P-Cresol
P-Cresol, systematically 4-methylphenol, is the para isomer of the three methyl substituted phenols, formula C7H8O, molar mass 108.14, CAS number 106-44-5. It occurs naturally in coal tar, in wood smoke, in several essential oils and in the volatile fraction of foods such as cheese, coffee, roasted meat and whisky.
In flavour and fragrance work it is a trace level material with a heavy phenolic, tar like, animalic odour often described as horse or stable at concentration, opening out into smoky, leather and narcissus facets on extreme dilution. It is used in parts per billion in food, where it contributes the smoky and barnyard notes of aged cheese, smoked meat and dark spirits, and rather more freely in perfumery, where it is a classic component of narcissus, jasmine and leather accords.
The pure material is a white crystalline solid that melts at about 35 degrees Celsius, so it is handled warm as a colourless to pale yellow liquid and darkens toward pink or brown on exposure to air and light. It is moderately soluble in water at roughly two grams per hundred millilitres and freely soluble in ethanol, ether and alkali solutions, the last because the phenolic hydroxyl is acidic. It is corrosive to skin and toxic on contact, which decides how it is handled.
We source bulk P-Cresol from top China manufacturers for our partners. The manufacturer is in Shandong. A smaller requirement can ship in a combined container with other ingredients.
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- Function
- Flavours and Aromas
Specifications
| Item | Specification |
|---|---|
| Appearance | Crystalline solid at room temperature, clear liquid when molten |
| Colour | White to pale yellow, 50 Hazen maximum when molten |
| Odour | Characteristic phenolic and tar like, true to reference sample |
| Assay by gas chromatography | 99.0 percent minimum |
| Identification by infrared spectrum | Conforms to reference spectrum |
| Freezing point | 34.0 degrees Celsius minimum |
| Ortho and meta cresol, total | 0.5 percent maximum |
| Phenol content | 0.2 percent maximum |
| Water content | 0.2 percent maximum |
| Distillation range | 200 to 203 degrees Celsius |
| Non volatile residue | 0.05 percent maximum |
| Heavy metals as lead | 10 mg/kg maximum |
| Lead | 1.0 mg/kg maximum |
| Arsenic | 1.0 mg/kg maximum |
Common Markets Grades
Two markets share the same molecule. Technical grade p-cresol, generally 98 to 99 percent with the balance made up of the ortho and meta isomers, is the large volume position and goes into antioxidants, notably butylated hydroxytoluene, into agrochemicals and into dyestuffs. Its specification is written around isomer distribution, freezing point and colour rather than around odour.
Flavour and fragrance grade is the same compound purified further, typically 99 percent or better with tight limits on phenol, on the other cresol isomers and on colour, and it is released on an odour assessment against a retained reference in addition to the analytical result. Because the neat material is a corrosive solid that must be melted to be dosed, it is very commonly sold as a dilution at one or ten percent in ethanol, triacetin or propylene glycol, and those solutions are the form most flavour houses actually buy.
Applications
- Smoke and barbecue flavours, where it supplies the phenolic backbone alongside guaiacol derivatives
- Cheese flavours, particularly aged and blue types, at trace level
- Whisky, rum and dark spirit flavourings, reproducing a cask and phenolic character
- Roasted meat and grilled flavour compounds, contributing a charred facet
- Coffee and cocoa flavours, used at very low level for depth
- Fine fragrance, in narcissus, tuberose and jasmine accords where an animalic note is wanted
- Leather and tobacco fragrance accords
- Chemical intermediate for butylated hydroxytoluene and other hindered phenol antioxidants
- Intermediate for agrochemical and dyestuff manufacture
- Analytical reference standard in smoke flavour and off flavour testing
China Manufacturers of P-Cresol
Top P-Cresol manufacturers in China.
Company names and logos are the property of the manufacturers themselves. They are listed here because our own directory records them as producing this ingredient. A listing is not an endorsement by them, and we do not represent them or speak on their behalf.
Regulatory Status
In the United States 21 CFR 172.515 lists p-cresol as a synthetic flavouring substance and adjuvant permitted for use in food, and it holds FEMA GRAS status as a flavouring substance under FEMA number 2337. Use levels in food are extremely low and are governed by good manufacturing practice, meaning no more than the quantity needed to achieve the intended flavour effect. Industrial and intermediate uses fall outside food law and are covered by the requirements applying to substances on the Toxic Substances Control Act inventory.
In the European Union p-cresol is an authorised flavouring substance on the Union list established under Regulation (EC) No 1334/2008, identified by a FLAVIS number in the phenol group. Flavourings are not assigned E numbers. The substance is separately classified as hazardous under the classification, labelling and packaging regulation, being acutely toxic and corrosive, so transport and workplace controls apply to the neat material even though the food use level is minute. The Joint FAO and WHO Expert Committee on Food Additives has evaluated the phenol and phenol derivative flavouring group, and Codex flavouring guidance applies where national law adopts it.
Manufacturing Process
The classical and still widely used synthetic route runs from toluene. Toluene is sulphonated with sulphuric acid or oleum under conditions that favour substitution at the para position, giving p-toluenesulphonic acid. That acid is neutralised to its sodium salt and fused with molten sodium hydroxide at high temperature, which displaces the sulphonate group and yields sodium p-cresolate. Acidification of the melt with sulphuric acid or with carbon dioxide releases the free cresol, which separates as an organic layer.
The crude cresol is washed to remove salts, dried, and purified by vacuum fractional distillation, which is where the para isomer is separated from residual ortho and meta material and from phenol and xylenols. Because the boiling points of the isomers are close, high efficiency columns and careful reflux control are needed, and some plants finish the separation by crystallisation, taking advantage of the much higher melting point of the para isomer. The purified material is held molten under nitrogen or flaked and packed as a solid in lined drums, with flavour grades given a final polish distillation and an odour clearance before release. An alternative supply route isolates cresols from the cresylic acid fractions recovered from coal tar or from petroleum refinery spent caustic streams.
