Manufacturing of yogurt is an ancient technique, which dates
back to thousands of years, and the knowledge has transferred
generation to generation. However, during the last few decades,
it became more rational due to improvement of various fields
such as microbiology, biochemistry and food engineering. Today
it is a complex activity combined with art and science[5]. The
generalized process of yogurt making is comprised of modifying
the original composition of milk, pasteurizing the yogurt mix,
fermentation at thermophilic temperatures (40-45 ºC), cooling
and addition of fruits and flavors. The production steps in
manufacture of stirred- and set yogurt are illustrated in the Figure
1.
Ingredients for yogurt manufacture
Yogurt is made with a variety of ingredients including milk,
sweeteners, stabilizers, fruits, flavors, and bacterial cultures.
Milk is the main ingredient used in yogurt manufacturing. The
type of milk to be used depends on the variety or type of the
yogurt that will be prepared. For instance, whole milk is used for
full fat/regular yogurt, partially skimmed milk is used for low fat
yogurt and skimmed milk is used for nonfat yogurt. Cream/butter
fat is used to adjust the fat content whereas skim milk powder,
whey protein concentrate are used to elevate the total solid
content of the yogurt mix. Stabilizers are usually added to the
mix in order to increase the body and texture leading to an
increase in firmness, prevents whey separation/syneresis, and
aids in uniform distribution of ingredients. In addition,
sweeteners are added to increase the flavor and consumer appeal.