Tesis doctoral de Sílvia De Lamo Castellví
The effects of high hydrostatic pressure (hhp) treatment, and the ability for survival, repair and growth of three human pathogenic microorganisms (yersinia enterocolitica, escherichia coli and salmonella enterica strains) were investigated in skimmed milk and model cheese made with and without starter culture. Inoculated samples were treated at 300, 400 and 500 mpa (except s. Enterica) for 10 min at 20ºc or at room temperature and analysed at 1, 2, 4, 7, 10 and 15 days (in the case of skimmed milk samples) and at 0, 1, 7 and 15 days (in the case of model cheese samples) to study the behaviour of bacterial population over time. Skimmed milk and cheese samples produced with starter culture showed the maximum lethality at 400 and 500 mpa and no significant differences in the baroresistant behaviour of microorganisms were detected, except in the case of y. Enterocolitica strains. Nevertheless, it is important to remark that in cheese produced without starter culture, it was necessary to apply more pressure to obtain the same reduction than in cheese produced with starter culture. In fact, the most effective treatment was mainly 500 mpa, for e. Coli strains and 400 mpa for s. Enterica strains. ability to repair and grow was not observed in model cheese produced with starter culture and cell counts of treated samples decreased after 15 days of storage at 8 or 12ºc. Whereas, in skimmed milk and cheese produced without starter, all pressurized samples showed the trend to repair and grow during the storage period. These results suggest that the presence of starter and low ph are the main factors to control the ability to recover and grow of y. Enterocolitica, e. Coli and s. Enterica strains inoculated in this type of cheese and treated by hhp.
Datos académicos de la tesis doctoral «Behaviour of pathogenic gram negative bacteria inoculated in skimmed milk and model cheese treated with high hydrostatic pressure«
- Título de la tesis: Behaviour of pathogenic gram negative bacteria inoculated in skimmed milk and model cheese treated with high hydrostatic pressure
- Autor: Sílvia De Lamo Castellví
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 30/03/2006
Dirección y tribunal
- Director de la tesis
- Marta Capellas Puig
- Tribunal
- Presidente del tribunal: romeo Toledo
- esther Sendra nadal (vocal)
- ramón Gervilla fernández (vocal)
- claudia Ruiz capillas (vocal)