The ultrasound-assisted hot air drying characteristics of Phyllanthus emblica was investigated in this paper. The effects of hot air temperature (60 C, 65 C, 70 C, and 75 C), ultrasonic pretreatment time (2, 4, 6, and 8 min), and ultrasonic power (200, 250, 300, and 350 W) on the drying rate, energy consumption, color change, and rehydration rate were evaluated and compared. It was found that the drying rate of Phyllanthus emblica increased with the hot air temperature. The drying time of Phyllanthus emblica with ultrasonic pretreatment was reduced by 10.0%, 25.0%, 21.4%, and 9.0% at 60 C, 65 C, 70 C, and 75 C, respectively. However, the hot air drying was not proportionally promoted by the increase of ultrasonic power or the extension of pretreatment time. Only an appropriate ultrasonic power or pretreatment time can not only improve the drying rate and rehydration rate, but also reduce the energy consumption and the total color change of the dried samples. A new drying model that considered the influences of hot air temperature, pretreatment time, and ultrasonic power was developed to fit the drying process. The results showed that the new model can accurately predict the hot air drying process of Phyllanthus emblica with and without ultrasonic pretreatment. Practical applicationsPhyllanthus emblica contains a variety of nutrients and has various biological activities. However, the harvest period and shelf life of Phyllanthus emblica is very short, and the fruit is prone to mildrew and browning after picking, which in turn leads to the loss of its nutritional and economical value. Thus, for the long-term preservation of Phyllanthus emblica, drying techniques are needed. In the food industry, hot air drying is widely used due to its low cost and easy operation; however, it also has some disadvantages such as long drying time, the oxygen-rich drying environment.These shortcomings lead to a low quality of dried materials. Ultrasonic pretreatment before hot air drying can improve drying efficiency without adversely affecting the drying quality of the material. In recent years, ultrasonic pretreatment before food drying has become a research hotspot.
The processing method of Camellia oleifera fruit used in the industry was investigated, that is, fresh C. oleifera fruit was shelled in the drying equipment first and then the remaining C. oleifera seeds returned until the target moisture content (about 10% d.b.) was reached. The variable-temperature drying of C. oleifera seeds was investigated for the first time and the drying process was optimized and compared with constant-temperature drying. Two independent variables, including hot air drying temperature and air velocity, were studied by central composite design. The responses were drying time and quality of Camellia oil, including acid value and peroxide value. Results showed that the optimal constant-temperature drying conditions were drying at a temperature of 60.5°C and air velocity of 2.1 m/s. Under this condition, the total drying time was 607 min, and the acid and peroxide values were 1.72 mg/g and 0.12 g/100 g, respectively. The optimal variable-temperature drying conditions were drying at a constant air velocity of 2 m/s and a drying temperature of 55°C for 67 min, then 60°C for 213 min, and finally 65°C for 297 min. Under these conditions, the acid value was 1.75 mg/g and the peroxide value was 0.1 g/100 g. The optimal variable-temperature drying efficiency was 16.7% higher than that of constant-temperature drying when the optimization objective of drying time, acid value and peroxide value was 2:1:1.
Infrared drying characteristics and quality variations (color change, hardness, contents of polyphenol and flavonoid) of lily bulb under blanching pretreatment are investigated. Influences of parameters such as pretreatment temperature and time, and infrared drying temperature are discussed. Effective moisture diffusion coefficient, activation energy and energy consumption were calculated. The drying time was reduced by 62.5%, 56.3% and 61.5% at 90 C compared to 60 C when blanching time was 4, 5 and 6 min, respectively. A blanching time of 5 min and drying temperature of 70 C were ideal for pretreatment and drying to maintain good color quality. Hardness value of lily bulb decreased as drying temperature and blanching time increased. 70 - 80 C was ideal drying condition to maintain good hardness quality. Blanching time and drying temperature differently affected contents of flavonoids and polyphenols of lily bulb. Basically, when blanching time was relatively long and drying temperature was relatively high, the content of flavonoids and polyphenols was high. Traditional lily bulb drying methods, sun drying and fire drying, may cause browning, and hence nutritional value and appearance quality are deteriorated. Infrared drying has high drying efficiency and good preservation of nutrients, and blanching pretreatment can effectively alleviate the degree of browning. Thus infrared drying with blanching pretreatment is ideal for lily bulb drying, however, investigations are limited. This paper presents effects of pretreatment temperature, pretreatment time and infrared drying temperature on drying kinetics and quality variations to provide guidance for storage and processing of lily bulb.
The hydrolysis acidification process is an economical and effective method, but its efficiency is still low in treating azo dye wastewater. It is therefore crucial to find more suitable and efficient means or techniques to further strengthen the process of treating azo dye wastewater by a hydrolytic acidification process. In this study, a hydrolytic acidification aerobic reactor was used to simulate the azo dye wastewater process. The change of wastewater quality during the reaction process was monitored, and the deep enhancement effect of single or composite biological intensification technology on the treatment of azo dye wastewater by the hydrolytic acidification process was also explored. Co-substrate strengthening and the addition of fructose co-substrate can significantly improve the efficiency of hydrolytic acidification. Compared with the experimental group without the addition of fructose, the decolorization ratio of wastewater was higher (93%) after adding fructose co-substrate. The immobilization technology was strengthened, and the immobilized functional bacteria DDMZ1 pellet was used to treat the simulated azo dye wastewater. The results showed that the composite technology experimental group with the additional fructose co-matrix had a better decolorization efficiency than the single immobilized bio-enhancement technology, with the highest decolorization ratio of 97%. As a composite biological intensification method, the fructose co-matrix composite with immobilized functional bacteria DDMZ1 technology can be applied to the treatment of azo dye wastewater.
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