MATLAB: Change in Data Storage

MATLABreadwrite saving changes

Hi All,
My basic question is, has there been a change into the way data is saved (the actual structure of it) for structure files in MATLAB within the past year and a half?
Background:
I have a series of scripts which I use to process large amounts of raw data (10+GB) and save into single files (1-3GB). Since multiple users use these, I have it all built into a MATLAB standalone application which multiple users use. Previously this was all done on MATLAB 2017b. Throughout the year as I have used 2019a I have not noticed any differences either. However I recently updated to 2019b and have noticed considerable changes to my write times in the files. Additionally I have noticed even greater read times for 'new' files (all with the same scripts), even when using the same original data.
tic
who('-file','previouslyGeneratedFile.mat');
toc %0.28s
tic
who('-file','newlyGeneratedFile.mat');%Note <25% of above, using same original data set
toc %17.4s
While the top file reads the variable info in 0.28s, the bottom example takes 17.4s, and that coupled with the second file is less than a quarter size (I used the same original fileset, but what previously took ~1 hour to process now could not complete overnight).
There have been other hints that lead to write/read changes as well which I have not included here.
If anyone has noticed this issue and has a solution please let me know, because without changing anything performance has diminished past any usable limits.

Best Answer

Answering incase anyone else stumbles across this.
The answer is above as Guillaume noted that the default setting for the SAVE command had changed (see comment on how to update) and needed to be reset to save as -7.3 and NOT -7.0 as they were updated to.
Thanks again to Guillaume!
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