Dairy Ingredients for Food Processing

206 Chapter 9

number and size can achieve moderate

success. However, greater success has been

achieved in recent years by modifying the

fatty acid composition of the milk fat through

changes to the dairy cow ’ s diet.

Many reports in the literature concern

modifi cation of the cow ’ s diet to increase the

content of unsaturated fatty acids in milk fat,

thus reducing solid fat content. These have

been reviewed by Ashes et al. (1997) and

more recently by Murphy (2000). Because

the long - chain fatty acids in milk fat, i.e.,

all of the C18 acids and approximately 50%

of C16 acids, originate from the cow ’ s

diet, they have been the focus for dietary

manipulation of milk fat. In a cow ’ s digestive

system (rumen), microorganisms normally

hydrolyze and hydrogenate dietary lipid,

mainly resulting in saturated and partially

saturated fatty acids entering the blood

stream to be transported to the mammary

gland, where milk is synthesized. In the

mammary gland, the delta - 9 stearoyl desatu-

rase enzyme then converts a signifi cant pro-

portion of the saturated C18 : 0 fatty acid,

stearic acid, into the monounsaturated C18 : 1

fatty acid, oleic acid.

butter, homogenization temperature, and the
required fat content of the fi nished product.
Starter culture and salt can also be added at
this stage. Following homogenization, the
blend is pumped into a silo and from there to
a scraped surface heat exchanger for cooling
before packing.

Spreadable Butter

Butter is recognized as a high - quality natural
product with a unique fl avor; unfortunately,
it is also well known that butter is hard and
virtually unspreadable at refrigerator tem-
perature, and this property makes it compare
unfavorably with dairy spreads and table
(tub) margarines. The primary reason for the
fi rmness of butter is the high content of satu-
rated fatty acids in milk fat that are solid at
low temperatures (Table 9.2 ). Legislation
prohibits any fat other than milk fat to be
present in butter, which limits options avail-
able to butter manufacturers to improve
butter spreadability. As mentioned earlier,
physical working to disrupt the three -
dimensional butter structure or application of
a cream - tempering regime to alter fat crystal

Figure 9.5. Low - fat butter production (APV Unit Systems, Denmark). Fearon and Golding (2008).

Reworker

Caseinate solution

Cream

Butter

Vacuum treatment

(vacuum worker)

Buttermilk

Culture

Low-fat butter homogenizer

Butter silo

Packaging