71A-12

D. L. VAN HEKKEN¹, M. H. Tunick¹, K. A. Soryal², and S. S. Zeng². (1) Dairy Processing and Products Research Unit, USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598, (2) E (Kika) de la Garza American Institute for Goat Research, Langston Univ., Agricultural Research and Extension Programs, PO Box 730, Langston, OK 73050-0730

Manufacturing cheeses is one way of utilizing caprine milk, although producing uniform quality cheeses that age well are challenged by the seasonal milk supply. Previously, we showed that using cheesemilk from goats at three different stages of lactation resulted in freshly manufactured Cheddar-like and Colby-like cheeses with different rheological properties. This phase of the study determined the changes in the rheological and proteolytic properties of these cheeses as they aged. Whole milk from Alpine goats (all began milking in April 2003) in early, middle, and late lactation (EL, ML, and LL; 4 to 5, 12 to 15, and 21 to 23 wk of lactation, respectively) was used to manufacture cheese according to Cheddar and Colby cheesemaking procedures. Cheeses aged at 4 °C for up to 16 wk (Colby-like) and 24 wk (Cheddar-like) were evaluated every 8 wk for proteolysis using SDS-PAGE and for changes in rheological properties using oscillatory shear, compression, and torsion tests. Although milk and cheese compositions and b-casein and a_S2-casein concentrations, for this herd and milking season, were similar for the three different stages of lactation for each cheese, the factors (currently unidentified) that influenced the formation of the cheese matrix were apparently different and resulted in the ML cheeses being harder, more rigid, and having higher viscoelastic properties than the EL or LL cheeses. Although proteolysis occurred with aging and the degradation of the proteins in the cheese matrix resulted in softer and less rigid cheeses that were more tolerant of deformation, the ML cheeses maintained the higher rheological values throughout aging, which suggests that cheeses of consistent quality and uniformity could be manufactured using ML milk. The EL and LL cheeses underwent more proteolysis during aging than the ML cheeses, which supports further investigation of the role of indigenous enzymes in cheese rheology and suggests that minor enzymes may factor into matrix formation.

Session 71A, Dairy Foods: General
8:30 AM - 12:00 PM, Tuesday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana