Quantifying the responses of three bacillus cereus strains in isothermal conditions and during spray drying of different carrier agents
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Universidade Federal de Minas Gerais
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Artigo de periódico
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Membros da banca
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Spray drying is a widely used method for producing milk powder. This process is not
aimed to cause microbial inactivation, thus sporeforming bacteria may be abundant
in the microbiota of milk powder. The first aim of this study was to determine the
inactivation kinetics parameters in capillary tubes of three Bacillus cereus strains (436,
B63, 540) in three menstrua (whole milk, phosphate buffer, and talc suspension) at 90,
100, and 110 C. D-values for B. cereus in the three menstrua were not significantly
different at the highest tested temperature (p > 0.05). Thus, talc was chosen as a
carrier agent to allow the recovery of B. cereus from spray dried materials given its
low interference on inactivation kinetics. B. cereus spores were also inoculated in whole
milk and skim milk following spray drying at 95, 105, and 110 C (outlet temperature).
After the spray drying runs, B. cereus spores were counted and the number of decimal
reductions (g) calculated. A correlation between the small diameter of the particles with
the survival of spores of three B. cereus strains was found, and B. cereus 436 presented
consistently the lowest g no matter temperature and a carrier agent. The highest g
was found when talc powder was used, which suggest that this carrier agent does not
protect B. cereus spores during spray drying. Spray drying of milk can lead to up to 4
g (strain 540) of B. cereus spores but depending on the strain less than one g (strain
436) could be observed. This study contributes to the knowledge on the microbiology of
low water activity foods by providing novel findings regarding the fate of three B. cereus
strains to different spray drying conditions. Acknowledging the variability of inactivation
of B. cereus during spray drying is key in the current context of food safety in which the
quantification of effects of unit operations must be known for the validation of processes
and development of more robust formulations.
Abstract
Assunto
Bacillus cereus, Secagem por pulverização
Palavras-chave
Spores, Low water activity, Thermal processing, Dried foods, Sporeforming bacteria, Dairy products, Milk, Foodborne pathogens
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https://www.frontiersin.org/articles/10.3389/fmicb.2018.01113/full