SPORE‐FORMING THERMOPMLES IN STERILISED MILK

Abstract

SummarySpore‐forming bacteria can be found in a wide variety of substances, including soil. They will survive temperatures of commercial sterilisation of milk. As they are present in at least 8% of raw milk supplies (in West Midlands) there seems little hope of applying control measures on the farm. Lethal time temperature combinations run very close to those at which milk becomes markedly caramelised. In order to ensure that the coldest bottle in most sterilisers is heated adequately it would be necessary to overheat other bottles. Rapid cooling is thought to be the secret of avoiding caramelisation, and is certainly a means of preventing rapid growth of surviving spore‐forming thermophiles, but is less effective against spore‐forming mesophiles. It might be possible to effect control of all spore‐formers by flash heating in bulk to 125o‐130oC. (257o‐266oF.) for 1 min. or less, and to avoid caramelisation by immediate cooling to homogenising temperature, bottling and sterilising at low pressure. Before any general recommendation could be made this would have to be subject to exhaustive trial both in the laboratory and dairy.