Friday, August 21, 2020

Milk and dairy foods

Milk is the secreted fluid of the mammary glands of female mammals. It contains nearly all the nutrients necessary to sustain life. Since the earliest times, mankind has used the milk of goats, sheep and cows as food. Milk is basically composed of water (~87 percent), milk fat (~4 percent) and non-fat solids (~9 percent).

In addition to milk, several dairy products such as cream, butter, yogurt, kefir, and cheese have been produced and consumed worldwide for millennia.

Fresh milk is highly perishable, bulky, and easily contaminated (it is a favorable medium for bacterial growth). Because it is so susceptible to contamination and adulteration (with water), fluid milk production, treatment and distribution is widely subject to controls.

Milk tastes mildly sweet, while its odor and flavor are normally quite faint. Cow milk generally contains between 3 and 4 g of fat/100 g, although values as high as 5.5 g/100 g have been reported in raw milk. Most milks consumed now contain a standardized fat content of around 3.5 g/100 g.

Milk fat occurs in the form of droplets or globules, surrounded by a membrane and emulsified in milk serum (also called whey). The fat globules (called cream) separate after prolonged storage or after centrifugation. The fat globules float on the skim milk. Homogenization of milk so finely divides and emulsifies the fat globules that cream separation does not occur even after prolonged standing.

The major proteins found in milk are casein and whey proteins, with casein (αs1-, αs2-, β-, and κ-casein) accounting for approximately 78 percent of the protein in cow milk and whey proteins accounting for about 17 percent of the total protein

Milk and dairy products are nutrient-dense foods, supplying energy and high-quality protein with a range of essential micronutrients (especially calcium, magnesium, potassium, zinc, and phosphorus) in an easily absorbed form. Milk minerals are crucial for human health and development as well as in dairy processes as cheese-making and for all traits involving salt-protein interactions.

In recent decades, technological advances have supported the development of new dairy-based products. Broadly, dairy products can be categorized as basic products, such as fermented milk, cheese and yoghurt, and value-added products, such as low-fat and fortified milks.

Milk can be internationally traded either in dry, evaporated or condensed whole milk form or as dry skimmed milk powder (NFDM). These whole milk products may be reconstituted to fluid milk by mixing with water. Skimmed milk powder is reconstituted by mixing with butteroil (anhydrous milk fat) or vegetable fats and water to obtain a mixture of about 3.5 to 4 percent fat and 9 percent non-fat-solids. Well-reconstituted milk is said to be practically indistinguishable from fresh milk.
Milk and dairy foods

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