Common Microorganisms Found in Milk and Dairy Products

Pathogenic microorganisms have the ability to spread to humans through the consumption of milk and various dairy items. A range of illnesses, including tuberculosis, brucellosis, diphtheria, scarlet fever, Q-fever, and gastroenteritis, can be contracted via these milk-related products.

The deterioration of dairy goods presents a significant global economic challenge. The volume of microorganisms present and the frequency of bacterial pathogens within food items function as indicators of food quality. Many of the risks linked to microorganisms in dairy products, like butter, cheese, and yogurt, stem from raw milk.

Domesticated animals serve as a primary reservoir of pathogens that can be transmitted to milk. Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7, and Campylobacter are the most frequently encountered potential pathogens linked to milk and dairy products in industrialized nations.

Raw milk provides an environment conducive to the growth of bacteria that can be managed or eradicated through the pasteurization procedure.

Undesirable alterations in butter can arise due to the proliferation of Flavobacterium spp., Pseudomonas putrefaciens, and Shewanella putrefaciens. Pseudomonas fragi and occasionally Pseudomonas fluorescens growth can result in fruity odors, rancidity, and proteolytic activity.

In the manufacturing of hard cheeses, specific bacteria, such as L. monocytogenes, S. aureus, and Salmonella, can remain viable without subsequent proliferation.

The potential danger posed by pathogenic bacteria has been significantly mitigated, and the occurrence of outbreaks associated with milk and dairy products has consistently decreased. This is predominantly attributable to contemporary milk production practices that underscore sanitary measures, enhanced udder health, herd evaluations, appropriate cooling, meticulous handling and storage of raw milk, and the near-universal adoption of pasteurization.
Common Microorganisms Found in Milk and Dairy Products

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Sweetened condensed milk

Sweetened condensed milk (SCM) is one of the oldest industrially produced dairy products. The method of preserving milk by sterilizing evaporated milk in sealed containers was developed at the beginning of the 1880s. Earlier, in about 1850, the method of preserving evaporated milk by the addition of sugar had been perfected by an American. Gail Borden was the first to conceive and patent a process for condensing milk which proved practical and resulted in the development of a patent on the condensing process in 1856.

Sweetened condensed milks are milk products which can be obtained by the partial removal of water from milk with the addition of sugar, or by any other process which leads to a product of the same composition and characteristics.

Fresh milk is clarified and standardized to a suitable level of fat, and it is then heat treated at 85–90 °C for several seconds. This heating process acts as a hurdle, which destroys the majority of microorganisms. It also decreases fat separation and inhibits oxidation. The water content of the milk is reduced due to evaporation.

The high sugar concentration in sweetened condensed milk increases the osmotic pressure to such a level that most of the microorganisms are destroyed. This product is not heat treated after packaging as its high sugar content preserves it for a long shelf-life. The sugar concentration in the water phase must not be less than 62.5 % or more than 64.5 %.

Condensed milk is a convenient product for household use, processing, as it does satisfactory keeping qualities, it is particular useful on-board ship and in the tropics.

Condensed milk products have several advantages over fresh milk, such as they require less storage space, they retain high quality, they preserve milk’s valuable surplus nutrients, and they reduce transportation costs.
Sweetened condensed milk

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Fortification of dairy products

Milk in its natural form is almost unique as a balanced source of man's dietary need. The various steps in processing and storage have a measurable impact on some specific nutrients.

Fortification is defined as the practice of deliberately increasing the content of an essential micronutrients such as essential vitamins and minerals to food. The fortification of food products has been practiced for more than 80 years.

The micronutrients which are commonly used in the fortification of the food products such as milk and its products are:
• Vitamins and co-vitamins
• Essential minerals
• Essential fatty acids
• Essential amino acids
• Phytonutrients
• Enzymes

Vitamins are compounds which play a role as cofactors in the body. Fermented milk products such as yogurt can be thought as vitamin sources. Vitamin concentrates with vitamins A and D are used for fortification of fluid milk.

Vitamin fortification has a long history in fluid milk in the United States to reduce rickets in children, and the FDA mandated in the 1990s that fortified fluid milks must be within 100% to 150% of label claims to address documented variability in vitamin amounts.

Iron-fortified yogurt has a relatively high iron bioavailability. Iron fortification of milk and dairy product is considered as a potential approach to prevent the iron deficiency disorder , since dairy foods are an important part of the daily diet in most parts of the world.

Iron fortification of milk or dairy products induces several bio physicochemical modifications with important consequences. Iron fortification of food is regarded as the most cost-effective method for reducing the prevalence of nutritional iron deficiency. Iron deficiency induces anemia, alters mental development, decreases immunity, impairs cognitive scores in children and leads to poor pregnancy outcome.
Fortification of dairy products

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Fat filled milk

Unsweetened and sweetened condensed milk can be made from fresh milk or recombined milk (nonfat dry milk, fat and water). When the source of fat is other than butterfat, the resultant milk is called filled milk.

Filled imitation dairy products are made in semblance of a dairy product. A vegetable or animal fat is used to substitute for milk fat.

Today, filled milk can be found on the canned milk shelved of any supermarket. Fat-filled powders are frequently manufactured for use as alternatives to whole milk, in both human and animal nutrition.

For human consumption filled milk powder contain 26 to 28% fat and are used for reconstitution, either domestically or by caterer. The type of vegetable oil, or oils sued will depended on nutritional requirements of the product, as different oils can be used to achieve a given fatty acid profile and given ratios of saturated, mono unsaturated and poly-unsaturated fats.

For animal feeding, fat filled milk powder contain 30 to 50% fat and up to 2% of emulsifying agent e.g. lecithin, monoglycerides.

Hardened palm kernel and coconut oils have commonly been used in fat-filled milk powder production but selectively hydrogenated rapeseed oil has found favor in grounds of cost.

While it contained no butterfat, filled milk had the same taste, odor, color consistency, specific gravity and cooking qualities as ordinary evaporated whole milk.
Fat filled milk

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Milk and dairy foods for good health

Milk is the product obtained by simple or multiple milking of mammals that are kept for the purpose of milk production.

While milk products are made entirely from milk. In certain cases, additives can be used during the manufacture. Milk and many of the products made from it are staples in the diet of people throughout the world.

Although fluid whole cow; milk is a liquid food (87% water), it contains an average of 13% total solids and 9% solids-non-fat, an amount comparable to the solids content of many other foods.

More than 100 different components have been identified in cow’s milk. Important nutritional contributions of milk and milk products are calcium, protein, potassium, vitamin A, vitamin B12, riboflavin, niacin and phosphorus.  Milk can also make a contribution to dietary vitamin D intake, especially when fortified.

An ever increasing variety of milk and other dairy products is available to meet the taste, nutrition, health and convenience demands of consumers. Milk products include cream, butter cheese, casein, yoghurt, clabber, gelato, ice cream and others.
Dairy products of varied fat content, of low or reduced lactose content, fortified with nutrients such as vitamin A, D and calcium, and processed to improve keeping quality are available.

The fat content in different milk products varies greatly, raging from a few percent in yoghurt to 80% in butter. It is suggested to eat moderate amounts of these foods and choose lower fat alternatives.

Dairy fats contain a range of lipids that may have health-promoting properties including omega-3 LS-PUFA, gangliosides, sphingolipids, etc.
Milk and dairy foods for good health

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