## 3 Results and Discussion
### Physicochemical Properties
Fruit fibers addition to meat products can increase the water-holding capacity of the food matrix causing higher moisture content [35]. Also, cellulose, one of the fiber contents of the coffee silverskin derivatives can be used to entrap moisture in a variety of foods [22]. [PERSON] and [PERSON] [41] found that the addition of cellulose to chicken meatballs increased the water-holding/moisture retention capacity, but there was no statistical difference among the groups with different cellulose levels. In another study, adding amaranth and pumpkin seeds to chicken burgers increased the water-holding capacity/moisture retention [18]. TBARS is an important indicator that reflects the level of lipid oxidation in meat products. In chicken patties, replacing animal fat with CSS significantly affected the TBARS value (\(p<0.01\)). The use of CSS increased TBARS values, and the highest average value was observed in the SS3 group, which used 6% animal fat + 6% CSS (\(p<0.05\)). This could be attributed to the presence of polyunsaturated fatty acids (64%) in the CSS. It has been reported that the fat content of CSS is approximately 2-4%, with about 30% of this fat consisting of saturated fatty acids (esterified sterols, di and triacylglycerglycerol), 64% of polyunsaturated fatty acids (free fatty acids, free sterols), and 6% monounsaturated fatty acids (palmitic and linoleic acids) [19; 42]. However, [PERSON] et al. [29] found lower TBARS values in cooked chicken burgers with CSS compared to the control group. The cooking process also significantly affected the TBARS value in chicken patties produced using different levels of CSS instead of animal fat (\(p<0.01\)). TBARS values increased after cooking. The TBARS value can vary depending on the processing conditions for different meat products. It has been reported that the threshold value for perceiving bitterness due to lipid oxidation is 2 mg MDA/kg (approximately 27.75 umol MDA/kg) for some meat products [43; 44; 45]. In this study, TBARS values lower than this limit were observed in all groups and after cooking, except for the SS3 group. Color is crucial in influencing consumer preferences for meat and meat products. Changes in the color of the chicken patties during the production stage are shown in Figure 5. The addition of CSS significantly impacted the color values of chicken patties  
Figure 4: Changes in moisture contents of chicken patties during the production stages (Control: 12% fat, SS1: 10% fat + 2% silverskin, SS2: 8% fat + 4% silverskin, SS3: 6% fat + 6% silverskin). a–c Means marked with different letters in different formulations at the same production stage are statistically different from each other (\(p<0.05\)). (\(p<0.01\)). Replacing animal fat with CSS resulted in a decrease in all color properties (L*, a*, and b*) of chicken patties, and this decrease continued as the proportion of CSS increased. These results may be due to the addition of CSS, which has a value of L* 20.8, a* 4.27, and b* 13.4 reported by [PERSON] et al. [2]. Therefore, the substitution of animal fat with CSS increased the darkness (L*) while reducing the redness (a*) and yellowness (b*) of chicken patties. This is probably due to the characteristic color of CSS. It has been reported that the color of CSS depends mainly on the interaction of structural polyphenols and anthocyanins that participate in oxidation and polymerization reactions during the coffee roasting stage, and also melanoidin's formed as a result of Maillard reactions occurring during the roasting process [2]. Similar findings were reported by [PERSON] et al. [29] in CSS-added chicken burgers. [PERSON] et al. [30] also observed decreased L*, a*, and b* values with increasing levels of CSS in Irish sausages. The cooking process also affected the color properties of chicken patties (\(p<0.01\)), with an increase in L* and b* values and a decrease in a* value after cooking. The interaction between the treatment and production stages showed that the control sample had the highest L* value before and after cooking.