Journal of Oleo Science Copyright ©2019 by Japan Oil Chemists’ Society J-STAGE Advance Publication date : July 10, 2019 doi : 10.5650/jos.ess19032 J. Oleo Sci. Comparison of the Changes in Fatty Acids and Triacylglycerols between maruadsi and Trichiurus lepturus during Salt-dried Process Yanyan Wu1† , Qiuxing Cai1,2,3† , Laihao Li1,＊ , Yueqi Wang1,3, and Xianqing Yang1 1 South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences; Key Lab of Aquatic Product Processing, Ministry of Agriculture and Rural Affairs of the People’s Republic of China, Guangzhou 510300, CHINA 2 Guangxi College and Universities Key Laboratory Development and High-value Utilization of Beibu Gulf Seafood Resources, College of Food Engineering, Beibu Gulf University, Qinzhou 535011, CHINA 3 College of Food Science and Engineering, Ocean University of China, Qingdao 266000, CHINA † Yanyan Wu and Qiuxing Cai contributed equally to first joint authors.

Abstract: In order to reveal changes in fatty acids and triglycerides during the pickling process of white- fleshed and dark-fleshed with high-fat, to compare the changes of triacylglycerols (TAGs) and fatty acids (FAs) in round scad (Decapterus maruadsi, dark-fleshed) and hairtail (Trichiurus lepturus, white- fleshed) during salt-dried processing, ESI-MS/MS and GC-MS techniques were used to quantify. Lipid oxidation was evaluated via peroxide values (POVs), and thiobarbituric reactive substances (TBARS). A total of 31 and 27 FAs, 45 and 44 TAGs were quantified in round scad and hairtail, respectively. DHA (C22:6n3), palmitic acid (C16:0), stearic acid (C18:0), and oleic acid (C18:1n9) were the main FAs in round scad. POO (16:0/18:1/18:1), PPO (16:0/16:0/18:1), POD (16:0/18:1/22:6), and PPaO (16:0/16:1/18:1) were dominant TAGs in both . Salt-dried processing significantly affected (p < 0.001) 7/5 FAs and 24/29 TAGs in round scad/hairtail. MUFAs changed significantly (p < 0.05) in dark-fleshed round scad; only SFAs and PUFAs changed in white-fleshed hairtail. Both species exhibited near-identical TAG compositions with different variation trends. More significant changes were observed in FAs at the half-dried stages and in TAGs (p < 0.05) at the salted stage. This coincided with the changing stages of POV and TBARS values that also increased significantly (p < 0.05) at the salted stages but peaked at the half-dried stages of both species.

Key words: round scad (Decapterus maruadsi) and hairtail (Trichiurus lepturus), salt-dried processing, fatty acids; triacylglycerols, lipid oxidation

1 Introduction rated fatty acid（PUFAs）such as DHA（C22:6n3）and EPA Hairtail（Trichiurus lepturus; white-fleshed）and round （C20:5n3）that are important for human health5）. However, scad（Decapterus maruadsi, dark-fleshed）are two fish PUFAs are susceptible to physicochemical changes from species widely distributed in the China Sea. Their annual lipid oxidation that lead to sensorial and nutritional deteri- harvest（2016）was estimated at 108.72 and 60.09 million oration6）, which is a health concern. Growing evidence cor- tons, respectively, ranking first and third in the ranking of relates lipid oxidation products with chronic diseases（such marine fish production in China1）. They are processed into as asthma, atherosclerosis, Alzheimer’s disease, and rheu- food products, including salt-dried and stewed fish. In matoid arthritis7）. Studies have reported the degree of China, traditional salt-dried fish, prepared by marinating primary oxidation through peroxide value（POV）measure- and air-dry ripening2, 3）, is popular for its unique flavor. Pro- ments that determine hydrogen peroxide production8）. duction is still based on workers’ experience and little is Others quantify secondary oxidation products via thiobar- known on the biochemical changes in fish muscle. Research bituric reactive substances（TBARS）measurements9）. Free has focused on nitrites that form carcinogenic nitrosamines fatty acids（FAs）from lipolysis are the main precursors of during salting4）, while aspects, such as lipid oxidation, have volatile compounds10, 11）; thus, their relationship is notewor- been overlooked. Fish is rich in omega-3（n-3）polyunsatu- thy. Literature on lipid oxidation during salt-dried meat

＊Correspondence to: Laihao Li, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences; Key Lab of Aquatic Product Processing, Ministry of Agriculture and Rural Affairs of the People’s Republic of China, No 231 of Xingangxi Road, Guangzhou 510300, CHINA E-mail: [email protected] Accepted May 7, 2019 (received for review January 30, 2019) 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 Y. Wu, Q. Cai, L. Li et al.

processing includes studies on dried cured goose12）and using the boron-trifluoride（14％ methanol, w/w）-catalyzed Cantonese sausage13）. However, studies on salt-dried fish esterification protocol20）. The FAMEs were measured using have not been reported to date. Moreover, comprehensive GC-MS（QP-2010, Shimadzu, Japan）. GC was performed on analyses combining lipid oxidation and FAs are rare. a DB-5MS capillary column（30 m×0.25 mm, 0.25 μm, Notably, the FA composition in fish during salt-drying was Agilent Technologies, Santa Clara, CA, USA）. GC-MS was investigated14）during lipolysis and lipid oxidation studies. operated as described by Hao21）, with some modifications. However, few studies have focused on quantify triacylglyc- Samples（1.0 μL）were injected in split mode（20:1）. Helium AGerols（T ）neutral lipids. MS protocols requiring simple was used as the carrier gas（flow rate, 0.5 mL/min; injector sample preparations were developed to analyze lipid com- temperature, 250℃; ion source, 230℃）. The temperature position in seafood15－17）. Yet, these protocols have rarely was set from 35 to 230℃ at a rate of 5℃/min. Mass spectra been applied to investigate lipids in salt-dried fish. This were recorded at three scans/s（50–500 m/z）. Chromato- study evaluates lipid oxidation using analytical indices grams and mass spectra were evaluated using the NIST05 （POV, TBARS）and profiles FAs（GC-MS）and TAGs database（National Institute of Standards and Technology, （ESI-MS/MS）formed in salt-dried round scad and hairtail Gaithersburg Library, MD, USA）. The measured FAs were

during processing. calibrated using standard alkanes（C12–C28; purity＞96％） （Anpel Laboratory Technologies, Inc., Shanghai, China）, with retention times converted into RI（Retention index） values22）. FA quantities were estimated by comparing their 2 Experimental peak areas with those of undecanoic acid（C11:0）as internal 2.1 Sampling protocol standard. Round scad（300–400 g/fish）and hairtail（600–800 g/fish） The lipid extract nutritional quality was assessed using were purchased from a local Vanguard Supermarket three different indicators: PUFA/SFA ratio, n-6/n-3（PUFA） （Guangzhou, China）, and delivered and stored at 0℃ and PI（Polyene Index）, PI＝（ C20:5＋C22:6）/C16:0, PI within 48–72 h of harvest to preserve freshness. The showed PUFA damage23）. were eviscerated and prepared following the code of prac- tice for salted fish（SC/T 3038-2006, Chinese Aquaculture 2.5 Determination of TAG composition Industry Standards）and method of Wu3）. Briefly, the fish An automated ESI-MS/MS approach was used for TAG was cured with 20/100 g coarse salt, marinated in saturated analysis. The samples were dissolved in 1 mL chloroform. brine at 20℃, rinsed with fresh water, and finally dried at An aliquot（4–10 μL）of extract in chloroform was analyzed 28（±2）℃ and 65％ RH. Each kind of fishes were divided and a precise amount of internal standard（Avanti Polar into five parts: 0 d（raw material）, 2 d（salting stage）, 3 d Lipids）was added（0.31 nmol tri17:1 TAG）. The sample/in- （rinsed）, 4 d（half-dried）, and 5 d（final product）. Five tails ternal standard mixtures were combined with solvents to of fish were taken for each part. 150 g dorsal muscles ob- form a chloroform/methanol/300-mM ammonium acetate tained from each part sample were minced and stored at ratio in water of 300/665/35 and a final volume of 1.4 mL. －18℃ for further analyses. Unfractionated lipid extracts were introduced by contin- uous infusion into the ESI source on a triple quadrupole 2.2 Lipid oxidation measurements MS（API4000, Applied Biosystems, Foster City, CA）. POVs（meq/kg sample）were measured by colorimetric Samples were introduced（30 μL/min）via an autosampler determination using ferric thiocyanate assay（Chinese Na- （LC Mini PAL, CTC Analytics AG, Zwingen, Switzerland） tional Standard, GB/T 5009.37-2003）. TBARS were fitted with an injection loop on the ESI needle. TAGs were ＋ measured（mg MDA/kg sample）by a method described by detected as［M＋NH4］ ions from a series of NL（Neutral Vyncke18）, with minor modifications. 1,1,3,3-Tetraethoxy- loss）scans. The scans targeted losses of various FAs as propane was used as MDA standard. neutral ammoniated fragments: NL 285.2（17:1, TAG inter- nal standard）, NL 243.2（14:1）, NL 245.2（14:0）, NL 273.2 2.3 Lipid extraction （16:0）, NL 271.2（16:1）, NL 301.2（18:0）, NL 299.2（18:1）, Lipids were extracted from the minced material of each NL 297.2（18:2）, NL 299.2（18:1）, NL 301.2（18:0）, NL 319.2 stage with a chloroform/methanol（2:1, v/v）solution accord- （20:5）, NL 321.2（20:4）, NL 323.2（20:3）, NL 325.2（20:2）, ing to Folch19）. The extracts were dried under an N-EVAP NL 345.2（22:6）, NL 347.3（22:5）, and NL 349.3（22:4）. Scan system（Organomation, Berlin, MA, USA）with nitrogen flow speed, 100 u/s; collision energy（nitrogen）, ＋20 V; declus- to determine the TL（total lipid）extract; one sample was tering potential, ＋100 V; entrance potential, ＋14 V; exit used for FA determination by GC-MS. potential, ＋14 V. Fifty continuum scans were averaged in MCA mode. Collision gas pressure, low; mass analyzers, 0.7 2.4 Analysis of FA composition by GC-MS μ full width at half height; source temperature（heated The FAs in the TL extract were transesterified to FAMEs nebulizer）, 100℃; interface heater, on; electrospray capil-

2 J. Oleo Sci. Fatty Acids and Triacylglycerols of Different Fishes during Salt-dried Process

lary, ＋5.5 kV; curtain gas, 20（arbitrary units）; and two ion source gases, 45（arbitrary units）. The background in each spectrum was subtracted, the data were smoothed, and peak areas were integrated using a custom script and Applied Biosystems Analyst software. For TAG analysis, data from NL scans were corrected for overlapping isotopic variants（A＋2 peaks）within the spectra. The ionization efficiency varied in acylglycerols with different fatty acyl groups（Han and Gross, 2001）, thus, the MS responses of the TAG species/internal stan- dard ratio was not directly proportional to the TAG content. TAG amounts were therefore expressed as relative mass spectral signal/mg dry weights, where a signal of 1.0 Fig. 1 Changes in peroxide values（POV）during salted- represented a signal equivalent to 1 nmol of tri17:1TAG（in- dried processing of round scad（Decapterus ternal standard）. Maruadsi）and hairtail（Trichiurus lepturus）. Means±standard deviations（SDs, n＝5）. Samples 2.6 Statistical analysis with different letters in the same curve exhibit Experiments were conducted with five replicates（n＝5）. significant differences（p＜0.05）in measured Data were analyzed using JMP 15.0 software（SAS Institute, parameters. Inc., Cary, NC, USA）. ANOVA（Duncan’s multiple range tests）was performed to evaluate the influence of process- ing（L, LY, LP, LG, and LC）on the proximate compositions, lipid oxidation parameters, and FA and TAG profiles of each extract. Differences in means at the p＜0.05 level of significance were determined by Tukey’s HSD test. Figures were drawn using OriginPro 8.5 software（OriginLab, Inc., Northampton, MA, USA）.

3 Results 3.1 POV and TBARS analyses POV levels were low in both raw round scad and hairtail （0.23 and 0.11 meq/kg sample, respectively）, increased Fig. 2 Chan ges in TBARS value during salted-dried significantly（p＜0.05）during the rinsed（round scad）and processing of round scad（Decapterus maruadsi） half-dried（hairtail）stages, and reached their highest values and hairtail（Trichiurus lepturus）. Means± （1.20 and 1.34 meq/kg sample, respectively）at the half- standard deviations（SDs, n＝5）. Samples with dried stage（Fig. 1）. Subsequently, both POV values de- different letters in the same curve exhibit creased significantly（p＜0.05）. The TBARS value of round significant differences（p＜0.05）in measured scad showed a significant increase from the raw material parameters. stage to the pickling stage（p＜0.05）, while the pickling stage to the drying stage increased although not significant during salt-dried processing are presented in Tables 1 and （p＞0.05）, and then significantly increased again after the 2. 31 and 27 FAs were detected in round scad and hairtail. finished product stage（p＜0.05）; While the TBARS value The main components of SFA, MUFA and PUFA in round of hairtail showed a significant increase from the raw mate- scad comprised palmitic acid（C16:0）, oleic acid（C18:1n9） rial stage to the pickling stage（p＜0.05）, although there and DHA（C22:6n3）（ Table 1）, however in hairtail com- was a decrease from the pickling stage to the rinsing stage, prised stearic acid（C18:0）, oleic acid（C18:1n9）and EPA but not significant（p＞0.05）, and then to the drying stage （C20:5n3）（ Table 2）. Furthermore, the combined EPA and was significant. It increased（p＜0.05）, and then decreased DHA content was 155.15 mg/g and 38.54 mg/g in raw round significantly（p＜0.05）（ Fig. 2）. scad and hairtail, accounting for 35.55％ and 19.59％ of the total FAs. Table 1 displays changes in FA composition 3.2 The effect of salt-dried process on fatty acid composi- during salt-dried processing of round scad. ANOVA re- tion of round scad and hairtail vealed that processing significantly affected（p＜0.001）the The profiles of FAs found in round scad and hairtail total（∑）PUFAs, ∑MUFAs, and C14:0, C15:0, C16:1n7,

3 J. Oleo Sci. Y. Wu, Q. Cai, L. Li et al.

Table 1 Changes in the FA composition（mg/g）of round scad（D. maruadsi）during salt-dried processing.

Retention Abundance (mg/g) in round scad (D. maruadsi) Fatty acids RI SIG time (min) Raw Salted Rinsed Half-dried Final product C12:0 10.365 1493 * 0.29±0.12b 0.46±0.06ab 0.37±0.03ab 0.52±0.05ab 0.66±0.13a C13:0 12.282 1591 * 0.13±0.01b 0.12±0.04b 0.13±0.00b 0.28±0.04a 0.18±0.01ab C14:0 14.37 1689 *** 8.05±0.92c 18.39±0.09b 12.71±0.71b 18.18±1.56a 19.16±0.94a C15:0 16.572 1786 *** 3.47±0.13c 3.15±0.12c 4.05±0.01b 5.95±0.12a 1.19±0.12b C16:0 18.843 1884 ** 74.61±9.98b 75.42±6.45b 77.5 ±0.56b 114.1 ±3.93a 102.31±0.74ab C17:0 21.085 1981 ** 7.88±0.02abc 5.66±0.11c 6.48±2.03bc 10.56±0.49ab 11.79±1.13a C18:0 23.373 2079 * 70.68±2.97ab 60.01±3.48b 55.91±5.73b 85.52±5.74a 67.37±1.84b C19:0 26.163 2177 ** 2.97±0.46ab 1.74±0.26b 1.62±0.13b 3.69±0.76ab 4.48±0.91a C20:0 28.961 2230 n. s. 2.28±0.22a 1.82±0.08a 1.55±0.08a 2.94±0.05a 3.16±0.88a C21:0 31.553 2375 ND 0.29±0.02 ND 0.75±0.03 0.35±0.08 0.44±0.01 C22:0 34.098 2475 ** 1.33±0.04ab 0.81±0.04b 0.66±0.11b 1.33±0.08ab 1.64±0.35a C23:0 36.670 2573 ND 0.26±0.02 ND ND 0.83±0.02 0.85±0.04 ∑SFA ** 171.96±14.34b 167.14±10.19b 161.31±7.81b 243.69±12.54a 192.04±1.47ab C14:1n3 14.102 1687 ND ND ND 10.18±0.3 0.17±0.02 0.11±0.01 C16:1n7 18.406 1882 *** 17.74±0.14c 13.59±1.58c 18.47±0.91c 40.96±2.74a 29.86±1.59b C16:1n10 20.007 1963 * 1.46±0.64b 1.66±0.12b 1.51±0.24b 3.45±0.39ab 4.96±1.01a C18:1n9 23.098 2085 ** 34.46±4.72c 62.39±1.5bc 79.74±0.47b 122.33±20.42a 75.45±0.48b C18:1n12 20.668 2068 ND ND 2.91±0.06 ND 0.49±0.01 3.19±0.05 C19:1n9 25.704 2175 ND ND ND ND 1.47±0.06 0.46±0.03 C20:1n9 28.213 2479 ND 0.67±0.04 6.12±0.96 6.48±0.04 ND ND C22:1n9 33.391 2560 ND ND ND 0.59±0.06 1.65±0.32 0.94±0.08 C24:1n9 39.498 2632 *** 2.33±0.26d 2.84±0.22cd 4.36±0.01bc 4.86±0.94b 8.37±0.33a ∑MUFA *** 58.53±6.24c 90.13±1.37bc 121.68±0.11b 177.14±17.69a 123.34±1.86b C16:3n6 18.015 1794 ND ND 1.16±0.06 ND ND 4.31±0.07 C18:2n6 22.538 1988 *** 9.32±0.26b 6.45±0.58b 11.34±0.44b 25.53±3.54a 8.34±0.47b C18:3n3 22.634 2053 * 0.52±0.02c 0.81±0.14c 1.27±0.12bc 2.59±0.01ab 3.63±0.73a C20:2n7 25.684 2272 *** 2.19±0.11b 1.08±0.01d 1.85±0.02c 2.18±0.01b 3.79±0.07a C20:3n7 22.307 2300 n. s. 1.28±0.07a 0.58±0.07a 1.66±0.09a 1.62±0.01a 1.66±0.88a C20:4n6 26.884 2474 * 17.57±1.97b 10.44±0.78b 12.45±0.05b 17.12±2.33b 25.64±2.59a C20:4n3 27.607 2477 * 17.42±0.71b 32.26±3.83ab 25.48±1.82ab 39.16±6.75a 28.03±2.81ab C20:5n3 27.043 2474 *** 26.39±4.81b 25.39±2.42b 30.63±1.97b 58.03±1.56a 51.56±0.62a C22:6n3 29.784 2576 ** 128.76±9.44a 143.92±7.72a 94.46±3.51b 136.81±11.01a 133.73±6.95a C22:5n3 32.216 2668 ND 2.46±0.48 ND 0.72±0.21 0.61±0.09 ND ∑PUFA *** 205.92±12.53bc 220.83±0.13b 181.25±0.93c 283.03±0.11a 256.35±8.55a ∑total ** 436.41±33.04c 478.06±11.66bc 464.25±6.76bc 703.86±30.11a 571.69±13.51b PUFA/SFA 1.20 1.32 1.12 1.16 1.33 n-6/ 0.15 0.04 0.16 0.18 0.18 n-3(PUFA) PI 2.08 2.24 1.61 1.71 1.81 Notes: a-d or A-D Means±SDs with different superscripts in a row differ significantly at different stages of processing (p＜0.05), n＝5; ND ＝not detected; SIG: Significance levels: *p＜0.05, ** p＜0.01, ***p＜0.001, n.s.＝not significant; RI: Retention index values, calculated according to the retention time of each FA.

4 J. Oleo Sci. Fatty Acids and Triacylglycerols of Different Fishes during Salt-dried Process

Table 2 Changes in the FA composition（mg/g）of hairtail（T. lepturus）during salt-dried processing.

Retention Abundance (mg/g) in hairtail (T. lepturus) Fatty acids RI SIG time (min) Raw Salted Rinsed Half-dried Final product C12:0 10.365 1493 * 0.54±0.04AB 0.35±0.07BC 0.61±0.01A 0.18±0.02C 0.25±0.07C C14:0 14.37 1689 *** 10.28±0.56A 8.55±0.92AB 6.16±0.03BC 4.64±0.09CD 2.34±0.04D C15:0 16.572 1786 n. s. 2.57±0.05A 2.51±0.33A 3.79±0.07A 4.41±0.87A 5.17±1.36A C16:0 18.843 1884 *** 13.51±0.22A 12.86±0.42A 11.35±0.04B 11.48±0.03B 10.42±0.18B C17:0 21.085 1981 ND 0.68±0.02 4.24±0.02 3.86±0.12 ND 1.59±0.32 C18:0 23.373 2079 * 30.28±3.87AB 25.68±3.83B 31.75±1.18AB 32.18±0.53AB 36.85±0.64A C19:0 26.163 2177 ** 0.78±0.17AB 0.6 ±0.14B 1.35±0.18A 1.09±0.03AB 1.27±0.27AB C20:0 28.961 2230 * 0.62±0.06AB 0.41±0.08B 0.83±0.06A 0.84±0.04A 0.75±0.02A C21:0 31.553 2375 ND ND ND 0.11±0.02 0.42±0.04 ND C22:0 34.098 2475 ND 0.23±0.02 0.17±0.04 0.33±0.01 ND 0.26±0.06 C23:0 36.670 2573 ND 0.78±0.13 ND ND ND 0.41±0.05 ∑SFA n. s. 60.24±5.33A 55.37±3.32A 60.14±2.01A 55.24±0.59A 59.31±4.20A C16:1n7 18.406 1882 n. s. 19.80±2.85A 13.19±0.76A 21.93±3.53A 15.69±2.79A 16.02±2.37A C16:1n9 28.391 1886 ND ND 1.92±0.13 0.82±0.024 ND 1.16±0.21 C16:1n10 20.007 1963 n. s. 2.44±0.09A 1.46±0.11A 2.65±0.07A 1.64±0.23A 2.19±0.75A C18:1n9 23.098 2085 ** 63.82±4.83A 58.55±4.87A 58.46±4.16A 52.43±0.59AB 42.87±1.06B C18:1n12 20.668 2068 ND ND ND 0.14±0.02 ND ND C20:1n9 28.213 2479 ND 0.64±0.15 0.25±0.04 0.68±0.06 4.24±0.13 ND C22:1n9 33.391 2560 ND 0.44±0.11 0±0 0.51±0.07 ND ND C24:1n9 39.498 2632 ND ND 0.72±0.07 0.37±0.02 ND 1.28±0.17 ∑MUFA ** 87.89±7.75A 77.94±5.84AB 86.49±7.44AB 74.56±1.96AB 64.14±4.12B C18:2n6 22.538 1988 * 4.23±0.68A 4.62±0.86A 4.15±0.14A 1.77±0.11B 2.67±0.12AB C18:3n3 22.634 2053 ND 0.29±0.04 ND ND ND 0.73±0.07 C20:2n7 25.684 2272 ND 0.43±0.02 ND 1.18±0.04 1.43±0.11 0±0 C20:3n7 22.307 2300 ** 0.85±0.08A 0.41±0.06B 0.84±0.07AB 0.82±0.18A 0.75±0.04AB C20:4n6 26.884 2474 *** 14.29±0.08A 8.54±1.85B 2.63±0.27C 2.49±0.69C 3.85±0.37C C20:5n3 27.043 2474 *** 34.42±0.03A 14.65±0.08B 14.4 ±3.38B 8.71±0.47C 3.36±0.05D C22:6n3 29.784 2576 *** 4.12±0.52BC 2.78±0.03C 6.62±9.23A 3.07±0.06C 5.78±0.45BC C22:5n3 32.216 2668 ND 0.76±0.28A 0.23±0.01A ND 0.62±0.14A 0.65±0.02A ∑PUFA *** 58.59±1.13A 31.03±2.82B 29.76±4.21B 18.22±0.02C 17.15±1.24C ∑total ** 196.73±12.65A 154.27±11.01AB 176.39±16.74AB 148.02±2.16B 140.59±8.85B PUFA/SFA 0.97 0.56 0.49 0.33 0.29 n-6/ 0.47 0.75 0.32 0.34 0.62 n-3(PUFA) PI 2.85 1.36 1.85 1.02 0.88 Notes: a-d or A-D Means±SDs with different superscripts in a row differ significantly at different stages of processing (p＜0.05), n＝5; ND ＝not detected; SIG: Significance levels: *p＜0.05, ** p＜0.01, ***p＜0.001, n.s.＝not significant; RI: Retention index values, calculated according to the retention time of each FA.

C24:1n9, C18:2n6, C20:5n3, and C20:2n7 contents. The stage（p＜0.05）. In the seven FAs altered（p＜0.001）by ∑MUFAs increased（p＜0.05）at the half-dried stage but processing, C16:1n7, C18:2n6, and C15:0 increased signifi- declined（p＜0.05）in the final product. Conversely, cantly（p＜0.05）at the half-dried stage and C15:0 also ac- ∑PUFAs first decreased significantly at the rinsed stage（p cumulated（p＜0.05）at the rinsed stage; however, they all ＜0.05）, and then increased significantly at the half-dried significantly diminished（p＜0.05）in the final product. Con-

5 J. Oleo Sci. Y. Wu, Q. Cai, L. Li et al.

versely, C20:2n7 decreased（p＜0.05）at the salted stage and accumulated continuously（p＜0.05）from the rinsed stage. C20:5n3 only increased significantly（p＜0.05）in the final product and half-dried stage, respectively, while C14:0 and C24:1n9 increased continuously（p＜0.05）from the salted and rinsed stage. Table 2 illustrates changes in FA composition during hairtail salt-dried processing. This caused highly significant changes（p＜0.001）in ∑PUFAs and C14:0, C16:0, C20:4n6, C20:5n3, and C22:6n3 contents. Furthermore, ∑PUFAs diminished（p＜0.05）at the salted and half-dried stages. The ∑PUFAs in salted herring14）were reported to decline（p＜0.05）at the drying stage, suggest- ing PUFA degradation due to oxidation; In the five FAs altered（p＜0.001）by processing, C20:4n6 and C20:5n3 Fig. 3 Changes in the total triacylglycerol amount during contents decreased（p＜0.05）during the salted stage and salt-dried processing of round scad（Decapterus subsequently diminished（p＜0.05）at the rinsed and half- maruadsi）and hairtail（Trichiurus lepturus）. dried stages, respectively. C16:0 and C14:0 only decreased Means±standard deviations（SDs, n＝5）. Samples （p＜0.05）at the half-dried stage and final product, respec- with different letters in the same curve exhibit tively. Conversely, the C22:6n3 content accumulated（p＜ significant differences（p＜0.05）in measured 0.05）at the rinsed stage and decreased（p＜0.05）at the parameters. half-dried stage. The PUFA/SFA ratio, n-6/n-3（PUFA）and PI were also ed by a combination of three FAs in order of the number of shown in Tables 1 and 2 of round scad and hairtail, respec- acyl-chain length and the degree of unsaturation. Apart tively. The PUFA/SFA ratio observed for round scad（1.12– from SLL（round scad）, the other species were consistent 1.33）was higher than for hairtail（0.29–0.97）. Tukey’s HSD and the TAG composition was similar in both species（Table analysis indicated no significant change（p＞0.05）in PUFA/ 3）. SFA ratio during round scad processing; that of hairtail de- Seven species of TAGs contained DHA（D）and EPA（E）at creased twice（p＜0.05）in the process. The afforded ratios 1552.9 and 101.3 nmol/mg, corresponding to 28.6％ and were lower than the FAO/WHO recommended values at the 24.9％ of the TAG amount in raw round scad and hairtail half-dried stage. An n-6/n-3 PUFA ratio ranged from 0.04 to （ESI-MS/MS）, respectively. Among these TAGs, 24 and 29, 0.18 in round scad and 0.32 to 0.75 in hairtail. Moreover, a respectively, were affected（p＜0.001）by salt-dried pro- significant difference（p＜0.05）was observed in both cessing. There were more species in hairtail, 19 of which species throughout processing. The PI（PUFA damage）in were common species. The TAGs comprised palmitic acid round scad ranged from 1.61 to 2.24; while it ranged from （P, 16:0）, stearic acid（S, 18:0）and oleic acid（O, 18:1）. PSD 0.88 to 2.85 in hairtail. A significant decrease in PI value and PPD（round scad）contained DHA, while PPE and PPaE was observed at the rinsed stage of round scad and at the in hairtail contained EPA. Tukey’s HSD revealed that 24 salted and half-dried stages of hairtail. TAGs in round scad significantly declined（p＜0.05）at the salted stage. PPaO, SOL, POA, OOL increased（p＜0.05）at 3.3 The effect of salt-dried process on TAG composition the same stage; their final amounts were lower than those of round scad and hairtail of the raw species. In hairtail, 29 TAGs accumulated（p＜ The TAG content in raw hairtail was 7.5％ of that in raw 0.05; MPO, PPPa, PaPaO, OPPa, PPO, PaOO, SPaO, POO, round scad（Fig. 3）. The TAG content declined（p＜0.05）at PSO, OOL, PSEt, and SSO）in the final product; the remain- the salted and half-dried stages and accumulated（p＜0.05） ing 17 TAGs were from the salted stage. Finally, their in the final product of round scad. It increased（p＜0.05）in amounts were much higher than those in the raw species. both the salted stage and final products. This difference Furthermore, these TAGs were all altered（p＜0.05）at the decreased in the final products of hairtail. salted stage; this was consistent with changes in POV and 42（round scad）and 41（hairtail）TAG species were de- TBARS; they also increased significantly（p＜0.05）at the tected. The acyl composition was consistent with that of salted stage in both species. marine and mammalian cells, including myristic（M, C14:0）, palmitic（P, C16:0）, stearic（S, C18:0）, oleic（O, C18:1）, linoleic（L, C18:2）, eicosapentaenoic（E, C20:5）, docosa- hexaenoic（D, C22:6）, arachidonic（A, C20:4）, palmitoleic （Pa, C16:1）, eicosatrienoic（Et, C20:3）, and eicosadienoic （Ed, C20:2）acids. TAG species in this paper are represent-

6 J. Oleo Sci. Fatty Acids and Triacylglycerols of Different Fishes during Salt-dried Process

Table 3 Changes in TAG（nmol/mg）of round scad（D. maruadsi）and hairtail（T. Lepturus）during salted-dried processing.

Abundance (nmol/mg) in round scad (D. maruadsi) Abundance (nmol/mg) in hairtail (T. Lepturus) TAG SIG Raw Salted Half-dried Final product SIG Raw Salted Half-dried Final product MPO ** 152.71±9.07a 79.45±5.86b 81.21±2.63b 112.52±17.49ab *** 21.59±6.25B 37.09±17.78B 21.96±3.17B 168.17±6.1A PPPa * 239.33±7.66a 212.07±33.59ab 135.22±1.78b 168.26±28.07ab *** 16.09±9.38B 55.77±25.34B 31.68±5.26B 200.98±12.69A PPP n. s 108.23±2.18a 82.35±14.18a 82.75±9.91a 85.49±0.97a ** 16.65±6.61B 30.71±14.67B 13.76±1.74B 85.11±10.62A PaPaO ** 29.43±3.08b 42.24±0.05a 14.83±2.03c 29.14±2.41b *** 2.33±0.32B 3.52±0.93B 2.29±0.13B 19.54±0.21A PPaL ** 51.18±0.35a 23.21±4.96b 20.92±0.81b 24.88±3.81b *** 5.02±0.04C 37.69±2.16A 2.74±0.68C 23.71±0.91B PPaO *** 368.14±15.96b 501.63±33.65a 166.66±0.08c 268.19±36.07bc *** 31.75±15.49C 96.53±44.86C 51.83±5.76C 400.97±22.93A PPL ** 29.89±0.65a 25.64±2.43a 15.16±1.32b 18.34±1.76b *** 3.69±0.41C 35.51±3.26A 4.99±0.52C 19.48±0.38B PPO * 442.14±24.26a 279.43±84.39ab 219.59±0.03b 297.32±21.34ab *** 40.84±16.68B 132.84±63.12B 62.76±3.53B 437.22±18.34A PPS ** 154.41±10.62a 81.71±22.11b 51.16±2.13b 58.65±7.54b ** 12.58±5.96B 46.85±20.02B 17.66±1.48B 111.79±16.55A PPaE ** 120.79±0.93a 92.42±4.93ab 68.26±1.83b 118.11±23.84a *** 5.81±0.73C 54.63±3.91A 11.01±0.43C 23.74±0.26B PPE ** 138.82±4.75a 109.58±9.73ab 71.03±0.83c 82.18±15.45bc *** 4.49±1.84C 79.18±9.76A 7.71±1.11C 30.93±1.63B PaOL *** 14.06±0.38a 6.42±0.69b 5.46±0.58b 4.95±1.21b ** 0.53±0.03B 2.02±1.08B 0.93±0.17B 5.36±0.54A PPA ** 53.92±0.11a 24.01±4.47b 16.54±1.46b 28.17±4.64b *** 7.89±1.68C 39.03±3.05A 3.92±0.05C 16.75±1.34B SPaL ND 17.35±1.10 27.31±7.63 ND ND ND ND 4.16±0.18 ND ND PaOO *** 132.83±2.21a 42.77±5.06c 39.04±1.81c 57.48±1.95b *** 5.53±2.87B 16.02±5.84B 9.89±0.24B 67.06±2.91A POL * 64.81±0.77a 30.16±7.43b 21.34±2.13b 34.41±2.16b *** 5.89±0.44C 43.97±3.47A 4.99±0.16C 33.24±0.28B SPaO *** 103.91±7.14a 29.19±1.16bc 24.74±4.28c 43.61±0.37b *** 7.55±2.05B 16.59±6.13B 11.36±1.04B 56.21±0.19A POO *** 1223.82±76.03a 1222.24±39.84a 271.41±33.27b 417.43±24.09b *** 66.43±31.98B 198.24±88.57B 90.35±4.04B 689.45±19.89A PSL *** 21.51±0.08a 9.25±2.68b 3.83±0.63b 8.21±0.83b *** 1.49±0.28C 18.02±1.14A 1.85±0.12C 11.33±0.32B PSO *** 208.83±4.31a 68.37±12.53b 42.45±12.13b 49.28±12.25b *** 18.78±3.74B 40.28±20.11B 19.58±0.12B 142.35±2.19A PSS *** 27.45±0.09a 10.83±1.44b 5.51±1.13c 5.56±0.02c *** 3.21±0.53C 9.35±2.33A 2.82±0.45C 16.83±0.05B PPaD ** 245.74±13.27a 144.23±27b 76.81±0.16bc 61.38±15.83c n. s 20.19±2.22A 25.06±18.83A 19.96±1.63A 28.27±3.66A PLA *** 22.64±0.44a 8.23±0.28b 8.71±1.86b 10.91±0.57b *** 1.98±0.29C 11.73±0.94A 1.34±0.31C 5.61±1.26B POE * 187.45±2.47a 95.56±23.02b 82.52±4.63b 111.49±13.22b * 8.53±1.72B 19.66±10.95AB 8.51±0.98B 37.16±3.23A PPD *** 298.09±7.95a 168.63±0.92b 94.41±0.62c 69.81±10.95c n. s 28.09±1.99A 35.39±26.28A 26.22±2.23A 32.84±4.62A OLL * 1.17±003a 1.18±0.32a 0.14±0.04b 0.54±0.09b * 0.12±0.02B 0.83±0.16A 0.11±0.02B 0.42±0.05B POA *** 71.95±1.86a 75.69±0.64a 27.05±5.09b 31.37±0.44b *** 7.33±1.62C 45.57±4.60A 5.54±0.49C 23.03±2.84B PSA *** 16.91±0.21a 5.68±0.93b 3.75±1.56b 3.61±1.31b *** 3.41±0.54B 17.78±0.14A 2.83±0.62B 16.01±0.74A OOL *** 22.87±0.16a 24.10±1.15a 5.21±0.95c 9.03±0.42b *** 2.31±0.62B 3.62±1.36B 1.45±0.18B 11.06±0.03A SLL ND 0.63±0.52 0.44±0.35 0.05±0.07 ND ND ND 4.16±0.18 ND ND PSEt *** 11.29±0.07a 3.39±0.21b 1.13±0.23d 2.33±0.08c *** 0.62±0.43B 1.43±0.19B 0.43±0.13B 5.37±0.21A OOO *** 88.52±5.65a 23.22±3.33b 23.25±3.12b 16.04±6.06b *** 3.98±1.79C 19.28±4.81B 5.93±0.11C 51.52±1.82A SOL *** 12.89±0.35b 15.32±0.57a 2.04±0.03c 3.73±0.56c *** 1.24±0.18B 6.67±0.95A 1.27±0.15B 7.24±0.04A SOO *** 111.61±3.82a 30.22±2.06b 8.04±4.43c 17.99±6.23bc *** 9.13±2.22C 30.11±8.32B 7.88±0.61C 68.76±0.58A SSO *** 26.16±4.15a 33.49±0.29a 1.68±0.46b 5.11±1.25b *** 2.79±0.19B 6.31±2.54B 3.21±0.54B 23.02±0.41A SSS *** 3.97±0.09a 3.04±0.04b 0.41±0.04d 1.41±0.34c * 0.27±0.06B 3.25±0.59A 0.65±0.01B 2.72±0.02A POD ** 399.97±26.62a 147.92±60.24b 112.11±5.46b 80.59±15.69b n. s 29.54±15.01A 44.44±30.81A 20.45±2.75A 46.32±3.14A PSD *** 162.04±8.11a 44.81±13.21b 25.96±0.75b 31.26±3.03b n. s 4.68±3.15A 19.84±14.25A 8.21±0.24A 18.11±2.99A OOA *** 18.21±2.09a 5.61±0.56bc 1.22±0.87c 6.69±0.35b *** 0.68±0.14B 10.16±0.75A 1.62±0.11B 9.72±0.45A SOA *** 18.12±0.32a 5.23±0.03b 1.63±0.49c 4.06±0.83b ** 1.17±0.09B 3.04±1.62B 1.53±0.32B 7.74±0.32A SOEt *** 7.30±0.24a 2.71±0.65b 1.04±0.06c 2.22±0.22bc *** 0.87±0.27B 1.51±0.45B 0.61±0.05B 3.96±0.10A SOEd *** 20.16±0.74a 6.78±1.42b 1.39±0.47c 6.31±1.11b *** 1.73±0.35C 11.94±1.24B 2.02±0.17C 15.29±0.22A Notes: 1) M: Myristic acid (C14:0); P: Palmitic acid (16:0); S: Stearic acid (18:0); O: Oleic acid (18:1); L: Linoleic acid (18:2); E: Eicosapentaenoic acid (20:5); A: Arachidonic acid (20:4); D: Docosahexaenoic acid (22:6); Pa: Palmitoleic acid (16:1); Et: Eicosatrienoic acid (20:3); and Ed: Eicosadienoic acid (20:2). 2) a-d or A-D Means±SDs with different superscripts in a row differ significantly at different stages of processing (p < 0.05), n＝5; ND＝not detected; SIG: Significance levels: *p < 0.05, ** p < 0.01, *** p < 0.001, n.s.＝not significant.

4 Discussion leading to deterioration in sensory quality and rancid 4.1 Changes of POV and TBARS in Round scad and odors24）. The evaluation of fish lipid oxidation is based on hairtail during processing POV, TBARS25, 26）, and LOX27）. POV reflects the initial prod- Lipid fractions in fish are highly sensitive to nutritional ucts of lipid oxidation（peroxides/hydroperoxides）that are deterioration. They undergo hydrolysis and oxidation, unstable during processing28）. Primary oxidation occurs in

7 J. Oleo Sci. Y. Wu, Q. Cai, L. Li et al.

the fattening stage of fat, peaks after drying, and then sig- PUFA, measured by the PI, differed between round scad nificantly decreases in the finished product phase. This is and hairtail. Decrease of PI values during salt-dried process due to unstable oxidation of primary oxidation products, indicated an existing decomposition of PUFAs. The range peroxides or hydroperoxides, which easily decomposes of variation of PI value is larger in round scad（1.61–2.24） into aldehydes, ketones and other substances under high than in hairtail（0.88-2.85）. The PI value begins to differ temperature conditions. During the curing and drying little between round scad and hairtail, but during process- stages, a significant drop in water content and an increase ing, the PI value in hairtail decreases significantly（p＜ in salt content contribute to the fat oxidation. However, 0.05）from the half-dried phase, while the decrease in the POV value is not necessarily accurate for the oxidation round scad is not significant. The change in PI value is assessment of lipids in aquatic products. During process- mainly due to the degradation of DHA and EPA. The DHA ing, it is always increased in large amounts at the initial content in hairtail is much lower than that in round scad, stage of oxidation, reaches a peak, and then falls rapidly, so so that a slight change in DHA in hairtail can cause large another indicator, TBARS, is often used to evaluate fat oxi- fluctuations in PI value. The PI range in round scad was dation. Therefore, TBARS are frequently used as markers higher than values reported for salmon40（） 0.75-1.28）and for lipid oxidation29）. Throughout the processing process, wild and farm-affected bogue23（） 0.71-1.10）. Although some the TBARS value curve of hairtail is located above the PI values in the hairtail are also within the range of round scad except for the rinsing and finishing stages. The salmon40）and bogue23）, their PI values fluctuate significant- TBARS value of the round scad is in the range of 0.15 - 0.99 ly. This decrease of PI resulted in an increase in primary mg MDA/kg sample, while the hairtail ranged from 0.26 to and secondary oxidation products（POV and TBARS）. The 0.84 mg MDA/kg, both below the 1 mg MDA/kg sample FA nutritional value damage was greater in hairtail. The level. POV results were similar to those reported for salted hairtail PUFA/SFA ratio was initially below the FAO/WHO herring（Clupea harengus, 0.4–1.1 meq/kg sample14）. recommended range and the decrease in PI was more Šimat23）suggested TBARS levels of 5–8 mg MDA/kg as the severe. Moreover, The changes in these indices indicated limit of sensory acceptability in fish. In this study, the that salt-dried processing compromises the nutritional TBARS of two fish during processing were lower than value of both PUFA-rich species. those reported for salted silver carp29）. The product also does not have any acid deterioration. 4.3 The effect of salt-dried process on TAG composition of round scad and hairtail 4.2 The effect of salt-dried process on fatty acid composi- TAG neutral lipids were fractionated by silica gel chro- tion of round scad and hairtail matography and analyzed by ESI-MS/MS. POO, PPO, POD, The compositon of fatty acids in both round scad and and PPaO were dominant in both species. This partly dis- hairtail agreed with those reported by Schneedorferová30）, agrees with the results reported by Mika41）, whereby the suggesting that the main FAs in fish are universal. Recent TAGs detected in mostly analyzed products included nutrition studies have focused on long-chain n-3 PUFAs, 16:0/18:1/18:4, POO（16:0/18:1/18:1）, OOL（18:1/18:1/18:2）, EPA（C20:5n3）and DHA（C22:6n3）are most frequently 18:0/16:1/24:1 and 20:1/20:1/22:3; oleic acid（18:1, O）was studied31）. Furthermore, the combined content of EPA and primarily found in fish meals as well as in our salt-dried DHA was higher in round scad than in hairtail. EPA and fish. Except for the other salt-dried meat, DHA and EPA DHA reduce the risk of coronary heart disease32）and help were detected in all mentioned TAGs. The TAG variation prevent and cure obesity33）and nervous system disorders, trend was different. This was attributed to different lipid including Alzheimer’s disease, schizophrenia, and depres- contents, especially since the lipid fraction in fish compris- sion34）. es cholesterol, diacylglycerol, polar lipids, and wax esters The PUFA/SFA ratio is used to estimate the nutritional in addition to TAGs42）. Qiu13）proposed that the increase in quality of lipids and their influence on coronary heart TAGs is caused by the interchange between the lipid frac- disease35）. Health guidelines recommend a ratio＞0.436）. tion and attributed the decrease to lipolysis and lipid oxi- During salt-dried process, the PUFA/SFA ratio of round dation. scad was much higher than recommended values of FAO/ WHO. The PUFA/SFA of hairtail started below the FAO/ WHO range during half-dried stage. Nutritional guidelines also recommend an n-6/n-3 PUFA ratio（cardiovascular 5 Conclusion health index）＜ 4.037）. These values are much lower in both Round scad（dark-fleshed）and hairtail（white-fleshed）are round scad and hairtail than those reported for pork and fatty fish（～10％ fat）with slightly different FA contents. lamb38, 39）and were attributed to a high n-3 PUFA content. The proportion of combined EPA/DHA was higher in round Moreover, a significant difference（p＜0.05）was observed scad. Salt-dried processing significantly affected（p＜ in both species throughout processing. The damage of 0.001）∑PUFAs and ∑MUFAs in the former but only

8 J. Oleo Sci. Fatty Acids and Triacylglycerols of Different Fishes during Salt-dried Process

∑PUFAs in the latter. Moreover, in species with highly af- 4） Wu, Y.Y.; Liu, F.J.; Li, L.H.; Yang, X.Q.; Deng, J.C.; fected FA, only C20:5n3 was similar in both species, Chen, S.J. Isolation and identification of nitrite-de- however, the variation trends were different. Some MUFAs grading lactic acid bacteria from salted fish. Adv. Ma- changed significantly（p＜0.05）in round scad but only SFAs ter. Res. 393-395, 828-834（2012）. and PUFAs changed in hairtail. Finally, in the variation 5） Arab-Tehrany, E.; Jacquot, M.; Gaiani, C.; Imran, M.; stages, more FAs changed in the rinsed and half-dried Desobry, S.; Linder, M. Beneficial effects and oxidative stages; this coincided with the changing stages of POV and stability of omega-3 long-chain polyunsaturated fatty TBARS values. Five FA nutritional indices revealed that acids. Trends Food Sci. Tech. 25, 24-33（2012）. the influence of salt-dried processing on FA nutritional 6） Farvin, K.H.S.; Grejsen, H.D.; Jacobsen, C. Potato peel value was greater in hairtail than in round scad. The lipid extract as a natural antioxidant in chilled storage of fractions in round scad were dominated by TAG（X13.6＞ minced horse mackerel（Trachurus trachurus）: Ef- hairtail）. TAG composition was identical in both species fect on lipid and protein oxidation. Food Chem. 131, but with different variation trends. 843-851（2012）. 7） Spiteller, G. Linoleic acid peroxidation̶the dominant lipid peroxidation process in low density lipoprotein̶ and its relationship to chronic diseases. Chem. Phys. Acknowledgements Lipids. 95, 105-162（1998）. Funding: This work was supported by the National 8） Capuano, E.; Oliviero, T.; Açar, Ö.Ç.; Gökmen, V.; Natural Science Foundation of China（31571869）, China Fogliano, V. Lipid oxidation promotes acrylamide for- Agriculture Research System（CARS-47）and Central Pub- mation in fat-rich model systems. Food Res. Int. 43, lic-interest Scientific Institution Basal Research Fund, 1021-1026（2010）. South China Sea Fisheries Research Institute, CAFS 9） Rød, S.K.; Hansen, F.; Leipold, F.; Knøchel, S. Cold at- （NO.2018ZD01）. mospheric pressure plasma treatment of ready-to-eat The lipid profile data were acquired at Kansas Lipido- meat: Inactivation of Listeria innocua and changes in mics Research Center（KLRC）. Instrument acquisition and product quality. Food Microbiol. 30, 233-238（2012）. method development at KLRC were supported by NSF 10） Morita, K.; Kubota, K.; Aishima, T. Comparison of aro- grants MCB 0455318, MCB 0920663, DBI 0521587, DBI ma characteristics of 16 fish species by sensory evalu- 1228622, Kansas INBRE（NIH Grant P20 RR16475 from the ation and gas chromatographic analysis. J. Sci. Food INBRE program of the National Center for Research Re- Agric. 83, 289-297（2003）. sources）, NSF EPSCoR grant EPS-0236913, Kansas Tech- 11） Gianelli, M.P.; Salazar, V.; Mojica, L.; Friz, M. Volatile nology Enterprise Corporation, and Kansas State Universi- compounds present in traditional meat products（char- ty. qui and longaniza sausage）in Chile. Braz. J. Med. Biol. Res. 55, 603-612（2012）. 12） Wang, Y.; Jiang, Y.T.; Cao, J.X.; Chen, Y.J.; Sun, Y.Y.; Zeng, X.Q.; Pan, D.D.; Ou, C.R.; Gan, N. Study on lipol- Conflict of interest ysis-oxidation and volatile flavour compounds of dry- The authors declare no conflict of interest. cured goose with different curing salt content during production. Food Chem. 190, 33-40（2016）. 13） Qiu, C.Y.; Zhao, M.M.; Sun, W.Z.; Zhou, F.B.; Cui, C. Changes in lipid composition, fatty acid profile and lip- References id oxidative stability during Cantonese sausage pro- 1） The People’s Republic of China Ministry of Agriculture cessing. Meat Sci. 93, 525-532（2013）. fishery and fishery administration , China fisheries 14） Andersen, E.; Andersen, M.L.; Baron, C.P. Character- yearbook. China Agriculture Press, China, p. 45 ization of oxidative changes in salted herring（Clupea （2016）. harengus）during ripening. J. Agric. Food Chem. 55, 2） Chung, H.Y.; Yeung, C.W.; Kim, J.-S.; Chen, F. Static 9545-9553（2007）. headspace analysis-olfactometry（SHA-O）of odor im- 15） Shen, Q.; Dai, Z.Y.; Huang, Y.W.; Cheung, H.Y. Lipido- pact components in salted-dried white herring（Ilisha mic profiling of dried seahorses by hydrophilic interac- elongata）. Food Chem. 104, 842-851.（2007）. tion chromatography coupled to mass spectrometry. 3） Wu, Y.Y.; Ren, Z.Y.; Li, L.H.; Yang, X.Q.; Lin, W.L.; Zhou, Food Chem. 205, 89-96（2016）. W.J.; Ma, H.X.; Deng, J.C. Mathematical modeling of 16） Boselli, E.; Pacetti, D.;Lucci, P.; Frega, N.G. Character- drying kinetics of salted Otolithes ruber at the differ- ization of phospholipid molecular species in the edible ent temperature. Adv. Mater. Res. 781-784, 1347- parts of bony fish and shellfish. J. Agric. Food Chem. 1352（2013）. 60, 3234-3245（2012）.

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