What are the brown spots on beans?

Beans are a common food ingredient used in many cuisines around the world. They provide protein, fiber, and other essential nutrients. However, sometimes when preparing dried beans, you may notice some have small dark or brown spots on the outer skin. These spots can be unsightly and cause concern about the safety or quality of the beans. But what causes these spots, and are they anything to worry about?

The brown spots that can appear on beans are actually quite natural and harmless. They are simply deposits of pigment that can occur as the beans dry. There are a few common explanations for bean spots:

Natural Pigmentation

Many bean varieties have natural pigmentation in their outer seed coat that shows up as speckles, streaks, or spots. Kidney beans, for example, often have reddish brown markings. As the beans dry, these pigments can become more concentrated in places, resulting in spots. This natural bean coloration is not a defect or sign of spoilage.

Water Droplets During Drying

Another reason brown spots may appear is from water droplets falling on the bean surface during the drying process. As moisture accumulates in one place, it can facilitate leaching of pigments and compounds to that area from the bean cotyledon inside. This creates a brown stain on the bean skin. But it does not affect the safety or nutrition of the bean.

Microscopic Damage

Sometimes microscopic cracks or imperfections in the bean seed coat lead to pigment congregating in that area as the bean dries down, again producing spots. But this is harmless and does not make the beans unsafe to eat.

Environmental Factors

Environmental conditions such as humidity, temperature, or sunlight during growth, harvest, and storage can also influence the appearance of beans. Exposure to moisture, heat, or certain gases during storage may create pigmentation changes and spotting. These factors can accelerate pigment alterations in beans, but do not necessarily render them unsafe.

Are the spots harmful or unsafe?

In most cases, the brown spots on beans are simply a cosmetic issue, not a sign of safety or quality problems. Here are a few key points showing the spots are harmless:

  • The spots are naturally occurring pigments and compounds inherent to beans. They are not contaminants or dirt.
  • The spots do not indicate mold growth or other microbial issues. Internal bean tissue is not affected.
  • There is no loss of nutritional value or flavor due to the spots.
  • The spots do not mean the beans are too old or spoiled. Beans keep for a long time without spoiling.
  • Cooking destroys any bacteria or enzymes, even if they were present due to damage allowing pigment leakage.

Research has confirmed that spotted beans are perfectly safe to eat. One study published in the journal Food Control examined beans with up to 25% of their surface area covered in brown spots. Chemical and microbiological analysis found no significant differences compared to beans without spots in terms of safety, shelf-life, nutritional content, or acceptability after cooking.

The Food and Drug Administration and other food safety organizations do not consider naturally occurring spots to be a defect or hazard in dried beans. The European Commission actually allows up to 25% of beans to show minor defects such as discoloration while still meeting quality standards.

So in summary, minor brown spots do not indicate beans have gone bad or pose any safety issues. Spotting is common and harmless, though some consumers still dislike the appearance. But the beans can be rinsed, sorted, or ground to eliminate spots with no need to discard batches due to small blemishes.

How to prevent spots on beans

If you want to minimize brown spots appearing on your dried beans, here are a few storage and preparation tips:

Avoid moisture during storage

Exposing beans to dampness or humidity can increase spotting. Store beans in an airtight container in a cool, dry place. Check for condensation or moisture inside containers.

Sort through beans

Picking through beans allows you to remove any with excessive spotting or imperfections. This is recommended for dishes where appearance is important.

Rinse before cooking

A quick rinse can help wash away some superficial spotting on the bean surface.

Grind beans into flour

Once dried beans are ground into flour, any minor spotting becomes invisible. Whole bean flours are very versatile for cooking and baking.

Consider the variety

Some bean types with thicker outer seed coats, like kidney beans, tend to show more obvious spotting. Lighter colored beans make spots more apparent. Choosing smooth-skinned varieties like navy or cannellini can reduce spotting.

Buy from reputable suppliers

Purchasing beans from companies with good quality control and storage practices can minimize damage and defects leading to spotting.

Cook thoroughly

Proper cooking destroys any enzymes or contamination, even if theoretical. Boiling beans for 10 minutes ensures safety.

While spots are harmless, these tips can help you achieve beans with the appearance you prefer. But keep in mind a few brown flecks are normal and should not cause concern about your bean quality.

Common questions about bean spots

Here are answers to some frequently asked questions about the harmless brown spots that can appear on dried beans:

Are spots a sign of insects or dirt in the beans?

No, the spots are naturally occurring pigments, not foreign contaminants or dirt. They are not caused by insects. Proper sorting and cleaning processes remove any dirt, debris, or damaged beans.

Do the spots mean the beans went bad?

The spots do not indicate spoilage or make the beans unsafe to eat. Beans are very shelf stable and can be stored up to a year without spoiling. Spots may become more noticeable as beans age but are not a sign they went bad.

Should I throw out spotted beans?

There is no need to discard beans with a few small spots. The FDA and food safety authorities say minor spotting is allowed and harmless. Removing flawed beans may reduce spots, but beans with some spotting can be rinsed or cooked as normal.

Can I eat spotted beans raw?

Raw beans must always be cooked before eating, even without spots. The tough cell walls of raw beans cannot be digested. Cooked beans are safe and nutritional.

How do I get rid of the brown spots?

Soaking, rinsing, or grinding beans can help remove surface spotting. Sorting to remove beans with extensive spotting is an option too. But small spots will not affect flavor and do not need to be removed.

Should Ibuy beans with spots at a discount?

Saving money on discounted beans with spots is fine since the spots do not indicate a problem. Just inspect closely for any damage, mold, or extensive defects unrelated to pigment spotting before purchasing.

Minor brown spotting on beans is harmless and unavoidable at times. With proper storage and preparation, beans with some natural spotting can be used and enjoyed with full confidence.


The small brown spots that can appear on dried beans are a naturally occurring, harmless phenomenon. They are caused by pigments and compounds in the bean seed coat becoming concentrated into spots during drying and storage. Factors like moisture, temperature, and bean variety can influence spotting, but the spots do not indicate spoilage or make the beans unsafe. Research confirms bean spots do not reduce nutritional quality, shelf-life, or flavor. Food safety organizations allow for some bean spotting as acceptable within standards. While the spots may not look appealing, beans with a few small blemishes can be rinsed, sorted or ground to minimize appearance. But overall, minor brown bean spots are natural, common, and harmless, so beans showing some spotting do not need to be discarded. With proper handling and cooking, spotted beans are just as healthy and delicious as unspotted ones.

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