Dairy Sheep Symposium - the Department of Animal Sciences ...

EVALUATION OF SENSORY AND CHEMICAL PROPERTIES OF MANCHEGO
CHEESE MANUFACTURED FROM OVINE MILK OF DIFFERENT
SOMATIC CELL LEVELS
J.J. Jaeggi* 1 , Y. M. Berger 2 , M.E. Johnson 1 , R. Govindasamy-Lucey 1 ,
B.C. McKusick 3 , D.L. Thomas 3 , W.L. Wendorff 4 .
1 Wisconsin Center for Dairy Research
2 University of Wisconsin Agriculture Research Station, Spooner, WI
3 University of Wisconsin-Madison Department of Animal Science
4 University of Wisconsin – Madison Department of Food Science
University of Wisconsin-Madison, Madison WI 53706
Abstract
As ovine milk production increases in the United States, somatic cell count (SCC) is increasingly
used in routine ovine milk testing procedures as an indicator of flock hygiene and health.
Ovine milk was collected from 72 East Friesian (EF) - crossbred ewes that were machine milked
twice daily. The milk was segregated and categorized into three different average SCC groups: <
100,000 (Group I); 100,000 to 1,000,000 (Group II); and > 1,000,000 cells/ml (Group III). Milk
was stored, frozen at –19°C for 4 mo. Milk was then thawed at 7°C over a 3-d period before
pasteurization. Casein content and casein to true protein ratio decreased with increasing SCC
group 3.99, 3.97, to 3.72% casein, and 81.42, 79.66, to 79.32% casein to true protein ratio,
respectively. Milk fat varied from 5.49, 5.67, and 4.86 in Groups I, II and III, respectively.
Manchego cheese was manufactured in duplicate from the three different SCC groups. As the
level of SCC increased, the time required for visual flocculation increased, resulting in longer
times to reach the desired firmness for cutting. Cheese yield at 1 d decreased from 16.03 to 15.97
to 15.09% with increasing SCC group. Lower yields were attributed to lower casein and fat
contents of the higher SCC milk. Cheeses were coated with a polymeric coating and ripened at
7°C and 85% humidity for 9 mo. Cheese samples were analyzed at 3 d, 1, 3, 6, and 9 mo for
soluble nitrogen and both total and individual free fatty acids. Cheese graders noted increased
levels of rancidity in the higher SCC level cheeses at each of the sampling points. No major
differences were noted in cheese texture between the different SCC levels.
(Key words: Manchego cheese, ovine, somatic cell counts, fatty acids)
Introduction
The American dairy sheep industry, particularly in states like Wisconsin is beginning to grow
both in milk volume and cheese production. In 1983, 11.4 million kg of sheep milk cheese was
imported into the U.S. and by 1998 those imports had increased to 28.2 million kg, which is onehalf
of global importation (FAO, 1998). Currently in Wisconsin, most cheese manufactured from
dairy sheep milk is produced in small cheese plants or on-farm generally with artisinal manufacturing
protocols. Compared to dairy cattle, dairy ewes produce less milk but of a much richer
content (6 to 8% milk fat, 4 to 6% milk protein, Anifantakis, 1986). Since milk production per
ewe is low, milk is typically frozen in polyethylene-lined pails until a sufficient quantity is
collected for manufacturing.
SCC is often used to differentiate between healthy and infected mammary glands in rumi-
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