This document provides information on fermented milk and cheese production. It discusses the different types of fermentation used to produce milk products like yogurt, the starter cultures used, and characteristics of good yogurt. The document also covers the processing procedures for making cultured butter milk and considerations for raw milk quality in fermented milk production. Cheese production is introduced, including definitions of ripened and unripened cheese. The general cheese making process and steps in cheese milk preparations are summarized.

1. Kamau S M
Lecturer: Dairy Training institute
Fermented Milk and Cheese
Production

2. Fermented milk products
 Milk Products be made by mesophilic or
thermophilic fermentation.
 Mesophilic fermentation uses starter cultures
(fermentation microorganisms) that have optimum
growth temperature of 30oC and they have a
growth temperature range of 20 - 40oC. The
incubation is usually for 14–16 h or until a pH of
5.0 is achieved.
 Thermophilic starter cultures grow from 30 to 46
°C for 8–10 hours; With a final pH of 4.7

3. What is fermentation?
 Fermentation is a bio chemical breakdown of a
substance usually sugars by bacteria, yeasts, or
other microorganisms
 Fermentation usually results in various products
such as organic acids (lactic acid, butyric acid,
etc.), alcohols (ethyl alcohol, butyl alcohol, etc.)
and gases (hydrogen, carbon hydroxide, etc.).

4. Dairy starter cultures
 Dairy starter cultures are harmless, specially
selected microorganisms of known and stable
metabolic activities that are inoculated into milk to
produce fermented products of desirable
characteristics (appearance, body, texture and
flavor).
 When inoculated in milk they convert the milk
sugar, lactose, into lactic acid for curd formation
and other by products responsible for flavour,
aroma and consistency development.

5. Producer Country Website
Christian and Hansen Denmark http://www.chr-hansen.com
Danisco Denmark http://danisco.com
DSM The Netherlands http://www.dsm.com
Alce Italy http://www.mofi nalce.it
Centro Sperimenti del
Latte
Italy http://www.csl.it
Valio Finland http://www.valio.fi
BioSource Flavors, Inc. United States http://www.biosourcefl
avors.com
CSK Food Enrichment The Netherlands http://www.cskfood.com
BIOPROX France http://www.bioprox.com

6. Yoghurt
 This is the most ppopular fermented milk product
made using thermophilic starter culture, it has
mild acidic taste, rich in aromatic diacetyl flavor
and has a smooth viscous texture.

7. Classification of yoghurt
 Chemical composition - they are classified as
full-fat, reduced-fat or low-fat, fruit yoghurt
 Method of production- they can be grouped as
set, stirred, drinking
 Flavor type- can be classified into subgroups
such as Plain/natural yogurt, flavoured yoghurt
(strawberry, vanilla etc)
 Post-incubation process - can be grouped as
concentrated, dried, and frozen, long life
 Textural characteristics – can be grouped as
thick yoghurt, thin ,smooth

8. Cultured butter milk (mala)
 Milk product made using mesophilic starter
cultures, it has mild acidic taste with an aromatic
diacetyl flavor and a smooth viscous texture. In
Kenya its popularly known as maziwa lala (mala
for KCC)

9. Processing of fermented
products
 Processing of fermented milk involves heat
treatment of milk, inoculation with starter cultures
and incubation to achieve the desired
characteristic of body, texture and flavour of the
fermented milk product.
 The fermented milk must be cooled immediately
after attaining the required acidity to stop the
fermentation process (further acid development).

10. Raw milk quality for fermented
milk production
 Physical dirt - Should be clean, if not sieve or clarify
 Antibiotics – antibiotics prevent growth of bacteria in the
starter culture
 Colostrum - the high amount of whey proteins causes
wheying off resulting in thin watery product. They also act
as natural inhibitors in milk.
 Mastitis - low sugar (lactose) in mastitis milk does not
allow production of enough lactic acid resulting in a flat
tasting product
 Water - added water prevents formation of a firm
coagulum.
 Chemicals- e.g. detergents, sanitizers, preservatives,
which are injurious to the consumer or will prevent growth
of bacterial culture.
 Microbial: - should be low in initial microbial load. Some
microorganism’s produce bacteriocins which might prevent
fermentation or be in competition with the starter culture

11. Additives and ingredients
 Other dairy products: SMP, Whey powder,
Lactose
 Sugar /Sweeteners
 Flavours (fruits, natural flavors and/or synthetic
flavors)
 Colours
 Stabilizers (gelatin, pectin)
 Thickeners (Corn starch, SMP)

12. Average amounts of ingredients
added in yoghurt making
 Sugar 4.0 -6.0%
 Skim milk powder 1.0 – 3.0%
 Starch ( Corn flour) 0.5 – 1.0%
 Pectin/gelatin 0.1 to 0.5%
 Food colour According to
consumer preference

13. YOGHURT MAKING PROCEDURES
SET YOGHURT STIRRED/DRINKING YOGHURT
 High quality milk.
 Filter.
 Standardize (optional).
 Optional enrichment with Skim Milk Powder, max. 3%, Sugar, max 6%,
Stabilizer e.g. gelatin, colour.
 Pasteurize 850
C/30 min. or 900
C/15 min.
 Cool to inoculation temperature 38 – 450
C (optimum 420
C)
Optional additional of
flavour
Additional of starter
culture
Incubation till
coagulation (3 – 6hrs )
Additional of starter
culture
Cooling to 4 0
C
overnight
Packaging into
individual cups
Stir, optional addition
of flavour, fruits, nuts
Incubation till
coagulation 3 – 6 hrs
Cooling to 4 0
C
overnight Whipped / Stirred
/Drinking Yoghurt
Set/ Firm/ Eating
Yoghurt

14. CHARACRTERISTIC OF GOOD YOGHURT
 Appearance Smooth, porcelain-like, no whey
separation
 Colour Natural milk colour or Colour of the
corresponding flavouring
 Odour Characteristic sourish, clean and aromatic or
typical for the used flavouring
 Taste Typical, characteristic, full, pleasant, mild to
slightly acidic and sweet if sweetened
 Consistency Gelatinous, viscous, slightly ropy, no
bubbles, no lumps, no separated whey

15. Processing Procedure Cultured
Butter Milk (Mala)
 High quality milk required
 Standardization
 Milk is usually heated to 85 °C for 30 minutes or
90 °C for 15 minutes
 Cool to 20-25 °C (room temperature)
 Addition of mesophilic starter culture.
 Incubation 14-16 hours, to an acidity of 0.7%
lactic acid.
 Packaging

16. Defect. Probable cause(s)
1) Wheying off
Over incubation
Too high incubation temps.
Contamination with unwanted microorganisms
2) Grainy / curdy/ small lumps
Over incubation
Too high incubation temps.
Contamination
3) High acid development
Over incubation
Too high incubation temps.
Contamination
4) Thin or low viscosity
Low total solids
Over stirring
Disturbing during setting
5) Flat taste/no acid development
Weak starter culture
Milk with preservatives/antibiotics
Little sugar in milk (as for mastitis milk)
6) No fermentation
Dead starter culture
Milk with preservatives/antibiotics
7) Mouldy or Yeasty flavour
Air in the coagulum/gassy
Sugar not pasteurized introducing yeast contamination
Over exposure to the environment leading to
contamination
and high storage temps
8) Bitter
Breakdown of proteins due to molds or
to molds or bacterial contamination

17. Cheese
 Cheese is the fresh or matured solid or semi-solid
product obtained by coagulating whole milk, skim
milk, cream, whey cream, or buttermilk or any
combinations of these materials through action of
rennet, or other coagulating agents and by
partially draining the whey resulting from such
coagulation (FAO/WHO; 1978.)

18. Ripened cheese
 Cured or Ripened cheese is cheese which is not
ready for consumption shortly after manufacture
but which must be held for such time at such
temperature and such other conditions as will
result in the necessary biochemical and physical
changes characterizing the cheese. E.g. Gouda,
cheddar

19. Un-ripened cheese
 Uncured, Unripened or Fresh cheese is cheese
which is ready for consumption shortly after
manufacture E.g. Mozarrella, cottage

20. Reasons for cheese making
 Value addition of milk
 Utilization of excess milk
 Increasing nutritional value per unit volume
 Increasing shelf life of milk
 Improving digestibility of milk

21. GENERAL CHEESE MAKING
OPERATIONS
 The cheese making process involves a set of
organized and well coordinated steps known as a
Recipe. It details the order, timing and limits of
each operation.
 The recipe is specific to the cheese type

22. CHEESE MILK PREPARATIONS
AND PRE-TREATMENTS
 Filtration and clarification
 Butterfat standardization
 Pasteurization
 Thermization