I have been researching on E227 (Calcium Bisulfite), and could find minimal information about how it acts as a preservative and how effective it is. I could only find that it preserves by converting itself to sulfurous acid in an acidic liquid, but could not find out how effective and how exactly it preserves. I would appreciate any help.
Sodium bisulfite is one of several sulfur-based chemicals commonly known as ‘sulfites’. Others include potassium bisulfite, potassium metabisulfite, sodium metabisulfite, sodium sulfite, or sulfur dioxide, and also your calcium bisulfite. They have fungicide properties and stop the natural browning process of produce. Dried apricots stay orange, and golden raisins stay yellow. Sulfites stop the browning and further ripening of fruit by blocking the natural enzyme, polyphenol oxidase. Sulfites are also added to some wines.
Sulfites destroy vitamin B1 (thiamin) and so the FDA does not allow sulfites on food containing vitamin B1 (thiamin). They estimate that 1 in 100 people are sulfite sensitive, so it is illegal to use sulfites on foods sold raw, except potatoes. They get an exception because there is no alternative to keeping french fries from looking brown.
The FDA lists sulfites as generally recognized as safe, but sulfites are linked to neurological, gastrointestinal, and respiratory problems. Trace amounts of sulfites have been known to cause hives, vomiting, wheezing, and anaphylaxis. I know from experience that too many dried apricots can cause intestinal cramping.
Modified, but essentially reporting from https://traditionalcookingschool.com/preserving/dehydrating-preserving/sulfites-and-food-preservation/