Journal of Oleo Science Copyright ©2020 by Japan Oil Chemists’ Society J-STAGE Advance Publication date : August 13, 2020 doi : 10.5650/jos.ess20084 J. Oleo Sci. Study on the Fatty Acids, Aromatic Compounds and Shelf Life of Paeonia ludlowii Kernel Oil Chao-Qi Zhang1, Yuan-Jiang Xu1, 2, Ya-Zhou Lu1, Lian-Qiang Li1, Xiao-Zhong Lan1＊ , and Zheng-Chang Zhong1＊ 1 TAAHC-SWU Medicinal Plant Joint R&D Centre, Tibetan Collaborative Innovation Centre of Agricultural and Animal Husbandry Resources, Food Science College, Xizang Agricultural and Animal Husbandry University, Nyingchi of Tibet 860000, CHINA 2 Research Institute of Tibet Plateau Ecology, Tibet Agriculture & Animal Husbandry University, Nyingchi of Tibet 860000, CHINA Abstract: To determine the food potential of Paeonia ludlowii D.Y.Hong (P. ludlowii) kernel oil, in this study, we analysed the fatty acid composition and volatile components of this oil, compared the antioxidant effects of two natural antioxidants on it, and then predicted its shelf life at room temperature (25℃). The results showed that P. ludlowii kernel oil mainly contained 20 fatty acids, of which linoleic acid, oleic acid and other unsaturated fatty acid contents together made up 86.99%. The aromatic composition of the crude P. ludlowii kernel oil was analysed, and 34 aromatic compounds were obtained, including 5 lipids (2.30%), 9 alcohols (12.64%), 6 aldehydes (14.67%), 2 alkanes (1.30%), 5 acids (2.70%), 1 ketone (0.41), 2 alkenes (39.12%) and 4 other substances (26.85%). The effects of the antioxidants were ranked as follows: 0.04% tea polyphenols + crude oil > 0.04% bamboo flavonoids + crude oil > crude oil. In addition, the shelf lives at room temperature (25℃) of each kernel oil-antioxidant mixture were 200.73 d, 134.90 d and 131.61 d, respectively. Overall, these results reveal that P. ludlowii kernel oil is a potential candidate for a new high-grade edible oil, and its development has broad application prospects. Key words: Paeonia ludlowii kernel oil, unsaturated fatty acids, aromatic substance, shelf life, natural antioxidants 1 Introduction Local Tibetans began to treat gynaecological ailments, In 1936, the Englishman Ludlow discovered Paeonia skin diseases, and cardiovascular and cerebrovascular dis- ludlowii during his investigation in Tibet. In 1953, he pub- eases with the root bark of P. ludlowii hundreds of years lished an article in the British "Botanical Magazine" naming ago9）. In recent years, compounds from P. ludlowii have Paeonia ludlowii1）. It is a deciduous shrub of the genus shown strong anti-tumour10－12）, anti-inflammatory13）, and Paeonia in the family Ranunculaceae, a subspecies of other activities. Therefore, more efforts should be devoted Paeonia delavayi, and it is endemic to Tibet2）. It is dis- to the propagation of P. ludlowii in the future to change tributed only in a narrow range of approximately 100 km in its endangered status and allow P. ludlowii to fulfil its im- length in Brahmaputra Canyon at an altitude of 2900～ portant medicinal and edible potential as soon as possible. 3200 m; it is one of the eight peony species in China3, 4）. To the author's knowledge, a detailed study of the chem- However, the distribution range of Paeonia ludlowii is ical composition and aromatic substances of P. ludlowii narrow, its population is small, and it is considered endan- kernel oil and a prediction of its shelf life has not been re- gered, as it is included in the "Chinese Red List of Species"5, 6）. ported in the literature. Therefore, this work set out to de- China issued the“ Announcement of the Ministry of Health termine the fatty acid composition and aromatic composi- on Approving Acer truncatum kernel oil and Peony seed tion of this oil by gas chromatography. Then, the OXITEST oil as New Food Resources” on March 22, 2011, approving （an oil oxidation analyser adopted by AOCS, CD 12c-16） Peony seed oil as a new food resource7）; thus, peony seed method was used to determine the oxidation stability of P. oil has officially become an edible oil from a woody plant in ludlowii kernel oil with different natural antioxidants. China. According to the literature, P. ludlowii can be used Then, the shelf life of the oil at room temperature（25℃） as a new material for the development of oil peony variet- was inferred, and the effects of different natural antioxi- ies8）. dants in P. ludlowii kernel oil were studied. The results ＊Correspondence to: Xiao-Zhong Lan; Zheng-Chang Zhong, TAAHC-SWU Medicinal Plant Joint R&D Centre, Tibetan Collaborative Innovation Centre of Agricultural and Animal Husbandry Resources, Food Science College, Xizang Agricultural and Animal Husbandry University, Nyingchi of Tibet 860000, CHINA E-mail: [email protected] (XL); [email protected] (ZZ) Accepted May 12, 2020 (received for review March 30, 2020) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs 1 C.-Q. Zhang, Y.-J. Xu, Y.-Z. Lu et al. provided here may provide a reliable theoretical basis for tion source（EI）; ionization energy: 70 eV; transmission line quality evaluation of this oil, the influence of different shelf temperature: 280℃; ion source temperature: 230℃; life durations on its content of unsaturated fatty acids and solvent delay: 5 min; scanning mode: selected ion scanning the changes in its aromatic components, and the effects （SIM）. and mechanisms by which temperature change causes the 2.4.2 Sample methyl esterification changes in its two antioxidant components. Samples were weighed to 0.5 g and placed into 50 mL centrifuge tubes; then, 5 mL n-hexane and 15 mL of 10％ acetyl chloride - methanol solution were added, the bottle mouth was sealed, and the samples were incubated for 2 h 2 Experimental Details at 80℃ in a water bath response with shaking once every 2.1 General 20 min. Then, the samples were removed and cooled at Gas chromatography-mass spectrometry instrument: room temperature, and 10 mL 6％ sodium carbonate and 5 Thermo TRACE GC Ultra - DSQ II; ultrapure water instru- mL n-hexane were added. After 30 min oscillation, the su- ment: Beijing Puri General Instrument Co., Ltd., Gwa-un; pernatant was removed and passed through a 0.22 m filter analytical balance, Mettler Toledo Instrument Co., Ltd., membrane. When the concentration was too high, it was al204-ic, sensitivity 0.0001 g; LYNX4000 high speed centri- diluted it 100 times and then tested. Blank test: blank fuge, Thermo Fisher Technology Co., Ltd.; R-1001vn rotat- samples were subjected to the same protocol as the ing evaporator, Zhengzhou Great Wall Technology Industry samples except that no samples were included. and Trade Co., Ltd.; Xlw-1500y crusher, Yongkang Xin Longwei Industry and Trade Co., Ltd.; VELP OXITEST oil 2.5 Analysis of volatile flavour substances in P. ludlowii oxidation analyser, VELP Scientifica SRL, Italy. kernel oil samples 2.5.1 Extraction of volatile flavour compounds from P. 2.2 Chemicals ludlowii kernel oil Unless otherwise stated, the reagents used in this Five grams of P. ludlowii kernel oil was weighed and method were analytically pure, and the water was ultra- placed in the bottom of a headspace bottle. The extraction pure. Hexane（pure by chromatography）, acetyl chloride needle was aged to ensure the removal of any volatile com- （98％）, n-heptane（pure by chromatography）, methanol ponents that might have been adsorbed, and the aged ex- （pure by chromatography）, anhydrous sodium sulfate, and traction needle was inserted into the headspace bottle by sodium carbonate were purchased from Shanghai McLean pushing the quartz fibre head through the handle and ex- Biochemical Technology Co., Ltd. Bamboo leaf flavonoids posing it to the upper part of the gas in the headspace （40％ purity）and tea polyphenols（98％ purity）were pur- bottle. One millilitre of the upper gas was taken from the chased from Shanghai Yuanye Biotechnology Co., Ltd. sample. The headspace bottle was placed in a water bath at a constant temperature of 55℃ for extraction for 30 min 2.3 Plant material and stirred at 200 rpm/min. Then, the quartz fibre head P. ludlowii kernels were collected in Mirui township, was pushed back into the needle while pulling it out, the Nyingchi city, Tibet, in October 2018 and identified as P. sample was inserted into the GC-MS sampler, and the in- ludlowii kernels by Professor LAN Xiaozhong, School of strument was set to collect data. Food Science, Tibet Agriculture and Animal Husbandry GC-MS analysis conditions. University. P. ludlowii kernels were obtained by removing Chromatographic conditions: chromatographic column the black outer kernel coats of P. ludlowii kernels and methylpolysiloxane capillary column（50 m×0.32 mm×0.5 then pressed after drying. μm）. The inlet temperature was 230℃, the carrier gas（He） flow rate was 1.0 mL/min, and the shunt ratio was 10:1. 2.4 Fatty acid composition analysis The heating procedure of the column temperature box was 2.4.1 GC-MS conditions as follows: the initial temperature was 40℃, the tempera- Chromatographic column: HP-WAX; column length: 30 ture was maintained for 3 min, and the temperature was m; internal diameter: 0.25 mm; film thickness: 0.25 μm. raised to 230℃ at 5 degrees/min and then maintained for 1 Inlet temperature: 270℃. Programmed temperature rise: min. The solvent delay time was 3 min. the initial column temperature was 40℃; it was maintained Mass spectrometry conditions: detection method: mass for 1 min, raised to 210℃ at 7℃/min, maintained for 5 min, scanning method, 35 m/z-600 m/z. Ionization mode: EI and then raised to 240℃ at 1.5℃/min.