The increasing interest in sustainability has driven research into the utilization of food by-products. Onion by-products, rich in bioactive compounds, represent a valuable resource for developing functional ingredients
however, they are prone to degradation due to environmental factors such as light, heat, and oxygen, leading to reduced efficacy and increased spoilage. Microencapsulation represents an effective approach to meet important goals in the formulation of food products such as the protection against degradation or the control of interactions with other ingredients that may modify and impair their functionality. This study explores the microencapsulation of flavonoid-rich onion by-product extract through spray drying, employing various wall materials (maltodextrin and a mixture of maltodextrin/trehalose and maltodextrin/trehalose/inulin) and their effect on the chemical and physical properties of the powders such as encapsulation efficiency, total flavonoids content, moisture content, water activity, bulk density, and bulk tapped density. The storage stability was further evaluated. This research supports waste reduction and suggests strategies for developing functional ingredients with extended shelf life and controlled release properties.