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Article

Study on the Effects of High-Voltage Discharge Plasma Drying on the Volatile Organic Compounds and Texture Characteristics of Oat Grass

by
Mingjie Zhang
1,
Zhiqing Song
1,*,
Bufan Li
2,
Chunxu Qin
1,
Changjiang Ding
1 and
Liqiang Liu
1
1
College of Electric Power, Inner Mongolia University of Technology, Hohhot 010080, China
2
College of Science, Inner Mongolia University of Technology, Hohhot 010051, China
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(5), 468; https://doi.org/10.3390/agriculture15050468
Submission received: 28 January 2025 / Revised: 17 February 2025 / Accepted: 18 February 2025 / Published: 21 February 2025
(This article belongs to the Section Agricultural Technology)
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Versions Notes

Abstract

:
Oat grass is a high-quality forage with exceptional nutritional value and quality. Freshly harvested oat grass requires rapid drying to extend its shelf life. Currently, the primary methods for drying oat grass are natural air drying (AD) and hot air drying (HAD). However, prolonged drying times or elevated temperatures can lead to a degradation in hay quality. To address this issue, in this study, we employed a novel non-thermal drying technology—high-voltage discharge plasma drying (HVDPD)—to dry oat grass. The HVDPD device adopted a multi-needle plate electrode system, with a high-voltage power output of 50 Hz AC and a voltage set to 35 kV. The distance between the needle tip and the plate was set to 10 cm, while the spacing between the needles was adjusted only to three gradients of 2 cm, 8 cm, and 12 cm. To investigate the effects of HVDPD, HAD, and AD on the volatile compounds and textural characteristics of oat grass, in this study, we employed gas chromatography–mass spectrometry (GC-MS) for qualitative and quantitative analyses of the primary volatile components in oat hay. The texture characteristics were determined using texture profile analysis (TPA) and shear testing. A total of 103 volatile substances were detected in oat grass. We categorized them into the following: 28 types of alkanes, 17 types of alkenes, 8 types of esters, 11 types of ketones, 13 types of aldehydes, 20 types of alcohols, and 6 other classes of compounds. We found that the HVDPD group demonstrated significant advantages in enhancing the volatile flavor and palatability of oat grass. The results of the textural properties showed that the structure of oat grass treated with HVDPD was significantly softer, with the 2 cm needle-spacing group exhibiting superior quality and palatability. Overall, this research demonstrates the significant advantages of HVDPD for drying oat grass, providing an important reference for its application in the field of drying technology.

1. Introduction

Oat grass is a relatively high-nutritional-value annual plant belonging to the Poaceae family and the Avena genus [1]. In addition, oat grass serves as premium forage and feed in livestock farming; common forms of forage include green fodder, hay (green dry hay), and silage. Many dairy farms across China primarily utilize oats as green fodder and silage [2]. Oat grass possesses a characteristic sweet flavor that can reduce the likelihood of animals refusing to eat it, effectively increasing both food intake and milk production. This indicates that animals show a marked preference for the soft texture of oat hay, making it one of the best choices among coarse feeds [3]. Consequently, textural properties have become an important quality attribute for oat grass as animal feed, significantly influencing animals’ consumption levels [4]. For instance, hardness, brittleness, and chewability are commonly used indicators of textural characteristics [5,6], which manifest in how palatable animals find oat grass. Resilience refers to the ability of forage to return to its original shape or state after being subjected to external forces [7]; adhesiveness largely depends on combined factors such as adhesion force, cohesion force, and viscosity [8]; and cohesiveness reflects how tightly packed internal structures are within food products.
The headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS) method is commonly employed for the detection of flavors in foods. It integrates the safety, accuracy, and high separation capabilities from both gas chromatography techniques and headspace solid-phase microextraction methods [9], along with mass spectrometry’s superior substance identification abilities, by combining qualitative analysis with retention time data for quantitative assessments [10].
The application of appropriate drying technologies significantly enhances the quality of forage in the following ways: (1) removing moisture—through drying technology, moisture can be effectively removed from forage, thereby extending its shelf life and ensuring both quality and palatability; (2) facilitating storage and transportation—dried forage has a lower moisture content, which helps to reduce costs associated with storage and transportation; (3) improving the nutritional value of forage—during the drying process, the nutritional components in forage can be effectively preserved, while digestibility and absorption rates can also be increased [11]; (4) meeting market demand—as a novel feed ingredient, dried forage is experiencing a continuous increase in demand [12].
Currently, commonly used drying methods for oat grass primarily include natural air drying (AD) and hot air drying (HAD). Natural air drying (AD) is a cost-effective and easily implementable method; however, it carries a higher risk of contamination, which can significantly affect quality. In contrast, while hot air drying (HAD) can reduce drying time and save some costs, it may also lead to the loss of antioxidant compounds [13]. In light of these issues, there is an urgent need to explore novel drying technologies to advance the field. High-voltage discharge plasma drying (HVDPD) technology represents an innovative non-thermal drying approach. This technique utilizes ion wind and electric field forces generated by electrical energy to directly dehydrate and dry wet materials, making it particularly suitable for processing medicinal herbs and forage containing heat-sensitive active components [14]. This unique characteristic of drying at ambient temperature effectively preserves the color, nutritional components, and overall condition of the materials [7]. Additionally, the low equipment cost and operational expenses associated with this technology facilitate its integration into agricultural and industrial production processes, allowing it to play a significant role [15]. For multi-needle-plate HVDPD systems, the effectiveness of the drying process is influenced by various factors, including voltage level, material characteristics, electrode spacing between plates, and needle spacing. Previous studies have indicated that excessively small needle spacings can impede airflow via interference among ion winds, resulting in reduced drying rates; conversely, overly large spacings diminish the effective working area of the needle electrodes, also leading to decreased rates. Therefore, determining the optimal needle spacing is crucial for research on high-voltage discharge plasma drying techniques.
The present study focuses on the use of oat grass as the research subject, employing a “needle-plate” electrode HVDPD technique. Different needle spacings (2 cm, 8 cm, and 12 cm) were established to conduct drying experiments. The objective of this research was to investigate the effects of varying needle spacings on the VOCs and textural properties of oat grass. Additionally, a comparison with traditional drying methods (HAD and AD) was made to reveal the evolution of the flavor and texture quality of oat hay under the influence of high-voltage discharge plasma.

2. Materials and Methods

2.1. Experimental Materials

Whole oat plants were utilized as the experimental material, and experiments were conducted in the natural environment of Inner Mongolia University of Technology (longitude: 111.68246, latitude: 40.84583) in a planting area of 4.8 m2. Manual sowing was carried out at the end of June 2023, and fresh grass was harvested during sunny weather after the oat plants entered their flowering stage. The initial moisture content was measured to be 75% ± 1%.

2.2. Experimental Equipment

(1) Drying Experiment Equipment: This setup primarily comprised a YD(JZ)-1.5/50 model high-voltage power supply, a KZX-1.5 KVA model controller (Wuhan, China), and a multi-needle-plate electrode system. The high-voltage power supply was capable of outputting an alternating current at 50 Hz, while the voltage adjustment range for the controller spanned from 0 to 50 kV AC. The spacing between needles in the multi-needle electrode could be adjusted between 2 cm, 4 cm, 6 cm, 8 cm, 10 cm, and 12 cm, while the HAD oven (DGX-9053, Shanghai, China) had a temperature adjustment range of 10 °C to 250 °C.
(2) Volatile Compound Measurement Equipment: This included a PDMS/DVB headspace solid-phase microextraction device (Agilent Technologies, Santa Clara, CA, USA), a QP2010 ultra gas chromatography–mass spectrometry system (Shimadzu Corporation, Kyoto, Japan), and a CTCPAL automatic sample pre-treatment injector (SSTech AG, Shenzhen, China).
(3) Texture Property Measurement Equipment: This consisted of a TMS-TOUCH physical property tester (FTC Inc., Laredo, TX, USA) along with a TA/LKB lightweight cutting knife probe (Baosheng Instruments Co., Ltd., Shanghai, China)

2.3. Dry Preparation of Oat Grass

HVDPD Experiment Method: The oats were uniformly cut into 5 cm segments from the root to the head, ensuring that each experimental section encompassed various parts of the entire oat plant. A multi-needle-plate electrode system with a controlled voltage level set at 35 kV was employed in the experiments. The distance between the needle tips and the plate was established at 10 cm, while the spacing between needles was variable and set at three gradients: 2 cm, 8 cm, and 12 cm, as shown in Figure 1.
HAD Experimental Method: The treated oat grass was evenly placed in a culture box and then subjected to drying in an oven. The oven temperature was set to 65 °C with an air velocity of 2 m/s.
AD Experimental Method: The treated oat grass was uniformly placed into a culture box and positioned within a constant temperature and humidity chamber. The settings for this chamber were established as a temperature of 24 °C, a relative humidity of 34%, and an air velocity of 0 m/s.
The drying process was considered complete when the dry basis moisture content of the oat grass dropped below 10% and its mass remained relatively stable.

2.4. Extraction of Volatile Organic Compounds

A sample of 3 g was placed into a 20 mL headspace vial and treated using a solid-phase microextraction fiber (DVB/CAR/PDMS, Shanghai, China). The adsorption time was set to 30 min, followed by desorption at 250 °C for 3 min before testing. The aging temperature of the extraction head was maintained at 250 °C for an aging duration of 300 s. The extraction temperature was set to 50 °C with an extraction time of 2400 s, while the stirring speed was adjusted to 300 r/min. After inserting the extraction needle into the gas chromatograph injection port, it was removed following analysis at a condition of 250 °C, after which GC-MS separation and identification were performed.

2.5. Analytical Conditions for Gas Chromatography–Mass Spectrometry

(1) Chromatographic Conditions: A DB-5 ms chromatographic column with dimensions of 30 m × 0.25 mm × 0.25 μm was utilized. The column temperature was set to a programmed increase, beginning at an initial temperature of 60 °C and maintained for 300 s, followed by a rise at a rate of 6 °C/min to 160 °C, which was then held for another 300 s. Subsequently, the temperature increased at a rate of 5 °C/min up to 280 °C and was again maintained for a duration of 300 s.
(2) Mass Spectrometry Conditions: The ion source temperature was set to 230 °C, with a flow rate of 1.4 mL/min. An MSD-type detector was employed, utilizing high-purity helium as the carrier gas at a flow rate of 1.0 mL/min. The sampling method was split injection with a split ratio of 10:1. The purge gas flow rate for the septum was maintained at 3.0 mL/min, and the injector temperature was set to 280 °C, while the scanning range was configured from 45 to 450 m/z.

2.6. Determination and Conditions of Texture Characteristics

After undergoing drying treatment, representative oat grass samples were subjected to comprehensive texture analysis through texture profile analysis (TPA) and shear tests to determine their textural characteristics.
(1)
Selection of Shear Testing Conditions
A lightweight TA/LKB cutting probe was utilized for testing, with a force arm set at 25 kg. The cutting distance was configured as 25 mm, while the pre-test speed and cutting speed were set to 5 mm/s and 10 mm/s, respectively. A sample of rehydrated oat grass weighing 5 mg was taken for the shear test.
(2)
Selection of TPA Measurement Conditions
The probe selected has a cylindrical shape with a diameter of 25.4 mm. The pre-test and post-test speeds were both set to 60 mm/min, with an initial force of 0.06 N and a compression deformation of 60%. The interval time between each measurement was set to 5 s, and the triggering type was configured as automatic triggering. For testing, 5 mg of rehydrated oat grass was used.

2.7. Statistical Analysis

The aforementioned experiments were conducted between 3 and 5 times, and the results were expressed in the form of “mean ± standard deviation” after calculating the average values and standard deviations for each group of data. The analysis of differences among groups was performed using one-way ANOVA via the IBM SPSS Statistics 27 software, with significance levels indicated by p-values; p < 0.05 was considered statistically significant. Data were organized using Microsoft Excel 2010, and all processed data were analyzed and visualized using the Origin 2024 software.

3. Results and Discussion

For the HVDPD group, only the distance between needles varied among different groups. In the HAD group, only the oven temperature was adjusted, with all other conditions maintained consistent with those of the AD group to achieve a controlled variable scenario.
Simultaneously, during this drying experiment, the drying time parameter was consistently monitored. The results indicated that the drying times for needle distances of 2 cm, 8 cm, and 12 cm were 20 h, 25 h, and 34 h, respectively. In contrast, the HAD group and AD group required 39 h and 8 h, respectively. Significant differences in drying time were observed among various drying methods employed in this study.

3.1. Analysis of the Types and Quantities of Volatile Components of Oat Grass After Different Drying Methods

The GC-MS technique integrates the high separation capability of gas chromatography (GC) with the high sensitivity and qualitative abilities of mass spectrometry (MS), enabling the specific detection of certain volatile substances. VOCs are a class of chemicals that easily evaporate at room temperature and can be perceived by the sense of smell; they include alcohols, aldehydes, ketones, esters, and certain sulfur- and nitrogen-containing heterocyclic compounds. The concentrations of these components in food, their odor thresholds, and their interactions with other constituents collectively determine the final flavor profile of food products. Therefore, accurately analyzing the composition and content of VOCs is crucial for understanding food flavor characteristics, optimizing production processes, and improving product formulations. The VOCs of oat grasses that were dried using various drying methods were detected and analyzed utilizing HS-SPME-GC-MS. The total ion chromatogram is presented in Figure 2. A total of 103 VOCs were identified using the GCMSsolution Release 2.10 analysis software. The detected VOCs were classified as 28 alkanes, 17 alkenes, 8 esters, 11 ketones, 13 aldehydes, and 20 alcohols, along with an additional category comprising 6 other types of compounds.
The types and quantities of volatile components in oat grass treated with different drying methods are illustrated in Figure 3. The group treated by HVDPD with 2 cm needle spacing exhibited the highest number of volatile substances, totaling 87 types. These were 24 alkanes, 14 alkenes, 8 esters, 10 ketones, 13 aldehydes, and 13 alcohols, along with 5 other compounds. In contrast, the group treated by HVDPD with 8 cm needle spacing revealed a total of 84 volatile substances, comprising 22 alkanes, 14 alkenes, 7 esters, 10 ketones, 12 aldehydes, 13 alcohols, and 6 other compounds. Furthermore, for the group subjected to HVDPD treatment with needle spacing of 12 cm, a total of only 52 volatile substances were identified, namely, 18 alkanes, 14 alkenes, 4 esters, 5 ketones; 5 aldehydes, 2 alcohols, and 4 other compounds. After undergoing HAD treatment, oat grass was found to consist of a total of 70 types of VOCs. These were 14 alkanes, 12 alkenes, 3 esters, 10 ketones, 13 aldehydes, and 13 alcohols, along with 5 other types of compounds. In contrast, the VOCs present in oat grass subjected to AD treatment amounted to a total of 51 types. These comprised 14 alkanes, 10 alkenes, 8 esters, 3 ketones, 4 aldehydes, and 8 alcohols, as well as 4 other types of compounds. The data presented above clearly indicate that there were significant differences in the volatile components of oat grass treated with various drying methods (p < 0.05). In particular, within the HVDPD experimental group, the quantities of volatile substances in the needle spacing groups of 2 cm and 8 cm showed a marked increase compared with the control group. However, it was observed that in the 12 cm needle spacing group, an excessively large spacing resulted in insufficient ion wind speed; thus, the oat grass’s exposure to high-voltage electric fields (HVEFs) had minimal impact. Consequently, no significant difference was noted between this group and the AD group regarding the quantity of volatile substances.
In a plasma, certain particles and groups can undergo chemical reactions with surrounding substances under appropriate conditions, resulting in the formation of new material structures that alter the physical and chemical properties of the original substances. These particles are referred to as reactive species within the plasma [16,17]. During the HVDPD process, various reactive species such as ozone, hydroxyl radicals, and hydrogen atoms—known for their strong oxidizing properties—are present in the ionic wind. Under the influence of an HVEF, these species are continuously directed towards the surface of oat grass. This interaction may accelerate lipid peroxidation reactions, leading to a significant increase in the production of alcohols and aldehydes among volatile components in samples from the experimental group subjected to HVDPD [18].
Compared with the AD group, the increase in volatile compound content observed in the HAD group can be attributed to the high-temperature environment facilitating reactions between carbonyl compounds (reducing sugars) and amino compounds (amino acids and proteins), known as the Maillard reaction or carbonyl–amino reaction [19]. This process subsequently influences cellular metabolism, leading to alterations in volatile components [20].

3.2. Analysis of Volatile Components of Oat Grass After Treatment with Different Drying Methods

The chart in Figure 4 illustrates the proportions of different volatile components in oat grass after treatment with various drying methods. It can be observed from the figure that alkanes and aldehydes constitute the primary components of volatiles in oat grass, with their combined proportion exceeding 55% across all experimental groups.
(1) Hydrocarbons are a collective term for compounds composed of carbon and hydrogen atoms. Alkenes possess a slight sweetness and exhibit anesthetic properties that can irritate mucous membranes; they can be metabolized into epoxy derivatives that are toxic to genes [21]. As illustrated in Figure 5a, which presents the relative content of alkanes in oat grass under different drying conditions, a total of 12 distinct substances were identified across the five experimental groups. Research has revealed the presence of a significant amount of alkane compounds in plant cell walls, such as cuticular waxes. These substances contribute to the hardness, rigidity, and durability of plant cell walls, thereby providing structural support and protection [22]. The newly synthesized Neophytadiene possesses a fragrant aroma, albeit with relatively strong irritant properties [23]. In contrast, chlorophyll and chlorophyll alcohol emit a greenish odor. During the drying process, as chlorophyll and chlorophyll alcohol are largely converted into Neophytadiene, the greenish smell of tobacco leaves is eliminated, resulting in the emergence of a pleasant fragrance [24]. The analysis revealed that the relative content of newly planted diene in the HVDPD groups at 2 CM, 8 CM, and 12 CM needle spacing was as follows: 1.08 ± 0.28, 0.98 ± 0.35, and 0.82 ± 0.18, respectively. In contrast, the relative contents for the HAD and AD groups were 0.62 ± 0.11 and 0.78 ± 0.14, respectively. The results indicate that the new planting of diene content in the 2 CM and 8 CM needle spacing groups was significantly higher than that in the AD group. In contrast, the 12 CM needle spacing group exhibited negligible effects because of its excessively small inter-needle distance, resulting in no significant difference in relative content compared to the AD group. This suggests that reducing needle spacing in HVDPD enhances the aromatic intensity of oat grass. The application of HAD can enhance the activity of internal oxidative enzyme systems in materials to a certain extent, thereby promoting the oxidation and decomposition of fats, which facilitates the formation of various compounds [25]. However, excessively high temperatures may lead to the gradual degradation of some thermosensitive compounds [26], resulting in a relative decrease in the content of hydrocarbon compounds. There were significant differences (p < 0.01) in the relative content of hydrocarbon compounds in oat grass under different drying conditions.
(2) Research has demonstrated that aldehyde compounds can also be generated through pathways such as lipoxygenase routes and Strecker degradation [27]. The relative content of aldehyde compounds after treatment under different drying conditions is illustrated in Figure 5b. In the experimental group subjected to HVDPD, the relative contents of aldehyde compounds for needle spacings of 2 cm, 8 cm, and 12 cm increased by 27.8%, 28.6%, and 9.8%, respectively. In contrast, the HAD group exhibited a relatively modest increase of only 3.8% in aldehyde compound content. These results indicate that both HVDPD and HAD can enhance the concentration of aldehyde compounds in oat grass. For HAD, the use of an oven set to a temperature of 65 °C accelerates the oxidation reaction process compared with AD via the elevated temperature. This leads to the production of a greater quantity of aldehyde compounds, which aligns with the conclusions drawn by Xu, M.F. regarding the effects of HAD on lipid oxidation in Taihu silver fish [28]. The HVDPD process, as discussed in Section 3.1, generates ion winds that carry highly reactive particles with strong oxidative properties. This phenomenon leads to a rapid lipid oxidation reaction within the oat grass, consequently increasing the relative content of aldehyde compounds. The closer the spacing between the electrodes, the greater the wind speed of the ion flow; hence, more pronounced enhancements were observed in groups with electrode spacings of 2 cm and 8 cm. Therefore, HVDPD proved to be particularly effective in generating various aldehyde compounds [29]. Typical aldehydes produced included benzaldehyde, which is a fatty aldehyde characterized by its resemblance to the fragrance of hyacinths, exhibiting distinct floral notes along with caramel-like undertones [30]. Additionally, there were compounds such as octanal and 2-nonenal; octanal possesses a strong, fruity aroma that, when highly diluted, reveals hints of sweet orange intertwined with subtle fatty honey nuances. For its part, 2-nonenal is a typical product of lipid oxidation reactions and is classified as an unsaturated aldehyde. It is often used as an indicator for lipid oxidation processes [31]. Significant differences (p < 0.05) were observed in the relative content of aldehyde compounds in oat grass after treatment with HVDPD at varying electrode spacings.
(3) The ester compounds produced from oat grass treated with HVDPD included diisobutyl phthalate and 2-methylpropanoic acid 3-hydroxy-2,2,4-trimethylpentyl ester. Between these, diisobutyl phthalate exhibits excellent adhesive properties while also enhancing the resilience of the oat grass. As shown in Figure 5c, the relative contents of ketones, esters, alcohols, and several other compounds in oat grass were analyzed after treatment with different drying methods. In the HVDPD group, the relative content of aldehyde compounds increased by 2.9% and 1.7% for needle spacings of 2 cm and 8 cm, respectively. This study indicates that prolonged exposure to sunlight and high temperatures during AD and HAD adversely affected the volatilization of ester compounds [32].
(4) For ketone compounds, the ketonic substances generated through drying experiments mainly included 2,3-octanedione, 6-methyl-5-hepten-2-one, and 3-octen-2-one. Among these, both 2,3-octanedione and 6-methyl-5-hepten-2-one exhibit a fresh aroma reminiscent of citrus fruits with green notes [33]. In contrast, 3-octen-2-one is naturally found in roasted hazelnuts and baked potatoes, imparting an earthy scent. After HVDPD treatment, the experimental groups with needle spacings of 2 cm and 8 cm showed relative increases in ketone compounds of 3.6% and 5.4%, respectively. The HAD group experienced a decrease of 2.5% in the relative content of ketone compounds. The differences in the relative contents of ketones and esters from oat grass under various drying conditions were found to be significant (p < 0.05).
(5) Alcohol compounds can be produced through various biological processes in nature, including fermentation, photosynthesis, and metabolism. Additionally, they may result from lipid oxidation and the enzymatic degradation of unsaturated fatty acids [34]. As shown in Figure 5c, the relative content of alcohol compounds was found to be highest in the AD group. The lowercase letters in the figure represent significance analysis. This phenomenon may be attributed to the prolonged exposure of this group to air, which facilitates lipid oxidation. Furthermore, the presence of microorganisms in the natural environment can easily contaminate oat grass, leading to fermentation that ultimately results in a significant increase in the relative content of alcohol compounds. The HVDPD process primarily accelerates the oxidation reactions of lipids in oat grass because of the presence of active particles such as hydroxyl and ozone, thereby increasing the content of alcohol. In contrast, the HAD group exhibited the lowest relative content of alcoholic compounds. This may be attributed to a certain degree of volatilization and esterification that occurred during the thermal treatment of the oat grass [35].
The compounds generated primarily originate from the Maillard reaction and pyrolysis [36]. Notably, among these compounds was 2-pentylfuran. Furan derivatives exhibit a range of aromatic profiles, including bean-like, fruity, earthy, green, and vegetable-like notes [37]. Phenol exerts a significant influence on various aspects of plant growth, nutrient absorption, physiological characteristics, enzyme activity, and the surrounding environment, including soil and microorganisms. Research has shown that 2,4-di-tert-butylphenol is a common toxic secondary metabolite produced by diverse biological communities. It can inhibit growth by altering the activity of biological enzymes, demonstrating strong toxicity against nearly all tested organisms, including producers [38]. Through analysis, it was observed that the relative content of 2,4-di-tert-butylphenol in oat grass treated with HVDPD exhibited a significant decreasing trend. This raises questions regarding whether HVDPD enhances disease resistance in forage crops, thereby providing valuable insights for future research on HVDPD technology.

3.3. Specific Analysis of Volatile Components of Oat Grass Under Different Drying Methods

To further elucidate the effects of different drying methods on the VOCs in oat grass, OPLS-DA (orthogonal partial least squares–discriminant analysis) was employed as a multivariate analytical approach to construct a quantitative correlation model between drying methods and volatile substances. OPLS-DA is particularly suited for distinguishing differences among multiple samples and represents a regression analysis method based on orthogonal signal correction [39]. As illustrated in Figure 6a, it is evident that the samples of oat grass exhibited distinct regional distribution characteristics under different parameters. R x 2 = 0.992 > 0.5 , Q 2 = 0.961 > 0.5 indicate that the model demonstrated commendable fitting accuracy and predictive capability. The OPLS-DA score plot obtained demonstrates the clustering of five different drying methods. It can be observed that the groups with needle spacings of 2 cm and 8 cm are located in the fourth quadrant, while the group with a needle spacing of 12 cm and the AD group are situated in the second quadrant. The HAD group is found in the third quadrant. Theoretically, the group with a needle spacing of 12 cm should fall within the HVDPD region, appearing in the first quadrant. However, the 12 cm needle spacing group was in the same quadrant as the AD group, for the reasons described in Section 3.1 above. The dispersion plot for OPLS-DA indicates good clustering among all five sample groups, revealing minor differences between them while achieving complete separation among different samples.
The results of the permutation test are illustrated in Figure 6b. Through 200 iterations of the permutation test, it was observed that the Q 2 regression line intersects the vertical axis in the negative half-plane. Additionally, both R 2 and the true values on the right side of Q 2 exceed those predicted on the left side. This indicates that there was no overfitting present in this model [40]. Therefore, the OPLS-DA model established was stable and reliable, making it suitable for the discriminative analysis of oatgrass under varying drying conditions, thereby possessing certain statistical significance.
The VIP value reflects the extent to which different substances contribute to the differential classification of models. Thresholds of p < 0.05 and VIP > 1 were established as the criterion for selecting differential substances [41]. The results of the VIP values for various volatile components are presented in Figure 6c and summarized in Table 1. A total of 15 compounds exhibited VIP values greater than 1.

3.4. Analysis of the Effects of Different Drying Methods on the Texture Characteristics of Oat Grass

Texture profile analysis and shear force tests can effectively reflect the internal organizational structure and variation patterns of oat grass to a certain extent. The radar chart illustrated in Figure 7 depicts the trends of various texture characteristic indicators under different drying methods. It is evident from the figure that oat grass in the 2 cm needle spacing group exhibited superior textural properties.
(1) Hardness is defined as the maximum force required to cut a sample, which is closely related to the organizational structure of the sample. It is one of the most important indicators for evaluating the palatability of forage [42]. As shown in Figure 8, the figure indicates that group ‘a’ represents the highest average relative content of VOCs in oat grass, while group ‘d’ corresponds to the lowest average value. Identical letters denote no significant differences, whereas different letters indicate statistically significant differences. All experimental groups exhibited hardness values lower than that of the AD group (p < 0.01). The lowercase letters in the figure represent significance analysis. Among them, the group with a needle spacing of 2 cm recorded the lowest hardness value at 5.14 ± 0.07. Furthermore, as the needle spacing decreased, there was a corresponding reduction in hardness values, indicating that less force is required for chewing. At this point, oat grass demonstrated improved palatability. The oat grass retained its tissue structure to a significant extent after being treated with HVDPD, resulting in hardness values that were all lower than those of the AD group. This finding aligns with the results obtained by Zhang, J. et al. in their experimental research on yam [7]. The heat-treated oat grass demonstrated a stronger ability to resist damage and maintain integrity; therefore, when compared with the AD group, the HAD group exhibited lower hardness values. This observation is consistent with the findings of Zhu et al. regarding the textural characteristics of apple slices [43].
(2) Elasticity, an important indicator of the textural characteristics of oat grass, refers to the material’s ability to return to its original shape after undergoing deformation due to external forces. The drying process results in a lower moisture content and water activity value for oat grass; thus, compared with AD samples, the HVDPD group oat grass exhibited smaller pore sizes and reduced elasticity [44]. This observation was particularly pronounced in the 2 CM needle spacing group and the HAD group. The 2 CM needle spacing group exhibited the highest ionic wind velocity among all experimental groups subjected to HVDPD, while the HAD group underwent thermal treatment at elevated temperatures. Both drying methods significantly reduced the moisture content of the samples, resulting in lower elasticity for both experimental groups (p < 0.05).
(3) Brittleness refers to the property of a material that exhibits minimal deformation before fracture under external forces such as tension or impact. It is characterized by the magnitude of force required for the initial breakage, which is considered to represent the height of the first peak [45]. The variation in brittleness is illustrated in Figure 8. The internal texture characteristics of the oat grass prepared by these three drying methods were generally similar (p > 0.05). However, it was observed that the deformation and cracking of oat grass may be attributed to the hardening that occurs during the later stages of drying, which makes it difficult for internal moisture to be removed, necessitating the application of greater force. As the drying time extends, the internal moisture gradually diffuses and evaporates, leading to a progressive reduction in brittleness. In contrast, oat grass treated with high-pressure discharge plasma exhibited a porous internal structure that facilitates the migration and diffusion of internal moisture and is preserved during this process. Consequently, compared with conventional HAD methods, this approach enables oat grass to demonstrate brittleness at an earlier stage and results in significantly lower brittleness values than those achieved through traditional methods. This research indicates that lower brittleness values suggest a more crisp texture for the material [46].
(4) Cohesiveness is defined as the strength of the bonds within the material’s structure [47]. In texture profile analysis (TPA) experiments, it is quantified as the ratio of the area under the second compression curve to that of the first compression area. The results presented in Figure 8 indicate that the values of the five experimental groups were closely aligned (p > 0.05). The adhesion properties of oat grass under different drying conditions improved at longer drying times, approaching zero. Initially, because of its high moisture content, fresh oat grass exhibits a relatively high level of adhesion. However, as the drying process progresses and moisture content decreases, the adhesion properties of oat grass continuously decline. In the later stages of drying, the loss of surface moisture leads to a gradual disappearance of its adhesive qualities. It is noteworthy that in the HAD group, for which significantly shorter drying times were utilized, there was a marked increase in adhesion values—1.54 times higher compared with the AD group.
(5) Adhesive properties refer to the characteristics of food materials that exhibit both elasticity and viscosity when subjected to force. This property represents the energy required to separate the food from its contact materials [48]. As shown in Figure 9, the adhesive properties of the HAD group were significantly higher than those of the AD group. This discrepancy can be attributed to the very low viscosity index of the oat grass in the AD group, which was primarily influenced by its high moisture content contributing to its adhesiveness. As temperature increases, the viscosity index also rises, indicating that removing moisture at elevated drying temperatures leads to a more substantial increase in viscosity within the oat grass tissue [49]. The differences in adhesiveness among oat grasses treated with different drying methods were highly significant (p < 0.01).
(6) Chewiness serves as a crucial indicator for assessing the quality value of materials, representing a comprehensive manifestation of hardness, elasticity, and cohesiveness [50]. As illustrated in Figure 9, asterisks are used to denote significant differences: * indicates a significance level of p < 0.05, while ** signifies highly significant differences at p < 0.01. The chewability of the samples, ranked from highest to lowest, was as follows: 12 cm needle spacing group > AD group > HAD group >8 cm needle spacing group >2 cm needle spacing group. After undergoing drying treatment, the palatability of the forage was improved to a certain extent across all groups; notably, the changes observed in the HVDPD-treated oat grass were most pronounced (p < 0.05). A moderate increase in temperature shows a positive effect on the chewability of oat grass. Research conducted by Ding et al. on the chewing characteristics of sliced jujube yielded similar conclusions [51].
(7) The maximum shear force refers to the highest level of force that a material can withstand during the shear testing process [47]. In this study, the AD group of oat grass exhibited a peak shear force of 6.42 ± 0.18, while the group subjected to HVDPD treatment with a needle spacing of 2 cm recorded a minimum value of 5.04 ± 0.14. There were significant differences in the maximum shear force values among oat grass treated by different drying methods (p < 0.05).

3.5. Principal Component Analysis

Principal component analysis (PCA) is a multivariate statistical analysis conducted in an unsupervised mode [52]. In this analysis, we utilized 103 VOCs and seven texture indicators as dependent variables, while five different drying methods served as independent variables for the PCA of oat grass under various drying conditions. The results are illustrated in Figure 10. The variance contribution rates of the first principal component (PC1) and the second principal component (PC2) reached 89.5%, indicating that these two components encompassed the majority of the information. The contribution rate of the first principal component to the variance was 44.3%, primarily reflecting hardness and brittleness; the contribution rate of the second principal component was 45.2%, mainly indicating elasticity and alkane compounds. This suggests that the model was suitable for analyzing the volatile components and textural characteristics of oat grass subjected to different drying methods. The analysis revealed distinct differences in the compounds and characteristics of oat grass subjected to various drying methods. There were notable discrepancies in the impact of different drying methods on the VOCs and textural properties of oat grass.

3.6. Correlation Analysis

The heatmap illustrated in Figure 11a presents a correlation analysis among the VOCs, texture characteristics, and drying methods of oat grass after it underwent different drying treatments. The sizes of the circles in the figure represent the magnitude of the correlation, and this magnitude is also indicated in the lower-left corner of the graph. The upper-right corner denotes significance using asterisks. A deeper yellow indicates a stronger positive correlation between the two variables, while a bluer hue signifies a stronger negative correlation. For the texture characteristics of hardness, chewiness, elasticity, and maximum shear force, the group with a 2 cm needle spacing exhibited a significantly high negative correlation index. In contrast, the negative correlation level in the 8 cm needle spacing group was reduced, while the 12 cm group demonstrated a positive correlation. This indicates that as the needle spacing decreases, oat grass becomes softer and more palatable. Therefore, it can be concluded that HVDPD significantly enhances the palatability of oat grass. These observations indicate that the groups with 2 cm and 8 cm needle spacing exhibited strong positive correlations with both 2-hexenal and hexanal compounds. Additionally, cohesiveness showed a significant negative correlation across all three experimental groups of HVDPD. The HAD group demonstrated a robust positive correlation (0.99) with brittleness, suggesting that oat grass becomes increasingly brittle after high-temperature thermal treatment.
The Pearson correlation coefficient matrix presented in Figure 11b highlights the relationships among various drying methods, specific compounds, and texture characteristic indicators. Asterisks are used to denote significant differences: * indicates a significance level of p < 0.05, while ** signifies highly significant differences at p < 0.01. In the analysis, a highly significant positive correlation (0.99) was found between 3,5,5-trimethyl-2-Hexene and cohesiveness. Conversely, Decanal exhibited a strong negative correlation index (−0.97) with brittleness. This suggests that the production of these two compounds is a primary factor contributing to the crispiness of oat grass to some extent. β-Ionone exhibited positive correlations with both 2-hexenal and Phenylacetaldehyde. Additionally, the compound Hexahydrofarnesyl Acetone demonstrated strong negative correlations with hardness, elasticity, and maximum shear force. The presence of this compound may contribute to making oat grass more palatable and flavorful. Furthermore, as the spacing between needles decreased, the positive correlations between these two compounds gradually increased. In summary, the treatment of oat grass with HVDPD has led to notable improvements in both taste and quality. Furthermore, the smaller the spacing between needles, the more pronounced this effect became.

4. Conclusions

In this study, we analyzed and compared the VOCs and texture characteristics of oat grass under three different drying methods (HVDPD, HAD, and AD). The results indicate that the oat grass treated with HVDPD exhibited the highest quantity of VOCs. Specifically, in groups with inter-needle distances of 2 CM, 8 CM, and 12 CM, the numbers of identified compounds reached 87, 84, and 52, respectively. At the same time, the advantages of low-temperature drying enable the HVDPD method to play a positive role in enhancing both the quality and palatability of oat grass. The oat grass treated with HVDPD exhibited superior texture characteristics. In the group with 2 cm needle spacing, hardness, chewiness, and maximum shear force were all at a minimum. This indicates that at this point, the biting force and chewing energy required for digesting oat grass are minimized. The research findings indicate that the volatile compounds in oat grass significantly increased after HVDPD treatment. Specifically, there were increases in 12 types of alkanes, 7 types of ketones, 10 types of aldehydes, and 4 types of phenolic compounds. Regarding textural characteristics, the hardness and brittleness of oat grass decreased significantly following HVDPD treatment, suggesting that the treated oat grass was softer. The reduction in chewiness indicates that the oat grass possessed superior taste and quality. In summary, these research findings contribute to the advancement of non-thermal processing technologies—high-voltage discharge plasma drying techniques—in forage processing and modulation applications. They provide a theoretical foundation and experimental validation for enhancing the quality of forage products and lay a solid groundwork for the future development and commercialization of HVDPD technology.

Author Contributions

M.Z., conceptualization, methodology, investigation, formal analysis, and writing—original draft; Z.S., data curation and funding acquisition; B.L., visualization and investigation; C.Q., supervision; C.D. and L.L., validation and visualization. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundations of China (Nos. 12265021 and 12365023), the Program for Young Talents of Science and Technology in Universities of the Inner Mongolia Autonomous Region (No. NJYT23108), the Natural Science Foundation of Inner Mongolia (2024MS01001), and the Basic Scientific Research Business Project of the Universities Directly of the Inner Mongolia Autonomous Region (Nos. JY20220057 and JY20240068).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Zhang, D.; Zhang, Y.; Pan, X.; Yuan, L.; Cai, Y.; Lao, F.; Wu, J. Effect of extrusion on the structural and flavor properties of oat flours. J. Cereal Sci. 2023, 113, 103742. [Google Scholar] [CrossRef]
  2. Räisänen, S.E.; Sigurðardóttir, P.H.; Halmemies-Beauchet-Filleau, A.; Pitkänen, O.; Vanhatalo, A.; Sairanen, A.; Kokkonen, T. Ruminal methane emission and lactational performance of cows fed rapeseed cake and oats on a grass silage–based diet. J. Dairy Sci. 2024, 107, 6732–6741. [Google Scholar] [CrossRef] [PubMed]
  3. Vanhatalo, A.; Gäddnäs, T.; Heikkilä, T. Microbial protein synthesis, digestion and lactation responses of cows to grass or grass-red clover silage diet supplemented with barley or oats. Agric. Food Sci. 2006, 15, 252–267. [Google Scholar] [CrossRef]
  4. Kethireddipalli, P.; Hung, Y.C.; McWatters, K.H.; Phillips, R.D. Effect of milling method (wet and dry) on the functional properties of cowpea (Vigna unguiculata) pastes and end product (akara) quality. J. Food Sci. 2002, 67, 48–52. [Google Scholar] [CrossRef]
  5. Lin, W.L.; Yang, X.Q.; Li, L.H.; Hao, S.X.; Wang, J.X.; Huang, H.; Wei, Y.; Wu, Y.Y. Effect of Ultrastructure on Changes of Textural Characteristics between Crisp Grass Carp (Ctenopharyngodon Idellus C.Et V) and Grass Carp (Ctenopharyngodon Idellus) Inducing Heating Treatment. J. Food Sci. 2016, 81, E404–E411. [Google Scholar] [CrossRef]
  6. Deng, L.Z.; Mujumdar, A.S.; Yang, X.H.; Wang, J.; Zhang, Q.; Zheng, Z.A.; Gao, Z.J.; Xiao, H.W. High humidity hot air impingement blanching (HHAIB) enhances drying rate and softens texture of apricot via cell wall pectin polysaccharides degradation and ultrastructure modification. Food Chem. 2018, 261, 292–300. [Google Scholar] [CrossRef]
  7. Zhang, J.; Ding, C.; Lu, J.; Zhu, J.; Bai, W.; Guan, P.; Song, Z.; Chen, H. Effect of electrohydrodynamic (EHD) drying on active ingredients, textural properties and moisture distribution of yam (Dioscorea opposita). Food Chem. X 2024, 23, 101622. [Google Scholar] [CrossRef]
  8. Adhikari, B.; Howes, T.; Bhandari, B.R.; Truong, V. Stickiness in foods: A review of mechanisms and test methods. Int. J. Food Prop. 2001, 4, 1–33. [Google Scholar] [CrossRef]
  9. Huang, T.; Sun, Y.; Guo, Y.; Wang, W.; He, T.; Cao, J. Application of HS-SPME-GC-MS combined with electronic nose technology in the odor recognition of pseudostellariae radix. Nat. Prod. Res. 2023, 37, 2457–2460. [Google Scholar] [CrossRef]
  10. Villière, A.; Symoneaux, R.; Roche, A.; Eslami, A.; Perrot, N.; Le Fur, Y.; Prost, C.; Courcoux, P.; Vigneau, E.; Thomas-Danguin, T.; et al. Comprehensive sensory and chemical data on the flavor of 16 red wines from two varieties: Sensory descriptive analysis, HS-SPME-GC-MS volatile compounds quantitative analysis, and odor-active compounds identification by HS-SPME-GC-MS-O. Data Brief 2019, 24, 103725. [Google Scholar] [CrossRef]
  11. Hu, W.; Song, Z.; Ma, Q.; Li, B.; Zhang, M.; Ding, C.; Chen, H.; Zhao, S. Study on the Drying Characteristics and Physicochemical Properties of Alfalfa under High-Voltage Discharge Plasma. Agriculture 2024, 14, 1134. [Google Scholar] [CrossRef]
  12. Ouédraogo, A.; Zampaligré, N.; Mulubrhan, B.; Adesogan, A.T. Assessment of peri-urban livestock producers’ willingness to pay for improved forages as cash crops. Agron. J. 2022, 114, 63–74. [Google Scholar] [CrossRef] [PubMed]
  13. Vidinamo, F.; Fawzia, S.; Karim, M.A. Effect of drying methods and storage with agro-ecological conditions on phytochemicals and antioxidant activity of fruits: A review. Crit. Rev. Food Sci. Nutr. 2022, 62, 353–361. [Google Scholar] [CrossRef] [PubMed]
  14. Ham, J.C.A.; Alawi, A.; Rizki, Z.; Boom, R.M.; Garbin, V.; Padding, J.T.; Schutyser, M.A.I. A multi-scale analysis on electrohydrodynamic drying technology for bio-based & food products. Trends Food Sci. Technol. 2024, 151, 104634. [Google Scholar] [CrossRef]
  15. Dalvand, M.J.; Mohtasebi, S.S.; Rafiee, S. Optimization on drying conditions of a solar electrohydrodynamic drying system based on desirability concept. Food Sci. Nutr. 2014, 2, 758–767. [Google Scholar] [CrossRef]
  16. Arkar, K.; Vasiliev, M.M.; Petrov, O.F.; Kononov, E.A.; Trukhachev, F.M. Dynamics of Active Brownian Particles in Plasma. Molecules 2021, 26, 256. [Google Scholar] [CrossRef]
  17. Cheng, J.-H.; Wang, H.; Sun, D.-W. Insight into the IgE-binding sites of allergenic peptides of tropomyosin in shrimp (Penaeus chinensis) induced by cold plasma active particles. Int. J. Biol. Macromol. 2023, 234, 123690. [Google Scholar] [CrossRef]
  18. Prasad, C.T.M.; Kodde, J.; Angenent, G.C.; de Vos, R.C.H.; Diez-Simon, C.; Mumm, R.; Hay, F.R.; Siricharoen, S.; Yadava, D.K.; Groot, S.P.C. Experimental rice seed aging under elevated oxygen pressure: Methodology and mechanism. Front. Plant Sci. 2022, 13, 1050411. [Google Scholar] [CrossRef]
  19. Xu, X.; Ma, C.; Yang, Y.; Bian, X.; Wang, B.; Zhang, G.; Zhang, N. Effects of phytic acid from soybean meal on Maillard reaction and antioxidant properties of products. Food Chem. 2025, 463, 141257. [Google Scholar] [CrossRef]
  20. Zhao, R.; Xiao, H.; Liu, C.; Wang, H.; Wu, Y.; Ben, A.; Wang, Y. Dynamic changes in volatile and non-volatile flavor compounds in lemon flavedo during freeze-drying and hot-air drying. LWT 2023, 175, 114510. [Google Scholar] [CrossRef]
  21. Gonsowski, C.T.; Laster, M.J.; Eger, E.I.; Ferrell, L.D.; Kerschmann, R.L. Toxicity of compound-a in rats—Effect of increasing duration of administration. Anesthesiology 1994, 80, 566–573. [Google Scholar] [CrossRef] [PubMed]
  22. Macnee, N.C.; Rebstock, R.; Hallett, I.C.; Schaffer, R.J.; Bulley, S.M. A review of current knowledge about the formation of native peridermal exocarp in fruit. Funct. Plant Biol. 2020, 47, 1019–1031. [Google Scholar] [CrossRef]
  23. Yan, L.; Zhang, A.; Qin, X.; Yu, H.; Ji, X.; He, S.; Zong, Y.; Gu, C.; Feng, Z.; Hu, L.; et al. Changes in key volatile components associated with leaf quality of Pandanus amaryllifolius Roxb. alongside growth duration. Food Chem. X 2025, 25, 102–126. [Google Scholar] [CrossRef]
  24. Wu, Y.; Zhang, H.; Wang, W.; Kong, G.; Li, Z.; Zhang, T.; Wang, M.; Yang, D.; Zhang, C.; Li, Y.; et al. Characterization of Volatile Organic Compounds and Aroma Sensory Properties in Yunnan Cigar. J. Anal. Methods Chem. 2024, 2024, 9583022. [Google Scholar] [CrossRef]
  25. Yang, H.; Li, W.; Lu, B.; Zi, L.; Xu, N.; Guo, L. Effect of different hot air drying process on flavor compounds and Maillard reaction products of Boletus edulis by HS-SPME/GC-MS coupled with multivariate analysis. LWT 2024, 198, 116055. [Google Scholar] [CrossRef]
  26. Huang, Y.; Wang, X.; Lyu, Y.; Li, Y.; He, R.; Chen, H. Metabolomics analysis reveals the non-enzymatic browning mechanism of green peppers (Piper nigrum L.) during the hot-air drying process. Food Chem. 2025, 464, 141654. [Google Scholar] [CrossRef]
  27. Zamora, R.; Gallardo, E.; Hidalgo, F.J. Strecker Degradation of Phenylalanine Initiated by 2,4-Decadienal or Methyl 13-Oxooctadeca-9,11-dienoate in Model Systems. J. Agric. Food Chem. 2007, 55, 1308–1314. [Google Scholar] [CrossRef]
  28. Xu, M.; Liu, Q.; Ni, X.; Chen, C.; Deng, X.; Fang, Y.; Wang, X.; Shen, Q.; Yu, R. Lipidomics reveals the effect of hot-air drying on the quality characteristics and lipid oxidation of Tai Lake whitebait (Neosalanx taihuensis Chen). LWT 2024, 197, 115942. [Google Scholar] [CrossRef]
  29. Ni, J.-B.; Bi, Y.-X.; Vidyarthi, S.K.; Xiao, H.-W.; Han, L.-D.; Wang, J.; Fang, X.-M. Non-thermal electrohydrodynamic (EHD) drying improved the volatile organic compounds of lotus bee pollen via HS-GC-IMS and HS-SPME-GC-MS. LWT 2023, 176, 114480. [Google Scholar] [CrossRef]
  30. Ma, L.; Gao, M.; Zhang, L.; Qiao, Y.; Li, J.; Du, L.; Zhang, H.; Wang, H. Characterization of the key aroma-active compounds in high-grade Dianhong tea using GC-MS and GC-O combined with sensory-directed flavor analysis. Food Chem. 2022, 378, 132058. [Google Scholar] [CrossRef]
  31. Zamora, R.; Alcón, E.; Hidalgo, F.J. Strecker-Type Degradation of Phenylalanine Initiated by 4-Oxo-2-alkenals in Comparison to That Initiated by 2,4-Alkadienals, 4,5-Epoxy-2-alkenals, or 4-Hydroxy-2-nonenal. J. Agric. Food Chem. 2013, 61, 10231–10237. [Google Scholar] [CrossRef] [PubMed]
  32. Zhang, J.; Ding, C.; Lu, J.; Wang, H.; Bao, Y.; Han, B.; Zhu, J.; Duan, S.; Song, Z.; Chen, H. Effects of electrohydrodynamics on drying characteristics and volatile profiles of goji berry (Lycium barbarum L.). LWT 2024, 200, 116–149. [Google Scholar] [CrossRef]
  33. Yu, W.; Wei, Y.; Long, F.; Zhao, S.; Xiao, Y.; Gao, H. Insights into the dynamic evolution of quality and sensory attributes in red aril wine during fermentation. LWT 2024, 203, 116382. [Google Scholar] [CrossRef]
  34. Huang, Q.; Dong, K.; Wang, Q.; Huang, X.; Wang, G.; An, F.; Luo, Z.; Luo, P. Changes in volatile flavor of yak meat during oxidation based on multi-omics. Food Chem. 2022, 371, 103–131. [Google Scholar] [CrossRef]
  35. Guo, Y.; Chen, D.; Dong, Y.; Ju, H.; Wu, C.; Lin, S. Characteristic volatiles fingerprints and changes of volatile compounds in fresh and dried Tricholoma matsutake Singer by HS-GC-IMS and HS-SPME-GC–MS. J. Chromatogr. B 2018, 1099, 46–55. [Google Scholar] [CrossRef]
  36. Zhang, L.; Chen, Q.; Liu, Q.; Xia, X.F.; Wang, Y.; Kong, B.H. Effect of different types of smoking materials on the flavor, heterocyclic aromatic amines, and sensory property of smoked chicken drumsticks. Food Chem. 2022, 367, 130680. [Google Scholar] [CrossRef]
  37. Wall, K.R.; Kerth, C.R.; Miller, R.K.; Alvarado, C. Grilling temperature effects on tenderness, juiciness, flavor and volatile aroma compounds of aged ribeye, strip loin, and top sirloin steaks. Meat Sci. 2019, 150, 141–148. [Google Scholar] [CrossRef]
  38. Zhao, F.; Wang, P.; Lucardi, R.D.; Su, Z.; Li, S. Natural Sources and Bioactivities of 2,4-Di-Tert-Butylphenol and Its Analogs. Toxins 2020, 12, 35. [Google Scholar] [CrossRef]
  39. Liu, M.; Yang, Y.; Zhao, X.; Wang, Y.; Li, M.; Wang, Y.; Tian, M.; Zhou, J. Classification and characterization on sorghums based on HS-GC-IMS combined with OPLS-DA and GA-PLS. Curr. Res. Food Sci. 2024, 8, 100692. [Google Scholar] [CrossRef]
  40. Chung, I.-M.; Kim, J.-K.; Han, J.-G.; Kong, W.-S.; Kim, S.-Y.; Yang, Y.-J.; An, Y.-J.; Kwon, C.; Chi, H.-Y.; Yhung Jung, M.; et al. Potential geo-discriminative tools to trace the origins of the dried slices of shiitake (Lentinula edodes) using stable isotope ratios and OPLS-DA. Food Chem. 2019, 295, 505–513. [Google Scholar] [CrossRef]
  41. Zhou, Y.; Wang, D.; Zhao, J.; Guo, Y.; Yan, W. Differentiation and characterization of volatile compounds in five common milk powders using HS-GC-IMS, HS-SPME-GC–MS, and multivariate statistical approaches. Food Chem. X 2025, 25, 102–179. [Google Scholar] [CrossRef] [PubMed]
  42. Kang, S.I.; Kim, M.W.; Kim, Y.J.; Kim, M.J.; Choi, B.D.; Heu, M.S.; Kim, J.S. Processing optimization of restructured jerky from sea rainbow trout frame muscle. Food Sci. Biotechnol. 2016, 25, 707–712. [Google Scholar] [CrossRef]
  43. Zhu, J.; Liu, Y.; Zhu, C.; Wei, M. Effects of different drying methods on the physical properties and sensory characteristics of apple chip snacks. LWT 2022, 154, 112829. [Google Scholar] [CrossRef]
  44. Elmas, F.; Bodruk, A.; Köprüalan, Ö.; Arıkaya, Ş.; Koca, N.; Serdaroğlu, F.M.; Kaymak-Ertekin, F.; Koç, M. The effect of pre-drying methods on physicochemical, textural and sensory characteristics on puff dried Turkey breast meat. LWT 2021, 145, 111350. [Google Scholar] [CrossRef]
  45. Qu, C.; Wang, X.; Wang, Z.; Yu, S.; Wang, D. Effect of Drying Temperatures on the Peanut Quality during Hot Air Drying. J. Oleo Sci. 2020, 69, 403–412. [Google Scholar] [CrossRef]
  46. Liu, C.; Zheng, X.; Jia, S.; Ding, N.; Gao, X. Comparative Experiment on Hot-Air and Microwave-Vacuum Drying and Puffing of Blue Honeysuckle Snack. Int. J. Food Eng. 2009, 5, 16–83. [Google Scholar] [CrossRef]
  47. Terpstra, M.E.J.; Jellema, R.H.; Janssen, A.M.; de Wijk, R.A.; Prinz, J.F.; van der Linden, E. Prediction of texture perception of mayonnaises from rheological and novel instrumental measurements. J. Texture Stud. 2009, 40, 82–108. [Google Scholar] [CrossRef]
  48. Xu, W.; Zhang, F.; Wang, J.; Ma, Q.; Sun, J.; Tang, Y.; Wang, J.; Wang, W. Real-Time Monitoring of the Quality Changes in Shrimp (Penaeus vannamei) with Hyperspectral Imaging Technology during Hot Air Drying. Foods 2022, 11, 3179. [Google Scholar] [CrossRef]
  49. Wang, H.; Liu, C.; Xue, Y.; Li, D. Correlation of mechanical properties of peach slices with cell wall polysaccharides and cell morphology during hot air predrying. J. Food Process. Preserv. 2019, 44, 14319. [Google Scholar] [CrossRef]
  50. Shrivastav, S.; Kumbhar, B.K. Textural profile analysis of paneer dried with low pressure superheated steam. J. Food Sci. Technol. 2010, 47, 10–59. [Google Scholar] [CrossRef]
  51. Ding, H.; Yang, C.; Cao, S.; Gu, J.; Li, Y.; Zang, Y.; Yao, X.; Zhu, R.; Wang, Q.; Dong, W.; et al. Prediction models of texture attributes for radiofrequency assisted hot air drying of jujube slices based on morphological parameters. LWT 2023, 190, 115527. [Google Scholar] [CrossRef]
  52. Wang, D.; Chen, X.; Pandiselvam, R.; Wang, Y.; Zhao, W.; Li, F.; Sun, X.; Guo, Y.; Su, D.; Xu, H. Effects of microwave power control on enzyme activity, drying kinetics, and typical nutrients of Pleurotus Eryngii: Exploring the blanching mechanism by microstructural and ultrastructural evaluation. J. Food Compos. Anal. 2024, 128, 106037. [Google Scholar] [CrossRef]
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Figure 1. Schematic diagram of HVDPD experimental setup.
Figure 1. Schematic diagram of HVDPD experimental setup.
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Figure 2. Total ion chromatogram of oat grass volatile substances. Note: 2 CM: HVDPD group with 2 cm needle spacing; 8 CM: HVDPD group with 8 cm needle spacing; 12 CM: HVDPD group with 12 cm needle spacing; HAD: hot air drying group; AD: natural air drying group.
Figure 2. Total ion chromatogram of oat grass volatile substances. Note: 2 CM: HVDPD group with 2 cm needle spacing; 8 CM: HVDPD group with 8 cm needle spacing; 12 CM: HVDPD group with 12 cm needle spacing; HAD: hot air drying group; AD: natural air drying group.
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Figure 3. Numbers of volatile components of oat grass under different drying conditions.
Figure 3. Numbers of volatile components of oat grass under different drying conditions.
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Figure 4. The proportions of volatile components in oat green hay under various drying conditions: (a) 2 CM needle spacing group; (b) 8 CM needle spacing group; (c) 12 CM needle spacing group; (d) HAD group; (e) AD group.
Figure 4. The proportions of volatile components in oat green hay under various drying conditions: (a) 2 CM needle spacing group; (b) 8 CM needle spacing group; (c) 12 CM needle spacing group; (d) HAD group; (e) AD group.
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Figure 5. Relative contents of volatile organic compounds in oat grass under various drying methods. (a) Relative levels of alkanes. (b) Relative content of aldehydes. (c) Relative levels of ketones, esters, alcohols, and some other compounds. Different letters indicate significant differences (p < 0.05) between sample means.
Figure 5. Relative contents of volatile organic compounds in oat grass under various drying methods. (a) Relative levels of alkanes. (b) Relative content of aldehydes. (c) Relative levels of ketones, esters, alcohols, and some other compounds. Different letters indicate significant differences (p < 0.05) between sample means.
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Figure 6. Specific analysis of volatile organic compounds. (a) OPLS–DA analysis. (b) OPLS-DA model displacement test. (c) VIP value of OPLS-DA model.
Figure 6. Specific analysis of volatile organic compounds. (a) OPLS–DA analysis. (b) OPLS-DA model displacement test. (c) VIP value of OPLS-DA model.
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Figure 7. Radar map of texture characteristics.
Figure 7. Radar map of texture characteristics.
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Figure 8. Relative content of hardness, brittleness, elasticity, and cohesiveness. Different letters indicate significant differences (p < 0.05) between sample means.
Figure 8. Relative content of hardness, brittleness, elasticity, and cohesiveness. Different letters indicate significant differences (p < 0.05) between sample means.
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Figure 9. Relative content of adhesiveness, chewiness, and maximum shear force. * indicates a significance level of p < 0.05, ** indicates a significance level of p < 0.01.
Figure 9. Relative content of adhesiveness, chewiness, and maximum shear force. * indicates a significance level of p < 0.05, ** indicates a significance level of p < 0.01.
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Figure 10. Principal component analysis of oat grass under different drying methods.
Figure 10. Principal component analysis of oat grass under different drying methods.
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Figure 11. Correlation analysis. (a) Correlation analysis heat map. (b) Pearson correlation coefficient matrix. * indicates a significance level of p < 0.05, ** indicates a significance level of p < 0.01.
Figure 11. Correlation analysis. (a) Correlation analysis heat map. (b) Pearson correlation coefficient matrix. * indicates a significance level of p < 0.05, ** indicates a significance level of p < 0.01.
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Table 1. Chemical composition analysis results of differential compounds of oat grass.
Table 1. Chemical composition analysis results of differential compounds of oat grass.
Compound CategoryCode NumberCompound NameCASChemical FormulaMoleculeRetention Time [min]Incense Type
Alkanes13,5,5-trimethyl-2-Hexene26456-76-8C9H18Agriculture 15 00468 i00111.743Mint scent
2Dodecane112-40-3C12H26Agriculture 15 00468 i00218.099Greasy odor
31-nonadecene18435-45-5C19H38Agriculture 15 00468 i00331.122Tobacco flavor
4Tridecane629-50-5C13H28Agriculture 15 00468 i00424.922/
53-methyl-Undecane1002-43-3C12H26Agriculture 15 00468 i00520.766Aromatic
6Tetradecane629-59-4C14H30Agriculture 15 00468 i00627.716/
71,2-Diphenoxyethane104-66-5C14H14O2Agriculture 15 00468 i00732.938/
Aldehydes8Decanal112-31-2C10H2OAgriculture 15 00468 i00821.944Citrus aroma
9Hexanal66-25-1C6H12OAgriculture 15 00468 i0090.900Grassy flavor
102-hexenal6728-26-3C6H10OAgriculture 15 00468 i0104.044Leafy green aroma
11Phenylacetaldehyde122-78-1C8H8OAgriculture 15 00468 i01115.418Fruity sweet aroma
122,4-Heptadienal4313-03-5C7H10OAgriculture 15 00468 i01213.009Aromatic
13Octyl aldehyde124-13-0C8H16OAgriculture 15 00468 i01313.325Fruity scent
Ketones14 β -Ionone14901-07-6C13H20OAgriculture 15 00468 i01429.779Violet scent
15Hexahydrofarnesyl Acetone502-69-2C18H36OAgriculture 15 00468 i01533.050Spicy notes
“/” indicates that the substance has no incense type.
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MDPI and ACS Style

Zhang, M.; Song, Z.; Li, B.; Qin, C.; Ding, C.; Liu, L. Study on the Effects of High-Voltage Discharge Plasma Drying on the Volatile Organic Compounds and Texture Characteristics of Oat Grass. Agriculture 2025, 15, 468. https://doi.org/10.3390/agriculture15050468

AMA Style

Zhang M, Song Z, Li B, Qin C, Ding C, Liu L. Study on the Effects of High-Voltage Discharge Plasma Drying on the Volatile Organic Compounds and Texture Characteristics of Oat Grass. Agriculture. 2025; 15(5):468. https://doi.org/10.3390/agriculture15050468

Chicago/Turabian Style

Zhang, Mingjie, Zhiqing Song, Bufan Li, Chunxu Qin, Changjiang Ding, and Liqiang Liu. 2025. "Study on the Effects of High-Voltage Discharge Plasma Drying on the Volatile Organic Compounds and Texture Characteristics of Oat Grass" Agriculture 15, no. 5: 468. https://doi.org/10.3390/agriculture15050468

APA Style

Zhang, M., Song, Z., Li, B., Qin, C., Ding, C., & Liu, L. (2025). Study on the Effects of High-Voltage Discharge Plasma Drying on the Volatile Organic Compounds and Texture Characteristics of Oat Grass. Agriculture, 15(5), 468. https://doi.org/10.3390/agriculture15050468

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