Document Detail

Pilot-scale crossflow-microfiltration and pasteurization to remove spores of Bacillus anthracis (Sterne) from milk.
MedLine Citation:
PMID:  21854901     Owner:  NLM     Status:  In-Data-Review    
High-temperature, short-time pasteurization of milk is ineffective against spore-forming bacteria such as Bacillus anthracis (BA), but is lethal to its vegetative cells. Crossflow microfiltration (MF) using ceramic membranes with a pore size of 1.4μm has been shown to reject most microorganisms from skim milk; and, in combination with pasteurization, has been shown to extend its shelf life. The objectives of this study were to evaluate MF for its efficiency in removing spores of the attenuated Sterne strain of BA from milk; to evaluate the combined efficiency of MF using a 0.8-μm ceramic membrane, followed by pasteurization (72°C, 18.6s); and to monitor any residual BA in the permeates when stored at temperatures of 4, 10, and 25°C for up to 28 d. In each trial, 95 L of raw skim milk was inoculated with about 6.5 log(10) BA spores/mL of milk. It was then microfiltered in total recycle mode at 50°C using ceramic membranes with pore sizes of either 0.8μm or 1.4μm, at crossflow velocity of 6.2m/s and transmembrane pressure of 127.6kPa, conditions selected to exploit the selectivity of the membrane. Microfiltration using the 0.8-μm membrane removed 5.91±0.05 log(10) BA spores/mL of milk and the 1.4-μm membrane removed 4.50±0.35 log(10) BA spores/mL of milk. The 0.8-μm membrane showed efficient removal of the native microflora and both membranes showed near complete transmission of the casein proteins. Spore germination was evident in the permeates obtained at 10, 30, and 120min of MF time (0.8-μm membrane) but when stored at 4 or 10°C, spore levels were decreased to below detection levels (≤0.3 log(10) spores/mL) by d 7 or 3 of storage, respectively. Permeates stored at 25°C showed coagulation and were not evaluated further. Pasteurization of the permeate samples immediately after MF resulted in additional spore germination that was related to the length of MF time. Pasteurized permeates obtained at 10min of MF and stored at 4 or 10°C showed no growth of BA by d 7 and 3, respectively. Pasteurization of permeates obtained at 30 and 120min of MF resulted in spore germination of up to 2.42 log(10) BA spores/mL. Spore levels decreased over the length of the storage period at 4 or 10°C for the samples obtained at 30min of MF but not for the samples obtained at 120min of MF. This study confirms that MF using a 0.8-μm membrane before high-temperature, short-time pasteurization may improve the safety and quality of the fluid milk supply; however, the duration of MF should be limited to prevent spore germination following pasteurization.
P M Tomasula; S Mukhopadhyay; N Datta; A Porto-Fett; J E Call; J B Luchansky; J Renye; M Tunick
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of dairy science     Volume:  94     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-08-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4277-91     Citation Subset:  IM    
Copyright Information:
Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Dairy and Functional Foods Research Unit, USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038.
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