# Characterization of Coffee Silver Skin as Potential Food-Safe Ingredient
## 3 Results
### Minerals in CSS  
Minerals are highly present in CSS [8]. As for fibers and bioactive molecules, minerals are important nutrients for human wellbeing, representing other valuable compounds to recover. We looked for those microelements that are useful for human health, such as calcium, potassium, and iron. We were able to trace out other minerals, such as phosphorous, magnesium, manganese, copper, sodium, zinc, nickel, chromium, and aluminum. The data obtained are shown in Table 4 and were compared with a few references available on mineral contents of coffee silver skin [9; 51]. [PERSON] et al. [9] reported CSS values of potassium (4977 \(\pm\) 151 mg 100 g\({}^{-1}\)), magnesium (2002 \(\pm\) 72 mg 100 g\({}^{-1}\)), calcium (584 \(\pm\) 62 mg 100 g\({}^{-1}\)), iron (41.8 \(\pm\) 2.69 mg 100 g\({}^{-1}\)), and sodium (5.32 \(\pm\) 0.14 mg 100 g\({}^{-1}\)). [PERSON] et al. [23] reported values of 470.60 \(\pm\) 13.9 (mg/kg) for aluminum and 1.64 \(\pm\) 0.34 (mg/kg) for nickel. This study confirms a high content of calcium, potassium,  
Figure 1: HPLC profile of coffee silver skin at 330 nm of phenolic acids in extract (MetOH:H\({}_{2}\)O 70:30). Identified peaks are: cafratic acid (**1**), chlorogenic acid (**2**), caffeic acid (**3**), ferulic acid (**4**), chlorogenic acid isomers (**5**–**7**). and phosphorus, and good values of iron, copper, and manganese in CSS. For aluminum, our results suggest lower contents with respect to cited data, as is the case for nickel. An important point is that CSS results to have large amounts of minerals and can be used as an integrator. [PERSON] et al. [56] remarked on how humans consume large amounts of minerals, with high needs for calcium and iron, used for bone renovation, the correct functioning of red blood cells, and cellular respiration. Magnesium, copper, selenium, zinc, iron, manganese, and molybdenum are important co-factors found in the structure of certain enzymes and are indispensable in numerous biochemical pathways. Conversely, some minerals are not involved in any biochemical pathway and can even be toxic or being used as a processing contamination index; aluminum and nickel are among them [56; 57]. Minerals can have different health effects; however, their daily requirement levels are very low (as they are micronutrients), so a small amount of CSS in a newly formulated food could remarkably increase their intake. According to the World Health Organization (WHO), the daily calcium intake, for men and women from 19-50 years old, is fixed at 840 mg daily [58]. By looking at our data, it can be assumed that in 100 g of CSS, there is about 546.5 mg of calcium, so, keeping these values in mind, an addition of 1.5% of CSS to a final amount of 45 g of a new formulated food will give 16.38 mg of calcium (2% daily requirement). In some studies [59], the daily intake of calcium (for the same target population) is lower, fat 700 mg daily. Similarly, for potassium intake, the WHO [60] recommends 3510 mg daily for adults. Following the previous example, 3g of CSS (1.5% for a 45 g final product) provides 65.7 mg of potassium (1.91% of daily requirement). According to these data, potassium can be used as a replacement for salt (NaCl) in newly formulated foods. The literature agrees that aluminum and nickel mainly come from fertilization, the high use of pesticides, and fungicides [56], which increase their content in the soil. Other causes are geographical and climatic conditions [57; 61]. Aluminum and nickel are among the most abundant metals around the globe (they are normally contained in vegetable sources) and their concentration grows steeply due to the human activities of extraction and soil and water acidification [57; 61; 62]. Recently, the European Food Safety Agency reviewed the use of aluminum sulfates (E 520-523) and sodium aluminium phosphate (E 541) as food additives due to the higher intake in the human diet [63]. The EFSA statement [64] on the evaluation of aluminum oral bioavailability has shown drinking water values close to 0.3%.