Sour Beans Research Articles

Characterization of defective coffee beans and blends differentiation based on 1H qNMR technique

Defective coffee beans (DCB) are one of the main reasons for poor coffee quality. In the current research, chemical difference of three common DCB including sour beans (SCB), black beans (BCB), and mold beans (MCB) were clarified using 1H qNMR method and compared with that of non-defective beans (NDCB). The results indicated that DCB has lower sugar and lipid content compared to NDCB, yet it boasts a higher acetate concentration. The 1H NMR from water-soluble content was shown to be more effective than that of oil fraction for qualitative of DCB blends, regardless of whether partial least squares discriminant analysis (PLS-DA) or machine learning (ML) algorithms were used. Support vector machine (SVM) was proved to be excellent for distinguishing DCB blends. Finally, a partial least squares regression (PLS) model was built for quantitative analysis of DCB blends. In summary, current research will not only help to reveal the material basis of DCB and their impact on coffee flavor, but also provide feasible strategies for the identification of DCB.

Bioactive compounds in blends of coffee defects originating from the harvesting

A coffee crop may consist of up to 1/5 of defective beans and finding a suitable destination for this material is economically interesting. Many coffee industries collect the selections - material containing coffee defects - and blend them with non-defective coffee fruits in specific proportions to obtain a marketable product. Studies on the composition of selections are scarce. Hydro- and liposoluble bioactive compounds were determined in five types of roasted and ground selections of coffee Arabica and in healthy Arabica and Robusta coffee species throughout an optimized HPLC-UV/Vis-MS-based method. Nicotinic acid and 4-CQA were not detected. Black and sour beans seem to increase the level of caffeine (variation from 1.3 to 2.4 g 100 g-1 of sample) in the selections. The occurrence of defects decreases the level of 5-CQA, the main representative chlorogenic acid. Trigonelline content is high in Arabica coffee, and the presence of defects does not promote a clear variation in its amount. Kahweol concentration (~74.6 to 76.9 mg g-1 of oil) was practicallythe same up the Arabica sample set; this diterpene was absent in Robusta coffee. Cafestol (variation between 12.4 and 16.4 mg g-1 of oil) is a good quality indicator. Kahweol and 16-O-methyl cafestol are species indicators, and caffeine can point out the species of coffee. PCA revealed that sour beans were associated with the presence of kahweol, while cafestol and trigonelline were correlated to the occurrence of coffee skin. The higher the proportion of black beans, the more balanced the contents of water-soluble and liposoluble compounds. Key words: PVA; Coffee harnessing; HPLC-based method; Selection of coffee; Water- and fat-soluble compounds.

Volatile compounds as potential defective coffee beans’ markers

Although Brazil is the largest raw coffee producer and exporter in the world, a large amount of its Arabica coffee production is considered inappropriate for exportation. This by-product of coffee industry is called PVA due to the presence of black (P), green (V) and sour (A) defective beans, which are known to contribute considerably for cup quality decrease. Data on the volatile composition of Brazilian defective coffee beans are scarce. In this study, we evaluated the volatile composition of defective coffee beans (two lots) compared to good quality beans from the respective lots. Potential defective beans’ markers were identified. In the raw samples, 2-methylpyrazine and 2-furylmethanol acetate were identified only in black-immature beans and butyrolactone only in sour beans, while benzaldehyde and 2,3,5,6-tetramethylpyrazine showed to be potential markers of defective beans in general. In the roasted PVA beans, pyrazine, 2,3-butanediol meso, 2-methyl-5-(1-propenyl)pyrazine, hexanoic acid, 4-ethyl-guayacol and isopropyl p-cresol sulfide also showed to be potential defective coffee beans’ markers.

Efeito da irrigação sobre a classificação do café

Foi estudado o efeito da irrigação sobre a classificação do café grão cru, quanto ao tipo, formato do grão e sua granulometria, nas cinco primeiras safras, em lavoura irrigada por pivô- central, aplicando-se cinco lâminas de irrigação em função do balanço entre a evaporação do tanque classe A (ECA) e precipitação (P), além de tratamento-testemunha (não-irrigado). A cultivar plantada foi a Rubi, em março de 1999, no espaçamento de 3,5 m entre linhas e 0,8 m entre plantas. Não foi observado efeito significativo da irrigação sobre os aspectos estudados: tipo (defeitos intrínsecos), formato (grãos chatos e moca) e granulometria dos grãos (peneiras). Contudo, entre as classes de defeito, os grãos verdes e ardidos foram os que apresentaram os maiores percentuais de defeitos para todas as safras estudadas e lâminas aplicadas. No que se refere às classes granulométricas, os tratamentos que receberam lâminas de 60% e 80% da ECA apresentaram os maiores percentuais de café médio (peneiras 15 e 16), 55,6% e 55,3%, respectivamente. O efeito da irrigação sobre a classificação do café grão cru, quanto ao tipo (número de defeitos), apresentou-se mais suscetível devido aos maiores coeficientes de variabilidade (C.V.) obtidos quando comparados a granulometria e o formato dos grãos.

Discrimination between defective and non-defective Brazilian coffee beans by their volatile profile

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. In view of the fact that coffee flavour is directly related to the volatile compounds produced during roasting, the objective of the present study was to perform a comparative evaluation of the volatile fraction of defective (black, immature, sour) and healthy coffee beans, in order to find possible chemical markers for detection of defective coffee beans in roasted coffee. Volatiles extraction and concentration was performed by solid phase micro-extraction (SPME) of the roasted coffee headspace, using a triple phase (divinylbenzene/carboxen/polydimethylsiloxane) fiber. Analysis of the volatile profiles was performed by GC–MS. The results obtained showed that the proposed methodology was adequate for extraction, concentration and analysis of the coffees volatile profile. Several substances were identified as possible markers for differentiating black, sour and immature beans from healthy coffee beans. Statistical analysis of the data by principal components (PCA) demonstrated that the volatile profile enables the differentiation of healthy and defective coffees. The data were separated into two major groups, one represented by immature and black beans and the other by healthy and sour coffee beans. Such results indicated that black and sour beans can be associated to fermentation of immature and of healthy beans, respectively.

A comparative study of chemical attributes and levels of amines in defective green and roasted coffee beans

Differences in chemical attributes (proximate composition, water activity, sucrose, acidity and pH levels) and amine levels between defective and healthy coffee beans were studied. Before roasting, significant differences ( p < 0.05) were observed for the ash contents of the coffee samples, with the highest values found for black beans. Moisture content was higher for non-defective beans in comparison to defective beans. Non-defective coffee beans had higher lipids contents than both sour and black beans. There were no significant differences ( p > 0.05) for protein levels between defective and non-defective beans. After roasting, protein levels remained constant, there was a small decrease in ash contents and a slight increase in oil contents of black and sour beans. Both black and sour beans had higher acidity levels than immature and non-defective beans. Acidity levels decreased after roasting. Water activity levels also decreased with roasting, with slightly higher levels for defective beans in comparison to non-defective ones. Sucrose levels were much higher in non-defective beans, and the lowest values were in black beans, prior to roasting. After roasting, only traces of sucrose were found. Total amine levels were much lower for black beans, in comparison to the other coffee samples. Putrescine was the prevailing amine in all samples. Histamine was only detected in the defective coffee samples. Small amounts of serotonin, cadaverine and tryptamine were found in some of the samples. After roasting to a light degree, only traces of serotonin were detected and no amines were detected after roasting to medium and dark degrees.

Composition of green and roasted coffees of different cup qualities

One of the most important criteria used for assessing coffee quality is based on sensory analysis and is referred to as cup quality. The presence of defective coffee beans is quite relevant to coffee quality. However, the majority of data on coffee properties are restricted to supposedly good quality beans. Therefore, the present study is aimed at an evaluation of physical and chemical attributes of coffees of different qualities, both green and roasted. Arabica coffee samples, previously classified by cup as soft (higher quality), hard, rioysh and rio (lower quality), were roasted at 200 °C for 1 h. Regarding attributes of green coffee beans, both bean density and volume were higher for the soft sample compared to the rio one. The soft sample also presented higher protein levels, due to its higher caffeine contents. The rio sample presented lower lipid contents, probably associated to the presence of defective beans. Acidity increased and pH levels decreased as cup quality decreased, probably due to the effect of defective beans that undergone fermentation (sour beans). After roasting, the rio sample presented higher density and trigonelline levels, indicating that it did not roast to the same degree as the other samples.

Physical and chemical attributes of defective crude and roasted coffee beans

Defective coffee beans are widely known to negatively affect beverage quality. In Brazil, the defective beans represent a population of about 20% of the total coffee production. These defective beans are separated from the non-defective ones prior to commercialization in the international market and are dumped in the Brazilian internal market, thus depreciating the quality of the roasted coffee consumed in Brazil. In order to offer more attractive alternative uses for these beans, an assessment of their physical and chemical attributes is of relevance. In this study, physical attributes, such as bean and bulk densities, bean volume and colour, and also chemical attributes, such as caffeine, trigonelline and chlorogenic acids, were evaluated in defective and non-defective coffee beans, both in the crude and roasted state. With the determined physical and chemical attributes, it was possible to differentiate the types of defective beans, and it was also demonstrated that both black and sour beans roast to a lesser degree than the other types of beans, under the same roasting conditions.