The influence of a food-grade long-chain polyphosphate mixture on the growth and survival of spoilage micro-organisms during storage in an experimental processed cheese spread formulation was evaluated. The emulsifying salt was added to the cheese blend at a concentration of 0.5% or 1.0%. A control product was also manufactured, which contained monophosphate instead of polyphosphate as emulsifying salt, with all other ingredients being identical to those in the experimental processed cheese spread. Half of the finished products were subjected to accelerated shelf-life testing at 37 °C for 10 days, whereas the other half of them was stored refrigerated at 4 °C for 120 days. Microbiological analyses (enumeration of viable cell counts, mesophilic sulphite-reducing clostridia, coliforms, yeasts and moulds) and sensory tests were performed at regular intervals. The results showed that polyphosphates had a beneficial effect on the shelf-life of the processed cheese spread tested in that they significantly reduced (P<0.05) the growth or survival rates of spoilage bacteria, especially of mesophilic sulphite-reducing clostridia. Polyphosphates also beneficially influenced the sensory, including textural properties of the experimental processed cheese spread. All the samples containing less than 1% polyphosphate showed signs of butyric blowing significantly earlier (P<0.05), during both accelerated shelf-life tests and regular refrigerated storage, than did the products fortified with 1% polyphosphate. In conclusion, the suitability of the long-chain polyphosphate formulation tested for shelf life extension of processed cheese spreads was demonstrated.