Estudos para determinação das melhores formulações de blends de cafe arabica (C. arabica) com cafe robusta (C. canephora Conilon) para uso no setor de cafes torrados e moido e de cafes expresso. / Study for determination of the best blends formularizations of arabian (C.arabica) with robust coffee(C. canephora Conilon) for use in the sector of roast and worn coffees and coffees espresso.

Luciane Carneiro Mendes

The main objective of this thesis was to study various blends of arabica and robusta coffees, prepared both by filtration and the espresso technique, by carrying out sensory evaluations with consumers. Initially, for each coffee studied, the most adequate degree of roast was determined using a sensory evaluation by experts and by a panel trained for Quantitative Descriptive Analysis. The results indicated a medium roast as being that presenting greater intensity of characteristic coffee aroma and flavour with no perception of a burnt flavour, characterised by a loss of mass from 15 to 16% and by a bean luminosity (L*) between 37 and 38. The fundamental stage of the work followed with the evaluation of the blends (from 10 to 50% semi-dry processed robusta) plus a 100% arabica sample, prepared both by filtration and by the espresso technique, using an acceptance test with daily coffee consumers. The results for both types of preparation showed no significant difference (at the 5% significance level) in the appreciation of the samples by the consumers. The results of the sensory test were complemented by chemical evaluations. The chlorogenic acid, carboxylic acid and sugar contents of the arabica and robusta (dry processed - RS, semi-dry processed - RCD) coffees, and of some blends (80% arabica + 20% RCD robusta; 60% arabica + 40% RCD robusta) were determined by high performance liquid chromatography (HPLC). The contents of these components were determined in the raw coffees, after roasting and in the brews (filtered and espresso). The results showed differences between the arabica and robusta coffees for various components, especially in the raw coffees, some differences between the RCD and RS robustas also being found. The values found in the blends were coherent considering the values found for the 100% robusta RCD and arabica samples. The differences tended to decrease with roasting and were even smaller in the brews, be the samples prepared by filtration or the espresso technique. To finalise the work, the volatile profiles of the samples cited in the previous paragraph, with the exception of the raw samples, were observed, using a technique of isolation from the headspace by retention in a porous polymer and analysis by gas chromatography (GC). The results showed considerable differences between the profiles of the arabica and robusta coffees, especially in the brews, but little difference was noted between the blends and the arabica coffee. In general, despite considerable differences between the arabica coffee and the robusta coffee, when the latter is added to the former up to 50% (as shown in the sensory evaluation), little difference is detected, either chemically or by the sensory acceptance of the final product. These results show the viability of using robusta coffee in both types of brew preparation, contrary to the prejudiced idea existing in some parts of coffee agro-business.

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