Fresh, raw suet is white and has a dry, slightly crumbly texture, but this may vary to a reasonable extent. While beef suet turns yellowish and develops a buttery texture as it ages, the edible fat shouldn’t be black or dark.
The main reason why your suet is turning black is microbial growth. Stale suet is rancid as it starts to decompose, which facilitates the growth of bacteria and fungi. Also, a suet cake or such food for birds may have contaminated ingredients that might turn black.
1. Stale or Rancid Suet Can Turn Black Due to Mold
Suet isn’t tallow, which is a rendered form of the same fat, and it has a much longer shelf life than suet.
However, the rendered suet used in bird feeds, whether cakes or bark butter, isn’t the same composition or quality as tallow made for people’s consumption.
So, here are some facts about the type of suet you probably feed your birds:
- Fresh, raw suet has a shelf life of only 5 days in a refrigerator.
- Fresh but frozen raw suet has a shelf life of 6 months in a freezer.
- Frozen suet stays good for ~1 month in the fridge after it’s thawed/opened.
Ideally, you should buy the freshest suet if you want to get some raw fat, which is likely to be the whitest form you can get.
But most people get slightly aged suet because that’s what is usually available.
However, if you’re lucky enough to live near a butcher, you can ask them to save the suet that they normally throw out when preparing an animal for sale.
Hence, the aged raw suet has a shorter life in the fridge or freezer, respectively.
Aged or old suet turns stale and rancid sooner. The moment the fat begins to decompose, it will harbor the growth of various microbes, including black mold.
So, your suet is likely to turn dark. The discoloration is typically black, but you may also find brownish and other fuzzy patches.
The growth of fungi or mold and bacteria is likely to be extensive if the ambient conditions are perfect for those microorganisms.
Your suet is likely to turn black sooner in the following circumstances:
- During the summer, heat and humidity turn suet rancid sooner than in winter. Suet’s melting point is 113°F to 122°F. But raw suet begins to melt at 70°F, which is sufficient for the growth of most bacteria and fungi.
- During the wet season or whenever there’s rain, water, or moisture exposure. Mold thrives in moist environments. Any direct contact with water or rain will alter the texture and composition of raw suet. So, rapid microbial growth may turn the suet black.
- When your suet is already aged or a bit old, its microbial infestation is likely to be aggravated. You may not know the specific condition of raw suet as you load it on a bird feeder. If it’s going bad, the fat is likely to start decomposing sooner.
Suet fares better in the colder months, which is why you should consider placing such feeders in the shade during summer.
You can also use a splash guard or some makeshift solution to protect the suet and feeder from rain and any bird bath you may have nearby.
2. Suet Cakes May Have Contaminated Ingredients
Many people don’t use fresh, raw suet to feed birds. You’re probably familiar with the following types of processed and packaged suet:
- Cakes
- Pellets
- Nuggets
- Plugs
- Bark butter
- Stackable
Some cakes or stackable suet are a no-melt variety, which don’t melt as quickly as raw suet.
But even the no-melt suet cakes or stackables won’t retain their composition or texture in high heat and humidity.
Besides, any such product may have contaminated ingredients.
Rendered and processed suet products for birds can have various ingredients, including the following:
- Corn
- Cornmeal
- Dried fruits
- Dried insects
- Peanut
- Peanut butter
- Other grains
- Sunflower seeds
- Thistle or nyjer seeds
Even if the suet itself isn’t stale or rancid, infested ingredients may make the feed vulnerable to microbial growth and outbreak.
Corn and cornmeal are thriving growth mediums for bacteria and mold, and so are peanuts.
Peanuts are known to be a haven for foodborne pathogens, including:
- E.coli
- Listeria
- Salmonella
- Mold spores
- Mold mycotoxins
Even peanut butter can compromise the quality of suet spreadables and stackables.
Salmonella can survive in peanut butter for ~6 months at a storage temperature of 41°F.
The survival rate is low in natural peanut butter, especially at storage temperatures ~70°F.
But Salmonella reproduces rapidly when the temperature spikes towards 77°F.
The effect of these temperature fluctuations is more severe for other bacteria and mold.
Most mold and bacteria thrive at 40°F to 140°F, aka the Danger Zone.
Thus, the various ingredients in suet feeds can become the ideal medium for black mold, other fungi, and several bacteria.
You can’t do much about contaminated ingredients or already aged suet except to buy these feeds from well-known retailers or manufacturers.
Even if you buy suet from a local butcher, you should ensure that it is fresh and handled in an impeccably clean and sanitized facility.
Otherwise, raw or processed suet may not stay fresh or pleasantly edible as long as you want.
The suet in your bird feeder is likely to turn black. Also, suet that’s already a bit rancid isn’t salvageable, whether you freeze or refrigerate it.
3. Feeders Infested With Microbes Turn Suet Black
A bird feeder infested with microbes, including mold, can turn suet black.
The fat’s quality or any of its ingredients, if you buy rendered suet in some form, won’t be the culprit. But this problem is in your control.
You should clean and disinfect your bird feeders before replenishing any stock.
Cleaning and disinfecting should apply to all feeders.
Even if you have an exclusive suet feeder that you don’t load with seeds or other foods, you should still clean and disinfect it before loading fresh bird feed.
Otherwise, your suet may turn black frighteningly sooner than you anticipate.