Watermelon (Citrullus lanatus) rind flour: Development and characterization of a novel watermelon byproduct

Watermelon (Citrullus lanatus) is a fruit widely consumed by the Brazilian population; however, its rind is usually discarded, despite its nutritional value. This work aimed to develop a watermelon rind flour (WRF) and a fiber-rich bread. The WRF was submitted to microbiological analysis, proximate composition, antioxidant activity, and a profile of phenolic compounds. Six types of bread were developed: three using WRF (20%, 30%, and 40% of wheat flour replacement) and three control samples (only wheat flour), which were submitted to the same analysis, in addition to colorimetric properties, instrumental texture profile, and sensory evaluation (check-all-that-apply, purchase intent, and acceptance test). A high fiber content was observed in WRF (27.15%). The total concentration of phenolic compounds was 2.38 ± 0.20 mg of gallic acid equivalent per g and benzoic acid was the main compound found (73.50 mg/100 g WRF). The results of the antioxidant capacity through the DPPH method indicated a 30% reduction. The WRF 40% bread had 3.06 g of insoluble fiber, characterizing itself as a source of fiber. In the instrumental texture analysis, it was observed that bread hardness increased significantly as the WRF content increased. The formulation of the bread containing WRF is an alternative for the use of waste, favoring the development of a fiber-source product, with a functional food claim.