Fermented Dairy Ingredients 337a guide to stop the fermentation. Therefore,
this limitation is used to distinguish yogurt
from other fermented milk products. The
term yogurt is also be used to cover strained
products from thermophilic fermentation of
milk such as yogurt cheese, Greek yogurt,
and other yogurt with cheese - like textures
that retains the acidic characteristics of
yogurt.Yogurt Characteristics
Milk fermentation culminates in a product
with different textures ranging from liquid
such as kefi r and koumis to semi - solid or
solid such as yogurt (Van de Water 2003 ).
Milk fermentation with LAB also results in
products with distinctive tastes and aromas.
LAB metabolism and the interaction between
selected strains produces lactic acid and other
compounds as well as coagulates milk pro-
tein. Fermentation conditions such as tem-
perature, pH, the presence of oxygen, and
milk composition also contribute to the char-
acteristic of the fi nal product (Nakasawa and
Hosono 1992 ).
Certain polysaccharides, called exopoly-
sacharides (EPSs), are also produced by bac-
terial culture such as Str. thermophilus , Lb.
delbruekii subsp. bulgaricus , and other LAB
such as Lc. cremoris and some strains of
Leoconostoc. These polysaccharides contrib-
ute to the texture of the fi nal product by
increasing the viscosity or creating a ropy
texture. Lactic acid gives a slightly tart - like
taste, while acetaldehyde gives green apple
fl avor to yogurt (Cerning 1990 , Nakasawa
and Hosono 1992 , Marshall 1993 ).Yogurt Formulations
As an ancient food from almost every part of
the world, there are many variations in the
way yogurt is made, including the kinds of
milk, cultures, and other added ingredients.
Cow ’ s milk is more commonly used in yogurt
manufacture; however, milk from sheep,East, leben, is mentioned in the Old Testament
as a complaint of the way God treated the
ailing Job (Job 10:10).
The popularity of yogurt has gained new
momentum in the last few decades, as more
and more scientifi c research evidence for its
health benefi ts are reported. In early 1900s,
É lie Metchnikoff proposed that lactic acid
bacteria in fermented milk must have an
antibacterial effect on the putrefying bacteria
of the gut by preventing the breeding of
bacteria that prefer an alkaline environ-
ment. This proposal was based on his obser-
vation that people who consumed yogurt
regularly in his native Balkan regions lived
longer (Metchnikoff 1921 , Van de Water
2003 ). This knowledge of the health benefi ts
of yogurt has helped to increase yogurt con-
sumption. The trend is also enhanced by the
increased palatability of yogurt due to the
addition of sweeteners and fruits (Van de
Water 2003 ).
Yogurt can be defi ned simply as a dairy
product from fermentation of milk. This fer-
mentation produces lactic acid from lactose
that, combined with milk protein, gives
yogurt its characteristic acidic taste and
texture. Yogurt is further defi ned in the
United States as an acidic - gelled product
from culturing of cream, milk, partially skim
milk, or skim milk either alone or in combi-
nation by Str. thermophilus and Lb. del-
brueckii subsp. bulgaricus. Other ingredients
can be added to alter its total solid, taste, and
nutritive values (FDA 2008 ). In Australia,
yogurt is referred to as a fermented milk
product in which lactic - acid - producing
microorganisms are used to ferment the dairy
ingredients and other additional ingredients,
and the microorganisms used must remain
viable in the fi nal product (FSANZ 2007 ).
Yogurt is usually made through fermenta-
tion by thermophilic microorganisms at a
relatively high temperature (slightly higher
than 45 ° C; 113 ° F)(Walstra et al. 2006 ) and a
shorter fermentation time (5 hours or longer),
at which the maximum pH of 4.5 is used as