# Quantitative Analysis of Caffe in Roasted Coffee: A Comparison of Brewing Methods
## 3 Results and Discussion
### Brewing Methods
#### 3.3.1 Cold Brew  
Cold Brew represents an alternative coffee preparation method that is increasingly popular and accepted among consumers; however, a standardized definition has yet to be established [61; 62; 63]. The brewing process involves the prolonged immersion of coffee in cold water. Extraction should occur at lower than body temperature, usually at room temperature or 8 \({}^{\circ}\)C. The minimum extraction time depends on the temperature, with 2 h at 20 \({}^{\circ}\)C. Cold Brew coffee is traditionally extracted with water for 24 h [29]. The extraction of Cold Brew coffee is influenced by many factors such as coffee grade, roast and grind level, coffee-to-water ratio, temperatures, and water composition, as well as various mechanical processes (stirring, shaking, or use of ultrasonic waves) [62]. In the Cold Brew method, hot water is not used; therefore, microbiological contamination is possible [63]. High pressure during the brewing process [64] or thermal preservation [65] can reduce this risk while maintaining the quality of the beverage. The flavor profile of cold-brewed coffee differs from that of hot-brewed coffee, being fruitier and sweeter [66].  
The caffeine content in coffee prepared using the Cold Brew method showed significant variability (Table 5). It ranged from 48.00 to 180.10 mg/100 mL in brew and from 605.00 to 4080.76 mg/100 g when expressed per 100 g of coffee. These values reflect distinct measurement approaches and are not directly comparable.  
The effect of selected parameters on caffeine content was analyzed.  
In the analyzed studies, the brewing time varied from 3 h to 24 h. Additional factors, such as pressure, were used in some studies to reduce the extraction time [42; 43; 60]. Higher caffeine content was recorded with longer brewing times [39; 49]. Studies by [PERSON] et al. [44] and [PERSON] et al. [31] were conducted under similar conditions (same coffee species, identical coffee/water ratio, similar water temperature of 22-24 \({}^{\circ}\)C) but with different brewing times (3 h, 6 h or 12 h), confirmed this relationship.  
In most studies, room-temperature water was used, as in the traditional method. Several studies analyzed the effect of changing water temperature on caffeine extraction [31; 49; 59]. It was observed that increasing the temperature from 5 \({}^{\circ}\)C to 22 \({}^{\circ}\)C increased the caffeine content for a 3 h extraction and higher for a 6 h brewing [31]. On the other hand, a study by [PERSON] et al. [49] showed a similar relationship for the Arabica coffee species, but in the case of Robusta, as well as in the study by [PERSON] et al. [59], this parameter did not differentiate caffeine content.  
The coffee-to-water ratio also proved to be a significant parameter affecting caffeine content. [PERSON] et al. [47] used a coffee-to-water ratio of 5:100, achieving twice the caffeine content of [PERSON] and [PERSON] [39], who used a ratio of 10:100 under similar brewing time and temperature conditions. Additionally, a study by [PERSON] et al. [59] used a 20:100 ratio and reported higher caffeine contents in the mg/100 mL unit.  
However, no clear correlations can be shown in studies where the results are presented in the unit mg/100 g due to variation or lack of information on some parameters [29; 42; 43; 57; 58].  
These results suggest that extraction time, extraction temperature, and the ratio of coffee to water can significantly affect the caffeine content of a Cold Brew-prepared brew.