Quality Change and Bacteria Succession of Dried Carrot Stored at Different Water Activities

【Objective】 The aim of this study was to explore quality change and exogenous bacteria succession in dried carrots at different water activities (a_w), so as to provide a theoretical basis for controlling quality deterioration and prolonging shelf life of dried carrots during storage. 【Method】 Dried carrots with uniform size at different a_w levels of 0.43, 0.67, 0.78 and 0.84, respectively were stored for 50 d in sealed desiccators. Hardness, microstructure, content of β-carotene and flavor components were then determined, and the changes of exogenous bacteria abundance and succession were also analyzed. 【Result】 Results suggested that lactic acid bacteria were the dominant bacteria in dried carrots. After 50 d storage, the relative abundance of Bacillus spp. in dried carrots stored at a_w = 0.43 was significantly higher than that of other groups. However, higher a_w levels promoted the growth of Pediococcus spp., Staphylococcus spp. and Lactobacillus spp. Moreover, the higher a_w levels reduced the hardness and adhesion of dried carrots microstructure and aggravated the loss of β-carotene, a typical nutrient in dried carrots. E-nose analysis showed that higher a_w caused a decrease in olefins and ketones contents, indicating loss of characteristic flavors in dried carrots. On the other hand, the increase of amines content was attributed to growth of lactic acid bacteria. 【Conclusion】 Higher a_w promoted the growth of Pediococcus spp., Staphylococcus spp. and Lactobacillus spp., caused a decline in hardness and microstructure adhesion of dried carrots, and accelerated the loss of β-carotene, as well as the deterioration of characteristic flavors.