I have purchased a Hamilton Beach 5 qt slow cooker. Made Wild Rice Chicken Soup in it for 7 hrs on low and after 4 hours I checked it and tasted. Delicious. 3 hours later I shredded the chicken and shut it off. It smelled and tasted delicious. Left it on warm and when I opened the lid 2 hours later, the smell was so disgusting that I gagged. The smell was a cross between melted plastic and something rotting. My hubby thought I had gotten sick in the kitchen. The smell lifted somewhat to just smelling like plastic. We couldn't eat it though because it still smelled and tasted like melted plastic. I had no problem with it the first time I used it. I could find no burnt or melted plastic anywhere on the cooker. What would have caused this. Would any ingredients do this. Wild rice, balsamic rice and normal soup stuff. I am returning the cooker but don't want to have this problem with another one.Made
It sounds like the cooker malfunctioned. An electrical fault inside the unit may have caused a short that caused some component to burn. Various electrical parts can give off strong acrid odors when this occurs. It's possible that the nature of the fault was such that its circuit only came into play when you switched the unit to "warm".
However, assuming it's a typical slow cooker with a ceramic bowl and glass cover, I don't know how the taste would be transferred inside to your cooked food. Perhaps the odor was so strong and held in the air such that it affected your taste buds.
In any case, you are wise to return the unit. Whatever happened to yours is likely an unusual occurrence. Hopefully it won't happen again to its replacement.
What ElmerCat said is correct.
As for your question about a specific ingredient causing the problem -- no. This has nothing to do with the ingredients, and everything to do with the appliance itself.
Typically, electronics either fail after only a few uses as there was some sort of a manufacturing mistake, or they take some time to fail. They may also fail if abused for some reason (eg, dropped, heated abnormally, tried using it without warming up after it had been in freezing temperatures, etc.)
If you're lucky, they just fail to turn on, or work sluggishly. When you're not so lucky, they burn up internally and may catch fire. It sounds like you were somewhere in the middle, but more towards the bad side.
(and if there are capacitors involved, the smells can get quite interesting ... and not in a good way)
And I'd also recommend posting a review on Amazon, even if that's not where you got it from. Enough people post reviews on there that it might help people identify if there's a particular model that's known to fail fast or in spectacularly bad ways.
Unless the cost of that thing is significant to you, do not return it but take it to an electrician and have him examine the cause, or take it to an electronics savvy friend and take it apart with him. Find out how these things fail, and if there ever was a danger of that failure mode causing a fire. Base your next purchasing decision concerning that make and model on the results of that.
Should you throw it away, before or after examining it, cut the plug off so nobody finding it can mistake it for something that might be serviceable.