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Cheddar cheeses were made from raw milk, pasteurised milk (72°C, 15 s) or milk produced from skim milk which had been microfiltered using an Alfa-Laval MFS-1 MF unit and mixed with pasteurised cream (72°C, 30 s). Microfiltration (MF) reduced the total bacterial count (TBC) by > 99% and MF cheesemilk had a lower TBC than pasteurised milk; counts of non-starter lactic acid bacteria (NSLAB) were < 1/ml. Cheeses were ripened at 10°C. Commercial graders and a trained taste panel found the pasteurised and MF cheeses to be of high and equivalent sensory quality but the raw milk cheese rapidly developed a strong and atypical flavour and was downgraded. NSLAB counts for the MF, pasteurised and raw milk cheeses were 43, 3·9 × 10² and 1·47 × 10⁵ cfu/g after pressing and 9·3 × 10⁶, 1·12 × 10⁷ and 1·19 × 10⁸ cfu/g after 11 weeks. The cheeses and their water-soluble extracts were indistinguishable by …