Innovative hybrid strategy for quality improvement of Goji tea: ultrasonic–ethyl oleate pretreatment combined with heat pump drying

• Published in: Journal of the science of food and agriculture 2024-10, Vol.104 (13), p.8162-8170
• Main Authors: Wang, Zhaokai, Ren, Guangyue, Liu, Wenchao, Duan, Xu, Zhao, Yike, Yuan, Yunxia, Liu, Gangtian, Zhang, Hui, Wang, Libo
• Format: Article
• Language: English
• Subjects: Antioxidants - chemistry; Berries; Color; Desiccation - instrumentation; Desiccation - methods; Drying; Flavonoids; Flavonoids - analysis; Flavonoids - chemistry; Food Handling - instrumentation; Food Handling - methods; Food industry; Food Preservation - instrumentation; Food Preservation - methods; Food quality; Freeze Drying; Fruit - chemistry; Fruits; functional components; Goji tea; Heat exchangers; heat pump drying; Heat pumps; Hot Temperature; Lycium barbarum; Magnetic properties; Magnetic resonance imaging; Moisture content; NMR; Nuclear magnetic resonance; Nutrient retention; Oleic Acid - chemistry; Polyphenols - chemistry; Pretreatment; Quality control; Quality Improvement; Rehydration; rehydration characteristics; Retention; Scanning electron microscopy; Scavenging; Shelf life; Ultrasonics - methods; Water absorption; Water content; Water distribution; Water engineering; Water infiltration
• ISSN: 0022-5142; 1097-0010; 1097-0010
• DOI: 10.1002/jsfa.13648

BACKGROUND Goji berries, renowned for their nutritional benefits, are traditionally dried to extend shelf life and preserve quality. However, conventional drying methods often result in uneven drying, color loss and reduced rehydration capacity. This study investigates an innovative hybrid strategy combining ultrasonic–ethyl oleate (US+AEEO) pretreatment with heat pump drying (HPD) to enhance the drying process of Goji berries. RESULTS Fresh Goji berries underwent US+AEEO pretreatment, which significantly disrupted the waxy layer, enhancing drying efficiency and water infiltration during rehydration. Compared to freeze drying (FD), HPD combined with US+AEEO pretreatment resulted in higher retention of total polyphenol content (TPC) and total flavonoid content (TFC) in the Goji soaking soup. Specifically, the HPD‐US+AEEO samples exhibited the highest TPC and TFC levels, significantly outperforming FD samples. Additionally, the DPPH and ABTS antioxidant assays demonstrated higher scavenging activities in HPD‐US+AEEO samples. The rehydration kinetics revealed that HPD samples had a superior rehydration rate and final moisture content compared to FD samples. Low‐field nuclear magnetic resonance and magnetic resonance imaging analyses confirmed enhanced water distribution and higher mobility in HPD‐US+AEEO samples. Scanning electron microscopy indicated a more porous structure in US+AEEO‐treated samples, facilitating better water absorption and functional component retention. CONCLUSION The combination of US+AEEO pretreatment with HPD significantly improves the drying process of Goji berries, enhancing nutrient retention, color preservation and rehydration properties. This innovative drying method offers a promising solution for producing high‐quality dried Goji berries, benefiting both the food industry and health‐conscious consumers. © 2024 Society of Chemical Industry.