Abstract
Physicochemical properties and flavor characteristics of hemp seeds (HS) were analyzed by roasting temperature (140 °C, 160 °C, 180 °C) and time (initial, 3, 6, 9, 12 min). HS with roasting showed a lightness (L*) with increasing roasting time. Total flavonoid content (TFC) decreased significantly with roasting compared to initial, and total phenolic content (TPC) tended to decrease with increasing roasting time at low temperatures (140 °C), but relatively high temperatures (160 °C and 180 °C), TPC increased significantly with increasing roasting time. The electronic tongue (E-tongue) analysis showed that the sweetness tended to increase with increasing roasting temperature and time, but the bitterness also tended to increase sharply when roasted at 180 °C. The electronic nose (E-nose) analysis showed that the main terpenes like d-limonene, α-pinene, caryophyllene, and β-pinene that exhibit fresh, herbal, and lemon-like aromas were decreased with increasing roasting time. But the volatile compounds with a sweet aroma produced like 2.5-dimethylpyrazine, 2,3-dimethylpyrazine and 2-methyl propanal were increasing with high temperatures (160 °C and 180 °C). This study will provide basic information for developing products using HS.
Keywords: Hemp seed, Roasting, Physicochemical properties, Electronic tongue, Electronic nose
Introduction
Hemp seed (HS) is the hulled seed of hemp, an off-white annual herb of the Ginseng family (Jang et al. 2018), which is composed of 20–25% protein, 25–35% fat, and 20–30% carbohydrates. The high protein content and good digestibility of HS increase the availability of hempseed as a source of essential amino acids (Song et al. 2022). HS has a high nutritional value because it contains insoluble fiber and various minerals, and the oil extracted from hemp seeds is particularly high in unsaturated fatty acids, which have been reported to have positive health effects, including lowering cholesterol levels and lowering hypertension (Xu et al. 2021). In addition to food products such as bread, cereals, rice cakes, and milk, HS is widely used in the pharmaceutical and cosmetic industries to treat intractable constipation, various painful diseases, menstrual irregularities, and skin diseases (Jang et al. 2018; Han et al. 2016), In China, European countries, and elsewhere, its soft texture makes it a popular snack, either as is or after heat treatment (Xu et al. 2021).
Heat treatment is a processing method that can stabilize food by delaying undesirable catabolic reactions that occur during storage and accelerating non-enzymatic browning reactions to generate new antioxidants (Ahmed et al. 2020). Heat treatment causes physicochemical changes such as texture, color, moisture content, lipid changes, and melanoidin reactions in foods (Ahmed et al. 2020), and the melanoidin products generated during the process exhibit various bioactivities against lipid rancidity, including antioxidant activity and antimutagenicity (Jang et al. 2018). In particular, heat treatment alters the chemical composition and physical properties of seeds and nuts to enhance their aroma, color, or texture, and provides a nutty aroma and roasted taste through the formation of some volatile and coloring compounds (Durmaz and Gökmen 2010; Yin et al. 2022). However, the degree of roasting is one of the main factors that determine the flavor of a product, as different degrees of roasting lead to the formation of unpleasant flavors and toxic compounds such as genotoxins and polycyclic aromatic hydrocarbons (Zhang et al. 2021).
In the past few years, the food industry has been making great efforts to analyze the changes in taste component and aroma compounds of various seeds according to the degree of roasting, and recently, studies using electronic systems such as E-tongue and E-nose have been increasing (Lee et al. 2019; Adelina et al. 2021; Cho and Moazzem 2022). E-tongue is an analysis system that uses electronic sensors to derive relative values for five taste components, and it can quickly obtain data with reproducibility and objectivity, providing analysis of individual taste components and patterns of overall taste components (Jeong et al. 2023). An E-nose is a system that analyzes the volatile compounds present in many foods in a short period of time using sensors related to volatile compounds and provides results by simultaneously detecting the analysis of individual volatile compounds and the overall pattern of volatile compounds. These systems are widely used for their convenience (Jeong et al. 2023).
To date, the majority of studies on hemp seeds have focused on the effects of heat treatment on the nutritional composition and antioxidant activity of hemp seeds (Babiker et al. 2021; Chen et al. 2012). However, despite the increasing consumption of heat-treated hemp seeds, there is a lack of studies that simultaneously analyze the changes in antioxidant activity, color, taste, and volatile compounds of hemp seeds subjected to various conditions of heat treatment. Therefore, this study was conducted to analyze the changes in antioxidant activity, color, flavor, and aroma components of hemp seeds under various conditions (initial (0 min), 140°C_3 min, 140°C_6 min, 140°C_9 min, 140°C_12 min, 160°C_3 min, 160°C_6 min, 160°C_9 min, 160°C_12 min, 180°C_3 min, 180°C_6 min, 180°C_9 min, 180°C_12 min). In addition, we aimed to select the optimal roasting conditions for developing processed products using roasted hemp seeds in the future through the flavor change of hemp seeds according to roasting temperature and time. This study is expected to provide basic data for future research on not only hemp seeds but also various roasted seeds.
Material and methods
Materials
Hemp seeds (Cannabis sativa L.) used in this experiment were purchased from an online store and were frozen at − 18 °C until used in the experiment. The materials used for this study were ethanol, 2 N Folin-Ciocalteu’s reagent, 30% Na2CO3, 1 M potassium acetate, 10% aluminum nitrate, standards of total phenol, total flavonoid, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Kovat’s were purchased from Sigma-Aldrich Co (Louis, USA).
Hemp seed roasting condition
The roasting temperature and the time were chosen to exclude the burnt flavor and burnt color caused by extreme roasting in preliminary experiments. 30 g Hemp seeds were roasted at 140 °C, 160 °C and 180 °C for 3/6/9/12/minutes using the oven function of a multi-light oven (EON-C200F, SK Magic, Seoul, Republic of Korea). For roasting at 140 °C, the average temperature of the oven was measured to be 144.4 ± 2.30, for 160 °C it was 165.65 ± 1.40, and for 180 °C it was 185.97 ± 1.41. As the roasting time increased, the temperature of the oven progressed slightly higher than the initially set temperature.
Chromaticity measurement
Chromaticity of HS according to roasting was measured using a Chroma meter (CR-400, Konica Minolta Inc., Tokyo, Japan), and changes in brightness (L*), redness (a*), and yellowness (b*) of HS according to the roasting degree were measured (Hong et al. 2021).
Extract preparation
Extract for antioxidant component and activity analysis was prepared by adding 20 mL of 50% ethanol, an extraction solvent, to 4 g of ground HS using a grinder (CSM-309, Motor Millions Electric Co., China) and extracting it at room temperature for 24 h. To collect the extract, 10 mL of the supernatant obtained after centrifugation (GZ-0406, GYROZEN Co., Daejeon, Korea) at 4000 rpm for 13 min was recovered, and then filtered with a 0.45 μm syringe filter (Whatman Inc., Maidstone, UK) and used for analysis.
Measurement of total phenolic content and total flavonoid content
Total phenolic content (TPC) was measured according to Hong et al. (2020). 200 μL distilled water was added to 40 μL of 1 mg/ mL HS extract, and 200 μL of 2 N Folin-Ciocalteu’s reagent (Sigma-Aldrich Co., St. Louis, MO, USA) was added and shaken for 30 s. 600 μL of 30% Na2CO3 and 160 μL of distilled water were added to this solution, and the absorbance was measured at 750 nm after leaving at 25 °C for 2 h. The standard is gallic acid (Sigma-Aldrich Co.) The concentration was 0–500 μg/ mL, and the total phenol content was derived using the calibration curve obtained after analysis in the same procedure as the sample.
Total flavonoid content (TFC) was measured according to Hong et al. (2020). 1.5 mL of 95% ethanol was added to 0.5 mL of HS extract, 0.1 mL of 1 M potassium acetate and 10% aluminum nitrate were added, and 2.8 mL of distilled water was added and reacted at room temperature for 30 min. The TFC was calculated using the calibration curve obtained after measuring the absorbance at a wavelength of 415 nm after the reaction. The standard for the TFC was quercetin, and the content was derived using a concentration gradient (0.01, 0.02, 0.04, 0.06, 0.08 mg/mL) (Hong et al. 2020).
Measurement of antioxidant activity
The antioxidant activity of HS extract was confirmed by DPPH radical scavenging ability. It was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Each sample was mixed with 10 μL with a DPPH solution of 0.1 mM (Sigma-Aldrich Co., St. Louis, MO, USA) and stirred at room temperature for 20 min, and the absorbance was measured at 517 nm. The measured absorbance value was substituted into the following equation to calculate the DPPH radical scavenging ability (Hong et al. 2021).
DPPH radical scavenging activity (%) = (1−sample absorbance/blank absorbance) × 100.
E-tongue analysis for taste components
E-tongue systems (ASTREE II, Alpha MOS, Toulouse, France) were used to analyze the taste components of the extracted HS. The analysis time and concentration of samples were set according to the basic manual for e-tongue analysis and the studies of Jeong et al. (2023) and Yoon et al. (2022), and the relative flavor components between samples were analyzed. Sensors combined with the E-tongue system are sourness, saltiness, umami, sweetness, and bitterness (SRS-sourness, STS-saltiness, UMS-umami, SWS-sweetness, and BRS-bitterness), consisting of sensors related to five tastes felt by humans and two reference sensors. The sample used for electronic tongue analysis was stirred with 2 g of ground HS and 100 mL of purified water at 300 rpm for 30 min at 60 °C for elution of taste components. Ninety milliliter of deionized water was added to 10 mL of the stirred sample and then used for electronic tongue analysis. The prepared sample solution was mounted on a sampler of the E-tongue, and then the sensor was immersed in the sample solution for 2 min to measure the strength of individual taste compounds through contact. To reduce contamination and errors between samples during the analysis process, the cleaning process was carried out using purified water after each analysis, and 6 repetitions were performed per sample. Taste component patterns were identified using multivariate analysis (Jeong et al. 2023).
E-nose analysis for volatile compounds
An E-nose system (HERACLES Neo, Alpha MOS, Toulouse, France) was used to analyze the volatile compounds of the extracted HS, and an MXT-5 column was used as the analysis column. For the E-nose analysis, roasted 3 g of HS was taken and placed in a headspace vial (22.5 × 75 mm, PTEE/silicone septum, aluminum cap) for E-nose analysis, and stirred at 500 rpm at 50 °C for 20 min to saturate volatile compounds inside the vial. Volatile compounds were collected through an automatic sample collector attached to the E-nose, and volatile compounds of 2,000 μL of the collected gas were taken using a syringe and injected into the gas chromatography injection port mounted on the E-nose. The analysis conditions were 1 mL/min of hydrogen gas flow rate, acquisition time was 110 s, trap absorption temperature was 40 °C, and trap desorption temperature was 250 °C. The oven temperature was maintained at 40 °C for 5 s, and then increased to 270 °C at a ratio of 4 °C/s and maintained at 270 °C for 30 s. Retention index based on carbon number was based on Kovat’s index library, and peak components separated by using AcroChemBase (Alpha MOS) of the E-nose were identified. The electronic nose analysis system was based on 3 repetitions per sample, and the volatile component pattern was confirmed using multivariate analysis (Jeong et al. 2023).
Statistical analysis
The results of this study were presented as mean values and standard deviations repeated three times, and the statistical program used SAS version 9.0 (SAS Institute Inc., Cary, NC, USA) to verify the significance of the experimental values obtained through Tukey’s multiple range test (P < 0.05). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied for multivariate analysis using XL-STAT software ver. 9.2 (Addinsoft, New York, NY, USA) to identify how six types HS were located in the pattern of chemical sensory properties. Based on Kaiser rules, the PCA displays the variables and samples mapped through the loading and scoring of dimensional spaces determined by the PC with eigenvalues greater than 1.0 based on Kaiser’s rule (Shin et al. 2010a). The HCA was performed to identify relative dissimilarity among samples and reported as a dendrogram (Shin et al. 2010b).
Results and discussion
Chromaticity change in the HS by different roasting conditions
The color change of roasted hemp seeds is also shown in Table 1. When roasting for 3 and 6 min under all temperature conditions, the L* value tended to increase compared to the initial (0 min), after 9 min of roasting, most samples significantly decreased the L* value compared to initial, resulting in darkening (P < 0.05). In the case of HS roasted at 140 °C, the a* value decreased as the roasting time increased, and then increased again from 9 min. On the other hand, in the case of 160 °C, the a* value showed a tendency similar to 140 °C and decreased after 12 min of roasting. As with 160 °C, HS roasted at 180 °C showed a tendency for the a* value to decrease significantly as the roasting time increased (P < 0.05). The b* value showed a significant difference compared to the initial when roasted for a long time and tended to decrease significantly when roasted for 12 min under all temperature conditions (P < 0.05). As a result of chromometer analysis, HS generally decreases in L* value as the roasting time increases, and the brightness becomes darker. In addition, green and yellow colors were displayed during roasting, and when roasted for a long time (12 min), the b* value decreased and became blue.
Table 1.
Physicochemical characteristics in the HS by different roasting conditions
| Temp. (°C) | min | DPPH (%) | TFC (mg/mL) | TPC (mg/mL) | L* | a* | b* |
|---|---|---|---|---|---|---|---|
| 140 °C | 0 | 24.13 ± 0.99ab | 75.08 ± 0.41b | 121.64 ± 2.18a | 38.35 ± 0.08c | 0.31 ± 0.01a | 0.31 ± 0.01a |
| 3 | 32.41 ± 8.16a | 81.96 ± 0.35a | 101.82 ± 0.37d | 42.24 ± 0.04a | 0.30 ± 0.01b | 0.31 ± 0.01a | |
| 6 | 21.33 ± 1.66b | 13.41 ± 0.23d | 104.37 ± 0.23d | 41.44 ± 0.03b | 0.30 ± 0.01b | 0.31 ± 0.01a | |
| 9 | 16.79 ± 1.28b | 15.1 ± 0.29c | 107.94 ± 0.40c | 41.45 ± 0.01b | 0.31 ± 0.01a | 0.31 ± 0.01a | |
| 12 | 15.82 ± 2.87b | 14.29 ± 0.19c | 115.31 ± 0.13b | 37.14 ± 001d | 0.31 ± 0.01a | 0.30 ± 0.01b | |
| 160 °C | 0 | 24.13 ± 0.99a | 75.08 ± 0.41a | 121.64 ± 2.18b | 38.35 ± 0.08b | 0.31 ± 0.01a | 0.31 ± 0.01a |
| 3 | 14.14 ± 0.82c | 19.30 ± 0.27c | 112.18 ± 0.23d | 41.81 ± 0.01a | 0.30 ± 0.01b | 0.31 ± 0.01a | |
| 6 | 13.87 ± 1.48c | 12.12 ± 0.08e | 94.04 ± 0.50e | 41.91 ± 0.06a | 0.31 ± 0.01a | 0.31 ± 0.01a | |
| 9 | 19.80 ± 1.73b | 16.08 ± 0.12d | 116.76 ± 0.57c | 35.88 ± 0.01c | 0.31 ± 0.01a | 0.31 ± 0.01a | |
| 12 | 14.42 ± 1.67c | 50.50 ± 0.15b | 140.4 ± 0.40a | 31.38 ± 0.06d | 0.30 ± 0.01b | 0.29 ± 0.01b | |
| 180 °C | 0 | 24.13 ± 0.99a | 75.08 ± 0.41a | 121.64 ± 2.18c | 38.35 ± 0.08c | 0.31 ± 0.01a | 0.31 ± 0.01a |
| 3 | 19.47 ± 3.04ab | 66.41 ± 0.33b | 120.52 ± 0.85c | 41.47 ± 0.02a | 0.30 ± 0.01b | 0.31 ± 0.01a | |
| 6 | 14.82 ± 3.12b | 26.73 ± 0.15e | 94.22 ± 0.89d | 39.44 ± 0.02b | 0.31 ± 0.01a | 0.31 ± 0.01a | |
| 9 | 16.97 ± 0.82b | 34.29 ± 0.08d | 125.5 ± 0.69b | 32.36 ± 0.02d | 0.30 ± 0.01b | 0.30 ± 0.01b | |
| 12 | 24.14 ± 1.17a | 41.75 ± 0.16c | 181.88 ± 0.34a | 29.40 ± 0.01e | 0.29 ± 0.01c | 0.20 ± 0.01c |
Data represent the mean ± SD in triplicate
Mean values with different letters (a–e) within the same temperature are significantly different according to Tukey’s multiple range test (p < 0.05)
As a result of chromaticity analysis, the L* value indicating brightness was significantly different when roasted at 140 °C, 160 °C, and 180 °C for 3 min, and the L* value tended to decrease as the roasting time increased under all temperature conditions. Studies by Babiker et al. (2021) and Gholami and Ansari (2021) also showed a tendency for L* value to decrease as the time of roasting seeds increased (Babiker et al. 2021; Gholami & Ansari 2021). In a study by Babiker et al. (2021), the a* value, which indicates the degree of red and green, decreased significantly in the case of roasted HS at 160 °C at 7 min intervals and increased when roasted for 21 min (Babiker et al. 2021), and in this study, roasted HS at 140 °C showed a similar trend. However, when roasted at 160 °C and 180 °C, the a* value increased when roasted for a long time. In this study, the b* value, which indicates the degree of yellow and blue, did not show a significant change with the initial roasting but showed a tendency to decrease under all temperature conditions when roasted for 12 min. A study by Babiker et al. (2021), also showed a tendency for b* values to decrease when HS was roasted for a long time (Babiker et al. 2021). Most of these color changes occur during the roasting process of nuts, and it is known that the change in pigment is more noticeable when the Maillard reaction and the caramelization reaction are intensified (Gholami and Ansari 2021).
Change in TFC, TPC, and antioxidant activity in the HS by different roasting conditions
The TFC, TPC, and DPPH radical scavenging activities of roasted HS are shown in Table 1. The TFC of the initial was 75.08 mg/mL, and the content of TFC was significantly reduced compared to the initial under all conditions except roasted HS at 140 °C for 3 min (P < 0.05). Initial’s TPC was 121.64 mg/mL, showing a tendency for TPC to decrease as the roasting time increased at 140 °C. On the other hand, when roasted at 160 °C for 12 min, TPC was 140.40 mg/mL, which was significantly higher than that of the initial (P < 0.05). In the case of 180 °C, TPC showed a significantly higher content after 9 min (P < 0.05). The DPPH radical scavenging activity of the initial was 24.13%, and the DPPH radical scavenging activity decreased compared to the initial as the roasting time increased at 140 °C, but no significant difference was observed (P > 0.05). In the case of roasted HS at 160 °C, the DPPH radical scavenging activity decreased significantly compared to the initial as the roasting time increased (P < 0.05), and the DPPH radical scavenging activity decreased significantly as the roasting time increased even when roasted at 180 °C (P < 0.05), but there was no significant difference in roasting for 12 min (P > 0.05). As a result of this study, TFC, TPC, and DPPH radical scavenging activity did not show a common trend with roasting temperature and time.
In this study, the content of flavonoids was significantly reduced by roasting, and the results were similar to the significant decrease in the flavonoid content of buckwheat seeds in the process of roasting buckwheat seeds (Zielinski et al. 2009). This is confirmed to be the result of certain useful components escaping together by heat and osmotic pressure during roasting (Gholami and Ansari 2021). Roasting at 140 °C resulted in a significantly lower total phenolic content than initially. This shows a slight contradiction to the results at 160 and 180 °C, where the total phenolic content increased from the initial level after prolonged roasting. There is also a slight increase in the 12 min, which is significantly lower than the increase at 160 and 180 °C. This shows that the relatively low temperature of 140 °C can destroys the free form of phenolic compounds, which are relatively heat sensitive, but not high enough to break the bonds of bound phenols (Jo & Surh 2016). However, the total phenol content tended to increase with the increase in roasting time at 160 °C and 180 °C. However, the DPPH radical scavenging activity did not increase accordingly, which is confirmed to be the result of conversion to phenolic compounds without radical scavenging ability due to the roasting temperature and time increase, or the production of phenols without radical scavenging ability (Gholami and Ansari 2021). These phenols mostly were produced due to the conversion of the bound form, to the free form due to heat treatment, and the increased solubility of these substances due to the disruption of cell membranes and cell walls and softening of food tissues (Jo & Surh 2016). In this study, a slight change in DPPH radical scavenging activity was confirmed as the roasting time increased at 140 °C, but it did not increase significantly compared to the initial. In addition, when roasting at 180 °C for 12 min, the DPPH radical scavenging activity was increased, but there was no significant difference from the initial. In a study by Babiker et al. (2021) DPPH radical scavenging activity increased only in HS roasted at 160 °C for 21 min (Babiker et al. 2021), and in a study by Carciochi et al. (2016), it was found that DPPH radical scavenging activity increased when roasted at a high temperature of 190 °C for a long time (Carciochi et al. 2016). Therefore, it is confirmed that the antioxidant activity of HS will increase when roasted at a higher temperature for a long time, and the antioxidant content and activity of HS are confirmed to be affected in a very wide variety depending on roasting.
E-tongue analysis results
The results of the analysis of the taste components for roasted HS were indicated in Fig. 1. Initial was measured relatively high compared to other taste components with UMS of 10 in the sensory score, and BRS was measured with the lowest value of 3.6. On the other hand, in the case of roasted HS at 140 °C, the SRS and SWS tended to increase as the roasting time increased compared to initial, and the UMS tended to decrease. In the case of roasted HS at 160 °C, as at 140 °C, the SRS and SWS tended to increase as the roasting time increased. In particular, when roasted at 160 °C for 12 min, the SRS was 9.1, which was the highest among all roasting conditions. In the case of roasted HS at 180 °C, the SRS tended to increase as the roasting time increased, except for 3 min, and when roasted for 6 min, the SWS was 9.7, which was relatively the highest compared to other conditions. In the case of BRS, most of the values were higher than initial, but in the case of roasted HS at 180 °C, the highest BRS was shown compared to other conditions.
Fig. 1.
Taste intensities in roasted HS using E-tongue a 140 °C b 160 °C, and c 180 °C
Heat treatment of HS, which produces a savory taste, destroys or creates nutrients such as amino acids, fatty acids, and vitamins, thereby changing the aroma and taste of the raw material (Jang et al. 2018). In particular, heat treatment of cereals such as HS increases their sweetness, resulting in a sweet aroma and taste, and is said to improve food quality (Navicha et al. 2018; Jang et al. 2018). In Bagheri (2020) study, it is known that roasting nuts enhances their sweetness (Bagheri 2020), and in this study, the SWS of HS tended to increase with increasing roasting temperature and time. In particular, at 140 and 160 °C, the SWS increased with longer roasting time and at 180 °C for 6 min had the highest SWS. This is judged to be the result of an increase in sweet amino acids such as glycine, alanine, lysine, and threonine by roasting (Lee & Song 2018). But after 6 min, the SWS tended to decrease and BRS tended to increase. This increase in BRS is due to changes in carbohydrates and proteins and oxidation of fats that occur at high temperatures (Mohammadi Moghaddam et al. 2016). Over-roasting of seeds tends to increase BRS, so it is necessary to identify the appropriate roasting temperature and time and seed characteristics to improve product palatability (Zhang et al. 2021). Therefore, as a result of this study, roasting HS at 140 and 160 °C for more than 9 min is expected to help develop a product that shows a more preferred taste by increasing sweetness.
E-tongue multivariate analysis results
The results of taste components for HS analyzed using an E-tongue were shown through PCA and HCA, respectively, and are shown in Fig. 2a and b. Figure 2a shows the results of confirming the pattern of HS taste components using PCA, PC1 showed 54.59% variance, and PC2 showed 25.79% variance, showing a total of 80.38% variance. The samples with relatively high SWS and BRS were located in the positive direction of PC1, while the samples that were highly affected by UMS and SRS were located in the negative direction of PC1. The sample roasted at 180 °C was in the positive direction of PC1 because it exhibited high SWS and BRS. On the other hand, 140 °C for 12 min and 160 °C for 12 min, which exhibited high SWS but were highly affected by SRS, were in the negative direction for PC1. In particular, the initial with the highest UMS measurements was located in the negative direction for PC1. The results of the HCA for the taste components of HS are shown in Fig. 2b. A total of three clusters were identified as a result of the HCA. Cluster I includes roasted HS at 180 °C, cluster 2 includes roasted HS at 140 °C for 9 and 12 min, 160 °C for 6, 9, and 12 min, and cluster 3 includes roasted HS at initial, 140 °C for 3, 6, and 160 °C for 3 min. Cluster I and clusters II, III showed the highest dissimilarity. The multivariate analysis revealed a clear pattern of changes in the taste components of HS with roasting temperature and time, with samples roasted at high temperature (180 °C) showing a common high BRS (cluster I), samples with moderate roasting showing an increase in SWS and SRS (cluster II), and samples with relatively little change in taste components due to slight heat treatment (cluster III). Currently, multivariate analysis has been used to pattern changes in the volatile compounds of pine nuts according to roasting conditions (Adelina et al. 2021), and to pattern changes in the taste and volatile compounds of coffee according to different roasting conditions (Yoon et al. 2022), and the use of multivariate analysis is increasing to identify changes in the characteristics of samples according to different sample and pretreatment conditions.
Fig. 2.
Taste patterns in roasted HS by E-tongue a PCA and b HCA
E-nose analysis results
The results of the volatile aroma analysis of roasted HS using the electronic nose analysis system are shown in Table 2. A total of 82 volatile compounds were detected, including 3 terpenes, 10 furans, 2 pyrroles, 5 pyrazines, 8 acids and esters, 7 alcohols, 9 aldehydes, 3 heterocyclic compounds, 22 hydrocarbons, 3 ketones, and 10 sulfur-containing compounds. In the case of initial, heterocyclic compounds showed the highest peak area, and α-pinene was detected as a volatile compound of terpenes. In the case of roasted HS at 140 °C, α-pinene was detected only when roasted for 3 min, and furan and pyrrole were not detected for 3 and 6 min of roasting. For HS roasted at 160 °C for 6, 9, and 12 min, α-pinene, α-terpinene-7-al, and p-menthadiene-hydroperoxide were detected among the terpenes, and volatile compounds such as furan and pyrazine were detected more than at the initial. α-pinene and p-menthadien-hydroperoxide were detected when roasted at 180 °C for 3 min and 12 min, and sulfur-containing compounds were detected as the roasting time increased.
Table 2.
Volatile compounds in the HS by different roasting conditions using E-nose (Peak area × 103)
| Compounds | RT1)(RI2)) | Sensory description | Initial | 140 °C | 160 °C | 180 °C | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 3 min | 6 min | 9 min | 12 min | 3 min | 6 min | 9 min | 12 min | 3 min | 6 min | 9 min | 12 min | ||||
| Terpenes(3) | |||||||||||||||
| α-Pinene | 54.28(907) | Minty | 0.12 ± 0.03 | 0.63 ± 0.11 | ND3) | ND | ND | ND | 0.52 ± 0.05 | ND | ND | 0.54 ± 0.00 | ND | ND | ND |
| α-Terpinen-7-al | 79.93(1,288) | Fatty | ND | ND | ND | ND | ND | ND | 4.13 ± 0.27 | 4.74 ± 0.40 | ND | ND | ND | ND | ND |
| p-Mentha-dien-hydroperoxide | 82.14(1,332) | – | ND | ND | ND | ND | ND | ND | ND | ND | 8.78 ± 1.86 | ND | ND | ND | 13.95 ± 3.53 |
| Furans(10) | |||||||||||||||
| Furan | 25.11(474) | Burnt | ND | ND | ND | ND | ND | 0.09 ± 0.08 | ND | ND | 0.87 ± 0.34 | ND | ND | 0.74 ± 0.11 | 2.02 ± 0.92 |
| Tetrahydrofuran | 34.61(616) | – | ND | ND | ND | ND | ND | ND | 0.35 ± 0.15 | 0.68 ± 0.35 | ND | 0.15 ± 0.08 | ND | ND | ND |
| 3-Methylfuran | 35.88(635) | – | ND | ND | ND | ND | ND | 0.27 ± 0.14 | ND | ND | ND | ND | ND | ND | ND |
| 2-Ethylfuran | 40.41(702) | Burnt, Sweet | ND | ND | ND | 0.67 ± 0.44 | ND | 1.44 ± 0.08 | ND | ND | ND | ND | ND | ND | ND |
| Furfural | 47.40(806) | Almond, Bread | ND | ND | ND | 0.16 ± 0.09 | 0.14 ± 0.01 | ND | ND | ND | 0.40 ± 0.06 | ND | 0.04 ± 0.04 | 0.23 ± 0.11 | 0.86 ± 0.31 |
| 2-Furanmethanol | 49.60(839) | Bread, Coffee | ND | ND | ND | ND | 0.04 ± 0.04 | 0.50 ± 0.09 | ND | 0.18 ± 0.08 | 0.15 ± 0.07 | ND | ND | 0.18 ± 0.07 | ND |
| 2-Methyl-3-furanthiol | 51.57(868) | Nutty, Sweet | ND | ND | ND | ND | ND | ND | 0.30 ± 0.06 | ND | ND | ND | ND | ND | ND |
| 2-Furanone | 53.13(892) | Butter | ND | ND | ND | ND | 0.38 ± 0.04 | ND | ND | ND | 0.75 ± 0.15 | 0.21 ± 0.14 | ND | ND | 1.55 ± 0.26 |
| Dihydro-2-furanone | 53.60(899) | Caramelized, Sweet | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.33 ± 0.13 | ND | ND |
| 2-Butylfuran | 53.88(902) | Sweet | ND | ND | ND | 0.22 ± 0.06 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Pyrroles(2) | |||||||||||||||
| Pyrrole | 45.01(771) | Coffee, Nutty | ND | ND | ND | ND | ND | ND | 0.13 ± 0.05 | ND | ND | 0.10 ± 0.08 | ND | ND | ND |
| 2-Acetyl-1-pyrroline | 55.60(922) | Nutty, Roast | ND | ND | ND | 0.36 ± 0.06 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Pyrazines(5) | |||||||||||||||
| Pyrazine | 43.49(748) | Corn, Nutty | ND | ND | 0.19 ± 0.04 | ND | ND | ND | ND | ND | ND | 0.30 ± 0.04 | ND | ND | ND |
| 2.5-Dimethylpyrazine | 54.07(904) | Roast, Nutty | ND | ND | 0.21 ± 0.13 | ND | ND | ND | 0.32 ± 0.18 | ND | ND | ND | 0.52 ± 0.08 | ND | ND |
| Ethylpyrazine | 54.10(905) | Nutty, Peanut | ND | 0.11 ± 0.10 | 0.64 ± 0.10 | ND | 0.57 ± 0.07 | ND | ND | 0.72 ± 0.04 | 1.09 ± 0.08 | ND | ND | ND | ND |
| 2,6-Dimethylpyrazine | 54.20(906) | Corn, Coffee | ND | ND | ND | ND | ND | 0.10 ± 0.04 | ND | ND | ND | ND | ND | 0.53 ± 0.18 | ND |
| 2,3-Dimethylpyrazine | 55.57(922) | Baked, Caramelized | ND | ND | ND | ND | ND | 0.54 ± 0.02 | ND | ND | ND | ND | ND | 1.25 ± 0.09 | ND |
| Acids and Esters(8) | |||||||||||||||
| Diethyl ether | 24.60(467) | – | ND | ND | ND | ND | 0.43 ± 0.08 | ND | 0.29 ± 0.20 | ND | ND | ND | 0.33 ± 0.15 | 0.83 ± 0.19 | 1.49 ± 0.48 |
| Formic acid | 31.39(568) | Pungent | ND | ND | ND | ND | ND | ND | 0.76 ± 0.15 | ND | ND | ND | ND | ND | 0.11 ± 0.10 |
| Propanoic acid | 43.45(747) | Pungent | ND | ND | ND | 0.78 ± 0.09 | ND | ND | 0.92 ± 0.09 | 1.36 ± 0.22 | 6.02 ± 1.25 | ND | 0.99 ± 0.09 | 3.27 ± 0.76 | 11.94 ± 4.43 |
| Butanoic acid | 47.05(801) | Butter, Sweet | ND | ND | ND | ND | 0.24 ± 0.05 | ND | ND | 0.45 ± 0.12 | ND | ND | ND | ND | ND |
| Ethyl 2-methylbutyrate | 49.60(839) | Sweet | ND | ND | ND | ND | ND | ND | ND | 0.06 ± 0.01 | ND | ND | ND | ND | ND |
| Pentanoic acid | 55.72(924) | Sour, Sweet | 0.84 ± 0.05 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Nonyl acetate | 81.19(1,312) | Sweet | ND | 4.61 ± 0.40 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Methyl decanoate | 81.62(1,321) | oily | 5.41 ± 0.39 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Alcohols(7) | |||||||||||||||
| Methanol | 20.24(402) | Pungent | 0.84 ± 0.02 | 0.46 ± 0.08 | ND | ND | ND | 0.55 ± 0.14 | ND | ND | ND | ND | ND | ND | 2.93 ± 0.12 |
| 1-Propanol | 28.27(521) | Ethanol | ND | 0.07 ± 0.07 | 0.21 ± 0.19 | ND | ND | ND | ND | ND | ND | 0.68 ± 0.08 | ND | ND | ND |
| Butanol | 37.09(653) | Oily, Sweet | ND | ND | ND | ND | 0.59 ± 0.11 | ND | ND | ND | 1.56 ± 0.34 | ND | ND | ND | ND |
| 3-Hexanol | 46.96(800) | Ethanol | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 4.18 ± 0.55 |
| 2-Hexen-1-ol | 50.86(858) | Walnut | ND | 0.49 ± 0.13 | 0.61 ± 0.12 | ND | ND | ND | ND | ND | ND | ND | 0.27 ± 0.03 | ND | ND |
| 3-Hexen-1-ol | 50.91(859) | Oily | ND | ND | ND | 0.27 ± 0.02 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 2-Undecanol | 81.15(1,311) | Fruity | ND | ND | ND | ND | ND | ND | ND | ND | ND | 4.43 ± 0.11 | ND | ND | ND |
| Aldehydes(9) | |||||||||||||||
| Acetaldehyde | 22.48(435) | Pungent | ND | ND | 0.42 ± 0.09 | ND | ND | ND | ND | ND | ND | 1.43 ± 0.36 | ND | 6.47 ± 0.64 | 6.29 ± 1.90 |
| Propenal | 22.58(436) | Almond | 0.63 ± 0.06 | ND | 0.06 ± 0.05 | ND | ND | 0.54 ± 0.07 | ND | ND | ND | ND | ND | ND | ND |
| 2-Methylpropanal | 27.35(508) | Baked | ND | ND | 0.34 ± 0.06 | 3.57 ± 0.15 | 3.60 ± 0.26 | 0.18 ± 0.04 | 4.35 ± 0.35 | 4.77 ± 0.42 | 5.24 ± 0.08 | 0.57 ± 0.08 | 4.46 ± 0.40 | 6.23 ± 0.17 | 7.15 ± 2.34 |
| Butanal | 31.90(575) | Green, Pungent | 0.33 ± 0.04 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 2-Butenal | 36.38(642) | Pungent | ND | ND | ND | 0.41 ± 0.10 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 3-Methylbutanal | 36.41(643) | Almond | ND | 0.10 ± 0.04 | 0.44 ± 0.21 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Pentanal | 40.21(699) | Almond, Nutty | ND | ND | ND | ND | ND | ND | 1.20 ± 0.08 | ND | ND | 1.13 ± 0.28 | 1.14 ± 0.07 | ND | ND |
| 2-Pentenal | 43.54(749) | Oily, Pungent | ND | 0.08 ± 0.02 | ND | ND | 1.15 ± 0.16 | ND | ND | ND | ND | ND | ND | ND | ND |
| 2-Hexenal | 50.95(859) | Almond, Fatty | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.48 ± 0.07 | ND | ND | ND |
| Heterocyclic compounds(3) | |||||||||||||||
| Methyl formate | 20.27(402) | Fruity | ND | ND | ND | 4.68 ± 0.40 | 4.45 ± 0.22 | 0.21 ± 0.09 | 5.41 ± 0.61 | 5.54 ± 0.51 | 6.73 ± 0.55 | 1.23 ± 0.17 | 5.45 ± 0.81 | 7.95 ± 0.78 | 7.06 ± 0.88 |
| Trimethylamine | 22.44(434) | Amine, Pungent | 7.47 ± 1.64 | 1.00 ± 0.16 | ND | ND | ND | ND | ND | ND | 4.17 ± 0.84 | ND | 3.77 ± 1.24 | ND | ND |
| Indole | 79.86(1,286) | Burnt, Sweet | ND | ND | ND | 4.12 ± 0.13 | 4.53 ± 0.39 | 4.56 ± 0.16 | ND | ND | ND | ND | ND | ND | ND |
| Hydrocarbons(22) | |||||||||||||||
| Perfluorononane | 16.41(345) | – | ND | ND | 0.90 ± 0.03 | 0.65 ± 0.18 | 0.57 ± 0.10 | 0.90 ± 0.12 | 0.58 ± 0.08 | 0.67 ± 0.18 | 0.69 ± 0.31 | 3.92 ± 0.28 | 0.42 ± 0.09 | 2.11 ± 0.26 | ND |
| Butane | 18.80(380) | – | ND | ND | 1.04 ± 0.12 | ND | ND | ND | ND | ND | ND | ND | ND | ND | 4.38 ± 0.63 |
| Ethyl chloride | 22.49(435) | Pungent | ND | 0.24 ± 0.13 | 0.36 ± 0.06 | 1.09 ± 0.12 | 1.76 ± 0.32 | 0.36 ± 0.19 | 1.08 ± 0.05 | 1.93 ± 0.06 | ND | ND | ND | ND | ND |
| 2-Methylbutane | 24.87(471) | – | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.52 ± 0.19 | ND | ND | ND |
| Pentane | 26.89(501) | – | 0.09 ± 0.09 | ND | 0.30 ± 0.06 | ND | ND | ND | ND | ND | 1.16 ± 0.43 | ND | ND | ND | ND |
| Acetonitrile | 28.15(519) | Sweet | ND | 0.05 ± 0.04 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 1,1-Dichloroethene | 29.74(543) | Sweet | ND | ND | ND | ND | ND | ND | 1.36 ± 0.11 | ND | 6.89 ± 1.34 | ND | ND | ND | ND |
| 2-Methylpentane | 29.77(544) | – | ND | ND | ND | 1.34 ± 0.04 | 2.47 ± 0.45 | ND | ND | 1.81 ± 0.33 | ND | ND | 1.51 ± 0.12 | ND | ND |
| 1,1-Dichloroethane | 31.39(568) | Chloroform | ND | 0.21 ± 0.08 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 14.13 ± 4.59 |
| Cyclopentane | 31.38(568) | Sweet | ND | ND | ND | 0.74 ± 0.10 | 1.47 ± 0.29 | ND | ND | ND | ND | ND | 0.97 ± 0.21 | 3.74 ± 1.05 | ND |
| 1,2-Dichloroethene | 31.75(573) | Sweet | ND | ND | ND | ND | ND | 0.18 ± 0.02 | ND | ND | ND | ND | ND | ND | ND |
| Trichloroethane | 36.28(641) | Sweet | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.26 ± 0.23 | ND | ND |
| Acetoin | 39.75(692) | Butter, Sweet | ND | ND | ND | ND | 1.35 ± 0.21 | ND | ND | ND | ND | ND | ND | ND | ND |
| Dibromomethane | 40.35(701) | – | 2.70 ± 0.06 | 1.89 ± 0.11 | 1.23 ± 0.09 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Heptane | 40.94(710) | Sweet | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 2.28 ± 0.47 | ND |
| Ethylcyclopentane | 43.38(746) | – | 0.22 ± 0.04 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Methylcyclohexane | 43.48(748) | Sweet | ND | ND | ND | ND | ND | 0.09 ± 0.03 | ND | ND | ND | ND | ND | ND | ND |
| Toluene | 45.38(776) | Pungent, Caramelized | ND | ND | ND | ND | ND | 0.09 ± 0.11 | ND | ND | ND | ND | 0.21 ± 0.14 | ND | ND |
| 1-Ethyl-3-methylcyclopentane | 46.50(793) | Pungent | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 1.48 ± 0.35 | ND |
| 2-Octene | 47.93(814) | – | ND | 0.10 ± 0.03 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 3-Ethylheptane | 51.56(868) | – | 0.52 ± 0.21 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Tridecane | 80.60(1,300) | – | ND | ND | 4.50 ± 0.36 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Ketones(3) | |||||||||||||||
| Butane-2,2-dione | 31.73(573) | Butter, Creamy | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.36 ± 0.03 | ND | ND | ND |
| 1-Hydroxy-2-propanone | 37.04(652) | Caramelized, Sweet | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 1.25 ± 0.38 | 3.51 ± 1.09 |
| Acetoin | 39.67(691) | Butter, Coffee | ND | ND | ND | ND | ND | ND | ND | 1.47 ± 0.26 | 2.91 ± 0.34 | ND | ND | ND | ND |
| Sulfur-containing compounds(10) | |||||||||||||||
| Dimethyl sulfide | 27.18(505) | Corn, Sulfurous | ND | ND | ND | 1.48 ± 0.08 | ND | ND | ND | ND | ND | ND | 1.62 ± 0.23 | ND | 6.33 ± 0.38 |
| Carbon disulfide | 29.72(543) | Burnt, Sulfurous | ND | ND | ND | ND | ND | 0.13 ± 0.11 | ND | 2.86 ± 0.68 | 5.13 ± 1.19 | ND | ND | 3.80 ± 0.97 | ND |
| Ethanethiol | 29.89(545) | Sulfurous | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.53 ± 0.16 | ND | ND | ND |
| Thiophene | 36.52(644) | Sulfurous | 0.21 ± 0.20 | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| Butanethiol | 41.45(718) | Coffee, Sulfurous | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 5.38 ± 1.50 |
| 2-Methylthiophene | 47.08(802) | Sulfurous, Sweet | ND | ND | ND | ND | ND | ND | ND | ND | 1.71 ± 0.02 | ND | ND | ND | ND |
| Dimethyl sulfoxide | 50.93(859) | Sulfurous | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.17 ± 0.11 |
| Methional | 53.68(900) | Creamy, Baked | ND | ND | ND | ND | ND | ND | ND | 0.42 ± 0.19 | ND | ND | ND | ND | ND |
| 1-Hexanethiol | 55.64(923) | Burnt, Sulfurous | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 1.60 ± 0.33 |
| 1-Decanethiol | 82.10(1,331) | – | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND | 5.73 ± 0.51 | ND |
Data represent the mean ± SD in triplicate
(1) RT: retention time, (2) RI: retention indices, (3) ND: not detected
Terpenes are the main volatile compounds of HS and hemp products (Mansouri et al. 2023), with β-myrcene, d-limonene, α-pinene, caryophyllene, and β-pinene being the main terpenes (Mansouri et al. 2023). These volatile compounds mainly exhibit fresh, herbal, and lemon-like aromas also known as dried grassy aromas (Li et al. 2023). In particular, α-pinene, known as a volatile compound that contributes a lot to providing the aroma of hemp seeds (Song et al. 2022), was detected in this study when initial, 3 min at 140 °C, 6 min at 160 °C, and 3 min at 180 °C. The volatile compounds produced during roasting mainly belong to aldehydes, alcohols, pyrazines, and furans, which are mostly produced from complex reactions such as the Maillard reaction, fatty acid oxidation, and amino acid degradation (Mansouri et al. 2023). Pyrazines and furans are the main volatile compounds in heat-treated foods, exhibiting roasted and nutty aromas (Mansouri et al. 2023). 2.5-Dimethylpyrazine, which was detected for 6 min of roasting at all temperatures in this study, and 2,3-dimethylpyrazine, which was detected in hempseeds roasted for 3 min at 160 °C and 9 min at 180 °C, are known volatile compounds formed during HS roasting(Mansouri et al. 2023), and 2-methyl propanal, which was detected at all conditions except initial and 3 min at 140 °C, is also a volatile compound formed during the roasting process and represents a sweet, roasted aroma (Mansouri et al. 2023). The results of the E-nose in this study showed that the terpenes responsible for the main aroma of HS decreased with increasing roasting time. When roasting for a long time at a relatively high temperature (160 °C) and high temperature (180 °C), a lot of furan and pyrazine with a sweet aroma was produced.
E-nose multivariate analysis results
The results of volatile compounds for HS analyzed using an E-nose were shown through PCA and HCA, respectively, and were shown in Fig. 3a, b. Figure 3a shows the results of confirming the pattern of HS volatile compounds using PCA, PC1 showed 55.53% variance, and PC2 showed 15.33% variance, showing a total of 70.68% variance. HS roasted at 160 °C for 12 min, 180 °C for 9 min, and 180 °C for 12 min, which generated various volatile compounds by roasting, were located in the positive direction with respect to PC1, while other conditions were located in the negative direction with respect to PC1 because relatively few volatile compounds were detected. The results of the HCA for the volatile compounds of HS are shown in Fig. 3b. A total of two clusters were identified as a result of the HCA. Cluster1 included all HS except those roasted at 160 °C for 12 min, 180 °C for 9 min, and 180 °C for 12 min, while cluster 2 included HS roasted at 160 °C for 12 min, 180 °C for 9 min, and 180 °C for 12 min. Cluster 2 contains samples with a wide range of volatile compounds, among which a large number of sweet and roasted aromas produced during the roasting process were detected and classified with the other samples (cluster I). Multivariate analysis is currently being used in a variety of studies to classify and pattern samples. For example, it has been used to classify samples based on the compounds produced during the roasting process (Tsai et al. 2021) and to pattern samples based on the relative amounts of metabolites produced by fish (Castrica et al. 2021).
Fig. 3.
Volatile compound patterns in roasted HS by E-nose a PCA and b HCA
Conclusion
In this study, we analyzed the physicochemical properties and flavor characteristics of HS roasted under various conditions. The changes in chromaticity of HS with roasting temperature and time varied widely, and the L* value decreased with prolonged roasting (more than 9 min), resulting in a darker color. The changes in antioxidant content and activity did not show a continuous trend with roasting temperature and time. E-tongue analysis showed that the SWS tended to increase with increasing roasting temperature and time, but the BRS tended to increase sharply when roasted at 180 °C. Therefore, the roasting temperature and time according to seed characteristics are important to improve the product’s palatability. According to the result of the E-nose analysis, the terpenes that give the grassy aroma of HS decreased with the increase of roasting time. When roasted at relatively high temperatures (160 °C and 180 °C), most of the volatile compounds were detected, especially the volatile compound with a sweet aroma produced by roasting. In this study, the optimal conditions that showed positive effects of roasting (increased sweetness and sweet flavor) were 9 and 12 min at 140 °C, 6 and 12 min at 160 °C, and 6 min at 180 °C. Therefore, in the future, we would like to check the possibility of improving the flavor of hemp seed oil with roasted hemp seeds based on these conditions.
Acknowledgements
This research was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (NRF-2022R1I1A3066192).
Author contributions
Hyangyeon Jeong: Conceptualization, Formal analysis, Methodology, Writing—original draft. Sojeong Yoon: Conceptualization, Methodology, Writing—original draft. Seong Jun Hong: Methodology, Formal analysis. Seong Min Jo: Methodology, Formal analysis. Moon Yeon Youn: Supervision, Writing—review & editing. Eui-Cheol Shin: Conceptualization, Methodology, Supervision, Writing—review & editing.
Funding
The National Research Foundation of Korea (NRF-2022R1I1A3066192).
Data availability
Data will be made available on request.
Code availability
Not Applicable.
Declarations
Conflict of interest
There are no conflicts to declare. The authors declare that they have no conflict of interest and no competing financial interest.
Ethical approval
Not Applicable.
Consent to participate
All authors have read and approved the revised manuscript and informed of the submission to JFST.
Consent for publication
All authors have approved the publication of all this manuscript materials to JFST.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
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Data Availability Statement
Data will be made available on request.
Not Applicable.