Ultrasound pretreatment enhances drying efficiency and phenolic retention in raspberries during heat pump drying by modulating cell wall structure and water status
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
Prolonged drying time and substantial loss of bioactive compounds remain major challenges in raspberry drying. This study investigated the effects of ultrasound pretreatment (45 kHz, 500 W, 45 °C, 5–20 min) on cell wall structure and physicochemical properties, water status, drying behavior, and phenolic content during heat pump drying. Ultrasound disrupted raspberry tissue structure, increased accessible surface area, reshaped pore size distribution, promoted pectin solubilization and depolymerization, reduced pectin molecular weight, and enhanced water mobility. These structural changes likely reduced internal resistance to water transport, which in turn shortened the drying time from 8.87 h in the control group to 5.53 h after 15 min treatment, representing a 37.7% reduction. Fifteen phenolics were identified, and US-15 showed the best preservation of anthocyanins, whose contents were 8.46%–25.52% higher than those in control group. Overall, ultrasound pretreatment improved drying efficiency and phenolic retention by remodeling cell wall architecture and promoting water redistribution. ab0005 Highlights • Ultrasound promoted the solubilization and depolymerization of pectin. li0005 • Ultrasound disrupted tissue integrity and increased cell-wall matrix porosity. li0010 • Ultrasound induced the side chains breakage of pectin. li0015 • Increased cell wall porosity and greater water freedom facilitated drying. li0020 • Ultrasound significantly increased anthocyanin content in
Abstract
Prolonged drying time and substantial loss of bioactive compounds remain major challenges in raspberry drying. This study investigated the effects of ultrasound pretreatment (45 kHz, 500 W, 45 °C, 5–20 min) on cell wall structure and physicochemical properties, water status, drying behavior, and phenolic content during heat pump drying. Ultrasound disrupted raspberry tissue structure, increased accessible surface area, reshaped pore size distribution, promoted pectin solubilization and depolymerization, reduced pectin molecular weight, and enhanced water mobility. These structural changes likely reduced internal resistance to water transport, which in turn shortened the drying time from 8.87 h in the control group to 5.53 h after 15 min treatment, representing a 37.7% reduction. Fifteen phenolics were identified, and US-15 showed the best preservation of anthocyanins, whose contents were 8.46%–25.52% higher than those in control group. Overall, ultrasound pretreatment improved drying efficiency and phenolic retention by remodeling cell wall architecture and promoting water redistribution. ab0005 Highlights • Ultrasound promoted the solubilization and depolymerization of pectin. li0005 • Ultrasound disrupted tissue integrity and increased cell-wall matrix porosity. li0010 • Ultrasound induced the side chains breakage of pectin. li0015 • Increased cell wall porosity and greater water freedom facilitated drying. li0020 • Ultrasound significantly increased anthocyanin content in dried product. li0025 simple l0005 author-highlights ab0010