Water Diffusion from a Bacterial Cell in Low‐Moisture Foods. Issue 9 (9th August 2016)

• Record Type: Journal Article
• Authors: Syamaladevi, Roopesh M.; Tang, Juming; Zhong, QingPing
• Is Part Of: Journal of food science. Volume 81:Issue 9(2016)
• Page Start: R2129
• Page End: R2134
• Publication Date: 2016-08-09
• Subjects: Enterococcus faecium -- low‐moisture foods -- mathematical modeling -- sorption isotherm -- water activity; Food -- Periodicals; Food -- Research -- Periodicals; Food -- Periodicals; Research -- Periodicals; Levensmiddelen; Voeding; 664
• DOI: 10.1111/1750-3841.13412
• Languages: English
• ISSNs: 0022-1147

Abstract

Abstract: We used a Fick's unsteady state diffusion equation to estimate the time required for a single spherical shaped bacterium (assuming Enterococcus faecium as the target microorganism) in low‐moisture foods to equilibrate with the environment. We generated water sorption isotherms of freeze‐dried E. faecium . The water activity of bacterial cells at given water content increased considerably as temperature increased from 20 to 80 °C, as observed in the sorption isotherms of bacterial cells. When the water vapor diffusion coefficient was assumed as between 10 −12 and 10 −10 m 2 /s for bacterial cells, the predicted equilibration times ( t eq ) ranged from 8.24×10 −4 to 8.24×10 −2 s. Considering a cell membrane barrier with a lower water diffusion coefficient (10 −15 m 2 /s) around the bacterial cell with a water diffusion coefficient of 10 −12 m 2 /s, the t eq predicted using COMSOL Multiphysics program was 3.8×10 −1 s. This result suggests that a single bacterium equilibrates rapidly (within seconds) with change in environmental humidity and temperature.