The antibacterial activity and mechanism of rhamnolipids (RLs) against Bacillus cereus spores were analyzed from the aspects of appearance, morphology, and cell membrane state. The results showed that minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of RLs were 80.0 and 160.0 mg/L, respectively. Both concentrations of RLs caused severe shrinkage and depression on the surface of spores, and disrupted the integrity and permeability of the spore cell membrane, leading to the leakage of intracellular electrolytes, DNA and proteins. In addition, RLs inhibited and inactivated B. cereus spores by various mechanisms such as decreasing heat resistance, generating oxidative stress, reducing surface adhesion, and binding to and interfering with DNA molecules. The results of this study will contribute to the development and application of RLs in the field of food safety.

In order to improve the phenomenon that frozen cooked noodles are susceptible to the formation of ice crystals and quality deterioration during storage, the effects of mannosylerythritol lipids (MELs) versus sucrose ester (SE) on the proportion of freezable water, water distribution, quality characteristics, gelatinization characteristics of wheat flour and the secondary structures of proteins in frozen cooked noodles were investigated. The results showed that the addition of 0.30%–1.10% (m/m) MELs could promote the conversion of free water to bound water in frozen cooked noodles, reduce the proportion of freezable water, and increase the binding of water to macromolecules such as protein and starch. Compared with the blank and SE groups, the quality of frozen cooked noodles made with 0.70% MELs was better, and the hardness was (4335.317 ± 48.047) g, which was 25.36% higher than that of the blank group. The tensile force and tensile distance at break were (11.22 ± 0.15) g and (69.09 ± 1.34) mm, respectively. The water absorption rate increased significantly, and the cooking loss rate was the smallest, suggesting MELs to be more effective in improving the cooking quality of noodles than SE. At the same time, MELs could effectively delay the retrogradation rate of wheat flour starch, increase the proportions of the secondary structure fractions β-sheet and α-helix, and strengthen the gluten network structure.