Dairy Ingredients in Dairy Food Processing 449(39 ° F) as the yogurt mass is pumped through
a heat exchanger. A texturizing cone is
inserted in the pipe leading to the heat
exchanger to smoothen the texture.
Manufacturing Procedures
Plain Yogurt. Plain yogurt is the basic yogurt
style, and it forms an integral component of
fruit - fl avored yogurt. The steps involved in
the manufacturing of set - type plain yogurt
are shown in Figure 17.5. Plain yogurt nor-
mally contains no added sugar or fl avors. It
has a natural yogurt fl avor for consumption
as such or it can be fl avored with other ingre-
dients of the consumer ’ s choice. In addition,
it may be used for cooking or for salad prepa-
ration with fresh fruits or grated vegetables.
In most recipes, plain yogurt is a sour cream
substitute that provides fewer calories and a
fat alternative.
Fruit - fl avored yogurt. In addition to
plain yogurt, Figure 17.5 also illustrates a
manufacturing outline for fruit - on - the -
bottom style yogurt, which includes the use
of two - stage fi llers. Typically, 59 ml (2 oz) of
special fruit preparation is layered at the
bottom of the cup, followed by 177 ml (6 oz.)
of inoculated yogurt mix on the top. The top
layer may consist of unfermented yogurt mix
containing stabilizers, sweeteners, and the
fl avor and color indicative of the fruit on the
bottom. After placing lids on the cups, incu-
bation and setting of the yogurt takes place
in the cups. When a desirable pH of 4.4 to
4.5 is attained, the cups are placed in refriger-
ated rooms with high - velocity forced air for
rapid cooling.
Stirred style yogurt or blended yogurt is
produced by blending the fruit preparation
thoroughly in fermented yogurt base obtained
after bulk culturing in fermentation tanks.
Figure 17.6 illustrates the process fl ow.
Stabilizers, especially gelatin, are com-
monly used in this form of yogurt unless
MSNF levels are relatively high (12% to
14%). In this style, cups are fi lled with an
in - line blended mixture of yogurt and fruit.
Several variations of this procedure exist in
the industry. Fruit incorporation is conve-
niently effected by the use of a fruit feeder at
the 8% to 15% level.
Aerated yogurt. Aerated yogurt resem-
bles mousse in that the product acquires a
novel foam - like texture. The aeration process
is similar to the ice cream process, but the
degree of overrun (extent of air content) is
kept relatively low, 20% to 50%. Foam for-
mation is facilitated by use of appropriate
emulsifi ers and the stability of foam is
achieved by using gelatin in the formulation.
After fermentation and cooling, aerated
yogurt is produced with appropriate equip-
ment (Oakes, Tanis, or Mondo), injecting a
controlled volume of an inert gas (nitrogen)
to create foam in the product. Nitrogen helps
to control fat oxidative issues in the product.
The amount of overrun is related to textural
and mouth feel attributes of the product and
is determined by the desired marketing
requirements. In aerated yogurt, it is desir-
able to measure overrun to ensure uniformity
of texture from day to day. The volume of
yogurt in the cup also is related to the degree
of overrun. Accordingly, overrun control
ensures the correct weight of the product in
the cup.
Yogurt - based salad dressings. Yogurt -
based salad dressings contain salt, spices, and
herbs such as dried onion, garlic, and parsley.
Some yogurt dressings may contain honey,
Dijon mustard, and celery seed. Yogurt dips
may also contain onion, clam, cheddar, and
blue cheese, depending on the product
concept.
Heat - treated yogurt. The shelf life of
yogurt may be extended by heating the yogurt
after culturing to inactivate the culture and
the constituent enzymes. Heating to 60 ° C
to 65 ° C (140 ° F to 149 ° F) extends the shelf
life to about 12 weeks at 12 ° C (54 ° F). UHT
treatment and aseptic packaging ensures
a shelf life that is even longer, even at
room storage temperature. However, these