# The Effect of Type and Duration of Digestive Enzyme Treatment on Coffee Bean Composition
## 3 Results and Discussion
### Color of the Beans  
Green and roasted coffee beans were ground and subjected to color analysis in the CIELab system. Figure 1 presents a comparison of all results in the form of a 3D graph. In the case of green beans, results can be divided into three groups. Group 1 consists of untreated beans, in which color differed only in the proportion of red (+a*: 1.85 and 2.25 for untreated Arabica and Robusta beans, respectively). Group 2, with brightness (L*) similar to the first one, comprises all samples prepared with Arabica beans; group 3 includes all samples prepared using Robusta beans--their L* was slightly lower in relation to other groups. Comparing all modified samples (groups 2 and 3) with unmodified beans (group 1), it is observed that they generally had slightly higher values of red (+a*) and yellow (+b*). The color of samples after roasting (group 4) underwent significant changes: L* and b* values decreased, while a* values increased compared to green beans. Upon closer examination (Figure 2), it can be seen that, after roasting, only the color of untreated beans still clearly differed from the color of the other samples (untreated roasted Robusta beans exhibited higher L* value, lower a* value and comparable b* value in relation to Arabica). Numerical values of CIELab analysis are given in Supplementary Materials (Tables S1 and S2). It should be noted that all modified samples generally had a higher L* value, which may be due to lower Maillard reaction and caramelization ranges during the roasting process and, consequently, a lower amount of produced melanoidins [1].  
Figure 1: Color of all coffee samples as measured in the CIELab system. Group 1 consists of untreated beans, group 2 contains controls and modified samples of Arabica beans and group 3 contains controls and modified Robusta beans. Group 4 encompasses values for roasted beans of all variants.  
Changes in the color of coffee beans due to enzymatic treatment observed in this study resemble those observed in the case of civet coffee. [PERSON] [23] analyzed coffee beans produced with the involvement of the Indonesian Palm cirvet and Ethiopian civet. Compared to untreated beans, digested beans exhibited lower brightness and higher values of the a* and b* parameters, possibly resulting from the action of enzymes and digestive juices on the surface of the material. In a study by [PERSON] et al. [24], where the color of kopi luwak from the Gayo Highlands region was analyzed according to Specialty Coffee Association of America (SCAA) standards, the examined green beans were mainly described as yellow, in contrast to the greenish-green color reported earlier for beans produced in the same region using the semi-dry method. All of those changes in green coffee bean color might serve as an indicator of chemical transformations resulting from the biochemical processing. Currently, there is no information in the literature regarding the color of roasted kopi luwak beans. The changes observed in this study related to the roasting process--primarily, the reduction in brightness and increase in the share of red in the overall color of coffee beans--were consistent with previously published data [25; 26; 27]. Results of this study mostly align with previous reports on color changes in coffee during processing and indicate that additional processes (such as soaking or enzymatic treatment) may influence the range of changes in color parameters.