If gravy turns mashed potatoes pink, it is likely due to a chemical reaction between the ingredients used in the gravy and the potatoes. There are a few possible explanations for this color change:
pH reaction: Potatoes are slightly acidic, and certain ingredients in the gravy, such as red or brown food coloring or acidic substances, can react with the potatoes' natural acids. This reaction can cause a color change, resulting in pinkish tones.
Iron reaction: Some gravies contain iron-rich ingredients, such as beef or red meat extracts. When these ingredients interact with compounds in the potatoes, such as phenols or tannins, it can lead to a chemical reaction called "oxidation." This oxidation reaction can produce a pinkish color.
Chemical additives: Some processed gravies contain artificial additives or colorants that can react with the potatoes, causing a color change. These additives may have different chemical properties that can alter the appearance of the food.
It's important to note that the specific ingredients and cooking methods used in both the gravy and mashed potatoes can influence the color change. Different combinations of ingredients can yield different results. However, in most cases, the pinkish color does not affect the taste or safety of the food.
If you want to avoid the pink color, you can try different gravy recipes or adjust the ingredients to prevent the chemical reaction with the potatoes. Alternatively, you can serve the gravy separately from the mashed potatoes to maintain their natural color.