title: Short communication: Effects of vacuum freeze-drying on inactivation of Cronobacter sakazakii ATCC29544 in liquid media with different initial inoculum levels.
abstract: Vacuum freeze-drying is an important food-processing technology for valid retention of nutrients and bioactive compounds. Cronobacter sakazakii has been reported to be associated with severe infections in neonates through consumption of contaminated powdered infant formula. In this study, effects of vacuum freeze-drying treatment for 12, 24, and 36 h on inactivation of C. sakazakii with different initial inoculum levels in sterile water, tryptic soy broth (TSB), skim milk, and whole milk were determined. Results indicated that the lethality rate of C. sakazakii in each sample increased with the extension of vacuum freeze-drying time. With initial inoculum levels of 102and 103cfu/mL, the survival of C. sakazakii in different liquid media was significantly affected by vacuum freeze-drying for 12, 24, and 36 h. In addition, the lethality rates of C. sakazakii in whole milk, skim milk, and TSB was significantly reduced compared with those in sterile water. Furthermore, whole milk showed the strongest protective role for C. sakazakii cells, followed by skim milk and TSB medium. Using the scanning electron microscope, the intracellular damage and obvious distortion of C. sakazakii cells were observed after vacuum freeze-drying for 24 and 36 h compared with the untreated sample, and the injured cells increased with the extension of vacuum-drying time. We concluded that inactivation of vacuum freeze-drying on C. sakazakii cells is related to the food matrix, and a combination with other methods for inactivating C. sakazakii is required for ensuring microbial safety of powdered infant formula.
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China; State Key Laboratory of Applied Microbiology Southern China, Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, 510070, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Jiao
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China.
authors.forename: Jina
authors.initials: J
authors.lastname: Gao
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China.
authors.forename: Xiyan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China.
authors.forename: Maofeng
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China.
authors.forename: Jiren
authors.initials: J
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Applied Microbiology Southern China, Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, 510070, China.
authors.forename: Qingping
authors.initials: Q
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Applied Microbiology Southern China, Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, 510070, China.
authors.forename: Jumei
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Center of Detection and Control of Foodborne Risk Factors, School of Food Science and Engineering, Hefei University of Technology, Hefei, 230009, China; State Key Laboratory of Applied Microbiology Southern China, Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, 510070, China. Electronic address: yeyw04@mails.gucas.ac.cn.
authors.forename: Yingwang
authors.initials: Y
authors.lastname: Ye
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D044083:Cronobacter sakazakii / Q000187:drug effects*; D005511:Food Handling; D005516:Food Microbiology; D005612:Freeze Drying; D006801:Humans; D007223:Infant; D041943:Infant Formula; D014618:Vacuum
keywords: Cronobacter sakazakii; liquid media; vacuum freeze drying