Effects of ultra-high pressure homogenization on microbial and physico-chemical shelf-life of milk
Special Symposium - Innovations in Food Technology (LMC Congress)
Hygiene, Hygienic Design & Unit Operations (Food-5a)
Keywords: ultra-high pressure homogenization, milk shelf-life, microbial inactivation, physico-chemical characteristics
Julieta Pereda*, Victoria Ferragut, Joan Miquel Quevedo, Buenaventura Guamis, Antonio José Trujillo
Centre Especial de Recerca Planta de Tecnologia dels Aliments (CERPTA), CeRTA, XiT, Departament de Ciència Animal i dels Aliments, Facultat de Veterinària, Universitat Autònoma de Barcelona, 08193 Bellaterra (Spain)
Ultra high-pressure homogenization (UHPH) is a new food preservation treatment that is being developed as an alternative to heat-treatments. To date, physico-chemical and microbiological changes generated by UHPH in milk have been studied after treatment but not during storage. Therefore, the aim was to compare the effects of heat and UHPH treatments on the microbial and physico-chemical shelf-life of milk during storage at 4ºC.
Milk was processed using a Stansted High Pressure homogenizer. Treatments applied were 200 and 300 MPa with inlet temperature (Ti) = 40ºC and 30ºC. UHPH-treated milks were compared to high-pasteurized milk (PA; 90ºC-15 s). Microbiological quality was studied by enumerating total counts, psychrotropic bacteria, lactococci, lactobacilli, enterococci, coliforms, spores and Pseudomonas spp. Physico-chemical parameters assessed were viscosity, color, pH, acidity and residual lactoperoxidase and alkaline phosphatase activities.
After treatment, UHPH was as efficient in reducing psychrotrophic, lactococci and total bacteria as was PA treatment, reaching important reductions (~3.5 log cfu/ml). Coliforms, lactobacilli and enterococci were completely eliminated. UHPH treatment produced milk with a microbial shelf-life between 14 -18 days, similar to that of PA milk. UHPH reduced the L* value of treated-milks and it induced a reduction in viscosity values of milks treated at 200 MPa compared to PA milks, however these differences would not be appreciated by consumers.
Therefore, alternative methods like UHPH give new opportunities to develop milk with an equivalent shelf-life to that of PA milk in terms of microbial and physico-chemical characteristics.
Presented Thursday 20, 09:35 to 09:50, in session Hygiene, Hygienic Design & Unit Operations (Food-5a).
