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. 2022 Dec 1;17:100530. doi: 10.1016/j.fochx.2022.100530

Characteristic volatile compounds, fatty acids and minor bioactive components in oils from green plum seed by HS-GC-IMS, GC–MS and HPLC

Lirong Xu a, Shihao Wang a, Ailing Tian a, Taorong Liu b, Soottawat Benjakul c, Gengsheng Xiao d,⁎, Xiaoguo Ying e,⁎, Yuhong Zhang f,⁎, Lukai Ma d,e,⁎
PMCID: PMC9720238  PMID: 36478708

Highlights

  • •

    42 kinds of volatiles from green plum seed oils were identified by HS-GC-IMS.

  • •

    Green plum seed kernel oil had more ethyl acetate and 1-pentanol than shell oil.

  • •

    Green plum seed shell oil contained more alkenals and acetic acid than kernel oil.

  • •

    The seed oils were rich in oleic acid (>45 g/100 g) and linoleic acid (>35 g/100 g).

  • •

    The shell oil had more total tocopherol and phytosterol than kernel oil.

Keywords: Green plum seed oil, Flavor compounds, Fatty acids, Bioactive compounds

Abstract

Green plum is popular due to its tasty flavor and nutritional benefits. This study investigated the volatiles of oils extracted from the green plum seed using the headspace-gas chromatography-ion mobility spectrometry. A total of 42 volatiles were identified in the oil of green plum seed kernel and shell. By principal component analysis, a distinct separation between the seed kernel oil and shell oil was observed. The gallery plot showed that seed kernel oil had more desirable flavor compounds, such as ethyl acetate, 1-pentanol, 2-pentylfuran, and 2-heptanone. However, seed shell oil contained more alkenals with a fatty odor and acetic acid with a pungent odor. The green plum seed oils were rich in oleic acid (>45 g/100 g), linoleic acid (>35 g/100 g), and minor bioactive components, i.e., tocopherol, phytosterol, and squalene. The shell oil had more total tocopherol (95.35 mg/kg) and β-Sitosterol (80.70 %) compared to kernel oil. Therefore, green plum seed oil can be sustainably used as an edible oil.

1. Introduction

Green plum (Buchanania obovata) is a plant of the Rosaceae family, and is widely cultivated in China. Green plums have high nutritional value and health benefits (Wallace, 2017). Consuming dried green plums regularly may prevent osteoporosis caused by estrogen deficiency (Wallace, 2017). Green plums are rich in protein (1.7 g/100 g), fat (0.9 g/100 g), organic acids (6.0 g/100 g), and carbohydrates (16.4 g/100 g) (Fyfe, et al., 2022). The acids in green plums mainly consist of citric acid and succinic acid, which can stimulate appetite, quench thirst, and relieve fatigue (Fyfe, et al., 2022). Citric acid, which is essential to the metabolism of human cells (Fyfe, et al., 2022), can facilitate the degradation of lactic acid into carbon dioxide and water that can be excreted from the body. Green plum is an excellent plant resource that has a concomitant function of both medicine and food, and is nutritionally comprehensive and balanced with a variety of medical and health care functions (Fyfe et al., 2020, Smith et al., 2014). Fresh green plums are not well tasted due to the high acid content. Therefore, green plums are commonly consumed as processed food such as candied fruit, wine, and healthy food (Fyfe, Netzel, Tinggi, Biehl, & Sultanbawa, 2018). Green plum products are sold domestically and exported in large quantities and are popular food due to their flavor, nutritional and therapeutic benefits (Yan et al., 2014).

Green plums have a short storage time due to high respiration, weight loss and accelerated ripening, and are easily decayed resulting in large amounts of by-products such as pomace and fruit kernels. Most of the by-products are piled up and discarded in the open air. In the food processing of green plums, the kernels, which has potential benefits, are discarded (Górnaś et al., 2015, 2016). Currently, the studies of the kernels mainly focus on the extraction of the kernel pigment and the antioxidant, the production of the kernel wine, and the applications in medicine (Gorman, Wurm, Vemuri, Brady, & Sultanbawa, 2020). There are also reports on the bioactive components and fatty acids in the kernel oil of plums in Europe (Górnaś et al., 2015, Górnaś et al., 2016, Kiralan et al., 2018). However, there are limited reports on the volatile substances of the seed oil of green plums. The headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) is a fast and non-destructive method to detect volatile compounds (Pan et al., 2022). This technique has been widely applied in food flavor analysis, including adulteration determination and classification of edible oils (He et al., 2021, Jurado-Campos et al., 2021, Dou et al., 2022). However, there are limited researches on the flavor analysis of green plum seed oil by the HS-GC-IMS technique.

In this work, oil extracted from green plum seeds was selected as the experimental material, and the volatile aroma compounds, fatty acids, and minor bioactive components were identified. We analyzed the differences of the volatile compounds extracted from kernel and shell oil by HS-GC-IMS technology. This study aims to provide a theoretical and scientific basis for the comprehensive development and utilization of green plum kernels in the intensive processing field.

2. Materials and methods

2.1. Materials and reagents

The green plum seed was obtained from Guangdong Green plum Industrial Food Co., ltd. (Guangzhou, China), which is the largest cultivated area of green plums in China. It is the Puning green plum (big nuclear plum) and was collected in May 2021. The green plum seed was dried at ambient temperature (25 °C) for 48 h, and the moisture content was 12 %. The 37 fatty-acid methyl esters standards, tocopherol standards (α-, β-, γ- and δ-tocopherols), phytosterol, and squalene standards (campesterol, stigmasterol, β-sitosterol, Δ5-avenostenol, squalene) were purchased from Sigma-Aldrich Chemical Co. ltd. (Shanghai, China), other reagents and solvents were obtained from Sinopharm Chemical Regent (Shanghai, China).

2.2. Lipid extraction

This method was performed which based on previous study (Nie et al., 2020, Xu et al., 2022). Firstly, the kernels and shells were separated by hand. The green plum seed was grounded by a high-speed grindergrinder with the speed of 25,000 r/min for 3 min. The powders of green plum seed shell and kernel were dissolved with n-hexane (1:13 g/mL), then kept at 25 °C for 12 h. Later, the oil samples were extracted by a KQ-300 DE ultrasonic cleaner (Kunshan Shunmei Co., ltd., Jiangsu, China) at 30 °C, 350 W power, and 40 kHz. After 1.0 h, the compound was centrifuged at 10,000 g for 8 min. Finally, a rotary vacuum evaporator was used to obtain concentrated oil samples.

2.3. Determination of fatty acid composition

0.50 mg of extracted oil was dissolved in 2.0 mL n-hexane. Then 0.5 mL 2 mol/L KOH-CH3OH was added to prepare fatty acid methyl esters. The fatty acid was analyzed using a 7820A gas chromatograph (GC) (Agilent, Palo Alto, CA, USA). The Trace TR-FAME capillary column (0.25 μm, 60 m × 0.25 mm, Thermo Fisher, Waltham, MA, USA) was used to analyze the sample. Fatty acids were identified by comparing the retention times with standards of 37 fatty-acid methyl esters. Their contents were reported in terms of the relative percentages of individual fatty acids.

2.4. Tocopherols

Approximately 0.5 g of oils were weighed in a 10 mL brown volumetric flask and then dissolved with n-hexane. The mixed solution was filtered through a 0.22 μm nylon syringe filter and 10 μL of the solution was injected into a high-performance liquid chromatographic (LC-20AT, Shimadzu, Tokyo, Japan) for analysis. The ultraviolet detector was performed on SPD-20A (Shimadzu). A C18 column (5 μm, 4.6 × 250 mm, Hanbon, Jiangsu, China) was used to separate the α-, β-, γ- and δ-tocopherols. The column temperature was 30 °C, and the mobile phase was hexane/isopropanol (98.5/1.5, v/v) with a 1.0 mL/min rate. The determining wavelength at 295 nm was used. The tocopherols were identified by comparing their retention times with authentic standards and quantified based on the peak areas compared with the external standards. The range of the calibration curve is from 1.0 mg/kg to 100 mg/kg.

2.5. Phytosterol and squalene

The phytosterol and squalene were determined according to the study by Gao et al. (2019). Analyses were performed using a gas chromatography and mass spectrogram (Thermo Fisher, Waltham, MA, USA). DB-5 capillary column (0.25 μm, 30 m × 0.25 mm, Agilent) was used to separate compounds. Helium was used as carrier gas with a linear velocity of 1.2 mL/min. The GC oven temperature began at 200 °C, increased to 300 °C at 10 °C/min, and held for 18 min.

2.6. Volatile components analysis by gas Chromatography-Ion mobility spectrometry

The volatile component analysis of samples was completed using an Agilent 490 gas chromatograph (Agilent Technologies, Palo Alto, CA, USA) and IMS instrument (FlavourSpec®, Gesellschaft für Analytische Sensorsystem mbH, Dortmund, Germany). The gas chromatograph was equipped with an FS-SE-54-CB-0.5 column (0.25 µm, 15 m × 0.53 mm, Agilent, USA) containing 94 % methyl, 5 % phenyl, and 1 % vinyl silicone groups. The detailed conditions were referred to the study reported by Chang et al., (2020) with minor modifications. For sample analysis, 1 mL of oil sample was introduced into a 20-mL headspace vial. After incubation for 15 min at 60 °C, 200 μL of the volatile matter was injected into the heated injector at 60 °C in a splitless mode. The flow of nitrogen was 2 mL/min for 2 min, then increased to 10 mL/min for 8 min and increased to 100 mL/min for 10 min, finally increased to 150 mL/min for 10 min. Therefore, the total retention time was 30 min. The volatiles were detected based on the retention index and drift time of standards in the gas chromatography-ion mobility spectrometry (GC-IMS) library and mass spectrum of the NIST 2014.

2.7. Data analysis for gas Chromatography-Ion mobility spectrometry

Data from volatile compounds in samples was acquired and processed using Laboratory Analytical Viewer (LAV) analysis software and Library Search qualitative software (G.A.S., Dortmund, Germany). LAV software was used to view the analytical spectrum, where each dot represents a volatile compound. A reporter plugin was directly used to compare the spectral differences between samples (two-dimensional top view, Fig. 1). A gallery plot plugin was used to compare fingerprints, and visually and quantitatively compare the differences in volatile organic compounds among different samples (Fig. 2). A dynamic principal component analysis (PCA) plugin was used for dynamic principal component analysis and clustering analysis of the samples, and to quickly determine the types of unknown samples (Fig. 3). The schematic diagram of the experimental design for all analyses was shown in Fig. S1.

Fig. 1.

Fig. 1

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The two-dimensional topographic plot (a), Comparison of the difference spectrum of volatile compounds from green plum seed kernel oil (A) and shell oil (B) (b), GC-IMS spectra with detected volatile compounds numbers of samples (c). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2.

Fig. 2

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Gallery plot comparison of volatile compounds in green plum seed kernel oil (A) and shell oil (B). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig.3.

Fig.3

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PCA analysis of GC-IMS.

2.8. Statistical analyses

All analyses were conducted in triplicate. The relevant results were denoted as mean ± standard deviation (SD). Significant differences were performed by one-way analysis of variance (ANOVA) combined with Turkey's multiple-range test using SPSS 22.0 (IBM, Armonk, New York).

3. Results and discussion

3.1. Fatty acids compositions of oils

Table 1 showed the percentage of fatty acids in the green plum seed kernel and shell oils. A total of 15 kinds of fatty acids were detected in the green plum seed oils. The main fatty acids were oleic acid (C18:1n9c) and linoleic acid (C18:2n6c). The content of oleic acid and linoleic acid was more than 45.00 g/100 g and 35.00 g/100 g in the green plum seed oils, respectively. The contents of oleic acid and linoleic acid were consistent with the study reported by Matthaeus & Oezcan (2009). The oleic and linoleic acids play essential roles in our health (Li et al., 2021). Oleic acid helps to strengthen the immune system (Carrillo Pérez et al., 2012, Guo et al., 2020), and linoleic acid is beneficial to relieving microglia inflammation triggered by saturated fatty acid (Tu et al., 2019, Guo et al., 2019). In this sense, the green plum seed oil is worthy of further study. Apart from these two fatty acids, the content of palmitic acid (C16:0) was also high and reached more than 10.00 g/100 g. The contents of other fatty acids were no more than 1.00 g/100 g. Moreover, heneicosanoic acid (C21:0) and tricosanoic acid (C23:0) can only be detected in seed shell oil. The contents of the main fatty acids in seed shell oils were higher than that in seed kernel oils. Unsaturated fatty acids (UFA) were the primary fatty acids in green plum seeds, and the content of UFA was more than 82.70 g/100 g.

Table 1.

Fatty acid composition of green plum seed kernel and shell oils.

Fatty acids (g/100 g) Seed kernel oil Seed shell oil
C6:0 0.16 ± 0.00a 0.13 ± 0.00b
C8:0 0.14 ± 0.00a 0.08 ± 0.00b
C12:0 0.05 ± 0.00b 0.07 ± 0.00a
C16:0 11.23 ± 0.14b 11.72 ± 0.10a
C16:1n9c 1.09 ± 0.01a 1.11 ± 0.01a
C17:0 0.10 ± 0.00b 0.15 ± 0.00a
C18:1n9c 45.46 ± 0.20b 46.88 ± 0.30a
C18:2n6c 35.43 ± 0.20b 37.30 ± 0.20a
C18:3n3 0.22 ± 0.00b 0.27 ± 0.00a
C20:0 0.45 ± 0.00b 0.46 ± 0.00a
C20:1 0.18 ± 0.00b 0.27 ± 0.00a
C21:0 ND 0.03 ± 0.00a
C20:5n3 0.41 ± 0.00a 0.38 ± 0.00b
C23:0 ND 0.20 ± 0.00a
C24:0 0.20 ± 0.00a 0.12 ± 0.00b
SFA 12.33 ± 0.14b 12.96 ± 0.10a
MUFA 46.73 ± 0.21b 48.26 ± 0.31a
PUFA 36.06 ± 0.20b 37.95 ± 0.20a
UFA 82.79 ± 0.41b 86.21 ± 0.51a
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Values represent the means ± SD (n = 3); Values in the list with different letters are significant difference at p＜0.05; ND: not detected; C16:0, Palmitic acid; C18:0, Stearic acid; C18:1, Oleic acid; C18:2, Linoleic acid; C18:3n3, α-linolenic acid; SFA, Saturated fatty acid; MUFA, Monounsaturated fatty acid; PUFA, Polyunsaturated fatty acid; UFA, Unsaturated fatty acid.

3.2. Tocopherols, phytosterol, and squalene

The contents of tocopherols, phytosterol, and squalene in green plum seed kernel and shell oils are presented in Table 2. The γ-Tocopherol (47.48–56.33 mg/kg) was the main tocopherol component accounting for more than 50 % in green plum seed oils, followed by α-Tocopherol (23.73–38.52 mg/kg). The γ-Tocopherol and α-Tocopherol were the main Tocopherols in plum kernel oils, which was consistent with the study reported by Diaby et al., 2016, Górnaś et al., 2016. The γ-Tocopherol and α-Tocopherol are important for anti-inflammatory properties (Reiter, Jiang & Christen, 2007). Meanwhile, α-Tocopherol has antioxidation activity (Packer, Weber & Rimbach, 2001). There are many studies focused on its antioxidation properties in oil (Feng, Tjia, Zhou, Liu, Fu, & Yang, 2020). We can conclude that green plum seed oil can be used as an edible oil to supply high content of γ-Tocopherol and α-Tocopherol for humans. Moreover, β-Tocopherol and δ-Tocopherol existed in green plum seed oils, but their content were relatively low, both of which were 1.20 mg/kg. As shown in Table 2, the total content of tocopherols in seed shell oil was 95.35 mg/kg, which was higher than that in seed kernel oil. Overall, the shells affected the tocopherol content, and the tocopherol of oils extracted from seeds with shells was much higher than that of de-shelled seeds.

Table 2.

Tocopherol, phytosterol and squalene contents of green plum seed kernel and shell oils.

Compounds Seed kernel oil Seed shell oil
Tocopherols (mg/kg)
α-Tocopherol 24.65 ± 0.92b 38.10 ± 0.42a
β-Tocopherol 1.20 ± 0.00a 1.20 ± 0.00a
γ-Tocopherol 47.55 ± 0.07b 54.85 ± 1.48a
δ-Tocopherol 1.20 ± 0.00a 1.20 ± 0.00a
Sum 74.60 ± 0.99b 95.35 ± 1.91a
Phytosterol (%)
Campesterol 2.45 ± 0.04b 2.74 ± 0.01a
Stigmasterol 1.17 ± 0.04b 1.28 ± 0.02a
β-Sitosterol 80.25 ± 0.07b 80.70 ± 0.00a
Δ5-Avenostenol 16.15 ± 0.07a 15.30 ± 0.00b
Squalene (g/100 g) 0.013 ± 0.00a 0.011 ± 0.00b
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Values represent the means ± SD (n = 3); Values in the list with different letters are significant difference at p＜0.05.

As seen in Table 2, the contents of different phytosterols in the green plum seed kernel and shell oils were significantly different (p < 0.05). The contents of phytosterols in the shell seed oils were higher than that in the kernel oils except for Δ5-Avenostenol. The main phytosterol was β-Sitosterol (80.18–80.70 %), accounting for more than 80 %, which was consistent with the study reported by Górnaś et al., (2016). It was reported by Gabay et al., (2010) that stigmasterol was a phytosterol with potential anti-osteoarthritic properties. Meanwhile, phytosterols have many health benefits including decreasing cholesterol, antioxidant,anti-inflammatory and antibacterial properties, regulating thyroid, and promoting cell growth (Mackay & Jones, 2011), thus green plum seed oil is proposed to be a promising functional oil in food industry. Compared with β-Sitosterol, the contents of campesterol (2.41–2.75 %) and stigmasterol (1.13–1.30 %) were relatively low. Furthermore, the content of campesterol, stigmasterol, and β-sitosterol in the seed shell oil was higher than that in the seed kernel oil. The content of squalene was relatively low in green plum seed oil. Although the content in seed kernel oil was higher, it was only 0.013 g/100 g.

3.3. Data analysis of gas Chromatography-Ion mobility spectrometry

3.3.1. Volatile compound identification in green plum kernel oil and shell oil

Fig. 1 (a) showed the 2D topographical visualization of the volatiles in green plum kernel oil (A) and shell oil (B) by GC-IMS. The Y-axis showed the retention time of the gas chromatography. The X-axis represented the ion migration time. The whole spectrum represented the total volatile compounds of the oil samples. Every point represented one kind of volatile compound. The higher intensity of volatile compounds would change color from white to red. Most of the signals of oil samples appeared in the retention times of 100–1000 s and the drift time of 1.0–1.5. Fig. 1 (a) showed that the types of volatile compound of green plum seed kernel oil and shell oil were very similar, but the signal intensity was slightly different. The flavor of the green plum seed shell oil (B) with a darker color was more abundant in the retention times of 100–400 s and the drift time of 1.0–1.5. Fig. 1 (b) illustrated the volatile aroma compounds of the green plum seed kernel oil (A) sample as a reference. The comparison showed the differences in the volatile compounds of green plum seed shell oil. If there was no difference between samples, the background of the topographic map deducted from the other sample was white. The red indicated that the compound content was higher than the reference sample, and the blue indicated that the compound concentration was lower than the reference. When the green plum seed oil was extracted with the shell, the signals at the drift time of 1.0–1.4 increased, indicating that these volatiles were higher when oil was extracted from the shell. For markers 27 (ethyl acetate (M)), 28 (ethyl acetate (D)), 29 (butanal (M)), 30 (butanal (D)), 31(2-methylpropanal(M)) and 32 (2-methylpropanal(D)), green plum seed kernel oil was significantly higher than green plum seed shell oil, belonging to eaters and aldehydes compounds (Fig. 1 (c)). For markers 2 (n-Nonanal), 20 ((E)-2-pentenal), 21 (1-Penten-3-ol) and 42 ((E)-2-Nonenal) belonging to aldehydes compounds, green plum seed shell oil was slightly higher than green plum seed kernel oil.

3.3.2. Qualitative analysis of volatile compounds

Qualitative analysis of the oil samples were shown in Fig. 1 (c). Each spot represented one kind of volatile compound and the numbers shown in Fig. 1 (c) were listed in Table S1. A total of 42 signal peaks were identified, among which 25 volatile compounds were aldehydes, others contained 7 alcohols, 5 ketones, 2 furans, 2 esters, and one acid (Table 3). Some of the compounds exhibited two peaks corresponding to monomers and dimers. This phenomenon is possible since compounds with a high proton affinity can make ions form dimers when they move in the drift trough (Liu et al., 2020). The aldehydes contained alkanals (hexanal, pentanal, butanal, heptanal, nonanal, octanal, 3-methylbutanal, 2-methylpropanal, and 2-methylbutanal), alkenals ((E)-2-decenal, (E)-2-octenal, (E)-2-heptenal, (E)-2-pentenal, and (E)-2-nonenal) and substituted aldehydes (2-Furfural, and benzaldehyde). The alcohols included 1-pentanol, 1-penten-3-ol, 1-butanol, ethanol, and 4-ethylphenol. The ketones included 2-heptanone, 2-propanone, and 2-pentanone. Furans contained 2-pentylfuran and 2-butylfuran. Other volatile compounds included acetic acid and ethyl acetate.

Table 3.

Volatile compounds of green plum seed kernel and shell oils.

Volatiles Molecule
Formula		 MW RI RT [sec] DT Seed kernel oil
signal intensity		 Seed shell oil
signal intensity
Aldehydes (25)
(E)-2-Decenal C10H18O 154.3 1232.2 1144.30 1.48 783.87 ± 59.55b 1075.78 ± 34.54a
n-Nonanal(M) C9H18O 142.2 1105.8 772.26 1.49 2842.15 ± 133.97b 3096.11 ± 46.94a
n-Nonanal(D) C9H18O 142.2 1103.7 767.18 1.94 956.69 ± 45.19b 1097.09 ± 44.77a
(E)-2-Octenal(M) C8H14O 126.2 1073.3 697.81 1.33 5339.64 ± 132.67a 5182.51 ± 105.37a
(E)-2-Octenal(D) C8H14O 126.2 1070.6 691.89 1.82 15234.9 ± 269.93a 15138.34 ± 155.5a
Octanal(M) C8H16O 128.2 1011.3 575.30 1.42 2273.10 ± 3.36b 2369.31 ± 34.1a
Octanal(D) C8H16O 128.2 1011.9 576.50 1.82 1454.69 ± 44.94a 1421.22 ± 55.22a
Benzaldehyde C7H6O 106.1 975.3 506.46 1.46 23823.20 ± 302.2b 25986.06 ± 87.42a
(E)-2-Heptenal(M) C7H12O 112.2 960.8 478.93 1.26 2232.75 ± 26.29a 2204.25 ± 13.6a
(E)-2-Heptenal(D) C7H12O 112.2 960.8 478.93 1.67 10094.51 ± 179.61a 10150.28 ± 209.18a
2-Furfural(M) C5H4O2 96.1 830.2 294.54 1.09 565.07 ± 0.75b 625.62 ± 18.18a
2-Furfural(D) C5H4O2 96.1 829.8 294.20 1.33 2442.57 ± 37.76b 2613.94 ± 114.24a
Hexanal C6H12O 100.2 792.4 257.26 1.56 16613.78 ± 115.09a 16742.16 ± 158.93a
(E)-2-Pentenal C5H8O 84.1 752.3 220.96 1.35 274.98 ± 11.37b 375.11 ± 11.36a
Pentanal C5H10O 86.1 698 179.41 1.42 8119.95 ± 55.27a 7406.97 ± 45.3b
3-Methylbutanal(M) C5H10O 86.1 653.3 155.95 1.18 527.11 ± 2.46b 614.20 ± 20.54a
3-Methylbutanal(D) C5H10O 86.1 655.7 157.04 1.40 1787.23 ± 1.73a 1280.25 ± 5.25b
Butanal(M) C4H8O 72.1 595.4 131.49 1.12 520.68 ± 25.86a 522.61 ± 13.15a
Butanal(D) C4H8O 72.1 595.4 131.49 1.27 1940.56 ± 34.08a 1519.26 ± 28.33b
2-Methylpropanal(M) C4H8O 72.1 565.7 120.44 1.11 504.12 ± 9.27a 427.41 ± 6.75b
2-Methylpropanal(D) C4H8O 72.1 564.9 120.16 1.28 579.60 ± 9.03a 295.33 ± 10.79b
2-Methylbutanal(M) C5H10O 86.1 667.2 162.44 1.17 536.25 ± 6.33b 597.14 ± 7.95a
2-Methylbutanal(D) C5H10O 86.1 667 162.34 1.39 1326.95 ± 9.17a 975.36 ± 36.96b
Heptanal C7H14O 114.2 901.8 381.79 1.69 1667.64 ± 43.8a 1460.25 ± 87.19b
(E)-2-Nonenal C9H16O 140.2 1145.8 874.42 1.41 641.57 ± 36.09b 709.99 ± 18.9a
Alcohols (7)
1-Pentanol(M) C5H12O 88.1 769.7 236.20 1.52 4476.96 ± 111.59a 4294.58 ± 83.24a
1-Pentanol(D) C5H12O 88.1 771.5 237.92 1.81 725.93 ± 24.51a 616.41 ± 11.47b
1-Penten-3-ol C5H10O 86.1 688.5 172.95 0.94 180.40 ± 1.84b 197.93 ± 5.97a
1-Butanol C4H10O 74.1 680.2 168.80 1.18 651.67 ± 2.74a 636.69 ± 6.16b
Ethanol(M) C2H6O 46.1 500.3 99.35 1.05 1002.69 ± 8.91a 1027.68 ± 17.67a
Ethanol(D) C2H6O 46.1 503.1 100.17 1.13 584.23 ± 9.69a 531.98 ± 20.76b
4-Ethylphenol C8H10O 122.2 1173 951.71 1.20 478.14 ± 34.15a 463.87 ± 49.16a
Ketones (5)
2-Heptanone(M) C7H14O 114.2 893 369.12 1.27 542.68 ± 9.04a 455.58 ± 31.55b
2-Heptanone(D) C7H14O 114.2 891.5 367.05 1.63 1862.97 ± 93.32a 1579.13 ± 96.04b
2-Propanone C3H6O 58.1 514.9 103.71 1.11 443.49 ± 1.54b 487.49 ± 6.85a
2-Pentanone(M) C5H10O 86.1 688.7 173.10 1.12 228.53 ± 5.61b 245.35 ± 1.87a
2-Pentanone(D) C5H10O 86.1 690.8 174.48 1.37 486.20 ± 14.83a 471.11 ± 36.31a
Furans (2)
2-Pentylfuran C9H14O 138.2 994.9 545.97 1.25 3890.07 ± 52.67a 3331.52 ± 126.73b
2-Butylfuran C8H12O 124.2 890.7 365.93 1.18 251.58 ± 4.26a 180.41 ± 2.8b
Acids (1)
Acetic acid C2H4O2 60.1 740.7 211.38 1.16 2021.51 ± 128.29b 3445.69 ± 534.07a
Esters (2)
Ethyl acetate(M) C4H8O2 88.1 616.8 140.01 1.09 573.06 ± 12.4a 347.26 ± 24.35b
Ethyl acetate(D) C4H8O2 88.1 614.1 138.92 1.34 803.68 ± 5.21a 160.80 ± 4.72b
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Values represent the means ± SD (n = 3); M: monomer, D: dimer; MW: Represents the molecular weight of the volatile compounds. RI: Represents the retention index calculated using n-ketone C4-C9 as the external standard in the FS-SE-54-CB column. RT: Represents the retention time in the capillary GC column. DT: Represents the drift time in the drift tube. The volatiles were detected based on the RI and drift time of standards in the GC-IMS library and mass spectrum of the NIST 2014.

Due to their low odor threshold, aldehydes usually play an important role in the flavor of edible oil products. Some alkanals, e.g., hexanal, heptanal, octanal, and nonanal, were mainly described as green and fatty odor. Aldehydes were mainly derived from the degradation of fatty acids (Xu, Mei, Wu, Karrar, Jin, & Wang, 2022). Hexanal with a green, leafy or woody aroma, was mainly the decomposition product of linoleic acid-13-COOH by β-homogenous cracking (Xu, Mei, Wu, Karrar, Jin, & Wang, 2022). The contents of hexanal, octanal, and nonanal were higher in the green plum seed shell oil than the kernel oil, mainly due to the higher linoleic acid and α-linolenic acid contents in the green plum seed shell oil.

Alkenals are mainly existed with trans-forms with ten carbon or less, including (E)-2-nonenal and (E)-2-decenal, with fatty aroma. Similarly, the higher linoleic acid and α-linolenic acid contents in the green plum seed shell oil led to the higher content of (E)-2-nonenal and (E)-2-decenal. Moreover, the content of benzaldehyde with a fruity and woody aroma in green plum seed shell oil reached 25986.06 compared to the kernel oil with a content of 23823.20. It was considered as the decomposition product of linoleic acid (Chang, Wu, Zhang, Jin, & Wang, 2019).

Alcohols had a higher threshold than aldehydes (van Gemert, 2011). Alcohols were mainly derived from lipids oxidation or reduction synthesis of carbonyl groups. 1-pentanol had a spice odor, which was commonly found in volatile compounds of edible oil. The green plum seed kernel oil had higher content (725.93) than the shell oil (616.41). The threshold of ketones was much higher than aldehydes, with a lower contribution to the flavor. Ketones might produce from the oxidation of unsaturated fatty acids. The 2-heptanone with fruit odor was higher in the green plum seed kernel oil (1862.97) than that in the shell oil (1579.13).

Similarly, the 2-pentylfuran (butter, fruity, green bean odor) in the green plum seed kernel oil was higher than that in the shell oil. Besides, green plum seed kernel oil had higher ethyl acetate (slightly fruity aroma), which was an important volatile compound that contributed to the flavor of edible oil (Yang et al., 2022). In contrast, the acetic acid with the acid odor was higher in the green plum seed shell oil than in the kernel oil; therefore, the green plum seed kernel oil was more desirable than the shell oil.

3.3.3. Comparison of fingerprints of volatile compounds

A gallery plot was used to intuitively compare the samples (Pan et al., 2022). The characteristic fingerprint was established according to the differences of volatile compounds in green plum seed oil samples. The gallery plot of volatile compounds in green plum seed kernel oil and shell oil is shown in Fig. 2. The intensity of the signal was reflected by the degree of color. The color changed from blue to red when the contents increased. The letter M and D represented the monomer and dimer of the compound, respectively. The gallery plot showed that group repeatability was quite high, and the differences between green plum seed kernel oil and shell oil were clear. In the red box, the intensity of components in the green plum seed kernel oil was much stronger, including ethyl acetate, heptanal, butanal, 2-methylbutanal, 3-methylbutanal, 1-pentanol, 2-butylfuran, 2-pentylfuran, 2-methylbutanal, 2-heptanone, and 2-pentanone. The ethyl acetate contributed to the fruity aroma, producing a desirable odor in the green plum seed kernel oil. In the yellow box, the signal intensity of green plum seed shell oil was much higher than that of kernel oil, including (E)-2-pentenal, acetic acid, (E)-2-decenal, nonanal, (E)-2-nonenal, 1-penten-3-ol and benzaldehyde, indicating that part of the volatile compounds that originally existed in the shell were found in the seed oil with the shell. The acetic acid had a pungent odor, resulting in an undesirable aroma in the shell oil. The results showed that GC-IMS was a feasible method to distinguish the differences between different oil samples.

3.3.4. Principal component analysis of gas Chromatography-Ion mobility spectrometry

The PCA can evaluate the regularity and differences among samples by the contribution rate of PC factors (Wang et al., 2021). The PCA results of volatile compounds in oil samples were shown in Fig. 3. Generally, the PCA model was selected as the separation model when the contribution rate reached 60 % (Chen, Chen, Xiao, Liu, Tang, & Zhou, 2020). The contribution rate of the first two principal components reached 86 %, indicating that the GC-IMS data can explain most of the flavor information. There was a clear separation trend of green plum seed kernel oil and shell oil samples in the axis of PC2, indicating that green plum seed kernel oil and shell oil was significantly different.

4. Conclusion

The volatile aroma compounds and minor bioactive components of green plum seed kernel oil and shell oil were evaluated. This study innovatively investigate the volatile compounds of oils extracted from the green plum seed by GC-IMS. In this study, we found that flavor compounds of green plum seed kernel oil can be distinguished from shell oil by using PCA method. A total of 42 volatile components were identified in green plum seed kernel and shell oil. The differences in volatile compounds of green plum seed kernel and shell oil samples were observed. Combining with gallery plot, the results showed that green plum seed kernel oil had more desirable flavor compounds that contributed to the fruity aroma, e.g., ethyl acetate, 1-pentanol, 2-pentylfuran, and 2-heptanone. However, the green plum seed shell oil contained more alkenals with a fatty odor, mainly due to the higher linoleic acid and α-linolenic acid contents. Moreover, acetic acid content was higher in the shell oil, contributing to the pungent odor. Therefore, the kernel oil had more desirable volatile compounds than the shell oil. A total of 15 kinds of fatty acids were detected in the green plum seed oils. The green plum seed oils were rich in unsaturated fatty acid, especially oleic acid and linoleic acid. Furthermore, the oil samples were rich in minor bioactive components, i.e., tocopherol, phytosterol, and squalene, and the shell oil had more total tocopherol and phytosterol compared to the kernel oil. The results suggested that green plum seed oil is a potential edible oil source. This study provides a theoretical basis for the intensive processing of green plum kernels.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was financed by the National Natural Science Foundation of China (Project No.32001622), the National Natural Science Foundation of China (Project No.32202083), Guangdong Province agricultural science and technology innovation ten main direction of the “top” project (NO. 2022SDZG04), Guangdong Basic and Applied Research Foundation (Project No. 2021A1515011060), the Fundamental and Applied Basic Research Fund for Young Scholars of Guangdong Province (Project No. 2019A1515110823).

Footnotes

Appendix A

Supplementary data to this article can be found online at https://doi.org/10.1016/j.fochx.2022.100530.

Contributor Information

Gengsheng Xiao, Email: xiaogengsheng@zhku.edu.cn.

Xiaoguo Ying, Email: yingxiaoguo@zjou.edu.cn.

Yuhong Zhang, Email: zhangyh75@taaas.org.cn.

Lukai Ma, Email: malukai@zhku.edu.cn.

Appendix A. Supplementary data

The following are the Supplementary data to this article:

Supplementary data 1
mmc1.docx (246.6KB, docx)

Data availability

Data will be made available on request.

References

  1. Carrillo Pérez C., Cavia Camarero M.D.M., Alonso de la Torre S. Role of oleic acid in immune system; mechanism of action; a review. Nutrición Hospitalaria. 2012;27(4):978–990. doi: 10.3305/nh.2012.27.4.5783. [DOI] [PubMed] [Google Scholar]
  2. Chang C., Wu G., Zhang H., Jin Q., Wang X. Deep-fried flavor: Characteristics, formation mechanisms, and influencing factors. Critical Reviews in Food Science and Nutrition. 2019;60(9):1496–1514. doi: 10.1080/10408398.2019.1575792. [DOI] [PubMed] [Google Scholar]
  3. Chang M., Zhao P., Zhang T., Wang Y., Guo X., Liu R.…Wang X. Characteristic volatiles fingerprints and profiles determination in different grades of coconut oil by HS-GC-IMS and HS-SPME-GC-MS. International Journal of Food Science & Technology. 2020;55(12):3670–3679. [Google Scholar]
  4. Chen X., Chen H., Xiao J., Liu J., Tang N., Zhou A. Variations of volatile flavour compounds in finger citron (Citrus medica L. var. sarcodactylis) pickling process revealed by E-nose, HS-SPME-GC-MS and HS-GC-IMS. Food Research International. 2020;138 doi: 10.1016/j.foodres.2020.109717. [DOI] [PubMed] [Google Scholar]
  5. Diaby M., Amza T., Onivogui G., Zou X.Q., Jin Q.Z. Physicochemical and antioxidant characteristics of gingerbread plum (Neocarya macrophylla) kernel oils. Grasas y Aceites. 2016;67(1):e117–e. [Google Scholar]
  6. Dou X., Zhang L., Yang R., Wang X., Yu L., Yue X.…Li P. Adulteration detection of essence in sesame oil based on headspace gas chromatography-ion mobility spectrometry. Food Chemistry. 2022;370 doi: 10.1016/j.foodchem.2021.131373. [DOI] [PubMed] [Google Scholar]
  7. Feng X., Tjia J.Y.Y., Zhou Y., Liu Q., Fu C., Yang H. Effects of tocopherol nanoemulsion addition on fish sausage properties and fatty acid oxidation. LWT - Food Science and Technology. 2020;118 [Google Scholar]
  8. Fyfe S.A., Netzel M.E., Tinggi U., Biehl E.M., Sultanbawa Y. Buchanania obovata: An Australian indigenous food for diet diversification. Nutrition & Dietetics. 2018;75(5):527–532. doi: 10.1111/1747-0080.12437. [DOI] [PubMed] [Google Scholar]
  9. Fyfe S., Smyth H.E., Schirra H.J., Rychlik M., Sultanbawa Y. The nutritional potential of the native australian green plum (Buchanania obovata) compared to other anacardiaceae fruit and nuts. Frontiers in Nutrition. 2020;7(311) doi: 10.3389/fnut.2020.600215. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Fyfe S., Schirra H.J., Rychlik M., van Doorn A., Tinngi U., Sultanbawa Y., Smyth H.E. Future flavours from the past: Sensory and nutritional profiles of green plum (Buchanania obovata), red bush apple (Syzygium suborbiculare) and wild peach (Terminalia carpentariae) from East Arnhem Land, Australia. Future Foods. 2022;5 [Google Scholar]
  11. Gabay O., Sanchez C., Salvat C., Chevy F., Breton M., Nourissat G.…Berenbaum F. Stigmasterol: A phytosterol with potential anti-osteoarthritic properties. Osteoarthritis and Cartilage. 2010;18(1):106–116. doi: 10.1016/j.joca.2009.08.019. [DOI] [PubMed] [Google Scholar]
  12. Gao P., Liu R., Jin Q., Wang X. Comparative study of chemical compositions and antioxidant capacities of oils obtained from two species of walnut: Juglans regia and Juglans sigillata. Food Chemistry. 2019;279:279–287. doi: 10.1016/j.foodchem.2018.12.016. [DOI] [PubMed] [Google Scholar]
  13. Gorman J.T., Wurm P.A., Vemuri S., Brady C., Sultanbawa Y. Kakadu Plum (Terminalia ferdinandiana) as a sustainable indigenous agribusiness. Economic Botany. 2020;74(1):74–91. [Google Scholar]
  14. Górnaś P., Mišina I., Grāvīte I., Lācis G., Radenkovs V., Olšteine A.…Rubauskis E. Composition of tocochromanols in the kernels recovered from plum pits: The impact of the varieties and species on the potential utility value for industrial application. European Food Research and Technology. 2015;241(4):513–520. [Google Scholar]
  15. Górnaś, P., Rudzinska, M., Raczyk, M., Misina, I., Soliven, A., La̅cis, G., & Seglina, D. (2016). Impact of species and variety on concentrations of minor lipophilic bioactive compounds in oils recovered from plum kernels. Journal of Agricultural and Food Chemistry, 64(4), 898-905. [DOI] [PubMed]
  16. Guo X.F., Li K.L., Li J.M., Li D. Effects of EPA and DHA on blood pressure and inflammatory factors: A meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition. 2019;59(20):3380–3393. doi: 10.1080/10408398.2018.1492901. [DOI] [PubMed] [Google Scholar]
  17. Guo X.F., Tong W.F., Ruan Y., Sinclair A.J., Li D. Different metabolism of EPA, DPA and DHA in humans: A double-blind cross-over study. Prostaglandins. Leukotrienes and Essential Fatty Acids. 2020;158 doi: 10.1016/j.plefa.2019.102033. [DOI] [PubMed] [Google Scholar]
  18. He J., Wu X., Yu Z. Microwave pretreatment of camellia (Camellia oleifera Abel.) seeds: Effect on oil flavor. Food Chemistry. 2021;364 doi: 10.1016/j.foodchem.2021.130388. [DOI] [PubMed] [Google Scholar]
  19. Jurado-Campos N., García-Nicolás M., Pastor-Belda M., Bußmann T., Arroyo-Manzanares N., Jiménez B.…Arce L. Exploration of the potential of different analytical techniques to authenticate organic vs. conventional olives and olive oils from two varieties using untargeted fingerprinting approaches. Food Control. 2021;124 [Google Scholar]
  20. Kiralan M., Kayahan M., Kiralan S.S., Ramadan M.F. Effect of thermal and photo oxidation on the stability of cold-pressed plum and apricot kernel oils. European Food Research and Technology. 2018;244(1):31–42. [Google Scholar]
  21. Li K., Shi Y., Zhu S., Shao X., Li H., Kuang X.…Li D. N-3 polyunsaturated fatty acids effectively protect against neural tube defects in diabetic mice induced by streptozotocin. Food & Function. 2021;12(19):9188–9196. doi: 10.1039/d1fo01606g. [DOI] [PubMed] [Google Scholar]
  22. Liu D., Bai L., Feng X., Chen Y.P., Zhang D., Yao W.…Liu Y. Characterization of Jinhua ham aroma profiles in specific to aging time by gas chromatography-ion mobility spectrometry (GC-IMS) Meat Science. 2020;168 doi: 10.1016/j.meatsci.2020.108178. [DOI] [PubMed] [Google Scholar]
  23. MacKay D.S., Jones P.J. Phytosterols in human nutrition: Type, formulation, delivery, and physiological function. European Journal of Lipid Science and Technology. 2011;113(12):1427–1432. [Google Scholar]
  24. Matthaeus B., Oezcan M.M. Fatty acids and tocopherol contents of some Prunus spp. kernel oils. Journal of Food. Lipids. 2009;16(2):187–199. [Google Scholar]
  25. Nie R., Zhang Y., Zhang H., Jin Q., Wu G., Wang X. Effect of different processing methods on physicochemical properties, chemical compositions and in vitro antioxidant activities of Paeonia lactiflora Pall seed oils. Food Chemistry. 2020;332 doi: 10.1016/j.foodchem.2020.127408. [DOI] [PubMed] [Google Scholar]
  26. Packer, L., Weber, S. U., & Rimbach, G. (2001). Molecular aspects of α-tocotrienol antioxidant action and cell signalling. The Journal of Nutrition, 131(2), 369S-373S. [DOI] [PubMed]
  27. Pan W., Benjakul S., Sanmartin C., Guidi A., Ying X., Ma L.…Deng S. Characterization of the Flavor Profile of Bigeye Tuna Slices Treated by Cold Plasma Using E-Nose and GC-IMS. Fishes. 2022;7(1):13. [Google Scholar]
  28. Reiter E., Jiang Q., Christen S. Anti-inflammatory properties of α-and γ-tocopherol. Molecular Aspects of Medicine. 2007;28(5–6):668–691. doi: 10.1016/j.mam.2007.01.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Smith B., Graef J., Wronski T., Rendina E., Williams A., Clark K., Clarke S., Lucas E., Halloran B. Effects of dried plum supplementation on bone metabolism in adult c57bl/6 male mice. Calcified Tissue International. 2014;94(4):442–453. doi: 10.1007/s00223-013-9819-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Tu T.H., Kim H., Yang S., Kim J.K., Kim J.G. Linoleic acid rescues microglia inflammation triggered by saturated fatty acid. Biochemical and Biophysical Research Communications. 2019;513(1):201–206. doi: 10.1016/j.bbrc.2019.03.047. [DOI] [PubMed] [Google Scholar]
  31. van Gemert L.J. second enlarged and revised ed.; Oliemans Punter & Partners BV:; Netherlands: 2011. Odour thresholds. Compilations of odour threshold values in air, water and other media. [Google Scholar]
  32. Wallace T. Dried plums, prunes and bone health: A comprehensive review. Nutrients. 2017;9(4):401. doi: 10.3390/nu9040401. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Wang F., Gao Y., Wang H., Xi B., He X., Yang X., Li W. Analysis of volatile compounds and flavor fingerprint in Jingyuan lamb of different ages using gas chromatography-ion mobility spectrometry (GC–IMS) Meat Science. 2021;175 doi: 10.1016/j.meatsci.2021.108449. [DOI] [PubMed] [Google Scholar]
  34. Xu L., Mei X., Wu G., Karrar E., Jin Q., Wang X. Inhibitory effect of antioxidants on key off-odors in French fries and oils and prolong the optimum frying stage. LWT-Food Science and Technology. 2022;162 doi: 10.1016/j.lwt.2022.113417. [DOI] [Google Scholar]
  35. Xu L., Liu T., Cao H., Zheng L., Zhu C., Karrar E., Shen X. Influence of different extraction methods on the chemical composition, antioxidant activity, and overall quality attributes of oils from Trichosanthes kirilowii Maxim seed. Food Control. 2022;142 [Google Scholar]
  36. Yan X., Lee S., Li W., Sun Y., Yang S., Jang H., Kim Y. Evaluation of the antioxidant and anti-osteoporosis activities of chemical constituents of the fruits of Prunus mume. Food Chemistry. 2014;156:408–415. doi: 10.1016/j.foodchem.2014.01.078. [DOI] [PubMed] [Google Scholar]
  37. Yang Y., Yu P., Sun J., Jia Y., Wan C., Zhou Q., Huang F. Investigation of volatile thiol contributions to rapeseed oil by odor active value measurement and perceptual interactions. Food Chemistry. 2022;373 doi: 10.1016/j.foodchem.2021.131607. [DOI] [PubMed] [Google Scholar]

Associated Data

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

Supplementary Materials

Supplementary data 1
mmc1.docx (246.6KB, docx)

Data Availability Statement

Data will be made available on request.

Articles from Food Chemistry: X are provided here courtesy of Elsevier

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