Spore-forming bacteria in commercial cooked, pasteurised and chilled vegetable purées Original Research Article

In commercial purées of broccoli, carrot, courgette, leek, potato and split pea, pasteurized in their final packaging and analysed at two periods, Bacillus spp. were the dominant aerobic mesophilic bacteria (AMB). Initial numbers were generally lower than 2 log cfu g−1. They increased up to 6–8 log cfu g−1after about 20 days of storage at 10°C. At 4°C, numbers of AMB after 20 days were lower than 3 log cfu g−1in potato purée, lower than 4 log cfu g−1in leek purée, and between 3 and 6 log cfu g−1in other products. Strict anaerobes were in markedly lower numbers than AMB. At all storage temperatures tested courgette purée usually showed the most rapid bacterial growth and spoilage. On this product, an increase in storage temperature from 4°C to 10°C resulted in a threefold reduction in time to 5 log cfu g−1, and time to spoilage. Growth kinetics of AMB in courgette purée at 20°C, 15°C, 10°C, 6·5°C and 4°C were determined using a mathematical model. Three hundred and forty eight isolates were identified using the API system. Bacillus circulans, B. macerans and B. polymyxa were among the main species isolated from products stored at 4°C and 10°C, while B. subtilis and B. licheniformis were the dominant species in product stored at abuse temperature. Bacillus cereus was isolated from all storage conditions, but mostly from products stored at abuse temperature.