Food Biochemistry and Food Processing (2 edition)

BLBS102-c23 BLBS102-Simpson March 21, 2012 13:44 Trim: 276mm X 219mm Printer Name: Yet to Come

436 Part 4: Milk

ssp.shermaniimetabolize lactate to form the carbon dioxide re-

sponsible for the eye formation. These cheeses are ripened in hot

rooms (20–22◦C) to optimize the growth of the propionibacteria

and allow eye formation.

Ripening of cheese is a time-intensive process; thus, there is

much interest in accelerating the ripening process without an

adverse effect on cheese quality. Addition of enzymes, includ-

ing the use of encapsulated enzymes; addition of attenuated or

modified starter cultures and adjunct cultures; elevated ripen-

ing temperatures; and the addition of cheese slurry have been

explored as possible means to shorten the ripening processing.

An important consideration is that increased proteolysis or an

imbalance of enzyme activity can result in higher contents of hy-

drophobic amino acids and peptides that contribute to bitterness

(Choisey 2000, Law 2001, Azarnia et al. 2006).

Processed Cheese

Processed cheeses are produced by blending and heating several

natural cheeses with emulsifiers, water, butterfat, whey powder

and/or caseinates to form a homogeneous mixture. The pro-

portion of cheese used in the formulation ranges from 51%

for cheese spreads and cheese foods to 98% in processed

cheeses. Different types of natural cheeses will produce pro-

cessed cheeses with different flavor and textural characteristics.

The formulation of these ingredients affects the consistency, tex-

ture, flavor, and melting characteristics of the processed cheese.

The heating process inactivates the microorganisms and dena-

tures enzymes to produce a stable product. The flavor of the

processed cheese is generally milder than the natural cheeses,

due to the effects of the heat. However, the melting properties

of the processed cheese are much improved due to the addition

of the emulsifiers. Processed cheeses range in consistency from

block cheese to sliced cheese to cheese for spreading. (Banks

1998, Fox et al. 2000).

Butter

Flavor and consistency are the most important quality attributes

to consider during the processing of butter. The characteristic

flavor of butter is a result of the formation of diacetyl by het-

erofermentative lactic acid bacteria. Off-flavors due to lipolysis,

oxidation, or other contaminants should be avoided. The but-

ter should be firm enough to hold its shape, yet soft enough to

spread easily. Modification of the cow’s diet to increase contents

of polyunsaturated fatty acids and conjugated linoleic acids in

the milk (Avramis et al. 2003, Bobe et al. 2007) or selecting cows

that produce milk with a higher content of unsaturated fatty acids

(Bobe et al. 2003) results in butter with a softer texture and the

potential for improved cold spreadability due to decrease in the

content of saturated fatty acids. Figure 23.2 outlines the process

involved for making butter and the by-product buttermilk.

The first step in the processing of butter is skimming the milk

to obtain cream with a fat content of at least 35%, in which the

fat is dispersed as droplets within the aqueous phase. This step

increases the efficiency of the process through increasing the

yield of butter, reducing the yield of buttermilk, and reducing

Figure 23.2.Processing scheme for butter processed from ripened

cream.

the size of machinery needed. The pasteurization step functions

to kill microorganisms, to inactivate enzymes, and to make the

butter less susceptible to oxidative degradation. Following pas-

teurization, the cream is inoculated with a starter culture mixture

(1–2%) ofLactococcusssp. andLeuconostocssp., which con-

tributes to the development of the characteristics butter flavor. It

is desirable that the starter cultures grow rapidly at low temper-

atures. During ripening, the cream begins to ferment and the fat

begins to crystallize. The formation of lactic acid and diacetyl

by the starter cultures contributes to flavor development in the

butter and buttermilk. Crystallization of the fat is important to

maximize the yield of the butter and minimize loss of fat into

the buttermilk during the churning process. During the churn-

ing process, air is incorporated into the cream using dashboards

or rotary agitators contributing to the aggregation of fat glob-

ules to form butter granules. The resulting butter grains may be

washed with water to remove nonfat solids followed by work-

ing or kneading the butter grains. During the working step, a