###### Abstract  
Steamed bread is a traditional staple food in China, and it has gradually become loved by people all over the world because of its healthy production methods. With the improvement in people's living standards, the light flavor of steamed bread fermented by single yeast cannot meet people's needs. Multi-strain co-fermentation is a feasible way to improve the flavor of steamed bread. Here, the dynamic change profiles of volatile substances in steamed bread co-fermented by _Saccharomyces cerevisiae_ SQJ20 and _Wickerhamomyces anomalies_ GZJ2 were analyzed using the electronic nose (E-nose) and headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The five detectors of the E-nose rapidly detected the changes in volatile substances in different dough or steamed bread with the highest response value in co-fermented dough. A total of 236 volatile substances were detected in all the samples using HS-SPME-GC-MS, and alcohols were the most variable component, especially Phenylethyl alcohol. Significantly, more alcohols and esters were upregulated in co-fermented dough, and the addition of _W. anomalous_ GZJ2 improved the key volatile aroma compounds of steamed bread using the relative odor activity value method (ROAV), especially the aldehydes and alcohols. Moreover, these key volatile aroma compounds can be quickly distinguished using the W2S detector of the E-nose, which can be used for the rapid detection of aroma components in steamed bread. steamed bread; volatile flavor substances; _Wickerhamomyces anomalies_; co-fermentation; HS-SPME-GC-MS; electronic nose  
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by single yeast is light, which cannot meet people's needs. In this case, multi-strain co-fermentation is a feasible way to improve the quality of steamed bread, which not only ensures the stability, simplicity, and safety of the industrial production process, but also enriches higher quality of steamed bread, including better flavor, texture, internal structure, etc. [5; 6]. Many studies have confirmed that the mixed fermentation of _Saccharomyces cerevisiae_ (_S. cerevisiae_) and lactic acid bacteria, such as _Weissella cibaria_ (_W. cibaria_) [7], _Toruslospora delbrueckii_ (_T. delbrueckii_) [6], _Lactobacillus jolnsonii_ (_L. jolnsonii_), and _Aectobacter pasteurianum_ (_A. pasteurianum_) [8], improved the quality of steamed bread. Furthermore, the co-fermentation of _S. cerevisiae_ with non-_Saccharomyces_ strains, such as _Wickerhamomyces anomulus_ (_W. anomulus_) and _Toruslospora delbrueckii_ (_T. delbrueckii_), was confirmed to improve the quality of steamed bread in our recently published literature [9]. _S. cerevisiae_ has a good gas production capacity; however, its aroma production capacity is weak. Meanwhile, non-_Saccharomyces_ strains can produce more complex flavor components and metabolites, such as extracellular enzymes, which can fully release substances in raw materials and convert them into alcohols, esters, and other aroma substances, although their gas production capacity is often weak. The combination of _S. cerevisiae_ and non-_Saccharomyces_ strains is beneficial to enhance the aroma of the fermentation substance. Among them, _W. anomulus_, as a non-_Saccharomyces_ strain, has been reported in recent years to increase the aroma of fruit wine, rice wine, etc. [10; 11]. Sourdough contains _S. cerevisiae_, non-_Saccharomyces_ strains, and lactic acid bacteria, all of which are highly biosafe because they have been used in the fermentation of steamed bread for thousands of years. Moreover, the co-fermentation of _W. anomulus_ with _S. cerevisiae_, isolated from sourdough, improved the quality of steamed bread; however, their effects on the aroma components of steamed bread are still unclear. The quality of steamed bread is reflected in the flavor, texture, shelf life, and nutritional value, etc., among which flavor substances are important indicators of high-quality steamed bread.