1. Submitted by
Ramya Selvaraj
III B.SC.,-Microbiology
Department of Microbiology
Vivekananda Arts and Science College for Women
Sankagiri, Salem.
Tamil Nadu, India.
Microbial spoilage of milk and
milk product
Subject:Food Microbiology
2. MICROBIAL SPOILAGE OF MILK
PRODUCT
The loss of quantity of milk and its
product for its consumption due to
the microbial growth or any other
microbial product is known as
microbial spoilage of milk product.
Milk product such as
butter,cheese and yogurt.
3. MICROBIAL SPOILAGE OF MILK AND
MILK PRODUCT
Dairy products such as milk,butter,cream and
cheese are all susceptible to microbial spoilage
due to their
High nutritional composition (protein
,carbohydrate,fats,minerals,lactose sugar,citrate
and nitrogenous compounds)
High water activity and
Moderate ph (6.4-6.6)
Limited self life.
4. Condition of
spoilage
Type of
microorganism
Examples of
microorganisam
During refrigerated storage psychrotrophs Pseudomonas, flavobacterium,
Alcaligenes, Listeria
monocytogenes ,Yersinia
enterocolitica, some coliforms,
and bacillus spp.
After pasteurization Thermoduric microorganisms Enterococcus , Streptococcus ,
some Lactobacillus, and spores
of bacillus and clostridium
Spoilage after the heat treatment Molds and yeasts Aspergillus, Byssochlamys,
Cladosporium , Candida spp.
5. DEFECTS THAT OCCUR IN MILK PRODUCTS
• Off flavor.
• Lipolysis with development of rancidity.
• Gas production.
• Discoloration.
• Fermentation to lactic acid with souring.
• Coagulation of milk protein proteolysis.
6. BUTTER
• INTRODUCTION
• Butter is a diary product made by churning
fresh or fermented cream or milk.
• Butter: water-in-oil emulsion form.
• Consisting of at least 80% fat ,15-17%
water, 0.5 %carbohydrate and protein.
• Butter is a considered as high calorie food
100g of butter provides almost 700 kcal.
• It is extremely rich in minerals like calcium,
phosphorus and potassium.
7. Total plate count 10,000g
Coliform count 10g
E.Coli Absent in 1g
Salmonella Absent in 25g
s.Aureus 10g
Yeast and mould 20g
Spore count Nil
Listeria monocytogenes Absent in 1g
Microbial standards of butter
8. SPOILAGE OF BUTTER
• The main source of microorganisms found in butter in cream which is starting
material of butter. Therefore , the main spoilage caused by Pseudomonas,
Alcaligenes , Acinetobacter , Aeromonas and Achromobacter.
• The primary spoilage organisms in butter are molds such as Thamnidium,
Cladosporium, and Aspergillus.
• The pathogenic microorganisms like Listeria monocytogenes,Brucella,
mycobacterium,Campylobacter,Jejuni,Yersinia enterocolitica and Salmonella
typhimurium.
9. CHEESE
• Cheese is a dairy product produced in wide ranges of
flavors, textures, and forms by coagulation of the milk
protein casein. It comprises proteins and fat from milk
(usually the milk of cows, buffalo, goats, or sheep).
• A coagulant is a substance added to milk to help
solids form out of the liquid portion.
• This is typically an acid like vinegar, or rennet, a
natural enzyme found in the stomach lining of cows.
10. SPOILAGE OF CHEESE
• Cheese is a fermented milk product that is
made by coagulating the casein present in
milk by using the enzyme rennet.
• The ripening in cheese is achieved due to
the proteolytic and lipolytic activities of
various microorganisms.
• The low moisture content of hard and semi-
hard ripened cheeses makes them
susceptible to fungi compared to bacteria.
11. • The bacterial cheese spoilage is caused by Clostridium spp.,
(especially C. pasteurianum, C. butyricum, C. sporogenes, and
C. tyrobutyricum), Bacillus polymyxa, Flavobacterium,
Pseudomonas spp., Alcaligenes, and Achromobacter.
• Yeasts are common cheese spoilage organisms e.g. Candida
spp., Debaryomyces hansenii, Geotrichum candidum, and
Pichia spp.
• The mold spoilage in cheese is caused mainly by Penicillium
spp. and Cladosporium spp.
• Major pathogenic bacteria found in cheese are Listeria
monocytogenes, Salmonella spp., and Escherichia coli
12. YOGURT
yogurt, also spelled yoghurt, yourt, or
yoghourt, semifluid fermented milk food
having a smooth texture and mildly
sour flavour because of its lactic acid
content. Yogurt may be made from the
milk of cows, sheep, goats, or water
buffalo.
13. SPOILAGE OF YOGURT
• Yogurt is a lactic acid fermented milk product that is produced by using symbiotic
cultures of two Lactic acid bacteria (Streptococcus thermophilus and Lb.
delbrueckii subsp. Bulgaricus).
• Fruits and nuts added to yogurt for enhancement of flavor are the main sources of
contamination.
• Molds and yeasts are the primary contaminants in yogurt.
• The most common mold causing yogurt spoilage are Aspergillus, Penicillium,
Rhizopus, Fusarium, and Trichoderma.
14. SPOILAGE OF YOGURT
• The most common yeasts causing yogurt spoilage are Candida spp.,
Debaryomyces, Kluyveromyces, Torulopsis, and Saccharomyces spp.
• They are responsible for off-flavor, gas production, discoloration, etc.
• Molds and yeasts that cause yogurt spoilage leads to a decrease in acidity,
leading to proteolysis and putrefaction by bacteria
• The common food-borne pathogens reported are Escherichia coli,
Staphylococcus aureus, Listeria monocytogenes, and Yersinia enterocolitica.
