Utilization of stale bread in fried wheat chips: Response surface methodology study for the characterization of textural, morphologic, sensory, some physicochemical and chemical properties of wheat chips

•The stale bread was successfully utilized in the production of chips.•The incorporation of stale bread flour decreased the oil uptake (by 35%) of chips.•Sensory evaluation revealed that the chips with stale bread (by 50%) flour were more preferred.•The structure of chips became firm with the addition of stale bread flour.

Wheat chips enriched with stale bread were produced and response surface methodology was used for the studying the simultaneous effects of stale bread level (0–50 g/100g), frying temperature (170–190 °C) and frying time (40–60 s) on some physicochemical, chemical, textural, morphological and sensorial properties of chips. Additionally, product optimization was performed by using ridge analysis to detect the optimum levels of process variables. The dry matter, ash, Hunter Lab a and b values of samples increased with the increasing stale bread level. Higher frying temperature caused a decrease in the hardness and water activity values. Also, addition of stale bread in the formulation of chips decreased the oil uptake of samples significantly (p < 0.01). Sensory values of wheat chips increased with the increasing stale bread level. In general, panelists preferred wheat chips enriched with stale bread compared to control sample. The addition of stale bread made the structure of chips firm and electron microscopy analysis revealed that pores and fractures of chips decreased for the samples containing stale bread, which resulted in lower oil uptake during frying.