In addition to being a nutritious food for humans, milk provides a favorable environment for the growth of microorganisms.
Microbes can enter milk via the cow, air, feedstuffs, milk handling equipment and the milker. Once microorganisms get into the milk their numbers increase rapidly. It is more effective to exclude microorganisms than to try to control microbial growth once they have entered the milk. Milking equipment should be washed thoroughly before and after use rinsing is not enough. Bacterial types commonly associated with milk are given in Table 3.
Microbial growth can be controlled by cooling the milk. Most microorganisms reproduce slowly in colder environments.
Cooling milk also slows chemical deterioration. Bacteria multiply very rapidly in warm milk and milk sours rapidly if held at these temperatures. At this temperature bacterial growth will be reduced and enzyme activity retarded. Thus, milk will keep longer if cooled. Natural souring of milk may be advantageous: for example, in smallholder butter-making, the acid developed assists in the extraction of fat during churning.
The low pH retards growth of lipolytic and proteolytic bacteria and therefore protects the fat and protein in the milk. The acidity of the milk also inhibits the growth of pathogens. It does not, however, retard the growth of molds.
Naturally soured milk is used to make many products, e.
These products provide ways of preserving milk and are also pleasant to consume. They are produced by the action of fermentative bacteria on lactose and are more readily digested than fresh milk.
The initial microflora of raw milk reflects directly microbial contamination during production. The microflora in milk when it leaves the farm is determined by the temperature to which it has been cooled and the temperature at which it has been stored. Rapid tests are available for estimating the bacterial quality of milk.
Pasteurisation is the process used to destroy bacteria in milk. In pasteurisation, the milk is heated to a temperature sufficient to kill pathogenic bacteria, but well below its boiling point.The Milk Microbiology section contains information relating to microbial concerns in milk.
A brief overview of dairy microbiology is presented below as an introduction this section. The topics covered are:. Milk is virtually sterile when it is synthesized in a healthy cow's udder mammary gland. Cows, like humans, are natural reservoirs of bacteria. Many of these bacteria are not harmful to humans, but some may be harmful to humans even though the cows are not affected and appear healthy.
Milk may become contaminated with bacteria during or after milking. The mammary glands of cows and humans can become inflamed due to a bacterial infection called mastitis. During a mastitis infection, very high numbers of bacteria present can be in the udder and in the milk. Some disease causing organisms pathogens can be shed through cow feces and may contaminate the outside of the udder and teats, the farm environment bedding, for example and the milking equipment.
Although optimal growth conditions for bacteria are different for different organisms, milk contains important nutritional components for mammal growth, and, therefore, it is also an ideal medium for the growth of many different bacteria.
Temperature plays an important role in bacterial growth. The area of dairy microbiology is large and diverse. The bacteria present in dairy products may cause disease or spoilage. Some bacteria may be specifically added to milk for fermentation to produce products like yogurt and cheese.
A detailed discussion of fermentation bacteria is outside the scope of this web site, although these organisms are discussed briefly in the section on yogurt production and cheese production. This section of the web site is dedicated to the discussion of pathogens because of their importance in human health. Human illness from milkborne pathogens is usually associated with consumption of raw milk or products made from raw milk such as fresh cheeses.
In the past 20 years, foodborne illnesses from dairy product consumption have been predominantly associated with Salmonella entericaListeria monocytogenesCampylobacter jejuniand Escherichia coli OH7. These organisms have been isolated from bulk tank samples at rates ranging from 0. Because there is a risk of pathogen contamination in milk produced from healthy cows under sanitary milk conditions, pasteurization of milk prior to consumption will destroy pathogens and provide protection for illness associated with consumption of dangerous microbes.
Occasionally, human illness has been linked to pasteurized milk products but these cases usually have been a result of contamination of the product after pasteurization or improper pasteurization.
Milk Microbiology The Milk Microbiology section contains information relating to microbial concerns in milk.The following points highlight the three types of milk. The types are: 1. Fresh Milk 2. Pasteurized Milk 3. Fermented Milk.
This milk is endowed with all the naturally occurring constituents provided the milking is done perfectly asceptically and the milking cattle are healthy.
This milk has great nutritional value. In Ayurveda this milk has been referred to as Dharoshna milk meaning thereby that the freshly drawn milk has the same temperature as the body of the milking cattle.
In this milk no constituent is lost and destroyed. But, use of this milk has its own limitations. The milk is treated at a definite temperature for a definite time period so as to get it free from the microorganisms without losing any constituent. This treatment is called milk-pasteurization which results in the destruction of most of the diseases and spoilage causing microorganisms in milk with heat.
Home pasteurization of milk is the simplest and one of the most satisfactory methods. The milk is usually pasteurized in regular milk bottles.
Download: Microbiology Of Milk And Milk Product.pdf
In this process, cover from one bottle is removed, a little of the milk is poured out, a hole is punched in the cover, the cover is replaced and a thermometer is inserted there. After the 30 minutes period, the hot water is gradually replaced with cold water until the milk is cooled, preferably using ice in the last water.
The milk is heated in closed vats by steam coils, hot water jackets or continuous spraying of heated water along the sides of the container. It is then cooled and bottled. It has been found in practice that LTH method is the more efficient as it destroys a larger percentage of the bacteria. The heating is done by means of electricity or hot water. The heated milk is then cooled and maintained at a low temperature until distributed.
Phosphatase is an enzyme present in raw milk. This enzyme is destroyed by adequate pasteurization of the milk. If the milk is under-pasteurized it gives positive reaction to phosphatase test. To this is then added 6 drops of BQC dibromo-quinone- chloroimide solution and allowed to stand for 5 minutes. The colour developed is compared with opaque standard.
Grey or brown colour indicates proper pasteurization. Blue colour is the sign of improper pasteurization. The intensity of the colour being proportional of the extent of improper pasteurization.
Fermentation is used to a very large extent with dairy area. Here the purpose is souring and developing flavour substances. Fermentation is done commonly of the pasteurized milk. This was done to preserve milk and to provide a new beverage with a distinctive and desirable flavour.Not only do individual consumers use liquid milk for beverages and cooking, but food manufacturers use vast quantities of milk powder, concentrated milks, butter, and cream as raw materials for further processing.
Effective quality assurance in the dairy industry is needed now more than ever. Pathogens have become a major issue in dairy manufacturing. Escheria coli is a concern, and milk-borne strains of Mycobacterium avium subsp. Even little-known parasites like Cryptosporidium have caused disease outbreaks. A critical evaluation of these changes and, in particular, of their impact on the diary industry is vital if the excellent safety record of milk and milk products is to be maintained, and it is to be hoped that this book will contribute to this aim.
If it does, then the credit lies with the authors who have so generously given of their time and expertise because, in keeping with most editors, my interference with the manuscripts has been minimal.
This reluctance to modify an approach selected by a given author s of a chapter has led to minor degrees of repetition, but if a particular pathogen, for example, is important in a number of disparate products, then the relevant behavior of the pathogen may well merit additional emphasis. Email Address. Delivered by FeedBurner. Avian Brood Parasitism Previous post. Subscribe to Blog via Email. Receive Books In Email. Enter your email address: Delivered by FeedBurner. Book Download Free.Microbiology is the study of living organisms of microscopic size, including bacteria, fungi mould and yeastalgae, protozoa and viruses.
Zoom Fig. Microorganisms are found everywhere - in the atmosphere, in water, on plants, animals and in soil. Because they break down organic material, they play an important role in the cycle of nature. Microorganisms occur most abundantly where they find food, moisture, and a temperature suitable for their growth. Since the conditions that favour the survival and growth of many microorganisms are those under which people normally live, it is inevitable that we live among a multitude of microbes.
Listed below are the key characteristics of the different groups of microorganisms, see Table 4. Biotechnology has a history that predates the modern scientific disciplines of microbiology, biochemistry and process technology by thousands of years.
Until the end of the nineteenth century, these processes were associated with food, and above all with preservation of food. Microbial processes still play a prominent part in the food industry, but biotechnology in the modern sense is largely associated with industrial utilization of the properties of living cells or components of cells to obtain production of various products, such as enzymes, hormones and certain vaccines.
This chapter deals mainly with microorganisms relevant to milk and milk processing, but specific viruses called bacteriophages are also described.
Bacteriophages cause serious problems in the manufacture of products where microorganisms are needed for development of flavour, texture and other characteristics.
Bacteria are unicellular organisms that normally multiply by binary fission, i. Bacteria are classified partly by their appearance. However, to be able to see bacteria, they must be studied under a microscope at a magnification of about 1 times. Bacteria may also be stained and the most widely used method of staining bacteria was introduced by the Danish bacteriologist Gram and is called Gram staining. Bacteria are divided into two main groups according to their Gram stain characteristics: Gram negatives are red and Gram positives are blue.
This is due to differences in the bacterial envelope and gives the two groups of bacteria different properties. Morphology is the study of the form of bacteria. This covers morphological features such as shape, size, cell structure, motility ability to move in a liquidand spore and capsule formation. Bacteria come in many different shapes. However, three main characteristic shapes can be distinguished: spherical- rod- and spiral-shaped. The spherical bacteria are named cocci and when arranged in pairs they are called diplococci Figure 4.
Cocci can also be arranged in irregular clusters like grapes c and arranged in groups of four or as cubic arrangement d. Rod-shaped bacteria vary in both length and thickness. Some of them also form chains in the same way as many Bacillus species Figure 4.August 23, Applied Dairy microbiology is a very useful microbiology book.
Dairy and milk products are used in larger quantities world wide. These dairy products contain a wide array of micro-organisms. These micro-organisms also play a key role in the fermented dairy products as well. First chapter of the eBook is about the microbiology of the dairy animals. Different microbes that may be added and present as such are discussed.
Then the microbiological aspects of different dairy products are reviewed. These products include raw milk products, dry milk products, deserts, butter and similar products. Many fermented dairy items need a starter culture for their production.
The introduction to starter culture and its use is explained. The metabolism of starter culture and particularly LAB Lactic acid bacteria is also given in this book.
LAB have been used in many fermented products. They vary from pickles to yogurts. They add a particular flavor to the food. Increase in shelf life is also done by the decrease in pH they make. Fermented milks and creams are popular food items. They are also added in the context of this book. Cheese products and other commonly used dairy items also have microbiological perspective.
Applied dairy microbiology is a detailed book. It covers majority of the topics that come in dairy microbiology. The testing and analysis of dairy products help detect adulteration. Applied dairy microbiology describes methods of testing.
Later part of eBook includes information about waste treatment of dairy wastes. Data presentation in the book is nice and effective. For getting more and detailed knowledge about dairy products read the Encyclopedia of Dairy sciences. Similarly to understand the biochemistry of Dairy products we have another book reviewed.
You must be logged in to post a comment. This site uses Akismet to reduce spam. Learn how your comment data is processed. Applied Dairy Microbiology pdf Download August 23, Previous Encapsulated and Powdered Foods. Leave a Reply Cancel reply You must be logged in to post a comment. Sorry, your blog cannot share posts by email.Book Detail: Introductory Dairy Microbiology.
Module 1. Hygienic milk Lesson 1. Sources of contamination of milk Lesson 3. Hygienic milk production. Module 2. Classification of dairy microorganisms Lesson 4. Morphology and classification of dairy bacteria Lesson 5.Dairy products under a microscope - cheeses, paneer, yogurt, milk powder, meat binders.
Characteristics of important microorganisms — I Lesson 6. Characteristics of important microorganisms — II Lesson 7. Characteristics of spoilage and pathogenic microorganisms — I Lesson 8.
Characteristics of spoilage and pathogenic microorganisms — II Lesson 9. Characteristics of spoilage and pathogenic microorganisms — III Lesson Characteristics of dairy associated fungi and bacteriophages. Module 3. Microorganisms associated with milk Lesson Microorganisms associated with raw milk and their significance — I Lesson Microorganisms associated with raw milk and their significance — II Lesson Role of psychrotrophs in milk Lesson Effect of processing on microorganisms in milk.
Module 4. Microbiological methods of milk testing Lesson Qualitative and quantitative methods of milk testing Lesson Dye reduction test Lesson Direct microscopic count DMC Lesson Standard plate count SPC Lesson Coliform counts in Milk Lesson Methods of Enumeration of other groups of bacteria Lesson Enumeration of yeast and moulds in Milk.
Module 5. Role of microbes in spoilage of milk — Microbial interactions Lesson Milk fermentations Lesson Abnormal milk fermentations.
Lesson Mastitic milk — Suitability for processing and public health significance Lesson Detection of mastitic milk. Module 7.