Usually, when you buy fresh potatoes they seem clean. At other times, you may notice a small amount of visible dirt on the surface of the potato. Potatoes grow as a root under the soil, so they certainly are not clean when harvested. This variability in cleanliness makes people wonder whether commercial potatoes are washed before they are sold to market. The answer is yes, potatoes are generally washed before being sold. However, they are not washed until perfectly clean and there is no requirement for them to be washed that well. Read on to learn more about how potatoes are washed and the U.S regulations pertaining to potato cleanliness.
While potatoes are washed before being shipped to market, not all potato producers use the same methods or wash to the same extent. The variety of potato will also dictate, to some extent, the degree of washing. Newly harvested potatoes in general can have fragile skins and aggressive washing can damage them. There is no one type of machine that is exclusively used to wash potatoes. Different growers are free to use different means and some may even construct their own apparatus. Both water sprays or water baths are used and there is typically some method used to filter out debris and pebbles. Brushes, rollers, rotating barrels, water bath agitation and any number of other devices are effective. The video below shows a potato washing line in action.
Again, washed does not mean perfectly clean. Potatoes sold as fresh potatoes in the United States are USDA No. 1 Grade potatoes. The USDA Shipping Point and Market Inspection Instruction clearly describes the guidelines for grading potatoes based on cleanliness (among other factors) Here are the guidelines stated in this manual:
Few lots that have not been properly washed or brushed will deserve the terms “clean” and “bright” but the fact that they have been washed or brushed does not necessarily mean they merit such a description. Inspectors must learn the relative degrees of cleanness in order to properly describe various lots and should frequently check their judgment with their supervisors.
At the request of the applicant it will be permissible to report the percentage of U.S. No. 1 quality waiving cleanness requirements on unwashed lots of potatoes. Extremely dirty potatoes may mask defects; therefore, if the potatoes fail to meet the minimum cleanness requirement of the grade, samples must be washed and reported as such under remarks. The percentage of U.S. No. 1 Quality will be reported under REMARKS, not under Grade, with the following statement – “At applicant’s request inspection based on contract specifications which waive cleanness requirements. Lot approximately 80% U.S. No. 1 Quality other than dirt (samples were washed).”
The U.S. Grades for potatoes have the following requirements for cleanness:
- U.S. No. 1: Fairly clean.
- U.S. Commercial & U.S. No. 2: Free from serious damage caused by dirt or other foreign matter.
Definitions:
§51.1552 Clean. “Clean” means that at least 90 percent of the potatoes in any lot are practically free from dirt or staining and practically no loose dirt or other foreign matter is present in the container.
§51.1553 Fairly clean. “Fairly clean” means that at least 90 percent of the potatoes in any lot are reasonably free from dirt or staining and not more than a slight amount of loose dirt or foreign matter is present in the container.
Adhering Dirt or Staining
Adhering dirt, staining from soft rot or other foreign matter must be considered in determining whether or not the potatoes meet the cleanness requirements of the specified grade.
Sorting Guide
For the U.S. No. 1 grade, if 90% of the potatoes are fairly clean, the remaining 10% can be slightly dirty. Individual potatoes which are more than slightly dirty (i.e. damage or serious damage by dirt) will be scored against the tolerance for grade defects and also included in the 10% allowed for slightly dirty. For example, if 3% of the potatoes were damaged by dirt, you could have 7% slightly dirty (total of 10%) and still meet the requirements for fairly clean. When determining the percentage of U.S. No. 1 quality, deduct only that amount which is damaged by dirt or which is in excess of the 10% that is allowed for potatoes that are slightly dirty or stained.
In U.S. Commercial and U.S. No. 2 grades any potato which is badly caked with dirt or badly stained is a grade defect and must be scored against the tolerance for defects. A badly caked potato is one having caked dirt on more than 1/2 of the surface or an equivalent amount of dirt in excessively thick chunks on a lesser area.
Potatoes are Not Always Thoroughly Washed
The cleanliness of the fresh potatoes you buy will vary. However, no matter how clean they look, it is important to understand that potatoes should never be considered clean enough to use without giving them a thorough washing yourself. As you can see from the USDA inspection guidelines above, these potatoes are generally washed but they are not required to be perfectly clean, only fairly clean. The washing is generally done to improve the appearance of the potatoes and eliminate most of the obvious dirt clinging to them. Cleaning a potato in a way that renders them 100% clean is difficult to do without damaging the skin of the potato, which would severely impact not only the appearance of the potato but its storage life and it’s vulnerability to fungus, and other damage. It’s also important that potatoes can be completely but quickly dried. A waterlogged potato will not store well and will develop almost certainly develop fungus.
Consumers in the U.S. expect potatoes to look fairly clean when they are purchased, and producers try to balance this consumer expectation with the effect of washing on storage life and other factors. It would not be in their best interest, or yours, for them to wash potatoes until they were perfectly clean and free of all soil or other debris. Other cultures see things differently and may feel that potatoes without some visible dirt are lower quality or less fresh. Potatoes come out of the ground and people from some cultures expect them to look as if they came out of the ground!
Ideally, potatoes would be stored with some of the soil still remaining on their surface. The soil can be protective and help defend the potato against light exposure, which produces the green tint of chlorophyll along with toxic solanine in the skin. And, as well, soil can protect against fungus. Those who grow their own potatoes and store them in cellars certainly have no need to thoroughly wash them before storage, although removing some of the loose debris and soil may be desirable.
Always Wash Potatoes Before Cooking Them
You should definitely wash potatoes thoroughly before baking them or cooking with them in general. Even after peeling potatoes, it is best to rinse off the potato. Soil can contain dangerous micro-organisms, including botulinum spores. If present on the surface of a potato, these spores may not be destroyed by typical cooking. The danger from botulism is especially present in baked potatoes wrapped in foil. You should never eat a baked potato that was wrapped in foil and then allowed to cool down inside the aluminum wrapping. This produces the perfect environment for the botulinum bacteria to thrive, both anaerobic and moist. If botulilin toxins are produced, reheating the potato may not destroy them. This danger from foil wrapped baked potatoes is much higher in the very young.
Do Not Wash Potatoes In Advance
In is a very bad idea to wash potatoes the potatoes you buy in advance before you store them for later use. The moisture will cause the potatoes to spoil faster and may cause them to develop mold. Store your potatoes in a cool, dark place in a paper bag or mesh cloth bag. Wash them only when you are ready to use them. And never store potatoes in the refrigerator.
