Yao, Tianyu (2017-05). Brew Methods Effect on Coffee Flavor and Aroma. Master's Thesis.
Coffee is one of the most popular aromatic hot drinks in the world. Numerous coffee brewing methods have been developed to make a cup of coffee. In industry, coffee flavor and aroma is determined by using a method called cupping, but in order to quantitate flavor and aroma in coffee, descriptive sensory is a better option. This study identified how brew methods influence coffee aroma and flavor. Four different roast level Folgers(R) commercial coffee (Breakfast blend, Classic roast, 100% Colombia and Black silk) were brewed by four brewing methods (pour over, drip, French press, and cold brew) and were tested using a trained descriptive panel using the World Coffee Research (WCR) coffee lexicon. Twenty-five main aroma attributes and thirty-five main flavor and texture attributes of coffee were used. Cold brew method produced the mildest coffee among the four brew methods while drip produced a much stronger coffee. The sensory aroma and flavor differences between different coffee types were not as great as differences between brew methods. From chemical tests, Brix percentage and TDS (Total Dissolved Solids) differed across coffee types and brew methods. Chemical attributes were closely associated with overall impact, body fullness, bitter basic taste and roasted and burnt flavor aromatics. Volatile compounds (n = 271) were identified. Forty-four volatile aromatic compounds differed across coffee types while thirty-seven volatile aromatic compounds differed across brew methods. Folgers(R) 100% Colombia coffee showed a difference from the other three coffee types by showing higher (P < 0.05) amount of volatile compounds, especially in 2-butenal, and 1-(2-hydroxyphenyl)-ethanone (beany aroma). Cold brewed Folgers(R) 100% Colombia was high on sweet, overall sweet flavor as well as 2,3-hexanedione. The preparation method is a critical factor affecting coffee flavor and aroma. Coffee from the cold brew method was more fruity, floral and sweet whereas coffee from the drip or French press methods were roasted, burnt, and ashy.