Analysis of the main aroma compounds in nine mature Yanshan Chinese chestnut varieties

Abstract: 【Objective】The main aroma compounds and differences in nine Yanshan Chinese chestnut varieties at maturity were analyzedin order to provide useful information for breeding and storage research of Yanshan Chinese chestnut.【Methods】Nine Chinese chestnut varieties were harvested at maturity from Qianxi and Zunhua county of Tangshan city, and then were stored at (-2+1) ℃. The analyses were made on the fifth day after harvest. The aroma components of chestnut fruits were determined by headspace solid phase microextraction (HS-SPME) combined with GC-MS. 2.0 g kernel was weighed accurately and were cut into 2.0 mm³ small pieces to be preheated for 18 min at 58.5 ℃ with headspace sampler oven before it was moved to 15 mL headspace sample bottle. Aroma ingredients were detected by Agilent 7890 A GC + 5975 C inert XL MSD after 50 min extraction (65 μm PDMS/DVB fiber) with automatic injection. The samples were analyzed with a HP-5 MS capillary column (30 m×0.320 mm×0.25 μm) . The injection temperature was 230 ℃ (split ratio 20:1) . The initial separation temperature was kept at 40 ℃ for 3 min, then it was increased at 10 ℃ · min^-1 to 180 ℃, and was maintained for3 min, then the temperature was increased to 200 ℃ at 10 ℃ · min^-1 and kept 2 min. The EI ion source temperature、interface temperature and quadrupole temperature was 230 ℃、250 ℃ and 150 ℃ separately. The ion mass scanning range was 30-480 m/z. Besides, principal component analysis (PCA) was performed with SPSS 19.0 software for data processing.【Results】36 volatile aroma compounds were detected in the nine varieties, including 7 aldehydes, 5 alcohols, 5 alkanes and 5 esters, 4 acids, 3 phenolics, 1 ether, 1 ketone and 5 other substances. The contents of nonyl alcohol, octanol, pentadecane, dodecane, eugenol, nonaldehyde, phenylacetaldehyde and methyl palmitate, myristic acid, ethylhexyl carbonate, palmitic acid, geranyl acetone, octane, n-pentafuran and o-dichlorobenzene were relatively higher in Yanshan Chinese chestnut. The main aroma components in different chestnut varieties and their relative contents were different. The content of phenylacetaldehyde in‘Yanshanduanzhi'was the highest (72.21%) , followed by phenythanol. The content of n-pentafuran in‘Yankui'was the highest (28.11%) , followed by methyl palmitate. The content of geranyl acetone in‘Yanli'was the highest (24.19%) , followed by nonaldehyde and decanal. Aldehydes was the primary aroma compound in‘Yanlong', its content was 94.19%, and the content of phenylacetaldehyde was the highest (47.08%) in‘Yanlong'. The content of phenylacetaldehyde in‘Yanzi'was the highest (31.31%) , followed by decanal and octane.Isopropyl myristate in‘Yanshanzaofeng'was the highest (29.53%) , followed by palmitic acid, phenylacetaldehyde and phenythanol. The content of n-pentafuran was the highest in‘Zipo' (56.44%) , and the contents of isopropyl myristate, phenylacetaldehyde, decanal and azulene were 3.06%-26.96%. The content of odichlorobenzene in‘Zunyu'was the highest (29.29%) , followed by pentadecane. The characteristic aroma was different among the nine varieties. The main aroma compounds of‘Dabanhong'were nonyl alcohol, hexyl alcohol, eugenol, nonaldehyde, decanal, 5, 9, 13-tetradecenal, undecanal and dodecanal. The main aroma compounds of ‘Yanshanduanzhi' were phenythanol, methyl palmitate, isopropyl myristate and myristic acid. The main aroma compounds of‘Yankui'were dodecane, 2, 5-bitertiary butyl phenol, phenylacetaldehyde and 2-methylpropionate. The main aroma compounds of‘Yanli'were nonyl alcohol, nonaldehyde, decanal, methoxyphenyloxime and methyl palmitate. The main aroma compounds of‘Yanlong'were nonaldehyde and decanal. The main aroma compounds of‘Yanzi'were 2, 6-bis (1, 1-dimethylethyl) -4-phenol, octane and ethylhexyl carbonate. The main aroma compounds of‘Yanshanzaofeng'were phenythanol, 5, 9, 13-tetradecenal, methyl palmitate, isopropyl myristate, palmitic acid, cis-9-cetenic acid, n-pentadecanoic acid and myristic acid. The main aroma compound of‘Zipo'was n-pentafuran. The main aroma compounds of‘Zunyu'were decanal and methyl palmitate. The content of phenylacetaldehyde was higher in eight chestnut varieties except‘Yanli'. And although the relative content of phenylacetaldehyde in‘Yanshanduanzhi'‘YanLong'and‘Yanzi'was72.21%, 47.08%, 31.31%, respectively, but phenylacetaldehyde was not the main aroma compounds to the three varieties. On the contrary, the contents of methyl palmitate, isopropyl myristate, nonaldehyde, ethylhexyl carbonate and myristic acid were lower than phenylacetaldehyde, but they were the most important aroma compounds of the three varieties. Phenylacetaldehy is only the main aroma components of aldehydes to‘Yankui'. The relative content of decanal was lower than that of phenylacetaldehyde in 9 varieties, but it was the main contributor of aroma compounds in the 4 varieties of ‘Dabanhong' ‘Yanlong' ‘Yanli' and ‘Zunyu'. Octanol, geranyl acetone and (E) -nonenal were relatively higher, but did not appear in the main aroma compounds.【Conclusion】The composition of the characteristic aroma compounds of the nine Yanshan Chinese chestnut varieties at maturity was different. The comprehensive scores of the aroma compounds in the nine Yanshan Chinese chestnut varieties were ranked as follows: ‘Danbanhong'>‘Yanli'>‘Yanshanzaofeng'>‘Yanzi'>‘Zunyu'>‘Zipo'>‘Yankui'>‘Yanlong'>‘Yanshan duanzhi'. Decanal was the aroma substance contained in all of the nine varieties, and its content was relatively higher. The main aroma compounds of the nine varieties were alcohols, esters and aldehydes. Aldehydes would play an important role in??. And it was a substance with larger amount among the characteristic aroma components. Decanal, nonaldehyde, methyl palmitate and isopropyl myristic acid were the main characteristic aroma compounds in the nine Yanshan Chinese chestnut varieties at maturity.