title: High pressure homogenization versus heat treatment: effect on survival, growth, and metabolism of dairy Leuconostoc strains.
abstract: The effect of high pressure homogenization (HPH) with respect to a traditional heat treatment on the inactivation, growth at 8°C after treatments, and volatile profile of adventitious Leuconostoc strains isolated from Cremoso Argentino spoiled cheeses and ingredients used  for their manufacture was evaluated. Most Leuconostoc strains revealed elevated resistance to HPH (eight passes, 100 MPa), especially when resuspended in skim milk. Heat treatment was more efficient than HPH in inactivating Leuconostoc cells at the three initial levels tested.  The levels of alcohols and sulfur compounds increased during incubation at 8°C in HPH-treated samples, while the highest amounts of aldehydes and ketones characterized were in heated samples. Leuconostoc cells resuspended in skim milk and subjected to one single-pass HPH treatment  using an industrial-scale machine showed remarkable reductions in viable cell counts only when 300 and 400 MPa were applied. However, the cell counts of treated samples rose rapidly after only 5 days of storage at 8°C. The Leuconostoc strains tested in this work were highly resistant  to the inactivation treatments applied. Neither HPH nor heat treatment assured their total destruction, even though they were more sensitive to the thermal treatment. To enhance the inhibitory effect on Leuconostoc cells, HPH should be combined with a mild heat treatment, which in addition  to efficient microbial inactivation, could allow maximal retention of the physicochemical properties of the product.
authors.affiliation: Instituto de Lactología Industrial (INLAIN, UNL-CONICET), Facultad de Ingeniería Química, Santiago del Estero 2829, 3000 Santa Fe, Argentina. dgugliel@fiq.unl.edu.ar
authors.forename: D M
authors.initials: DM
authors.lastname: Guglielmotti
authors.forename: F
authors.initials: F
authors.lastname: Patrignani
authors.forename: R
authors.initials: R
authors.lastname: Lanciotti
authors.forename: M E
authors.initials: ME
authors.lastname: Guerzoni
authors.forename: J A
authors.initials: JA
authors.lastname: Reinheimer
authors.forename: A
authors.initials: A
authors.lastname: Quiberoni
mesh_terms: D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D005506:Food Contamination / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D005524:Food Technology / Q000379:methods; D006358:Hot Temperature; D006801:Humans; D007934:Leuconostoc / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D050296:Microbial Viability; D011312:Pressure; D013997:Time Factors