Can you eat moldy potatoes?
The contents of this article are fact-based except otherwise stated within the article.
Author bio
Dr Anny March PhD is a food Engineer with expertise in Food Technology, Natural Polymers, Edible Films, Enzymes, and Nanotechnology.
Dr Anny Manrich’s Highlights:
- Research and Technology at the Brazilian Agricultural Research Corporation
In this brief guide, we will answer the question, “Can you eat moldy potatoes?”. We will also elaborate on some common molds that grow on potatoes, and different ways to minimize their growth along with the safe handling of potatoes with mold on it.
Can you eat moldy potatoes?
No, you can not eat moldy potatoes. Many molds provoke allergic responses and respiratory issues. And some molds, in the appropriate conditions, secrete mycotoxins, which are toxic substances that can make you ill.
It should be kept in mind that you only see part of the mold on the surface of food, for instance, gray fur on bologna that is kept outside, or small velvety spheres on fruits. It may seem less to you, but in reality, it could have penetrated the entire food deeply.
When a food exhibits substantial mold growth, the mold threads have undoubtedly penetrated it intensely. In deadly molds, toxic substances are often present in and throughout these threads. In some situations, poisons may have dispersed completely in the food.
Molds produce a number of potentially irritating substances that can be divided into volatile organic compounds and particulates (eg, spores, hyphae fragments, and their components). The threshold level of irritant response depends on the intrinsic properties of the specific material involved, the level plus length of exposure, and the innate sensitivity of the exposed tissues (eg, the skin versus nasal mucosa). Volatile organic compounds made by molds are responsible for their musty odor and include a wide range of alcohols, ketones, aldehydes, esters, carboxylic acids, lactones, terpenes, sulfur and nitrogen compounds, and aliphatic and aromatic hydrocarbons. Mold particles (spores, hyphal fragments, and their structural components) are not volatile. However, these structural mold compounds (particulates) are able to cause inflammation through deposition on mucus membranes (1).
So, even if you see slight mold growth on potatoes, discard them right away.
The common mold that grows on potatoes
Sclerotinia sclerotiorum is the common white mold that grows on potatoes. It produces white and fluffy mycelium and hard, black, unevenly shaped sclerotia. The sclerotia differ in size, ranging from quite small to over one-half inch in diameter. The sclerotia is the resting stage.
Sclerotinia sclerotiorum is typified by the lack of conidia and the generation of sclerotia and tan-colored, cup- or funnel-shaped apothecia generally 2 – 10 mm in diameter. Sclerotia form from the agglomeration of hyphae in colonized plant tissues. The first symptoms on potatoes appear as water soaked spots usually at stem and branch axles or on branches or stems in contact with the soil. A white cottony growth of fungus mycelium develops on the lesion, and the infected tissue becomes soft and watery. Lesions often expand in size rapidly following establishment and may girdle the stem which causes the foliage to wilt. Lesions become dry and will turn beige, tan or bleached white in color and papery in appearance (2).
How do you know when potatoes are moldy?
Raw potatoes should feel firm when touched with tight skin that should not have large blisters, black spots, or other flaws. If a potato has become soft to touch, you should discard it. Although it is normal for potatoes to have an earthlike or nutlike fragrance, a dusty or moldy fragrance is an indication of spoilage.
It is fair to say that if your potatoes grow any quantity of mold, they are no longer safe to consume. Also, you can not simply remove the mold, since the little microscopic spores could already be spreading somewhere else in the potato. As long as the potatoes are still firm enough, they are healthy to consume.
Somo common potato molds and their characteristics are listed (3):
Common Scab (Streptomyces spp.)
Common scab produces tan to dark brown, circular or irregular lesions which are rough in texture. Scab may be superficial (russet scab), slightly raised (erumpent scab), or sunken (pitted scab).
Early blight (Alternaria solani)
Tuber lesions are dark, sunken, and circular, often bordered by purple to gray raised tissue. The underlying flesh is dry, leathery, and brown. Lesions can increase in size during storage and tubers become shriveled.
Fusarium Dry Rot (Fusarium spp.)
Fusarium dry rot causes internal light to dark brown or black dry rot of the potato tuber. The rot may develop at an injury site such as a bruise or cut. The pathogen penetrates the tuber, often rotting out the center. Extensive rotting causes the tissue to shrink and collapse, usually leaving a dark sunken area on the outside of the tuber and internal cavities.
Black Dot (Colletotrichum coccodes)
On potato foliage, symptoms of black dot are nearly indistinguishable from those of early blight. On tubers, it produces tiny black sclerotia (fungal resting structures). Symptoms on tubers can be easily mistaken for silver scurf.
Silver Scurf (Helminthosporium solani)
Silver scurf affects only tuber periderm (skin). Lesions are initiated at the stolon end as small pale brown spots which may be difficult to detect at harvest but will continue to develop in storage. In storage, lesions may darken and the skin may slough off and many small circular lesions may coalesce to form large affected areas.
Ways to properly store potatoes
Below are some ways to help your potatoes last longer (4).
- Keep in mind, fresh potatoes will last longer. If you want to store some potatoes at home then it is best to opt for the freshest ones.
- Keep the potatoes in a cool, shady and dry spot in the pantry.
- Prevent direct contact with sunlight. Solanine production speeds up when potatoes come in contact with sunlight, which causes them to become even more poisonous gradually.
- Save the potatoes in an open basket that will enable the air to flow properly. Don’t keep them in plastic. Plastic will not let the air pass and will reduce the shelf life of potatoes. Instead try a basket, paper bag, net bag, or cardboard carton.
- Storing potatoes in a fridge is not recommended. Though cooling the potatoes will give them a more prolonged shelf life, the lower temperature will make the starch on the potatoes change into sugar. It not only gives the potatoes a sweeter taste but also makes them darker earlier. In other words, cold storage is commonly used to control sprouting, yet temperature management depends on the intended market: tubers for the fresh market can be stored at temperatures below 7°C while tubers destined for the processing market need higher temperature (8–13°C) to preserve frying quality (4).
- Observe the small eyes that grow on potatoes even after they are harvested. These eyes will grow into much bigger and larger sprouts with time. Get rid of those sprouts before they spoil the potatoes.
- Observe them frequently and remove those already in a bad state so they will not spoil the healthy ones.
- Applying essential oils (such as mint oil) on the surface of the potato tubers can delay sprouting and increase shelf life (4).
Correctly stored potatoes can stay fresh for 1-2 weeks, those kept in the fridge can remain fresh for 3 to 4 weeks while frozen potatoes can remain safe for 12 months.
Ways to minimize mold growth
Cleanliness is the primary step in regulating mold growth. Mold spores from contaminated mushrooms or other food products can accumulate in the fridge, dishcloths, and other cleaning tools. Follow the steps below to minimize mold growth:
- Clean the inside of the fridge after a few months with one tbsp of baking soda mixed in one-quarter of water.
- Clean with water and dry.
- Scrape any visible mold on rubber casings using three tsp of bleach in one-quarter of water.
- Keep dishcloths, napkins, sponges, and dusters clean and fresh. A musty smell indicates they are growing mold around. Discard items you can not clean or wash.
- Maintain the humidity level in the house under 40 per cent.
Other FAQs about Potatoes that you may be interested in.
Can sweet potatoes be peeled ahead of time?
Can cut potatoes be refrigerated?
How many grams of mashed potatoes do you need per person?
Conclusion
In this brief guide, we have provided an answer to the question, “Can you eat moldy potatoes?”. We have also elaborated on some common molds that grow on potatoes, and different ways to minimize their growth along with the safe handling of potatoes with mold on it.
References
- Bush, Robert K., et al. The medical effects of mold exposure. J Allergy Clin Immunol, 2006, 117, 326-333.
- Johnson, Dennis A., and Zahi K. Atallah. Disease cycle, development and management of Sclerotinia stem rot of potato. Am J Plant Sci, 2014, 5, 3717.
- Scheufele, S.B. Potato, Identifying Diseases. 2016. Center for Agriculture, Food and the Environment. UMass Vegetable Program
- Alamar, M. Carmen, et al. Assuring potato tuber quality during storage: A future perspective. Front plant sci, 2017, 8, 2034.
