## 5 Conclusions  
In this study, the volatile flavor profiles of two different types of WPCS stored in the same silo were analyzed using HS-SPME-GC-MS, HS-GC-IMS, and E-nose. A total of 32 and 101 VOCs were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively, including aldehydes, alcohols, esters, ketones, and hydrocarbons. The analysis of abnormal silage via HS-SPME-GC-MS revealed three major classes of characteristic VOCs associated with a bitter almond taste, including benzaldehyde, cyanides, and isocyanates. The action of organophosphate ester-related pesticides was found to increase specific volatile compounds, such as cyanides and isocyanates, through biological enzymatic or microbial biochemical processes. This suggests that these compounds are unique volatile byproducts and precursors of the bitter almond flavor in abnormal silage. The presence of benzaldehyde may be linked to herbicides or plant growth regulators applied to corn, highlightingthe unique bitter almond flavor characteristics imparted by the silage fermentation process. E-nose differential contribution values indicated that W5S (nitrogen oxides) was the key substance distinguishing the two feedstuffs. These findings are consistent with GC-IMS and GC-MS results, which identified 34 nitrogen-containing heterocyclic compounds in the abnormal silage sample, including 1H-tetrarole-1,5-diamine, which is noted for its high nitrogen content. In summary, the VOC data revealed distinct combinations and concentrations of compounds in the feedstuffs, each with different odor profiles, suggesting that these compounds can interact with one another to regulate further flavor characteristics, which are critical for feed quality. The comprehensive use of HS-SPME-GC-MS and HS-GC-IMS techniques provided a detailed understanding of the impact of VOCs on silage odor. The odor of silage is likely influenced by environmental factors, such as temperature and microorganisms, and thus warrants further investigation in the future. This study enhances our understanding of the chemical processes involved in silage odor formation and provides a scientific basis for addressing bitter almond odors and improving silage quality.  
The following supporting information can be downloaded at: [[https://doi.org/10.6084/m9.figshare.28044839](https://doi.org/10.6084/m9.figshare.28044839)]([https://doi.org/10.6084/m9.figshare.28044839](https://doi.org/10.6084/m9.figshare.28044839)) (accessed on 17 December 2024), Table S1: HS-SPME-GC-MS identification results of aroma components of different silages.  
Conceptualization, Y.C. and L.W.; methodology, Y.C. and Y.Z. ([PERSON]); software, Y.C. and Y.Z. ([PERSON]); validation, Y.C. and N.Z.; formal analysis, Y.C. and Y.Z. ([PERSON]); investigation, Y.C. and Y.Z. ([PERSON]); resources, Y.Z. ([PERSON]) and Y.Z. ([PERSON]); data curation, Y.C.; writing--original draft preparation, Y.C.; writing--review and editing, Y.G. and L.W.; visualization, Y.C. and Y.Z. ([PERSON]); supervision, Y.Z. ([PERSON]) and Y.Z. ([PERSON]); project administration, N.Z. and Y.Z. ([PERSON]); funding acquisition, Y.Z. ([PERSON]) and Y.Z. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
This research was funded by Shanxi Province Science and Technology Major Special Projects (Grant No. 202201140601026), the National Key Research and Development Plan Project (Grant No. 2021 YED19011), and the Modern Agricultural Industrial Technology System of Shanxi Province (Grant No. 2024 CYJSTX13). We thank the editors and anonymous reviewers for their useful suggestions on improving the quality of this article.  
Not applicable.  
All data supporting the results of this study are included in this manuscript and its Supplementary Information File. Also, the datasets used and/or analyzed in this study are available upon request from the corresponding authors.  
The authors declare no conflicts of interest.