Summary 2

Summary 2

In this article  “Enzymatic-spectrophotometric determination of sucrose in coffee beans”, A. Alcazar, J. Marcos Judaro, A. Gustavo Gonzalez (2005) wrote a report about determining sucrose in samples of coffee beans with an enzymatic spectrophotometric.

Coffee flavour is developed during the roasting process of beans. Sucrose is a very important flavour. Sucrose is the major free sugar present in green coffee. It has been quantitated in coffee beans by using ion chromatography. The ion chromatography separation looks very easy. However, the detection presents several handicaps. The determination of low molecular weight sugars, specially sucrose, can be easily carried out by using enzymatic procedures. In this case the author used selectivity from the features of the enzymatic process, leading to the quantitation of sucrose without interferences from other glucides. So the aim of the paper is to develop an enzymatic spectrophotometric method for determining sucrose in samples of coffee beans.

For this experiment an Unicam UV series 500 with quartz-cells of 1.0 cm was used. The green coffee samples were supplied from Centre National de Recherche Agronomique (CNRA). Roasted coffee samples were obtained from local stores. Before starting, the samples were sieved and dried.

In order to evaluate the applicability of the method, samples of green and roasted coffee were analysed. Since the method is based on glucose released by invertase activity the author considered possible interferences due to the presence of endogenously reducing sugars. The sugars are present in green coffee, but the quantities are very small. In the green coffee values between 7.6 and 4.6% were obtained. These results are in accord with the reported values in Ref.  In the case of the roasted coffee, no sucrose was found. Sucrose is lost rapidly during roasting process, so that at a medium or dark type of roast sucrose is completely lost.

As a conclusion, the proposed method has been shown to be useful for determining sucrose in coffee beans. The experiment is suitable, easy to apply and does not need expensive instrumentation. The most important variable was the temperature of the extraction step.  No differences have been found between the proposed method and the currently practiced method.