Effect of shear rate and oxygen stresses on the survival of Lactococcus lactis during the atomization and drying stages of spray drying: a laboratory and pilot scale study

Ghandi, Amir, Powell, Ian B., Howes, Tony, Chen, Xiao Dong and Adhikari, Benu (2012) Effect of shear rate and oxygen stresses on the survival of Lactococcus lactis during the atomization and drying stages of spray drying: a laboratory and pilot scale study. Journal of Food Engineering, 113 2: 194-200. doi:10.1016/j.jfoodeng.2012.06.005


Author Ghandi, Amir
Powell, Ian B.
Howes, Tony
Chen, Xiao Dong
Adhikari, Benu
Title Effect of shear rate and oxygen stresses on the survival of Lactococcus lactis during the atomization and drying stages of spray drying: a laboratory and pilot scale study
Journal name Journal of Food Engineering   Check publisher's open access policy
ISSN 0260-8774
1873-5770
Publication date 2012-11
Sub-type Article (original research)
DOI 10.1016/j.jfoodeng.2012.06.005
Volume 113
Issue 2
Start page 194
End page 200
Total pages 7
Place of publication London, United Kingdom
Publisher Elsevier
Collection year 2013
Language eng
Abstract The effect of shear rate and oxygen injury during atomization and the combination of these factors on the survival of Lactococcus lactis subsp. cremoris in spray drying was studied using laboratory and pilot scale spray dryers. The atomization was carried out using a two-fluid nozzle in the laboratory study and a two-fluid nozzle or rotary atomizer in the pilot scale study. The extent of oxygen-induced death was determined using ascorbic acid in the feed and atomizing the feed with gaseous nitrogen. The lowest levels of bacterial death were observed at lowest characteristic shear rate and in the presence of nitrogen and ascorbic acid. Quantitative analysis showed that lower shear rate, creating an oxygen-limiting environment during atomization and drying, and using oxygen scavengers in the feed were successful in enhancing bacterial survival in spray drying. We also report for the first time that, at least for L. lactis, the extent of death during the atomization stage far outweighs death during the drying stage, and that the majority of bacterial death (up to 93%) occurs during the atomization stage. The death of bacteria was found to be less when using a rotary atomizer or when using a two-fluid nozzle atomizer at lower flow rate. This work shows that bacterial death during spray drying can be minimized by using oxygen scavengers such as ascorbic acid and/or an anaerobic atomizing medium (such as nitrogen), and by altering the spraying conditions.
Keyword Atomization
Spray drying
Survival
Shear rate
Oxygen injury
Lactococcus
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Available online: 23 June 2012.

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2013 Collection
 
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