# The Effect of Type and Duration of Digestive Enzyme Treatment on Coffee Bean Composition
## 1 Introduction  
Main constituents of green coffee beans are carbohydrates, N-containing compounds, lipids, acids and water. During the roasting process, each of those groups undergo many changes and coffee beans acquire characteristic color and aroma. The composition of green coffee affects the roasting process and sensory characteristics of the roasted coffee beans [1]. There are numerous factors that influence chemical composition of green coffee, e.g., species and variety of coffee tree, geographical origin, cultivation processes, ripeness and post-harvest processing of coffee fruits [2, 3]. Basic methods used for post-harvest processing are dry/natural method, wet method and semi-dry method [4]. There are also less conventional methods, in which production of kopi luwak needs to be included.  
Coffee known as kopi luwak has been of interest to consumers and scientists for many years. The production of kopi luwak takes place in Indonesia, where a civet cat (_Paradoxurus hermaphrodites_ ssp.) consumes ripe coffee fruits and, after digestion, excretes green coffee beans. They are later separated from manure, cleaned, dried and roasted. Kopi luwak exhibits a unique sensory profile and high market price thanks to its unique production method [5, 6]. In order to increase the supply of this coffee, adulteration or cage breeding and force-feeding of civet cats are used [6].  
Scientific interest regarding kopi luwak production concentrates mainly on microbiological aspects. [PERSON] et al. [7] and [PERSON] et al. [8] worked on the identification of microorganisms, which can participate in kopi luwak fermentation during its passage through the digestive tract. There were also experiments to produce artificial kopi luwakusing microbiota from the civet digestive tract or microorganisms isolated from its manure [9; 10; 11]. However, there is not much information regarding the effect of digestive enzyme activity on the composition of coffee.  
Proteins and carbohydrates are the main structural components in green coffee and are precursors of compounds that are very important for the quality of roasted coffee (primarily, Maillard reaction products) [1]. Pepsin (stomach) and trypsin (small intestine) are proteolytic enzymes that are active in different parts of the digestive tract. \(\alpha\)-amylase is one of the basic amyloid enzymes and is active in the mouth and small intestine. Digestive enzyme activity might affect carbohydrates and proteins present in green coffee beans and, therefore, change characteristics of the final product [4].  
Due to limited availability of fresh coffee material and the intricate nature of digestion, reconstruction of kopi luwak production in the laboratory is not always possible. Nevertheless, by drawing inspiration from this process, it becomes feasible to investigate the effect of factors akin to those encountered in the digestive tract of civet cats on readily available coffee material. Therefore, this study investigated the effect of typical proteolytic and amyloid enzymes present in the animal digestive tract and the duration of such enzymatic modification on compositional changes in both green and roasted coffee beans. The analysis focused on both fundamental and coffee-specific components commonly associated with coffee quality.