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item Van Hekken, Diane
item Tunick, Michael
item Malin, Edyth
item Holsinger, Virginia

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2005
Publication Date: 8/18/2005
Citation: Van Hekken, D.L., Tunick, M.H., Malin, E.L., Smith, P.W., Holsinger, V.H. Rheological characterization of low and full-fat mozzarella cheese made with microfluidized milk. 2005: In Press.

Interpretive Summary: Low-fat cheeses are in great demand because of their reduced fat content but tend to have less than desired texture compared to full fat cheeses. Homogenization of milk, a process that breaks up milk fat into smaller droplets, has been shown to improve the texture of some Cheddar cheeses and slightly improves the ability of low fat Mozzarella cheese to melt. A new homogenization process, called microfluidization, uses very high pressure to break the fat droplets into even smaller droplets than homogenization that are more widely distributed in the milk. The effects of high pressure microfluidization on the textures of low-fat Mozzarella have yet to be determined. In this study, milk was microfluidized under different condi- tions of pressure and temperature and then used to make low fat and full fat Mozzarella cheeses. The textures of the cheeses were then evaluated using different methods and compared to that of cheeses made from milk that twas not microfluidized (controls). Cheeses that were similar to controls could be made if the milk was microfluidized at l0C and low pressures. Cheese texture was not as good if the milk was microfluidized at the higher temperatures at all pressures because the fat droplets formed by this process were too small and the fat and protein relationships were changed enough to alter the internal body of the Mozzarella cheese. Understanding the impact of new processing techniques on the final texture of a cheese helps the food scientist develop new cheeses for the consumer. Microfluidization of milk is useful for making cheeses with no or low melting ability or with a crumbly texture.

Technical Abstract: Microfluidization of cheese milk at different temperatures and pressures was studied to determine its effect on the meltability and rheological pro- perties of low-fat Mozzarella cheese. Pasteurized milk, standardized at either l or 3.2% fat and heated to l0, 43, or 54C, was microfluidized at pressures of 34, l04, or l72 MPa and used to make Mozzarella cheese by standard procedures. After hand stretching of the curd in 77C water and brining, cheeses were vacuum packaged and stored at 4C until assayed. Cheese made from non-microfluidized milk served as controls. After l and 6 weeks of storage, samples were tested for meltability, hardness, springi- ness, cohesiveness, shear stress and shear strain at point of fracture, and viscous and elastic moduli. During the hot water stretching step, only con- trol cheeses and cheeses made with milk microfluidized at l0C could be stretched; the others had very short curds that did not melt together into a uniform mass. The rheology testing results confirmed these differences, as the cheeses made with control milks and milk processed at the lowest temperature at the lower pressures had the lowest hardness, shear stress at fracture, and elastic and viscous moduli, and the highest meltability, co- hesiveness, and shear strain at fracture. Analysis of torsion results show- ed that full fat cheeses made from control milk and milks microfluidized at 10C or 34 or l04 MPa were significantly more rubbery than all other cheeses Microfluidization of cheese milk at temperatures above the melting point of of milk fat at different pressures resulted in finer emulsions and altered the relationship between protein and lipid. This change in component inter- actions influenced the formation of the curd matrix and resulted in Mozza- rella cheeses with significantly altered melt & rheological properties.