Correlation of physicochemical properties and volatile profiles with microbiome diversity in cucumber during lightly-pickling in seasoning liquid

Lightly-pickled cucumber is a popular pickled product in Asian countries. However, its quality and microbial alteration during pickling and its correlation between microorganisms and quality are still unclear. Changes in physicochemical properties, volatile organic compounds (VOCs), and microbial community during lightly-pickling cucumbers in seasoning liquid and their relationships were investigated. Results showed that the hardness and fracturability decreased with pickling time, modeled by a zero-order kinetic model. The color became brown and dark as pickling extended. Sixty-four VOCs were identified and 13 aroma-active compounds were found using GC-O and odor activity values. (E,Z)-2,6-nonadienal, hexanal, and (E,E)-2,4-heptadienal were the characteristic aroma markers essential for differentiating among the samples with different pickling times. At the genus level, Delftia and Stenotrophomonas dominated in the bacterial community, and Rhodotorula and Naganishia are the dominant fungal genera. The correlation analysis revealed that one bacteria (Acinetobacter) and two fungi (Naganishia and Rhodotorula) were strongly related to quality loss and off-flavors in cucumbers in the late pickling process. This study provides an important reference for facilitating the quality control of lightly-pickled cucumber during processing.