| HS Code | 668243 |
| Chemical Name | Zinc L-aspartate (zinc bis(L-aspartate)) |
| Cas Number | 36393-20-7 |
| Molecular Formula | C8H12N2O8Zn |
| Molecular Weight | 329.57 g/mol |
| Appearance | White to off-white crystalline powder |
| Odor | Odorless |
| Solubility | Soluble in water; practically insoluble in ethanol |
| Elemental Zinc Content | 19.8% |
| Chelate Structure | Zn2+ chelated by two L-aspartate molecules |
| Stability | Stable under normal storage conditions; protect from moisture and strong acids |
| Storage Conditions | Store in a cool, dry, well-ventilated area, away from light |
As an accredited Zinc L-Aspartate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Zinc L-Aspartate, 60 vegetarian capsules per bottle, packaged in an amber glass jar with tamper-evident seal and moisture-resistant closure. |
| Container Loading (20′ FCL) | 20′ FCL: palletized, drummed Zinc L-Aspartate securely stowed, weight-optimized, protected from moisture, safe for non-hazardous transport. |
| Shipping | Zinc L-Aspartate ships in sealed, moisture-resistant containers to prevent degradation. Store in a cool, dry area away from heat and sunlight. Non-hazardous under normal conditions, but avoid inhalation and direct contact. Ensure proper labeling and secure packaging to prevent spillage during transit. |
| Storage | Store Zinc L-Aspartate in a tightly sealed container in a cool, dry, well-ventilated area, away from direct sunlight, heat, and moisture. Keep the container closed when not in use. Avoid storage near strong oxidizers or incompatible materials. Ensure it remains out of reach of children and pets. |
| Shelf Life | Stable for at least two years when stored tightly sealed in a cool, dry place away from light and moisture. |
Direct compression of zinc L-aspartate dihydrate, Zn(C₄H₆NO₄)₂·2H₂O, into single-entity and multivitamin/mineral solid oral dose formats imposes measurable constraints on excipient selection, blend rheology, and tablet press parameters. The chelate’s plate-like crystalline habit, with a typical bulk density of 0.55–0.75 g/mL and a tapped density ratio of 1.20–1.45, generates segregation forces in low-shear bin blends when the particle size distribution D50 exceeds 150 μm and is paired with spray-dried mannitol of D50 below 100 μm. Pre-blending zinc L-aspartate with fumed silica at 0.3–0.8 wt% and microcrystalline cellulose type 102 for 8–12 min in a v-blender at 60–75% fill volume reduces assay variability to ≤2.0% RSD across 10 sampling points. Compression on a 16-station rotary tablet press using D-tooling requires main compression force between 10 kN and 20 kN; capping occurs above 25 kN or when dwell time falls below 20 ms, while magnesium stearate above 1.0 wt% and residual moisture above 4.0% w/w produce lamination and retarded dissolution. The formulation addition ratio for a 15 mg elemental zinc label claim is typically 75–82 mg zinc L-aspartate dihydrate per tablet, corresponding to 10.0–12.5 wt% of a 750 mg core; in multivitamin/mineral cores supplying 7.5–11 mg zinc, the use rate is 38–55 mg per unit dose. Industry compliance for this segment is anchored to EU Directive 2002/46/EC Annex II, which lists zinc L-aspartate among permitted zinc sources for food supplements, FDA 21 CFR 111 for dietary supplement cGMP, USP <2040> for disintegration, USP <711> for dissolution using 0.1 N HCl at 37±0.5°C, and USP <2091> for weight variation. As a chemical raw material placed on the EU market, the substance is also subject to REACH Regulation (EC) No 1907/2006 and CLP Regulation (EC) No 1272/2008. The downstream production process involves dispensing through 1000 μm screen sifting, dry blending, passing through an 800 μm conical mill, compression at 15–45 rpm turret speed, and aqueous film coating to a 3.0–4.0% weight gain. Terminal product types include clear film-coated tablets, two-piece HPMC capsules, and stick-pack oral powders reconstituted to 150 mL water.
In ready-to-drink beverage systems, the primary processing conflict is not zinc solubility but pH-dependent chelate integrity. Zinc L-aspartate disperses rapidly at 25°C in deionized water, but in citric acid–based matrices at pH below 3.5, protonation of the aspartate ligand shifts the equilibrium toward free Zn²⁺, which then complexes with polyphenolic fractions or orthophosphates and generates visible haze. Comparative stability screening in a model still beverage containing 0.30 wt% citric acid monohydrate and 0.15 wt% sodium citrate shows that turbidity remains below 0.5 NTU at pH 4.0–4.5 after 48 h at 25°C, but rises above 2.0 NTU at pH 3.2 when phosphate salts are present at 0.05 wt% as monobasic sodium phosphate. To deliver 2.5 mg elemental zinc per 250 mL serving, 12.5 mg zinc L-aspartate is added, equivalent to 0.005 wt% of finished beverage; for a 5.0 mg zinc claim, 25 mg is added, equivalent to 0.010 wt%. In dry mix powder systems for 500 mL reconstitution, 25–50 mg zinc L-aspartate is incorporated per 20 g sachet, equivalent to 0.125–0.25 wt% of dry powder, and tricalcium phosphate is omitted to avoid free-zinc precipitation after reconstitution. Above 5.0 mg elemental zinc per serving, taste-masking with 0.05–0.10 wt% rebaudioside A or erythritol is generally required to control metallic aftertaste. Regulatory compliance references include Regulation (EC) No 1925/2006 Annex II for food fortification in the EU, Codex CAC/GL 55-2005 for vitamin and mineral addition to foods, and ISO 20636:2018 as the ICP-MS mineral determination method adapted to fortified beverages. Microbiological verification for hot-filled low-acid ready-to-drink products references 21 CFR 113 for thermally processed low-acid foods packaged in hermetically sealed containers, with aseptic validation based on a 5-log spore reduction of Bacillus coagulans. The downstream production process for ready-to-drink products uses high-shear mixing at 1500–3000 rpm for 2–4 min, pH adjustment with 50% w/w citric acid solution before thermal treatment, hot-fill at 85–90°C for 15–30 s inversion hold, or UHT at 135–140°C for 3–5 s followed by aseptic dosing of zinc L-aspartate after cooling to 30–35°C. Published data for zinc L-aspartate in anthocyanin-rich fruit juice systems is limited; formulators commonly run accelerated sedimentation tests at 40°C and 75% RH for 6–12 weeks. Terminal product types include clear still flavored waters, isotonic sports drinks, and reconstitutable electrolyte powders in foil laminate stick packs.
Thermal processing of enteral formulas containing zinc L-aspartate presents a bimodal challenge: the amino acid ligand can participate in Maillard reactions with reducing sugars during sterilization, while insufficient homogenization can leave zinc localized in aqueous-phase droplets that sediment during storage. In a representative 1.0 kcal/mL polymeric enteral formula, zinc L-aspartate is added at 50–55 mg per 1000 kcal, equivalent to 0.005–0.006 wt% of final liquid, to deliver 10–11 mg elemental zinc per 2000 kcal. The production process introduces zinc L-aspartate into the water phase at 45–55°C under high-shear dispersion at 2500 rpm for 3–5 min, followed by two-stage homogenization at 200–300 bar first stage and 30–50 bar second stage. Sterilization is conducted in a tubular UHT unit at 140–145°C for 5–8 s for liquid aseptic packs, or in batch retorts at 121°C for 8–12 min for polymeric oral nutritional supplement bottles. For spray-dried clinical powders, zinc L-aspartate is dry-blended into the spray-dried base after sieving through 600 μm, because wet addition before spray drying can increase free zinc exposure on whey-protein or caseinate matrices. Compliance for this segment is governed by Commission Delegated Regulation (EU) 2016/128 for foods for special medical purposes, 21 CFR 101.9 for U.S. nutrition labeling, ISO 20636:2018 for mineral determination by ICP-MS, and AOAC 2011.14 for zinc in infant, adult, and pediatric nutritionals. Terminal product types include high-protein oral nutritional supplements in 200 mL aseptic bricks, polymeric tube-feeding formulas in 500–1000 mL retort-stable flexible packs, and powder clinical nutrition formulas in 400 g HDPE cans.
The formulating constraint in oral rinse manufacture is the interaction between zinc L-aspartate and anionic surfactant systems, which can produce zinc-surfactant complexes and visible turbidity at neutral pH. Alcohol-free mouthwash concentrates are therefore compounded using nonionic or amphoteric surfactants; sodium lauryl sulfate is omitted above 0.02 wt% because free zinc released from the aspartate ligand at pH 6.5–7.0 forms insoluble aggregates. Zinc L-aspartate is incorporated at 0.20–0.50 wt% in a mouthwash concentrate, delivering 400–1000 mg/kg total zinc in the diluted product; in a ready-to-use alcohol-free rinse, the final zinc content is 200–500 mg/kg. In toothpaste formulations, zinc L-aspartate is used at 0.5–1.0 wt% in a silica-base dentifrice with a pH of 5.8–6.5, providing 1000–2000 mg/kg total zinc without the astringency typical of zinc chloride at equivalent zinc concentrations. Compliance standards for this application include ISO 11609:2017 for dentifrice requirements and test methods, ISO 16408:2015 for oral rinses, and Regulation (EC) No 1223/2009 for cosmetics; where an antiplaque claim is pursued in the United States, the product falls under 21 CFR 355.50 oral antiseptic drug product requirements and requires USP 51 antimicrobial effectiveness testing. The production process is conducted at 20–30°C in stirred stainless-steel vessels with counter-rotating propeller agitation at 300–600 rpm; zinc L-aspartate is pre-dissolved in a 10 wt% stock solution at pH 4.5–5.0 and added after neutralization to avoid local precipitation. Terminal product types include alcohol-free zinc mouthwashes in 500 mL PET bottles, antiplaque toothpastes in aluminum barrier laminate tubes, and breath-freshening mouthspray concentrates packaged in 10–15 mL HDPE dropper bottles.
Feed mills replacing zinc sulfate monohydrate with zinc L-aspartate in pelleted broiler rations commonly observe reduced dust bound to zinc and lower oxidative pressure on fat-coated micro-ingredients, but the pelleted product requires revalidation of mineral recovery through the conditioner. In a typical poultry feed line, zinc L-aspartate is pre-blended with calcium carbonate or extruded rice hulls in a micro-ingredient premix and metered at 0.4–0.7 kg zinc L-aspartate per tonne of finished feed to provide 80–140 mg added zinc per kg complete feed, within species-specific total zinc limits established under the applicable national feed law. Steam conditioning is operated at 70–85°C for 30–60 s at 16–17% moisture; zinc L-aspartate survives pellet die compression of 2.5–4.0 MPa with mineral recovery by ICP-OES after feed acid digestion typically within 95–105% of theoretical dosage. Regulatory compliance for this segment is governed by Regulation (EC) No 1831/2003 on feed additives, with zinc chelate of amino acids hydrate authorised under Commission Implementing Regulation (EU) 2016/1095, ISO 6869:2000 for zinc determination by flame atomic absorption spectrometry, and AOAC 968.08 for minerals in feeds by atomic absorption spectrophotometry. Extruded pet food processing uses barrel temperatures of 120–135°C and 25–30% moisture, followed by drying at 110°C to moisture below 10%. Terminal product types include pelleted broiler grower feed, extruded adult dog kibble, and calf milk replacer powders in 20 kg multiwall paper sacks with polyethylene inner liners.
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Zinc L-aspartate is the zinc chelate of L-aspartic acid, typically supplied as a white to off-white crystalline powder with the anhydrous formula C8H10N2O8Zn and a molecular weight of 327.56 g/mol; the corresponding elemental zinc content is 19.96% on an anhydrous basis. The product is not defined by a single harmonized pharmacopeial monograph, so commercial specifications commonly identify the material by zinc assay rather than a model number, with finished goods coded as “Zinc L-Aspartate 20%” or equivalent. Representative raw material acceptance parameters include a zinc assay of 19.0–20.5% by inductively coupled plasma optical emission spectrometry at 213.856 nm after microwave digestion, loss on drying not exceeding 8.0% at 105°C, and residue on ignition within 0.1% of the dosed mass. Heavy metal limits are normally set against the finished product’s permitted daily exposure under ICH Q3D rather than as a single raw material value; where USP 2232 is used, manufacturers validate recovery of Pb, As, Cd, and Hg in the presence of the chelate matrix. The product is used primarily in solid oral dosage forms and dry powder nutritional blends where a fully reacted amino acid chelate is preferred over inorganic zinc salts to minimize free zinc cation interactions with phytate, dietary fiber, and polyphenols. Unlike zinc sulfate monohydrate, which releases highly bioaccessible Zn2+ immediately upon dissolution and can accelerate oxidation of ascorbic acid in dry blends at intermediate water activities, zinc L-aspartate retains the metal center in a ligand field that reduces redox catalytic activity; controlled trials with ferric ammonium sulfate titration show lower pro-oxidant response at equivalent elemental zinc load, although published data for direct comparison under ICH stability conditions is limited. The product is not intended for aqueous parenteral administration; sterility and endotoxin claims require separate monograph compliance.
Zinc sulfate monohydrate contains approximately 36% elemental zinc and dissolves rapidly in aqueous phase, creating a local pH drop in unbuffered suspensions. In effervescent tablet granulations, this acidity can react with carbonate components during wet granulation and reduce carbon dioxide yield. Zinc L-aspartate, with an elemental zinc content near 20%, exhibits a more neutral pH in a 1% aqueous dispersion and provides carboxylate buffering capacity in the pH 5.0–6.5 range. The difference is not limited to gastric irritation; it affects blend segregation, redox stability, and dissolution testing. During direct compression, spray-dried zinc sulfate fines below 75 µm can migrate toward the bottom of the hopper under vibration, whereas zinc L-aspartate batches with a controlled particle-size distribution between 74 µm and 250 µm show better residence-time distribution in paddle-bin blenders. In dissolution testing using USP Apparatus 2 at 75 rpm in 900 mL simulated gastric fluid without pepsin, zinc L-aspartate tablets typically release more than 80% of label zinc within 30 min at pH 1.2, while zinc oxide under the same conditions may release less than 20% within 30 min when the acid concentration is insufficient to solubilize the oxide. Table 1 compares relevant properties.
| Source | Typical Zn (w/w) | Aqueous behavior | Primary use constraint |
|---|---|---|---|
| Zinc sulfate monohydrate | 36.0% | Freely soluble; acidic pH | metallic taste, gastric irritation, ascorbic acid oxidation |
| Zinc oxide | 80.3% | Insoluble in water; acid-dependent dissolution | low solubility under suppressed gastric acid |
| Zinc bisglycinate | 30.6% | Soluble chelate; near-neutral pH | higher raw material cost; moisture sensitivity |
| Zinc L-aspartate | 19.96% anhydrous | Soluble; mildly acidic to neutral | lower zinc density; larger formula weight at fixed dose |
Direct-compression premixes containing zinc L-aspartate are typically blended in a 600 L bin blender for 20–30 min at 8–12 rpm after geometric dilution of the active premix. For tablets with a target dose of 15 mg elemental zinc per dosage unit, the chelate addition is 75.2 mg per tablet at 19.96% zinc; at this concentration, the excipient-to-active ratio exceeds 30:1 for a 750 mg tablet, so blend uniformity is governed by excipient flow and segregation rather than active solubility. In production-scale trials on a 20-station rotary press with 9.5 mm round tooling, blend uniformity samples analyzed by ICP-OES met USP 905 acceptance criteria with RSD values of 2.8–4.1% for magnesium stearate levels of 0.5–0.75%; increasing magnesium stearate above 1.5% or extending blend time beyond 45 min did not improve ejection force but increased disintegration time from 14 min to 21 min when tested according to USP 701. Therefore, the chelate is not a direct-compression binder; tablet hardness must be built with microcrystalline cellulose or dibasic calcium phosphate dihydrate at 30–55% of formulation mass. Lubrication sensitivity is low compared with effervescent citric acid systems, but over-lubrication still delays dissolution in simulated gastric fluid at pH 1.2. Roller compaction is preferred over slugging when dry granulation is required because the brittle fracture mode of the crystalline chelate under roll pressure of 5–8 kN/cm produces granules with a d50 of 300–500 µm and fewer fines below 75 µm than high-shear wet granulation, which can mobilize zinc ions and form localized aspartic acid-rich regions during tray drying at 55°C.
In two-piece hard shell capsule operations, the chelate’s bulk density, typically 0.55–0.70 g/cm3, and tapped density, typically 0.75–0.95 g/cm3, place it in the same filling class as light granular acetaminophen. On a dosator-type capsule filler, a 0 size capsule at target fill weight 400 mg can maintain weight RSD below 2.0% when the powder bed is conditioned to 35–45% RH; higher humidity causes powder adhesion to the dosator tip and increases the incidence of split capsules. Tamping-pin machines are less sensitive to electrostatic charge but require flow aids such as silicon dioxide at 0.2–0.5% to prevent ratholing in the hopper. Precompression of the slug at 5–8 kN during encapsulation is not recommended because the crystalline structure undergoes brittle fracture, generating fines that can leak from the cap-body gap and compromise weight consistency.
Dry beverage sticks with pH 3.0–3.5 after reconstitution pose a chelate-stability challenge because protonation of the aspartate ligand can release zinc as the free cation. Formulation work at 1.0 mg elemental zinc per 200 mL serving shows that zinc L-aspartate remains acceptable in clarity at pH 3.5 for 24 h at 25°C, but at pH 3.0 a slight haze appears after 8 h; this is attributed to ligand dissociation and interaction with citrate buffer species. When citrate is present at 0.2% w/v, the L-aspartate chelate remains transparent longer than zinc sulfate but does not match the clarity of zinc bisglycinate at the same zinc load; published data for this specific configuration is limited. For powdered beverage applications, the material should be sieved through a 40 mesh screen and combined with maltodextrin or glucose syrup solids as a carrier before addition of flavor oils. If the flavor system contains aldehydes such as citral, the zinc load should be kept below 3.0 mg of elemental zinc per liter to minimize Schiff-base interactions with primary amines released from degraded aspartate. Packaging in high-barrier PET/AL/PE laminates with oxygen transmission rate below 0.5 cm3/(m2·day·bar) is required for a 24-month shelf life. Sensory panel evaluation at 0.5 mg zinc per 100 mL in a sweetened tea base showed no significant metallic aftertaste versus zinc sulfate at the same dose, but the difference diminished above pH 4.5 because the acid environment masked the taste difference. Addition of zinc L-aspartate to dry beverage premixes should therefore occur before final pH adjustment and after the dry flavor carrier has adsorbed liquid flavor oil, because direct contact with concentrated citrus oil at water activity below 0.25 causes uneven wetting and clump formation that does not fully redisperse during reconstitution.
Thermogravimetric analysis of zinc L-aspartate dihydrate shows a dehydration event beginning near 90°C and decomposition above 180°C; therefore, processing in dryers or coating pans should be limited to bed temperatures not exceeding 70°C. In fluid-bed granulation, spraying an aqueous binder solution containing the chelate at 0.5% solids into a bed at 55–60°C does not produce detectable free aspartic acid after 30 min; however, extended exposure to 65% RH at 25°C for 7 days raises loss on drying from 2.0% to 6.8% and produces soft agglomerates that pass through a 20 mesh screen but increase variation in tablet weight from 1.2% to 2.6%. For moisture-sensitive premixes, a package desiccant of silica gel or molecular sieve at 2–5 g per unit is used; calcium oxide desiccants are not recommended because they can raise the pH of the headspace and destabilize the aspartate ligand through ammonia evolution. When the product is stored in ICH climatic zone IVb conditions of 30°C/75% RH in open trays, visual yellowing occurs within 14 days; this is not necessarily accompanied by zinc release but indicates Maillard-type reactions between the amino acid and reducing sugars in the blend. Formulators should therefore avoid lactose monohydrate as a filler in high-humidity regions unless the product is coated or packaged with an oxygen and moisture barrier. Differential scanning calorimetry can be used to confirm the absence of free L-aspartic acid, which shows a characteristic endotherm near 270°C while the zinc chelate decomposes above 180°C. Dry premixes containing zinc L-aspartate should not be exposed to steam sterilization or autoclaving because the combination of heat and condensate produces sticky granules and measurable ligand loss above 100°C.
Method transfer for zinc L-aspartate quantification across quality control laboratories typically uses ICP-OES at 213.856 nm after microwave-assisted digestion in concentrated nitric acid; the method should be validated for specificity, linearity over 0.5–5.0 mg/L, and recovery between 98.0% and 102.0% against NIST-traceable zinc standard solution. Because the chelate binds to EDTA and may interfere with simple complexometric titration, chelatometric methods require sample ashing at 550°C for 4 h in porcelain crucibles before titration with 0.05 M EDTA and Eriochrome Black T indicator. Finished product release under 21 CFR 111 requires testing for identity, strength, and contaminants; zinc L-aspartate is not listed in every national pharmacopeia, so a supplier CoA and a validated in-house method often constitute the regulatory file. For EU supplements, the substance falls under the Food Supplements Directive 2002/46/EC only through national zinc compound lists; manufacturers should confirm inclusion in the specific Member State before labeling with a health claim under Regulation (EC) No 1924/2006. The product is incompatible with strong oxidizing agents and concentrated mineral acids; it should not be dry-blended with sodium metabisulfite in effervescent systems because sulfur dioxide release follows first-order degradation kinetics at water activities above 0.35. Storage in tightly closed, light-resistant containers at 15–25°C and relative humidity below 60% is recommended; opened containers should be reclosed immediately after dispensing.
