L-isoleucine
L-isoleucine is an essential, branched-chain amino acid with two chiral centers, an isomer of leucine. Commercial L-isoleucine is made by bacterial fermentation of sugars, then separated from the broth, purified by ion exchange and crystallized. Brands buy it as a white crystalline powder, mostly as part of branched-chain amino acid blends and essential amino acid mixes, and less often on its own.
Suppliers sell different products under the same name. Specify the one you need.
Standard fine crystalline powder for capsules, tablets and dry blends.
L-isoleucine agglomerated or coated with a small amount of lecithin (often sunflower or soy) so it wets and disperses in water; check the lecithin source for allergen labeling.
L-isoleucine made by bacterial fermentation of corn, cassava or beet sugar; the source and any vegan statement appear on the supplier's spec.
L-isoleucine tested to the USP monograph, used where a compendial grade is required for supplements.
Compare each result with your own specification when the lot arrives.
Store L-isoleucine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. 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.
Record assay and source for each lot, and note the lecithin type for instantized lots. Rotate stock FEFO.
Facts from regulators and standards bodies, each linked to its source.
21 CFR 172.320 lists L-isoleucine 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-isoleucine may not exceed 6.6 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-isoleucine with the technical effects flavoring agent or adjuvant and nutrient supplement.
Source: hfpappexternal.fda.gov (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.
Manufacturers and distributors whose own websites say they sell it.
Manufacturer · Raleigh, NC
North American subsidiary of the Ajinomoto Group. It supplies pharmaceutical- and food-grade amino acids made by fermentation, in pack sizes from R&D pails to bulk, plus custom amino acid blends.
Suppliers are in alphabetical order and none pays to appear. Each claim is checked against the supplier’s own website on the date shown. Ask for the specification sheet and a recent COA before you order, and confirm details with the supplier.
Common forms include crystalline, instantized, fermented (plant-sugar) grade and uSP grade. Ask each supplier for the specification sheet of the exact grade they quote.
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.
Store L-isoleucine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. 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.
21 CFR 172.320 lists L-isoleucine among the amino acids that may be safely used as nutrients added to foods. Under 21 CFR 172.320, added plus naturally present L-isoleucine may not exceed 6.6 percent by weight of the total protein of the finished food. FDA's Substances Added to Food inventory lists L-isoleucine with the technical effects flavoring agent or adjuvant and nutrient supplement.
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