1NFIN8 said:

Proposition 122 said:

Increase cooking time by 5% for every 1,000 feet above 2,000 feet elevation.

Pressure cookers work by increasing the pressure inside the pot, which raises the boiling point of water, allowing food to cook faster even at lower external atmospheric pressure. BUT — at high altitudes, the starting atmospheric pressure is lower, so:

A standard pressure cooker reaches a lower absolute pressure than at sea level.

That means the boiling point is still slightly lower, and the cooking temperature is lower, even under pressure.

According to USDA and pressure cooker manufacturers:

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Water boils at 202 degrees for me at 4500 ft so I effectively get the same pressure at lower temp. Sterilization is time and pressure driven. So I have to extend sterilization time by ~78% per the maths of standard thermal death kinetics (z-value of 10°C) since I can’t raise the pressure past 15.

I might be the only one who cares about this but found it fascinating to research:

- For other sterilization (e.g., substrates in mushroom cultivation or lab use), if pressure cannot be increased, extend time proportionally—e.g., 48% longer at 3,000 feet, scaling similarly to 78% at 4,500 feet.
-  Some pressure cooker manuals (e.g., Presto) suggest a general 5% time increase per 1,000 feet above 2,000 feet for cooking, but this underestimates needs for full sterilization, where studies show higher failure rates at elevation without adjustments.

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Nope, you are not the only one
Good point, Presto is giving numbers for food prep/canning and we are interested in sterilization. Presto's 5% rule is a simplification, not derived from z-value-based thermal death kinetics.

As I understand it in a pressure canner, the gauge pressure (e.g., 15 psi) is added on top of atmospheric pressure, so the absolute pressure and the temperature achieved inside the vessel both drop with altitude for the same gauge reading. This results in a lower actual sterilization temperature at altitude, even if your dial gauge still reads 15 psi.

Every 10°C (18°F) drop requires ~10× longer time to achieve the same microbial kill. A 212°F → 202°F drop (about 5.5°C) is roughly half a log, so:
    10(5.5/10)≈3.55×time increase
I think if standard sterilization is 15 minutes at 121°C (250°F), and you only reach ~116°C (240°F), you'd need ~3.5× the time to match the same kill rate.

Since Presto's are designed for 15psi max the alternative is increased time. I know there are teks advocating increasing the weight of the jiggle weight to increase pressure (and I have done it on my previous PC without blowing myself up) some degree of caution is reasonable.

misterswisher said:

Anyone else notice discoloration in popcorn after pressure cooking? I notice it as the mycelium eats the corn. But I’ve never noticed it before they’ve been inoculated.

These just came out of a pc cycle, an extra long one just to be sure (2hrs) everything worked properly. So I’m pretty confident I can rule out bacteria, which is what I thought before. Has anyone else noticed this? I think this brand is doing it more than others. Starting to hate corn might switch to something else.

I’m thinking the hot heat converts the starches into ???(someone smarter than me help) and then it oxidizes into this brown color?

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Stipe-n Cap said:

You have to take into consideration their referencing pharma practices which clocks a 12 log reduction at like 30 mins. 2 hours is plenty for jars at any elevation.

I run all my rigs at like 18-20 psi, it's not dangerous at all and less isn't more. Longer purge, and higher psi = good timez.

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Stipe-n Cap said:

nocap said:

Also, yes, sugars can caramelize or burn to a brown color.  I’ve seen that in agar for sure.

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Never once have I witnessed the elusive "caramelization" of agar...

Quote:

Caramelization, the process where sugar breaks down and develops a characteristic flavor and color, typically occurs at temperatures above 320°F (160°C).

General Caramelization Range: Most sugars will caramelize within the range of 320°F (160°C) to 360°F (182°C).

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Dissolved solids will produce tinting but never caramelization.

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Are you sure there boss? Genuine question. I tried finding the answer myself, but failed What I do know is that it's possible, easy even, to reach caramelization temperatures(160°C) with a kettle as long as 20% of the weight in the solution is sugar. And I think that has to do with the density.

Off course agar ain't sugar, but it will without a doubt change the density right?

I am asking because I'm am pretty certain that I have witnessed caramelization while brewing. LME(liquid malt extract) is commonly used with extract brewing, as well as DME(dry malt extract). If LME is not stirred in, it'll sink to the bottom and the concentration of sugar will be way over 20% of the weight in the bottom of the kettle. If not stirred that shit will caramelize

It's not as common with DME because that shit will dissolve or float, most of the time any way, but if humidity gets in the DME it'll clump up and turn to a sugar stone, if added to a kettle with water it will start to dissolve, when that DME stone has enough moisture it will sink. If not stirred while on the bottom of the kettle I'm pretty sure that shit will caramelize as well.

Could it be that with the density from the agar-agar combined with DME clumps some caramelization is actually possible?

nocap said:

Seems likely contam in that case.

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