Comparison of nine common coffee extraction methods: instrumental and sensory analysis

Abstract

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a singleserve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in°B rix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids $ texture/body, headspace intensity $ aroma intensity, concentrations of caffeine/chlorogenic acids $ bitterness and astringency.

Unremitting Problems With Chlorogenic Acid Nomenclature: A Review

“…Some of them are in agreement with Moeenfard's results and some are not. The work in compliance was published by Gloess et al, 52 but they also used the wrong nomenclature. Both of these authors mentioned 3-CQA as chlorogenic acid.…”

Analytical methods applied for the characterization and the determination of bioactive compounds in coffee

“…Caffeine (1,3,7-trimethylxanthine) is the major alkaloid present in green coffee beans which also can be found in considerable concentration in roasted coffee [36,53,54]. Because of its stimulating effect on the central nervous system, it is also the most widely known constituent of coffee [55].…”

“…Sample preparation before this analysis is usually very simple and contains only filtration and dilution steps [54,57,58]. Some methods include clarification with Carrez reagents [15,36,53] or with lead acetate [59]. Alternatively, sample can be cleaned up by water extraction of powdered coffee beans mixed with magnesium oxide [56] or using solid phase extraction [27,60].…”

“…The samples prepared according to one of these procedures were analyzed in a reverse phase elution mode with octadecylsilicapacked column. Caffeine was detected with the ultraviolet absorbance detector at 270-280 nm [11,15,27,36,53,54,[56][57][58]60]. Alternatively, HPLC with mass spectrometry Extraction with aqueous methanol and sonication for 10 min, followed by shaking at 300 rpm for 30 min 5-CQA and 3-CQA [53] was used for determination of caffeine [59] or theobromine and theophylline [36].…”

Diterpenes in espresso coffee: impact of preparation parameters

“…People prefer to know more about the chemical composition of their coffee brew and the potential impact of specific compounds on their health [19]. Therefore during the past few decades, EC have caught more attention due to high consumption.…”