Potato Starch

A couple of years ago I stumbled into what has been coined the 'hack of the decade.' I made the discovery that plain old potato starch, as commonly seen in supermarket baking aisles, is a second-to-none prebiotic, fermentable fiber. People all over the world are now using potato starch to improve their gut health.

I don't claim to be the potato starch "guru," and I don't want to be. It's up to you to decide how to use potato starch. If you are allergic to nightshades in general, don't despair...there are alternatives. This page is simply the intricacies of what I went through to ascertain the effectiveness of potato starch as a dietary supplement.

This page is filled with ideas that have been common knowledge among scientists for nearly 30 years, but have escaped the medical community and the general public until now. Resistant starch is recognized by dieticians, doctors, and much of the general public as a “thing,” but they don’t know what to do with it. People are more familiar with the term “fiber,” but even that term has fallen out of favor as it has become more of a marketing gimmick than a health intervention.

Potato starch is a solution to many of our modern health woes—our electric, fast-paced lifestyle with its reliance on antibiotics and excessive sterilisation has made us dependent on medications and and makes us age faster than we should. Obesity, diabetes, and heart disease are killing us and placing a huge burden on our health care system and personal finances. So many of our problems are brought on by diet alone and no one seems to realize, or care. Potato starch can be part of the solution. Potato starch is a safe, concentrated form of resistant starch—easily sourced, cheap, and effective.

This is the article that started it all for me:

Cooked, cooled potatoes contain healthy starch   

By Megan Murphy 

July 2, 2007 

There must be a million versions of potato salad. Some are extra-rich and creamy with mayonnaise or even sour cream, and some very low in fat with more of a vinegar or mustard base. Whichever way you prefer it, you probably haven’t ever thought of it as health food. 

Well, it’s time to think again. 

We so often count potatoes as low on the list of nutrient-dense vegetables. But recent evidence has turned up some new information that may lead us to think again about this meal staple. 

An animal study done in Spain showed that pigs fed larger quantities of raw potato starch had healthier intestines than pigs fed their regular diet. The potato starch-eating pigs also had lower levels of certain white blood cells in their blood. 

Fewer white blood cells showing up implies that there is less inflammation. Inflammation in the body seems to increase risks of chronic disease, including cardiovascular disease and cancer. 

Starch consumption in particular is thought to decrease risk for colon cancer. The lower levels of inflammation from the potato starch might correspond to fewer problems with irritable bowel syndrome. 

The key ingredient in the raw potato starch the pigs ate is something called resistant starch. This type of starch is not digested well in the small intestine, and continues on into the large intestine. The bacteria present in the large intestine feed upon this resistant starch. 

Certain bacteria are very helpful in maintaining intestinal health. Adequate bacteria in the large intestine, or colon, allows for more production of short-chain fatty acids. These particular fatty acids keep the cells that line the large intestine healthy, thus decreasing risk for colon cancer. 

There may be other roles for these short-chain fatty acids, too, involving weight loss and lowering blood cholesterol. 

Resistant starch is found in whole-grain cereals, seeds and nuts, as well as in some processed starchy foods like white rice and cornflakes. In certain foods, such as white rice and white potatoes, the resistant starch increases after cooking and cooling take place. 

Heating starch in the presence of water causes it to soften or gelatinize. Upon cooling, some of that starch turns into a more crystalline form that is resistant to digestion, therefore making it a type of resistant starch. 

Cold, cooked rice, like you would eat in sushi, and cooked, cooled potatoes, like you would eat in potato salad, fall into this category. 

Even though you may now see potato salad in a new light, that shouldn’t give you license to goop on all the fat you can. 

Potato salads loaded down with mayonnaise or oil might keep your intestines healthy, but all that fat can pack on the pounds. 

Today’s version is lighter on the fat, using vinegar and tasty Dijon mustard for flavor and moistness. Adding the asparagus makes this dish a significant source of folate, an important B vitamin. Plus, it adds color. 

This article is typical of articles on resistant starch (RS).  It extolls the virtues of RS, cites studies, and gives ways to incorporate RS into your diet.  Also typical is the massive gap between the amount of RS used in the studies cited and the amount and type of RS in the suggested dietary interventions.  EVERYONE missed the obvious low-hanging fruit.  Did YOU spot it? 

A quick web search for the Spanish pig study cited in the above article reveals what the study entailed:

OBJECTIVE: 

The potential effect of a long-term intake of resistant starch on colonic fermentation and on gut morphologic and immunologic indices of interest in bowel conditions in humans was studied in pigs. 

METHODS: 

Sixteen growing pigs were meal fed for 14 wk on a diet containing a large amount of raw potato starch (RPS; resistant starch) or corn starch (CS; digestible starch). Effects were assessed in the colon from the physicochemical properties of digesta and in the intestinal morphology, including lymphocytic infiltration, apoptosis, and proliferation activities. Hematologic and blood leukocyte cell subsets analysis were performed. 

RESULTS: 

After 97 d, the digestive content from RPS pigs was heavier than for CS pigs, producing a hypertrophy of tunica muscularis. The proportion of butyrate was two-fold higher in proximal colon digesta in RPS pigs. RPS-fed pigs had reduced apoptosis in the crypts, lamina propria and lymphoid nodules in the colon, and ileal Peyer's patches. Fermentation of RPS reduced indices associated with damage to epithelial cells, such as crypt cell proliferation and magnesium excretion, whereas mucin sulfuration was increased, which promotes epithelial protection. The numbers of intraepithelial T cells and of blood leukocytes, neutrophils, and lymphocytes, mainly T-helper lymphocytes, were reduced in RPS pigs. 

CONCLUSION: 

Long-term intake of RPS induces pronounced changes in the colonic environment, reduces damage to colonocytes, and improves mucosal integrity, reducing colonic and systemic immune reactivity, for which health benefits in inflammatory conditions are likely to be associated. 

This study is simply amazing.  When they fed pigs raw potato starch, their guts became super-”human”.  Pigs are often used in studies like this because their digestive systems are remarkably human-like, and they can be dissected and studied in ways humans can’t.   

Again, comparing the article to the study and again to the advice given at the end of the article shows a glaring discrepancy.  The pigs were fed raw potato starch and we are told to eat potato salad.  This may sound like reasonable advice, but it is not quite what it seems.   

Resistant starch is not all created equal.  A raw potato contains RS type 2 and cooked and cooled potatoes contain RS type 3. RS2 is also found in green bananas, plantains, and cereal grains. It seemed to be the RS type 2 that was making the big changes in the pig intestines, but there are numerous studies in which RS2 and/or RS3 are fed to humans and it seems about 20-40 grams per day are needed to make big changes in health.  

A couple of quick calculations show you’d need to eat about one raw potato or a couple of extremely green bananas a day to meet this goal if you wanted all RS2 from raw starch, of course you could try getting RS3 from cold potato salad, but it would take approximately 2-3 pounds to meet the need. 

Here’s the dilemma: green bananas are terrible to eat, and raw potatoes are nearly just as bad.  Is all this worth eating 3 pounds of potato salad every day?  You’d be fat as a pig if you did that!   It just isn’t that easy to get a lot of resistant starch in your diet.   

There is an elegant solution, however.  It’s so stupidly simple that everyone who has ever read a study on RS that used raw potato starch as the vehicle for RS missed…buy a bag of cheap potato starch at your local grocery store and eat it.  

SAFETY 

This “hack” for great gut health couldn’t be that easy.  Something HAS to be wrong with it...surely you can’t just buy a bag of cheap potato starch and expect it to work miracles in your broken, dyspeptic gut.  But, it does seem to be about as safe as any dietary intervention.  There are some people for whom this may not be a great idea, and some for whom this trick may not work—we’ll explain all that and give you some options.  But plain ol’ potato starch is a good start.  It’s not the be-all end-all for sure, but it has opened lots of eyes and caused quite a stir in certain circles.  Let’s take a look at all of the safety related concerns I’ve come up with so far in my grand little experiment: 

The FDA’s “Select Committee of ‘Generally Recognized as Safe’ Substances” issued a statement of the suitability of potato starch as a food item at the behest of none other than President Richard M. Nixon in 1969.   

According to this special presidential committee:

  

“There is no evidence in the available information on unmodified potato starch that demonstrates or suggests reasonable grounds to suspect a hazard to the public…”  

and 

“No adverse effects have been attributed to these starches as added food ingredients.”  

However, they did issue a couple of cautionary statements: 

“Consumption of excessive quantities, pounds per day, of raw starch has resulted in obesity and iron-deficiency anemia in human subjects.”  

and 

“It is suggested, however, that specifications for food grade unmodified starches be developed in order to distinguish them from the starches that are used in non-food applications.”   

The Food and Drug Administration likewise did not see potato starch as a harmful substance as long as it was labelled correctly.  They did not set a standard for potato starch because the US Pharmacopeia had already deemed potato starch safe and they deferred to them for safety concerns:

 “In the absence of a standard of identity, starch meeting the specification of the United States Pharmacopeia is acceptable for food use. 

For purposes of labeling in accordance with Section 403(i) of the Federal Food, Drug, and Cosmetic Act, and Section 4(a)(1) of the Fair Packaging and Labeling Act, the term "starch" is considered the common or usual name for starch made from corn; alternatively, the name "cornstarch" may be used. 

Starches from other sources should be designated by some non-misleading term that indicates the source of such starch, for example, "potato starch," "wheat starch," or "tapioca starch."”  

USP USE IN MEDICINE 

The US Pharmacopeia, whose mission is to “...improve global health through public standards and related programs that help ensure the quality, safety, and benefit of medicines and foods.” Has deemed potato starch safe for inclusion in medicine and they’ve developed specifications for pharmacy grade potato starch: 

To meet USP requirements, potato starch must conform to these standards: 

1  Description  Irregular, angular white masses or fine powder. Is odorless, and has a slight, characteristic taste.  2  Solubility  Insoluble in cold water and in alcohol.  3  Identification  (A) Microscopically examination  (B) By Chemical.  (C) By Chemical.  A) Under a microscope, using not less than 20x magnification and using a mixture of glycerin and water (1:1) as a mounting agent, it appears either as angular polyhedral granules of irregular sizes with diameters ranging from about 2 µm to about 23 µm, or as rounded or spheroidal granules of irregular sizes with diameters ranging from about 25µm to about 35 µm. The central hilum consists of distinct cavity or two- to five- rayed cleft, and there are no concentric striations. Between crossed nicol prisms, the starch granules show a distinct black cross intersecting at the hilum.  B) A thin, cloudy mucilage is formed.  C) An orange-red to dark blue color is produced, which disappears on heating.  4  Microbial contamination  a) Total viable aerobic count  b) Fungi count  c) Escherichia coli  Not more than 1000 cfu/g  Not more than 100 cfu/g  Must be absent  5  pH  Between 5.0 and 8.0.  6  Loss on drying  Not more than 20.0% w/w, at 130°for 90 minutes  7  Residue On Ignition  Not more than 0.6% w/w  8  Limit of iron  Not more than 10 ppm  9  Oxidizing substances  Not more than 20 ppm  10  Sulfur dioxide  Not more than 50 ppm

As a food-grade item, potato starch is usually accompanied by a “Technical Data Sheet” from the supplier which can be had for the asking.   

Most Technical Data Sheets look like this: 

Technical data sheet:

• Appearance white powder moisture 20% max
• Whiteness 95.0 min
• ph(30%suspension) 6.5-8.5
• Ash 0.25% max 
• Sulphur dioxide (SO2) 2ppm max
• Viscosity peak 1790b
• Granule size 150um (100 mesh sieve) 99.6% min

SULFUR DIOXIDE 

In all potato starch processing methods, an antioxidant is introduced at some point to keep the starch white.  Later, I will show you how to make potato starch at home...be forewarned, it will turn gray or pink as the proteins oxidize and stain the normally pure white starch granules.  Commercially available starch is expected to be bright white and this is accomplished by adding sulfur dioxide. 

Sulfur dioxide is used widely in our food supply, if you are sensitive to sulfur dioxide, you may want to either make your own potato starch or find a raw starch that does not contain sulfur dioxide.   

A review of dozens of technical data sheets from around the world showed that the sulfur dioxide contents ranged from less than 2ppm to 50ppm.  The Food and Drug Administration issued a statement in 1976 concerning sulfur dioxide in food items:   

“In view of the foregoing, the Select Committee concludes that: There is no evidence in the available information on … sulfur dioxide that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current and in the manner now practiced.” 

Further, they indicated that sulfur dioxide  is generally recognized as safe between 30-100 mg per kg of bodyweight!  They estimate average intake is .2 to 2mg/kg of bodyweight (for 220 pound person, that's nearly 200mg per day).   

The maximum SO2 content in potato starch, or 50ppm, would equate to 50 micrograms per gram of potato starch. 50 grams of potato starch contains about 2.5 milligrams of SO2, at it’s highest noted concentration, which is well-below the FDA’s limit of 200 milligrams per day for a 220 pound man.  

Still, if you have a known sensitivity to sulfur dioxide, you may want to avoid potato starch.  If you’ve ever had a reaction to foods that normally contain high levels of sulfur dioxide such as dried fruit, fruit juices, breakfast cereals, cookies, soft drinks, cereal bars, muesli bars, yogurt, ice cream, candy, frozen french fries, bread, margarine, or gluten-free flours, you may want to avoid potato starch. Sulfur Dioxide may be especially troublesome for people with asthma. 

SOLANINE 

A glycoalkaloid found naturally in potatoes, known as “Solanine,” can be troublesome.  Solanine is found in the leaves, sprouts, and green spots of potatoes and can be very toxic in large amounts—however it is not found in potato starch in measurable amounts. During the starch production process, the solanine is diluted and washed away with potato solids.  

Solanine may be found in effluents from potato starch factories and in the potato waste products generated during potato processing.  Thirty to eighty percent of the solanine in the potato tuber are found in the outer layers. Thus, peeling greatly reduces solanine levels. The first step in the potato starch production process is washing and peeling the potatoes. 

In commercially available potatoes, the solanine content is less than 20mg per kilogram..  At this level, it is considered non-toxic, however, the solanine can accumulate in green spots and eyes...it’s common-knowledge that these should be avoided. The National Institute of Environmental Health Sciences determined that the average consumption of solanine and other potato toxins was 12.75 mg glycoalkaloids per person per day, and that the lowest dose able to show toxic effects in humans is 5 times that at 1mg per kg of bodyweight, or about 50-70mg per day. 

Still, a standard warning needs to apply...if you are extremely sensitive to solanine you may wish to avoid potato starch. Signs of solanine toxicity are burning and tingling lips and throat immediately after consuming, and diarrhea, nausea, and gastrointestinal distress within a few hours.  Solanine does not accumulate readily in the body and is eliminated in approximately 12 hours by the health human. 

NIGHTSHADES 

Some people have “Nightshade Intolerances.”  Nightshade allergies stem from a malfunctioning immune system.  Your body sees the proteins in potatoes (or other nightshades) as a harmful substance and attempts to fight them off.  Your body immediately produces antibodies to destroy the nightshade proteins and these antibodies cause soft tissues throughout the body to become inflamed and watery.   

Nightshade intolerance mainly affects the lungs, skin, and nasal passages and is seen as asthma, runny nose, watery eyes, scratchy/sore throat, sneezing, and possibly a rash.  In severe cases, the lungs can swell leading to shortness of breath, chest pain and wheezing.      

Digestive symptoms are also common with any nightshade allergies. The intestinal tract can become inflamed from histamine, leading to vomiting, nausea, diarrhea, stomach cramping and abdominal pain.  

Nightshade intolerances are presumably caused by the glycoalkaloids contained in nightshade plants (potatoes, peppers, eggplants, etc…) and linked to rheumatoid arthritis. One proven connection to the cause of these conditions is poorly diversified gut flora. 

Presumably, since the proteins are all removed, there should be no problems.  But please err on the side of caution. If you’ve had allergic-type reactions to potatoes, peppers, eggplants, tomatoes, or pimentos, it’s best you use a different raw starch—more on this in a bit. 

MODIFIED POTATO STARCH 

Starch also has many non-food uses; it’s used in glue, laundry spray, automotive and drilling industries, and many other obscure processing methods.  Each one of these uses requires specially modified starch.  If you suspect the potato starch you want to use is “modified” in any way—don’t use it.  A quick call to the manufacturer may be needed to be sure, but generally, if it’s sold for food use, it’s “unmodified.”  Below is a list of terms used when modifying potato starch, if you see any of these terms—don’t use it: 

• dextrin (E1400),  roasted starch with hydrochloric acid 
• alkaline-modified starch (E1402) with sodium hydroxide or potassium hydroxide 
• bleached starch (E1403) with hydrogen peroxide 
• oxidized starch (E1404) with sodium hypochlorite, breaking down viscosity

• enzyme-treated starch (INS: 1405), maltodextrin, cyclodextrin 
• monostarch phosphate (E1410) with phosphorous acid or the salts sodium phosphate, potassium phosphate, or sodium triphosphate to reduce retrogradation 
• distarch phosphate (E1412) by esterification with for example sodium trimetaphosphate, crosslinked starch modifying the rheology, the texture 
• acetylated starch (E1420) esterification with acetic anhydride 
• hydroxypropylated starch (E1440), starch ether, with propylene oxide, increasing viscosity stability 
• hydroxyethyl starch, with ethylene oxide 
• Octenyl succinic anhydride (OSA) starch (E1450) used as emulsifier adding hydrophobicity 
• cationic starch, adding positive electrical charge to starch 
• carboxymethylated starch with monochloroacetic acid adding negative charge 

If you decide to use potato starch as a food item, it MUST be unmodified.  It MUST be sold as a food item, generally purchased in a food aisle or website selling it as a food-grade item. If you suspect it is modified in any way—DON’T USE IT. 

POTATO FLOUR 

Another product you may come across when looking for potato starch is potato flour—it’s not the same thing!  Potato flour is made from whole, cooked, and dried potatoes.  It may look similar, but it contains very little resistant starch.  Also beware of potato flakes—they are made from dehydrated, cooked potatoes, again—no RS. These are not dangerous in any way, they are just not a source of RS.  Use potato flour or flakes in recipes for taste and texture, but not for RS. 

Description of Potato Starch 

Potato starch is an amazing substance.  One could literally spend a lifetime studying it’s properties and uses.  It’s multifaceted and simply amazing.  Unimaginably complex yet incredibly simple.   

Potato starch, like all starch, is composed of two types of starch: 80% amylopectin and 20% amylose.  This starch is packed inside of granules that are spherical in shape that range from 10-100 micrometers across, averaging 36 micrometers—the largest of all starches.  Potatoes use these starch granules to survive between growing seasons, turning the starch into sugars for energy and also to prevent themselves from freezing.  These starch granules, known as amyloplasts are specialized cells designed to store sugar in the form of starch and look like this: 

from: http://waynesword.palomar.edu/vege1.htm 

Inside of each starch granules’ hard shell is a miniscule amount of water—20% by weight. When heated, this water swells and causes the starch granule to burst and turn into a sticky, gelatinous mess.  This is the ‘thickening’ action that makes potato starch so sought after by cooks for gravies and sauces.  As with everything about raw starch granules, this “little bit of water” is also not what it seems—it’s not there by accident, it’s an integral part of how starch works to provide energy for the plant.  This water is highly purified and remains unfrozen even at -30 degrees F.  It’s interspersed amongst the starch chains in a regular pattern and when looked at with an electron microscope, this pattern can be used to identify the type of starch it is.    

The amylose and amylopectin starches are works of art.  The amylose starch22 is a helical spiral unit made up of glucose units and looks like this: 

The amylopectin starch is made of the same basic building blocks, but is highly branched and  looks like this: 

         

When a human eats a raw potato, it gets broken down into tiny pieces through chewing and stomach actions.  In the small intestine, the proteins and about 20% of the starch are digested.  The remainder is termed “type 2 resistant starch,” and serves as food for your gut bugs.  This is haute cuisine to your intestinal microbes, something they evolved on for nearly 2 million years back when humans were more ape-like, but rarely see anymore--it is one of their favorite foods.   

When a potato is heated and eaten, enzymes in our stomach and small intestine attack the ends of the amylose and amylopectin chains.  Since the amylopectin starch is so highly branched, with lots of ends—it gets digested very fast.  The amylose, with it’s tight bonds and only two ends, gets digested more slowly.  This is food for us.  A really good food, too.  It packs a punch in carbohydrates, protein, and even a bit of fat.  It has a full complement of vitamins and minerals.  It’s good food...for us, but not our gut bugs.  In fact, they go hungry on a meal of freshly cooked potatoes. 

If the cooked potato is allowed to cool, the amylose and amylopectin starches undergo a process called retrogradation where the straight portions of each starch unit rejoin and form crystals.  As the temperature drops, the crystals become tighter and tighter and the water which was inside them is expelled.  This is why bread goes stale and stored potatoes turn dry.  The retrogradation process begins at about 40 degrees F and is fully complete when the temperature drops to 17 degrees F.  If you heat this potato back up, the retrograded starch actually gets stronger as more water is expelled.  In fact, you can heat and cool it several times and with each cycle, more retrograded starch forms.  When eaten, this provides a good meal for you AND your gut bugs.  Win-win.  This is the way humans cooked and ate for millions of years after we learned to cook food.  

ADHERENCE 

When I was a kid on the farm, my Mom used to make lots of homemade bread.  A family favorite was a version called “Salt-Rising” bread.  It differed from most breads in that it didn’t need yeast to rise.  The recipe called for putting a mixture of corn meal and potato slices in a bowl of warm water and keeping it warm for several days.  This “starter” made our house smell like death, but the bread it produced covered any lingering smells and delighted us kids to no end.  Here I am, 40 years later, finding out that Mom’s killer bread was the result of potato magic.   

Raw potato starch granules have an amazing property in that they attract bacteria—both good and bad—and put it where it needs to go.  This property, known as adherence, works through a mechanism known as “ligand mimicry.”  Animal and plant cells have receptors that allow for other cells to communicate with them, sometimes this inter-cell communication is the passing of hormones or transmitters that tell the cells to multiply or tell them to die.  Drugs often target these receptor cells, as do pathogens and viruses.  Anything that attaches to one of these receptors is known as a “ligand.”   

Potato starch is covered with receptors that do nothing except fool other cells into binding with them.   

This may seem inconsequential, but this exact same ligand mimicry is also seen in the fibers found in breast milk, known as Human Milk Oligosaccharides (HMOs).  In human breast milk, there are hundreds of compounds called HMOs that serve as food for the baby’s gut bugs.  Any pathogenic microbe, and most non-pathogens, that encounters these HMOs will attach themselves to the HMOs—and not the cells of the small intestine. This prevents small bowel infections, diarrhea, etc... and is one reason why newborns are so bulletproof.  Here's the point: Potato starch displays the same ligand mimicry as seen in HMOs.   

Potato starch can do two things for us with its little bag of tricks—it can take beneficial bacteria, for instance bifidobacteria, on a ride through the stomach and small intestine where bifidobacteria normally perish; and it can “mop up” stray pathogens and viruses that are located in the stomach and small intestine, taking them to the large intestine where they can be dealt with by our body’s defenses.  In the case of cholera, a mixture of water and raw starches are given to the victim and recovery is rapid as the cholera leaves the small intestine and is eliminated27. Unfortunately most common pathogens like Salmonella, Shigella, Klebsiella, or E. coli do not bind. Although ligand mimicry does not sway these populations, the butyrate and SCFA generated improves intestinal ecology as well as lowers proliferation  of these pathogenics. 

Picture of bacteria clinging to potato starch: 

from:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC92288/

  

Potato Starch Processing Procedures 

There are two places you can get potato starch—make it yourself or buy it in the store.  As you may have guessed, we’re not fans of overly processed foods such as wheat flour, vegetable oil, and high-fructose corn syrup.  Some people are concerned that potato starch is somehow “unnatural,” but that couldn’t be further from the truth.  Potato starch is a very natural product and found in large quantities in potatoes.  A raw potato is about 20% starch by weight, a regular-sized potato (~1/2pound), will yield about 40 grams of potato starch. 

DIY POTATO STARCH EXTRACTION 

If you have the time and a few basic kitchen tools, you can easily make your own potato starch: 

• Wash and peel 1 pound of firm Russet potatoes. 
• Using a hand grater, grate the potatoes into a large glass bowl. 
• With your bare hands, squeeze and knead the grated potatoes for several minutes. 
• Pour the potato slurry through a fine colander into another bowl. 
• Using two layers of cheesecloth, squeeze as much liquid from the drained potatoes as possible. 
• Place the squeezed-out potatoes in a bowl, add 2-3 cups of cold water, let sit 5 minutes. 
• Repeat the squeezing until you’ve extracted as much liquid as possible. 
• Put the squeezed-out shreds into a blender and cover with cold water. Pulse several times being careful not to chop too finely. 
• Strain the blended potato shreds in your colander and allow to drip for several minutes into your collection bowl.   
• Once again, squeeze the remaining potatoes using cheesecloth into your bowl of liquids. 
• Place the liquid in the refrigerator for 2-3 hours. 
• When the starch has mostly settled to the bottom, pour off as much liquid as you can, leaving the settled starch undisturbed. 
• Spread the wet starch onto a plastic or glass plate and allow to air dry overnight...a dehydrator on low heat would work even better. 
• When the starch is thoroughly dried, you will find that you have collected approximately 4-6TBS (48-60 grams) of potato starch from a pound of potato. 
  
  
  The process looks a bit like this... 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

COMMERCIAL POTATO STARCH EXTRACTION  

Seeing how easy it was to extract starch at home simply by grating and squeezing, I wondered if store-bought potato starch was made as simply.  I contacted a large manufacturer of potato starch and they gave me a look at how it’s done on a large scale:28 

• Freshly picked potatoes are placed in a rotating screen drum to remove any dirt, sand, or gravel. 
• The potatoes are blasted with very hot water and sent into a large vat of cold water where they are channeled and funneled towards a washing station. 
• At the washing station, the potatoes are rotated in another screen drum so that they agitate each other to remove any fungus, pesticides, or chemicals used in the growing process.  They are blasted repeatedly with high pressure water to ensure complete cleanliness and to remove the peels. 
• The cleaned, peeled potatoes are sent into a rasper where they are finely ground into a slurry composed of starch, potato juice, and potato pulp (protein and cell walls). 
• The potato slurry is sent to an extractor, a stainless steel, cone shaped, rotating drum, and blasted again with cold water to separate the starch from the other plant materials. 
• Sulfur dioxide is added at some point to prevent darkening of the starch, as previously discussed, this does not pose a health risk. 
• The crude “starch milk” that leaves the extractor gets sent to a refrigeration unit and  is filtered and rinsed numerous times through smaller and smaller screens until all that remains is pure starch. 
• The final step is drying the moist starch in a flash dryer with hot air and sifting the starch one last time before packaging. 

The only real difference between making your own potato starch and making it in an industrial setting is the use of sulfur dioxide.  An industry paper shows that is is used at a rate of about 1 pound per ton of potatoes, and carefully checked to ensure the amount found in the finished product is less than 50 parts per million, though more often it is less than 2ppm.  Sulfur dioxide is used widely as a preservative in the processing of dried fruits and vegetables, and also in wine making.  Sulfur dioxide is water soluble and is mostly gone from potato starch, however, if anyone is highly sensitive to sulfur dioxide, this may be a reason to avoid commercial potato starch and make your own instead.  

RS Amounts in Potato  

   

In many of the raw potato starch (RPS) studies, the researchers used 40 grams of resistant starch (RS) per day to achieve their goals of increased gut health.  Here is a breakdown on the RS content in RPS and also in potatoes cooked in various ways, and even raw.   

Let’s look at the nutrition label on a bag of potato starch: 

      

We see that 1TBS of potato starch weighs 12 grams, and contains 10 grams of carbohydrate.  The 20% disparity in weight vs. carbs makes sense since potato starch is 20% water.  We also know that if we eat RPS, we won’t be getting 10g of carbs—that is only effective for cooked potato starch.  Studies show that RPS is between 65-85% RS, so we’ll use 75%.  1TBS of RPS, therefore, should contain very close to 9 grams of RS (75% of 12 grams), and 4TBS will contain pretty close to 36g of RS.  

If you are a chronic calorie counter, it is safe for you to figure that when eating RPS, you will not be getting the advertised 40 all-carbohydrate calories per tablespoonful.  You will however get approximately 20 calories from fat.  This seeming contradiction occurs because your gut bugs are the beneficiary of the eaten RPS, and they turn it into butyrate, a short-chain fatty acid (fat).   

Next, let’s look at a potato: 

 

Again, the nutrition data is always going to be for a cooked potato, but since we are going crazy here and throwing convention out the window, let’s see what we can infer from the label as to it’s RS content when eaten raw. 

The potato on the label weighs 148g, which would make it “three to the pound.”  This potato would be about the size of a tennis ball, for reference.  Inside of it’s 148 grams of spud-licious goodness is a 20% starch content, give or take a few percent.  If you had a machine that could wring out every last drop of starch, you’d find there were just under 30 grams of pure starch in this potato, or just under 3TBS.  We know that pure potato starch is 75% RS2 by weight, so we can easily calculate that this potato, eaten raw, would provide us with 22 grams of RS.   

If instead of eating it raw, we decide to cook it and eat it hot, we’d find the RS content of this potato to be somewhere around .25 grams...not much.  This measly amount is achieved because all of the “resistance” cooked out of the starch—it is now considered “readily digestible starch,”  good for you--nothing for your gut bugs.  Potato starch gelatinizes, that is, the starch granules swell and burst--destroying the RS2 value when the starch reaches about 140 degrees F.   

Taking it all a step further, let’s cool this guy down.  We’ll put him in our refrigerator overnight and chill him right down to about 35 degrees.  The next morning, we find that the readily digestible starch has retrograded into a bit of RS--it now has about 3.5 grams of RS3.  We’ll keep going and chop this potato into cubes and heat it up in a hot pan with a bit of oil to brown it nicely.  At this point, our poor, reheated potato will have about 4 grams of RS3.  Cool it down again, 4.5 grams of RS3.  Heat it back up—5 grams, cooled again—5.5 grams, reheated—6g.  Eventually it will stop, but what I wanted you to see was how the biggest boost in RS was at the very first cooling and reheating cycle.  After that, it lessens. 

To recap: 

1 medium potato, tennis ball sized, 150g or so, can be looked at like this in terms of resistant starch: 

• Raw -              22g 
• Cooked -        .25g 
• Cooled -         3.5g 
• Re-heated -       4g 
• Re-cooled -     4.5g 
• Re-re-heated -        5g 
• Re-re-cooled -      5.5g 
• Re-re-re-heated -    6g 

Resistant starch in foods is officially measured with a standardized test protocol known as AOAC 2002.02.  This test was adopted in 2002 by the Association of Agricultural Chemists to ensure accurate reporting of RS contents.  Test labs that measure RS using AOAC 2002.02 cannot measure any values higher than about 64% RS by weight, and all measures of potato starch via this protocol result in an RS value of 64%.  Potato starch contains the highest level of RS of any natural (or synthetic) starch.  

Potato Starch as an RS Supplement 

Potato starch is a good way to boost resistant starch consumption to a level close to what was being used in human studies to good effect, as long as the whole spectrum of fiber is included (insoluble, inulin, oligosaccharides, etc)..  It is not difficult, with preparation that mimics cultural habits (cooling-reheating cycles), to get much more than 10-20g of RS per day through regular starchy foods food. Please see Chapters 10 and 16 for more detailed discussions about the differences and contrasting benefits of RS3 (cooked) and RS2 (raw).  

Below are some noteworthy scientific studies using raw, unmodified potato starch in varying amounts: 

  

1. Langworthy et al. described bloating and discomfort with 180g of raw potato starch and none with 60g.  It was also noted that when human subjects were fed over 40g of potato starch, a portion was found in feces, indicating that microbiome may only be able to process up to 40g of potato starch in a single feeding.   

  

2. 17-30g/day of raw potato starch in 15 day human trials increased SCFA. 

3. Three separate studies show that the prebiotic effects of raw potato starch are as, or more, effective than RS from other sources.  Raw potato starch is a preferred substrate by bifidobacteria over starches from pea and wheat.  That when compared with wheat or barley starches, potato starch induced greater amounts of satiety and postprandial glucose control and was on par with experiments measuring lipid metabolism, glucose control, and insulin response.  When compared with maize, wheat, and pea starch raw potato starch provided more butyrate than other starches studied.

4. Raw potato starch increased short chain fatty acid production and enhanced the proportion of butyrate.  Raw potato starch increased fecal weight and shortened transit time slightly. 

5. 50g of raw potato starch created less hydrogen than 10g of lactulose indicting it was being fermented in the large intestine by a different population of microbes that digest sugars.  

, 

6. Raw potato starch was compared to FOS.  It was found that raw potato starch is fermented mostly in the caecum and proximal colon, where FOS was fermented distally.  However, with the raw potato starch, more lactate was produced distally.  This study shows why raw potato starch on it’s own may not be as beneficial as raw potato starch combined with other fiber sources.  

7. Raw potato starch significantly increased absorption of calcium and magnesium without altering plasma levels.  When inulin was added, the effect was even better. 

8. Adding 50g of raw potato starch to a human diet reduced postprandial glycemia and insulinemia. 

9. Raw potato starch reduced the large intestine damaging effects of a high protein diet. 

10.  Raw potato starch stimulated the growth of bifidobacteria and lactobacteria as well as short chain fatty acids which were found to be useful for the suppression of pathogenic organisms in the colon. 

Clean-break Technology ®  

Of almost laughable note is the near universal acclaim of potato starch to regulate bowel movements.  Anecdotal reports of diarrhea and constipation clearing up rapidly after supplementing with a TBS or two of raw potato starch are commonplace, but the most sought-after effect has been termed the “Clean Break,”  Without going into gory detail, we believe that the built-in Clean-break Technology ® of potato starch may just put the manufacturers of toilet paper in the poor-house.  One could literally return to the day of using a corn cob to “finish up” and skid marks in tighty-whiteys may be a relic of the pre-RS years.   

  

ALTERNATIVES 

If you cannot tolerate potato starch, there are viable alternatives. It may also be a good idea to “change things up” every now and then just to keep your gut bugs guessing.  It’s doubtful our ancestors ate the same things day-in and day-out so there’s no reason for us to, either. 

The cooked food portions of resistant starch are fairly easy—get your RS3 from cooked and cooled potatoes, rice, beans, and the other sources we’ve shown you.  For RS2, the raw starch granules, you’ll need to be a little pickier. 

Other sources of RS2 equivalent to potato starch can be found in green banana or plantain flour, high-amylose corn starch, or tapioca starch. A brief description of each follows: 

Bananas -  

All bananas, which include plantains and “dessert” bananas, start out green, hard to peel, and filled with raw starch granules that are resistant to digestion and an excellent source of RS2.  As bananas ripen, they turn yellow and the RS2 quickly converts to sugar.   

A very delicious flour is made around the world from green bananas, most often the plantain variety, and makes a suitable substitute for gluten containing flours in baked goods.  What’s even better, when eaten raw, banana flour is a potent source of RS2.  The RS content in banana flour is a bit less than in potato starch because the starch is not extracted, the entire banana is dried and ground.  Even so, the RS content is a respectable 50% by weight.   

In some ways, banana flour is even better for us than potato starch in that it contains all the nutrients, vitamins, and plant fibers found in the original fruit.  This distinction is very important and makes banana flour a very desirable source of RS2.   

Tapioca -  

Tapioca is made from the extracted starch of the cassava plant.  While the raw starch of the cassava has been noted to be very high, up to 80%, in fact, the isolated starches have come in with mixed results.  Some studies that measured the RS in tapioca starch found as little as 5% and as much as 50%.  We believe the differences are due to the species of cassava used and also possibly the processing methods.  Until more is known, tapioca starch should be used with caution as an RS source.  

Corn - 

Regular corn starch used in cooking contains very little RS, maybe 2-3% by weight.  There is another type of corn starch known as high-amylose starch which is made from specially bred corn containing up to 55% RS2.  In many of the studies done on RS health benefits, this corn starch is called “HAMS” for High Amylose Maize Starch. There is technically nothing wrong with using HAMS to supplement RS2 in your diet, but there are many unanswered questions such as the safety and genetically modified organism (GMO) status of this grain.  Not much is written on the processing method and it seems to be embroiled deep in the manufacturing of “heart healthy” fiber-rich baked goods and is therefore steeped in “industry secrets.” 

Other starches -  

There are several other starches that have great promise as RS2 sources; mung bean starch, buckwheat starch, and pea starch all show high levels of RS2, but no studies have been done to catalog the RS remaining in commercially available products.  Hopefully one day, these starches will come with a label showing the exact RS content, but until then use at your own discretion.   

CONCLUSION 

Hopefully you read this chapter as it was intended, a simple treatise on the beauty and simplicity of potato starch as a suitable supplement for resistant starch.  The science behind potato starch is simply fascinating and the scientific/medical experimentation which has been performed just adds to the mystique.  How, and even if, you use potato starch is completely up to you, but our sincere hope is that you don’t discard all the other advice we’ve given you and jump straight into high doses of potato starch in an attempt to turn around years of medical issues and poor lifestyle or dietary choices.  Potato starch may very well be the one item that tips things in your favor, or it may end up being something you don’t need, only you will be able to decide.   

If, one day, you begin to see row after row of miracle resistant starch supplements, please keep in mind that plain ol’ potato starch can be just as good. 

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