Optimization of guava fruit bar formulation using refractance window drying technique to enhance quality and nutrient retention
摘要
Guava pulp was successfully transformed into a nutritious guava bar using Refractance Window (RW) drying technique. Process optimization was carried out using a Central Composite Rotatable Design (CCRD), evaluating the effects of water temperature (70–90 °C), pulp thickness (3–7 mm), and total soluble solids (15–25 °Brix) on the key response parameters: drying time, ascorbic acid, hardness, L* value and overall acceptability. Water temperature had the most significant impact, followed by pulp thickness and soluble solids. Fruit bars formulated using the optimized conditions (water temperature—75.95 °C, pulp thickness—5.14 mm and total soluble solids—19.96 °Brix) yielded final product with favorable nutrient retention (ascorbic acid—134.08 mg/100 g), texture (hardness—126.97 N), colour (L* value—63.10), sensory appeal (overall acceptability—7.43), by reducing the drying duration (drying time—105.93 min). Drying kinetics under optimized conditions were analyzed using eight thin-layer models; the Logarithmic model best fit the data (R2 = 0.99), followed closely by the Demir model, confirming high predictive accuracy. Overall, RW drying demonstrated high efficiency and innovation in developing value-added guava bars with improved shelf life and nutritional quality, offering a promising solution for preserving tropical fruits.
Graphical abstract