Alicyclobacillus spp. are one of the major harmful microorganisms that can cause fruit juice spoilage. In this study, the inactivation activity and mechanism of phenyllactic acid (PLA) and glycerol monolaurate (GML) against Alicyclobacillus spp. were evaluated, and their effects on fruit juice quality were also investigated. The results displayed that the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of GML were 0.01–0.02 mg/mL and 0.04–0.60 mg/mL, while those of PLA were in the range of 0.25–0.50 mg/mL and 0.5–16.0 mg/mL, respectively. All of these antibacterial agents disrupted the permeability of cell membranes, destroyed the morphology of bacteria, and led to the leakage of cell contents. GML could stimulate bacteria to release a large number of reactive oxygen species, causing some oxidative damage and destroying bacteria. Treatment with L-PLA could reduce the level of adenosine triphosphate (APT) in cells by inactivating ATP synthase. In addition, the MBC of GML and L-PLA in apple juice were 0.02–0.6 and 0.25–16 mg/mL, respectively, which mainly depended on the strain difference. The treatment of L-PLA and GML had no significant adverse effect on the quality of apple juice, except that GML had some effect on color and organic acids, and L-PLA increased the total acid content. Sensory evaluation revealed that these treatments did not affect the organoleptic properties of apple juice. This study provides preliminary theoretical and data support for the application of GML and L-PLA to control Alicyclobacillus spp. contamination in apple juice.
An approach based on multifunctional fluorescent magnetic nanoparticles was proposed for the enrichment and identification of Alicyclobacillus spp. in apple juice simultaneously. The prepared Fe 3 O 4 magnetic particles (MNPs) were modified by the sol-gel process and a silica shell was formed to improve the reactivity, and then the obtained MNPs@SiO 2 -SH nanoparticles were conjugated with Thioglycolic acid functionalized CdTe/CdS QDs via thiols chemistry. The characteristic evaluation results indicated that the MNPs-QD nanocomposites exhibited good magnetic properties and optical characterization. The polyclonal anti- Alicyclobacillus IgG antibody was immobilized onto the surface of MNPs-QD materials via esterification reactions. The maximum antibody immobilization capacity was 119.62 μg/mg and the adsorption reaction could be accomplished in 60 min. The adsorption process could be represented by Langmuir model and pseudo-second order kinetics equation, respectively. Based on the high immunocapture efficiency and sensitive fluorescence characteristics, the obtained MNPs-QDs-antibody conjugates could be applied to recognize the contamination of Alicyclobacillus spp. and a quantitative analysis method was established for target cells detection. The minimum quantitative limit was 10 4 CFU (colony forming unit)/mL and the testing process could be completed in 90 min. The results indicated that the MNPs-QDs-antibody conjugates can be successfully applied for immunocapture and detection of Alicyclobacillus spp. in apple juice. That is to say, the developed MNPs-QDs-antibody conjugates have exhibit more attractive and great potential for the immunocapture and recognition of target bacteria, fully demonstrated a new method for enrichment and rapid detection of Alicyclobacillus spp. in fruit juices.
危险品化学品经营许可证（带存储）