Incorporation of different particle-size peanut shell powder in wheat flour: effect on the dough and cookie characteristics

Peanuts are the most produced and processed industrial crops worldwide. Therefore, a considerable amount of waste is generated during its processing. In this study, the effect of peanut shells ground to different sizes (212, 500, and 800 µm) on the physical, chemical, techno-functional, and textural properties of cookies was investigated. The hardness of the dough increased and the stickiness and the dough strength decreased as the particle size decreased; however, no significant differences were observed in the textural parameters between the doughs obtained with 500 µm and 800 µm aperture-sized peanut shell powder. The addition of peanut shells to cookies was found to increase the crude fiber content by 85-100-fold, the total phenolic content by 1.5-1.8-fold, and the antioxidant activity by 2-2.4-fold. The incorporation of peanut shell powder in cookies decreased the thickness by 8–15% but increased the spread ratio by 18–33% compared to the control cookies. The hardness and the fracturability of cookies decreased by about 27–47% and 1–5%, respectively, as the particle size of peanut shell powder increased. The results suggest that peanut shells could be a noteworthy source of fiber and phenolic compounds in functional cookie production.