Chemical composition of defective coffee beans

Immature-black beans (VP) and immature beans (V), known by the Brazilian coffee terminology as 'cafe verde-preto' and 'cafe verde', are defective beans and cause a reduction of the quality of the beverage. Their presence in raw coffee samples is due to a high percentage of immature fruits at harvest. In this study, some of their physico-chemical properties and chemical composition were investigated and compared with non-defective coffee beans (B). B beans were heavier and had higher humidity than VP and V. Although they did not differ with respect to pH, V beans were more acidic (titrable acidity). Sucrose was the main soluble carbohydrate in all samples and its content in B beans was higher than defective beans. Reducing sugars were found at higher concentration in V and B beans. Protein contents increased from VP to B (VP < V < B); however, there was no relationship with free amino acid contents, which were higher in V beans. Qualitative analysis showed that asparagine was the main amino acid in these beans. Denaturing electrophorectic (SDS-PAGE) profiles of proteins did not show qualitative differences among the three coffee types. The contents of 5-caffeoylquinic acid (5CQA) and soluble phenols were also higher in V beans, and their ratio increased from VP to B (VP < V < B). In this order, the reversed-phase high-performance liquid chromatography profile at 280 nm of methanolic extracts prepared similarly showed, in general, a reduction of detected peak areas. Polyphenol oxidase activity was inversely associated with 5CQA contents, V beans showing the lowest activity. Similar caffeine contents were observed in the samples. Total oil content was higher in B beans. In addition, the defective beans were individually mixed with B beans in different proportions and analysed for some constituents. The results showed that, depending on the substance analysed, its content in the B beans is significantly affected. Although the influence of each component of the raw coffee bean that determines beverage quality has never been established, our results show that the presence of defective beans can drastically change the chemical composition of the final product. (C) 1999 Elsevier Science Ltd. All rights reserved.