Discriminating between different proteins in the microstructure of acidified milk gels by super-resolution microscopy

Ruifen Li, Morten Frendø Ebbesen, Zachary J. Glover, Tanja Christine Jæger, Tijs A.M. Rovers, Birte Svensson, Jonathan R. Brewer, Adam Cohen Simonsen, Richard Ipsen, Anni Bygvrå Hougaard*

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Abstract

Super-resolution microscopy (Stimulated Emission Depletion, STED) combined with quantitative image analysis and rheology was used to study acidified milk gels with the addition of both endogenous milk proteins (i.e., liquid casein and whey protein concentrate, LCC and LWPC) and different types of whey protein ingredients. Casein and whey protein were stained separately using two different dyes prior to mixing. STED micrographs showed that added whey protein concentrate (WPC) and nano-particulated whey protein (NWP) were able to self-aggregate and attach to casein assemblies by inter-chain crosslinking. The behavior of NWP was shown to be similar to the behavior of LWPC, except that NWP formed larger aggregates with increased connectivity to the gel network. Micro-particulated whey protein (MWP) did not appear to interact with any other proteins and scattered MWP particles were visible in the mixed gels. The spatial colocalization of the fluorescence emission stemming from casein and whey protein, respectively, was highest for the system that contained only endogenous proteins. The lowest colocalization level was found for the systems with added MWP which also showed the highest image coarseness in accordance with the lowest observed G’. The systems with added LWPC or NWP exhibited thicker aggregate strands, which correlated to higher G’ compared to the other systems with WPC.

OriginalsprogEngelsk
Artikelnummer108468
TidsskriftFood Hydrocolloids
Vol/bind138
Antal sider12
ISSN0268-005X
DOI
StatusUdgivet - maj 2023

Bibliografisk note

Funding Information:
This research was jointly supported by the Danish Dairy Research Foundation and Chinese Scholarship Council, CSC . Arla Foods Ingredient (Nr. Vium, Denmark) is thanked for providing nano-particulated whey protein, micro-particulated whey protein and whey protein concentrate powders. Image acquisition and image analyses were performed at the Danish Molecular Biomedical Imaging Center (DaMBIC, University of Southern Denmark ), supported by the Novo Nordisk Foundation (NNF) (grant agreement number NNF18SA0032928 ).

Publisher Copyright:
© 2023 The Authors

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