Abstract
The effects of ultrasound-enhanced hot air drying on the drying characteristics, microstructure and bioactive profile of germinated highland barley seeds (GHB) were studied. GHB was dried by hot air at 55 °C and 70 °C and ultrasonic intensities of 125.1 W/dm2 and 180.2 W/dm2, respectively. The results showed that when the drying temperature was 55 °C or 70 °C, the sonicated groups could shorten the drying time by 17.4–26.1% or 18.8–31.3%, respectively. Ultrasound drying at 125.1 W/dm2 and 55 °C could mostly increase the content of organic selenium and the rehydration rate, improve the color and maintain the original structure of GHB. Compared with hot air drying alone, the phenolic content did not increase due to ultrasound-enhanced hot air drying. Therefore, drying at an ultrasonic intensity of 125.1 W/dm2 and a temperature of 55 °C could effectively shorten the drying time, and enhance the quality of GHB.
Highlights
Highland barley (Hordeum vulgare L.), as a kind of hulless barley, is a principal food crop in Tibet and the only food crop in China that grows at high altitudes of 4200–4500 m [1,2]
Lazo-Vélez et al [9] found that the total selenium content of selenium-enriched germinated soybeans increased significantly after adding different concentrations of sodium selenite solution, and the total selenium content was at least 100 times higher than that of non-selenium-enriched germinated soybeans
6 g of germinated highland barley seeds (GHB) was placed in a tray, with a fixed wind speed of 4 m/s, drying temperatures of 55 ◦C and 70 ◦C, ultrasonic intensities of 125.1 W/dm2 and 180.2 W/dm2, and a drying mode of 5 s on/5 s off [16], and the hot air drying treatment group was a control
Summary
Highland barley (Hordeum vulgare L.), as a kind of hulless barley, is a principal food crop in Tibet and the only food crop in China that grows at high altitudes of 4200–4500 m [1,2]. Highland barley is rich in nutrients, such as protein, dietary fiber and vitamins, unsaturated fatty acids, lysine and phytosterols, especially phenolic compounds [3,4]. These bioactive substances confer various physiological functions to highland barley, such as reducing hyperlipidemia and diabetes risk, and preventing chronic diseases [4,5]. The contents of folic acid, γ-aminobutyric acid, phenolic compounds, and other bioactive substances in grain can be increased [8]. Germination is an effective means to enrich selenium in grain. Selenium-enriched grains, such as brown rice and wheat, have been studied, studies on selenium-enriched highland barley have rarely been reported [7,10]
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