L-proline
L-proline suppliers and sourcing guide
L-proline is a non-essential amino acid with a ring structure, a major building block of collagen. Commercial L-proline is made by bacterial fermentation of sugars, then purified and crystallized. It is a white crystalline powder, very soluble in water and slightly hygroscopic, that brands buy for amino acid blends, collagen-style formulas and powders, and that is also used in cosmetics.
- Category
- Proteins and amino acids
- Also known as
- Proline · L-Pro · (S)-2-Pyrrolidinecarboxylic acid
- Facts checked
- November 2026
Forms and grades of L-proline
Suppliers sell different products under the same name. Specify the one you need.
Crystalline
Standard fine crystalline powder for capsules, tablets and dry blends.
Fermented (plant-sugar) grade
L-proline made by bacterial fermentation of corn, cassava or beet sugar; the source and any vegan statement appear on the supplier's spec.
USP grade
L-proline tested to the USP monograph, used where a compendial grade is required for supplements.
Food grade
L-proline tested to a Food Chemicals Codex or supplier food specification for use in foods and drink mixes.
What to check on the COA
Compare each result with your own specification when the lot arrives.
- Identity
- Infrared spectrum matched to a reference standard, plus specific optical rotation, which confirms the L-form of proline.
- Assay
- Purity on a dried basis by nonaqueous titration or HPLC, reported against the USP, FCC or supplier specification.
- Related substances
- Other amino acids, including hydroxyproline, by HPLC or TLC.
- Loss on drying and residue on ignition
- Moisture by loss on drying and inorganic residue as residue on ignition (sulfated ash), with chloride and sulfate where the specification lists them.
- Heavy metals and microbiology
- Lead, arsenic, cadmium and mercury by ICP-MS, plus total plate count, yeast and mold, E. coli and Salmonella.
Storage, lots and expiry
Storage and shelf life
Store L-proline in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. It absorbs moisture readily, so keep liners tied and use desiccant in part-used containers. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
Lots and expiry dates
Record assay and loss on drying for each lot, since moisture pickup can cause caking. Rotate stock FEFO.
Regulatory status
Facts from regulators and standards bodies, each linked to its source.
21 CFR 172.320 lists L-proline among the amino acids that may be safely used as nutrients added to foods.
Source: ecfr.gov (opens in a new tab)Under 21 CFR 172.320, added plus naturally present L-proline may not exceed 4.2 percent by weight of the total protein of the finished food.
Source: ecfr.gov (opens in a new tab)FDA's Substances Added to Food inventory lists L-proline with the technical effects flavor enhancer, flavoring agent or adjuvant, and nutrient supplement, and cites FEMA No. 3319.
Source: hfpappexternal.fda.gov (opens in a new tab)Health Canada's Workout Supplements monograph lists L-proline among its non-essential amino acids, with a dose range of 259.5 mg to 519 mg per day.
Source: webprod.hc-sc.gc.ca (opens in a new tab)
This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
L-proline suppliers
Manufacturers and distributors whose own websites say they sell it.
We are checking L-proline suppliers now
Every listing is checked against the supplier’s own website before it goes live, so this list fills in over the coming weeks. The specs and COA checklist above are ready today.
Sell L-proline? Request a listingFrequently asked questions
What forms of L-proline can brands buy?
Common forms include crystalline, fermented (plant-sugar) grade, uSP grade and food grade. Ask each supplier for the specification sheet of the exact grade they quote.
What should the COA for L-proline include?
Expect identity, assay, related substances, loss on drying and residue on ignition and heavy metals and microbiology, each with its method, specification and result for that lot.
How should L-proline be stored?
Store L-proline in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. It absorbs moisture readily, so keep liners tied and use desiccant in part-used containers. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
What is the regulatory status of L-proline?
21 CFR 172.320 lists L-proline among the amino acids that may be safely used as nutrients added to foods. Under 21 CFR 172.320, added plus naturally present L-proline may not exceed 4.2 percent by weight of the total protein of the finished food. FDA's Substances Added to Food inventory lists L-proline with the technical effects flavor enhancer, flavoring agent or adjuvant, and nutrient supplement, and cites FEMA No. 3319. Health Canada's Workout Supplements monograph lists L-proline among its non-essential amino acids, with a dose range of 259.5 mg to 519 mg per day.
More proteins and amino acids
- Collagen Peptideshydrolyzed collagen · collagen hydrolysate
- Creatine Monohydratecreatine · micronized creatine
- L-TheanineTheanine · N-ethyl-L-glutamine
- Pea ProteinPisum sativum protein · pea protein isolate
- Whey Protein IsolateWPI · whey isolate
- Whey protein concentrateWPC · WPC 80
- Whey protein hydrolysateWPH · hydrolyzed whey protein
- Micellar caseinmicellar casein isolate · casein micelles
- Milk protein concentrateMPC · MPC 70
- Milk protein isolateMPI · milk protein
- Sodium caseinatecasein sodium · caseinate sodium salt
- Calcium caseinatecasein calcium · caseinate calcium salt
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