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Cold microfiltration removes microorganisms, somatic cells from skim milk.

The physical removal of microorganisms from skim milk by microfiltration is becoming increasingly attractive to the dairy industry because of the efficiency of the process.

Usually, this process is performed at temperatures of approximately 50 C. But additional shelf life and quality benefits might be gained by conducting the microfiltration process at low temperatures. This type of cold microfiltration could also minimize any microbial fouling of the membrane and prevent the germination of thermophilic spores.

Scientists at Cornell University optimized a cold microfiltration process that would effectively remove microbial and somatic cells from skim milk. Their carbon dioxide-aided cold microfiltration process could be economically attractive to the dairy industry and directly benefit the quality and shelf life of dairy products.

An experimental microfiltration setup containing a tubular commercial ceramic membrane, which had a nominal pore size of 1.4 micrometers, was used for the microfiltration of raw skim milk at a temperature of 6 [+ or -] 1 C.

As processing conditions, the researchers used cross-flow velocities of 5 m/s to 7 m/s, and transmembrane pressures of 52 kPa to 131 kPa. All of the microfiltration experiments were performed in triplicate. The permeate flux was determined gravimetrically. Microbiological, chemical and somatic cell analyses were performed to evaluate the effect of microfiltration on the composition of skim milk.

The permeate flux increased drastically when velocity increased from 5 m/s to 7 m/s. The critical transmembrane pressure range conducive to maximum fluxes was 60 kPa to 85 kPa. When the scientists conducted microfiltration under optimal conditions, they were able to very efficiently remove vegetative bacteria, spores and somatic cells, as well as achieve the near complete transmission of proteins into the microfiltered milk.

To further enhance the flux, a carbon dioxide backpulsing system was developed. Backpulsing removes particles that have collected in the pores and on the surface of a membrane by applying a periodic reversal of the transmembrane pressure. This system was able to both increase the flux and maintain it steadily for an extended period of time.

Further information. Carmen Moraru, Department of Food Science, Cornell University, 364 Stocking Hall, Ithaca, NY 14853; phone: 607-255-8121; email: cim24@cornell.edu.

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Publication:Emerging Food R&D Report
Date:Nov 1, 2015
Words:361
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