Dear Sahil Nain, this is done generally to exclude extra transitions accompanying the targetted one. These extra transitions may be due to residual stresses, different macromolecular structures arrangements (especially in the case of proteins) in the amorphous phase, and others. By heating-cooling cycles, the effects of such artifacts are reduced if note completely removed. My Regards

Dear Abdelkader BOUAZIZ,

Thanks for your explanation.

But, I am wondering if this heating-cooling-heating cycle could exclude the original transitions that we want to study (i.e., effect of protein / starch molecular structure).

And how to decide whether we are removing original transitions that we want to study or extra transitions that you mentioned ?

It is in the safe domain providing the protein doesn't reach the denaturation temperature, supposed known for conventional proteins. However, even so, thermal ageing/fatigue occur at extended thermal cycling.

If it is a matter of water, freeze drying is to be done prior to DSC test.

Dear Abdelkader BOUAZIZ,

Thanks for your explanation.

As you mentioned in the your first line that heating should not induced protein denaturation, otherwise we are losing something that we are going to measure, is what I think.

But I have commonly seen in research paper conducting DSC or TGA analysis doing first heating to 200 degree Celsius or above (in the heating-cooling-heating cycle), that actually denaturing the food proteins, since generally food proteins denaturation temperatures were below 200 degree Celsius. So, there is something wrong in their procedure or I am not getting this.

Also, these DSC or TGA analysis usually performed on freeze dried samples. Then, there should be no reason to conduct this ?