PPM (Phenol Parts per Million)

Definition and Context

PPM (Phenol Parts per Million) denotes the concentration of phenolic compounds in malt, measured as the number of parts phenols per million parts of malt. In practice this is often expressed as mg phenol per kg of dry malt (mg/kg), which corresponds to roughly 1 ppm ≈ 1 mg/kg in solid samples. Phenols mainly originate from smoke- or peat-based kilning and contribute significantly to the aroma and flavour profile of whisky.

Typical levels and variation

The smoke level in malt is often in the range around 20–50+ ppm, but variations arise depending on the type of peat, the composition of the source water, and drying parameters such as temperature and duration, as well as the moisture content in the malt.

Relation to finished whisky

PPM in malt correlates with phenol content in the finished whisky, but is not directly equivalent. During fermentation and distillation, the availability, evaporation and distribution of phenols change, which can alter the concentration and profile of phenols in the whisky. Therefore, two malts with similar ppm can yield different phenol profiles in the final whisky.

Phenol types and flavour contributions

Phenols in malt include compounds such as phenol, cresols, guaiacol and syringol, as well as other polyphenols. These contribute smoky, dried, spicy and medicinal notes in whisky and vary with the peat source as well as the drying parameters.

Measurement methods

Analysis of phenols in malt is typically performed by: - GC-MS or LC-MS for specific phenols - HPLC for quantification of individual compounds - Folin-Ciocalteu-based colorimetric assays for assessment of total phenol content (more general)

Practical remarks and applications

• The ppm level is used as a guideline in planning the malt profile and peat/smoke content during kilning.
• Distillation and aging can alter the final phenol profile in whisky; therefore, the ppm in malt is a starting point and not a guarantee of the whisky's phenol content.