Some components in food may react with ferric pyrophosphate. The following are some common situations:
Acidic components: Ferric pyrophosphate may dissociate under acidic conditions, releasing iron ions. For example, acidic substances such as citric acid, malic acid, and phosphoric acid in food will lower the pH value of the solution, reducing the stability of ferric pyrophosphate. When the pH value is low, pyrophosphate ions combine with hydrogen ions to form substances such as phosphoric acid or pyrophosphoric acid, thus freeing the iron ions. This reaction may affect the color, flavor, and nutritional value of the food. The free iron ions may further undergo redox reactions with other components.
Reducing agents: The iron in ferric pyrophosphate is ferric iron (Fe³⁺), which has a certain degree of oxidizing property. Some reducing agents in food, such as ascorbic acid (vitamin C) and sulfites, can reduce ferric iron to ferrous iron (Fe²⁺). Taking ascorbic acid as an example, it can provide electrons, enabling ferric ions to gain electrons and be reduced to ferrous ions, while itself is oxidized. In some cases, this reaction can increase the bioavailability of iron, but it may also cause changes in the color of the food or affect the stability of other components.
Proteins: Amino acid residues in protein molecules contain various functional groups, such as amino groups, carboxyl groups, and sulfhydryl groups, which may interact with ferric pyrophosphate. On the one hand, proteins can bind to ferric pyrophosphate through electrostatic interactions, hydrogen bonds, etc., affecting its dispersibility and stability in the food system. On the other hand, iron ions may undergo complexation reactions with certain amino acid residues in the protein, altering the structure and properties of the protein, and thus affecting the texture, taste, and other quality characteristics of the food.
Phosphates: Pyrophosphate ions in ferric pyrophosphate may undergo polymerization or depolymerization reactions with phosphates from other sources in the food. For example, orthophosphate can react with pyrophosphate ions under certain conditions to form polyphosphates with different degrees of polymerization. This reaction will change the existing forms and distribution of phosphates in the food, and further affect the processing characteristics and quality of the food, such as having an impact on the pH value, ionic strength, emulsifying properties, etc. of the food.
