Rheological Characteristics Of Young Montery Jack Goat Milk Cheese By Y.W. Parks, PhD Agricultural Research Station, Fort Valley State University, Fort Valley, GA 31030 Reprinted with Permission |
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Two lots of Monterey Jack goat milk cheeses were manufactured using bulk goat milk produced at the Georgia Small Ruminant Research and Extension Center, Fort Valley State University, Fort Valley, GA, to characterize various rheological properties of the young cheeses stored at 4oC for 1 and 4 weeks. The experimental goat cheeses were examined for the major rheological parameters, including meltability, texture profile analyses (TPA), dynamic analysis, and torsion analysis as described in Tunick et al. (1993) and Ma et al. (1996). Meltability of the cheeses was assayed using Schreiber test. TPA was performed using the Universal Testing Machine (Sintech l/G, MTS Systems Corp., Eden Prairie, MN). Cylindrical plugs were compressed by 75% twice at a crosshead speed of 100 mm/min, and hardness, springiness, and cohesiveness were calculated. Dynamic analysis was conducted using Rheometrics Dynamic Analyzer (Model RDA-700, Rheometrics Scientific, Piscataway, NJ). Samples (25.4 x 4-5 mm) were glued between two disks and tested at a frequency of 100 rad/s. Elastic (G’) and viscous (G”) moduli and complex viscosity (eta*) were recorded. Torsion analysis was carried out using Torsion Gelometer (Gel Consultants, Inc., Raleigh, NC). Sample plugs were cut and milled to proper capstan shape and tested in gelometer. Shear stress and shear strain were used to calculate shear modulus (stress/strain). Results showed that the curds of the goat milk cheeses appeared to be knitting with time, as reflected in the springiness, G’ as well as shear strain results shown in Table 1. The increased meltability and viscosity values of the cheeses were also observed in the elevated G”, and eta* data with the storage time. As the cheeses aged, they became softer as seen by hardness and shear stress values, and more rubbery as seen when plotting shear stress and strain on a texture map. The lot 2 cheese was a softer, springier, and more viscous than the lot 1, probably because of compositional differences. It was concluded that the young goat milk Monterey Jack cheeses became more elastic, cohesive, meltable, viscous and softer after 4 weeks of aging presumably due to proteolysis. |
REFERENCES Ma, L., M.A. Drake, G.V. Barbosa-Canovas, and B.G. Swanson. 1996. Viscoelastic properties of reduced- fat and full-fat Cheddar cheeses. J. Food Sci. 61:821-823. Tunick, M.H., Mackey, K.L., Shieh, J.J., Smith, P.W., Cooke, P., and Malin, E.L. 1993. Pheology and microstructure of low-fat mozzarella cheese. Int. Dairy J. 3:649-662.
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Table
1. Texture profiles, viscoelasticity and torsion
characteristics of Monterey Jack goat milk cheeses stored at
4oC for one and four week periods.|
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