You can tell if butter is rancid as rancid butter will smell sharp, metallic or even smell like old paint.
You can simply smell the butter and if the butter has a sour, musty or even a cheesy odor to it, the butter is rancid and or spoiled and should be thrown out.
Also check the surface of the butter and if the outer edges of the butter are a darker yellow, brown, or have any spots of mold, like white, blue or green, the butter is spoiled and should be thrown out.
And if the butter passes the visual and smell tests, you can taste a tiny silver of the butter and rancid butter will have a sharp, bitter or unpleasantly sour flavor.
Homemade butter also goes rancid and spoils faster than store bought butter as homemade butter lacks the preservatives that store bought butter has.
Homemade butter lasts for 2 to 3 weeks in the refrigerator, and up to 9 months to 12 months in the freezer.
The actual shelf life of the homemade butter also depends heavily on how thoroughly you rinse out any residual buttermilk and whether you add any salt.
If you're making the homemade butter yourself, after churning the butter, press and rinse the homemade butter under cold water until the water runs completely clear.
Leaving any residual buttermilk trapped inside will cause the homemade butter to spoil and sour in under a week.
When freezing the homemade butter, wrap the homemade butter in parchment paper or beeswax tightly, then place the homemade butter in an airtight container or freezer bag to prevent any freezer burn and odor absorption.
Homemade butter is often safe for 1 to 2 days at room temperature but any longer than that it starts to spoil due to lack of preservatives.
Homemade butter can be frozen and will remain at it's freshest in the freezer for between 3 months to 6 months but can remain safe to eat for 9 to 12 months when in the freezer.
The homemade butter unlike commercial butter lacks commercial preservatives, so homemade butter can and is also highly prone to absorbing odors from the freezer and going rancid.
But homemade butter does often freeze well.
However before freezing your homemade butter, you should wrap the homemade butter tightly in some parchment paper.
Then after the homemade butter is tightly wrapped in parchment paper, place the homemade butter in a heavy duty airtight freezer bag.
Then before you use the homemade butter, remove the homemade butter the day or night before you use it and allow the homemade butter to slowly thaw out in the refrigerator.
The signs that your homemade butter are bad are if the homemade butter has a sour, cheesy or metallic or even old paint smell.
Or if you notice any visible mold, a dark yellow, brown, or even pink discoloration or a slimy texture ot the homemade butter it's a sign that the homemade butter is bad and should be thrown out.
Homemade butter contains more trapped buttermilk, moisture and lacks preservatives and so homemade butter spoiled faster than store bought butter does.
Spoiled butter including homemade spoiled butter and store bought spoiled butter can make you sick.
Although if the spoiled homemade butter or store bought butter has just simply gone rancid from oxygen exposure, it often just tastes terrible and causes mild digestive upset, although it can sometimes cause nausea.
But if the butter that is spoiled has mold, it can harbor toxins and cause real food poisoning.
Butter is 80% fat, making it highly resistant to bacteria, but also vulnerable to oxidation (turning rancid).
Rancid butter smells sour, stale, or like "sweaty feet".
It won't give you severe food poisoning, but it can cause an upset stomach.
If your butter has visible mold or dark spots, throw it out immediately.
Molds can release harmful mycotoxins that are dangerous, and you cannot make it safe by simply cutting the moldy part off.
To keep your butter fresh, store it properly.
Salted butter can last 1 to 3 months in the fridge or 1 to 2 weeks on the counter in a covered dish.
Unsalted butter spoils much faster and should be kept refrigerated or used within 1 to 2 days on the counter.