The application of coffee silver skin extract in pomegranate juice and study for its
bioactivities

Coffee silver skin (CS) is the main by-product of coffee roasting production. It consists of various valuable chemical compositions such as phenolic acids, polyphenols, flavonoid, and so on; therefore, it is highly interesting to valorize and study for its bioactivity and potential application. Then CS was extracted by a subcritical water extraction process and freeze-dried to obtain the coffee silver skin crude extract powder (CSE). This study aimed to propose an extra beneficial drink, a CSE-pomegranate juice, and quantify the bioactive compounds in the juice. The Pomegranate juice was made from pomegranate powder and pomegranate syrup. The total phenolic content (TPC), antioxidant activity (AA), total caffeoquinic acid (T-CQA), caffeine, anti-hyaluronidase, and anti-glucosidase were studied to confirm the beneficial bioactivities of the combined juice. It was found that the CSE-pomegranate juice contained TPC=439.20 mg GAE/100 mL, AA=62.22 (mg TE/100 mL), T-CQA=12.63 (mg/100 mL), and caffeine=30.49 (mg/100 mL). The percent inhibition of hyaluronidase was 52.73%, and the percent inhibition of glucosidase was 58.15%. These results indicate that coffee silver skin dried crude extract adds more benefits to the pomegranate juice. Therefore, coffee silver skin extract (CSE) is a valuable industrial ingredient and source of antioxidative materials.