Food technology is a branch of food science that addresses the production, preservation, quality control and research and development of food products. Bakery at the Faculty of Food Technology, Latvia University of Life Sciences and Technologies The food technology room at Marling School in Stroud,

1. MISS: SALSABEEL H. AL JOUJOU

2. Objectives -
:
Be able to produce of yoghurt using Lactobacillus
delbrueckii and Streptococcus thermophilus.

3. I. Introduction:-
 Yoghurt or yogurt is a dairy product produced by
the controlled fermentation of milk by two species
of bacteria (Lactobacillus sp. and Streptococcus
sp.).
 The sugar in milk (called lactose) is fermented to
(lactic acid) and it is this that causes the
characteristic curd to form.

4. I.1 Yogurt Types:
1. Set yogurt: A solid set where the yogurt firms in a
container and not disturbed.
2. Stirred yogurt: Yogurt made in a large container
then spooned or otherwise dispensed into secondary
serving containers.
The consistency of the “set” is broken and the texture
is less firm than set yogurt. This is the most popular
form of commercial yogurt.

5. 3. Drinking yogurt: Stirred yogurt to which additional milk
and flavors are mixed in. Add fruit or fruit syrups to
taste.
 Mix in milk to achieve the desired thickness. The shelf
life of this product is 4-10 days, since the pH is raised by
fresh milk addition.
 Some whey separation will occur and is natural.
Commercial products recommend a thorough shaking
before consumption.

6. 4. Fruit yogurt: Fruit, fruit syrups, or pie filling can be
added to the yogurt. They are placed on top, on bottom,
or stirred into the yogurt
I.2 Health benefit of yogurt
1. Yogurt is easier to digest than milk.
2. Yogurt contributes to colon health.
3. Yogurt remains an excellent source of calcium.
4. Yogurt can boost immunity.
5. Yogurt .
6. Yogurt can lower LDL ,Raise HDL cholesterol.

7. II. Method of processing:
II.1 Yoghurt
There are two types of plain (unflavored) yoghurt that
are produced under control conditions.
These are set that yoghurt that has a firm crud and
stirred yoghurt that has a smooth creamy consistency,
similar to a thick cream.
The production method is:

8. 1. Heat milk in a stainless steel (or less desirably an
aluminum) pan to 80- 85 ºC for 15- 20 min. with
constant stirring.
2. Cool 40- 45 ºC as quickly as possible and add a
starter culture (or inoculum) of the mixed lactic acid
bacteria.
3. Depending on the yoghurt required, the milk is
either kept in pan (for stirred yoghurt) or filled into
individual retail pots (for set yoghurt).

9. 4. Incubate the milk at 40- 45 ºC for 4- 6 hrs to
allow the fermentation to take place.
5. For stirring yoghurt, the pan of the crude is then
stirring using a sterilized spoon or ladle until the
crude becomes a smooth cream that has a thick
consistency without any lumps.
6. Both types of yoghurt are stored in a refrigerator
at 4- 8 ºC.

10. II.2 Flavoured or fruit yoghurt
Flavoured or fruit yoghurt is produced the same as plain
yoghurt. For flavoured yoghurt, the essence (e.g, vanilla,
chocolate or fruit flavour) with or without coloring, is added
befor the milk is fermented.
Yoghurt that contains fruit pulp is made in the similar way
to plain yoghurt and the fruit pulp is added after
fermentation. Less acidic fruits such as melons or pawpaw
(papaya) are more successful because they don’t react with
the milk.
Acidic fruits (lemons, lime, pineapple, etc.) may cause
excessive curdling and separation of the yoghurt.

11. II.2.1 To make fruit pulp
1.Select fully rip fruit.
2.Wash in clean water.
3.Remove the peel and seed.
4.Pulp the fruit.
5.Heat the pulp for 15- 20 min. at 70- 80 ºC in stainless
steel pan, with constant stirring to prevent it burning in to
the pan.

12. This softens the fruit and destroys any contaminating
microorganisms and naturally occurring enzymes that
would cause changes to the color or flavour of the fruit
during the storage.
6.Cool to room temperature.
7.Either mix the pulp into stirred yoghurt (e.g. one part
pulp between three to five parts yoghurt) or place a
layer of pulp at the bottom of pots before filling stirred
yoghurt.
8.Store as for plain yoghurt