Dairy Microbiology

1. Fundamentals of Microbiology                                                                                                                                                                3 (2 + 1)

Microbiology :  history and scope; contributions of Leeuwenhock, Pasteur and Koch. Principal of microbiology : Light Microscopy (Bright field, dark field, phase contrast, fluorescence); preparation and staining of specimens : electron microscopy. Microbial taxonomy : principles; numerical taxonomy ; major characteristics used in taxonomy; classification according to Bergey’s manual of systematic bacteriology. Structure and functions of prokaryotic cells; difference between prokaryotes and eukaryotes. Microbial growth and nutrition : the growth curve ; factors affecting growth of microorganisms, estimation of bacterial growth; bacteriostatic and bactericidal agents; the common nutrient requirements and nutritional types of microorganisms. Bacterial  genetics; DNA as the genetic material ; structure of DNA; bacterial mutations (spontaneous and induced); genetic recombination – (transformation, transduction, conjugation). Micro flora of air, soil and water methods for controlling microorganisms in air; water as carrier of pathogens.


Practical :   General instruction for microbiological laboratory. Microscope- simple and compound ; Microbiological equipments; autoclave, hot air oven, incubator, centrifuge, colorimeter, laminar airflow, membrane filter, Simple staining methylene blue; crystal violate; negative staining. Differential staining (Gram spore, acid fast). Mortality of microorganisms; hanging drop technique. Measurement of microorganisms by micrometry. Preparation of commonly used growth media liquid and solid: simple and differential media. Isolation technique for microorganisms-Streak & pour plate Enumeration of microorganisms in air and soil. Enumeration of microorganisms in water : Total viable count, coliform (MPN).


2. Introductory Dairy Microbiology                                                                                                                                                        3 (2 + 1)

Hygienic milk production system; microbial quality of milk producted under organized v/s unorganized milk sector in India and comparison with developed countries; microbial and non microbial contaminants, their sources and entry points in milk during various stages of production; Good Hygiene Practices (FHP) during milk production operations Microorganisms associated with raw milk; morphological and biochemical characteristics of important groups and their classification; significance of different groups of bacteria i.e. psychrotrophs, mesophiles, thermodurics, and thermophiles in milk; Microbiological changes in bulk refrigerated raw milk; impact of various stages like milking, chilling, storage and transportation on microbial quality of milk with special reference to psychrotrophic organisms;  Direct and indirect rapid technique for assessment of microbial quality of milk. Role of microorganisms in spoilage of milk; souring, curdling, bitty cream, proteolysis, lipolysis; abnormal flavours and discoloration. Mastitis milk : Processing and public health significance, organisms causing mastitis, somatic cells secreted in milk as a vehicle of pathogens; food infection, intoxication and toxic infection caused by milk borne pathogens like E.Coli. Salmonella Typhi, Staph aureus cereus etc. Antimicrobial substances in milk: immunoglobulin. Lactoferin, lysozymes, LP systems etc.


Practical :   Morphological examination of common dairy organism (size and shape, arrangement and sporulation). Enumeration of psychrotophic, thermophilic, thermoduric and spore forming bacteria in milk. Detection of sources of contamination : air, water, utensils, equipment and personnel line testing. Spoilage of milk caused by microorganisms souring, sweet curdling, gassiness, lipolysis, ropiness, proteolysis and discoloration. Detection of mastitis milks, pH, SLST, somatic cell count chloride content, Hotis test, CAMP test. Detection and estimation of coliforms; presumptive test, rapid coliform count, IMVIC test. Detection of important pathogens using selective media; E.coli, Staphylococcus aureus Salmonella and Bacillus cereus. Estimation of microbiology load in milk by SPC and DYE reduction tests- (MBRT,RRT). Detection of antibiotic residues using qualitative test.


3. Food and Industrial Microbiology                                                                                                                                          3 (2 + 1)

Food Microbiology :  Basic aspects and scope of food microbiology. Intrinsic and extrinsic factors that affect microbial growth in foofs. Microbial spoilage of fruits, fruit juices, vegetables, cereals, meat, poultry, sea foods, carbonated soft drinks, canned foods; control of spoilage. Food preservation : physical methods; chemical preservatives and natural antimicrobial compounds, biology based preservation system. Industrial Microbiology : Fermentation processes: the range, components and types (submerged, Surface and solid state fermentation): criteria for selection of industrially important microorganisms; media for industrial and inoculums development; down stream processing of fermented products. Fermenters: types, functions, design and control; chemostat and turbidostat. Microorganism and processes involved in the production of industrial alcohol, organic acids (citric lactic). Enzymes (protease, lipase and rennet), vitamin (B-12), antibiotic (nisin) and microbiology of effluent treatment in food industry.


Practical :    Microbiological examination of fresh and canned fruits/vegetables/juices; flour and bread, eggs and meat. Design and control of a tabletop and 10 liter lab fermenter (Demonstration). Isolation of psychrophile, salt and sugar tolerant microorganisms from foods, Isolation of industrially important microorganisms from environment. Production and ….. of microbial enzymes (protease/tipase). Production of lactic acid from whey. Production of nisin and assaying the antimicrobial activity of the culture. Production of ethyl alcohol from molasses and whey by yeasts. Production of fermented whey beverages. Educational tour to food processing/fermentation industries.


4. Starter Cultures and Fermentated Milk Products                                                                                                                     3 (2 + 1)

Introduction of starter cultures & their importance in dairy industry, classification of Lactic Acid Bacteria; Metabolism of Lactic Acid Bacteria and diacetyl production, production of antibacterial substances by lactic starter cultures. Mixed  and define strain starter culture; propagation of starter cultures; factors affecting their propagation;starter concentrates- direct bulk and direct vat starter cultures; starter distillates. Quality and activity of starter cultures; defects in starters  and their control; starter failures; antibiotic residues, sanitizers and bacteriophages. Preservation of starter cultures; freezing and freeze-drying; factors affecting the survival of cultures during preservation. Role of starter cultures in the preparation of various fermented milks; classification of fermented  milks microbiology of dahi and yoghurt; different types of dahi and yoghurt; preparation; defects and their control, Microbiology of milk products; their nutritional and therapeutic significance. Kefir and Kumiss: origin and characteristics: microbiology of Kefir grains. Microbiology of other fermented milks such as Bugarian milk, cultured buttermilk, Leben and Yakult; their significance. Concept of probiotic starters and their application in probiotic dairy food.


Practical :    testing for purity of starter cultures; gram’s staining, catalase test; creatine test. Starter activity tests: die reduction tests, Horrall-Elliker test, Whitehead and Cox test. Preparation of single and mixed starter cultures: homofermentation and hetrofermentation separately and also in combinations. Maintenance and preservation of starter cultures- Freeze drying techniques demonstration. Preparation of concentrated starter – Freeze dried and frozen types. Effect of physical factors on dairy starter: temperature, pH salt, sugar. Testing milk for the presence if inhibitory substance using B. Stearothermophilus and S. Thermophilusas indicator organisms. Effect of antibiotic residues in milk on starter activity. Associative growth of microorganisms in milk and cream. Detection of bacteriophages in cheese whey by plaque assay. Preparation and evaluation of quality and grading of Dahi, Yoghurt, cultured butter milks, acidophilus milk and Kumiss. Microbiological analysis of processed cheese- Total spore count & Anaerobic spore count. Microbiological analysis at different stages of manufacture of (storage and ripening) hard verities of cheese- such as Cheddar cheese.


5. Dairy Biotechnology                                                                                                                                                                                    3 (2 + 1)

Definition, scope and historical development of biotechnology, achievement and future application: structure of DNA and RNA; DNA replication, protein synthesis, genetic code, mutations: Vectors, cloning strategies in bacteria and animals, DNA technology. Protoplast fusion & Tissue culture in dairy cultures. Application of biotechnology in food and dairy industry, dairy effluents. Genetic manipulation of dairy starters for improved attributes of commercial value. Dairy enzymes and whole cell immobilization. Ethical issues related to use of genetically modified foods.


Practical :   Isolation of plasmid and genomic DNA from bacteria (E.coil,  lactic acid bacteria Agarose gel electrophoresis of DNA fragments). Restriction analysis of DNA. Curing of plasmids. Preparation of competent cell. Conjugal transfer in E.coli cells. Transformation of E.coli by calcium chloride treatment/electro oration. Preparation of protoplasts and protoplast fusion. PCR technique demonstration. Vist to a biotechnology lab.


6. Quality and Safety Monitoring in Dairy Industry                                                                                                                       3 (2 + 1)

Current awareness on quality and safety of dairy foods: consumer awareness and their demands for safe foods; role of codex alimentarious  commission (CAC) in harmonization of international standards; quality (ISO 9001 : 2000) and food safety (HACCP) system and their application during milk production and processing. National and international food regulatory standards; BIS, PFA, ICMSF, IDF etc., their role in the formulation of standards for controlling the quality and safety of dairy foods. Rapid assessment of dairy food for microbial and non-microbial contaminants: Enumeration Principles in detection of predominant spoilage organisms and pathogens like indicator organisms, E.coli, salmonella, shigella, staph aureus, Bacillus cereus  and non microbial contaminants like antibiotic residues, aflatoxin, pesticides other inhibitors etc from. Dairy foods and their control measures. Microbial quality of water and environmental hygiene in dairy plant; dhlorination of dairy water supply, quality of air. Personnel hygiene, treatment and disposal of waste water and effluents; setting up of microbiological/ pathogen lab in a dairy plant and its safety concern.

Practical :   Evaluation of common sanitizing agents used in dairy plants by (a) suspension (b) capacity test. Microbiological tests for assessing equipment and personnel hygiene by swap and rinse methods. Detection of faecal and non-faecal coliforms and faecal streptococci in dairy plant. Detection and enumeration of different pathogenic bacteria in dairy products : Staphylococus aureus, Bacillus cereus, Salmonella and Shigella.  Bacteriological analysis of dairy water for : (a) total viable counts (b) coliform counts (MPN). Detection of antibiotic residues, pesticides, aflatoxins and staphylococcal enterotoxins in milk using rapid techniques. Determination of BOD in dairy waste water. Quality evaluation by HACCP in the preparation of dairy products.