Hot air drying of tea flowers: effect of experimental temperatures on drying kinetics, bioactive compounds and quality attributes

Shi, Linzuo; Gu, Yanlong; Wu, Dan; XiaoQing, Wu; Grierson, Donald; Tu, Youying; Wu, Yuanyuan

doi:10.1111/ijfs.13967

Cited by 33 publications

(29 citation statements)

References 20 publications

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“…(2011) , allowing us to predict the drying kinetics at four temperatures for both fresh pulp slices and heat-treated pulp for the drying constant k , corresponding to decreasing exponential values. A direct dependence on temperature is evident; that is, at a higher drying temperature, its value increases, and this result coincides with some studies on fruits and vegetables found by other researchers ( Arslan and Özcan, 2011 ; Shi et al., 2019 ).…”

Section: Resultssupporting

confidence: 91%

Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

Márquez-Cardozo

Caballero-Gutiérrez

Ciro-Velázquez

et al. 2021

Heliyon

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The study was carried out to assess fresh slices and thermally pretreated pumpkin ( Cucurbita maxima ) dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C. The drying kinetics and quality attributes of the dried product were determined, and results indicated that the modified Page model was the best fit, with activation energies of 29.47 kJ mol −1 and 16.06 kJ mol −1 for drying fresh and thermally pretreated slices, respectively. A significant effect (p < 0.05) related to thermal pretreatment and temperature was evidenced on the physicochemical properties. The fresh pulp powders presented the following ranges of moisture and color (ΔE), 7.10%–8.31% w.b.; 21.23–25.23, respectively, and for the pretreated pulp powders, they were 8.94%–11.54% w.b., and from 19.00- 28.30, respectively. There were no significant effects on the techno-functional properties in the powders; cold water solubility was 5.36%–6.46%, water absorption capacity was 3.42–6.52 g/g, and oil absorption capacity was 1.00–1.30 g/g. The carbohydrate and fiber contents significantly decreased in the pretreated powder. An increase in antioxidant activity was found in fresh and thermally pretreated pulp powder at a temperature of 70 °C, presenting values between 2.23-2.98 μmol Trolox equivalent g −1 d.b. evaluated by the DPPH method and between 40.48-45.92 μmol Trolox equivalent g −1 d.b. by ABTS, and no significant differences (p > 0.05) were determined after pulp pretreatment. The total content of carotenoids presented retention percentages for fresh pulp powders of 52.09%, 41.92%, 30.55%, and 22.79%, while for pretreated pulp powders, they were 30.67%, 32.86%, 24.84%, and 14.71% when dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C, respectively. The powders obtained from heat-pretreated pumpkin pulp showed significant differences (p < 0.05) in physicochemical characteristics and total carotenoids, but they were not found (p > 0.05) in the techno-functional properties and antioxidant activity evaluated by the DPPH and ABTS methods.

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Section: Resultssupporting

confidence: 91%

Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

Márquez-Cardozo

Caballero-Gutiérrez

Ciro-Velázquez

et al. 2021

Heliyon

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“…Thus, it is important that a highly efficient drying process is used. So far, many investigations have been done on the hot-air drying characteristics of camellia oleifera seeds Xing, Li, Jin, Gu, & Wang, 2012;Zhang, Wu, Li, Kou, & Li, 2010) and other food materials (Li et al, 2017;Li et al, 2019;Shi et al, 2019;Wang, Jung, McGorrin, & Zhao, 2018).…”

mentioning

confidence: 99%

Microwave intermittent drying characteristics of camellia oleifera seeds

Huang

Men

Tang

et al. 2020

J Food Process Engineering

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This paper reports on an experimental investigation of the drying characteristics and kinetics of camellia oleifera seeds under microwave intermittent drying conditions. The effects of key parameters such as microwave power, heating time, and the length of the intermittent time are discussed in detail. The energy consumption in the drying process along with the main quality parameters of camellia oil, namely the peroxide and acid values, have also been determined and compared with hot‐air drying. Results show that the microwave drying curve consists of an acceleration rate period, a constant rate period and a falling rate period. As the microwave power and heating time increase, the drying time decreases. While as the length of the intermittent time increases, the drying time increases. The hot‐air drying time was found to be much longer than microwave drying time, and the energy consumed during hot‐air drying was also several hundred times higher than that used during microwave intermittent drying. The acid and peroxide values of camellia oil after hot‐air and microwave drying were both within the allowable range in the National Standard of China. The Midilli and Kucuk model was the best model to describe the kinetics of the drying process.Practical applicationsDrying is the first step in the processing of camellia oleifera seeds, which not only affects the storage of camellia oleifera seeds, but also affects the quality of camellia oil, and has thus become a research hotspot in recent years. However, several disadvantages of hot‐air drying have been identified like the slowness of the drying process and the relatively large energy consumption. Therefore, finding a drying method that is more suitable is necessary. Microwave intermittent drying is a type of discontinuous drying. The moisture and temperature inside the material can be evenly redistributed during the intermittent time, so that the material is not overheated. This feature of preserving the quality of the products to be dried has made microwave intermittent drying attractive and has been successfully applied to agricultural, forestry, and food products.

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“…Another purpose of drying is the denaturation of oxidases after the oxidation process of some teas ( Salman et al, 2021 ). Conventional drying is carried out by the application of hot air ( Shi et al, 2019 ). As with other thermal processes, drying can reduce the concentration of bioactive compounds in dry matter, and technologies have been developed to preserve these chemical compounds.…”

Section: Bioactive Composition Of Teasmentioning

confidence: 99%

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

et al. 2021

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Hot air drying of tea flowers: effect of experimental temperatures on drying kinetics, bioactive compounds and quality attributes

Cited by 33 publications

References 20 publications

Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

Microwave intermittent drying characteristics of camellia oleifera seeds

Processing, chemical signature and food industry applications of Camellia sinensis teas: An overview

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