Abstract
Previous studies suggest that increased intracellular trehalose concentrations can result in increased robustness of probiotics and starter cultures after processing. We evaluated whether pulsed electric field (PEF) pre-treatment, resulting in increased intracellular trehalose concentrations, can lead to enhanced survival during spray drying and subsequent storage and what the effect of the carrier matrix during drying herein is on survival. The applied PEF pre-treatment resulted in increased survival of Lactobacillus plantarum WCFS1 after spray drying and subsequent storage in reconstituted skim milk (RSM), though not in the other evaluated carrier matrices. The same PEF pre-treatment in lactose instead of trehalose electroporation medium resulted also in an increased survival after spray drying in RSM. Further analysis of intracellular trehalose and lactose concentrations revealed that survival after spray drying cannot only be explained by intracellular trehalose and/or lactose concentrations. Experiments with other bacterial strains indicated that strain variability cannot be neglected when designing a process aimed at enhanced bacterial survival after processing. Overall, PEF pre-treatment is promising for enhancing survival of bacteria after drying and storage, though further understanding of the applicability is required for industrial application. Industrial relevance textProbiotics and starter cultures are very common in food industry. Survival of these cultures during drying processes is essential for their application. A pulsed electric field pre-treatment resulting in increased bacterial survival after spray drying and powder storage may contribute to more energy efficient production processes of dried bacterial cultures.
Highlights
Spray drying and freeze drying can be used to stabilize micro organisms such as probiotics and starter cultures for a prolonged shelf life
In previous work we showed that pulsed electric field treatment can be used to increase intracellular trehalose in bacteria, namely in Lactobacillus plantarum WCFS1 (Vaessen et al, 2018)
We showed that pulsed electric field (PEF) pre-treatment in trehalose can increase sur vival of L. plantarum WCFS1 during spray drying in reconstituted skim milk (RSM)
Summary
Spray drying and freeze drying can be used to stabilize micro organisms such as probiotics and starter cultures for a prolonged shelf life. These heat sensitive microorganisms are often encapsulated in a carrier matrix consisting of carbohydrates and/or proteins to provide protection during the drying process and subsequent storage of the powders (Broeckx et al, 2017; Huang et al, 2017). Trehalose has been found intracellularly in Lactobacillus casei and Propionibacterium freudenreichii after pre-conditioning of these bacteria towards osmotic stresses to induce increased survival during subsequent spray drying (Gaucher et al, 2019; Huang et al, 2018). PEF pre-treatment to increase intracellular trehalose was found to lead to increased sur vival of mammalian and plant cells after subsequent processing (Dovgan, Barlič, Knežević, & Miklavčič, 2017; Phoon, Go, Vicente, & Dejmek, 2008)
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