I have heard rumors that Bob’s Red Mill’s customer service is telling people that their potato starch does not contain resistant starch (RS). In October, 2015, this comment appeared on the Bob’s Red Mill website:
Question: Is Tapioca Flour a Starch and would it be considered resistant starch?
Answer: Yes, tapioca flour is a starch, but it is not considered a resistant starch. Our potato starch, however, is considered resistant.
I have three thoughts:
- Bob’s does not want to be in the RS/health supplement business, so they are intentionally spreading a falsehood,
- Bob’s customer service people do not know that their product is high in RS, and give the wrong information, or
- Someone is spreading “fake news” so people use a more expensive (or different) product. Are these “emails” even real?
When discussing potato starch as a source of type 2 resistant starch (RS2), it must be uncooked. Once heated above 150 degrees, the starch granules swell and burst, becoming “readily digested starch.” Please read my (lengthy) review on resistant starch if you are new to the idea.
I am 100% convinced that Bob’s Red Mill Unmodified Potato Starch, and all other products labeled “unmodified potato starch” are good sources of RS. Bob’s Red Mill does not make the starch, they buy it from distributors. All potato starch is made in a similar fashion, easily Googled, and it results in a product that contains uncooked potato starch granules.
Depending on test methods used, the percentage of RS in a sample of potato starch is 50-75%. In fact, a sachet of potato starch is provided with the test kit for testing RS content in order to calibrate the process. There is no other native starch with a higher RS content than potato starch, so it makes a good control for the “span” of the test method, known as AOAC2002.02.
For $145, anyone can get some starch tested at Medallion labs, and several other labs that test this sort of thing. I’m surprised Bob’s Red Mill does not regularly test and label, but then they would be selling a supplement and not a cooking ingredient.While I have never sent a sample to be tested, I know some that have…results: Bob’s Red Mill Unmodified Potato Starch contains ~65% RS2.
If anyone needs further convincing, the process to measure RS in various starches was developed in this paper: Measurement of resistant starch by enzymatic digestion in starch and selected plant mater. They sent samples of various starches to 37 different test labs, Table 2 shows the range of results for potato starch (~45-70%, mean 63%). The potato starch used was a standard commercial brand (Avebe Potato Starch, NL).
Interestingly, Bob’s Red Mill told one person that their potato starch was of “Dutch origin,” one website listed it of “Malaysian origin.” My guess is that they buy it from the lowest bidder in huge bulk. On the open market, this product is traded as “native potato starch” meaning the granules are intact. Otherwise, it’s sold as “modified potato starch.”
Furthermore, UMich did a nice study on RS2 using Bob’s Red Mill Unmodified Potato Starch last summer, had it tested, and found it to be ~50%. I’m not sure which lab, or if they tried testing it themselves, but at any rate, Bob’s PS worked beautifully in their study.
Participants consumed their habitual diet throughout the study period. During the intervention phase, raw unmodified potato starch (Bob’s Red Mill, Milwaukie, OR) was gradually added to their diet (day 1—12 g, day 2—24 g, day 3—48 g; Fig. 1). This potato starch contains approximately 50 % resistant starch (type 2) by weight…Our data show that dietary supplementation with RS type 2 as unmodified potato starch increases fecal butyrate concentration, but with remarkable inter-individual variation.
Without equivocation, I can give a personal guarantee that the following easily purchased potato starches are good sources of RS2:
- Bob’s Red Mill Unmodified Potato Starch
- Anthony’s Organic Potato Starch
- Authentic Foods Potato Starch
- Barry Farm Potato Starch
- Others with the ingredient “potato starch”
However, buying potato starch from any source and using it as a prebiotic RS2 supplement is taking a chance. Until we can buy potato starch, or another resistant starch product that is specifically labeled with it’s RS content, there is always a chance that what you are using is not what you expect.
Therefore, if anyone is worried that Bob or Anthony or any of the other producers are supplying potato starch that is not a high-quality resistant starch, I would suggest this guaranteed source of measured RS2:
- Honeyville Hi-Maize Corn Starch (5lbs) – Guaranteed to be approximately 54% RS2.
- National Starch Hi-Maize Corn Starch (50lbs) – Guaranteed to be approximately 54% RS2.
I have it on good authority that soon some manufacturers of starch-based prebiotics will soon be launching products labeled with source and content of RS. Stay tuned!