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In order to study the quality change of coffee malt premixed powder with the extension of storage period, the coffee malt premixed powder was stored at the environment where the temperature is 25 ℃ and 35 ℃, respectively, and the relative humidity is 50% respectively. Its moisture, fatty acid value and falling value were monitored during the whole storage period. The volatile compounds were separated and identified by solid phase microextraction accompanying gas chromatography-mass spectrometry during the whole storage period. The results demonstrated that with the extension of storage period, the overall moisture content shows a falling trend, while the fatty acid value and falling value show an overall rising trend. The higher the storage temperature, the more significant the change is 41 kinds of main volatile compounds of coffee malt ready mixed powder were identified. It mainly includes 13 kinds of aldehydes, 15 kinds of heterocycles, 7 kinds of esters, 4 kinds of alcohols and 2 kinds of ketones. Among them, the relative concentration of aldehydes (n-hexanal, nonanal, trans-2-nonenal) showed an increasing trend with the extension of storage period.

Different malt samples with various total acid content were used to brew beer. The organic acid content in both the malt and the brewed beer was measured by using high-Performance liquid chromatography (HPLC) to establish the correlation between the total acid content in malt and the organic acid content in the beer. Additionally, gas chromatography-mass spectrometry (GC-MS) was used to detect the components of volatile compounds in the beer, and sensory evaluation was employed to assess the brewed beer's qualities. The results indicated that as the total acid content in malt increased, the pH value gradually decreased, and the content of succinic acid, malic acid, lactic acid, and acetic acid increased. There was a significant positive correlation between the total acid content in malt and the total acid content, malic acid content, and lactic acid content in the beer, with correlation coefficients of 0.94, 0.94, and 0.92, respectively. Different malt samples with varying total acid content demonstrated different characteristic aroma compounds in the brewed beer, contributing to differences in sensory attributes. As the total acid content in malt increased, the perceived acidity score of the brewed beer increased, while the scores for hop/fruit aroma, phenolic aroma, and alcohol perception decreased.

Methane is a greenhouse gas and significantly contributes to global warming. Methane biofiltration with immobilized methane-oxidizing bacteria (MOB) is an efficient and eco-friendly approach for methane elimination. To achieve high methane elimination capacity (EC), it is necessary to use an exceptional support material to immobilize MOB. The MOB consortium was inoculated in biofilters to continuusly eliminate 1% (v/v) of methane. Results showed that the immobilized MOB cells outperformed than the suspended MOB cells. The biofilter packed with fly ash ceramsite (FAC) held the highest average methane EC of 4.628 g h–1 m–3, which was 33.4% higher than that of the biofilter with the suspended MOB cells. The qPCR revealed that FAC surface presented the highest pmoA gene abundance, which inferred that FAC surface immobilized the most MOB biomass. The XPS and contact angle measurement indicated that the desirable surface elemental composition and stronger surface hydrophilicity of FAC might favor MOB immobilization and accordingly improve methane elimination.