
==== Front
Food Chem X
Food Chem X
Food Chemistry: X
2590-1575
Elsevier

S2590-1575(24)00611-4
10.1016/j.fochx.2024.101723
101723
Research Article
Structural characterization and physicochemical properties of grain amaranth starch
Shen Wangyang a
Yang Jiye a
Wang Zhan a
Liu Benguo liubenguo@hist.edu.cn
b⁎
a School of Food Science and Engineering, Wuhan Polytechnic University, Wuhan 430023, China
b School of Food Science, Henan Institute of Science and Technology, Xinxiang 453003, China
⁎ Corresponding author. liubenguo@hist.edu.cn
10 8 2024
30 10 2024
10 8 2024
23 1017235 7 2024
8 8 2024
9 8 2024
© 2024 The Authors. Published by Elsevier Ltd.
2024

https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
With potato starch (PS) and corn starch (CS) as the controls, the structure and physicochemical properties of grain amaranth starch (GAS) and its binding with dihydromyricetin were investigated in this study. The results indicated that GAS granules were small in size (3.21 ± 0.13 μm) and had a low amylose content (11.57 ± 0.91%). GAS exhibited low paste clarity, solubility, and swelling power, but demonstrated good freeze-thaw stability and resistance to retrogradation. Although the pasting temperature of GAS was high (75.88 ± 0.03 °C), its peak viscosity, breakdown viscosity, and setback viscosity were significantly lower than those of PS and CS. GAS was classified as A-type starch, with a high molecular weight and broad distribution (Mw, 3.96 × 107 g/mol; PDI, 2.67). For its chain length distribution, chain B1 had the highest proportion (50.09%), while chain B3 had the lowest proportion (13.50%). The complexation of GAS with dihydromyricetin effectively enhanced its ABTS and DPPH free radical scavenging capacities.

Highlights

• Grain amaranth starch (GAS) granules were small and had a low amylose content.

• GAS exhibited good freeze-thaw stability and resistance to retrogradation.

• GAS was A-type starch with a high molecular weight and broad distribution.

• In the length distribution, chain B1 had the highest ratio, while chain B3 had the lowest.

• The complexation of GAS with dihydromyricetin could enhance its antioxidant activity.

Keywords

Grain amaranth starch
Physicochemical properties
Functional properties
Characterization
Complex
==== Body
pmc1 Introduction

Grain amaranth (Amaranthus sp), a member of the Amaranthaceae family and the Amaranthus genus, is an annual herb that serves as both a cereal and forage crop (Joshi et al., 2018). It is well-known for its high yield and superior quality as an ancient grain crop. The seeds of grain amaranth are rich in protein, containing approximately 17% and a balanced amino acid profile, surpassing that of many conventional cereal crops, thus making it a complementary addition to traditional grains (Grundy et al., 2020; Marta et al., 2023). In addition, the lipid content of its seeds is approximately 7.01%, with essential fatty acids accounting for about 83.45% (Procopet & Oroian, 2022).

Starch constitutes the predominant component of grain amaranth seeds, comprising over 60% of their composition. These seeds are also rich in dietary fiber, boasting a high digestibility and absorption rate. Additionally, grain amaranth is a plentiful source of calcium, iron, zinc, selenium, and various other trace elements. Its gluten-free nature makes it an ideal option for individuals with gluten allergies, presenting the food industry with a novel source of high-quality raw materials (Ozgur, Çimen, Denizli, & Bereli, 2023).

Grain amaranth starch (GAS) could be effectively extracted using the alkali method or the alkali/protease method (Villarreal, Ribotta, & Iturriaga, 2013). The amylose content of GAS ranged from 4.7% to 12.5% (Kong, Bao, & Corke, 2009). Kong et al. applied the enzymatic hydrolysis/HPAEC-PAD method to analyze the fine structure of amylopectin of GAS, and found that the amylopectin domain contained 2.2 clusters, with each cluster being composed of 13 chains (Kong, Corke, & Bertoft, 2009). Furthermore, GAS could be used to fabricate β-carotene microcapsules (Coelho et al., 2022). Despite the aforementioned reports on GAS, current research on the structure and physicochemical properties of GAS remains relatively limited when compared to that of starches derived from maize, potatoes, and other crops. To broaden the scope of GAS application, this study systematically investigated its appearance, structure, functional properties, and binding with dihydromyricetin. Potato starch (PS) and corn starch (CS) were used as controls. The obtained results can facilitate the application of GAS in food.

2 Materials and methods

2.1 Materials and chemicals

Grain amaranth seeds were purchased from a local market in Suqian city, Jiangsu province, China. PS and CS were the products of Hebei Zhaofa Food Co., Ltd. (Langfang, China). Dihydromyricetin was bought from Aladdin (Shanghai, China). Amylose, amylopectin, 2, 2′ -azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and 1-diphenyl-2-picrylhydrazyl (DPPH) were from Sigma-Aldrich (St. Louis, MO, USA). All other chemicals were of analytical grade.

2.2 Preparation of GAS

GAS was prepared according to a previous report (Bashir & Haripriya, 2016). An appropriate quantity of grain amaranth seeds was combined with distilled water and rapidly ground in a blender. The resulting mixture was then filtered through cheesecloth. The obtained filtrate was centrifuged at 5000 rpm for 10 min, and the precipitate was collected. The dried precipitate was treated multiple times with hexane to remove lipids by immersion, followed by natural air-drying. The defatted sample was soaked in 70% ethanol for 1 h to remove the pigment. The sample was then mixed with an alkali solution (pH 10.0) at a ratio of 1:15 (g/mL), left for 4 h, and then centrifuged at 4000 rpm. This step was repeated twice to remove the protein. The sample was washed repeatedly with water, dried, and crushed through a 100-mesh sieve, and collected as GAS. The obtained GAS was sealed in self-sealing bags for subsequent research.

2.3 Determination of starch content

The starch sample (0.2 g) was mixed with 50 mL of a 1% HCl solution. The mixture was then heated for 15 min in a boiling water bath. After cooling the sample solution to room temperature, it was sequentially mixed with 1 mL of a 30% ZnSO4 solution and 1 mL of a potassium ferricyanide solution. The resulting mixture was then filtered, and the optical rotation of the filtrate was measured using a polarimeter to determine the starch content (Coelho et al., 2022).

2.4 Measurement of amylose content

The amylose content was measured following the method of Jing, Yan, Ouyang, Xiang, and Ren (2012). In brief, 50 mg of starch sample was combined with 10 mL of 0.5 mol/L sodium hydroxide solution, and then incubated at 95 °C for 15 min before being diluted to a final volume of 50 mL. Subsequently, 2.5 mL of the resulting mixture was mixed with 20 mL of distilled water, and the pH was adjusted to 3.0. Following this, 0.5 mL of iodine reagent (0.2% I2, 2% KI) was added, and the solution was further diluted to a final volume of 50 mL. After allowing the solution to stand for 10 min, its absorbance at 620 nm was recorded using a spectrophotometer. The amylose content was then determined by comparing the absorbance to a standard curve.

2.5 Microscopic observation of starch granules

The starch sample was affixed to the sample stage using conductive double-sided adhesive, gold-coated in a vacuum, and subsequently observed for the appearance of starch granules using an FEI Quanta 200 scanning electron microscope (Hillsboro, OH, USA) at magnifications of 6000× for GAS and 1000× for CS and PS. The size distribution of the starch granules was measured using a BETTER BT-9300H laser particle size analyzer (Dandong, China).

2.6 Measurement of pasting properties

The pasting properties of a starch sample were analyzed using a Perten RVA 4500 Rapid Visco analyzer (Stockholm, Sweden) according to the RVASuper3 standard procedure. Specifically, 3.0 g of the starch sample and 25 mL of distilled water were combined in an aluminum tube. The mixture was then subjected to a series of temperature changes: it was initially held at 50 °C for 1 min, then heated to 95 °C within 3.5 min, held at 95 °C for 3 min, cooled to 50 °C within 3.5 min, and held at 50 °C for 2 min, during which the viscosity of the sample was automatically recorded (Wang & Copeland, 2012).

2.7 Evaluation of functional properties

The paste clarity, freeze-thaw stability, syneresis, solubility, swelling power and gel strength of starch sample were measured.

For paste clarity test, the starch suspension (1%, w/v) was subjected to boiling in a water bath for 15 min, followed by cooling to room temperature. The transmittance (T%) of the suspension was then measured at 640 nm using a spectrophotometer (Correia, Cruz-Lopes, & Beirão-da-Costa, 2012).

For freeze-thaw stability assay, the starch suspension (6%, w/v) was subjected to a boiling water bath for 15 min and subsequently cooled to room temperature. The resulting starch paste, weighing 30 g, was then stored in a − 18 °C refrigerator for 24 h, followed by thawing at room temperature for 2 h. Afterward, it was centrifuged at 4000 rpm for 15 min, and the percentage of the separated water weight to the paste weight was recorded as the freeze-thaw stability (Luo, He, Fu, Luo, & Gao, 2006).

The syneresis test was carried out according to a previous report (Lv, Zhang, Zhen, Shi, & Liu, 2022). A 2% (w/v) starch suspension was heated in a boiling water bath for 20 min and subsequently cooled to room temperature. The resulting 30 g starch paste was refrigerated at 4 °C for 24 h and then centrifuged at 4000 rpm for 15 min. The syneresis value, calculated as the percentage of the weight of separated water to the weight of the paste, was inversely proportional to the anti-retrogradation ability of the sample.

The solubility and swelling power of the sample was evaluated based on a previous report (Lv et al., 2022). A 6% starch solution was subjected to heating in water baths at temperatures of 55, 65, 75, 85, and 95 °C for a duration of 30 min. Subsequently, the solution was cooled to room temperature and then centrifuged at 4000 rpm for 15 min. The mass of dissolved starch (W1) was determined after evaporating the supernatant, and the mass of swelling starch in the centrifuge tube (W2) was also recorded. The solubility (S1) and swelling power (S2) of the starch were then calculated using the following formula:(1) S1=W1W0×100%

(2) S2=W2W01−S1×100%

where W0 is the mass of the starch used.

The gel strength of the sample was also determined (Lv et al., 2022). A 10% (w/v) starch suspension was heated in a boiling water bath for 30 min, then cooled to room temperature and refrigerated at 4 °C for 16 h to form a stable starch gel. The gel strength was measured at 25 °C using a TA-XT plus texture analyzer with a P/0.5 probe (Stable Micro Systems, UK). The measurement parameters included a trigger force of 2.0 g, a probe speed of 1.0 mm/s, and a compression depth of 10 mm.

2.8 Determination of X-ray diffractometry pattern

The sample was subjected to XRD analysis using an Empyrean X-ray diffractometer (Malvern Panalytical, Worcestershire, UK). The 2θ scanning range was set at 5–40° with a step size of 0.04°. Subsequently, the obtained data was processed utilizing JADE6 software (MDI, Livermore, CA, USA) to determine the crystallinity.

2.9 Determination of molecular weight

The 5 mg starch sample was dissolved in 5 mL of DMSO and heated to 80 °C for 3 h until complete dissolution. Subsequently, a GPC-RI-MALS system (Wyatt, Santa Barbara, CA, USA) was utilized to determine the molecular weight of the sample (Wang et al., 2023; Wang et al., 2023). The sample solution (200 μL) was injected and separated using three series of GPC columns (Ohpak SB-805 HQ, Ohpak SB-804 HQ, Ohpak SB-803 HQ) at 60 °C with dimethyl sulfoxide containing 0.5% lithium bromide as the mobile phase. The flow rate was set at 0.3 mL/min.

2.10 Determination of starch chain length

The 10 mg starch sample was mixed with 5 mL of distilled water and heated in a boiling water bath for 60 min. Subsequently, 50 μL of sodium acetate (0.6 M, pH 4.4), 10 μL of NaN3 (2% w/v), and 10 μL of amylase (1400 U) were added to the mixture, which was then incubated at 37 °C for 24 h. Following this, a 0.5% (w/v) sodium borohydride solution was added, and the mixture was further kept for 20 h. The 600 μL mixture was placed in a centrifuge tube and dried with nitrogen at room temperature. The residue was dissolved in 30 μL of 1 M NaOH, and allowed to stand for 60 min. Then, 570 μL of water was added for dilution, followed by centrifugation at 12000 rpm for 5 min. The supernatant was taken for analysis. The starch chain length determination was conducted using an ICS5000+ ion chromatograph with a Dionex™ CarboPac™ PA200 column (Thermo Fisher Scientific, Waltham, MA, USA). The injection volume was 5 μL, and the mobile phase consisted of 0.2 M sodium hydroxide (A) and 0.2 M sodium hydroxide/0.2 M sodium acetate (B). The gradient elution program followed our previous report (Guo, Geng, Shi, Yuan, & Liu, 2024).

2.11 Preparation of starch/dihydromyricetin complex

The starch/dihydromyricetin complex was prepared based on a previous report (Jiang et al., 2023). Specifically, 100 mL starch suspension (10%, w/v) was heated for 30 min in a boiling water bath to gelatinize the starch. The gelatinized starch solution was then combined with 1 g of dihydromyricetin, homogenized for 1 min at 8000 rpm, and incubated at 90 °C for 20 min. Subsequently, the mixture was centrifuged, and the resulting residue was washed with anhydrous ethanol, centrifuged again, and finally vacuum freeze-dried to yield the starch/dihydromyricetin complex.

2.12 Measurement of dihydromyricetin content in complex

The complex (0.3 g) was combined with 10 mL of anhydrous ethanol. It was then subjected to 800 W of ultrasound for 30 min and subsequently centrifuged at 5000 rpm for 10 min. This process was repeated twice. The resulting supernatant was collected and adjusted to a final volume of 50 mL. Its absorbance at 292 nm was determined after proper dilution, and the dihydromyricetin content in the complex was determined based on the standard curve of dihydromyricetin.

2.13 Antioxidant assay

The ABTS and DPPH free radical scavenging activities of the complex and starch were determined following the method outlined by (Serpen, Capuano, Fogliano, and Gökmen (2007)). For the ABTS test, a 2 mg sample was transferred into a centrifuge tube and mixed with 4 mL of ABTS test solution. The mixture was then swirled for 2 min to facilitate the reaction. After centrifugation, the absorbance value (Asample) of the supernatant at 734 nm was measured, and the absorbance value (Acontrol) of the ABTS test solution at 734 nm was also determined. The ABTS free radical scavenging activity of the sample (AA) was calculated using Formula 3.

For the DPPH assay, 2 mg of the sample was transferred in a centrifuge tube and mixed with 4 mL of a 0.2 mmol/L DPPH test solution. The mixture was then allowed to sit for 30 min, with periodic vortexing to enhance the contact between the sample and DPPH. After centrifugation, the absorbance value of the supernatant was measured at 517 nm (Asample), and the absorbance value of the DPPH test solution (Acontrol) was recorded. The DPPH free radical scavenging activity of the sample (AA) could be determined using Formula 3.(3) AA=Acontrol−AsampleAcontrol×100%

2.14 Statistical analysis

The experimental results were presented as mean ± standard deviation (n = 3). Data analysis was performed using SPSS 18.0 software (SPSS Inc., Chicago, Illinois, USA), and one-way ANOVA was used with Duncan's multiple range test. A significance level of p < 0.05 was utilized to determine statistical significance.

3 Results and discussion

3.1 Appearance and size of starch

Cereal types and growth conditions have a significant impact on the morphology and size of starch granules. As shown in Fig. 1, scanning electron microscopy (SEM) observations were conducted at a magnification of 6000 times for GAS, while PS and CS were observed at a magnification of 1000 times. The microscopic analysis revealed that GAS possessed irregular spherical shapes with smooth surfaces and a high degree of aggregation, consistent with the particle size analysis presented in Table S1 (median diameter, 3.21 ± 0.13 μm). Most CS granules were polygonal, while PS granules were elliptical, with median diameters of 13.85 ± 0.05 μm and 15.46 ± 0.28 μm, respectively, both higher than that of GAS, which coincided with the report of Kong, Corke, and Bertoft (2009). Starch with smaller particle size is often used to produce fat substitutes, thereby improving the texture of food.Fig. 1 Scanning electron microscope images of grain amaranth starch (a), corn starch (b), and potato starch (c) (grain amaranth starch, corn starch and potato starch are observed at 6000×, 1000× and 1000×, respectively).

Fig. 1

3.2 Amylose content

Grain amaranth typically produces over 100,000 seeds per plant, with each seed being very small and weighing only 0.5–1.2 g per 1000 grains. Consequently, the hull of the seeds is challenging to remove during processing, leading to a lower starch content. The starch content of GAS obtained in this experiment was 83.92 ± 0.92%, as indicated in Table S1, which was significantly lower than that of CS (88.42 ± 0.30%) and PS (86.25 ± 0.13%). Additionally, the amylose content of GAS was 11.57%, also lower than that of CS (22.98%) and PS (21.20%), consistent with the findings of (Zhu (2017). It has been previously documented that the amylose content of GAS is generally lower than that of other grains, with only a few grain amaranth seeds exhibiting higher amylose content than grain starch (Hoover, Sinnott, & Perera, 1998). The amylose content may be influenced by factors such as the plant area, the method of amylose determination, and the growing environment.

3.3 Pasting properties

When heated in water, starch particles absorb water and swell, causing the breaking of intermolecular and intramolecular hydrogen bonds. This leads to a change in the ordered crystal structure of starch molecules into a disordered crystallization state, resulting in the formation of starch gelatinization. Table 1 presents the pasting properties of GAS, CS, and PS. The pasting temperature of GAS was slightly lower than that of CS and significantly higher than that of PS. Additionally, the peak viscosity, breakdown viscosity, setback viscosity, trough viscosity and cold viscosity of GAS were inferior to those of CS and PS. The peak viscosity of starch reflects the maximum viscosity achieved upon heating after its interaction with water, and is closely related to the granule size and distribution of both amylose and amylopectin. Low breakdown viscosity and low setback viscosity indicate that GAS exhibits good heat resistance, shear resistance, and thermal stability, with excellent stability in cold paste. These findings align with the research results of Xia et al. (2015).Table 1 Pasting properties of grain amaranth starch (GAS), corn starch (CS), and potato starch (PS).

Table 1	Peak viscosity
(cp)	Trough viscosity
(cp)	Breakdown viscosity
(cp)	Cold viscosity
(cp)	Setback viscosity
(cp)	Pasting temperature
(°C)	
GAS	2041 ± 130.14c	1195 ± 67.09c	846 ± 69.95c	1334 ± 76.17c	138.7 ± 14.50c	75.88 ± 0.03b	
CS	3067 ± 36.11b	2076 ± 41.94b	991 ± 6.03b	3347 ± 37.23b	1271.3 ± 22.12a	76.80 ± 0.62a	
PS	5133 ± 149.12a	2644 ± 56.75a	2488 ± 96.41a	3655 ± 158.71a	1011 ± 103.20b	71.87 ± 0.06c	
Different lowercase superscript letters in the same column indicate significant differences (p < 0.05).

3.4 Functional properties

The clarity of starch paste is affected by factors such as amylose content, molecular weight, and molecular structure (Lv et al., 2022). As shown in Table 2, the paste clarity of GAS was lower than that of CS and PS, primarily due to the small particle size and agglomeration of GAS. Freezing and thawing of starch gels leads to starch chain aggregation, resulting in dehydration shrinkage, which can be quantified by the syneresis rate. A higher syneresis rate indicates lower freeze-thaw stability. As shown in Table 2, the freeze-thaw stability of GAS was significantly superior to that of CS and PS, indicating that GAS can be used in the manufacture of frozen food. When gelatinized starch is cooled to room temperature or below, retrogradation occurs, causing the starch paste to become opaque, and in some cases, coagulate and precipitate. The rate of retrogradation is initially fast and gradually decreases over time. In Table 2, the syneresis value of GAS was inferior to that of CS and PS, mainly attributed to its low amylose content, confirming its excellent retrogradation resistance. The retrogradation resistance of PS was higher than that of CS, primarily due to the higher phosphate ester content in PS, which delayed retrogradation.Table 2 Paste clarity, freeze-thaw stability, syneresis, and gel strength values of grain amaranth starch (GAS), corn starch (CS), and potato starch (PS).

Table 2	Clarity
(%)	Freeze-thaw stability
(%)	Syneresis
(%)	Gel Strength
(g)	
GAS	2.50 ± 0.34c	11.25 ± 0.36c	16.43 ± 1.02c	12.76 ± 2.19c	
CS	5.13 ± 0.54b	15.11 ± 1.16b	44.75 ± 1.89a	57.36 ± 10.20b	
PS	15.57 ± 1.09a	26.17 ± 4.83a	26.75 ± 1.82b	66.03 ± 2.67a	
Different lowercase superscript letters in the same column indicate significant differences (p < 0.05).

In this investigation, the strength of starch gel was assessed at a 10% concentration (Table 2). The gel derived from GAS exhibited lower strength compared to those from CS and PS. It was attributed to the inferior amylose content of GAS, as well as its difficulty in retrogradation, resulting in a loose internal structure and lower gel strength. These findings were consistent with the report of Wang, Wu, et al. (2023) and Wang, Zhang, et al. (2023). When starch granules are heated in water, the molecular hydrogen bonds are broken, leading to the destruction of the crystal structure of starch and subsequent dissolution and swelling of the granules. As depicted in Fig. 2, the swelling power and solubility of GAS were found to be higher than those of CS and PS within the temperature range of 55 °C–65 °C. This was attributed to the smaller particle size of GAS, which made it easier to dissolve and swell. However, with the increasing temperature, the swelling power and solubility of GAS gradually decreased compared to those of CS and PS, indicating that GAS has good stability at high temperature and can be used to keep the texture and taste of cooked food.Fig. 2 Solubility and swelling power results of grain amaranth starch (GAS), corn starch (CS), and potato starch (PS).

Fig. 2

3.5 XRD pattern

X-ray diffraction is commonly used for analyzing the structure of starch, with the positions of specific diffraction peaks used to identify different crystal forms. Starch can be categorized into types A, B, and C based on its XRD patterns, with some cases also showing V-type crystal structures. As shown in Fig. S1, GAS displayed distinct diffraction peaks at 15.0°, 16.9°, 18.0°, and 23.0°, similar to CS, indicating its classification as A-type starch. PS, on the other hand, exhibited different intensity peaks at 5.6°, 15.1°, 17.07°, and 23.1°, confirming its classification as B-type starch. The calculation of the ratio of crystal peak area to the total diffraction area revealed that the crystallinity of GAS was 21.02%, which was lower than that of CS (25.26%) and PS (22.44%). This finding, consistent with the report of (Sindhu and Khatkar (2018), suggests a high degree of crystallinity within the amylopectin component of GAS.

3.6 Molecular weight

Molecular weight is an essential physicochemical parameter of starch molecular structure, significantly influencing its properties and applications (Kowittaya & Lumdubwong, 2014; Sikora et al., 2015). The weight-average molecular weight (Mw) of GAS was 3.96 × 107 g/mol, higher than that of CS at 3.34 × 107 g/mol, and lower than that of PS at 8.50 × 107 g/mol. Nowak et al. also reported a weight-average molecular weight of 4.51 × 107 g/mol for GAS (Nowak, Khachatryan, & Wisła-Świder, 2021), slightly higher than the results of this study, possibly due to differences in dissolution conditions and varieties. The polydispersity index (PDI) of GAS (2.67) was higher than that of CS (2.03) and PS (1.18), indicating that the particle size of GAS was more complex and its molecular weight distribution was wider. The Z-average radius (Rz) of gyration of the polymer, which indicates the probability of finding the polymer at a given distance from the center, is often used to characterize the molecular size of the linear polymer. The Rz of GAS (111.15 nm) was larger than that of CS (74.17 nm) and PS (107.077 nm), further illustrating the complexity of molecular distribution of GAS.

3.7 Starch chain length

The distribution of starch chain lengths is an important structural characteristic of starch (Li, Wen, Wang, & Sun, 2018), and it varies among different types of starch (Li & Liu, 2019). According to starch structure, starch chain lengths can be categorized into chain A (fa, 6 < DP ≤ 12), chain B1 (fb1, 13 < DP ≤ 24), chain B2 (fb2, 25 < DP ≤ 36), and chain B3 (fb3, DP > 37) based on different degrees of polymerization (DPs). Fig. 3 presents the chain length (CL) distribution of GAS, CS, and PS. For GAS, the first major peak was observed around DP12, indicating the presence of short chains including chain A and chain B1, while a second smaller peak appeared around DP43, representing medium and long chains, with chain B1 accounting for the largest proportion (50.09%) and chain B3 accounting for the smallest (13.5%), consistent with the findings of Srichuwong et al. (2017). Both CS and PS exhibited dual peak distributions in chain length, similar to GAS, with the primary peak occurring around DP12 for both. A secondary peak was observed at DP45 for CS and at DP43 for PS. Notably, chain B1 was predominant in both cases, accounting for 48.81% and 46.06% of the total for CS and PS, respectively, while chain B2 was the least prevalent, comprising 14.14% and 10.90%, respectively.Fig. 3 Starch chain length distribution profiles of grain amaranth starch (GAS), corn starch (CS), and potato starch (PS) (fa, fb1, fb2 and fb3 represent chain A, chain B1, chain B2 and chain B3, respectively).

Fig. 3

3.8 Starch/dihydromyricetin complex

Starch with small particle size has potential applications in fat replacement, active substance delivery, and other fields due to its small and uniform particle size, and low allergenicity (Marta et al., 2023). Dihydromyricetin (DMY) is a flavonoid with various biological activities that can bind with proteins and starch. In this study, CS and PS were used as controls to investigate the binding effects of GAS and DMY. The results indicated that the binding capacity of GAS with DMY was 50.95 ± 0.41 mg/g, significantly lower than that of CS (58.23 ± 0.68 mg/g) and PS (71.26 ± 2.25 mg/g). This difference may be attributed to the low amylose content of GAS (Liu et al., 2017). The antioxidant activity of food can prolong the shelf life of food and also resist discoloration and loss of nutrients. Currently, most antioxidant assays are limited to soluble substances. However, Liu et al. found that specific chemical groups can also play an antioxidant role after combining with insoluble substances and developed a method for the determination of insoluble substances (Liu et al., 2018). In this study, the antioxidant activities of the GAS-DMY complex, CS-DMY complex, and PS-DMY complex were evaluated using this method. As shown in Fig. 4, the GAS-DMY complex exhibited significantly higher ABTS and DPPH free radical scavenging abilities compared to the CS-DMY complex and PS-DMY complex. However, GAS, CS, and PS all showed relatively low scavenging capacity. It can be concluded that the complexation of GAS with DMY enhanced its antioxidant ability. This enhancement may be attributed to the smaller particle size of GAS, resulting in a larger contact area with the ABTS and DPPH solutions during testing, leading to higher antioxidant performance (Jiang et al., 2020).Fig. 4 ABTS and DPPH radical scavenging activities of grain amaranth starch (GAS), corn starch (CS), potato starch (PS), grain amaranth starch/dihydromyricetin complex (GAS-DMY), corn starch/dihydromyricetin complex (CS-DMY), and potato starch/dihydromyricetin complex (PS-DMY).

Fig. 4

4 Conclusions

GAS was characterized by small granule size and low amylose content. While GAS exhibited lower paste clarity, solubility, and swelling power compared to CS and PS, it demonstrated superior anti-retrogradation ability and freeze-thaw stability in comparison to the latter. GAS displayed a high pasting temperature, but its peak viscosity, breakdown viscosity, and setback viscosity were significantly lower than those of CS and PS. Furthermore, GAS was identified as an A-type starch, with a large molecular weight and wide distribution. In terms of starch chain length distribution, chain B1 had the highest proportion, while chain B3 had the lowest proportion. Additionally, the complexation of GAS with DMY effectively enhanced its ABTS and DPPH free radical scavenging capacity. These findings can provide references for the application of GAS in starch foods and functional foods.

CRediT authorship contribution statement

Wangyang Shen: Writing – review & editing, Writing – original draft, Validation, Methodology, Investigation, Formal analysis, Data curation, Resources. Jiye Yang: Writing – review & editing, Writing – original draft, Validation, Methodology, Investigation, Formal analysis, Data curation. Zhan Wang: Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis. Benguo Liu: Writing – review & editing, Writing – original draft, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization.

Declaration of competing interest

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.

Appendix A Supplementary data

Supplementary material

Image 1

Data availability

Data will be made available on request.

Acknowledgements

This work was supported by the 10.13039/501100001809 National Natural Science Foundation of China (No. 32072180 ).

Appendix A Supplementary data to this article can be found online at https://doi.org/10.1016/j.fochx.2024.101723.
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