white potato

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potato pressure cooker nutrition

When a potato is pressure cooked and cooled a large portion of its starch is converted into “resistant starch” – a healthier starch that isn’t fully digested and instead used by the body like fiber – lowering blood cholesterol and fats.

Resistant starch is usually found in beans, whole grains and some fruits (bananas); but, it can also be created by cooking typically starchy foods (such as potatoes, rice, pasta and bread) and then cooling them.  This “retrograded resistant starch” isn’t naturally present in these foods and can only be produced by converting common starch with cooking and cooling.

Scientists in Spain measured pressure cooked potato starch samples at 100°C (boiling),  and with pressure to 120°C (equivalent 15 psi) and 250°C using an autoclave to find out how much of the potato’s own starch would convert into resistant starch.  An autoclave is a pressure vessel used for research and industrial applications that can operate from 1 to 50psi or more (depending on the model) – they can be brought up to pressure using water-generated steam, just like a pressure cooker. Although their paper doesn’t give exact data from their findings, their conclusion was..

…. [Resistant Starch] RS yields obtained in the [High-pressure Autoclave] HPA process were greater than the ones obtained using a boiling water bath as gelatinization system.

Which basically means you can convert more of the potato’s starch into the better-for-you “resistant starch” by pressure cooking compared to boiling.  If eating cold mashed potatoes isn’t appealing, that’s OK. Reheating doesn’t destroy this newly created resistant starch – apparently it can increase it.

A BBC TV Show (Trust Me, I’m A Doctor) conducted a small experiment with cooked, cooled and reheated pasta and found that reheating continues the process of converting a food’s starch to resistant starch.  All 10 volunteers had a 50% lower blood glucose response to the “cooked, cooled & reheated” pasta compared  to the “cooked” or “cooked & cooled.” Evidence, according to the experiment’s author,  that even more resistant starch was converted during reheating.

no acrylamide? no problem!

The potato research continues with Swiss researchers who took a bunch of potatoes to steam, roast, and fry to measure how much acrylamide was produced.  Acrylamide is a carcinogenic compound that forms during high temperature cooking.  The Swiss found that this compound is primarily created during dry cooking methods like roasting or deep frying. It turns out that steaming potatoes under pressure produced almost no acrylamide compared to dry cooking methods where the potatoes reached the same temperatures (25 μg/kg versus 1500 μg/kg ). BUT, if the pressure cooking temperature is raised from the 120°C (equivalent to 15 psi) to 160°C (only achievable with an autoclave) then acrylamide will start  to develop even in the presence of steam and pressure (800 μg/kg).

Don’t worry, most potatoes need only 10 minutes at high pressure (115-120°C) to be fully cooked and these researchers pressure cooked theirs for 20.

bottom line

It is not possible to create carcinogenic acrylamide when cooking potatoes at the high temperatures that can be achieved by household pressure cookers.

Pressure cooking and cooling potatoes produces a nutritional insoluble starch which has a lower glycemic impact. It’s likely that reheating pressure cooked potatoes will increase this resistant starch further for more nutritional benefits.

Aren’t your leftovers starting to look good right about now?!?

potato pressure cooker recipes

Start your quest for resistant starch with one of our pressure cooker potato recipes…

want more?

potato_1V

references:

Andrews, Rayan. “Resistant Starch: What Is It? And Why Is It so Good for You?.” Precision Nutrition Inc, 2011. Web. 25 May 2016.

Escarpa, A., et al. “Resistant starch formation: Standardization of a high-pressure autoclave process.Journal of Agricultural and food chemistry44.3 (1996): 924-928.

van Tulken, Chris, MD. “Is Reheated Pasta Less Fattening?” BBC News Magazine, 16 Oct. 2014. Web. 20 May 2016.

Biedermann, Maurus, et al. “Methods for determining the potential of acrylamide formation and its elimination in raw materials for food preparation, such as potatoes.” Mitteilungen aus Lebensmitteluntersuchung und Hygiene 93.6 (2002): 653-667.

 

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26 Comments

  1. That is very good news! Thanks for keeping us informed. Now, if something could be done alter white rice.

  2. Sharon, there has been some research with rice in the pressure cooker – I haven’t reviewed all of the papers on it thoroughly – the jist of it is that the starch is MORE digestible immediately after pressure cooking which is the opposite of “resistant starch.”

    If you’re trying to lower GI with rice, go for parboiled rice. It’s almost already completely gelatinized and pressure cooking does not “undo” any of this. Like cooked and cooled potatoes and pasta, rice can also produce “retrograded resistant starch.”

    Ciao,

    L

  3. I do believe I read somewhere that adding a teaspoon or so of coconut oil to the water while cooking rice changes the starch.

    1. There’s a case for risotto and pilafs! However, when I follow the links to find out more I’m taken to a Washington Post article saying that this was “preliminary research” – nothing appears to have been actually published about it (I looked because I wanted to know more and see the data : ).

      Ciao,

      L

  4. This is a 20 year old study. I wonder if there are any more recent studies. Also, the conversion to resistant starch is mentioned under autoclave pressure –which pressure cookers never reach. Finally, how much is actually converted is unclear. This article is inflating the science.

    1. The food industry does not change as quickly as computer technology – data collected from potatoes 20 years ago is not going to be significantly different today. Did you know that many of the pressure canning processing times and guidelines are based on research from 1940’s and 50’s? Some USDA guidelines are based on data and research that is even older than that!

      Regarding the RS conversion, the researchers used an Autoclave for both the 120°C and 250°C measurements. They state in the paper that they did not notice any significant difference between the RS yield at both temperatures, so they so they referred to the results of both temperatures in the paper as “High-pressure Autoclave” (HPA).

      Ciao,

      L

    2. P.S. I added the following sentence to the article…

      “An autoclave is a pressure vessel used for research and industrial applications that can operate from 1 to 50psi or more (depending on the model) – they can be brought up to pressure using water-generated steam, just like a pressure cooker. ”

      Thanks for the feedback!

      Ciao,

      L

  5. I think you have the wrong link for the BBC Trust Me I’m a Doctor episode. Try this: http://www.bbc.co.uk/programmes/articles/3LncBcDcCXKgtpFvrDZVnNQ/can-my-leftovers-be-healthier-than-the-original-meal

    1. Victoria, thanks for sharing this link to the BBC site – it has more data and details than the first article I linked-to!

      Ciao,

      L

  6. Very interesting, I consume a product called UCAN Super Starch and your article has me in research mode trying to find out if I can simply use potatoes instead. I’m a obstacle course racer (mud runs, Spartan, Tough Mudder etc) and train on a low carb diet, but when I race I try to carb load without spiking my insulin levels.

    Here’s a great article on the health benefits of resistant starch; http://www.core3training.com/what-you-should-know-about-resistant-starch/

  7. This is great news since we are diabetic.
    I dry roast our rice in a pan before cooking. This also converts the starch in rice but I did not know about potatoes.
    We can now eat rice and it doesn’t make our blood sugar go so high.
    Thanks for this info. I will pressure cook the potatoes from now on. : )

  8. I try to restrict carbs to < 50 gm/day (LCHF diet or lifestyle) and have no eaten many potatoes for 2 years. It is difficult not to take a few off of someone elses plate. After reading the above, I bought some baby new potatoes and cooked the in my new Amazon Prime InstantPot..

    After cooling and reheating in the microwave, They tasted very good eaten with lots of better or sour cream. I read someone's blog about reheating the potatoes reversing starches to original glycemic index and came back here to read the article again.

    Eating fat is good for you. It is carbohydrates and INSULIN that makes you fat and diabetic.

    1. Even as diabetics we eat everything but in moderation and not daily. I prefer that we have a lot of variety in order to get enough vitamins and minerals.
      We eat potatoes often because they have a lot of vitamin C and are delicious with most proteins.
      I have been making risotto lately because I can convert the starch before adding the liquid and I still come out with a cream risotto.
      There are many ways we can modify our cooking methods so we can enjoy a variety of foods. : )

  9. Question about the “cooling” portion of this process – anything special here? Does it need to be rapidly cooled or is allowed to cool naturally ok? Cooled for a particular length of time? What temp equals “cool”? (Cool to the touch or needs to be below 40 degrees F?).

    Would I get RS by pressure cooking my pasta, rinsing with cold water until cool and then dropping back into some boiling water to reheat for serving in order to use “same day”? Or do I need to make my pasta/potatoes/rice a day or more ahead?

    Thank you!

  10. Aurora,

    I am almost to the point of buying a glucose meter to help answer that question although I am not diabetic. In looking up other articles on resistant starch, they imply that reheating loses the benefits. Insulin is the fat storage hormone and it is eating carbohydrates that make you fat. The healthiest thing you can do for you and your family is to minimize carbohydrate intake and throw away “vegetable” seed oils (PUFAs) polyunsaturated omega 6 fatty acids.

  11. IFortuna, vit C is destroyed by heat, so unless you are eating your potato raw, you aren’t getting C from it. Sorry to burst your bubble.

  12. So, as a newbie to pressure cooking in general my question is: How do I cook these in a pressure cooker; in liquid or a steamer basket?
    Thank you.

    1. Alan, it depends on the recipe you use. For example, mashed potatoes are boiled, while making a potato salad the slices are steamed (to keep them from falling apart). Here are all of the hip potato recipes, just choose one and follow the steps.
      https://www.hippressurecooking.com/category/ingredient/vegetables/potato/
      Welcome!

      Ciao,

      L

    2. I don’t eat many but pressure cooked a pot full of small potatoes yesterday for a large group. I use 1 cup of water and the trivet and used 14 min. It probably makes no difference whether the rack is used.

  13. Very glad to hear that reheating doesn’t reverse the effect!

  14. I bought a Walmart glucose meter to check out the theory of resistant starch in pressure cooked and refigerated potatoes. I cooked some medium gold potatos in my Instant Pot for 13 min. and refrigerated them for several days. This morning, I reheated 3 small to medium potatoes for 123 sec. in the microwave. I checked my blood glucose before and at 30 min after starting to eat. My blood glucose went from 105 mg/dl to 175 mg/dl.

    IMHO the resistant starch theory failed this n=1 experiment. I may try the experiment again and eat the potates cold.
    I have tried to eat LCHF (low carb high fat) for 3 years and won’t be buying any potatoes real soon.

    1. This is an interesting experiment. But, to make a conclusion you would also need to test your sugar levels after eating a warm freshly-cooked potato and then compare. I bet Greg, a retired science teacher, would have more suggestions on how to make this experiment more solid. ; )

      Ciao,

      L

    2. The article indicates that the cookling/cooling/reheating method forms resistant starch and that the absorbable starch is reduced by this percentage of resistant starch, not that all absorbable starch is eliminated. I would totally expect you to still have a glycemic response to the remaining normal starch. Your experiment should be to see what your numbers are eating normally cooked potatoes and then compare the number to the resistant starch potatoes. You would need to either consume the exact same things each meal or only eat potatoes each time in order to maintain control in your experiment (i.e. same amount of butter, same drink, etc.).

  15. Laura,

    I am a retired MD and have studied nutrition for the last 3+ years. The key to health and longivity is to minimize blood insulin levels by minimizing carbohydrate ingestion and replacing with good fats.
    The kidney can resorb glucose up to 180-200 mg./dl. Any higher and glucose is spilled into the urine. The pancreas will try to keep up by putting by increasing insulin secretion. Insulin is the fat storage hormone and chronic demand for more and more insulin is the cause of many dieaseses. In fact, it is the #1 health problem in the world. Cholesterol is not the problem. Excessive carbs are the problem.

  16. Aurora,
    I intended to continue self experimentation as you have outlined had my glucose been in the130-150 mg/dl at 30 min.however 175 is close to the renal threshold and is too high for me and my belief system. I enjoyed the potatoes too. My hemoglobin A1c was normal earlier this year @ 5.4% (I had hoped it to be < 5.0%). That is a test for your blood sugar level over 3 months. You don't catch obesity and diabetes type 2 like the flu. You earn them by eating too much sugar and carbohydrates too often. That is my understanding and I have studied the subject for 3 years.
    Insulin is the fat storage hormone and you can't burn fat with an elevated insulin level.

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