Development of functional ingredients from berry by-products: a process engineering approach to the optimization and characterization of convective drying

Abstract

Valorizing high-moisture (60–80%) berry by-products (pomace and bagasse), rich in fiber and bioactives, through optimized convective drying is critical for industrial sustainability. This doctoral research demonstrated that engineered optimization of convective drying (50–90 °C) effectively transforms raspberry, blueberry, and blackberry by-products into functional ingredients with improved techno-functional and bioactive profiles, employing kinetic modeling (Page model), physicochemical characterization, and for blackberry, advanced analyses (phase-segmented mass transfer, thermodynamics, sustainability, multivariate). Raspberry pomace at 70 °C (Page R2 >0.996) showed a 0.46 kg H2O·kg−1 db·min−1 drying rate, 34.17 kJ·mol−1 Ea, a 43.40% SDF increase (to 3.37 g·100g−1 db), retaining 32.10 mg GAE·g−1 db TPC and 25.84 mg C3G·g−1 db TAC. Blueberry pomace dried at an optimized 70 °C (Page R2 >0.996, Ea 39.55 kJ·mol−1) yielded increased SDF (4.66 g·100g−1 db) and TPC (13.65 mg GAE·g−1 db). Evaluating the 50–90 °C range, increasing temperature reduced SEC from 67.35 (50 °C) to 33.17 kWh−1·kg−1 H₂O (90 °C); the 70 °C optimum also yielded a 47% reduction in estimated production costs and lower CO2 emissions, enhancing process sustainability. For blackberry pomace, phase- segmented exergy analysis (revealing continuous drying limitations like final ηEx 0.8744 at 50 °C vs. 0.6311 at 90 °C) supported a proposed staged temperature profile (70–80 °C → 60–70 °C → 50–60 °C). This staged approach offers improved exergy efficiency, further optimized SEC, and enhanced sustainability (improved Sustainability Index, reduced CO2 emissions vs. continuous low-temperature drying), demonstrating techno- economic viability. Blackberry bagasse multivariate analysis (PCA 86.4% variance) showed maximum TPC (27.35 mg GAE·g−1 db) at 70 °C, while TAC dropped 76% at 90 °C (1.29 mg C3G·g−1 db) versus freeze-drying (8.62 mg C3G·g−1 db). These quantitative findings establish a robust engineering framework for by-product valorization, enabling targeted ingredient design. This research details these transformations, offering validated industrial strategies to convert waste into quality ingredients with improved energy efficiency, sustainability, and techno-economic viability.