Wheat Flour Substitution with Sacha Inchi Tea Leaf Powder: Effects on Physicochemical Properties, Starch Digestibility, and Sensory Attributes of Cookies

Abstract

Sacha inchi (Plukenetia volubilis L.) leaves are an underutilized by-product of an expanding oilseed crop, yet their use as a food ingredient remains limited. This study evaluated sacha inchi tea leaf powder (STLP) as a partial replacement for wheat flour in cookies at 0%, 2.5%, 5%, and 10% (w/w), and examined the physicochemical properties, antioxidant capacity, in vitro starch digestibility, and sensory acceptability of the cookies. Substitution with STLP significantly increased the protein, dietary fiber, and ash contents of the cookies (p ≤ 0.05). Total phenolic content and ferric-reducing antioxidant power also increased with the substitution level, particularly at 5% and 10% STLP (p ≤ 0.05). In the simulated digestion model, STLP-substituted cookies showed lower glucose release, glucose area under the curve, hydrolysis index, and predicted glycemic index than the control (p ≤ 0.05), indicating reduced starch hydrolysis in vitro. Physical properties were largely maintained at low to moderate substitution levels, whereas 10% STLP increased spread ratio and hardness, and reduced baking loss. Sensory evaluation showed that STLP substitution lowered appearance, color, smell, flavor, and overall acceptability scores compared with the control, while texture scores were not significantly affected. These findings suggest that STLP may be used as a potential ingredient to improve protein, fiber and ash contents, enhance antioxidant properties of cookies, and reduce in vitro starch hydrolysis. Although further formulation optimization is needed to balance these effects with sensory acceptability, STLP is a promising functional ingredient for bakery products and a means of valorizing an underutilized agricultural material.