Can I pressure cook nested containers?

Question

I have some tutoring in pressure canning, and an engineering background, so please don't judge me for what is about to be a naive question.

I understand that pressure canning uses a sealed liquid environment at higher than atmospheric pressure at 250 F for a measured period of time to create a sterile environment.

I want to pack small containers of food samples fully submerged in liquid in thier respective half inch cube closeable thin glass boxes (microscope slide thickness) stacked next to each other inside the jar, to occupy the space within the jar.

They would be separateable thusly so the flavors would not mix.

These cubes would occupy the nominal headspace limit of the jar, then the jar filled with water per jar requirements.

On other words, the ingredients of the mason jar would be fully but individual sealed.

The mechanism would be an electric pressure canner.

Questions:

1. Would the pressurized water bath properly heat the cubed through thier in glass envelopes?

2. Would the mason jar do its job of maintaining a sterile environment until opened, just as it would if the ingredients were tightly packed?

3. Would the heat and pressure conditions still transmit to within the contents of the sealed cubes, given sufficient cooking time?

The purpose is to make a bento-box in glass.

Answer 1

Any container can be pressure cooked to recommended temperatures given enough time in the cooker. This may cause the food inside to become overcooked. But that's not your main problem with this setup.

When you're heat-treating a jar in a water bath, it is not completely sealed. Instead, the lid is just a little loose so that pressure, in the form of air, can escape. Then, when the jar comes out of the bath, one tightens the lid to form a tight seal.

It is clearly not possible to do this with a nested container. This means that the inner containers would either need to be unsealed (resulting in potential leakage into the other container), or would need to be tightly sealed before going into the pressure canner. Tightly sealed inner containers would have major issues with unequalized pressure between the inside and outside, particularly when they go above 100C. The "microscope slide thick" glass would certainly break, and might even explode.

If you think about it, you don't see commercially for sale foodstuffs packaged with both inner and outer canned sealed containers, and these problems are likely why. You're trying to solve an engineering problem that nobody in the industry has yet solved satisfactorily, so expect it to be very hard.