| Gardenia jasminoides Ellis is the first edible and pharmaceutical resources,which is issued by Ministry of Health. It is considered as "antibiotic" in Chinese herbal medicines. Gardenia yellow pigment in the fruit is the main biologically active components. It is a non-toxic, safe, natural pigment, which has a certain nutritional value and does good to our health. In order to make better use of the prolific Gardenia resources in Fujian province,Gardenia jasminoides Ellis cv. Fenguan No.1 was used as material in this paper, discussed the varying content of Gardenia yellow pigment in all development periods. And hot air-microwave vacuum drying technology was applied to Gardenia fruits, with the using of which the hot air drying and microwave drying characteristics of Gardenia fruit were systematically studied in this paper. On the basis, quadratic rotation-orthogonal combination design was used for experimental design, combined with response surface methodology to determine the optimal procedure parameters of hot air-microwave vacuum drying in Gardenia. The main results were as follows.1. Gardenia yellow pigment content arised to peak at the 20th week after the fruit ripened. The content of Gardenia yellow pigment absorbance in the integral fruit were 1.122,1.987, 1.738, the same with b* values of the peak value. There may be some association between them. If Gardenia yellow pigment was mainly extracted from Gardenia fruits for natural edible pigment or medicine, the fruits of the 20th week were good. At this time, the Gardenia color turned from red to yellow, totally mature, and the content of Gardenia yellow pigment is the highest.2. There were significant differences among different drying methods on the gardenia fruits sensory quality. Hot air-vacuum microwave drying gardenia fruit had the most sensory quality than the hot air drying, vacuum drying, microwave drying, vacuum microwave drying and vacuum microwave-hot air drying.3. Blanching pretreatment had some effect on color, PPO activity and organizational structure of gardenia fruit, but it had little effect on Gardenia yellow pigment content. Blanched 10 minutes can effectively maintain the better color and microstructure of gardenia fruit.4. The higher the hot air temperature was, the faster the rate of gardenia fruit water loss and the shorter the drying time were. During microwave vacuum drying process, the more microwave power, microwave intensity and the less loadge were, the quicker dehydration rate of gardenia fruit water and the shorter drying time were. Vacuum degree could shorten drying time by increasing vacuum degree. However, the impact was not significant on the whole, at the same time, the equipment would be demanded to improvement of water loss rate by increasing the degree of vacuum.5. The optimum parameters of drying technology of hot air-vacuum microwave drying for Gardenia were:hot air temperature was 50℃, hot air time was 20 minutes, and microwave intensity was 8.86 W/g, and under this condition, the absorbance of Gardenia yellow pigment was 0.497, and unit energy consumption was 28.93 kJ/g. Besides, the color value of the Gardenia yellow pigment was 57.21, the OD(A238nm/A440nm) was 2.07, the extraction rate was 92.45%.6. The hot air-vacuum microwave drying is better than traditional hot air drying and vacuum microwave drying on the reserves of chemical composition such as gardenia yellow pigment. It’s better than traditional hot air drying on the reservation of color and the shape of dried samples. It’s also better than vacuum microwave drying on the color. The hot air-vacuum microwave drying and vacuum microwave drying both reduced the drying time and unit energy consumption greatly. In this way the tissue of their dried products was bulk and retained porous structure. However, the microstructure of the samples using traditional hot air drying was closely, without gaps. |
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