Proprionates (bakery preservative) as migraine trigger

I haven't found anything online about proprionates as a migraine trigger, yet a doctor told me about them 30 years ago.

They are commonly used as preservatives in baked goods, usually in the form of either calcium proprionate or sodium proprionate. A line of whole grain breads I always bought has been absorbed by another company and now includes proprionates in their dough, so has lost my business.

Most grocery store bakeries do NOT have proprionates in the goods they bake on site. Unfortunately, they carry baked goods with no apparent brand name and no labelling to identify the ingredients. Many of these items, which seem to be similar to the store-baked goods in appearance and packaging, DO contain proprionates. I have learned to ask the staff to look them up for me, or I tell them I won't buy.

This chemical is used not only in bread and rolls, but pizza dough, bagels, flatbreads, pitas, wraps, pie crust (even the frozen stuff!?) in readymade pies and empty shells to fill at home, packaged cakes & desserts, etc. I've never found an English muffin without it.