Obviously ingredient labels will not expressly tell you “mold”. With the exception of things like yeast, aspergillus oryzae or other such formal starter cultures that are intentionally used to produce certain foods.
The main things I look out for are anything fermented (sauerkraut, kimchi, fermented bean pastes, kombucha, chocolate) including vinegar. Speaking of vinegar, most commercial vinegar is fine in small amounts as they are pasteurized. Heat removes most of the problems for me. I avoid raw or unpasteurized vinegars found usually in the fancier, healthy, small batch brands. I avoid things like sauerkraut and fermented bean paste even when cooked, as these have large amounts of mold and seem to cause mild issues.
Things would be much more complicated if one does not tolerated small amounts of mold even when cooked. This would mean any tomato products, mushrooms, even berry preserves would be out, among others. Luckily I am okay with these.
Also, corn and peanut are notorious for mold contamination. The more processed they are, the more we cannot see their whole form, the more likely to be problematic. As for us, we didn’t detect any problem with fresh corn, even frozen or canned corn, where we can see the whole kernels. But there were some incidents that made us suspicious of corn flour or cornmeal products such as cereals or chips.
Since most of my problem foods are among the 8 most common allergens, many times a quick scan for the major allergens is enough to reject a food product. For example, any mention of milk, tree nuts, or shrimp, and it’s out. But if it mentions wheat (gluten) or soy, I look further.
If the soy is in the form of soy lecithin or soybean oil, I can have it. Protein content in lecithin and commercial oils are so low that most people with allergies will tolerate these.
If the only source of wheat and soy is soy sauce, I can usually have it. Gluten content in commercial soy sauce is under 20 ppm for most brands and I can tolerate small amounts.
Of course this all depends on one’s sensitivity level, but knowing these exceptions can open up quite a few more options.
If you have food allergies, should you worry about cooking oils (and fats) in your food?
In general, commercial peanut oil, soybean oil, sunflower oil, palm oil are unlikely to cause reactions as they are highly refined and their protein content is nonexistent. But there can always be exceptions. It all depends on your sensitivity level. If you are extremely sensitive to even minute amounts or if your reactions are severe it would be safe to err on the side of caution.
Oils labeled cold pressed, expeller pressed, or unrefined, are more problematic from an allergy viewpoint as they will contain small amounts of protein. These are more likely to be found in “natural”, “organic”, and higher-end foods as they are generally considered healthier due to less processing and thus less loss of nutrition.
Coconut, sesame, perilla oils are generally not refined.
And for milk allergies, ghee and clarified butter’s milk protein content is much lower than butter. Again depending on sensitivity level you may tolerate none, one, or possibly even both.
Allergenic protein structures change when processed. Some are more heat labile than others. It all depends on the protein structure.
Higher temperatures for longer times can decrease the allergenicity of the proteins, allowing it to be tolerated by some. Generally the greater the decrease in allergenicity as you heat, cook, and finally bake.
Fermenting is another way protein structures can change enough to make a difference in allergenicity, as they are partially digested into shorter chains (peptides).
Example: gluten content in regular commercial soy sauce. Many test under 20 ppm, low enough to be tolerated depending on one’s sensitivity.
Soy decreases allergenicity when fermented, which might be meaningful if you are allergic or intolerant to soy.
But less well known, some are allergic to fermented soy but okay with soy.
There is a study on late onset anaphylaxis with natto allergic. Unusual in that it is IgE mediated but triggered only when it reaches the intestines, taking a mean of 8 hours.
I am not okay with soy but my reaction is much worse with raw fermented soy. I suspect it is the difference between soy protein intolerance versus mold (aspergillus) allergy. If I didn’t have the latter I might have tolerated small amounts of fermented soy, such as that of a typical condiment serving size, which would have opened up some more flavor adventures, alas.