# The Effect of Type and Duration of Digestive Enzyme Treatment on Coffee Bean Composition
## 3 Results and Discussion
### Carbohydrate and Protein Contents in Coffee Beans  
In untreated green beans (Table 2), no presence of glucose was detected, and only trace amounts of fructose were found. The sucrose content in untreated Arabica beans was approximately 5.5 g/100 g dm, about 1.5 times higher than in untreated Robust beans (3.5 g/100 g dm; Table 2). Despite different units, the data presented by [PERSON] et al. [1] regarding the content of sucrose in green beans are comparable. The significant amount of sucrose observed here and the small amount of simple sugars might be related to the processing method applied to coffee fruits after harvesting [2]. Regardless of the modification variant, small amounts of simple sugars were determined in controls and samples; sucrose content was lower than in untreated beans (Table 3). It is noteworthy that the amounts of these compounds in modified samples were the smallest among all examined samples. The quantity of each tested sugar decreased with longer modification time. This trend and the occurrence of only small amounts of simple sugars suggest structural changes and efficient extraction from examined material, which could be further enhanced by enzyme activity. A similar decreasing trend over time was previously observed and linked to the absorption of solutions and rehydration of the beans [2]. Figure 2: Color of roasted coffee samples as measured in the CIELab system. There are little literature data on carbohydrate content in digested coffee, such as kopi luwak. [PERSON] [28] reported that sucrose content in green beans of three kopi luwak coffees ranged from 5.09 to 7.70%, which was similar to the amount detected in Arabica beans. From the presented data, it is evident that the applied amyloidic enzyme (\(\alpha\)-amylase) had no significant impact on the glucose content in the modified beans. This could be associated with the specificity of its action and its concentration compared to other enzymes. The presence of chlorogenic acids in coffee beans could also influence the reduction of \(\alpha\)-amylase activity [29]. After roasting, no simple carbohydrates were detected, and sucrose content could only be quantitatively determined in a few samples (Tables 2 and 4). This indicates the loss of carbohydrates due to reactions occurring during roasting, where sugars serve as important substrates, e.g., caramelization and Maillard reactions. Melanoidins are produced during those processes--they are associated with roasted coffee color. Their lower production due to overall lower carbohydrate content in controls and modified samples could have resulted in higher L* values for roasted beans. The content of soluble protein in unmodified samples was 14.9 g/100 g dm and 19.8 g/100 g dm for green Arabica and Robust beans, respectively (Table 2). In the case of modified samples (18-21 g/100 g dm and 25-27 g/100 g dm for Arabica and Robust samples, respectively), a significant increase in the content of this protein fraction was observed compared to their respective controls (3-6 g/100 g dm). Compared to untreated beans, the protein content in modified material increased by 30-40%, regardless of the enzymes used (Table 3). These changes are the result of the use of proteolytic enzymes--pepsin and trypsin. Coffee proteins could have been released from the complex structures of the beans and part of the insoluble proteins could have undergone transformations under the enzymatic activity, increasing the pool of available soluble proteins. A similar effect of enzymes on increasing the amount of soluble proteins was confirmed in a study by [PERSON] et al. [30]. The extension of the modification time generally had a significant adverse effect on the determined content of soluble proteins. In the case of untreated and enzyme-treated samples, a decrease in the content of soluble proteins after roasting was observed; generally, the values determined in those samples did not differ significantly from each other (Tables 2 and 4).