Spoilage of milk and it's products..pptx

1. By - Deepanshi Dagar MSc. Microbiology (P) Roll no. 04 Spoilage of milk and it’s products

2. Food Spoilage Food spoilage is a metabolic process that causes foods to be undesirable or unacceptable for human consumption due to changes in sensory characteristics(tactile, visual, olfactory or flavour) Burkepile et.al, 2006

3. Importance of understanding food spoilage Waste reduction Economic impact Public Health Environmental Impact Innovation and Research

4. History 1659 – Kircher demonstrated the occurrence of bacteria in milk. 1780 - Scheele identified lactic acid as the principal acid in sour milk. 1839 – Kircher examined slimy beet root and found organisms that formed slime when grown in sucrose solution. 1857 – Pasteur showed that souring of milk was caused by the growth of organism in it.

5. 1873 – The first reported study on the microbial deterioration of eggs was carried out by Gayon. 1878 – Cienkowski reported the first microbiological study of sugar slimes and isolated Leuconostoc mesenteroides from them. 1895 – The first record on the determination of numbers of bacteria in milk were those of Von Geuns in Amsterdam. S.C. Prescott and W. Underwood traced the spoilage of canned corn to improper heat processing for the first time. 1915 – Bacillus coagulans was first isolated from coagulated milk by B.W. Hammer.

6. Signs of food spoilage Foul Odor: Unpleasant or off-putting smells are a clear sign of spoilage. Discoloration : Changes in color can signal spoilage. Look for alterations in the natural color of the food, such as browning, darkening are sign of spoilage.

7. Texture Changes: Spoiled food may exhibit changes in texture, becoming slimy, mushy, or excessively dry. Unusual Taste: Spoiled food can have an unpleasant or off taste.

8. Abnormal Growth: The presence of mold, especially on bread, fruits, or vegetables, indicates spoilage. Gas Production: Fermentation or microbial activity can produce gases, causing packaging to bulge. Canned goods with a bulging or swollen appearance may be spoiled.

9. Factors affecting food spoilage Extrinsic Intrinsic •Nutrient content •pH •Water activity •Antimicrobial constituents •Temperature •Relative humidity •Gaseous atmosphere

10. Types of Food spoilage Non microbial Microbial Physical Spoilage Chemical spoilage

11. Physical Spoilage Physical spoilage is due to physical damage to food during harvesting, processing or distribution and in Transportation. Food spoilage can be caused by physical factors, such as temperature, moisture, dehydration, mechanical damage and pressure acting upon the foods. The damage increases the chance of chemical or microbial spoilage and contamination because the protective outer layer of the food is bruise, crushed or broken and microorganisms can enter the foodstuff more easily.

12. Chemical spoilage Chemical spoilage of food refers to the undesirable changes in the chemical composition of food items, resulting in alterations to their taste, appearance, texture, or nutritional content. Oxidation Enzymatic browning Eg. Phenol oxidase Non enzymatic browning Maillard reaction Caramelization Hydrolytic reactions

13. Microbial Spoilage Microbial food spoilage is the biological process that causes degradation or decomposition of the food item due to microbial growth and activity that brings undesirable changes and makes the food undesirable for consumption.

14. Spoilage of milk and it’s products Dairy products such as milk, butter, cream and cheese are all susceptible to microbial spoilage due to their- • high nutritional composition (lactose, Protein , Fats, citrate and nitrogenous compounds) •high water activity and • moderate pH (6.4-6.6)

15. Spoilage of raw milk Because of the fermentable sugar(lactose) present in milk, an acid formation by bacteria occurs in raw milk. Acid formation cause sour flavor of milk, then coagulation of milk gives solid jellylike curd or a weaker curd that releases clear whey. Lactic acid fermentation takes place in raw milk at room temperature. In raw milk at temperature from 10-37 C, Streptococcus lactis cause the souring, with possibly some growth of coliform bacteria, enterococci, lactobacilli,& micrococci.

16. PSYCHROTROPHIC SPOILAGE Psychrotrophic bacteria which spoil raw and pasteurized milk are primarily aerobic gram-negative rods in the family Psendomonadaceae . It is typical that 65 to 70% of psychrotrophic isolates from raw milk are in the Pseudomonas genus. Although representatives of other genera, including Aeromonas, Listeria, Staphylococcus, Enterococcus , and the family Enterobacteriaceae ,

17. Mechanism of action of Psychrotrophs Proteases production ( P. Fluorescens, P. Fragi and Pseudomonas aeruginosa ) . Lipases production ( Pseudomonas spp. ) Bitter, putrid flavour and coagulation result from proteolysis. Rancid and fruity flavors result from lipolysis. Degradation of casein results in the liberation of bitter peptides. Continued proteolysis results in putrid off flavors associated with lower-molecular weight degradation products such as ammonia, amines, and sulfides.

18. SPOILAGE BY FERMENTATIVE NONSPORE FORMERS They are mostly in either the lactic acid-producing or coliform group. Genera of lactic acid bacteria involved in spoilage of milk and fermented products include Lactococcus, Lactobacillus, Leuconostoc, Enterococcus, Pediococcus, and Streptococcus. Members of the Enterobacter and Klebsiella genera are often spoilage coliforms of concern.

19. Sources contributing to microbes found in milk The Udder interior The teat exterior and it’s immediate surroundings Milking and milk handling equipment.

20. Bacteria get on the outside of teat and may evade the opening and hence the udder interior. Most commonly isolated microbes are micrococci, streptococci and the diptheroid Corynebacterium bovis.

21. The Udder and its immediate environment can be contaminated with microorganism from cow’s general environment. Contamination from bedding and manure can be a source of human pathogens such as E. Coli, Campylobacter, Salmonella and Bacillus spp. may be introduced from soil. C. butyricum and C. Tyrobutyricum may be introduced in milk from silage fed to cows.

22. Milk handling equipment such as teat cups, pipework, milk holders and storage tanks, is the principal source of microorganisms found in raw milk.

23. The defects that occur in milk due to microorganism are: •Off flavors
•Discoloration
•Gas production
•Lactic acid production/ Souring
•Proteolysis
•Lipolysis with development of rancidity
•Sweet curdling

24. Spoilage of butter Butter is a milk product made by the separation of milk and subsequent churning of the cream.
The main source of microorganisms found in butter is cream which is starting material of butter.

25. 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.
Soft and fresh cheeses are spoiled easily due to their higher pH, moisture content, and lower salinity.

26. SPOILAGE CAUSED BY YEAST AND MOLDS The most common yeasts present in dairy products are Kluyveromyces marxianus and Debaryomyces hanseni (the teleomorph) and their asporogenous counterparts (the anamorph), Candida species , and Zygosaccharomnyces microellipsoid es. Also prevalent are Rhodotorula mucilaginosa , Y arrowia lipolytica, Torulospora , and Pichia

27. Microbial succession during spoilage It refers to the sequential and predictable changes in the microbial communities that occur over time as food undergoes deterioration. The process involves various microorganisms succeeding each other, often influenced by factors such as the food matrix, environmental conditions, and the metabolic by-products produced during spoilage.

28. References Doyle MP and Beuchat LR. Food Microbiology: Fundamentals and Frontiers. 3 rd edition. ASM press. Adams MR and Moss MO. Food Microbiology . 2th edition. Royal Society of Chemistry. Jay JM, Loessner MJ, Golden DA. Modern Food Microbiology . 7 th edition. Springer. D.E. Burkepile, J.D. Parker, C.B. Woodson, H.J. Mills, J. Kubanek, P.A. Sobecky and M.E. Hay. Ecol., 2006, 87: 2821–2831.