Is an Instant Pot sufficient for "scientific sterilization"?

Question

According to this promotional post by InstaPot,

Who knew that Instant Pot can provide scientific-grade sterilization? (Actually, we did.)

Swensen and her research team concluded that “store-bought pressure cookers can be an appropriate substitute for commercial autoclaves…Only the Instant Pot brand pressure cooker was able to inactivate G. stearothermophilus endospores, which indicated that it would be the most appropriate choice for a laboratory pressure cooker.”

To what extent "appropriate substitute" as quoted in the post "scientific-grade sterilization" as found in a more normal tool like an autoclave?

Many Instant Pots can reach 15 PSI, including

• Instant Pot Max
• Instant Pot PRO™ PLUS (6-quart model only, I don't see the 8-quart making a 15 psi claim)

Specifically, I want to know if there is anything a 15 PSI InstantPot can NOT do for the purposes of sterilization that a scientific autoclave can do. Since they're claiming it's sufficient.

Answer 1

While it might work for some things it is not an acceptable replacement as it does not reach the same temperature and pressure levels that an autoclave can. An instant pot will reach 115-118°C while an autoclave exceeds that at 121-135°C. The pressure is also higher due to the increased temp with an instant pot at 10.15-11.6 psi while an autoclave hits 15-45 psi.

This means that there are levels of sterilization that an instant pot can't achieve due to not being able to get as hot.

According the the NCBI, it depends on the nature of the work undertaken and it seems the instant pot did the best work of the reviewed machines.

Instant Pot

Temperature is the cooking temperature in the cooking pot throughout the cooking process. The peak working temperature of Instant Pot® is 115°C-118°C or 239°F-244°F. However, the smart cooking programs don’t always maintain the peak temperature.

Pressure: When the liquid content in the cooking port reaches the natural boiling point (varies depending on the altitude of your location), steam builds up in the cooking pot and generates pressurization. The thermodynamics of gas indicates that in ideal cases the product of the pressure and volume of a gas is directly proportional to the temperature. Since the volume in the cooking pot is a constant, we can consider the pressure being linearly related to the temperature of the gas, and to large extent (with delaying effect) to the temperature of the liquid content. The working pressure of Instant Pot is 10.15-11.6 psi (pound-force per square inch).

Autoclave

Q: What temperature(s) can an autoclave reach? A: Autoclaves are typically designed to reach temperatures between 250°F and 275°F (121°C and 135°C).

All autoclaves operate under elevated pressure (14–45 pound-force per square inch gauge) and must therefore be manufactured with an incredibly robust construction and fitted with a number of safety features and devices to ensure they present no danger to users. One of these safety devices is the safety valve, which is the final fail-safe device for the pressure vessel should all electronic controls fail. It is imperative that the safety valve be inspected, tested, and verified to be in proper working condition based on the recommendations of the sterilizer and/or valve manufacturer, as well as local inspection and insurance agencies.

I broke the quoted part into two sections to help ensure information about the instant pot compared to the others was easier to see.

Assessment and verification of commercially available pressure cookers for laboratory sterilization

This work examines the use of commercial electric pressure cookers as an alternative method for the sterilization of media, instruments, and waste. Four commonly available brands of pressure cooker were tested for their ability to sterilize microbiological media, a variety of metal instruments, and high-titer microbial cultures. All four pressure cookers were able to sterilize these starting materials as well as a range of microbial types, including Gram-positive bacteria, Gram-negative bacteria, filamentous fungi, unicellular fungi, and mixed environmental samples.

Only the Instant Pot, however, was able to sterilize autoclave tester ampoules of Geobacillus stearothermophilus spores. These results suggest that, depending on the nature of the work undertaken, store-bought pressure cookers can be an appropriate substitute for commercial autoclaves.

Answer 2

An Instant Pot can almost perform "scientific-grade sterilization", it can steam sterilize for the purpose of food, and medicine, from the CDC,

Recognized minimum exposure periods for sterilization of wrapped healthcare supplies are 30 minutes at 121°C (250°F) [...]

From the CDC link above, at this pressure and temperature you're inactivating geobacillus stearothermophilus spores, which is the benchmark for an autoclave in many use-cases. To achieve 121°C water must be at 15 PSI. Pressure and temperature are related. Without the pressure, the water on the boiler would turn to steam and you'd be unable to heat it further. An Instant Pot can create these conditions and it subsequently passes the geobacillus stearothermophilus test.

But the CDC isn't talking about "scientific sterilization" there in a lab setting. Some things found in labs are more difficult to sterilize. Take prions for example which require hotter temperatures (and also are a concern for people caring for and disposing of bodies with Mad Cow and CJD)

Infectivity can survive autoclaving at 132-138 degrees C, and under certain conditions the effectiveness of autoclaving actually declines as the temperature is increased.

And even at those insane temperatures and pressures, it's still suggested to use a chemical bath of sodium hypochlorite for 1 hour before autoclaving. While an Instant Pot can NOT hit 132 degrees, laboratory sterilizers can reach those temperatures,

Laboratory autoclaves (also referred to as steam sterilizers) are designed to sterilize at temperatures between 190°F and 275°F (88°C and 135°C) through the use of steam.

For reference, 135°C is 31 PSI (far more pressure than the Instant Pot's best case of 15 PSI on select models). Moreover, laboratory autoclaves are often regulated by quasi-governmental agencies like American Society of Mechanical Engineers (ASME) Boiler and the European counter-part Pressure Vessel Code in the United States, and Pressure Equipment Directive (PED) in Europe. They're subject to more suggestions such as those by NIH. While ASME regulations aren't technically-required at a federal level and they're not a government agency, many states legislate the ASME requirements including mine (Texas). Things these regulations are said to consider are factors such as (I can't actually read the regulation, it's insanely expensive so I'm judging by marketing materials of products that claim to meet these demands),

• In an event of a power outage can microbes escape, how is a negative pressure system maintained?
• Is access permitted while contents are still too hot to handle?
• Where does the unit vent in the case of emergency and during regular operation?
• Is there an isolated containment and clean side?
• Are there redundant systems such that if either temperature or pressure fails, the user is notified and can not retrieve the contents under the assumption they're sterilized? Sales brochures say a double-door solves this.

So to put it another way, an Instant Pot is certainly useful for science, food, and medical purposes, but there are safety features found in laboratory units as well as higher pressures that may not be necessary except it in the most niche of cases where no precaution can be discarded.