Factors affecting the inactivation of the natural microbiota of milk processed by pulsed electric fields and cross-flow microfiltration

• Published in: Journal of dairy research Vol. 78; no. 3; pp. 270 - 278
• Main Authors: Rodríguez-González, Oscar, Walkling-Ribeiro, Markus, Jayaram, Shesha, Griffiths, Mansel W
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.08.2011
• Subjects: Animal productions; Animals; Bacteria - isolation & purification; Biological and medical sciences; Cattle; coliform bacteria; Colony Count, Microbial; cream; Electric fields; electrical conductivity; Electricity; Filtration - methods; Food Handling - methods; Food industries; food processing; Fundamental and applied biological sciences. Psychology; High temperature; high-temperature short-time pasteurization; Inactivation; lipid content; microfiltration; Microorganisms; Milk; Milk - microbiology; Milk and cheese industries. Ice creams; Pasteurization; pulsed electric fields; skim milk; Temperature; Terrestrial animal productions; Vertebrates; fat content; Milk natural microbiota; cross-flow microfiltration; fluid milk; pulsed electric field; hurdle technology; electrical conductivity; Electrical conductivity; Fluid; Dairy product; Microflora; Fat content; Inactivation; Microfiltration; Electric field; Technology; Pulsed field; Dairy industry; Milk
• ISSN: 0022-0299; 1469-7629
• DOI: 10.1017/S0022029911000367

Prior to processing milk and cream were standardised and homogenised. Skim milk was cross-flow microfiltered (CFMF) prior to treatment with pulsed electric fields (PEF) or high temperature short time (HTST) pasteurization. The effect of temperature of the skim milk and product composition on the efficacy of PEF treatment was determined. The electrical conductivity of the product was related to fat and solids content and increased 5% for every g/kg increase of solids and decreased by nearly 0·7% for every g/kg increase of fat. From the three microbial groups analyzed (mesophilic, coliform, and psychrotroph) in milks differences (P<0·05) in the inactivation of mesophilic microorganisms were observed between the counts following PEF treatment, while HTST pasteurization resulted in higher reductions in all different counts than those obtained after PEF. Increasing the skim milk temperature prior to PEF treatment to about 34°C showed equivalent reductions in microbial counts to skim milk treated at 6°C in half the time. The reductions achieved by a combination of CFMF and PEF treatments were comparable to those achieved when CFMF was combined with HTST pasteurization. A higher reduction in coliform counts was observed in homogenised products subjected to PEF than in products that were only standardised for fat content.