Ever wonder how manufacturers get all the liquid out of milk, package it and sell it as dry milk? Is powdered milk nutritious; is it cow milk or is it simply a milk substitute with little nutritional value?
The Process of Making Powdered Milk
The process to make dry milk begins at the creamery. When milk first arrives, it is filtered and checked to make sure it meets the required qualities. The first step of the actual drying process begins once the milk passes the quality tests. This first step involves running it through an evaporator. The evaporators used in creameries are colandrias with some creameries using two or more in the process of drying whole milk.
As the liquid is run through the evaporator it loses about one third of its water content. During the evaporation process the milk is heated to a low enough boiling temperature so the water is evaporated without the damage to the liquid. The solids in the milk are increased from about twelve percent to about fifty percent. During this process the milk is also pasteurized which reduces the bacteria. If cooks tried this at home, the milk would end up scorched. However, at the creameries, the milk is run through small tubing that heats it for a few seconds and then immediately cools it, thus preventing damage to the milk.
After evaporation, the milk is put through the separator. The separator removes the cream and places it in a tank to be used later. The skim milk is then pushed through to tanks for standardizing. The standardizing process is the stage in which solids and butterfat are balanced, for example producing the one percent or two percent milk, to meet the creameries standards to ensure each packaged product is of the same quality. It is add this stage vitamins are added.
Drying the Milk
Milk slated for the end result of powdered milk is then sent to the drying towers. Two types of drying towers are used for this stage of the process. The spray nozzle dryers are still used by many creameries, but the newer atomization driers are increasing in popularity. The spray dryers are housed in tall towers, sometimes reaching twelve stories, where the top of the column has four spray nozzles that mist the condensed milk into swirling air heated to 400 degrees F. The swirling air removes the water from the milk droplets as they fall until minuscule of milk powder particles are all that is left. As the particle falls to the bottom, the air is cooler, about 250 degrees F, and they are collected into a funnel-shaped hopper where they are removed. Operators control the amount of moisture in the finished product by controlling the swirling of the air.
The newer atomizing driers use an atomizing wheel instead of spray nozzles. The wheels turn at extremely high speed and can produce a finer particle of milk powder. These drying towers are considered compact as they are generally about three stories high. The smaller particles of course dry faster and fall to a fluidizing bed. This is where the powder is collected and is constantly vibrating in a fluid motion (thus the name). Here, additives such as vitamins, to further increase milk nutrition, are added to the powdered and the constant motion mixes it well.
During the drying process instant milk can be made by adding a very small amount of lecithin. The lecithin is sprayed on the finer dry particles and moved to the top of the tower. As the wet and dry particles are mixed, the wet stick to the dry particles and form air pockets. As the particle dries, it falls to the bottom. Instant powdered milk is the same as powered, but because of the decrease in density, makes it more easily mixed with water. There should be no difference between the two in taste.
Uses of Powdered Milk
As creameries update their equipment with new technology the process of evaporation and drying is becoming more efficient to produce large quantities of powdered milk. One creamery alone can produce 30 million pounds of dry milk each year. A large portion of the powdered milk produced in the United States is exported to third world countries as it does not need to be refrigerated and has a long shelf life. Other uses include bakery mixes, such as boxed cake mixes.
At home, bakers can use powdered milk as a milk substitute for recipes. Add 1/8th the amount of regular dry milk in exchange for the liquid milk the recipe demands. Add the powder to the other dry ingredients and increase the water measurement to include the amount required by adding the measurement of liquid milk the recipe required. For example, if the recipe calls for two cups of liquid milk, use 1/4 cup of regular milk powder and two cups of water (1/8th of 2 cups = ¼ cup).
Instant milk mixes better than regular dry milk; however, it is more expensive and takes more shelf space. To get a smoother yield when using regular dry milk, mix the powder the night before, put it in the refrigerator and the lumps with dissolve during the night. Before serving, stir it again. For immediate use, fill a glass about 1/8 full, add about 1/3 glass of water. Mix the powder until creamy and then fill the glass the rest of the way with cold water. Almost all of the lumps should be gone.
Using liquid, powdered, or instant dry milk is a choice. Powdered milk provides a less expensive product for struggling families. Though many consider it milk substitute, powdered milk is not a substitute—it is milk with all the nutrients of liquid milk.
http://findarticles.com/p/articles/mi_m3289/is_n9_v162/ai_14462693/ Dairyman's co-op powders up for profits - Dairyman's Cooperative Creamery Association's milk drying plant Tulare, California
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