# Characterization of Coffee Silver Skin as Potential Food-Safe Ingredient
## 3 Results
### Characteristics of CSS Composition  
Table 2 reports data on the composition of CSS. As previously mentioned, CSS is a low-moisture ingredient due to the roasting step that also lowers the a\({}_{W}\) value. Our results are close to data from [PERSON] et al. [9] (4.76 \(\pm\) 0.10 g/100 g). [PERSON] et al. [33] substituted wheat flour with different concentrations of CSS (2.5, 5.0, and 7.5%) for cookie production, observing darker products. Similarly, [PERSON] et al. [15] used CSS as a substitute for sucrose in combination with stevia at concentrations of 1.33 and 3.33 g, obtaining darker biscuits. Finally, in sponge cakes, [PERSON] and [PERSON] [34; 35], used concentrations of 20, 25, and 30% as fat replacers, observing a decrease in L* and b* values of the crumb and an increase in a* value. They also added CSS as a substitution for flour [35], observing a higher index for crumb darkness and redness and an increase in fiber content, concluding that no strong difference could be observed with additions up to 30%. Fiber content in by-products gave good results, confirming what is stated in the literature (Table 2). CSS has an average TDF content of 50% but a high ratio between IDF and SDF. [PERSON] et al. [9] also found a TDF% content of 56.4 \(\pm\) 0.70, IDF level of 49.1 \(\pm\) 0.44, and SDF of 7.30 \(\pm\) 0.07. [PERSON] et al. [10] found higher levels; their results were 67.7 \(\pm\) 1.6 (TDF%) for arabica varieties (_C. arabica_), IDF content 64 \(\pm\) 1.6, and SDF 3.7 \(\pm\) 0.0. In comparison with these results, the study presented a major SDF content of 7.86%, although other studies gave SDF% values of around 8.8% for arabica varieties (_C. arabica_) [36]. As for other compounds, this variability depends on roasting conditions, geographical provenience, and the varieties analyzed. Despite these differences, the consumption of CSS can improve the daily intake of dietary fibers, known for their beneficial role in lowering the risk of cardiovascular diseases, obesity, type 2 diabetes, chronic constipation, and other unhealthy conditions [37; 38]. Moreover, as highlighted by [39], the consumption of foods rich in dietary fibers are often good reservoirs of phenolic compounds which have antioxidant and anti-inflammatory effects. According to [40], the \begin{table}
\begin{tabular}{c c} \hline \hline a\({}_{W}\) & 0.32 \(\pm\) 0.004 \\ pH & 5.34 \(\pm\) 0.02 \\ L* & 20.8 \(\pm\) 2.62 \\ a* & 4.27 \(\pm\) 0.18 \\ b* & 13.4 \(\pm\) 0.80 \\ C* & 14.12 \(\pm\) 0.79 \\ Moisture (\%) & 2.78 \(\pm\) 0.30 \\ Ash (\%) & 6.79 \(\pm\) 0.78 \\ Proteins (\%) & 18.15 \(\pm\) 2.17 \\ Lipids (\%) & 2.31 \(\pm\) 0.50 \\ Fibers (\%) & 51.05 \(\pm\) 0.35 \\ Soluble Fibers (\%) & 7.86 \(\pm\) 1.01 \\ Insoluble Fibers (\%) & 48.85 \(\pm\) 0.83 \\ Acrylamide (\(\mu\)g kg\({}^{-1}\)) & 720 \(\pm\) 110 \\ WHC (g water/g CSS) & 4.89 \(\pm\) 0.36 \\ OHC (g oil/g CSS) & 3.02 \(\pm\) 0.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physico-chemical, color, and chemical characterization of CSS. recommended dietary reference intake (DRI) daily allowance in men aged 19-50 years is 38 g/day and in women 25 g/day, and for men aged > 51 it is 31 g/day and in women aged > 51 it is 21 g/day, although the average consumption among Americans is about 15 g/day. The quantity of dietary fibers in vegetable foods varies a lot, and the ratio of IDF and SDF differs. Cereals and some fruits, vegetables, and nuts are considered good sources of dietary fibers. For wheat (_Triticum aestivum_ L.), the common values are 11.6-17.0 g TDF, of which 10.2-14.7 g are IDF, and 1.4-2.3 g are SDF; for oats (_Avena sativa_ L.), the values are 10.3 g TDF, of which 6.5 g are IDF, and 3.8 g are SDF [41]. In apples (_Malus domesticus_), these concentrations were found to be 4.4 g TDF, 3.3 g IDF, and 1.1 g SDF; oranges (_Citrus sinensis_ L.) have 3.4 g TDF, 1.4 g SDF, and 2.0 g IDF [42]. A content of 720 \(\pm\) 110 \(\upmu\)g kg\({}^{-1}\) of acrylamide was found.