Effects of Cold and Hot Brew on the Aroma of Coffee Extract by SPME-GC-MS Combined with Multivariate Statistical Method

This study aimed to explore the differences in aroma between cold and hot brewed coffee beans, and the correlation between sensory descriptions and aroma compounds. Yunnan and Sidamo coffee beans were used as raw materials, and cold and hot brewing were conducted separately. The aroma components of the extracted liquid were determined by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Meanwhile, sensory evaluation was also conducted. Multivariate statistical analysis was used to identify the aroma compounds that made significant contributions to sensory descriptions. The results showed that a total of 69 volatile compounds were identified in the four different coffee extracts, of which 39 had odor activity values (OAV)>1. The content of most volatile compounds was higher in cold brewing than in hot brewing, while 4-ethyl guaiacol, 2,4-di-tert-butylphenol, and p-vinyl guaiacol were higher in hot brewing than in cold brewing. In terms of sensory evaluation, the scores for green aroma, fruity aroma, and nutty aroma were significantly higher in cold brewing than in hot brewing, while the score for smoky aroma was higher in hot brewing. 4-ethyl guaiacol and p-vinyl guaiacol contributed significantly to smoky aroma, while hexanal contributed significantly to green aroma. Methyl isovalerate, 2-butylfuran, ethyl nonylate, and ethyl butyrate contributed significantly to fruity aroma, and 2,3-diethyl-5-methylpyrazine contributed significantly to nutty aroma. This study provides valuable data for exploring the aroma quality of cold and hot brewed coffee extracts.