Hot air drying of purple-fleshed sweet potato with contact ultrasound assistance

Liu, Yunhong; Sun, Yanlong; Yu, Hua; Yin, Yunfei; Li, Xin; Duan, Xu

doi:10.1080/07373937.2016.1193867

Cited by 90 publications

(57 citation statements)

References 46 publications

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“…The appearance of voids and rough structures in sweet potato samples dried at higher US frequency of 60 kHz at higher infrared temperature clearly shown the difference when compared to 20 and 40 kHz dried samples. A similar phenomenon was reported by Liu et al () when sweet potatoes subjected to drying at a high temperature with high ultrasound frequency pretreatments.…”

Section: Resultssupporting

confidence: 86%

Effect of infrared drying with multifrequency ultrasound pretreatments on the stability of phytochemical properties, antioxidant potential, and textural quality of dried sweet potatoes

Rashid

Jatoi

et al. 2019

J Food Biochem

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The study aims to determine drying of sweet potatoes using multifrequency ultrasound (US) pretreatments (20, 40, and 60 kHz) at three different infrared (IR) drying temperatures (60, 70, and 80°C) and evaluate the phytochemical and textural quality of the dried product. Drying time was significantly decreased in moderate US frequency (40 kHz) at 70°C with the increasing drying temperature. Comparing to the fresh samples, the dried samples showed the highest amount of phytochemical contents. The antioxidant activity of the samples increased especially at 60 kHz and 80°C, while US‐IR treatments shown a positive impact on total carotenoids contents and β‐carotene. For phenolic compounds, Ellagic acid and Rutin were quantified in higher amount while Quercetin‐3‐rhamnoside and Quercetin 3‐β‐D‐glucoside were two new compounds identified for the first time in sweet potatoes. FTIR spectra showed the successful synthesis of OH group and phenolics in samples treated with the US at 20 kHz. Practical applications This study investigated the effects of multifrequency ultrasound with different infrared drying temperatures. The study provides evidence that infrared drying application in synergy with ultrasonic pretreatments can improve drying efficiency and food quality much better than using each method alone. Total phenolic contents and total flavonoid contents remained stable at US 40 kHz and 60°C conditions. The findings showed that moderate ultrasound frequency (40 kHz) at 60°C improved phytochemical properties while antioxidant activities showed better preservation response at 80°C with 60 kHz. In addition, the samples treated with the same US treatment at 40 kHz showed less cell breakage in SEM analysis.

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Section: Resultssupporting

confidence: 86%

Effect of infrared drying with multifrequency ultrasound pretreatments on the stability of phytochemical properties, antioxidant potential, and textural quality of dried sweet potatoes

Rashid

Jatoi

et al. 2019

J Food Biochem

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“…The oscillating signal generated by the ultrasonic generator could be transmitted to the ultrasonic transducer, after which energy conversion occurs within the transducer, consequently converting the signal into ultrasonic waves that pass into the material. In the drying process, pear materials are placed on the ultrasonic radiation disk and ultrasonic waves are directly transmitted into the pear to enhance the HAD process (Liu et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…In the drying process, pear materials are placed on the ultrasonic radiation disk and ultrasonic waves are directly transmitted into the pear to enhance the HAD process (Liu et al, 2016).…”

Section: Contact Ultrasound-assisted Hot Air Dryermentioning

confidence: 99%

Drying characteristics, microstructure, glass transition temperature, and quality of ultrasound‐strengthened hot air drying on pear slices

Liu

Zeng

Wang

et al. 2019

J Food Process Preserv

Self Cite

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In order to explore the reinforcement effect of contact ultrasound on hot air drying (HAD), the effects of different ultrasonic powers and drying temperatures on drying characteristics and quality of pear slices were studied. The results showed that the increase in ultrasonic power and drying temperature could significantly shorten drying time. The drying process of pear was internal diffusion control, and ultrasound application could reduce internal diffusion resistance as well as improve dehydration rates. SEM results illustrated that ultrasound’s cavitation and mechanical effects could produce more microchannels and dilate intercellular spaces in pear slices. DSC results revealed that ultrasound application during drying could improve water mobility and then reduce glass transition temperature. Both drying temperature and ultrasonic power had significant effects on total phenolic, total flavonoids, VC, and rehydration ratio, and contact ultrasound application in HAD was beneficial to increasing the nutrient component contents. Practical applications Hot air drying (HAD) is a traditional and frequently used drying method. Yet it has the defects of low thermal efficiency, lengthy time, and unacceptable product quality. Nowadays, the application of contact ultrasound strengthening technology has drawn great attention in drying enhancement. When contact ultrasound is applied in HAD of pear, ultrasonic energy is directly transmitted into materials without passing through any medium, so as to enhance the utilization and enhancement effect of the ultrasound. The ultrasound application could enlarge and even produce more microchannels in pear slices, which could accelerate moisture migration. Contact ultrasound application in drying process was beneficial to improving the drying rate as well as increasing nutrient components. Therefore, contact ultrasound‐strengthened HAD technology is promising and could be applied for drying agricultural products.

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“…Some studies have found that in the drying process, conditions such as drying temperature may lead to the loss of anthocyanins and the decrease of antioxidant capacity (Nayak, Berrios, Powers, & Tang, 2011; Qiu, Wang, Song, Deng, & Zhao, 2018). Additionally, characteristics such as microstructure and color will be affected (Liu et al, 2017; Onwude, Hashim, Abdan, Janius, & Chen, 2018).…”

Section: Introductionmentioning

confidence: 99%

The influence of processing conditions on kinetics, anthocyanin profile and antioxidant activity of purple sweet potato subjected to hot air drying

Wang

et al. 2020

J Food Process Engineering

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Purple sweet potato is rich in anthocyanins. The influence of hot air drying on the physical properties, anthocyanin profile and antioxidant capacity of purple sweet potato was explored at six different temperatures (60, 70, 80, 90, 100, and 110°C), three different paving densities and six different dimensions. The results show that the hot air drying kinetics of purple sweet potato were best described by the Page model. The samples dried at 60°C had the highest rehydration rate (2.64), and there was no significant difference between 80 and 60°C. There were no significant differences among the colors of the samples dried at 60, 70, 80, and 90°C, but they were quite different from that dried at 110°C. Four anthocyanins were identified by HPLC–MS/MS as cyanidin 3‐sophoroside‐5‐glucoside, peonidin 3‐sophoroside‐5‐glucoside, cyanidin 3‐p‐hydroxybenzoylsophoroside‐5‐glucoside and peonidin 3‐p‐hydroxybenzoylsophoroside‐5‐glucoside and determined by HPLC‐DAD, and the anthocyanin contents of the samples dried at 80°C were 609.08 ± 3.26, 82.75 ± 0.33, 265.88 ± 0.93, and 179.74 ± 1.35 mg/100 g DW, respectively. The highest ORAC antioxidant capacity was found in samples dried at 80°C (130.94 ± 2.59 μmol TE/g). Based on these studies, 80°C is most suitable for the hot air drying of purple sweet potato. Practical applications Purple sweet potatoes have good antioxidant capacity, which is good for health and loved by consumers. Fresh purple sweet potatoes are not easy to store, but the storage time can be prolonged after hot air drying. This study detected the influence of hot air drying on the drying kinetic, color, rehydration, microstructure, and anthocyanin content of purple sweet potato. Compared with dimension and paving density, the influence of drying temperature is greater. Among six temperatures, 80°C is most suitable for the hot air drying of purple sweet potato. This study provides a theoretical basis for the development and utilization of purple sweet potato as a functional food.

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Hot air drying of purple-fleshed sweet potato with contact ultrasound assistance

Cited by 90 publications

References 46 publications

Effect of infrared drying with multifrequency ultrasound pretreatments on the stability of phytochemical properties, antioxidant potential, and textural quality of dried sweet potatoes

Effect of infrared drying with multifrequency ultrasound pretreatments on the stability of phytochemical properties, antioxidant potential, and textural quality of dried sweet potatoes

Drying characteristics, microstructure, glass transition temperature, and quality of ultrasound‐strengthened hot air drying on pear slices

The influence of processing conditions on kinetics, anthocyanin profile and antioxidant activity of purple sweet potato subjected to hot air drying

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