1. Vitamin A Palmitate 250 SD CWS (CAS 79-81-2): An Overview
Vitamin A Palmitate 250 SD CWS/S Toc. Stab. is a spray-dried, cold-water-dispersible powder in which the oil-soluble vitamin A ester retinyl palmitate (CAS 79-81-2, C36H60O2, molecular weight 524.87 g/mol) is dispersed in a water-soluble carrier matrix and standardised to 250,000 IU/g. The grade described here is stabilised with both dl-alpha-tocopherol and sodium ascorbate, carried on modified starch, maltodextrin and vegetable oil, with silicon dioxide as anti-caking agent.
Every element of that name is a functional decision rather than a marketing label: 250 is the potency in IU per gram, SD means spray-dried, CWS means cold-water dispersible, S marks the stabilised grade and Toc. Stab. states that tocopherol is part of the antioxidant system. Reading the name correctly is most of the work of specifying the product, because two vitamin A powders with the same 250,000 IU/g headline figure can behave completely differently in a beverage line, a premix or a tablet press.
2. The Active Ingredient: Retinyl Palmitate
| Property | Value / note |
|---|---|
| Chemical name | Retinyl palmitate (vitamin A palmitate) |
| CAS Registry Number | 79-81-2 |
| Molecular formula | C36H60O2 |
| Molecular weight | 524.87 g/mol |
| Chemical class | Retinoid ester: all-trans retinol esterified with palmitic acid |
| Character | Oil-soluble, hydrophobic; practically insoluble in water |
| Theoretical oxygen content | 6.10% |
| Native potency (pure ester) | about 1,818,000 IU/g by the USP conversion |
Retinyl palmitate is the ester of all-trans retinol with palmitic acid. The esterification is not cosmetic: the free alcohol, retinol, is markedly less stable, and the palmitate ester is the form most often used when vitamin A has to be stored, blended and shipped before it is consumed. Inside the body the ester is hydrolysed back to retinol, which is why the nutritional activity of the ester is expressed in IU or in retinol equivalents rather than in milligrams of the ester itself.
The 1,818,000 IU/g figure is worth memorising because it is the ceiling against which every commercial grade is measured. By the USP convention 1 IU equals 0.3 µg of all-trans retinol or 0.55 µg of all-trans retinol palmitate; dividing one gram by 0.55 µg gives the potency of the pure ester. Everything below that figure is dilution by carrier.
3. What “SD CWS” Actually Means
The technical problem this product solves is straightforward to state and hard to execute: vitamin A is an oil that oxidises readily, but a large part of the market – beverages, dairy drinks, instant powders, feed premixes – handles only dry, free-flowing solids and mixes them into water.
Spray drying solves the physical problem. An emulsion of the vitamin A oil in an aqueous solution of the carrier is atomised into a hot gas stream; the water flashes off and each droplet becomes a particle in which tiny oil droplets are embedded in a glassy carbohydrate matrix. The matrix is what protects the vitamin: it limits oxygen diffusion, it keeps the oil from bleeding onto the particle surface, and it converts an oil into a powder with a defined particle-size distribution.
Cold-water dispersibility (CWS) solves the application problem, and it is not automatic. When a spray-dried powder is dropped into cool water, the carrier must wet and dissolve quickly enough that the particles separate before they clump; if the surface is hydrophobic or the particles are too fine, they form lumps with dry cores. This is why the grade carries a specific sieve specification rather than just a “powder” description:
| Sieve (US) | Requirement | Practical meaning |
|---|---|---|
| No. 40 (425 µm) | 100% passing | No oversize agglomerates that would not disperse |
| No. 60 (250 µm) | ≥ 90% passing | Most of the powder is in the fast-dispersing range |
| No. 100 (150 µm) | ≥ 45% passing | Enough fines to wet out quickly without dusting excessively |
The three-tier sieve spec is the difference between a powder that dissolves in a cold beverage and one that floats. A buyer comparing two 250,000 IU/g offers who does not compare sieve data is comparing only half the product.
The carrier system is the other half. Modified starch provides the glassy matrix and the emulsifying function; maltodextrin adjusts the matrix solids and the taste neutrality; vegetable oil is the carrier phase in which the vitamin A is dissolved before emulsification. The combination is chosen so that the finished powder is free-flowing, low-dust, and stable at ambient temperature – and so that it adds no flavour, which matters in dairy and beverage applications.
4. Specifications and Potency Accounting
| Parameter | Specification | What it protects |
|---|---|---|
| Appearance | Light yellow, free-flowing powder | Carrier quality and oxidation state |
| Identification | TLC (EP); colour reaction with antimony(III) (USP); TLC (USP) | Confirms the retinoid identity, not just the potency |
| Assay | ≥ 250,000 IU/g | The delivered vitamin A potency |
| Absorbance ratio | ≥ 0.85 | Isomer and degradation check on the extracted vitamin |
| Loss on drying | ≤ 5.0% | Free moisture; a stability indicator |
| Solubility | Dispersible in cool water, milky emulsion | The CWS functionality itself |
| Heavy metals | ≤ 10 mg/kg | Carrier and process contamination |
| Arsenic | ≤ 1.0 mg/kg | Carrier sourcing |
| Lead | ≤ 2.0 mg/kg | Carrier sourcing |
| Total plate count | ≤ 1,000 CFU/g | Spray-drying and filling hygiene |
| Mould and yeast | ≤ 100 CFU/g | Moisture control and packaging integrity |
| Coliforms | < 3.0 MPN/g | Hygienic processing |
| Salmonella | Negative in 25 g | Food-safety release criterion |
Converting IU into grams of active material
The potency figure is the one people misread most often, so it is worth doing the arithmetic explicitly. Using the USP convention of 0.55 µg of retinyl palmitate per IU:
| Quantity | Calculation | Result |
|---|---|---|
| Active ester at 250,000 IU/g | 250,000 × 0.55 µg | 137.5 mg/g = 13.75% |
| Carrier, antioxidant and moisture | 100% − 13.75% | about 86% |
| Retinol equivalents at 250,000 IU/g | 250,000 × 0.3 µg | 75 mg RE/g |
| Vitamin A in 1 kg of powder | 250,000 × 1,000 | 250 million IU |
| Powder needed per tonne of feed at 10,000 IU/kg | 10,000 ÷ 250,000 × 1,000 g | 40 g per tonne |
Two consequences follow from that table, and both are commercially important. First, 86% of what you ship is carrier – so freight, packaging and warehouse space are being spent mostly on starch and maltodextrin, which is exactly why high-potency liquid forms exist for applications that can handle oil. Second, the arithmetic scaling from a feed requirement to a premix inclusion rate is trivial once the IU/g is fixed, and a formulator who does that calculation on paper before choosing the grade avoids the common error of buying a 500,000 IU/g product for an application that will be diluted to 10,000 IU/kg anyway.
The absorbance ratio is not a redundant test
An assay measures how much vitamin A activity is present; the absorbance ratio measures what state it is in. Vitamin A absorbs in the ultraviolet, and the shape of that absorption – expressed as a ratio between the absorbance at the principal maximum and the absorbance of the same solution after a defined correction – shifts when the all-trans isomer has been partly converted to cis isomers or when degradation products have accumulated. A batch can therefore measure 260,000 IU/g and still fail an absorbance ratio specification, because the material has been over-heated during spray drying or over-exposed during handling. For a buyer, the ratio is the check that separates a well-processed powder from one whose potency number is being carried by a lot of partly degraded material.
5. The Antioxidant System: Why Two Antioxidants
The name of this grade includes Toc. Stab. for a reason: vitamin A oxidation is the main mechanism by which the product loses value, and a single antioxidant cannot cover both phases of a spray-dried particle.
- dl-alpha-tocopherol is oil-soluble. It partitions into the vitamin A oil droplets inside the particle, which is where the most vulnerable material sits – unsaturated conjugated double bonds in direct contact with dissolved oxygen. Tocopherol intercepts peroxyl radicals in the lipid phase and is regenerated by ascorbate.
- Sodium ascorbate is water-soluble. It partitions into the aqueous carrier phase, where it acts as an oxygen scavenger and as the reducing partner that regenerates oxidised tocopherol. It also addresses the metal-ion route of oxidation by keeping trace iron and copper in their reduced states in a way that limits their pro-oxidant cycling.
The two together are more than the sum of their parts: tocopherol alone is consumed and cannot regenerate; ascorbate alone does not reach the oil phase. This is why a specification that states “stabilised” without naming the antioxidants should be treated as incomplete – the identity of the antioxidant system determines the shelf life, and “stabilised” alone does not say whether it will last twelve months or three.
6. Stability: What Actually Degrades the Potency
Vitamin A loss is not one reaction but several running in parallel, and each is controlled by a different variable:
| Degradation route | Driven by | Practical control |
|---|---|---|
| Autoxidation of the conjugated chain | Oxygen, light, heat | Antioxidant system, nitrogen flushing, opaque packaging, cool storage |
| Isomerisation (trans to cis) | Heat, light, acidic conditions | Control spray-drying temperature; avoid prolonged heating in the application |
| Hydrolysis of the ester | Moisture, acidity | Loss on drying ≤ 5.0%; avoid acidic matrices |
| Metal-catalysed oxidation | Trace Fe, Cu | Heavy-metal specification; avoid metal contact in processing |
| Physical loss of the oil phase | Poor encapsulation, abrasion | Matrix quality; particle-size control; gentle handling |
In feed applications the dominant loss is usually process-related rather than storage-related: pelleting and expansion subject the powder to steam and mechanical shear, and a meaningful fraction of the vitamin can be destroyed in that step, which is why feed-grade vitamin A is normally added with an overage and why the retention figure under a customer’s specific pelleting conditions matters more than the room-temperature shelf life on the certificate. In beverage and dairy applications the dominant losses are light and oxygen during processing and filling, plus the loss onto packaging surfaces; in tablet applications the dominant stress is the compression step and the moisture of the granulation.
Two practical rules apply across all of these. First, do not judge a vitamin A powder by its assay alone – an assay run on freshly opened material says nothing about what survives twelve months in the customer’s warehouse. Second, ask for retention data under your process conditions, not just a general shelf-life statement, because “24 months at 25 °C in the original unopened container” and “what is left after my pelleting step” are two different questions.
7. Applications
This grade is designed for systems that are dry at the point of addition and aqueous at the point of use.
| Application | Why this form fits | Practical note |
|---|---|---|
| Beverages and dairy drinks | Disperses in cool water to a milky emulsion without an oil ring | Add to the aqueous phase with agitation; protect from light through filling |
| Dairy alternatives and plant-based drinks | Neutral carrier adds no flavour to a delicate base | Check that the carrier system is acceptable for the claimed allergen and labelling status |
| Instant powders and dry mixes | Free-flowing, low dust, blends without segregation | Sieve match to the rest of the blend reduces segregation in filling |
| Feed and premix | Handles and weighs like a premix ingredient | Apply an overage for pelleting; confirm retention under your conditions |
| Dietary supplements | Dry vitamin A for tablets, capsules and sachets | Compression stability should be tested in the actual formulation |
| Cosmetics | Introduces an oil-soluble retinoid into a dry or low-oil format | Formulators should confirm compatibility with the rest of the emulsion system |
In every one of these, the underlying reason for choosing a cold-water-dispersible powder over the pure oil is the same: the product eliminates a liquid handling step and a solubility constraint at the same time, at the cost of shipping 86% carrier.
8. Regulatory and Safety Notes
- Food and feed use is governed by the vitamin A addition limits and labelling rules of the destination market; the permitted addition level, the permitted forms and the labelling of retinol equivalents differ between jurisdictions and should be confirmed for each market rather than assumed.
- Nutrition claims must follow the local claim regulation. This page describes the product as a vitamin A source; it makes no therapeutic or disease-related claim.
- The carrier system matters for labelling: modified starch, maltodextrin, vegetable oil, sodium ascorbate, dl-alpha-tocopherol and silicon dioxide all have to appear in the ingredient list, and allergen statements should be based on the actual carriers used, not on the generic product name.
- Handling: the powder is a dust-generating food ingredient. Use local exhaust ventilation when weighing, avoid eye contact, and store in a cool, dry place away from light and strong odours (vitamin A powder can pick up off-notes).
9. Procurement Guide
| Decision | What to specify | Why it matters |
|---|---|---|
| Potency | State the IU/g required and whether it is “as is” or on a dried basis | A 250,000 IU/g statement means nothing without the basis |
| Form | CWS (cold water dispersible) versus plain dry powder | Only the CWS grade disperses in cool water without lumping |
| Antioxidant system | Name the antioxidants (tocopherol, ascorbate) and ask for the intended shelf life | “Stabilised” alone is not a specification |
| Particle size | The three-tier sieve data, not just “powder” | Determines dispersion behaviour and segregation in blends |
| Carrier | Full carrier list plus allergen and GMO statements | Drives labelling and market access |
| Microbiology | TPC, mould and yeast, coliforms, Salmonella limits | A food-grade release criterion, not a formality |
| Retention data | Stability data under your process (pelleting, baking, filling), not only warehouse shelf life | The loss that matters happens in your plant |
| Packaging | Fibre drum with food-grade liner; confirm nitrogen flushing if offered | Oxidation protection starts with the pack |
10. Frequently Asked Questions
What does 250 SD CWS mean?
250 is the potency in IU per gram, SD means spray-dried, and CWS means cold-water dispersible – the powder disperses in cool water to a milky emulsion rather than floating or clumping. See the full specification overview for the complete parameter set.
How much active vitamin A is actually in the powder?
At 250,000 IU/g, about 13.75% of the powder is retinyl palmitate (137.5 mg/g), using the USP conversion of 0.55 µg of palmitate per IU. The rest is carrier, antioxidant and residual moisture.
What is the difference between the oil and this powder?
The oil is more concentrated and cheaper per unit of vitamin A, but it requires oil-phase handling and cannot be dispersed in water. See the form comparison article for the decision table.
Why does the specification list two antioxidants?
Because oxidation happens in two phases of the particle: tocopherol works inside the oil droplets, ascorbate works in the aqueous carrier and regenerates the tocopherol. A single antioxidant leaves one of the two phases unprotected. See the stability article.
Why is the absorbance ratio tested as well as the assay?
The assay measures how much vitamin A activity is present; the absorbance ratio measures the isomer and degradation state. A batch can pass the potency specification while carrying a significant fraction of cis isomers or degradation products, which the ratio catches.
Can this be used in organic-certified products?
That depends on the certification scheme and on the origin of every carrier and antioxidant in the formulation, not on the vitamin A itself. Ask for a specific statement covering the full carrier list for the target market.
References and Further Reading
- CAS Registry Number 79-81-2; PubChem CID 5280531 (retinyl palmitate, C36H60O2, molecular weight 524.87 g/mol).
- USP convention for vitamin A activity: 1 IU = 0.3 µg all-trans retinol = 0.55 µg all-trans retinol palmitate; the pure ester therefore corresponds to about 1,818,000 IU/g.
- Spray drying of oil-in-water emulsions for encapsulation of lipophilic vitamins: standard food-engineering practice for glassy carbohydrate matrices.
- Related reading on this site: Vitamin A Palmitate Forms Compared and Vitamin A Stability: Antioxidants, Carrier Effects and Premix Losses.
Disclaimer: this article describes the technical characteristics, handling and regulatory context of a food- and feed-grade vitamin A preparation for professional readers. It is not a safety data sheet, not a nutrition or health claim, and not a substitute for the labelling and addition limits that apply in your market. Analytical values quoted are typical commercial specifications; the specification that applies to your order is the one stated on the certificate of analysis for that batch.
Request a quotation for Vitamin A Palmitate 250 SD CWS/S Toc. Stab. (CAS 79-81-2): send the quantity, required potency and destination port to polybluechem@163.com. COA, SDS and carrier declaration available on request.