The Antioxidant Activity Of Coffee (Raw, Roasted And Spent And Black Tea

Figure 1 describe the total phenolic content of coffee (raw, roasted and spent) and black tea (raw and spent tea). Both of coffee and black tea contain reasonable amount of phenolic, however, the total phenolic compound in black tea is much higher than those of coffee, which was found to be 104.3 and 187.50 mg GAE /g in raw coffee and black tea, respectively. Similarly, the spent coffee contained less amount of phenolic (97.87mg GAE /g) than those in spent black tea (152.87 mg GAE /g). The analysis of variance showed that there was no significant (P < 0.05) difference between the total phenolic in raw and spent coffee, however, it was found significantly (P < 0.05) less in spent black tea than in raw black tea. Previous studies showed that
Figure 4 displayed the antioxidant activity of coffee (raw, roasted and spent) and black tea (raw and spent) in term of DPPH scavenging. As shown in figure 4, coffee bean has high rate of antioxidant activity, it was found significantly (P < 0.05) higher in raw followed by spent and roasted coffee 76.79, 72.93 and 59.37%, respectively. The degradation of antioxidant activity of coffee might be due to the degradation of native antioxidants and the formation of new ones. Thus, the antioxidant capacity of coffee is related to the presence of both natural constituents and compounds formed during processing (roasting) (Vignoli et al., 2011). For black tea, it was observed that the antioxidant activity of raw and spent is significantly (P < 0.05) the same. It was ranged between 57.83 and 59.27%, however, it was significantly lower than the rate of antioxidant activity in coffee. The trend observed in DPPH results were the same with total phenolic compound and total flavonoids content. Thus, fundamentally the DPPH scavenging ability may depend on the amount of total phenolic compound and total flavonoids content in the coffee and black tea extracts. The results are in agreement with the statement reported by Lee et al. (2008) who stated that extracts enriched with flavonoids or phenolic showed much higher DPPH scavenging ability than those of the other extracts. Moreover, Romdhane et al. (2015) found that antioxidant activity of coffee residual was range between 64.57 and 52.83%. On the other hand, extraction of antioxidants from old black tea leaves (OTL) and black tea wastes (BTW) using hot water show high extraction yield and antioxidant activities as identified from the work of Farhoosh et al.