Skip to main content
NCBI home page
Food Science & Nutrition logoLink to Food Science & Nutrition
. 2024 Sep 17;12(11):9007–9024. doi: 10.1002/fsn3.4409

Effects of different thermal processing methods on amino acid, fatty acid, and volatile flavor substance contents of Aohan millet (Golden seedling millet)

Likun Cheng 1, Shuang Qu 1, Yueying Yun 1, Yan Ren 1, Fucheng Guo 1, Yakun Zhang 1,✉, Guoze Wang 1,✉
PMCID: PMC11606813  PMID: 39620021

Abstract

Aohan millet has been cultivated for 8000 years and has rich nutritional value, such as high‐quality fatty acids and amino acids. Thermal processing is a conventional approach to food preparation. However, the effect of thermal processing on the formation of flavor substances in millet has not been clarified. Therefore, in this study, the effects of three different thermal processing techniques, namely, steaming, stir‐frying, and puffing, on the amino acids, fatty acids, and volatile flavor substances of Aohan millet were investigated using high‐speed automatic amino acid analyzer, headspace solid‐phase microextraction method, combined with gas chromatography–mass spectrometry (HS‐SPME/GC–MS) and gas chromatography (GC) with Aohan millet from Inner Mongolia as the raw material. All three thermal processing methods notably reduced the levels of protein, starch, polyphenols, and flavonoids in Aohan millet when compared to the raw millet (p < .05). Amino acid and fatty acid contents demonstrated an increase in fried and puffed millet relative to steamed millet, with notable distinctions in amino acid and fatty acid contents between these two groups. Following the steaming process, there was a significant increase in the flavor compounds of Aohan millet, rising from 53 to 80, while this increase was not observed in the other two groups. The correlation analysis suggested that the formation of flavor compounds was predominantly influenced by the types and levels of amino acids. The study suggested that different heat treatments affected the amino acid, fatty acid, and more significantly flavor material content and composition of Aohan millet. In conclusion, steaming treatment could retain more nutrients and richer flavor substances; while puffing treatment would enhance amino acid and fatty acid content, which provides a fundamental basis for scientifically guided processing and rational culinary application of Aohan millet.

Keywords: amino acids, Aohan millet, fatty acids, thermal processing method, volatile flavor compounds

Puffed millet shows reduced fat and starch levels, rendering it a suitable choice for individuals seeking weight loss. Fried and puffed millet exhibited increased amino acid and fatty acid content compared to steamed millet. The correlation analysis suggested that the formation of flavor compounds was predominantly influenced by the types and levels of amino acids.

graphic file with name FSN3-12-9007-g005.jpg

1. INTRODUCTION

Aohan Millet, cultivated in Aohan Banner, Chifeng City, Inner Mongolia Autonomous Region, is renowned as the “birthplace of world Xiaomi”. Historical records indicate that millet has been cultivated in this region for over 8000 years, making it one of the earliest areas for millet cultivation and consumption globally (Jia et al., 2016) The region offers ample sunshine, significant day–night temperature fluctuations, moderate precipitation, and topographic features such as hills, slopes, and sandy soil, which collectively provide a unique environment conducive to grain growth (Wang, Wang, et al., 2021). Aohan millet is grown organically, utilizing organic fertilizers sourced from cattle, sheep, and other livestock, alongside environmentally friendly pest control methods. Furthermore, the soil in Aohan Banner is rich in well‐balanced minerals like iron and phosphorus, contributing to the inherent high‐quality attributes of Aohan millet (Feng, 2020). The Aohan Dryland Farming System has earned recognition as a ‘Globally Important Heritage Systems’ site by the Food and Agriculture Organization (FAO) (Min & Zhang, 2019). In the local Chinese market, Aohan millet has seen a surge in sales as a premium product and is known for its beneficial effects on blood sugar and lipid levels, establishing its reputation as a cereal with both medicinal and dietary values (Jones, 2017; Sabuz et al., 2023; Vedamanickam et al., 2020).

Thermal processing is a conventional approach to food preparation. This process involves heating food, leading to the denaturation of proteins, gelatinization of starch, and the disruption of cellular tissue structure. These changes result in the release of cellular contents, rendering the food more easily digestible and enhancing its nutritional value (Zhan et al., 2018). Thermal processing also offers various advantages, including pathogen inactivation, reduction of natural toxins, extension of shelf life, improved palatability, taste, texture, and flavor, as well as enhanced functional characteristics (van Boekel et al., 2010). Common thermal processing techniques for cereals include steaming, boiling, stir‐frying, roasting, and puffing. These methods can alter the color, texture, and flavor of food, making it more appealing. Moreover, thermal processing can modify the nutritional composition of food, including fat content, vitamins, and minerals (Jongyingcharoen & Ahmad, 2014). Different thermal processing methods exert varying effects on the nutritional properties and functional composition of food. For instance, cooking can dissolve water‐soluble substances, such as soluble sugars (Yang et al., 2019), water‐soluble vitamins (Bureau et al., 2015), and trace elements (Koplík et al., 2004), in food, leading to a significant reduction in their content. Conversely, steaming does not bring the grains into direct contact with water, resulting in fewer effects on the water‐soluble components of the food. Research by Pradeep indicates that both atmospheric pressure steaming and high‐pressure steaming can enhance the content of total phenols, total flavonoids, tannins, and ferulic acid in millet, with high‐pressure steaming having a more pronounced effect (Pradeep & Guha, 2011). The preparation of expanded grains relies on high‐temperature, short‐time treatment (HTST), which causes the endosperm to expand due to the generation of steam within it (Dharmaraj et al., 2012). Huang observed that expansion treatment significantly enhances antioxidant capacity and minimizes the loss of proteins, amino acids, and other components compared to alternative thermal processing methods (Huang et al., 2023). Shabir compared nutrient composition and antioxidant differences in brown rice under three treatments (raw, boiled, and expanded), demonstrating that expansion treatment improves the nutritional value of brown rice, while boiled treatment increases mineral content (Mir et al., 2016).

Currently, both domestic and international research on millet processing primarily focus on methods, such as steaming and boiling, with limited exploration of frying, puffing, and other methods. This limitation was due to the challenge of processing millet, characterized by its small particle size compared to other cereals. However, as living standards improve, the processing of millet has become more and more diversified, and it was important to understand the effect of thermal processing methods on the nutritional properties of food and the formation of flavor. In addition, flavor substance research was focused on determining the relationship between key volatile compounds and their sensory properties. The flavor of millet was developed mainly during various processing treatments, especially heat treatment processing, as well as precursor flavor substances and enzymes from natural millet that contribute to flavor formation. The flavor of processed millet was a complex combination of volatile aromas associated with heat. These were the innovative points of the present study and underscoring the significance of understanding the impact of thermal processing methods on the nutritional properties of food. Consequently, this study employs steaming, frying, and puffing as three thermal processing methods for Aohan millet. The research investigates the impact of these methods on nutrient content, functional composition, and related factors, offering theoretical guidance for the scientific processing and rational culinary utilization of Aohan millet, thereby enhancing its application potential.

2. MATERIALS AND METHODS

2.1. Chemicals and materials

Aohan Millet was commercially sourced. α‐Amylase, protease, and amyloglucosidase were procured from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Folin Reagent was obtained from Solarbio Science and Technology Co., Ltd (Beijing, China). Gallic acid was acquired from Kramar Reagent Co., Ltd (Shanghai, China). Rutin served as the standard. A set of 37 fatty acid mixture standards was purchased from the Sigma Company. All other reagents used were of analytical purity.

2.2. Instruments and equipment

The following equipment and instruments were employed: K9840 automatic Kjeldahl nitrogen analyzer (Haineng Future Technology Group Co., Ltd), SXT‐06 Soxhlet extractor (Shanghai Hongji Instrument Equipment Co., Ltd), L‐8900 amino acid analyzer, 6890 N‐G5795B Gas Chromatograph Mass Spectrometer (Agilent), Ultraviolet spectrophotometer, XLR high‐speed refrigerated centrifuge (Thermo Fisher Technology (China) Co., Ltd).

2.3. Methods

2.3.1. Heat processing of Aohan millet

Millet grains with no presence of moths, debris, mildew, and exhibiting full freshness were selected as raw materials. These grains underwent thorough cleaning, involving washing 2 to 3 times, before further processing. The processing of Aohan millet included three methods:

  1. Steamed Aohan millet, S‐AM: The prepared Aohan millet was steamed under boiling water (95°C) for approximately 30 min, adhering to a millet‐to‐water ratio of 1:1 (mass ratio) (Bai et al., 2022).

  2. Fried Aohan millet, F‐AM: Processed Aohan millet was dried at 37°C and then fried in a hot pan (300 W) for 30 min without the addition of oil (Bi et al., 2021).

  3. Expanded Aohan millet, E‐AM: Processed Aohan millet was dried at 37°C and subjected to puffing using a popcorn machine.

After the heating process, the millet was allowed to cool to room temperature, following which it was ground using a grinder and sifted through a 200‐mesh sieve. The millet flour was then individually packed in sealed bags and stored at −40°C for future use.

2.3.2. Nutrient determination

Determination of polyphenol content

The polyphenol content of the extract was assessed using the Folin–Ciocalteu method, as described by Adom et al. (2003). In brief, 5 mL of sample extract (1 mg/mL) was combined with 1 mL of Folin–Ciocalteu reagent after 5 min of incubation. This mixture was followed by the addition of 2 mL of 20% sodium carbonate (Na2CO3), and the final volume was adjusted to 10 mL with distilled water. The resulting mixture stood in darkness for an additional 60 min, after which absorbance was measured at 765 nm. The polyphenol content was determined from a calibration curve and expressed as milligrams of gallic acid equivalent per gram (mg GAE/g) of dry weight. The linear regression equation was y = 10.597x + 0.0266, with R 2 = 0.9992.

Determination of flavonoid content

The flavonoid content of the sample extract was assessed via the aluminum chloride (AlCl3) colorimetric method, based on Adom's protocol (Adom et al., 2003), with slight adjustments. Specifically, 5 mL of the crude extract was mixed with 0.7 mL of 5% sodium nitrite (NaNO2) solution. After 5 min of incubation, 0.7 mL of 10% AlCl3 solution was added, followed by 5 mL of 1 mol/L sodium hydroxide (NaOH) solution. The final volume of the mixture was adjusted to 25 mL with 60% ethanol. After 15 min of standing, absorbance was measured at 510 nm. The total flavonoid content was calculated from a calibration curve and expressed as milligrams of rutin equivalent per gram (mg RE/g) of dry weight. The linear regression equation was y = 9.0825x + 0.017, with R 2 = 0.999.

2.3.3. Determination of amino acid content

Amino acid contents were determined following Huang's method (Huang et al., 2019) with minor modifications. Approximately 300 mg of Aohan millet powder was weighed and placed in a digestion tube. Subsequently, 10 mL of 6 mol/L hydrochloric acid (HCl) solution was added, followed by 2 min of ultrasonication. The tube was sealed under a nitrogen atmosphere. After cooling, the digestion tube was shaken at room temperature, and its cap was opened. The solution was then diluted with ultrapure water in a 100 mL volumetric flask and thoroughly mixed. It was filtered through a 0.45‐μm inorganic filter membrane, and 2.5 mL of this filtrate was transferred into a 25 mL volumetric flask and further diluted with ultrapure water. This solution was again filtered using a 0.45‐μm inorganic filter membrane. The resulting filtrate was used for detection and analysis on a LA8080 high‐speed automatic amino acid analyzer.

2.3.4. Determination of fatty acid content

Fatty acid content determination was performed according to Honicky's method (Honicky et al., 2020), with minor modifications. After extracting the fat from the sample, fat saponification and fatty acid methylation were carried out. In the fat extract, 2 mL of 2% sodium hydroxide in methanol solution was added and subjected to a water bath at 85°C for 30 min. Subsequently, 3 mL of 14% boron trifluoride (BF3) in methanol solution was added to the water bath at 85°C for an additional 30 min. Following the water bath, and once the temperature had cooled to room temperature, 1 mL of n‐hexane was introduced into the centrifuge tube. After shaking for 2 min, the mixture was left undisturbed for an hour to facilitate stratification. A volume of 100 μL of the supernatant was taken and adjusted with n‐hexane to a final volume of 1 mL. This solution was then filtered through a 0.45‐μm filter membrane and analyzed using the appropriate machine. The gas chromatography conditions included a TG‐FAME column measuring 50 m × 0.25 mm × 0.20 μm, with a heating procedure that was initiated at 80°C for 1 min, followed by a heating rate of 20°C/min to 160°C, where it was held for 1.5 min, and ultimately a heating rate of 3°C/min to 250°C, which was maintained for 3 min. The inlet temperature was set at 270°C, utilizing nitrogen as the carrier gas with a flow rate of 0.63 mL/min. The injection was shunt‐based with a 100:1 shunt ratio, and a hydrogen flame ionization detector (FID) was employed with a detector temperature of 270°C.

2.3.5. Determination of volatile flavor compounds

Volatile flavor compounds were determined following methods described by Yaqub and Gay (Gay et al., 2020; Yaqub et al., 2020). Initially, saturated sodium chloride (NaCl) was added to a 20 mL headspace bottle and heated at 80°C for 30 min. After this period, a headspace microextraction injection needle was inserted into the headspace bottle, and the heating continued for another 30 min. Subsequently, the analysis was conducted with an inlet temperature of 250°C for 5 min. The chromatographic conditions were configured as follows: the column used was HP‐5MS, with dimensions of 30 m × 0.25 mm × 0.25 μm. The column temperature was initiated at 50°C for 2 min, then increased at a rate of 5°C/min to 180°C for 5 min, and finally, it was elevated at a rate of 10°C/min to 250°C for another 5 min. The inlet temperature was maintained at 250°C, and the transmission line temperature was 280°C. The carrier gas flow rate was 1.0 mL/min, and no shunt was utilized. For mass spectrometry, the ion source temperature was set to 230°C, the quaternary rod temperature to 150°C, and the mass spectrum operated in the electron ionization (EI) source mode with a full sweep range of 40–600.

2.3.6. Statistics analysis

Data analysis was conducted using SPSS software (SPSS PASW 18.0). Duncan's multiple range test was used to separate means (p < .05). All presented data were given as the mean with the standard deviation. All tests were conducted in triplicate. Principal component analysis (PCA) was executed using Origin 2018 statistical software (Origin Lab, Northampton, MA, USA). Correlation analyses were performed using Spearman's rank correlation coefficient, which was a nonparametric statistical method suitable for non‐normally distributed data.

3. RESULTS AND DISCUSSION

3.1. Nutritional analysis of Aohan millet

Table 1 provides an overview of the basic nutrient composition of Aohan millet after undergoing three distinct thermal processing methods. Notably, all three processing methods led to a significant reduction (p < .05) in the protein content of Aohan millet when compared to the raw AM. However, there was no significant difference in protein content between steamed S‐AM and F‐AM (p > .05). Conversely, after steaming, the fat content of Aohan millet experienced a notable increase (p < .05), which can be attributed to the rupture of cell walls during heating, facilitating fat dissolution and augmenting its content. In contrast, both frying and puffing treatments resulted in a substantial reduction in fat content (p < .05). This reduction may be due to the breakdown and structural degradation of fat during frying and puffing, causing the release of fat. Furthermore, starch content displayed a significant variation (p < .05) among these three processing methods, with reductions of 18.32%, 10.18%, and 59.82% in S‐AM, F‐AM, and E‐AM, respectively, when compared to AM. There was aqueous leaching of amylose or degradation of the starch granules leading to consequent reduction in starch content, with the highest starch loss observed in the expansion treatment, given its pressurized nature (Saha & Roy, 2020).

TABLE 1.

Effects of different thermal processing methods on basic nutrients of Aohan millet.

Processing method Protein content (g/100 g) Fat content (g/100 g) Starch content (g/100 g)
AM 11.56 ± 0.30a 3.16 ± 0.06b 65.61 ± 0.73a
S‐AM 7.48 ± 0.30b 5.45 ± 0.39a 53.59 ± 0.45c
F‐AM 7.45 ± 0.25b 0.21 ± 0.08d 58.93 ± 0.64b
E‐AM 4.39 ± 0.30c 1.64 ± 0.32c 26.36 ± 1.73d
Open in a new tab

Note: Mean ± SD (n = 3). Means with different superscripts (a, b) in the same row are significantly different (p < .05).

Abbreviations: AM, Raw Aohan millet; E‐AM, Expanded Aohan millet; F‐AM, Fried Aohan millet; S‐AM, Steamed Aohan millet.

3.2. Analysis of the content of functional components of Aohan millet

Functional components, such as polyphenols and flavonoids, are known for their anti‐inflammatory and antiaging properties (Bai et al., 2021; Wang, Cao, et al., 2021). Table 2 illustrates the impact of three thermal processing methods on the content of functional components in Aohan millet. It was evident that thermal processing led to a significant reduction (p < .05) in both polyphenol and flavonoid contents of Aohan millet. The polyphenol content of F‐AM exhibited the least decrease, while the flavonoid content of expanded E‐AM experienced the least reduction. Conversely, S‐AM demonstrated the most substantial decrease in both polyphenols and flavonoids, with a reduction of 56.64% and 45.06%, respectively. This finding aligns with the results of a study by Wu, which revealed that four heating methods (boiling, roasting, extruding, and pressure cooking) led to decreased polyphenol, flavonoid, and saponin content in quinoa, consistent with the outcomes of this experiment (Wu et al., 2021). In a study by Das, it was determined that the optimal extraction conditions for polyphenols in tea were 80°C for 20 min, with polyphenol content decreasing as temperature and time increased. The results indicate that all three heat processing methods (steaming, frying, and puffing) resulted in polyphenol loss in millet due to the higher temperatures involved (Das & Eun, 2018). Shigihalli also checked the popping effect on the nutritional and antinutritional profiles of finger millet. The result showed a decrease in fat content and the antinutrients’ content like trypsin inhibitor activity, tannins, and phytic acid (Shigihalli et al., 2018). Notably, the highest polyphenol content was observed in E‐AM due to the rapid preparation of puffed millet, involving a shorter duration of heat exposure and creating a porous structure that aids in the release of polyphenolic substances.

TABLE 2.

Effects of different thermal processing methods on functional component content of Aohan millet.

Processing method Polyphenol content (mg/100 g) Flavonoid content (mg/100 g)
AM 344.04 ± 3.29a 58.85 ± 2.15a
S‐AM 149.16 ± 7.17d 32.33 ± 2.46c
F‐AM 222.96 ± 4.71c 49.66 ± 1.60b
E‐AM 303.24 ± 28.72b 30.03 ± 2.80d
Open in a new tab

Note: Mean ± SD (n = 3). Means with different superscripts (a, b) in the same row are significantly different (p < .05).

Abbreviations: AM, Raw Aohan millet; E‐AM, Expanded Aohan millet; F‐AM, Fried Aohan millet; S‐AM, Steamed Aohan millet.

3.3. Effects of heating–processing on amino acids of Aohan millet

Amino acids play a crucial role in enhancing the flavor and color of food, making them a significant determinant of food quality (Yao et al., 2006). Table 3 outlines the impact of different thermal processing methods on the amino acid composition and content of Aohan millet. It was evident that Aohan millet contains 18 amino acids, with a total content ranging from 8.13% to 8.60%. Glutamic acid was the most abundant amino acid, followed by leucine, proline, and aspartic acid. The essential amino acid and total amino acid contents of fried and puffed millet were elevated compared to raw millet, although the changes were not statistically significant (p > .05). Studies have indicated that increased amino acid content can provide several benefits, including relaxation and nervous system benefits (Nathan et al., 2006). Millet contains eight essential amino acids, with leucine, phenylalanine, and isoleucine being the top three in terms of content. Histidine was an essential amino acid for infants and young children, and its content remains largely unaffected by thermal processing. Glutamic acid holds the highest content among nonessential amino acids, accounting for 1.81% to 1.96%. It was worth noting that the proportion of essential amino acids to the total mass of amino acids in each group ranged from 39.05% to 40.19%, while the proportion of essential amino acids to the total mass of nonessential amino acids ranged from 64.06% to 67.19%, closely aligning with the evaluation criteria of the FAO/WHO (World Health Organization) amino acid model (Herreman et al., 2020).

TABLE 3.

Effects of different thermal processing methods on amino acid content of Aohan millet.

Amino acid types Amino acid content (%)
AM S‐AM F‐AM E‐AM
Sweet amino acids (SAA)
Ala 0.78 ± 0.00c 0.78 ± 0.01c 0.85 ± 0.00a 0.82 ± 0.21b
Gly 0.20 ± 0.00a 0.19 ± 0.01b 0.21 ± 0.01a 0.10 ± 0.01a
Ser 0.41 ± 0.00ab 0.39 ± 0.00b 0.42 ± 0.00a 0.41 ± 0.01ab
Thr* 0.33 ± 0.00b 0.32 ± 0.00c 0.35 ± 0.00a 0.34 ± 0.01b
Pro 0.60 ± 0.01c 0.72 ± 0.01b 0.76 ± 0.00a 0.71 ± 0.07a
Total 2.32 ± 0.01d 2.40 ± 0.03c 2.59 ± 0.01a 2.38 ± 0.31b
Sour and MSG‐like amino acids (SMAA)
Glu 1.89 ± 0.04ab 1.81 ± 0.01b 1.96 ± 0.01a 1.89 ± 0.06ab
Asp 0.57 ± 0.00a 0.55 ± 0.00b 0.59 ± 0.00a 0.58 ± 0.01a
Total 2.46 ± 0.04ab 2.36 ± 0.01b 2.55 ± 0.01a 2.47 ± 0.07ab
Bitter amino acids (BAA)
Val* 0.42 ± 0.01bc 0.41 ± 0.01c 0.44 ± 0.00a 0.43 ± 0.01ab
Met* 0.20 ± 0.11a 0.16 ± 0.01a 0.10 ± 0.02a 0.17 ± 0.00a
Leu* 1.18 ± 0.02b 1.17 ± 0.00b 1.27 ± 0.00a 1.22 ± 0.04ab
Ile* 0.34 ± 0.01a 0.34 ± 0.00a 0.37 ± 0.01a 0.36 ± 0.01a
Phe* 0.50 ± 0.00b 0.51 ± 0.00b 0.55 ± 0.00a 0.52 ± 0.01b
His 0.17 ± 0.00a 0.16 ± 0.00a 0.17 ± 0.00a 0.17 ± 0.01a
Arg* 0.22 ± 0.00a 0.20 ± 0.01b 0.20 ± 0.01b 0.21 ± 0.01ab
Total 3.03 ± 0.15a 2.95 ± 0.03a 3.10 ± 0.04a 3.09 ± 0.10a
Tasteless amino acids
Lys* 0.14 ± 0.00a 0.12 ± 0.01b 0.10 ± 0.00c 0.09 ± 0.00c
Tyr 0.22 ± 0.03ab 0.19 ± 0.03b 0.18 ± 0.01b 0.26 ± 0.01a
Total 0.36 ± 0.03a 0.31 ± 0.04ab 0.28 ± 0.01b 0.35 ± 0.01a
Other amino acids
Cys 0.13 ± 0.01a 0.14 ± 0.01a 0.12 ± 0.01a 0.12 ± 0.01a
NH3 0.20 ± 0.01b 0.20 ± 0.00ab 0.22 ± 0.01a 0.21 ± 0.01ab
Total 0.33 ± 0.02ab 0.34 ± 0.01a 0.34 ± 0.02ab 0.33 ± 0.02b
Essential amino acids 3.32 ± 0.14a 3.22 ± 0.01a 3.37 ± 0.04a 3.33 ± 0.09a
Nonessential amino acid 4.94 ± 0.08b 4.91 ± 0.04b 5.24 ± 0.03a 5.19 ± 0.08a
Total amino acids 8.26 ± 0.23ab 8.13 ± 0.06b 8.60 ± 0.06a 8.52 ± 0.18ab
Essential Amino Acids/Total amino acids 40.19 ± 0.61a 39.61 ± 0.10ab 39.10 ± 0.12b 39.05 ± 0.27b
Essential Amino Acids/Nonessential amino acid 67.19 ± 1.71a 65.58 ± 0.28ab 64.22 ± 0.33b 64.06 ± 0.72b
Open in a new tab

Note: Mean ± SD (n = 3). Means with different superscripts (a, b) in the same row are significantly different (p < .05).

Abbreviations: AM, Raw Aohan millet; E‐AM, Expanded Aohan millet; F‐AM, Fried Aohan millet; S‐AM, Steamed Aohan millet.

*

Indicates essential amino acids.

Amino acids, such as alanine, glycine, serine, and threonine, impart a sweet taste, while glutamic and aspartic acids contribute to a pleasant fresh taste. Valine, methionine, leucine, isoleucine, phenylalanine, histidine, and arginine are associated with a bitter taste (Li‐Chan & Cheung, 2010). As depicted in Table 3, the content of sweet amino acids was significantly higher (p < .05) in F‐AM, along with elevated levels of fresh and bitter amino acids. Conversely, S‐AM exhibited the least amount of bitter amino acids, suggesting that the steaming treatment reduced the bitter flavor. Figure 1 further demonstrates that F‐AM contained a higher proportion of sweet, fresh, and bitter amino acids, while raw millet contained more odorless amino acids. Consequently, Aohan millet exhibits improved flavor characteristics to some extent after undergoing thermal processing, with the most noticeable enhancement observed in fried millet.

FIGURE 1.

FIGURE 1

Open in a new tab

Radar graph of amino acids in Aohan millet under different hot processing methods. AM, Aohan millet; F‐AM, Fried Aohan millet; E‐AM, Expanded Aohan millet; S‐AM, Steamed Aohan millet. Sweet = Ala+Gly + Ser + Thr + Pro; Umami = GLU + ASP; Bitter = Val + Met+Leu + Ile + Phe + His+Arg; Tasteless = Lys + Tyr; Other = Cys + NH3.

3.4. Gas‐phase analysis of the fatty acid composition and content of Aohan millet

Gas‐phase analysis of the fatty acid composition and content of Aohan millet revealed essential findings, as elucidated in Table 4. It was evident that saturated fatty acids are 28.26% of the total mass of total fatty acids, with palmitic acid being the highest (388.65 mg/100 g). Furthermore, unsaturated fatty acids contribute to 71.74% of the total fatty acid content, with linoleic acid being the most prevalent at 1208.70 mg/100 g, followed by oleic acid (258.35 mg/100 g). The millet is rich in fatty acids. Palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid are the main components of foxtail millet (Li et al., 2020), and it bears resemblance to this result. These findings underscore the high‐quality fat content in millet, particularly due to the presence of linoleic and oleic acids, which confer hypoglycemic and hypolipidemic properties, thereby promoting human health and averting diseases (Annor et al., 2015; Ren et al., 2021). It was noteworthy that both steaming and frying processes resulted in a significant (p < .05) decrease in the levels of saturated and unsaturated fatty acids relative to raw millet, while puffed millet exhibited a nonsignificant (p > .05) increase in both types of fatty acids. This phenomenon was attributed to the release of fatty acids from millet fat cells following high‐temperature treatment and puffing, leading to an expansion in the oil yield area and enhanced fatty acid production (Das & Eun, 2018).

TABLE 4.

Effects of different thermal processing on fatty acid content of Aohan millet.

Fatty acid type Fatty acid content (mg/100 g)
AM S‐AM F‐AM E‐AM
Saturated fatty acid
Decanoic acid (C15:0) 3.90 ± 0.28a 4.00 ± 0.28a 4.15 ± 0.21a 4.15 ± 0.21a
Palmitic acid (C16:0) 388.65 ± 26.66a 358.95 ± 15.06a 356.85 ± 8.27a 404.05 ± 18.60a
Stearic acid (C18:0) 142.30 ± 9.62a 80.55 ± 3.32b 87.75 ± 2.05b 145.55 ± 7.28a
Eicosanoic acid (C20:0) 42.10 ± 3.11a 22.50 ± 1.13b 24.70 ± 0.99b 42.80 ± 2.12a
Heneicosanoic Acid (C21:0) ND ND ND 1.65 ± 2.33a
Behenic acid (C22:0) 15.60 ± 1.13a 9.00 ± 0.42b 9.55 ± 0.21b 16.00 ± 0.85a
Tricosanoic acid (C23:0) 5.45 ± 0.35a 5.40 ± 0.28a 4.95 ± 0.07a 5.80 ± 0.42a
Lignoceric acid (C24:0) 7.60 ± 0.42a ND ND 8.15 ± 0.49a
Total saturated fatty acid 605.60 ± 41.58a 480.40 ± 20.51b 487.95 ± 11.81b 628.15 ± 32.31a
Unsaturated fatty acid
Oleic acid (C18:1n9c) 258.35 ± 17.47a 162.15 ± 6.86b 17.44 ± 0.43c 260.55 ± 13.22a
cis‐11‐Eicosenoic acid (C20:1) 6.45 ± 0.49a 3.95 ± 0.21b 4.25 ± 0.07b 6.70 ± 0.28a
Erucic acid (C22:1n9) 5.15 ± 0.49b 4.00 ± 0.14c 5.80 ± 0.14b 9.85 ± 0.49a
Linoleic acid (C18:2n6c) 1208.70 ± 83.86a 800.30 ± 33.66b 845.30 ± 18.38b 1217.10 ± 57.98a
αLinolenic acid (C18:3n3) 58.55 ± 4.03a 44.00 ± 1.98b 45.40 ± 0.99b 58.70 ± 2.83a
Total unsaturated fatty acids 1537.20 ± 106.35a 1014.40 ± 42.85b 1075.10 ± 23.90b 1552.90 ± 74.81a
Total fatty acids 2142.80 ± 147.93a 1494.80 ± 63.36b 1563.05 ± 35.71b 2181.05 ± 107.13a
Saturated fatty acids/total fatty acids 28.26 ± 0.01d 32.14 ± 0.01a 31.21 ± 0.04b 28.80 ± 0.07c
Unsaturated fatty acids/total fatty acids 71.74 ± 0.01a 67.86 ± 0.01d 68.78 ± 0.04c 71.20 ± 0.07b
Open in a new tab

Note: Mean ± SD (n = 3). Means with different superscript (a, b) in the same row are significantly different (p < .05).

Abbreviations: AM, Raw Aohan millet; E‐AM, Expanded Aohan millet; F‐AM, Fried Aohan millet; S‐AM, Steamed Aohan millet.

3.5. HS‐SPME‐GC–MS analysis of volatile components of Aohan millet

An HS‐SPME‐GC–MS analysis was conducted to examine the volatile components of Aohan millet under various heat treatments. The analysis employed the headspace solid‐phase microextraction (HS‐SPME) method, combined with gas chromatography–mass spectrometry (GC–MS). The chromatographic data were cross‐referenced with the NIST14 (National Institute of Standards and Technology) spectral library and manually analyzed. The outcomes presented in Table 5 demonstrate alterations in volatile flavor substances in Aohan millet following different heat treatments. The results indicated that Aohan millet contains 53 volatile flavor compounds, including 6 esters, 3 aldehydes, 9 ketones, 3 acids, 17 alkanes, 1 nitrogen‐containing compound, 6 aromatic compounds, 5 heterocyclic compounds, 1 alcohol, and 2 oxides. Of these compounds, 80, 50, and 55 volatile compounds were detected after steaming, frying, and puffing, respectively. Notably, the variety of volatile flavor substances in Aohan millet significantly expanded following the steaming process, with a notable increase in esters, aldehydes, nitrogen‐containing compounds, and heterocyclic compounds compared to raw millet. In steamed millet, the highest content of veratraldehyde was 55.50%, which contributes to a sweet flavor and enhances the taste of steamed millet. Meanwhile, fried and puffed millet exhibited the highest piperonal content at 34.76% and 39.14%, respectively, among the volatile compounds. A comparison with raw millet unveiled significantly higher levels of aldehydes, amines, olefins, alcohols, and heterocyclic compounds in all three heat processing methods, which can be attributed to the structural changes that occur due to heating and the consequent generation of certain compounds. The elevated aldehyde content may be on the one hand attributed to oxidative degradation of unsaturated fatty acids (Shi et al., 2019). However, it was worth noting that aldehydes play a role in the creation of the fragrant aroma of cooked millet (Bi et al., 2019). On the other hand, it may be explained by the occurrence of a Meladic reaction after heat treatment of millet, which promotes the production of aldehydes (Bai et al., 2022; Lykomitros et al., 2016). A previous study by Li. reported the identification of 62 volatile compounds in millet using HS‐SPME‐GC–MS, including 18 aldehydes, 6 alcohols, 9 ketones, 5 acids, 10 hydrocarbons, 10 benzene derivatives, and 4 other components (Li, Zhao, Liu, Zhang, et al., 2021). Similarly, Yang identified 8 fatty acids, 7 essential amino acids, and 59 volatile compounds in glutinous and non‐glutinous millet porridges, with components, such as 6 alcohols, 14 aldehydes, 22 alkanes, 4 ketones, 1 benzene, 8 acids and esters, 2 amines, 1 heterocyclic group, and 1 olefin contributing to the flavor profile (Yang et al., 2021). These findings align with the results of the current study.

TABLE 5.

Effects of different thermal processing on volatile organic compounds of Aohan millet.

Compound number Retention time (min) Compound CAS Molecular formula Relative content (%)
AM S‐AM F‐AM E‐AM
Esters (20)
VOC1 3.383 Acetic acid, dimethoxy‐, methyl ester 89–91‐8 C5H10O4 / / 0.64 /
VOC2 4.651 2‐Propenoic acid, 3‐[4‐(acetyloxy)‐3‐methoxyphenyl]‐, methyl ester 2309‐08‐2 C13H14O5 / / 0.16 /
VOC3 4.670 3,4‐Dimethyl‐2‐(3‐methyl‐butyryl)‐benzoic acid, methyl ester 71940–29‐9 C15H20O3 / / 0.35 /
VOC4 4.684 1,4‐Benzenedicarboxylic acid, 2‐amino‐, dimethyl ester 5372‐81‐6 C10H11NO4 / / / 0.30
VOC5 4.688 1,2‐Benzenedicarboxylic acid, 4‐nitro‐, dimethyl ester 610–22‐0 C10H9NO6 0.20 / / 0.18
VOC6 4.770 1,4‐Cyclopentadiene‐1‐carboxylic acid, 3‐[1‐(dimethylamino)ethylidene]‐, methyl ester 14485–75‐7 C11H15NO2 / 0.14 / /
VOC7 4.792 1,2‐Benzenedicarboxylic acid, 4‐amino‐, dimethyl ester 51832–31‐6 C10H11NO4 / 0.24 / /
VOC8 4.823 Benzoic acid, 2‐formyl‐4,6‐dimethoxy‐, 7‐formylhept‐2‐yl ester 312305–59‐2 C18H24O6 1.10 0.12 / /
VOC9 6.660 Carbamic acid, methyl‐, 3‐methylphenyl ester 1129–41‐5 C9H11NO2 / 0.90 / /
VOC10 6.730 Acetic acid, 4‐methylphenyl ester 140–39‐6 C9H10O2 / 0.27 / /
VOC11 7.764 Methyl 2‐butynoate 23326–27‐4 C5H6O2 / 0.62 / 0.41
VOC12 8.454 di‐tert‐butyl dicarbonate 24424–99‐5 C10H18O5 / / / 0.80
VOC13 8.504 Propanoic acid, ethenyl ester 105–38‐4 C5H8O2 1.67 / / /
VOC14 14.805 t‐Butyl cinnamate 7042‐36‐6 C13H16O2 / 0.23 / /
VOC15 18.888 2,2,4‐Trimethyl‐1,3‐pentanediol diisobutyrate 6846‐50‐0 C16H30O4 0.99 0.67 / /
VOC16 19.452 Propanoic acid, 2‐methyl‐, 2‐methyl‐2‐propenyl ester 816–73‐9 C8H14O2 / / 0.58 /
VOC17 21.527 Dimethyl phthalate 131–11‐3 C10H10O4 / / / 0.72
VOC18 24.886 Diethyl Phthalate 84–66‐2 C12H14O4 / / / 0.66
VOC19 25.453 3‐Methylbutyric acid, 2‐biphenyl‐4‐yl‐2‐oxoethyl ester 4376–32‐3 C19H20O3 1.08 / / /
VOC20 29.636 Phenyl salicylate 118–55‐8 C13H10O3 0.78 / / /
Total 5.82 3.19 1.73 3.07
Alkanes (32)
VOC21 8.982 1,2‐Di(2,4,6‐trimethylphenyl)ethane 4674–23‐1 C20H26 / 0.20 / /
VOC22 10.669 Cyclopentane, 1‐ethyl‐1‐methyl‐ 16747–50‐5 C8H16 2.50 / / /
VOC23 11.008 Oxetane, 3‐(1‐methylethyl)‐ 10317–17‐6 C6H12O 0.98 / / /
VOC24 11.035 Cyclopentane, propyl‐ 2040‐96‐2 C8H16 6.22 / / /
VOC25 11.989 Cyclopentane, methyl‐ 96–37‐7 C6H12 / / 2.14 0.51
VOC26 13.907 Cyclopentane, 1,1,3‐trimethyl‐ 4516‐69‐2 C8H16 / / / 0.44
VOC27 14.706 Dodecane 112–40‐3 C12H26 3.64 1.26 2.61 0.74
VOC28 16.550 cis‐1‐Hydroxybicyclo[4.4.0]decane 3574‐58‐1 C10H18O / 0.49 / /
VOC29 17.458 Heptane, 2,2,4‐trimethyl‐ 14720–74‐2 C10H22 / 0.24 / /
VOC30 17.459 2,2,6,6‐Tetramethylheptane 40117–45‐1 C11H24 / 0.23 / /
VOC31 17.475 Decane, 3‐methyl‐ 13151–34‐3 C11H24 / / 0.62 /
VOC32 17.475 Tridecane 629–50‐5 C13H28 0.88 / / 0.51
VOC33 18.899 2,3’‐Bifuran, octahydro‐ 73373–15‐6 C8H14O2 1.06 / / /
VOC34 19.324 Undecane, 5,5‐dimethyl‐ 17312–73‐1 C13H28 / / / 0.18
VOC35 20.085 Decane, 2,5‐dimethyl‐ 17312–50‐4 C12H26 / / / 1.37
VOC36 20.087 Tetradecane 629–59‐4 C14H30 4.62 1.43 2.82 1.77
VOC37 22.576 Pentadecane 629–62‐9 C15H32 1.68 1.19 2.63 1.08
VOC38 22.960 Tetracyano‐p‐quinodimethane 1518‐16‐7 C12H4N4 / 0.39 / /
VOC39 24.246 Hexadecane, 2‐methyl‐ 1560–92‐5 C17H36 / / 0.76 /
VOC40 24.253 Pentadecane, 3‐methyl‐ 2882‐96‐4 C16H34 1.05 / / /
VOC41 24.923 Hexadecane 544–76‐3 C16H34 3.74 1.03 2.35 1.73
VOC42 26.041 Nonane, 2,2,4,4,6,8,8‐heptamethyl‐ 4390–04‐9 C16H34 0.87 0.24 / /
VOC43 26.044 Pentadecane, 2,6,10‐trimethyl‐ 3892‐00‐0 C18H38 / / 1.65 /
VOC44 26.181 Cyclohexane, tetradecyl‐ 1795‐18‐2 C20H40 / 0.69 / /
VOC45 27.161 Heptadecane 629–78‐7 C17H36 1.83 0.77 1.94 /
VOC46 27.175 Heptacosane 593–49‐7 C27H56 1.95 0.55 0.42 /
VOC47 27.176 Hexadecane, 7‐methyl‐ 26730–20‐1 C17H36 / / 1.06 /
VOC48 27.295 Pentadecane，2,6,10,14‐tetramethyl‐ 1921‐70‐6 C19H40 4.30 0.51 / 0.79
VOC49 29.447 Octadecane 593–45‐3 C18H38 1.99 / / /
VOC50 29.630 Benzene, 1,1′‐[1,2‐ethanediylbis(oxy)]bis‐ 104–66‐5 C14H14O2 4.65 1.19 2.14 /
VOC51 29.678 Pentadecane, 4‐methyl‐ 2801‐87‐8 C16H34 1.91 / / /
VOC52 29.689 Tridecane, 2,5‐dimethyl‐ 56292–66‐1 C15H32 / / 1.07 /
Total 43.87 10.41 22.21 9.12
Phenols (6)
VOC53 4.828 2‐Propenoic acid, 3‐(3,4‐dimethoxyphenyl)‐, (E)‐ 14737–89‐4 C11H12O4 9.45 0.76 / /
VOC54 17.870 Phenol, 5‐ethenyl‐2‐methoxy‐ 621–58‐9 C9H10O2 / 3.26 1.27 4.97
VOC55 17.971 Phenol, 4‐(1‐methylpropyl)‐ 99–71‐8 C10H14O / / / 1.04
VOC56 17.972 Phenol, 2‐(1‐methylpropyl)‐ 89–72‐5 C10H14O / 0.17 / /
VOC57 22.914 2,4‐Di‐tert‐butylphenol 96–76‐4 C14H22O / 1.78 3.59 /
VOC58 22.956 Phenol, 2,4,6‐tris(1‐methylethyl)‐ 2934‐07‐8 C15H24O / 1.14 / /
Total 9.45 7.11 4.86 6.01
Acids (10)
VOC59 3.396 Acetic acid 64–19‐7 C2H4O2 / / / 0.27
VOC60 4.527 6‐Methoxy‐3‐methyl‐2‐benzofurancarboxylic acid 10410–29‐4 C11H10O4 / 0.05 / /
VOC61 4.670 3,4‐Dimethoxycinnamic acid 2316–26‐9 C11H12O4 / 1.15 / /
VOC62 4.815 4‐Diethylaminosalicylic acid 23050–90‐0 C11H15NO3 / / 0.38 /
VOC63 9.009 8‐Phenylquinoline‐6‐carboxylic acid 35871–15‐9 C16H11NO2 / / 0.81 /
VOC64 12.338 9,10‐Dihydrophenanthren‐2‐butyric acid 7494‐59‐9 C18H18O2 / 0.13 / /
VOC65 14.881 2H‐Pyran‐2,6(3H)‐dione, dihydro‐4,4‐dimethyl‐ 4160‐82‐1 C7H10O3 / / / 0.29
VOC66 19.451 Propanoic acid, 2‐methyl‐, 3‐hydroxy‐2,2,4‐trimethylpentyl ester 77–68‐9 C12H24O3 3.30 0.91 2.06 1.05
VOC67 22.907 [2,2’‐Bifuran]‐3‐carboxylic acid, 5′‐methyl‐, methyl ester 5896–31‐1 C11H10O4 / / / 0.30
VOC68 22.915 3,4‐Methylenedioxycinnamic acid 2373‐80‐0 C10H8O4 1.02 / / /
Total 4.32 3.24 3.25 1.91
Aldehydes (12)
VOC69 10.241 Benzeneacetaldehyde 122–78‐1 C8H8O / / / 0.59
VOC70 11.990 Nonanal 124–19‐6 C9H18O 12.60 2.52 7.89 4.71
VOC71 12.004 Furfural 98–01‐1 C5H4O2 / 0.26 / /
VOC72 13.584 2‐Nonenal, (E)‐ 18829–56‐6 C9H16O 4.19 / 3.18 /
VOC73 14.747 1,3‐Cyclohexadiene‐1‐carboxaldehyde, 2,6,6‐trimethyl‐ 116–26‐7 C10H14O / / / 0.43
VOC74 14.891 Decanal 112–31‐2 C10H20O / / / 0.69
VOC75 15.279 Benzaldehyde, 4‐methyl‐ 104–87‐0 C8H8O / 0.32 / /
VOC76 17.921 2,4‐Decadienal, (E,E)‐ 25152–84‐5 C10H16O / / 1.97 4.43
VOC77 18.387 Piperonal 120–57‐0 C8H6O3 / 1.70 34.76 39.14
VOC78 19.167 2(3H)‐Furanone, 5‐heptyldihydro‐ 104–67‐6 C11H20O2 / / / 0.31
VOC79 22.174 Benzaldehyde, 2,4‐dihydroxy‐3,6‐dimethyl‐ 34883–14‐2 C9H10O3 0.27 / / /
VOC80 22.189 Benzaldehyde, 3,4‐dimethoxy‐ 120–14‐9 C9H10O3 / 55.50 1.15 /
Total 17.06 60.3 48.95 50.3
Ketones (18)
VOC81 7.883 1,3,5‐Triphenyl‐1,5‐pentanedione 6263‐84‐9 C23H20O2 / 0.26 / /
VOC82 9.506 1,2‐Propanedione, 1‐phenyl‐ 579–07‐7 C9H8O2 / / 0.42 /
VOC83 9.627 4,6‐Heptadiyn‐3‐one 29743–27‐9 C7H6O / / / 0.42
VOC84 11.981 4‐Pyranone, 2,3‐dihydro‐ 84302–42‐1 C5H6O2 2.08 / / /
VOC85 11.990 4(1H)‐Pyridone 108–96‐3 C5H5NO 1.77 / / /
VOC86 17.873 Ethanone, 1‐(2‐hydroxy‐5‐methylphenyl)‐ 1450‐72‐2 C9H10O2 / / 1.21 /
VOC87 18.297 5‐(p‐tert‐Butylphenoxymethyl)‐3‐(O‐tolyl)‐2‐oxazolidone 5198‐41‐4 C21H25NO3 0.15 / / /
VOC88 18.400 5,6,7,8‐Tetrahydro‐6‐oxopteridine 51036–16‐9 C6H6N4O / 0.58 / /
VOC89 20.350 2‐Hexen‐1‐one, 1‐(2‐hydroxy‐5‐methylphenyl)‐ 51956–79‐7 C13H16O2 0.70 / / /
VOC90 21.453 5,9‐Undecadien‐2‐one, 6,10‐dimethyl‐, (E)‐ 3796‐70‐1 C13H22O 2.38 0.60 1.69 1.21
VOC91 21.538 .delta.2‐1,3,4‐Oxadiazolin‐5‐one, 2‐(4‐pyridyl)‐ 2845‐82‐1 C7H5N3O2 0.64 / / /
VOC92 22.167 3‐Butyn‐2‐one 1423‐60‐5 C4H4O / 0.43 / /
VOC93 22.600 7H‐Indeno[2,1‐a]anthracen‐7‐one 27582–45‐2 C21H12O 0.16 / / /
VOC94 24.242 Ethanone, 1,2‐diphenyl‐ 451–40‐1 C14H12O / / / 0.34
VOC95 24.936 Cyclopentanone, 2‐octyl‐ 40566–23‐2 C13H24O / / / 0.52
VOC96 26.560 3(2H)‐Benzofuranone, 6‐methoxy‐2‐[(3‐methoxyphenyl)methylene]‐, (E)‐ 77764–84‐2 C17H14O4 / 0.28 / /
VOC97 27.160 l‐Pyrrolid‐2‐one, N‐carbamoyl‐ 40451–67‐0 C5H8N2O2 / / 0.21 /
VOC98 29.635 4,4’‐Dihydroxybenzophenone 611–99‐4 C13H10O3 1.04 / / /
Total 8.92 2.15 3.53 2.49
Amines (14)
VOC99 3.902 Methyl‐methoxy‐hydroxymethyl‐amine 6919‐52‐4 C3H9NO2 / / / 0.34
VOC100 6.709 Benzenamine, 4‐propyl‐ 2696‐84‐6 C9H13N / 0.05 / /
VOC101 7.899 Benzenamine, 4‐(hexyloxy)‐ 39905–57‐2 C12H19NO / / / 0.40
VOC102 9.077 5‐Dimethylaminopyrimidine 31401–46‐4 C6H9N3 / 1.04 / /
VOC103 11.979 L‐Prolinamide 7531‐52‐4 C5H10N2O / 0.69 / /
VOC104 11.985 Cyclopentanamine 1003‐03‐8 C5H11N / / / 0.71
VOC105 14.710 Cyclohexanamine, N,N‐dimethyl‐ 98–94‐2 C8H17N / 0.36 / /
VOC106 14.891 1,1‐Diethylpropargylamine 3234‐64‐8 C7H13N 0.48 / / /
VOC107 17.877 4‐Hydroxyphenylacetamide 17194–82‐0 C8H9NO2 / 0.48 / /
VOC108 17.930 3‐(5‐Methylfuryl)‐N‐furamidopropionamide 331958–18‐0 C13H14N2O4 / 0.17 / /
VOC109 24.512 Benzamide, N‐acetyl‐ 1575‐95‐7 C9H9NO2 / / / 0.32
VOC110 24.923 1,3,5‐Triazine‐2,4,6‐triamine 108–78‐1 C3H6N6 / / 0.38 /
VOC111 25.125 Benzamide, 4‐ethoxy‐ 55836–71‐0 C9H11NO2 / / / 0.19
VOC112 29.645 Salicylanilide 87–17‐2 C13H11NO2 / 0.23 / /
Total 0.48 3.02 0.38 1.96
Olefins (6)
VOC113 13.584 2‐Octene, 4‐ethyl‐, (E)‐ 74630–09‐4 C10H20 / 0.61 / /
VOC114 17.972 5‐Pentylcyclohexa‐1,3‐diene 56318–84‐4 C11H18 / / 1.35 /
VOC115 19.455 Cyclobuta[1,2‐d:3,4‐d’]bis[1,3]dioxole, tetrahydro‐, (3a.alpha.,3b.alpha.,6a.alpha.,6b.alpha.)‐ 69956–59‐8 C6H8O4 / 0.25 / /
VOC116 20.346 Longifolene 475–20‐7 C15H24 / / 1.82 /
VOC117 22.193 Benzene, 3‐butenyl‐ 768–56‐9 C10H12 / 0.32 / /
VOC118 22.816 .alpha.‐Farnesene 502–61‐4 C15H24 / / / 0.94
Total 0 1.18 3.17 0.94
Heterocycles (30)
VOC119 4.792 1,6‐Dimethylphenazine 58718–43‐7 C14H12N2 / / 0.70 /
VOC120 6.663 2‐Ethyl‐3,5‐dimethylpyridine 1123‐96‐2 C9H13N / / 0.59 /
VOC121 6.682 2,5‐Dimethylpyrimidine 22868–76‐4 C6H8N2 / 0.54 / /
VOC122 9.023 Quinoxaline, 2,3‐diphenyl‐ 1684‐14‐6 C20H14N2 / / / 1.09
VOC123 9.508 5H‐1‐Pyrindine, 6,7‐dihydro‐ 533–37‐9 C8H9N / 0.34 / /
VOC124 11.270 2‐Aminopurine 452–06‐2 C5H5N5 / 0.73 / /
VOC125 11.984 Aziridine, 1,2,3‐trimethyl‐, trans‐ 693–88‐9 C5H11N / / / 1.26
VOC126 13.583 2‐(2‐Pyrrolidin‐1‐yl‐ethyl)‐pyridine 6311‐90‐6 C11H16N2 0.59 / / /
VOC127 14.250 Azulene 275–51‐4 C10H8 / 0.26 / /
VOC128 14.656 Pyridine, 2‐pentyl‐ 2294‐76‐0 C10H15N / / / 0.62
VOC129 14.710 3‐Amino‐s‐triazole 61–82‐5 C2H4N4 / / 0.68 /
VOC130 15.305 Benzofuran, 2,3‐dihydro‐ 496–16‐2 C8H8O / / / 0.92
VOC131 15.338 Benzofuran, 2‐ethenyl‐ 7522‐79‐4 C10H8O / 0.23 / /
VOC132 15.667 7H‐Dibenzo[b,g]carbazole, 7‐methyl‐ 3557‐49‐1 C21H15N / / 0.24 /
VOC133 16.238 6‐Methyl‐2‐phenyl‐7‐(2,4‐dimethylphenylmethyl)indolizine 64002–75‐1 C24H23N 0.31 / / /
VOC134 17.914 Furan, 2‐hexyl‐ 3777‐70‐6 C10H16O / 1.02 / /
VOC135 17.958 2‐tert‐Butylpyridine 5944‐41‐2 C9H13N / 0.24 / /
VOC136 18.278 1H‐Pyrazole, 4‐methyl‐3‐(4‐methylphenyl)‐1,5‐diphenyl‐ 73306–07‐7 C23H20N2 / 0.22 / /
VOC137 18.417 1,3‐Dioxolane, 2‐phenyl‐2‐(phenylmethyl)‐ 4362‐19‐0 C16H16O2 / / / 13.82
VOC138 18.494 Benzofurazan 273–09‐6 C6H4N2O / / / 0.15
VOC139 19.455 Cyclobuta[1,2‐d:3,4‐d’]bis[1,3]dioxole, tetrahydro‐, (3a.alpha.,3b.beta.,6a.beta.,6b.alpha.)‐ 70004–63‐6 C6H8O4 / 0.24 / /
VOC140 21.523 1H‐1,2,3‐Triazole, 4‐methyl‐5‐(5‐methyl‐1H‐pyrazol‐3‐yl)‐ 51719–86‐9 C7H9N5 / 0.11 / /
VOC141 22.656 1H‐Indole, 1,3‐dimethyl‐5,6‐dimethoxy‐2‐(3,5‐dimethoxyphenyl)‐ 156785–76‐1 C20H23NO4 / / / 1.55
VOC142 22.906 3,4‐Dihydro‐4‐imino‐3‐methoxyquinazoline 15018–64‐1 C9H9N3O / / / 0.24
VOC143 22.947 Furan, 2,5‐diphenyl‐ 955–83‐9 C16H12O / / 0.32 /
VOC144 22.965 6‐Nitro‐5‐methoxy‐2,3‐dimethylindole 53918–83‐5 C11H12N2O3 / 0.19 / /
VOC145 24.885 4‐Amino‐2‐(4′‐cyanobutyl)‐5,6‐trimethylene‐pyrimidine 30036–58‐9 C12H16N4 / / / 0.15
VOC146 24.940 2,2’‐Bifuran, octahydro‐ 1592‐33‐2 C8H14O2 / / 0.44 /
VOC147 26.550 1H‐Indole, 3‐(2‐methoxyethyl)‐2‐(2‐pyridyl)‐ 161988–60‐9 C16H16N2O 0.15 / / /
VOC148 27.298 3‐Acetamidofuran 59445–85‐1 C6H7NO2 0.31 / / /
Total 1.36 4.12 2.97 19.8
Aromatic (17)
VOC149 9.009 [1,1’‐Biphenyl]‐4‐carbonitrile, 4′‐ethyl‐ 58743–75‐2 C15H13N / 0.11 / /
VOC150 9.624 Isopropyl phenyl ketone 611–70‐1 C10H12O / / / 0.40
VOC151 12.334 Phenanthrene, 3,6‐dimethoxy‐9,10‐dimethyl‐ 5025‐36‐5 C18H18O2 / / / 0.12
VOC152 13.510 [1,1’‐Biphenyl]‐4‐carbonitrile, 4′‐pentyl‐ 40817–08‐1 C18H19N 0.22 / / /
VOC153 15.877 Benzene, pentamethyl‐ 700–12‐9 C11H16 0.45 / / /
VOC154 16.780 1H‐Indene, 1‐ethyl‐2,3‐dihydro‐ 4830‐99‐3 C11H14 / 0.17 / /
VOC155 17.783 Naphthalene, 1‐methyl‐ 90–12‐0 C11H10 0.43 / 0.77 /
VOC156 18.933 Naphthalene, 1,2‐dihydro‐1,1,6‐trimethyl‐ 30364–38‐6 C13H16 / 0.30 / /
VOC157 18.940 Naphthalene, 1,2‐dihydro‐2,5,7‐trimethyl‐ 53156–03‐9 C13H16 / / / 0.18
VOC158 20.228 Naphthalene, 2,6‐dimethyl‐ 581–42‐0 C12H12 / / 0.28 /
VOC159 20.683 Naphthalene, 1,2‐dimethyl‐ 573–98‐8 C12H12 / / 0.17 /
VOC160 22.511 Fluorene 86–73‐7 C13H10 / 0.20 / /
VOC161 22.961 Butylated hydroxytoluene 128–37‐0 C15H24O / / 3.32 /
VOC162 23.351 Naphthalene, 2,3,6‐trimethyl‐ 829–26‐5 C13H14 / 0.19 / /
VOC163 24.548 1‐Amino‐2‐methylnaphthalene 2246–44‐8 C11H11N / 0.33 / /
VOC164 26.810 1,1’‐Biphenyl, 2,2′,5,5′‐tetramethyl‐ 3075‐84‐1 C16H18 2.27 0.44 / /
VOC165 27.457 Anthracene, 1,2,3,4‐tetrahydro‐9,10‐dimethyl‐ 94573–50‐9 C16H18 0.57 / / 0.70
Total 3.94 1.74 4.54 1.40
Alcohols (4)
VOC166 9.031 [3‐(4‐Methoxyphenyl)‐4,5‐dihydro‐1,2‐oxazol‐5‐yl]methanol 206055–84‐7 C11H13NO3 0.06 / / /
VOC167 17.869 1,2‐Benzisoxazol‐3(2H)‐one 21725–69‐9 C7H5NO2 / 0.93 / /
VOC168 20.092 4‐Methyl‐1,6‐heptadien‐4‐ol 25201–40‐5 C8H14O / / 0.84 /
VOC169 25.127 Cedrol 77–53‐2 C15H26O / / 1.11 1.17
Total 0.06 0.93 1.95 1.17
Ethers (3)
VOC170 6.570 3‐Dimethylaminoanisole 15799–79‐8 C9H13NO / 0.11 / /
VOC171 9.058 4‐Hexylanisole 81693–80‐3 C13H20O / 0.05 / /
VOC172 21.927 3‐tert‐Butyl‐4‐hydroxyanisole 121–00‐6 C11H16O2 / / / 0.53
Total 0 0.16 0 0.53
Oxides (2)
VOC173 14.708 Di‐tert‐butyl peroxide 110–05‐4 C8H18O2 1.72 / / /
VOC174 26.806 1‐Methylphenazine 5‐oxide 14202–95‐0 C13H10N2O 0.47 / / /
Total 2.19 0 0 0
Quinones (1)
VOC175 9.032 Anthraquinone, 2,3,6,7‐tetramethyl‐ 15247–68‐4 C18H16O2 / 0.21 / /
Others (6)
VOC176 4.598 N‐Methylcoclaurine 3423‐07‐2 C18H21NO3 / 0.35 / /
VOC177 4.673 Hydrastine 118–08‐1 C21H21NO6 / / 0.26 /
VOC178 4.840 (.+/−.)‐Calycotomine 4356‐47‐2 C12H17NO3 / 0.21 0.48 /
VOC179 12.000 Acetaldehyde, butylhydrazone 20607–72‐1 C6H14N2 1.25 / / /
VOC180 13.566 2‐Cyanoguanidine 127099–85‐8 C2H4N4 / / 0.83 /
VOC181 14.714 anti‐2‐Acetoxyacetaldoxime 37858–07‐4 C4H7NO3 / / 0.88 /
Total 1.25 0.56 2.45 0
Open in a new tab

Abbreviations: AM, Raw Aohan millet; E‐AM, Expanded Aohan millet; F‐AM, Fried Aohan millet; S‐AM, Steamed Aohan millet.

3.6. Principal component analysis (PCA)

Principal component analysis (PCA) was performed to evaluate the impact of different thermal processing methods on Aohan millet. The PCA scores, plotted in three‐dimensions (3D), employed amino acid and fatty acid composition and content as classification criteria, as illustrated in Figure 2. The results revealed that the first principal component (PCA1) contributed 62.9% of the variance, second principal component (PCA2) contributed 19.6%, and third principal component (PCA3) contributed 10.3%. The cumulative contribution of the first three eigenvalues accounted for 92.8% of the total variance, indicating that the top three principal components encapsulated the bulk of the information from the indicators. Consequently, these top three eigenvalues were employed. The figure visually conveys that Aohan millet samples treated with different heating methods occupy distinct regions. Raw Aohan millet was positioned at the center, while the three distinct heat treatments induced significant divergence in amino acid and fatty acid composition and content in the millet. This implies that steamed, fried, and puffed Aohan millet exhibited dissimilarities in amino acid and fatty acid profiles, which offer opportunities for diverse Aohan millet product development.

FIGURE 2.

FIGURE 2

Open in a new tab

The PCA scatterplot of fatty acids in Aohan millet under different hot processing methods.

3.7. Correlation analysis (amino acids and flavor substances, fatty acids, and flavor substances)

The results, as depicted in Figure 3, illustrated significant correlations between specific amino acids and volatile flavor substances. For instance, a highly significant positive correlation was identified between His and ketones (p < .01), whereas His exhibited a highly significant negative correlation with aldehydes and amines (p < .01). Additionally, Phe, Ile, and Ala displayed highly significant positive correlations with alcohols (p < .01) and highly significant negative correlations with esters and phenols (p < .01). Furthermore, several amino acids, including Ser, Glu, Cys, Tyr, His, and Arg, exhibited significant correlations with esters, phenols, and alcohols, as well as other amino acids (p < .05).

FIGURE 3.

FIGURE 3

Open in a new tab

Correlation heat map between amino acids and flavor substances in Aohan millet under different hot processing methods. Red represents positive correlation, blue represents negative correlation, and *represents p < .05.

The correlations between fatty acids and volatile flavor substances of Aohan millet were assessed using thermograms, depicted in Figure 4. Notably, C16:0, C18:3n3, C20:1, and C24:0 exhibited a significant negative correlation solely with olefins (p < .05). Meanwhile, C18:0, C18:1n9c, C18:2n6c, C20:0, C22:0, and C22:1n9 displayed a significant negative correlation with quinones, whereas C23:0 exhibited a significant positive correlation with quinones (p < .05). Furthermore, the relationship between C23:0 and heterocycles displayed a significant negative correlation (p < .05). The oxidation of fatty acids affects the aroma foxtail millet porridge. Therefore, unsaturated fatty acids are more conducive to the formation of Aohan millet flavor substances (Li, Zhao, Liu, Li, et al., 2021).

FIGURE 4.

FIGURE 4

Open in a new tab

Correlation heat map between fatty acids and flavor substances in Aohan millet under different hot processing methods. Red represents positive correlation, blue represents negative correlation, and *represents p < .05.

In summary, the study suggests that the production of volatile flavor compounds in Aohan millet was more closely related to amino acids than fatty acids.

4. CONCLUSION

Steamed millet exhibits elevated protein, fat, and starch content, thereby furnishing the body with essential nutrients and energy. Conversely, puffed millet shows reduced fat and starch levels, rendering it a suitable choice for individuals seeking weight loss. Furthermore, all three millet variants displayed diminished polyphenol and flavonoid concentrations relative to raw millet. Notably, fried and puffed millet exhibited increased amino acid and fatty acid content compared to steamed millet. After subjecting Aohan millet to steaming, there was a substantial increase in flavor compounds, rising from 53 to 80. In contrast, the other two groups did not demonstrate significant changes (p > .05).

The correlation analysis concluded that the connection between amino acids and flavor compounds in Aohan millet, under various thermal processing methods, was more robust than the relationship between fatty acids and flavor compounds. This suggests that the formation of flavor compounds was more closely linked to the types and quantities of amino acids.

Considering both fundamental nutrients and volatile flavor compounds, the steaming method proved to be the most effective. In contrast, the frying method was more effective when evaluating functional components, while the puffing method excelled in terms of amino acid and fatty acid content. The findings of this study offer current and valuable insights into influencing the flavor of Aohan millet during processing and selecting the most suitable processing approach. Nevertheless, the precise mechanistic underpinnings necessitate further exploration, involving an examination of millet's structural characteristics and potential enzyme alterations.

AUTHOR CONTRIBUTIONS

Likun Cheng: Data curation (equal); funding acquisition (equal); methodology (equal); resources (lead); software (equal); writing – original draft (lead). Shuang Qu: Data curation (equal); formal analysis (equal); investigation (equal); visualization (equal). Yueying Yun: Data curation (equal); validation (lead). Yan Ren: Validation (equal). Fucheng Guo: Validation (equal). Yakun Zhang: Conceptualization (equal); supervision (equal); visualization (lead); writing – review and editing (lead). Guoze Wang: Conceptualization (equal); funding acquisition (lead); project administration (lead); supervision (equal).

FUNDING INFORMATION

This work was financially supported by the 2022 Hondlon District Science and Technology Planning Project (YF2022016); The Fundamental Research Funds for Inner Mongolia University of Science & Technology (2023RCTD020, 2024QNJS019); The Special Research Project on Peak Carbon Dioxide Emissions and Carbon Neutralisation in Higher Education Institutions of Inner Mongolia (STZX202229).

CONFLICT OF INTEREST STATEMENT

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.

ETHICS STATEMENT

Ethics approval was not required for this research.

ACKNOWLEDGMENTS

The authors would like to acknowledge Inner Mongolia University of Science and Technology for providing instruments used in the experiments.

Cheng, L. , Qu, S. , Yun, Y. , Ren, Y. , Guo, F. , Zhang, Y. , & Wang, G. (2024). Effects of different thermal processing methods on amino acid, fatty acid, and volatile flavor substance contents of Aohan millet (Golden seedling millet). Food Science & Nutrition, 12, 9007–9024. 10.1002/fsn3.4409

Contributor Information

Yakun Zhang, Email: zhykun12@163.com.

Guoze Wang, Email: wgz13789726841@126.com.

DATA AVAILABILITY STATEMENT

The data presented in this study are available on request from the corresponding author.

REFERENCES

  1. Adom, K. K. , Sorrells, M. E. , & Liu, R. H. (2003). Phytochemical profiles and antioxidant activity of wheat varieties. Journal of Agricultural and Food Chemistry, 51(26), 7825–7834. 10.1021/jf030404l [DOI] [PubMed] [Google Scholar]
  2. Annor, G. A. , Marcone, M. , Corredig, M. , Bertoft, E. , & Seetharaman, K. (2015). Effects of the amount and type of fatty acids present in millets on their in vitro starch digestibility and expected glycemic index (eGI). Journal of Cereal Science, 64, 76–81. 10.1016/j.jcs.2015.05.004 [DOI] [Google Scholar]
  3. Bai, X. , Zhang, M. , Zhang, Y. , Zhang, J. , Wang, C. , & Zhang, Y. (2021). Effect of steam, microwave, and hot‐air drying on antioxidant capacity and in vitro digestion properties of polyphenols in oat bran. Journal of Food Processing and Preservation, 45(12), e16013. 10.1111/jfpp.16013 [DOI] [Google Scholar]
  4. Bai, X. , Zhang, M. , Zhang, Y. , Zhang, Y. , Guo, X. , & Huo, R. (2022). Effects of pretreatment on the volatile composition, amino acid, and fatty acid content of oat bran. Foods, 11(19), 3070. 10.3390/foods11193070 [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bi, S. , Wang, A. , Lao, F. , Shen, Q. , Liao, X. , Zhang, P. , & Wu, J. (2021). Effects of frying, roasting and boiling on aroma profiles of adzuki beans (Vigna angularis) and potential of adzuki bean and millet flours to improve flavor and sensory characteristics of biscuits. Food Chemistry, 339, 127878. 10.1016/j.foodchem.2020.127878 [DOI] [PubMed] [Google Scholar]
  6. Bi, S. , Wang, A. , Wang, Y. , Xu, X. , Luo, D. , Shen, Q. , & Wu, J. (2019). Effect of cooking on aroma profiles of Chinese foxtail millet (Setaria italica) and correlation with sensory quality. Food Chemistry, 289, 680–692. 10.1016/j.foodchem.2019.03.108 [DOI] [PubMed] [Google Scholar]
  7. Bureau, S. , Mouhoubi, S. , Touloumet, L. , Garcia, C. , Moreau, F. , Bédouet, V. , & Renard, C. M. G. C. (2015). Are folates, carotenoids and vitamin C affected by cooking? Four domestic procedures are compared on a large diversity of frozen vegetables. LWT‐ Food Science and Technology, 64(2), 735–741. 10.1016/j.lwt.2015.06.016 [DOI] [Google Scholar]
  8. Das, P. R. , & Eun, J.‐B. (2018). A comparative study of ultra‐sonication and agitation extraction techniques on bioactive metabolites of green tea extract. Food Chemistry, 253, 22–29. 10.1016/j.foodchem.2018.01.080 [DOI] [PubMed] [Google Scholar]
  9. Dharmaraj, U. , Ravi, R. , & Malleshi, N. G. (2012). Physicochemical and textural characteristics of expanded finger millet. International Journal of Food Properties, 15(2), 336–349. 10.1080/10942912.2010.487626 [DOI] [Google Scholar]
  10. Feng, L. (2020). Determination and analysis on minerals profile of commonbuckwheat, naked oat and millet from inner mongo‐lia. Inner Mongolia Agricultural University. [Google Scholar]
  11. Gay, M. , Lempereur, L. , Francis, F. , & Caparros Megido, R. (2020). Control of Dermanyssus gallinae (De Geer 1778) and other mites with volatile organic compounds, a review. Parasitology, 147(7), 731–739. 10.1017/s0031182020000530 [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Herreman, L. , Nommensen, P. , Pennings, B. , & Laus, M. C. (2020). Comprehensive overview of the quality of plant – and animal‐sourced proteins based on the digestible indispensable amino acid score. Food Science & Nutrition, 8(10), 5379–5391. 10.1002/fsn3.1809 [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Honicky, M. , Cardoso, S. M. , de Lima, L. R. A. , Ozcariz, S. G. I. , Vieira, F. G. K. , de Carlos Back, I. , & Moreno, Y. M. F. (2020). Added sugar and trans fatty acid intake and sedentary behavior were associated with excess total‐body and central adiposity in children and adolescents with congenital heart disease. Pediatric Obesity, 15(6), e12623. 10.1111/ijpo.12623 [DOI] [PubMed] [Google Scholar]
  14. Huang, M. , Zhang, H. , Zhao, C. , Chen, G. , & Zou, Y. (2019). Amino acid content in rice grains is affected by high temperature during the early grain‐filling period. Scientific Reports, 9(1). 10.1038/s41598-019-38883-2 [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Huang, Y. , Liu, C. , Ge, Z. , Huang, F. , Tang, H. , Zhou, Q. , Liu, R. , Huang, J. , & Zheng, C. (2023). Influence of different thermal treatment methods on the processing qualities of sesame seeds and cold‐pressed oil. Food Chemistry, 404, 134683. 10.1016/j.foodchem.2022.134683 [DOI] [PubMed] [Google Scholar]
  16. Jia, X. , Sun, Y. , Wang, L. , Sun, W. , Zhao, Z. , Lee, H. F. , Huang, W. , Wu, S. , & Lu, H. (2016). The transition of human subsistence strategies in relation to climate change during the bronze age in the west Liao River basin, Northeast China. The Holocene, 26(5), 781–789. 10.1177/0959683615618262 [DOI] [Google Scholar]
  17. Jones, M. (2017). Archaeology shows there's more to millet than birdseed. https://www.cam.ac.uk/research/features/archaeology‐shows‐theres‐more‐to‐millet‐than‐birdseed
  18. Jongyingcharoen, J. S. , & Ahmad, I. (2014). Thermal and non‐thermal processing of functional foods. Functional Foods and Dietary Supplements, 11, 295–324. [Google Scholar]
  19. Koplík, R. , Mestek, O. , Komínková, J. , Borková, M. , & Suchánek, M. (2004). Effect of cooking on phosphorus and trace elements species in peas. Food Chemistry, 85(1), 31–39. 10.1016/j.foodchem.2003.05.004 [DOI] [Google Scholar]
  20. Li, P. , Zhao, W. , Liu, Y. , Zhang, A. , Liu, S. , Song, R. , Zhang, M. , & Liu, J. (2021). Precursors of volatile organics in foxtail millet (Setaria italica) porridge: The relationship between volatile compounds and five fatty acids upon cooking. Journal of Cereal Science, 100, 103253. 10.1016/j.jcs.2021.103253 [DOI] [Google Scholar]
  21. Li, P. , Zhu, Y. , Li, S. , Zhang, A. , Zhao, W. , Zhang, J. , Chen, Q. , Ren, S. , Liu, J. , & Wang, H. (2020). Variation patterns of the volatiles during germination of the foxtail millet (Setaria italic): The relationship between the volatiles and fatty acids in model experiments. Molecules, 25, e1238. 10.3390/molecules25051238 [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Li, S. , Zhao, W. , Liu, S. , Li, P. , Zhang, A. , Zhang, J. , & Liu, J. (2021). Characterization of nutritional properties and aroma compounds in different colored kernel varieties of foxtail millet (Setaria italica). Journal of Cereal Science, 100, 103248. 10.1016/j.jcs.2021.103248 [DOI] [Google Scholar]
  23. Li‐Chan, E. C. Y. , & Cheung, I. W. Y. (2010). Flavor‐active properties of amino acids, peptides, and proteins. In Mine Y., Li‐Chan E., & Jiang B. (Eds.), Bioactive proteins and peptides as functional foods and nutraceuticals (pp. 341–358). Wiley‐Blackwell. 10.1002/9780813811048.ch23 [DOI] [Google Scholar]
  24. Lykomitros, D. , Fogliano, V. , & Capuano, E. (2016). Flavor of roasted peanuts (Arachis hypogaea) – part I: Effect of raw material and processing technology on flavor, color and fatty acid composition of peanuts. Food Research International, 89, 860–869. 10.1016/j.foodres.2016.09.024 [DOI] [PubMed] [Google Scholar]
  25. Min, Q. , & Zhang, B. (2019). Research progress in the conservation and development of China‐nationally important agricultural heritage systems (China‐NIAHS). Sustainability, 12(1), 1–15. 10.3390/su12010126 [DOI] [Google Scholar]
  26. Mir, S. A. , Bosco, S. J. D. , Shah, M. A. , & Mir, M. M. (2016). Effect of puffing on physical and antioxidant properties of brown rice. Food Chemistry, 191, 139–146. 10.1016/j.foodchem.2014.11.025 [DOI] [PubMed] [Google Scholar]
  27. Nathan, P. , Lu, K. , Gray, M. , & Oliver, C. (2006). The neuropharmacology of L‐theanine (N‐ethyl‐L‐glutamine). Journal of Herbal Pharmacotherapy, 6(2), 21–30. 10.1300/J157v06n02_02 [DOI] [PubMed] [Google Scholar]
  28. Pradeep, S. R. , & Guha, M. (2011). Effect of processing methods on the nutraceutical and antioxidant properties of little millet (Panicum sumatrense) extracts. Food Chemistry, 126(4), 1643–1647. 10.1016/j.foodchem.2010.12.047 [DOI] [PubMed] [Google Scholar]
  29. Ren, X. , Wang, L. , Chen, Z. , Hou, D. , Xue, Y. , Diao, X. , & Shen, Q. (2021). Foxtail millet improves blood glucose metabolism in diabetic rats through pi3k/akt and nf‐κb signaling pathways mediated by gut microbiota. Nutrients, 13(6), 1837. 10.3390/nu13061837 [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Sabuz, A. A. , Rana, M. R. , Ahmed, T. , Molla, M. M. , Islam, N. , Khan, H. H. , Chowdhury, G. F. , Zhao, Q. , & Shen, Q. (2023). Health‐promoting potential of millet: A review. Separations, 10(2), 80. 10.3390/separations10020080 [DOI] [Google Scholar]
  31. Saha, S. , & Roy, A. (2020). Puffed rice: A materialistic understanding of rice puffing and its associated changes in physicochemical and nutritional characteristics. Journal of Food Process Engineering, 43(9). 10.1111/jfpe.13479 [DOI] [Google Scholar]
  32. Shi, Y. , Li, X. , & Huang, A. (2019). A metabolomics‐based approach investigates volatile flavor formation and characteristic compounds of the Dahe black pig dry‐cured ham. Meat Science, 158, 107904. 10.1016/j.meatsci.2019.107904 [DOI] [PubMed] [Google Scholar]
  33. Shigihalli, S. , Ravindra, U. , & Ravishankar, P. (2018). Effect of processing methods on phytic acid content in selected white finger millet varieties. International Journal of Current Microbiology and Applied Sciences, 7(2), 1829–1835. 10.20546/ijcmas.2018.702.220 [DOI] [Google Scholar]
  34. van Boekel, M. , Fogliano, V. , Pellegrini, N. , Stanton, C. , Scholz, G. , Lalljie, S. , Somoza, V. , Knorr, D. , Jasti, P. R. , & Eisenbrand, G. (2010). A review on the beneficial aspects of food processing. Molecular Nutrition & Food Research, 54(9), 1215–1247. 10.1002/mnfr.200900608 [DOI] [PubMed] [Google Scholar]
  35. Vedamanickam, R. , Anandan, P. , Bupesh, G. , & Vasanth, S. (2020). Study of millet and non‐millet diet on diabetics and associated metabolic syndrome. Biomedicine, 40(1), 55–58. 10.51248/.v40i1.102 [DOI] [Google Scholar]
  36. Wang, L. P. , Wang, X. , Wang, D. Y. , Qi, B. S. , Zheng, S. F. , Liu, H. J. , Luo, C. , Li, H. , Meng, L. , Meng, X. , & Wang, Y. H. (2021). Spatiotemporal changes and driving factors of cultivated soil organic carbon in northern China's typical agro‐pastoral ecotone in the last 30 years. Remote Sensing, 13(18), 18. 10.3390/rs13183607 [DOI] [Google Scholar]
  37. Wang, X. , Cao, Y. , Chen, S. , Lin, J. , Bian, J. , & Huang, D. (2021). Anti‐inflammation activity of flavones and their structure–activity relationship. Journal of Agricultural and Food Chemistry, 69(26), 7285–7302. 10.1021/acs.jafc.1c02015 [DOI] [PubMed] [Google Scholar]
  38. Wu, L. G. , Wang, A. , Shen, R. , & Qu, L. (2021). Effect of heating under pressure treatment on the antioxidant of quinoa. International Journal of Food Engineering, 17(10), 795–804. 10.1515/ijfe-2020-0282 [DOI] [Google Scholar]
  39. Yang, Q. , Zhang, W. , Li, J. , & Feng, B. (2021). Differentiation of fatty acid, aminno acid, and volatile composition in waxy and non‐waxy proso millet. Food Science and Technology, 42, e58320. 10.1590/fst.58320 [DOI] [Google Scholar]
  40. Yang, W. , Lu, X. , Zhang, Y. , & Qiao, Y. (2019). Effect of cooking methods on the health‐promoting compounds, antioxidant activity and nitrate of tatsoi (Brassica rapa L. ssp.narinosa). Journal of Food Processing and Preservation, 43(8), e14008. 10.1111/jfpp.14008 [DOI] [Google Scholar]
  41. Yao, L. , Liu, X. , Jiang, Y. , Caffin, N. , D'Arcy, B. , Singanusong, R. , Datta, N. , & Xu, Y. (2006). Compositional analysis of teas from Australian supermarkets. Food Chemistry, 94(1), 115–122. 10.1016/j.foodchem.2004.11.009 [DOI] [Google Scholar]
  42. Yaqub, G. , Hamid, A. , Khan, N. , Ishfaq, S. , Banzir, A. , & Javed, T. (2020). Biomonitoring of workers exposed to volatile organic compounds associated with different occupations by headspace GC‐FID. Journal of Chemistry, 2020, 1–8. 10.1155/2020/6956402 [DOI] [Google Scholar]
  43. Zhan, L. , Pang, L. , Ma, Y. , & Zhang, C. (2018). Thermal processing affecting phytochemical contents and total antioxidant capacity in broccoli (Brassica oleracea L.). Journal of Food Processing and Preservation, 42(3), e13548. 10.1111/jfpp.13548 [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Articles from Food Science & Nutrition are provided here courtesy of Wiley

RESOURCES