Comparative Study of Refractance Window and Hot Air Drying of Apple Pomace: Kinetics, Modeling, and Utilization in Pancakes

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ABSTRACT In the current study, the drying characteristics, energy consumption, physical and biochemical properties, and powder properties of hot air (HA) and refractance window (RW) dried apple pomace were investigated. Mathematical modeling and artificial neural network (ANN) modeling of drying curves were also performed. Additionally, the best sample, considering drying time, preservation of bioactive compounds, and powder properties, was used as a sugar and flour substitute in a pancake formulation. RW drying showed superior characteristics compared to HA drying, significantly reducing drying time (60–140 min vs. 140–200 min) and specific energy consumption (1.99–2.87 vs. 10.55–12.59 kWh kg −1 water), while safely decreasing water activity (0.35–0.43). The Weibull distribution model was the best among the mathematical models describing the drying curves (R 2 > 0.9977). However, ANN modeling provided higher predictive accuracy than all mathematical models (R 2 > 0.9998). Total phenolic compounds, antioxidant activity, and ascorbic acid were better preserved in RW dried samples than HA dried ones. 5‐hydroxymethylfurfural (HMF) formation was not detected in any of the samples. Both drying methods caused a perceptible color change (ΔE > 21.62) compared to the fresh pomace. Although the sample RW dried at 65°C exhibited the best flowability properties (lowest Carr index and Hausner ratio), the powder obtained from apple pomace RW dried at 75°C was selected for further use due to its overall optimal bioactive retention and shorter drying time. Apple pomace powder (APP) was added as a sugar and flour substitute in pancake formulation at different concentrations (control, 25%, 50%, and 75%), and pancakes were sensorily analyzed. As a result, it has been determined that the addition of APP to the pancake formulation at a rate of up to 50% does not show a statistically significant difference in overall acceptance compared to the control. In conclusion, the current study contributes to the zero‐waste approach and reveals the potential of apple pomace as a functional ingredient. RW drying has superior advantages compared to HA drying in terms of drying rate, energy efficiency, and retention of bioactive compounds.