Composition, enzyme and antioxidant activities of pineapple

Three pineapple cultivars smooth cayenne, Tainung 17, and Tainung 19 were processed into flesh, peel, and stem. Nine samples were analyzed for their proximate compositions and bromelain activity existed in their water extracts. Pineapple fleshes were rich in reducing sugars and soluble fiber whereas peel and stem were rich in crude fiber. Stem showed higher bromelain activity (102-247.3 U/mg). All 18 samples including water and ethanol extracts were quite effective in the scavenging ABTS(+)- and DPPH-radical activities and reducing power as evidenced by their low EC50 (0.98-15 mg/mL). Water extracts of stem were more effective than their ethanol extracts. The scavenging ABTS(+)-radical ability was highly related with total phenols and flavonoids. Overall, peel and stem of pineapple showed high amounts of reducing sugars and soluble fiber, and higher bromelain activity and exhibit effective antioxidant activities. These wastes of pineapple would be utilized to develop as a sweet supplement or functional product.