corn. On the other hand, highest PV (where granule swelling rate equals its breakdown rate) for IC 447645 yellow corn and the lowest was for IC 361714 white corn (Supplementary Table S3). BDV of IC 447639, IC 447511, IC 447649 and IC 447328 was considerably lower (5–40 cP) than the other ones which indicated their larger thermal stability. BDV represented granular disintegration after swelling. Sandhu et al. (2007) reported the lowest Breakdown viscosity (BDV) for Pb sathi flour indicated its paste stability. The enhancement in viscosity upon cooling was probably by the aggregation of amylose molecules led to final viscosity (FV). IC 361712 and IC 447511 presented significantly smaller FV (722.5–757.9 cP) than other lines. Singh et al. (2014) also documented similar results for corn starches. Setback viscosity (SBV) indicated the amount of retrogradation present in starch pastes while the cooling process was going on. The smallest SBV value was for IC 447511 white corn, whereas the largest for IC 447646 yellow corn. Lowest SBV values showed lower retrogradation tendencies of starch granules upon cooling. PCA gave information that PT had a positive relation with ash and fat levels (Supplementary Figure S1). Shevkani et al. (2014) documented that lipids might enhance the integrity of starch granules that would delay gelatinization initiation, thereby increasing the PT of corn fractions.

Fig. 1.

Fig. 1

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Pasting curves of flours from different corn accessions

Total phenolic content and antioxidant activity of flours

ANOVA presented considerable differences in DPPH inhibition and TPC due to accessions and colour; however, colour had lower effect than accessions (Supplementary Table S1). The highest TPC was observed for IC 447667 purple corn, while the lowest was observed for IC 550370 white corn (Table 2). Purple corn showed high TPC which could be due to greater accumulation of anthocyanins (Singh et al. 2014). IC 447639 white corn showed the highest DPPH inhibition, while IC 447648 yellow corn showed the lowest (Table 2). Previous results also reported similar results for antioxidant activity (Adom et al. 2005). DPPH inhibition could be contributed to the presence of greater amounts of lutein and zeaxanthin (de la Parra et al. 2007). PCA revealed that TPC was related positively to a* and b* values, but negatively to L* value, suggesting that dark coloured accessions had higher amounts of phenolic compounds as compared to the light coloured ones (Supplementary Figure S1). Moreover, there was a positive relation between DPPH and TPC for flours (Supplementary Figure S1).

Mineral analysis

Mineral content of corn flour from different accessions is given in Table 3. ANOVA demonstrated significant differences in accumulation of minerals due to accessions and colour. Conversely, accessions had a larger impact than colour (Supplementary Table S1). The macroelements Na, K, Ca and Mg content ranged from 97.49 to 19.50 mg/kg, 21 to 1677 mg/kg, 0.87 to 89.30 mg/kg and 48 to 621 mg/kg, respectively. The microelements Cu, Mn, Fe, and Zn ranged from 0.02 to 2.94 mg/kg, 0.09 to 1.32 mg/kg, 3.10 to 9.40 mg/kg and 1.63 to 7.42 mg/kg, respectively (Table 3). K, Mg, Ca Zn, Na, Cu, Mn, and Fe were in high concentration in IC 447511 (89.30 mg/kg), IC 362129 (4182.7 mg/kg), IC 447644 (621.77 mg/kg), IC 447509 (7.42 mg/kg), IC 447632 (97.49 mg/kg), IC 447511 (2.94 mg/kg), IC 361712 (1.32 mg/kg) and IC 447511 (9.40 mg/kg), respectively, while the lowest accumulation of Cu, K, Mg, Zn, Na, Ca, Mn, and Fe was observed for IC 361727 (0.87 mg/kg), IC 447645 (21 mg/kg), IC 361727 (48 mg/kg), IC 447647 (1.63 mg/kg), IC 447643 (19.50 mg/kg), IC 447648 (0.02 mg/kg), IC 361727 (0.09 mg/kg) and IC 447645 (3.10 mg/kg), respectively. The variation in mineral composition among different coloured corn accessions may be due to environmental factors and soil nutrients as well as variation in the use of fertilizers (Ahmadi et al. 1993). Minerals act as body regulators and play major role in metabolic and cellular functions of the body. The accessions having large or small amounts of minerals can be considered to differentiate the genetic and physiological mechanisms that were reported to be responsible for development of seeds by regulating mineral transport (Wang et al. 2003). A marked variation in mineral concentration of grains among different corn accessions was also reported earlier by Menkir et al. (2008). Nuss and Tanumihardjo (2010) reported that Mg and K were the most prevalent minerals present in corn.

Table 3.

Mineral composition of flour from different colored corn accessions (in ppm)

S. no Colour Accessions Cu (ppm) Mn (ppm) Fe (ppm) Zn (ppm) Mg (ppm) Ca (ppm) K (ppm) Na (ppm)
1 White IC 447511 2.94 ± 0.15l 1.22 ± 0.03ij 9.40 ± 0.20h 4.92 ± 0.33e 394 ± 31de 89.30 ± 5.20bc 565.7 ± 9.5bc 61.04 ± 2.49ef
2 White IC 447638 1.02 ± 0.01i 0.83 ± 0.05fg 5.87 ± 0.38ef 3.21 ± 011cd 444 ± 12ef 84.50 ± 2.50bc 339.3 ± 5.5b 58.19 ± 0.44e
3 White IC 447632 0.56 ± 0.02e 0.60 ± 0.05d 5.00 ± 0.52d 2.16 ± 0.33ab 332 ± 18cd 84.07 ± 1.55bc 661 ± 11c 97.49 ± 2.14h
4 White IC 447660 0.45 ± 0.2de 0.70 ± 0.02e 5.33 ± 0.18e 2.93 ± 0.27c 294.27 ± 32cd 61.50 ± 3.50abc 385 ± 40b 47.73 ± 5.28d
5 White IC 447639 0.39 ± 0.01cd 0.76 ± 0.01ef 5.27 ± 0.23e 3.13 ± 0.36c 426.77 ± 29.25e 49 ± 3ab 319.7 ± 5.5b 50.97 ± 5.27de
6 White IC 447328 0.62 ± 0.15f 0.96 ± 0.06g 7.06 ± 0.17g 3.34 ± 0.17cd 439 ± 14ef 48.50 ± 3.50ab 713 ± 10c 53.25 ± 2.35de
7 White IC 550370 0.83 ± 0.35h 0.95 ± 0.03fg 5.3 ± 0.25e 3.12 ± 0.39c 350.27 ± 5.75de 54.50 ± 1.50ab 350 ± 6b 61.66 ± 1.91ef
8 White IC 550365 0.53 ± 0.02ef 0.82 ± 0.02fg 5.00 ± 0.25de 3.01 ± 0.51c 705.50 ± 19.50h 58.77 ± 1.25ab 607.7 ± 17.5bc 77.95 ± 2.50fg
9 White IC 447626 0.93 ± 0.04i 0.87 ± 0.03fg 4.28 ± 0.27cd 3.00 ± 0.25bc 265.50 ± 26cd 60 ± 5bc 512.3 ± 12.5bc 57.48 ± 2.13e
10 White IC 447501 0.46 ± 0.04e 0.90 ± 0.05fg 5.89 ± 0.07ef 2.51 ± 0.13bc 606.77 ± 18.25fg 57 ± 5bc 508.7 ± 36.5bc 59.67 ± 0.57ef
11 White IC 447509 0.43 ± 0.04e 0.93 ± 0.02fg 5.50 ± 0.06ef 7.42 ± 0.08f 302 ± 23cd 51.50 ± 4.50abc 249.7 ± 6.5ab 74.11 ± 0.46f
12 White IC 361712 0.78 ± 0.07g 1.32 ± 1.75j 5.90 ± 0.34ef 5.10 ± 0.15e 314.27 ± 10.75cd 48.87 ± 1.35abc 30.17 ± 23.5b 48.71 ± 1.86d
13 White IC 361714 0.33 ± 0.45d 0.80 ± 0.05ef 4.36 ± 0.14cd 3.22 ± 0.28cd 241 ± 9bc 41 ± 4ab 267 ± 9ab 49.83 ± 2.53de
14 White IC 447632 0.49 ± 0.06e 0.92 ± 0.03fg 4.01 ± 0.23c 3.30 ± 0.54cd 263.50 ± 11.50cd 39.77 ± 5.25ab 250 ± 6ab 57.28 ± 0.73e
15 White IC 361719 0.37 ± 0.05de 0.99 ± 0.65g 5.99 ± 0.25f 3.17 ± 0.39c 293.50 ± 31.50cd 39.50 ± 5.50ab 216.7 ± 36.5ab 51.23 ± 4.03de
16 Yellow IC 347386 0.42 ± 0.35de 0.92 ± 0.35fg 5.11 ± 0.14de 2.35 ± 0.21b 258.50 ± 16.50bc 231.50 ± 146d 219 ± 4ab 41.10 ± 3.90cd
17 Yellow IC 427129 0.42 ± 0.04de 0.82 ± 0.03ef 5.01 ± 0.49de 3.06 ± 0.19c 234 ± 16bc 24.27 ± 0.75ab 162.7 ± 12.5a 37.68 ± 7.33c
18 Yellow IC 397828 0.40 ± 0.05de 0.82 ± 0.03ef 5.57 ± 0.17ef 3.18 ± 0.18cd 286 ± 14cd 15.50 ± 12.50ab 1677 ± 7.5d 32.95 ± 2.05bc
19 Yellow IC 397956 0.78 ± 0.04g 0.88 ± 0.06fg 4.70 ± 0.04d 3.29 ± 0.35cd 248.50 ± 7.50bc 46.77 ± 5.25ab 551.3 ± 45c 41.40 ± 3.60cd
20 Yellow IC 397957 0.40 ± 0.60de 0.88 ± 0.06fg 5.89 ± 0.35ef 3.23 ± 0.26cd 244 ± 6bc 38 ± 8ab 170.7 ± 4.5a 39.33 ± 3.48cd
21 Yellow IC 397958 0.40 ± 0.60de 0.89 ± 0.02fg 5.57 ± 0.17ef 3.41 ± 0.24cd 244 ± 12bc 58.50 ± 6.50bc 264 ± 11ab 47.50 ± 2.50d
22 Yellow IC 361709 0.36 ± 0.02d 0.90 ± 0.05fg 5.30 ± 0.21e 3.11 ± 0.14c 262.27 ± 12.75cd 52.50 ± 3.50abc 239 ± 11ab 59.30 ± 2.70ef
23 Yellow IC 362129 0.35 ± 0.03d 0.90 ± 0.03fg 4.97 ± 0.52de 3.46 ± 0.18cd 281.77 ± 7.25cd 40.87 ± 4.35ab 4182.7 ± 52.5 49.60 ± 2.40de
24 Yellow IC 362130 0.39 ± 0.35de 1.15 ± 0.09h 5.31 ± 0.18e 3.29 ± 0.27cd 300.27 ± 24.75cd 46.27 ± 5.75ab 216.7 ± 8.5b 62.83 ± 2.18ef
25 Yellow IC 361726 0.81 ± 0.04g 0.48 ± 0.08cd 4.68 ± 0.07d 3.13 ± 0.43c 119.27 ± 5.75ab 11.50 ± 3.50ab 306.3 ± 18.5bc 29 ± 6.60b
26 Yellow IC 447627 1.30 ± 0.05j 0.54 ± 0.4d 4.46 ± 0.04cd 3.07 ± 0.15c 101 ± 4ab 11 ± 4ab 196.7 ± 59.5b 23.95 ± 8.05ab
27 Yellow IC 447645 0.48 ± 0.75e 0.32 ± 0.35b 3.10 ± 0.14b 2.16 ± 0.08ab 64.77 ± 3.25ab 0.87 ± 0.35a 21 ± 4a 21.20 ± 3.80a
28 Yellow IC 447646 0.40 ± 0.03de 0.41 ± 0.15bc 4.08 ± 0.17c 2.26 ± 0.23b 433 ± 5e 47 ± 5ab 80 ± 5ab 50.98 ± 4.23de
29 Yellow IC 447641 0.13 ± 0.03b 0.36 ± 0.06bc 4.10 ± 0.10c 2.34 ± 0.18b 177.50 ± 7.50b 42.50 ± 0.50ab 39.7 ± 2.5a 28.35 ± 2.15ab
30 Yellow IC 447648 0.02 ± 0.01a 0.31 ± 0.04b 3.12 ± 0.13a 2.24 ± 0.29b 92.50 ± 7.50ab 22 ± 3ab 415 ± 10c 88 ± 7g
31 Purple IC 361727 0.51 ± 0.04e 0.09 ± 0.01a 2.95 ± 0.54a 2.05 ± 0.48ab 48 ± 7a 0.87 ± 0.35a 31 ± 11a 62.49 ± 2.74ef
32 Purple IC 447636 0.46 ± 0.06e 0.35 ± 0.35bc 4.09 ± 0.15c 2.00 ± 0.25ab 110.50 ± 14.50ab 7.77 ± 0.75a 112.3 ± 10.5ab 21.50 ± 4.10a
33 Purple IC 447648 0.58 ± 0.04f 0.42 ± 0.35bc 3.93 ± 0.31c 1.98 ± 0.04ab 88.50 ± 6.50ab 8.50 ± 1ab 82.7 ± 2.5ab 32.90 ± 2.70bc
34 Purple IC 447649 0.50 ± 0.02e 0.45 ± 0.05cd 4.02 ± 0.20 2.46 ± 0.09bc 123.77 ± 6.25ab 12.37 ± 2.85ab 262.7 ± 12.5b 46.78 ± 5.23d
35 Purple IC 447667 1.69 ± 0.06k 0.56 ± 0.003d 4.39 ± 0.11cd 3.60 ± 0.15cd 88.50 ± 2.00ab 3.17 ± 0.65a 33 ± 2a 21.03 ± 3.98a
36 Purple IC 447647 0.28 ± 0.05c 0.39 ± 0.06bc 3.31 ± 0.19b 1.63 ± 0.21a 70.77 ± 4.25ab 1.50 ± 0.50a 28 ± 4a 23.78 ± 8.23ab
37 Purple IC 447643 0.58 ± 0.04f 0.58 ± 0.75d 4.09 ± 0.16c 3.01 ± 0.25c 88.50 ± 2ab 4 ± 0.50a 23 ± 3a 19.50 ± 5.50a
38 Purple IC 447644 0.15 ± 0.03b 0.43 ± 0.13c 4.34 ± 0.15cd 2.85 ± 0.39c 621.77 ± 3.25g 78.77 ± 6.25bc 100 ± 5ab 28.38 ± 3.63ab
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Values are mean ± SD. Means with similar superscript in a column did not differ significantly (P ≤ 0.05). All values are reported on dry weight basis

Cu Copper, Mn Manganese, Fe Iron, Zn Zinc, Mg Magnesium, Ca Calcium, K Potassium, Na Sodium

SDS-PAGE analysis

Different corn accessions showed the presence of different molecular weight storage proteins of 15–20 polypeptide (PP) subunits that ranged from 9.7 to 95 kDa [Supplementary Figure S3(a), (b)]. Major PP subunits observed in coloured corn accessions were 97, 86, 60, 45, 30, 27, 22, 19 and 13 kDa. Low molecular weight (LMW) PP subunits (20 to > 10 kDa) were highly accumulated in different coloured corn varieties. Zein (alcohol soluble protein) was present in corn as LMW PPs. Esen (1986) termed zein proteins of 19 and 22 kDa, 14 kDa, and 16 and 27 kDa PP as α, β and γ-zein, respectively. Yellow corn accessions did not show variation among high molecular weight (HMW) protein subunits, whereas small variations were observed for medium molecular weight (MMW) PP subunits. All accessions showed higher accumulation of 23–28 kDa PPs, while absence of 23 kDa PP in IC 447509 accessions was remarkable. This might be due to more proportion of hard endosperm in corn. Dombrink-Kurtzman and Bietz (1993) reported that hard endosperm had lesser amount of γ-zeins, while soft endosperm of same genotype showed the reverse trend. Thakur et al. (2015) reported that γ-zein (27 kDa) was present in very small amount in corn varieties with soft endosperm texture. Major polymorphism was found in MMW PPs. 15.6 kDa PP was highly accumulated in yellow coloured accessions, whereas 12 kDa PP was present in white coloured accessions. Shewry and Tatham (1990) reported 15 kDa PP as β-zein. Higher accumulation of 23, 25, 27 and 28 kDa PP subunits was observed in yellow corn accessions. HMW 95 kDa PP was present in all accessions, whereas LMW 10, 11, 12, 13, 14, 15, 17 and 19 kDa PPs were observed in corn accessions. Polymorphism in different MW PPs was found among white and red-pigmented corn accessions, where IC 447509 white accession showed the absence of MMW 23, 24 kDa PPs. IC 447649 showed the accumulation of MMW except 20–24 KDa PPs among purple accessions. Dombrink-Kurtzman and Bietz (1993) reported that α-zein (22 kDa) was present in higher amount in hard endosperm fractions and was not uniformly distribution throughout the endosperm.

Amino acid analyses

Amino acids (essential and non essential) content in different corn accessions are shown in Supplementary Table S7a, b. Higher proportions of citrulline, arginine, GABA, phenylalanine, isoleucine, tyrosine, threonine, glycine in relation to other amino acids were observed in different corn accessions. According to NRC (2012), corn contains minute quantity of crude protein (CP) and amino acids (AA) as compared to other plant protein sources. IC 550370, IC 447639, IC 447638, IC 447644, IC 550365, IC 447509, IC 447648, IC 361727, IC 397958, IC 397957, IC 447501, IC 447649, IC 447511, IC 427129, IC 447636, IC 447645 showed higher relative proportion of glutamic acid, tryptophan and GABA, asparagine and lysine, glutamine and threonine, histidine, citrulline, arginine, phenylalanine, isoleucine, proline, lucine, tyrosine, cystine, valine, methionine, alanine and glycine respectively. Similar trends were also observed by Mouhamad et al. (2016) in the nine and 39 corn cultivars. Corn sources from different origins varied in CP and AA content especially in lysine and tryptophan (Kil et al. 2014). Factors such as corn genotype, soil condition, precipitation and other environmental conditions resulted in considerable variation in CP and AA concentrations among corn sources produced in various regions of The United States (Cowieson and Adeola 2005).

HPLC analysis

Significant variation in concentration of base-hydrolysed bound phenolic compounds of different coloured corn accessions was observed (Supplementary Table S6). Calibration curve equations, limits of detection, coefficient of determination of linearity and quantification collected for different phenolics are given in Supplementary Table S2. The major phenolics in corn flours were associated with cell wall components in bound form, while absent in free form. HPLC analysis showed the presence of gallic acid, catechin, caeffic acid, chlorogenic acid, protocatechuic acid, vanillic acid, p-coumaric acid, quercetin, ferulic acid, sinapic acid, reservatrol and luteolin in the range of 0.76–27.02, 0.19–17.62, 0.01–1, 0.11–11.54, 0.63–27.22, 0.01–2.28, 2.17–3.64, 0.11–9.66, 0.23–18.43, 0.04–22.74, 0.01–2.49 and 9.36–15.38 mg/g, respectively. Similar results were reported earlier in corn by Ramos-Escudero et al. (2012). Primarily all corn accessions contained ferulic acid but white accessions had exceptionally large amounts of this phenolic acid. Lopez-Martinez et al. (2009) observed ferulic acid present in eighteen strains of Mexican corn. IC 447632 presented the largest concentration of ferulic acid, while IC 397828 showed the lowest. Base-hydrolyzed bound gallic acid, protocatechuic acid, p-coumaric acid, sinapic acid, quercetin and luteolin content showed a significant variation among different coloured corn accessions. Gallic acid content of yellow coloured corn accessions was significantly lower as compared to other accessions except IC 347386. White coloured corn accessions showed significantly high gallic acid content than purple coloured corn accessions. Slightly lower concentration of protocatechuic acid was observed in yellow accessions in comparison with white and purple coloured corn accessions. A significantly higher sinapic acid and luteolin content in different corn accessions were observed. Sinapic acid (r = 0.318, P ≤ 0.05), catechin (r = 0.440, P ≤ 0.005), p-coumaric acid (r = 0.388, P ≤ 0.05) and luteolin (r = 0.502, P ≤ 0.005) correlated significantly with Mg and TPC respectively. Zhao and Moghadasian (2008) reported some phenolic compounds chelates metal ions thus exhibit anitioxidant activity. Phenolics acids have wide range of variation in their effectiveness as antioxidant (Robards et al. 1999). The highest content of quercetin was observed for IC 427129, while the lowest was for IC 447643.

Starch characteristics

Physico-chemical characteristics

The amylose content, blue value and λmax of different corn starches varied significantly and differences in the characteristics were highly prominent due to accessions than colour (Supplementary Table S1). Amylose content of starches from various corn accessions ranged widely from 7.64 (IC 550365) to 20.90% (IC 447645) (Supplementary Table S5). Similar results for amylose content of different corn starches were reported by Thakur et al. (2015). Blue value of starches from various corn accessions ranged from 0.099 (IC 550365) to 0.22 (IC 447627). Higher number of long chains in amylopectin was responsible for high iodine binding capacity (Lu et al. 2008). λmax of starches from different corn accessions ranged from 570.46 (IC 550365) to 598.49 (IC 361726).

Granule size distribution and morphology

SEM micrographs of starches from various corn accessions are shown in Fig. 2. Starch granules showed a characteristic angular (polygonal) shape with smooth surfaces. Some starch granules were irregular in shape having the presence of grooves or furrows or pores on the surface. Bajaj et al. (2018) suggested that the pores and differences in granule morphology of starches were associated with botanical source and physiology of the plant. Similar results were seen in corn, sorghum and millet starch granules by (Fannon et al. 1992) SEM confirmed the granule size distribution which ranged from 10 to 100 µm. The average granule size of starches varied significantly. The differences were higher due to accessions than colour (Supplementary Table S1). The size of the starch granules ranged from 13.49 µm (IC 447636) to 48 µm (IC 361714) (Supplementary Table S5). All starches from different corn accessions showed unimodular distribution for granule size. Bajaj et al. (2018) reported the diameter of corn starch granule ranging from 6 to 30 µm.

Fig. 2.

Fig. 2

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Scanning electron microscope of starches from different corn accessions

Thermal characteristics

Thermal characteristics of starches among various corn accessions are given in Supplementary Table S4. Significant variation in transition temperatures; onset (To), peak (Tp), conclusion (Tc) and enthalpy of gelatinization (∆Hgel) among starches from various corn accessions was observed. ANOVA presented considerable differences in thermal properties due to accessions and colour but accessions had a greater effect than colour (Supplementary Table S1). To, Tp, Tc and ∆Hgel ranged from 62.84 (IC 447638) to 68.33 °C (IC 447643), 66.35 (IC 361726) to 71.44 °C (IC 347386), 70.01 (IC 361712) to 75.78 °C (IC 447643) and 6.10 (IC 447648) to 11.64 J/g (IC 362130). Bajaj et al. (2018) reported the DSC values in the similar trend for starches. Differences in the degree of crystallinity were responsible for the variation in the transition temperatures among starches from different corn accessions (Singh and Singh 2003). The deviation in ΔHgel (indicative of melting of amylopectin crystallites) might represent the variation in bonding forces among the double helices, forming amylopectin crystallites. This led to different hydrogen bonds alignments inside starch molecules (McPherson and Jane 1999). The low ΔHgel indicated the role of shape of starch granules and fraction of large and small granules along with the presence of amylopectin (Yuan et al. 1993). Moreover, low To and broad range of gelatinization (R) indicated the presence of irregular shaped starch granules (Yamin et al. 1999). PCA revealed positive correlation between thermal properties and crystallinity.

X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopy

The X-ray diffraction pattern of starches from various corn accessions are illustrated in Supplementary Figure S2. Starch granule exhibited a semi-crystalline structure which was classified into A, B and C types. All starches presented a typical A-type diffraction pattern having prominent diffraction peaks around 15.02° and 23.2° and dual peak at 17–18.1° 2θ which has been confirmed by Bajaj et al. (2018) and explained that the presence of higher content of amylose in starches led to lower degree of crystallinity possibly because of associated lower amylopectin content. Crystalline structure as well as short range order was studied by IR spectroscopy. The absorbance bands at 1047 cm−1 were associated with crystalline regions while absorbance at 1022 cm−1 was observed due to amorphous regions in starch. Ratio of absorbance of 1047/1022 cm−1 described the changes in crystallinity and 1047/1035 cm−1 ratio for short range order. The change in crystallinity (ratio of absorbance of 1047/1022 cm−1) and short range order (1047/1035 cm−1) varied significantly for the accessions which ranged from 0.29 (IC 447648) to 1.14 (IC 362129) and 2.64 (IC 447501) to 0.01 (IC 447632), respectively. The higher ratio of band intensity of 1047/1022 cm−1 and 1047/1035 cm−1 indicated larger crystallinity and more of short range regions. The differences in crystallinity in various corn starches can be due to the differences in the amylose content and long and short chain amylopectin (Singh et al. 2006). PCA confirmed the positive relation between the crystallinity with amylose content.

Pasting properties of starches

A significant variation in pasting properties was observed amongst starches from different corn accessions. Table 4 represents the differences in pasting behaviour of starches from different corn accessions. PT, FV, PV, BDV and SBV ranged from 69.64 (IC 447639) to 74.98 °C (IC 397956), 2102 (IC 361714) to 4293 cP (IC 447638), 1175 (IC 361712) to 3021 cP (IC 447660), 1199 (IC 397956) to 2798 cP (IC 361712) and 2644 (IC 447632) to 3883 cP (IC 361714), respectively. Similar results were reported by Sandhu et al. (2007). The accessions with higher PT showed resistance to swelling. Li and corke (1999) explained that low PV indicated the resistance of starch to shear thinning. PCA revealed the positive relation of amylose content with FV and SBV while negative relation with BDV of starch. The high BDV may be due to weaker rigidity of starch granules under heating and shearing in the presence of low amylose content (Lu et al. 2008). Bajaj et al (2018) reported higher SBV was associated with amylose content of starches. The high FV of corn starches is because the amylose molecules tend to aggregate (Miles et al. 1985).

Table 4.

Pasting characteristics of starches from different colored corn accessions

S. no Colour Accessions Peak viscosity (cP) Breakdown viscosity (cP) Final viscosity (cP) Setback viscosity (cP) Pasting temperature (°C)
1 White IC 447511 3284 ± 9.0de 1505 ± 28c 3961 ± 11.5g 2182 ± 30.5fg 72.99 ± 0.02cd
2 White IC 447638 3528 ± 26.5fg 1721 ± 45d 4293 ± 42i 2452 ± 23h 73.99 ± 0.57de
3 White IC 447632 2773 ± 14ab 1389 ± 23bc 3639 ± 40.5f 2241 ± 64g 72.92 ± 0.46cd
4 White IC 447660 2679 ± 32ab 2050 ± 17.5f 3679 ± 26f 3021 ± 18j 71.00 ± 0.09b
5 White IC 447639 2846 ± 21b 1851 ± 2e 3356 ± 31.5e 2361 ± 8.5gh 69.64 ± 0.36a
6 White IC 447328 3043 ± 13.5c 1382 ± 2.5bc 3606 ± 29f 1944 ± 17.5de 74.16 ± 1.01de
7 White IC 550370 3232 ± 16.5de 1489 ± 37c 3805 ± 10.5fg 2212 ± 15.9ef 74.11 ± 0.09de
8 White IC 550365 2872 ± 9.9bc 1271 ± 32.5ab 3220 ± 50.5de 1620 ± 16c 72.18 ± 0.97c
9 White IC 447626 3029 ± 10c 1590 ± 24cd 3667 ± 7.5f 2233 ± 36.5g 72.98 ± 0.19cd
10 White IC 447501 3139 ± 21cd 1356 ± 12b 3858 ± 29g 2075 ± 20ef 72.86 ± 0.37cd
11 White IC 447509 3213 ± 36d 1544 ± 2c 3671 ± 48.5f 2003 ± 14e 72.70 ± 0.45cd
12 White IC 361712 3725 ± 12.5g 2798 ± 8i 2102 ± 82a 1175 ± 49a 72.56 ± 0.09cd
13 White IC 361714 3883 ± 38h 2691 ± 57.5h 2511 ± 3c 1319 ± 16.5b 72.07 ± 0.020c
14 White IC 447632 2644 ± 17.5a 1913 ± 33e 3543 ± 5.5f 2812 ± 45.5i 71.33 ± 0.18bc
15 White IC 361719 3470 ± 22ef 2377 ± 4.5g 2299 ± 28b 1206 ± 1.5a 72.27 ± 0.37c
16 Yellow IC 347386 3245 ± 34de 1438 ± 46.5c 4057 ± 5.5gh 2251 ± 17.5g 73.86 ± 0.59de
17 Yellow IC 427129 3345 ± 20.2e 1555 ± 98c 3990 ± 17.5gh 2200 ± 73fg 74.22 ± 1.34de
18 Yellow IC 397828 3047 ± 19c 1297 ± 25.6b 3703 ± 41.5f 1955 ± 47.5de 73.87 ± 0.23de
19 Yellow IC 397956 3149 ± 18cd 1199 ± 34a 4287 ± 63i 2337 ± 11gh 74.98 ± 0.86e
20 Yellow IC 397957 3306 ± 28.5de 1632 ± 24.5d 4017 ± 22gh 2343 ± 17gh 74.66 ± 0.18e
21 Yellow IC 397958 3144 ± 20.5de 1361 ± 8b 3928 ± 32.5g 2145 ± 20f 74.29 ± 0.04de
22 Yellow IC 361709 2891 ± 10.8bc 1220 ± 73.5a 3560 ± 99.5f 1890 ± 64d 73.80 ± 0.28de
23 Yellow IC 362129 3189 ± 19.5d 1572 ± 10c 3491 ± 3.5ef 1873 ± 13.5d 73.77 ± 0.47de
24 Yellow IC 362130 2913 ± 28.5bc 1265 ± 16.9ab 3765 ± 28.7fg 2117 ± 174f 74.39 ± 1.05e
25 Yellow IC 361726 3500 ± 35ef 1682 ± 8d 3863 ± 39g 2045 ± 11ef 73.31 ± 0.55de
26 Yellow IC 447627 3180 ± 21de 1418 ± 32.5bc 4105 ± 45h 2343 ± 33.5gh 74.46 ± 0.24e
27 Yellow IC 447645 2958 ± 26.5bc 1277 ± 19.5b 3782 ± 1.5fg 2102 ± 5f 74.44 ± 0.18e
28 Yellow IC 447646 3329 ± 37.5de 1607 ± 9cd 3824 ± 27.5fg 2101 ± 19.5f 73.36 ± 0.69de
29 Yellow IC 447641 3158 ± 49cd 1431 ± 14.5c 3892 ± 37.5g 2166 ± 3f 73.45 ± 0.89de
30 Yellow IC 447648 3173 ± 73.5cd 1461 ± 8.5c 3715 ± 10f 2003 ± 35.5e 74.54 ± 0.24e
31 Purple IC 361727 3431 ± 0.1ef 1895 ± 26e 3487 ± 2ef 1968 ± 8de 73.25 ± 0.72cd
32 Purple IC 447636 3016 ± 15.8bc 1563 ± 30cd 3148 ± 19d 1894 ± 7d 70.87 ± 0.08b
33 Purple IC 447648 3004 ± 0.2bc 1589 ± 3.5cd 3383 ± 21.6e 1876 ± 24.5d 69.85 ± 0.26a
34 Purple IC 447649 3022 ± 15bc 1657 ± 15.5d 3775 ± 9fg 2410 ± 21.2h 73.09 ± 0.30cd
35 Purple IC 447667 3185 ± 12d 1702 ± 36.5d 3686 ± 17.5f 2204 ± 66fg 71.91 ± 0.23c
36 Purple IC 447647 3297 ± 13de 1580 ± 16.5cd 3927 ± 38g 2210 ± 41.5fg 73.50 ± 0.30de
37 Purple IC 447643 2987 ± 14e 1321 ± 3b 3676 ± 27f 2010 ± 10e 74.64 ± 0.24e
38 Purple IC 447644 3177 ± 21de 1708 ± 10.5d 3156 ± 49d 1695 ± 25cd 72.95 ± 0.16cd
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Values are mean ± SD. Means with similar superscript in a column did not differ significantly (P ≤ 0.05)

Conclusion

The present study revealed characterization of diverse range of coloured corn accessions. Grain, flour and starch characteristics were in strong correlation with each other. Significant differences were observed in grain characteristics. Flours from various corn accessions differed significantly for physicochemical, antioxidant, pasting, amino acid and polyphenolic profiles. Quercetin, Sinapic acid, protocatechuic acid, ferulic acid, and gallic acid were present in different accessions in varying concentration. Purple corn accessions showed higher antioxidant activities and polyphenolic content than yellow and white accessions may be useful to impart nutritional properties. Analyses of physicochemical, pasting, thermal and structural characteristics of starches presented considerable knowledge contributing to functional properties of starches. The production and processing of significant quality starch depends upon the desired food characteristics. The differences in composition and physical properties can be utilized in developing gluten free products. Corn being a non-glutinous, antioxidant rich cereal showed high amount of phenolics that are useful to impart resistance to several diseases.

Electronic supplementary material

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Supplementary file1 (DOCX 3598 kb) (3.5MB, docx)

Acknowledgements

NS acknowledges Science and Engineering Research Board for providing funds in the form of a research project (SERB/SR/SO/PS/13/2011). ST acknowledges UGC-BSR for providing financial assistance in the form of fellowship. Authors also acknowledge Dr. Jai Chand Rana, NBPGR, New Delhi (India) for providing corn accessions.

Abbreviations

TPC

Total phenolics content

FV

Final viscosity

SEM

Scanning electron microscope

SBV

Setback viscosity

PT

Pasting temperature

PV

Peak viscosity

BDV

Breakdown viscosity

PP

Polypeptides

HMW

High molecular weight

MMW

Medium molecular weight

LMW

Low molecular weight

AA

Amino acids

GABA

Gamma-amino butyric acid

PCA

Principal component analysis

ANOVA

Analysis of variance

Compliance with ethical standards

Conflict of interest

Authors declared no conflict of interest.

Footnotes

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