Spoilage of egg, raw milk

and milk products

By

Assoc.Prof.Dr.Narumol Matan

Structure of egg

Intrinsic parameters

1. Waxy shell membrane

2. Shell

3. Inner shell membrane

4. Lysozyme of egg white: ability to hydrolyze a polysaccharide in the cell wall of some bacteria to prevent bacterial spoilage

5. Egg white contains avidin, which forms a complex with biotin, thereby making this vitamin unavailable to microorganisms. In addition, egg white has a high pH (about 9.3) and contains conalbumin, which forms a complex with iron, thus rendering it unavailable to microorganisms.

Avidin-biotin

6. Hen egg albumen contains ovotransferrin, which chelates metal ions, particularly Fe3+, and ovoflavoprotein, which binds riboflavin. At its normal pH of 9.0 to 10.0, egg albumen is cidal to gram-positive bacteria and yeasts.

Nutrition Nutrition Total weight White egg Yolk egg Cook egg

weight 50 33 17 50

protein 6.45 3.6 2.72 6.45

Fat-total lipid 5.75 - 5.75 5.75

CHO 0.36 0.26 0.1 0.36

Ca 27 2.97 23.97 27.0

Vit A 102.5 4.95 96.73 102.5

Bacterial spoilage of eggs

1. Green rots caused by Pseudomonas spp.,

P. fluorescens

2. Colorless rots caused by Pseudomonas, Acinetobacter

3. Black rots caused by Proteus, Pseudomonas, Aeromonas

4. Pink rots caused by Pseudomonas

5. Red rots caused by Serratia spp.

6. Custard rots caused by Proteus vulgaris, P. intermedium

7. Rotting caused by normal flora

8. Pinspots caused by Penicillium, Cladosporium spp.

Salmonella and eggs?

Salmonella enteritidis

Prevention • Chilling

• Remove dirt from the eggs.

• Wash hands that handle raw eggs before cooking.

• Do not store eggs in room temperature before cooking for 2 hours.

• Do not keep too much food in the refrigerator.

• Do not eat ice cream made from raw eggs.

Changes in egg quality during storage

• Low moisture protect (storage T=(-1.7 to 0.55 .C)

• The size of the air cell increases.

• The yolk enlarges.

• The membrane weakens.

• The egg white becomes thinner.

• The egg becomes more alkaline.

• The odor and flavor of the egg deteriorate.

• The pH of egg rises due to loss of CO2 from the egg.

• Microbial growth.

Spoilage of raw milk and milk products

1. Microorganism in raw milk

2. Microorganism in process milk

3. Microorganism in finish product milk

Nutrition %Total %Average

water 82-90 87.3

fat 2.3-7.8 3.67

protein 2-4.5 3.42

lactose 3.5-6.0 4.78

mineral 0.6-0.9 0.73

solid 10-18 12.69

NSF 7.5-10.6 8.77

1. Contamination of raw milk

• 1. Udder

• 2. Human

• 3. Water and Weather

• 4. OX (Mycobacterium, Brucella sp, Streptococcus scarlatinae, Coxilella burnetti )

• 5. Equipment

• 6. Insect

• 7. Intredients such as sugar salt

Storage of raw milk

Microorganism in raw milk

– acid Streptococcus lactis, Micrococcus, Lactobacillus.

– Gas H2, CO2 Heterofurmentative

– proteolysis (acid or acid and alkali)

– sweet curd rannin enz. Rennin precipitation B. cereus, proteus

– Ropiness Enterobacter, Alcaligeues, Viscolactis.

– Lipid change lipase enz. Pseudomonas, Proteus, Alcaligenes, Bacillus, Clostridium.

– Alkaline production Pseudomonas, Aluorescenus, Alcaligenes.

– Flavor change

• Sour flavor Streptococcus lactis

• Bitter flavor Micrococcus, Pseudomonas

• Brunt or caramel flavor

• Color change – blue Pseudomonas syncyanea.

– Yellow P. synxantha.

– Red Serratia.

– Blown P. pntrefaciens.

2. Microorganism in process milk

Pasturization

• 2.1.1 LTLT ( Low Temperature Long Time ) 60 .C 30 min.

• 2.1.2 HTST ( High Temperature Short Time ) 72 .C 15 Sec-1

• 2.1.3 HHST (Higher Heat Shorter-Time) Or UHT 130-150 .C 2-8 Sec-1

• * Random simple in line sample

Resistant of Microbiology Heating • 2.2.1 Bacterial

– Cocci > Rod, Themophile > Simple bact.

– Capsule > no capsole, Spore > No spore

– Clostridium botulinum

– Bacillus stearothermophilus

– Clostridium sporogenes

• 2.2.2 Fungi

– Asexal spores > Mycelium

– Wet heat > Dry heat

• 2.2.3 Yeast

– Ascospores > Cell

3. Microorganism in finish product milk

Random sample (Finished Product)

• Grade of milk

– Grade raw milk pasturization milk

– SPC SPC Colifrom

– A 200,000 30,000 10

– B 1,000,000 50,000 10

– C no limit no limit no limit

Spoilage of Cheese

1. Lactic acid bacteria case gas such as L. casei, L. brevis (May be pink)

2. Coliform bacteria; if contaminated, this will cause the cheese bag to swell.

3. Yeast and molds such as Candida parapsilosis, Penicillium roqureforti

Spoilage of Canned condensed milk

• Low water activity because it is a very sweet product. Therefore, can be found spore-forming such as Bacillus stearothermophilus, B.cereus