Sodium citrate is the sodium salts of citric acid. While citric acid readily found in citric fruits, citric acid is produced on a production scale via fermentation of various sugars.
Because corn is a readily available source of carbohydrates in the US, citric acid is fermented from corn related sugars/carbohydrates using Aspergillus niger. This makes citric acid and vulnerable to natural disasters and fertilizer fluctuations. Once citric acid is produced, the material is reacted with sodium hydroxide to form the sodium citrate salt.
Up Stream Materials/Building Blocks:
Carbohydrate (Corn, Molasses, Sucrose, Glucose, Fructose)
Down Stream Materials Consuming Sodium Citrate:
food additive, usually for flavor or as a preservative