Functional and antioxidant properties of novel snack crackers incorporated with Hibiscus sabdariffa by-product

The Hibiscus sabdariffa calyxes' residue (HSR) remained after the extraction of beverage is discarded which contributes to environmental pollution. The objective of this study was to explore the suitability of incorporating different amount of HSR (0%, 1.25%, 2.5%, 3.75%, and 5.0%) in crackers to enhance dietary fiber and antioxidant content. Physicochemical properties, antioxidants activity, nutritional quality, sensory profile and microstructure properties of samples containing HSR were examined and compared with control crackers. Cracker protein and fat levels decreased as HSR increased from 0.0% to 5% while ash increased. The total dietary fiber DF increased from 3.36% to 8.17% where the highest DF was reached at 5% HSR. The content of phenols increased from 5.99 to 17.57 mg/g and total flavonoid content increased from 49.36 to 104.63 mg/g of crackers incorporated with 5% HSR. DPPH radical scavenging activity increased two fold by increasing HSR up to 5%. HSR containing crackers exhibited darker L values than none/less HSR containing ones. In sensory ranking tests, acceptable crackers with pleasant flavor were obtained by incorporating up to 3.75% HSR into the cracker's formula. Crackers prepared with 5% HSR received the poorest sensory rating compared to non/less HSR enriched cracker. Scanning electron microscopy (EM) images of the prepared crackers revealed marked changes caused by incorporating HSR as upon HSR addition the surface was observed to be scratched, cracker and rougher. Overall results suggest that HSR is a potential functional food ingredient high in fiber content and antioxidants activity that may be processed into flour and used in food applications, such as baked goods.