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. 2023 Mar 25;28(7):2949.
doi: 10.3390/molecules28072949.

Comparative Study on the Volatile Organic Compounds and Characteristic Flavor Fingerprints of Five Varieties of Walnut Oil in Northwest China Using Using Headspace Gas Chromatography-Ion Mobility Spectrometry

Lina Sun  1 , Yanlong Qi  2 , Meng Meng  3 , Kuanbo Cui  1
Affiliations

Comparative Study on the Volatile Organic Compounds and Characteristic Flavor Fingerprints of Five Varieties of Walnut Oil in Northwest China Using Using Headspace Gas Chromatography-Ion Mobility Spectrometry

Lina Sun et al. Molecules. .

Abstract

Odor is an important characteristic of walnut oil; walnut oil aromas from different varieties smell differently. In order to compare the differences of volatile flavor characteristics in different varieties of walnut oil, the volatile organic compounds (VOCs) of walnut oil from five different walnut varieties in Northwest China were detected and analyzed using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The results showed that 41 VOCs in total were identified in walnut oil from five different varieties, including 14 aldehydes, 8 alcohols, 4 ketones, and 2 esters. Walnut oil (WO) extracted from the "Zha343" variety was most abundant in VOCs. The relative odor activity value (ROAV) analysis showed that aldehydes were the main aroma substances of walnut oil; specifically, hexanal, pentanal, and heptanal were the most abundant. Fingerprints and heat map analysis indicated that WO extracted from the "Xin2", "185", "Xin'guang", and "Zha343" varieties, but not from the "Xinfeng" variety, had characteristic markers. The relative content differences of eight key VOCs in WO from five varieties can be directly compared by Kruskal-Wallis tests, among which the distribution four substances, hexanal (M), hexanal (D), pentanal (M), (E)-2-hexanal (M), presented extremely significant differences (P<0.01). According to the results of the principal component analysis (PCA), WO extracted from the "Zha343" variety was distinct from the other four varieties; in addition, WO extracted from the "Xin2" variety exhibited similarity to WO extracted from the "185" variety, and WO extracted from the "Xinfeng" variety showed similarity to WO extracted from the "Xin'guang" variety. These results reveal that there are certain differences in the VOCs extracted from five different WO varieties, making it feasible to distinguish different varieties of walnut oil or to rapidly detect walnut oil quality based on its volatile substances profile.

Keywords: HS–GC–IMS; flavor fingerprint; volatile organic compounds; walnut oil.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a): GC–IMS three-dimensional spectra of the VOCs in walnut oil from five different varieties; (b): Comparison of GC-IMS spectra of VOCs in of walnut oil from five different varieties (after color deduction).
Figure 2
Figure 2
Fingerprint (gallery plot) of characteristic VOCs in walnut oil from five different varieties (A: Xin2; B: 185; C: Xinfeng; D: Xin’guang; E: Zha343).
Figure 3
Figure 3
PCA diagram of walnut oil from five different varieties((A: Xin2; B: 185; C: Xinfeng; D: Xin’guang; E: Zha343)).
Figure 4
Figure 4
Heat map of VOCs in walnut oil from five different varieties.
Figure 5
Figure 5
Box plot of key VOCs (relative content) in walnut oil from five different varieties.
Figure 6
Figure 6
The appearances of walnuts from five varieties.
See this image and copyright information in PMC

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