Roasted tree peony (Paeonia ostii) seed oil: Benzoic acid levels and physicochemical characteristics

Figures & data

Table 1. Physiochemical characteristics of TPSO with different roasting temperatures

	Roasting temperature (°C)
Parameter	Control	120	130	140	150
L*	14.5 ± 0.2d	13.1 ± 0.1c	12.4 ± 0.2a	12.7 ± 0.2b	13.1 ± 0.2c
a*	8.3 ± 0.4a	8.9 ± 0.4a	8.7 ± 0.6a	9.0 ± 0.1a	9.1 ± 0.3a
b*	10.0 ± 0.4b	9.7 ± 0.3ab	9.3 ± 0.3a	9.0 ± 0.1b	9.8 ± 0.3ab
AV	1.0 ± 0.02a	1.2 ± 0.01b	1.7 ± 0.04c	1.9 ± 0.01d	2.3 ± 0.01e
C16:0	5.4 ± 0.01a	5.5 ± 0.1bc	5.5 ± 0.1c	5.4 ± 0.01ab	5.4 ± 0.01abc
C18:0	1.5 ± 0.01a	1.5 ± 0.01a	1.5 ± 0.02a	1.5 ± 0.03a	1.4 ± 0.1a
C18:1	24.2 ± 0.01a	24.7 ± 0.2b	24.7 ± 0.1b	24.6 ± 0.1b	24.7 ± 0.1b
C18:2	24.2 ± 0.01a	24.3 ± 0.4a	24.4 ± 0.3a	24.0 ± 0.2a	24.0 ± 0.03a
C18:3	44.8 ± 0.01a	44.1 ± 0.5a	44.0 ± 0.4a	44.5 ± 0.3a	44.5 ± 0.1a
DPPH	32.2 ± 1a	34.8 ± 0.3b	38.2 ± 1c	42.1 ± 2d	45.4 ± 1e
ABTS	16.4 ± 3a	18.6 ± 3a	28.7 ± 4b	43.9 ± 2c	52.7 ± 2d
Total phenols	63.9 ± 4a	37.8 ± 2b	41.6 ± 2b	40.5 ± 1b	49.6 ± 2c

Different letters in the same row represented significant differences (p < 0.05). AV was expressed as mg KOH/g oil; DPPH and ABTS were expressed as µg trolox equivalent/mL methanolic extract; total phenols was expressed as µg gallic acid equivalent/mL methanolic extract. Oil obtained from unroasted peony seeds was used as a control.

Table 2. Volatile compounds of TPSO with different roasting temperatures

					Relative concentrations (mg/kg oil)^D
		RI^A			Roasting temperature (°C)
No.	Compounds	Wax	Rtx-5ms	ID^B	Control	120	130	140	150
	Pyrazines
1	2-methylpyrazine	1267	781	RI,MS	ND^C	ND	1.3 ± 0.1a^E	5.3 ± 0.4b	14.1 ± 1c
2	2,6-dimethylpyrazine	1330	894	RI,MS	ND	ND	8.6 ± 0.04a	21.2 ± 2b	42.8 ± 2c
3	2-ethyl-6-methylpyrazine	1394	994	RI,MS,RS	ND	ND	1.1 ± 0.2a	4.1 ± 0.7b	9.3 ± 1.3c
4	trimethylpyrazine	1406	1008	RI,MS	ND	ND	7.8 ± 0.2a	13.5 ± 1b	24.5 ± 2c
5	2-ethenyl-6-methylpyrazine	ND	984	RI,MS	ND	ND	0.7 ± 0.1a	1.8 ± 0.2b	3.1 ± 0.3c
6	3-ethyl-2,5-dimethylpyrazine	1448	1107	RI,MS	ND	ND	5.9 ± 0.3a	12.4 ± 2b	21.7 ± 2c
7	ethylpyrazine	1337	881	RI,MS	ND	ND	ND	0.6 ± 0.2	1.8 ± 0.1
8	2,3-dimethylpyrazine	1349	894	RI,MS	ND	ND	ND	0.9 ± 0.2	2.9 ± 0.2
9	2,6-diethyl-3-methylpyrazine	ND	1206	RI,MS	ND	ND	ND	1.0 ± 0.1	2.1 ± 0.1
	Pyrrole derivates
10	2-acetylpyrrole	ND	1035	RI,MS	ND	ND	1.6 ± 0.1a	3.6 ± 0.4b	5.5 ± 0.6c
	Alcohols
11	(Z)-hex-3-en-1-ol	1383	868	RI,MS,RS	ND	0.8 ± 0.1	ND	ND	ND
12	1-hexanol	ND	860	RI,MS,RS	ND	0.4 ± 0.1	ND	ND	ND
13	1-octen-3-ol	ND	969	RI,MS	ND	0.3 ± 0.02	ND	ND	ND
	Phenols
14	eugenol	1392	nd	RI,MS,RS	ND	0.4 ± 0.1a	0.4 ± 0.1a	0.6 ± 0.3a	0.6 ± 0.1a
15	methyl eugenol	ND	1361	RI,MS	ND	0.3 ± 0.01a	0.3 ± 0.03a	0.5 ± 0.02b	0.5 ± 0.1b
16	phenol	ND	901	RI,MS	ND	ND	ND	1.0 ± 0.2	1.3 ± 0.1
	Furan derivatives
17	4-hydroxy-2,5-dimethyl-3(2H)- furanone	2043	1022	RI,MS	ND	ND	3.7 ± 0.5a	8.9 ± 0.6b	16.6 ± 0.1c
18	2-methyloxolan-3-one	ND	821	RI,MS	ND	ND	ND	0.8 ± 0.02	1.4 ± 0.2
19	5-methyl-2-furanmethanol	1730	975	RI,MS	ND	ND	ND	1.0 ± 0.2	1.9 ± 0.2
20	5-methyl furfural	1586	920	RI,MS	ND	ND	ND	ND	1.8 ± 0.1
	Aldehydes
21	hexanal	806	ND	RI,MS	ND	0.2 ± 0.02	0.5 ± 0.02	ND	ND
22	phenylacetaldehyde	ND	1081	RI,MS	ND	0.9 ± 0.2a	7.5 ± 0.3b	8.6 ± 0.5c	8.5 ± 0.03c
23	benzaldehyde	1538	ND	RI,MS,RS	ND	0.2 ± 0.004a	0.3 ± 0.01b	0.3 ± 0.003c	0.3 ± 0.003d
24	furfural	1474	831	RI,MS,RS	ND	ND	0.5 ± 0.1a	1.4 ± 0.3b	3.4 ± 0.1c
25	2-phenyl-2-butenal	ND	1265	RI,MS	ND	ND	0.6 ± 0.1a	1.2 ± 0.1b	2.5 ± 0.1c
	Ketones
26	2,3-dihydro-3,5-dihydroxy- 6-methyl-4(H)-pyran-4-one	2266	1269	RI,MS	ND	0.4 ± 0.2a	24.6 ± 2b	54.9 ± 0.8c	83.8 ± 4d
27	2,3-pentadione	ND	790	RI,MS	ND	ND	0.5 ± 0.2a	1.3 ± 0.3b	2.1 ± 0.2c
28	acetoin	ND	717	RI,MS	ND	ND	1.1 ± 0.2a	0.9 ± 0.1a	1.7 ± 0.1a
29	3-methyl-1,2-cyclopentanedione	ND	1003	RI,MS	ND	ND	ND	0.5 ± 0.2	2.1 ± 0.1
30	hydroxyacetone	1305	ND	RI,MS	ND	ND	1.4 ± 0.03a	2.7 ± 0.03b	5.0 ± 0.1c
31	3-hydroxy-2-methyl-4H-pyran-4-one	1980	1063	RI,MS	ND	0.6 ± 0.2a	3.3 ± 0.4b	8.5 ± 0.6c	16.5 ± 3d
32	1-(6-methylpyrazin-2-yl)ethanone	ND	1130	MS	ND	ND	ND	2.2 ± 0.1	5.7 ± 0.4
	Acids
33	benzoic acid	2407	1150	RI,MS,RS	0.1 ± 0.1a	22.0 ± 6a	327.5 ± 40b	564.3 ± 10c	942.8 ± 70d
34	hexanoic acid	1854	ND	RI,MS,RS	ND	ND	0.1 ± 0.001a	0.1 ± 0.002b	0.1 ± 0.001c
35	acetic acid	1454	ND	RI,MS,RS	ND	0.8 ± 0.01a	4.8 ± 0.01b	8.2 ± 0.1c	15.5 ± 0.2d
36	4-hydroxybutyric acid	1648	1018	RI,MS	ND	ND	0.6 ± 0.05a	2.5 ± 0.2b	5.8 ± 0.5c
	Alkenes
37	α-pinene	ND	948	RI,MS	0.3 ± 0.1	0.2 ± 0.04	ND	ND	ND
38	β-myrcene	ND	958	MS	0.4 ± 0.03	0.4 ± 0.05	ND	ND	ND
	Others
39	anethole	ND	1190	MS	0.2 ± 0.03a	3.4 ± 0.3b	4.5 ± 0.2c	4.8 ± 0.1c	5.9 ± 0.7d
40	methyl anthranilate	2243	ND	RI,MS	1.2 ± 0.03c	1.2 ± 0.01c	1.1 ± 0.02b	1.1 ± 0.02a	1.1 ± 0.01a
41	toluene	ND	794	RI,MS	0.1 ± 0.02	ND	ND	ND	ND
42	methyl benzoate	1637	1060	RI,MS	ND	ND	1.9 ± 0.1a	4.0 ± 0.3b	8.8 ± 1c

^ARetention indices were determined by using n-alkanes (C₇-C₂₄) on Rtx-5MS column and HP-Innowax column.tab

^BIdentification of the compounds, ‘RI, MS, RS ‘ means identified by RI, mass spectrum and authentic standard; ‘MS, RI’ means tentatively identified by mass spectrum and RI with the NIST library; ‘MS’ means tentatively identified by a mass spectrum of the NIST library.

^CND, not detected.

^DValues followed by different letters were significantly different at p< 0.05.

^EThe concentration given was equivalent to the internal standard (concentration of the IS: 4.88 mg/kg tree peony seed oil).

Table 3. Benzoic acid content of TPSO roasted at different temperatures

Roasting temperature (°C)	Concentration (mg/L)±SD
control	2.95 ± 0.1a
120	26.8 ± 0.3b
130	57.8 ± 0.5c
140	103.4 ± 0.2d
150	162.8 ± 0.3e

Different letters in the same row represented significant differences (P <0.05).

Figure 1. Total ion chromatograms of the volatiles formed with different roasting temperatures of TPSO. a. with HP-Innowax column. b. with Rtx-5MS column

Figure 2. Typical chromatogram of benzoic acid standard at a concentration of 50 mg/L a. and oil sample roasted at 150°C b. The detector wavelength were both set at 230 nm