NWGD mini-symposium on ‘Spray drying of ferments and living bacteria’

Geplaatst door Ilse-Marte de Leeuw

zaterdag 14 november 2020

An online NWGD mini-symposium entitled ‘Spray drying of ferments and living bacteria’ was organized on 12 October 2020 to celebrate Evelien Vaessen’s PhD defence that day.

Martijn van der Hoeven from Nutricia R&D presented about ‘Fermenting more than yoghurts: infant milk ingredients produced by fermentation’, https://www.nutriciaresearch.com/our-unique-fermentation-process for more info.

Isabel Siemons, Wageningen University  presented about ‘Particle morphology linked to survival of lactic acid bacteria during drying’, the result of a joint study of Evelien Vaessen and herself, see https://www.sciencedirect.com/science/article/pii/S0260877420303538.

Prof. Romain Jeantet from Agrocampus Ouest in Rennes (France) presented ‘Improving the survival of beneficial bacteria during drying and storage by taking advantage of bacterial adaptation’.

Finally, Rian Timmermans from Wageningen Food & Biobased Research, WUR presented ‘Applications of Pulsed Electric Fields for the Food Industry’ explaining also the possibility of using PEF as a pretreatment before drying to improve drying efficiency or product quality.

In the afternoon Evelien Vaessen defended her thesis ‘Pulsed electric field pretreatment for drying of living bacteria’ successfully.

In a nutshell her PhD thesis:

Bacteria are commonly used in food industry as starter cultures or probiotic supplements. These bacteria can be stored in the powder form to prolong their shelf life. However, during the drying process bacterial inactivation occurs due to thermal and dehydration stresses. In this thesis we focused on a pre-treatment for the bacteria to increase their survival during subsequent drying processes. We provided a proof of principle that pulsed electric field (PEF) pre-treatment can be used to increase intracellular protective solutes concentrations in bacteria. This PEF treatment resulted in permeabilization of the cellular membrane upon which protective molecules in the PEF medium can diffuse into the cell.

Image: Schematic representation of the effect of PEF treatment aimed for in this thesis. Dashed lines indicate permeabilized cell membranes and solid lines intact cell membranes.

Furthermore, we showed that PEF pre-treatment can lead to increased drying robustness of bacteria when the bacteria are dried in a reconstituted skim milk medium. These insights can be used to develop and optimize drying processes aimed at high bacterial culture viability. View her last publications on the latter online:



If you missed the thesis defence of Evelien Vaessen you are still able to watch it online on the Wageningen University webpage https://www.wur.nl/en/activity/Pulsed-electric-field-pre-treatment-for-drying-of-living-bacteria.htm.

Nederlandse werkgroep drogen

De Nederlandse Werkgroep Drogen (NWGD) stimuleert de ontwikkeling en toepassing van duurzame droogtechnologie in Nederland. Sinds 1974 verbindt de NWGD droogexperts in Nederland door thematische excursies, symposia en andere activiteiten.

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