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  • Food grade and technical grade are not interchangeable

    Citric acid is citric acid. The molecule does not change between grades. What changes is everything around it: how much of the material is the molecule, what else is present, how finely it is milled, and what the producer is prepared to certify about it.

    That distinction is why ordering by chemical name alone is the single most common cause of a material arriving that cannot be used.

    What grade actually controls

    • Assay. The proportion that is the named substance. Food and pharmaceutical grades are typically held to a tighter range than technical grade.
    • Impurity limits. The important part. Food and pharma grades carry defined limits on heavy metals, arsenic, and residues relevant to that use. Technical grade often does not set them at all — not because the material is dangerous, but because nobody testing it was asked the question.
    • Physical form. Particle size, bulk density and whether the material is granular, fine powder or prilled. This is not cosmetic; it governs dissolution rate, dosing accuracy and how the material behaves in a dry blend.
    • Documentation. A food or pharma grade should come with a certificate of analysis referencing a recognised monograph. Technical grade may come with far less.

    Why substitution goes wrong

    The failure is rarely dramatic. More often it is a batch that dissolves too slowly and throws out a continuous process, a powder that cakes in the hopper because the moisture spec was looser than expected, or a finished product that fails an audit because the intake paperwork does not reference the right standard.

    The reverse also happens: buying pharmaceutical grade for an application that only needs technical, and paying a premium for a specification nobody downstream will ever ask about.

    Specify by monograph where one exists

    For many food additives there is a recognised standard — FCC for food chemicals, USP or BP for pharmaceutical use, and the E-number framework for additives sold into food in many markets. Naming the standard on the purchase order removes most of the ambiguity in one line.

    “Citric acid” is an invitation to interpretation. “Citric acid monohydrate, food grade, FCC, fine granular” is an order.

    What to put on the enquiry

    1. Chemical name and CAS number. The CAS number removes any doubt about which compound and which hydration state you mean — monohydrate and anhydrous are different materials with different dosing.
    2. Grade and standard. Food, pharma, feed or technical, and the monograph if your process references one.
    3. Physical form. Powder, granular, flake or prill, with a mesh range if it matters.
    4. Quantity and packing. Including whether you need a specific pack size to suit your handling.
    5. Destination market. Permitted additives and declaration rules differ, and this affects what can be supplied.

    Check the arriving material against it

    When the consignment lands, read the certificate of analysis against the specification you ordered to — not against the last certificate you filed. Appearance and assay are the two fields that catch a grade substitution fastest. Our note on reading a certificate of analysis covers what each field is telling you.

    Every product in our catalogue lists its CAS number, appearance and solubility so you can check the basics before you enquire. Send us your house specification with the enquiry and we will check the producer’s specification against it before the order is placed.

  • Sodium benzoate or potassium sorbate: choosing a preservative

    Sodium benzoate and potassium sorbate turn up in the same product categories often enough that they get treated as alternatives. In practice they solve overlapping but different problems, and the choice between them is usually decided by two things: the pH of your product and what is actually spoiling it.

    pH decides whether benzoate works at all

    Sodium benzoate is only meaningfully active in acidic conditions. It works through the undissociated form of benzoic acid, and the proportion of the preservative present in that form falls away sharply as pH rises. Below about pH 4.0 to 4.5 it is efficient. Approaching pH 5 you are adding cost without adding much protection.

    That makes it well suited to carbonated soft drinks, fruit cordials, vinegar-based sauces and pickled products — systems that are strongly acidic by design.

    Potassium sorbate follows the same principle but stays useful considerably further up the scale, to around pH 6.5. That extra range is why it appears in baked goods, cheese, dips and dressings where benzoate would be doing very little.

    They cover different organisms

    Sorbate is strongest against yeasts and moulds. It is comparatively weak against bacteria. Benzoate has a broader reach across yeasts, moulds and bacteria, but only within its narrow pH window.

    So the practical question is not simply “which is better” but “what is spoiling this product”. A mildly acidic dip going off through yeast is a sorbate problem. A low-pH drink at risk from a wider range of organisms is a benzoate problem. A product exposed to both, at a pH where each is only partly effective, is a case for using them together — which is why the combination is so common.

    Handling differences that matter in the plant

    • Solubility. Potassium sorbate is highly soluble in water and is normally dosed as a solution. Sodium benzoate is freely soluble too, and both can go straight into a liquid batch without pre-dispersion.
    • Flavour. Benzoate can contribute a perceptible note at higher use levels, particularly in delicately flavoured drinks. Sorbate is generally the quieter of the two.
    • Interactions. Benzoate in the presence of ascorbic acid and certain metal ions has been the subject of well-documented concern in beverages. If your formulation contains both, it is worth reviewing.
    • Labelling. Both carry E numbers — E211 for sodium benzoate, E202 for potassium sorbate — and permitted levels vary by market and product category. Check the destination market before finalising a dose.

    A short decision path

    Start with the measured pH of the finished product, not the target pH of the recipe. If it sits below 4.5 and the risk is broad, benzoate is the efficient choice. If it sits above that, sorbate is the one still working. If you are between the two, or the product is exposed to both fungal and bacterial spoilage, a combined system usually costs less than pushing either one to its limit alone.

    Then confirm the grade. Both are supplied in food grade for this use, and the specification should state the assay and the physical form you are dosing — granular and powder behave differently in a dry blend.

    See the full preservatives range, or tell us your application and we will point you to the right product and grade.

  • How to read a certificate of analysis

    Every consignment of a food or pharma grade chemical should arrive with a certificate of analysis. It is the producer’s statement of what that particular batch actually tested at. Used properly it is the difference between accepting a pallet and discovering a problem three weeks into production.

    The mistake we see most often is treating the COA as a formality — checking that one exists, filing it, and moving on. A COA is only worth anything if you read it against the specification you bought to.

    What a certificate of analysis is

    A COA reports results for a specific, identified batch. That is what separates it from a technical data sheet, which describes the product in general terms and gives typical or guaranteed ranges. The TDS tells you what the product is; the COA tells you what this batch measured.

    If a document gives you ranges rather than single measured values, you are looking at a specification sheet, not a certificate of analysis. Both are useful. They are not interchangeable.

    The fields that matter

    • Batch or lot number. This must match the number printed on the sacks or drums you received. If it does not, the certificate belongs to different material.
    • Date of manufacture. Combined with the shelf life, this tells you how much usable life the material has left when it reaches you — not when it left the producer.
    • Assay or purity. The headline number. Check the test method as well as the figure; the same nominal purity measured by different methods is not always comparable.
    • Appearance. Sounds trivial, but a mismatch here — granular where you expected fine powder — is the earliest warning that the wrong grade has shipped.
    • Loss on drying / moisture. Often the field that determines whether a hygroscopic material will cake before you use it.
    • Heavy metals and residual limits. Frequently reported as “conforms” rather than a number. If your own specification sets a limit, ask for the measured value.

    Three things buyers routinely miss

    Typical values presented as batch results. Some certificates repeat the same figures batch after batch. If every COA for a product shows an identical assay to two decimal places, you are being sent typical values on certificate letterhead.

    The retest date rather than the expiry. Many inorganic salts do not expire so much as require retesting after a period. A retest date is not a use-by date, and treating it as one wastes usable material.

    Test methods left unstated. “Assay 99.5%” means little without the method. Where the specification you are buying to names a method, the certificate should name the same one.

    Check it on arrival, not at point of use

    Match the batch number on the certificate against the batch number on the packaging before the pallet is put away. It is a two-minute check at goods-in and it catches the errors that are expensive to unpick later — mixed batches on one pallet, a certificate for the previous shipment, or a grade substitution nobody flagged.

    Keep the certificate with the intake record for that batch. When a customer complaint arrives eighteen months later, the ability to trace a finished lot back to the raw material batch and its certificate is what turns a guess into an answer.

    What to ask for when you order

    State on the purchase order which documents you require and in what form. If you need the certificate before the goods ship, say so — it is much easier to resolve a discrepancy while the material is still with the producer.

    We supply the certificate of analysis with every consignment, and technical data sheets and safety data sheets are available on request. If you have a house specification you buy to, send it with your enquiry and we will check the producer’s specification against it before the order is placed.

    Browse the catalogue or send us an enquiry with the product, grade and quantity you need.