Utilization of watermelon rinds and sharlyn melon peels as a natural source of dietary fiber and antioxidants in cake

The aim of this work was to evaluate some physical and chemical properties of watermelon rind and sharlyn melon peel powders and its utilization as partially, substituted of wheat flour at levels of 2.5%, 5.0% and 7.5% or fat at levels of 5.0%, 10% and 15% in cake making. Watermelon rinds had higher moisture, ash, fat, protein and carbohydrates 10.61%, 13.09%, 2.44%, 11.17% and 56.00%, respectively as compared to sharlyn melon peels. On the other hand, sharlyn melon peels had higher content crud fiber (29.59%) than in watermelon rinds (17.28%). The water absorption capacity (WAC) and oil absorption capacity (OAC) of sharlyn melon peels was higher than that of watermelon rinds being 7.7, 7.13 (g water/g) and 2.24, 1.65 (g oil/g), respectively. Watermelon rinds showed significantly greater free radical scavenging activity and b-carotene (39.7% and 96.44%), respectively compared to sharlyn melon peels. It contained different types of phenolic compounds, the most abundant one was 4-hydroxybenzoic acid (958.3 lg/g dw) followed by vanillin (851.8 lg/g dw), while the lowest phenolic compound was coumaric acid (8.8 lg/g dw). On the other hand four phenolic compounds were identified in sharlyn melon peels namely, 4-hydroxybenzoic acid, vanillin, chlorgenic acid, and coumaric acid. The incorporation of WMR and SMP powders in cakes batter at all the studied levels enhanced the volume and specific volume of the baked cakes to overcome, those of the control. These materials also retard staling of cakes and inhibition the lipids oxidation and free fatty acids formation during storage. It is revealed that, substitution of 5% flour and 10% fat with watermelon rinds and sharlyn melon peels produced acceptable cakes which were not significantly different with the control.