U.S. FDA is Reviewing Petition to Broaden Soy Leghemoglobin Use

On March 14, 2025, the U.S. Food and Drug Administration (FDA) announced in the Federal Register that it has filed a Color Additive Petition (CAP 5C0336) submitted by Impossible Foods, Inc. The petition proposes to expand the safe use of soy leghemoglobin as a color additive to include plant-based meat, poultry, and fish analogue products (both ground and whole cut).

If approved, soy leghemoglobin could be used in a wider range of plant-based products, including meat, poultry, and fish analogues. This expansion would support innovation in alternative protein foods while ensuring safety through the FDA's comprehensive review process.

Background

The color additive soy leghemoglobin is a stabilized product of controlled fermentation of a non-pathogenic and non-toxicogenic strain of the yeast, Pichia pastoris, genetically engineered to express soy leghemoglobin protein. Soy leghemoglobin protein is the principal coloring component of the color additive and imparts a reddish-brown color.

Under 21 CFR 73.520, soy leghemoglobin must meet stringent specifications to ensure safety and quality. These include:

• Purity Requirements: The protein purity must be at least 65% by weight, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

• Heavy Metal Limits: The levels of lead, arsenic, mercury, and cadmium must not exceed 0.4 ppm, 0.05 ppm, 0.05 ppm, and 0.2 ppm, respectively.

The current regulations allow the safe use of soy leghemoglobin in ground beef analogue products, with the protein content not exceeding 0.8% by weight of the uncooked product.

Food Additives & Petitions

A petition is needed when proposing new uses for food or color additives. These additives are considered unsafe unless they comply with existing regulations or investigational use exemptions. The petition must include supporting data and information to request a new regulation.

The following is a simplified overview of the approval process for food and color additives. This process may involve repeating certain steps until the Agency reaches a consensus that the petitioned use of the additive poses a reasonable certainty of no harm.

1. Enterprises submits a petition

A good food and/or color additive petition shall includes:

a. The identity and composition of the additive

b. Proposed use

c. Use level

d. Data establishing the intended effect

e. Quantitative detection methods

f. Estimated exposure from the proposed use (in food, drugs, cosmetics, or devices, as appropriate)

g. Full reports of all safety studies

h. Proposed tolerances (if needed)

i. Environmental information

j. Fee (for color additive petitions only)

k. Ensure that consistent information is presented throughout all sections of the petition, including those pertaining to:

• chemistry,

• toxicology,

• environmental science, and

• any other pertinent studies (e.g., microbiology)

2. FDA receives a new petition

• FDA's Office of Food Additive Safety (OFAS) evaluates the petition for adequacy of filing (if adequate, a filing notice is published in the Federal Register)

• The need for review outside Center for Food Safety and Applied Nutrition (CFSAN) is determined

3. The Consumer Safety Officer distributes appropriate parts of the petition to experts for evaluation

4. Decisions

• A tentative safety conclusion is reached,

• Advisory committee input is received, if necessary,

• The final safety evaluation is made,

• The administrative record is compiled, and

• A Federal Register final rule is drafted

5. The final Agency review is completed

The final regulation is published in the Federal Register and later codified in the Code of Federal Regulations.