Nitric acid is strong oxidizer- no doubt, but the -CH2- groups of citric acid would likely not be oxidized, and the OH group has no alpha-hydrogen nearbly to convert it to ketone. But, would the citric acid crystals put into nitric acid be dissolved overcoming the common-ion effect? would the C-C bonds of citric acid be cleaved by nitric acid? I know nitric acid is not as hygroscopic as concentrated sulfuric acid, but what about concentrated nitric acid?

And when a metal would react with this mix, profuse amount of NO2 gas is supposed to evolve. Would it react with citric acid to convert it into some sort of Explosive?

It is precisely for this risk of explosion i am asking this question before trying it out physically.

Edit: I have mixed around 1 g of Citric acid trihydare crystals in around 1.8 g Conc. nitric acid and evaporated sloyly to dryness. What does the crystals remaining contain? (They seem like small rounder flat spot on bottom of beaker, rosette-like radiating out from a center) I cannot run any sort of FTIR/ UV-VIS/ TA on this sample, so only knowledge of organic chemistry is of help fopr me as of now.