Welcome to Chinese Journal of Tropical Crops,

Chinese Journal of Tropical Crops ›› 2022, Vol. 43 ›› Issue (3): 614-621.DOI: 10.3969/j.issn.1000-2561.2022.03.021

• Post-harvest Treatment & Quality Safety • Previous Articles     Next Articles

Technologies of Blanching and Sulfur-free Color-protecting in Litchi Fruit During Drying Processing

GAO Zhiqiang1,2,3, SHEN Xiajun2, LIN Yuzhao2,3,4, ZENG Lingzhen2,3,4, LIN Hetong2,3,4,*()   

  1. 1. College of Food Engineering, Zhangzhou Institute of Technology, Zhangzhou, Fujian 363000, China
    2. College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
    3. Key Laboratory of Postharvest Biology of Subtropical Special Agricultural Products (Fujian Agriculture and Forestry University), Fujian Provincial Universities, Fuzhou, Fujian 350002, China
    4. Institute of Postharvest Technology of Agricultural Products, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
  • Received:2021-08-06 Revised:2021-11-30 Online:2022-03-25 Published:2022-03-23
  • Contact: LIN Hetong


Litchi fruit, with the high nutritive value and commercial potential, is an important tropical and subtropical fruit in south China. However, the harvested litchi fruit is prone to quality deterioration such as rot occurrence, pericarp browning and pathogen infection in high temperature and high humidity seasons. Thus, litchi fruit is often processed into different commercial products in addition to fresh-eating, especially dried litchi. Due to the long drying processing time, the dried litchi is highly susceptible to serious pericarp browning development, resulting in the loss of appearance color, product quality and fruit flavor of the dried litchi, and eventually limit the sustainable development of litchi processing industry. Therefore, it is necessary to develop a safe and effective drying processing technology for the dried litchi fruit to delay pericarp browning, stabilize appearance color and improve quality of the dried litchi fruit. Some studies reported that the technologies of blanching and sulfur-free color protection liquids could effectively control the occurrence of enzymatic browning during drying processing by inactivating the activity of polyphenol oxidase (PPO), and thus improve the product quality of the dried horticultural products. However, there are few reports on delaying pericarp browning development and maintaining appearance quality in the dried litchi during hot-air drying processing by using the safe color-protecting technology. Therefore, in this study, in order to control the pericarp browning of litchi fruit during hot-air drying, the technologies of blanching and sulfur-free color-protecting in litchi fruit during drying processing were studied. An L9(34) orthogonal experimental design was used to investigate the effects of different blanching conditions such as blanching temperature and blanching time with different concentration of citric acid, and different sulfur-free color protection liquids including citric acid, sodium chloride (NaCl) and ascorbic acid, on the inactivation of PPO in the pericarp of litchi fruit, which would help to obtain the optimal parameters of blanching and sulfur-free color-protecting in litchi fruit during drying processing. The results displayed that the blanching temperature 95℃, blanching time 3 min and 0.3% citric acid were the optimum blanching conditions for dried litchi fruit during processing. Additionally, the application of the sulfur-free color protection liquids including 0.2% citric acid, 2.0% NaCl and 0.3% ascorbic acid for litchis revealed the best color-protecting of dried litchis. The data indicated that the above optimized parameters could effectively suppress the occurrence of pericarp browning in litchi fruit during drying processing, and thus maintain the better quality of dried litchi fruit.

Key words: litchi, fruit, drying, blanching, sulfur-free color-protecting

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