During the ancient times, our ancestors consume milk in its fresh form. Today, milk comes in many forms. This is due in large part of various processes that it may undergo. Some of these include pasteurization, fortification, bleaching, and homogenization. And it is indicated on the packaging or container if the milk has gone any of these processes. The words “pasteurized” and homogenized” are most common. So what is homogenized milk, anyway?
The process of homogenization started in Europe when it was invented in 1899 by French inventor August Gaulin. When the process was introduced in North America in 1909, the reception was lukewarm. But the public eventually accepted homogenized milk nearly 20 years after its introduction.
The primary purpose of homogenization is to prevent creaming, or the rising of fat to the top of a milk container. To do this, the size of the fat globules is decreased while increasing their number to make them evenly distributed throughout the milk. The homogenization technique permanently emulsifies the tiny fat globules by pumping milk under high pressure at 2,000 to 2,500 lb/in.2 (psi) through small mesh orifices in a homogenizer, a machine that creates a uniform and even mixture.
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The homogenized milk introduced in America in 1909 was made by a Gaulin homogenizer and milk sterilized in bottles at 226°F (108°C) for 20 minutes. This early form of a homogenizer consisted of a three-piston pump that pushed a mixed stream of milk and cream through tiny capillary tubes or valve.
If properly performed, homogenization gives milk a more homogeneous composition, better body and texture, a whiter look, richer flavor, and more digestible curd.
HOW HOMOGENIZATION WORKS
Homogenization provides permanent emulsification. This is due to the fact that as the surfaces generate new fat globules, each fat globule is covered with a portion of the lipoprotein membrane as well as extra proteins from casein and whey. As a result, these proteins adsorb onto the newly formed oil surface. This prevents globules from rejoining or coalescing and ensuring that fat is evenly distributed throughout milk.
Milk fat globules range in diameter from 1 to 10 microns when fresh from the cow. Following homogenization, the globules range in diameter from 0.2 to 2.0 m. Raw milk is homogenized by forcing it under pressure through very small diameter nozzles. Large milk globules are driven through an opening. This makes the membranes to shear, essentially breaking the tough globule coverings while mixing and forming many smaller fat globules. If the protein surface load is still low, the frequent collisions between newly produced drops could lead to recoalescence.
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The exposed lipid droplets are immediately covered by casein proteins from the milk’s liquid phase. As a result, casein-coated milk fat globules are smaller and less prone to separate from the rest of the milk. The negative charge of the casein proteins prevents milk fat globules from combining and forming a solid layer of fat.
Homogenization is most efficient when the fat phase is liquid, and temperatures between 140°F (60°C) and 158° (70°C) are typically used. A rise in temperature results in a little reduction in particle size. A temperature so low is not good either as it makes part of the fat crystalline.
Milk can be homogenized before or after pasteurization. The homogenization procedure is conducted quickly to ensure bacterial control and quality loss.
WHY HOMOGENIZED MILK?
When buying milk, it may be confusing as to which form to get. But is homogenized milk for you? It depends. Prevention of creaming is the main purpose of homogenization. But there are other benefits as well.
If you are someone whose stomach has a hard time digesting milk, Then homogenized milk is for you. Since its fat globules have been broken down into smaller particles, homogenized milk can be consumed without having an upset stomach afterwards.
Homogenized milk also has a whiter appearance than a non-homogenized milk. This is generally more acceptable than milk that is cream in color. This white color of homogenized milk is because of more evenly distributed fat. Due to the smaller fat particles, there is an increase in light absorption and reflection.
Some milk gets its white appearance because of bleaching. Bleaching is a process that makes milk white by treating the carotenoid or chlorophyll pigments with compounds such as benzoyl peroxide (BP). The Food and Drug Administration (FDA) permits the use of BP as a bleaching agent in milk, or in a mixture with potassium alum, calcium sulfate, or magnesium carbonate. But if you want white milk without such compound added, get homogenized milk.
The use of homogenized milk also has several disadvantages.
The production of any product that depends on the aggregation and gelation of the caseins, such as rennet curd formation or acid gelation in fermented milk, yields a final product that differs from equivalent foods derived from unhomogenized milk in terms of rheological and textural characteristics.
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The fat globules are also more prone to lipolysis when active lipase is present and to light-induced oxidation, both of which can be easily avoided by opaque packing.
