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Chemistry and Industry of Forest Products ›› 2021, Vol. 41 ›› Issue (1): 29-37.doi: 10.3969/j.issn.0253-2417.2021.01.005

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Effect of Post-harvest Treatment on the Product Quality of Chinese Gallnut

Wenwen ZHANG1(), Kun LI1,2,*(), Baoshan TANG1, Pinde ZHANG3, Yiwen LIU3, Hong ZHANG1   

  1. 1. Research Institute of Resources Insects, Chinese Academy of Forestry; Research Center of Engineering and Technology on Characteristic Forest Resources, National Forestry and Grassland Administration, Kunming 650224, China
    2. School of Agricultural Sciences, Xinyang Agriculture and Forestry University, Xinyang 464000, China
    3. Wufeng Chicheng Biotechnology Co. Ltd.; Research Centers of Chinese Gall Effective Cultivation and Deep Processing Engineering Technology, National Forestry and Grassland Administration, Yichang 443413, China
  • Received:2020-09-01 Online:2021-02-28 Published:2021-03-03
  • Contact: Kun LI E-mail:zhangwenwen1105@163.com;likunkm@163.com


The effects of two pretreatments, steam blanching(SB) and boiling water blanching(BWB), on fresh Chinese gallnuts were studied. After the pretreatment, oven drying(OD), fluidized bed drying(FBD), natural drying(ND), and ultraviolet irradiation(UVI) were selected to dry gallnuts and the effects of the four drying methods on the quality of the gallnut products were investigated.The results showed that: after two pretreatments, the moisture content and tannic acid content of the gallnut products decreased, especially after steam blanching, which resulted in a decrease in the moisture content to 47.68%, which was significantly different from that of untreated gallnut(55.77%). Heat treatment reduced the tannic acid content, while the gallic acid content in the dried gallnuts increased. The tannic acid content of ND gallnut was 50.12%-56.84%, and the gallic acid content was 0.29%-0.46%. After oven drying, the tannic acid content in the gallnuts decreased to 32.48%-42.43%, while the gallic acid content was as high as 2.97%-4.39%; different post-harvest treatments had different effects on the quality of the products. Boiling water blanching or steam blanching combined with ultraviolet irradiation could increase the drying rate of gallnuts and had little effect on the tannin content of the products. Oven drying and fluidized bed drying could reduce the drying time to less than 5 h, but the tannic acid content(32%-43%) in the obtained gallnut products was also reduced significantly; ND after pretreatment could maintain the original structure of tannin, but the drying time was more than 200 h.Therefore, the post-harvest treatment of fresh gallnut could be selected according to the actual operating conditions and its applications. Industries should pay more attention to drying efficiency when choosing the treatments of gallnuts; a combination of steam blanching and fluidized bed drying is more preferred.

Key words: Chinese gallnut, pretreatment, drying methods, quality

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