Question from P.E.: why do potatoes I buy from the store foam when I cut them? Why are they so slimy on the inside?

Answer from Coastalfields: because they contain toxic chemicals.

Potatoes sold at the grocery store are usually at least a year old, and sometimes even several years old! Potatoes are harvested only once per year, so to keep a steady supply available (and have enough in case of shortages from poor harvests) they are stored for a very long time.

A potato from the grocery store is not just a potato! To prevent them from growing sprouts during this time, they are treated with any number of potentially toxic chemicals. Even organic store bought potatoes must be treated - they would also sprout if left untreated for that long! Here is a list of the most common chemicals used, and some that are currently being developed for future use in organic and conventional potatoes:

• Chloropropham is the most commonly used. It is applied in the storage facility (after harvest). It works by inhibiting root growth and photosynthesis. Chronic exposure of laboratory animals has caused retarded growth, increased liver, kidney and spleen weights, and lesions of the spleen. This chemical degrades very slowly in all environments (soil, air, and in your potato).

• Maleic hydrazide is the second most commonly used. It is also used for sprout inhibition on onions. It is applied before harvest to live potato (or onion) plants. The leaves absorb it and put it into the tuber (the part we eat). According to the EPA, Maleic hydrazide "appears to be genotoxic (that is, they have the potential to affect DNA repair processes) at high doses in some mutagenicity tests;" at these doses it can also cause tumors. The government has established a maximum residue tolerance for this chemical on potatoes, and expect that most people only get about 30% of the maximum amount that is safe to eat (safe means it will not cause documentable adverse affects). However, those who are getting the highest rate are young children (ages 1-6), who get about 60% of the maximum safe amount: young children weigh less and eat (proportionately) more.

• Di-isopropylnaphthalene is applied as an aerosol in the storage facility. It may only be used once during the storage process. It is not particularly effective, and is often combined with chloropham. This product also has a maximum tolerance to prevent people from eating unsafe amounts; it is estimated that the population typically gets about 7% of the maximum, and young children (ages 1-6) get 23%

• 1,4-Dimethylnaphthalene is applied as an aerosol in the storage facility. It is naturally occurring in potato skins, but the product itself is synthetic and manufactured.

• Many universities and private manufacturers are working on developing new sprout inhibitors that would be allowed in organic production. These include mint oils (peppermint and spearmint) and clove oils, both of which would be applied as aerosols or in a wick system. The Agricultural Research Service of the USDA has also reported that certain aromatic compounds and jasmonates (extract from the jasmine flower) can be used to inhibit potato sprouting.

A better way to store potatoes is through dehydration. This uses no chemicals whatsoever. Canning potatoes is also a good way to preserve the harvest...but watch out if you're buying canned potatoes that they do not include any potentially toxic preservatives in the canning liquid.

Resources:

http://extoxnet.orst.edu/pips/choropro.htm info on chloropropham

http://www.agr.gov.sk.ca/docs/production/PotatoManual_SproutInhibitionInThe%20Field.pdf Info from Canada on chloropropham and maleic hydrazide

http://www.epa.gov/oppsrrd1/REDs/factsheets/0381fact.pdf Info on Chloropropham

http://www.umaine.edu/umext/potatoprogram/Pest%20Control%20Guide/Sprout-Inhibitors-section.pdf Info on synthetic options

http://www.kimberly.uidaho.edu/potatoes/alternat.htm Info on mint products

http://www.organicfacts.net/organic-vegetables/organic-potato/organic-control-of-potato-sprouting.html Review of organic options

http://www.ars.usda.gov/is/AR/archive/jul02/sci0702.htm Info on organic aromatic and jasmonate options

http://info.ag.uidaho.edu/pdf/CIS/CIS1120.pdf Info on Organic options

http://pmep.cce.cornell.edu/profiles/herb-growthreg/24-d-butylate/26-Diisopropylnaphthalene/diisopropylnap_let_804.html Info on Di-isopropylnaphthalene

http://www.ams.usda.gov/NOP/NationalList/TAPReviews/14Dimethylnaphthalene.pdf 1,4-Dimethylnaphthalene organic review