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Applied and Environmental Microbiology, June 2000, p. 2605-2612, Vol. 66, No. 6
Teagasc, Dairy Products Research Center,
Moorepark, Fermoy, County Cork,1 and
Department of Microbiology, University College Cork,
Cork,2 Ireland
Received 10 September 1999/Accepted 20 February 2000
Spray drying of skim milk was evaluated as a means of preserving
Lactobacillus paracasei NFBC 338 and Lactobacillus
salivarius UCC 118, which are human-derived strains with
probiotic potential. Our initial experiments revealed that NFBC 338 is
considerably more heat resistant in 20% (wt/vol) skim milk than UCC
118 is; the comparable decimal reduction times were 11.1 and 1.1 min, respectively, at 59°C. An air outlet temperature of 80 to 85°C was optimal for spray drying; these conditions resulted in powders with
moisture contents of 4.1 to 4.2% and viable counts of
3.2 × 109 CFU/g for NFBC 338 and 5.2 × 107 CFU/g for UCC 118. Thus, L. paracasei NFBC
338 survived better than L. salivarius UCC 118 during spray
drying; similar results were obtained when we used confocal scanning
laser microscopy and LIVE/DEAD BacLight viability
staining. In addition, confocal scanning laser microscopy
revealed that the probiotic lactobacilli were located primarily in the
powder particles. Although both spray-dried cultures appeared to be
stressed, as shown by increased sensitivity to NaCl, bacteriocin
production by UCC 118 was not affected by the process, nor was the
activity of the bacteriocin peptide. The level of survival of NFBC 338 remained constant at ~1 × 109 CFU/g during 2 months
of powder storage at 4°C, while a decline in the level of survival of
approximately 1 log (from 7.2 × 107 to 9.5 × 106 CFU/g) was observed for UCC 118 stored under the same
conditions. However, survival of both Lactobacillus strains
during powder storage was inversely related to the storage temperature.
Our data demonstrate that spray drying may be a cost-effective way to
produce large quantities of some probiotic cultures.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Comparative Survival Rates of Human-Derived Probiotic
Lactobacillus paracasei and L. salivarius
Strains during Heat Treatment and Spray Drying
*
Corresponding author. Mailing address: Teagasc, Dairy
Products Research Center, Moorepark, Fermoy, Co. Cork, Ireland. Phone: 353-25-42229. Fax: 353-25-42340. E-mail:
pross{at}moorepark.teagasc.ie.
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