New procedures for determination of acids in coffee extracts, and observations on the development of acidity upon ageing

Abstract

Analysis of the acid content of coffee extracts has been performed by adaptation of a procedure, recently introduced by our laboratory, to the task of evaluating both the "volatile" and "non volatile" fractions. Besides useful changes in the preparation of the acid pool, diazobutane was used to obtain esters of volatile acids suitable for GC-MS analysis, to minimize losses of material by evaporation. The new procedures have been used to evaluate changes in the acid content of some Italian-style roasted coffee extracts after accelerated ageing (65 degrees C, 72 h) and in coffee beans after different amounts of roasting. The origin of formation of volatile acidity was also investigated. Electronic supplementary material is available if you access this article at http://dx.doi.org/10.1007/s00216-002-1561-y On that page (frame on the left side) a link takes you directly to the supplementary material.

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

“…The lower roast degree of lunghi (which may preserve acids) might have compensated for the higher dilutions. The results are consistent with the literature [3,5,15,[34][35][36][37].…”

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

“…Concentrations of citric and malic acids slightly decrease. In the same time, considerable increase in formic, acetic, glycolic and lactic acids can be observed, while phosphates are little affected by the roasting process [98]. Therefore, analysis of these compounds is so important.…”

“…Verardo et al [98] used gas chromatography with mass spectrometric detection. The acids were derivatized before analysis with diazobutane (used for low molecular weight (C1-C3) acids) or with diazomethane (used for other acids).…”

“…The acids were derivatized before analysis with diazobutane (used for low molecular weight (C1-C3) acids) or with diazomethane (used for other acids). The procedure was successfully applied for analysis of different coffee types and for analysis of changes in coffee caused by the roasting process [98]. Bähre and Maier also applied gas chromatography with mass spectrometric detection for analysis of carboxylic acids in coffee [99].…”

Effects of refrigeration and oxygen on the coffee brew composition

“…The increase of sourness in warm stored coffee brews has been attributed to the increase of acids produced by the hydrolysis of the quinic acid lactones and chlorogenic acid lactones formed during roasting, the hydrolysis of low molecular weight esters, and the thermal degradation of chlorogenic acids into their corresponding hydroxycinnamic acids [8,9]. However, most of these conclusions have been obtained from the results of (a) accelerated ageing studies where coffee brews were maintained at high temperatures (60 to 95ºC) [3,4,[10][11][12][13], (b) studies of coffee beverages added with sugar and other additives, and pasteurized, stored at room or refrigeration temperatures [5,14]; or (c) sterilized sugary coffee beverages stored at high temperature [15]. In all of them, an additional thermal process is included after coffee brew preparation, which could be relevant to the degradation of chlorogenic acids and, consequently to the coffee quality.…”