Physicochemical, antioxidant, microstructural, and sensory characteristics of biscuits as affected by addition of onion residue

Onion residue, obtained from onion processing, is valuable source of health-promoting compounds including polyphenols, mainly quercetin. In this study, biscuits were prepared by enrichment with onion residue (OS). Moreover, the influence of OS supplementation on physicochemical properties, antioxidant activities, mineral profiles, microstructural and sensory characteristics of biscuits were evaluated. Overall, the addition of OS up to 3% level significantly (p < 0.05) improved nutritional components, quercetin content, antioxidant activities and sensory scores of supplemented biscuits whereas further rises in OS caused sharply declining tendency in textural and sensorial properties. The environmental scanning electron microscopy (ESEM) results showed that OS hindered the structural formation of gluten network in biscuits and led to achieve loose biscuits. X-ray diffraction (XRD) revealed that addition of OS reduced the area of the crystallization zone. Biscuits added with OS up to 3% could be utilized as convenience foods and vehicle of improved nutritional status with health beneficial bioactive compounds. Moreover, supplementation of OS led to improvement of functional properties of biscuits as valuable source of bioactive compounds.