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

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. 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. 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.

Wang Z ，Ren G ，Liu W ，Duan X ，Zhao Y ，Yuan Y ，Liu G ，Zhang H ，Wang L ... -  《-》

Ultrasonic and osmotic pretreatments followed by convective and vacuum drying of papaya slices.

Papaya fruit is highly nutritive, but very fragile, and thus has a limited shelf life. Drying is essential to preserve it for longer durations. In this work, osmotic dehydration (OD) with and without ultrasound (US) was applied to papaya slices as a pretreatment in conjugation with vacuum (VD) and convective air drying (AD). Drying was carried out in a novel dryer. Moisture content, drying time, water activity, total color change, total phenolic content, radical scavenging activity, texture, and Fourier-transform infrared (FTIR) spectrums were evaluated for fresh and dried papaya slices. It was observed that US-assisted osmotic dehydration (USOD) followed by VD had the lowest drying time with highest retention of phenols and antioxidants as compared to other drying techniques. Higher phenols and antioxidants in US-pretreated samples were attributed to the release of trapped intra-cellular polyphenols by cavitation. However, the color characteristics and texture of OD pretreatment followed by convective AD slices were found to be better. Color retention could be due to carotenoid preservation, which would be degraded in other treatments, whereas lower brittleness was associated with lower pectin. Infrared spectroscopy confirmed the retention of phytochemicals and antioxidants in dried papaya slices that were subjected to pretreatment. Pretreatment before drying enhances the end product quality of dried papaya slices. The results of this study highlight that USOD-VD is effective for nutrition preservation while OD-AD is suitable for preserving physical characteristics. © 2020 Society of Chemical Industry.

Chandra A ，Kumar S ，Tarafdar A ，Nema PK ... -  《-》

Effect of ultrasound combined with chemical pretreatment as an innovative non-thermal technology on the drying process, quality properties and texture of cherry subjected to radio frequency vacuum drying.

To obtain high-quality cherry products, ultrasound (US) combined with five chemical pretreatment techniques were used on cherry prior to radio frequency vacuum drying (RFV), including carboxymethyl cellulose coating (CMC), cellulase (CE), ethanol (EA), isomaltooligosaccharide (IMO), and potassium carbonate + ethyl oleate (PC + AEEO). The effect of different pretreatments (US-CMC, US-CE, US-EA, US-IMO, US-(PC + AEEO)) on the drying characteristics, quality properties, texture, and sensory evaluation of cherries was evaluated. Results showed that the dehydration time and energy consumption were decreased by 4.17 - 20.83 % and 3.22 - 19.34 %, respectively, and the contents of individual sugars, soluble solid, total phenolics (TPC), natural active substances, total flavonoids (TFC), and antioxidant properties (DPPH, ABTS and FRAP) were significantly increased after US combined with five chemical treatments (P < 0.05). Moreover, the pretreatment played important role in improving texture properties and surface color retention in the dried cherries. According to the sensory evaluation analysis, the dehydrated cherries pretreated with US-CMC exhibited the highest overall acceptance, texture, crispness, color, and sweet taste showed lower off-odor, bitter taste and sour taste compared to control and other pretreatments. The findings indicate that US-CMC pretreatment is a promising technique for increasing physicochemical qualities and dehydration rate of samples, which provides a novel strategy to processing of dried cherry.

Zang Z ，Wan F ，Ma G ，Xu Y ，Wu B ，Huang X ... -  《-》

Hot air-assisted radio frequency drying of orange slices: Drying behavior and product quality.

This research aimed to assess the hot air-assisted radio frequency drying (HA-RFD) of orange slices to evaluate the possibility of producing high-quality dried orange slices and overcome the problem of the long drying time and the high energy consumption. The effect of electrode distance (60, 70, and 80 mm) and number of slices (1-3 slices; 4 mm thickness per slice) on the HA-RFD of orange slices was evaluated. Orange slices in three layers with a total thickness of 12 mm and an electrode gap of 70 mm were picked to dry the orange slices in the shortest time. The quality of orange slices dried with HA-RFD was compared with those of HA-dried (HAD) and freeze-dried (FD) samples. HA-RFD allowed a 67% decrease in the time of drying of the orange slices (from 1170 to 390 min) when compared to HAD. Total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, and color values were affected by the drying technique. HA-RFD showed higher TPC, TFC, and antioxidant activity than HAD. The FD samples showed the highest TPC (928 mg GAE/100 g dw), TFC (200 mg rutin/100 g dw), and antioxidant activity (67.58%). Moreover, the samples dried with HA-RFD resulted in the least color change in comparison to HAD and FD samples. Regarding vitamin C, FD samples were the best, followed by HA-RFD and HAD, respectively. Considering the final product quality, and the characteristics of drying techniques, especially drying time and drying rate, HA-RFD proved to be an alternative technique to the HAD for producing dried orange slices. PRACTICAL APPLICATION: HA-RFD was applied for the first time as an alternative technology to dry orange slices. The quality of orange samples dried by HA-RFD was compared with samples that dried by HAD and FD. The results indicated that the HA-RFD technique is a good method to dry orange slices by considering the drying characteristics and the final product quality.

Ismail M ，Özbek HN ，Göğüş F 《-》

Effect of ethyl oleate pretreatment on blueberry (Vaccinium corymbosum L.): drying kinetics, antioxidant activity, and structure of wax layer.

An K ，Fu M ，Zhang H ，Tang D ，Xu Y ，Xiao G ... -  《-》