The history of enrichment of milk started as of early half a century ago. In the same direction, enrichment of milk with vitamin “D” was first reported as of 1923 and presently, milk enrichment is carried out with vitamins “A” and “D”.
The history of milk enrichment started as of early half a half- century ago. In the same direction, enrichment of milk with vitamin “D” was first reported as of 1923 and presently, milk enrichment is carried out with vitamins “A” and “D”.
The U.S. Food and Drug Administration (FDA) in 1923 announced that amount of vitamin “D” added to milk is better not to exceed IU400 in each quart (equal to one liter).
Milk is a nutrient substance. With enjoying all necessary 10 amino acids and also very high- quality protein, not only milk shares in total daily received energy, but also it contains necessary fatty acids, immunoglobulin and other micro foods. Although milk of goat, buffalo, sheep and camel is also consumed, cow milk is a predominant type in several countries in world. It should be noted that milk is used in fermented forms like cheese, yogurt (kefir), dough (sour yogurt drink) and butter as well. In the same direction, milk in industrial form is divided into two groups of liquid milk and powdered or dried milk.
Content of Micro Nutrients in Milk:
Milk is rich in calcium, vitamin “B2” and is a good source of vitamin “A”. Milk also is a weak source of vitamin “D”. Nevertheless, dependency on the change of food patterns in various seasons of year, some changes are observed in content of vitamins of milk as well. In summertime, cow is grazed and pastured with wet and fresh grasses while in wintertime, it is fed with warehoused dry fodder and forage. For example, vitamin “A” of fresh milk in U.S. is IU1800 – 600 /liter while vitamin “D” of milk is IU40- 5 /liter. It should be noted that warm milk is used by human being in order to prevent from risks threatening health of human with relation to pathogenic microorganism available in raw milk.
In developing countries, major part of milk is produced by small cattle breeding houses and is sold to consumer/ customer directly. The thermal care which is common for liquid milk includes pasteurization of care with ultra heat or ultra heat temperature (UHT) and sterilization. To obtain powdered milk, fresh milk is first heated and then, it is dried into powder in spray, roll or cylindrical forms. These industrial processes eradicate some nutrients especially the vitamins which can be found naturally in milk. Moreover invigorating process, the nutrients, which are eradicated during milk processing operation, can be added to milk. In many countries, milk fat is exited industrially for producing low- fat or fatless milk. When milk fat is removed, solvable vitamins in fats will also be removed.
Therefore, these vitamins can be substituted with invigoration or improvement process.
Nutrients Added to Milk
Milk enrichment with vitamins “A” and “D” is carried out by only limited countries. In some dairy industries based in U.S., milk is enriched with vitamin “C”, calcium, plus vitamins “A” and “D”.
As a factor for improvement of color, beta-carotene is added to some milk byproducts such as butter. Powdered milk and favored powdered milk or seasonings are almost enriched with vitamins “A” and “D”, calcium and iron (folic acid). Special milk- based infants’ formulas and/or foods as substitutes to breastfeeding are enriched with a series of vitamins and minerals and other nutrients such as unsaturated fatty acids.
The powdered milks in Chile used in children’s supplementary nutrition are enriched with vitamins “C”, iron, copper and zinc.
The nutrients added to milk depend on several factors such as milk consumption level, milk sensory specifications (flavor, taste and color), and stability of nutrients during milk preservation and processing stages. The liquid milk especially the milk producing cream is enriched with vitamins “A” and “D” with 5,000 and 500 international units/ liter.
The technology of enriching milk is simple and all vitamins and minerals, which can be added to milk, are available in the form of powdered milk and vitamins solvable in fat in the form of oil. Usually, more than a nutrient may be added to milk and these nutrients are mixed with each other previously and can be turned out in unified form.
The technology of enrichment of milk is very simple and all vitamins and minerals can be added to the milk, available in the form of powdered milk and vitamins solvable in fat in the form of oil.
It should be noted that enrichment of liquid milk, vitamins solvable in fat can be added in two forms of dry or oily, provided that vitamins solvable in water and minerals are added directly to the liquid milk in dry form. Enrichment of liquid milk is carried out just before pasteurization process or Ultra Heat Treatment (UHT) operation. Of course, fair distribution of nutrients should be assured before heat treatment process. When vitamins are used in oily form, homogenization is necessary.
Enrichment of Powdered Milk (Dried Milk Fortification)
Although oily forms of nutrients can be added to the powdered milk, mixing powdered or dried forms of vitamin and minerals with the powdered milk can be considered as the simplest way of enrichment of powdered milk. Unlike liquid milk, dry or powdered milk can be enriched before and after heat treatment. Sprayed powdered milk is considered as the most applicable methods of enrichment of this type of milk. It should be noted that vitamins are susceptible and sensitive to temperature, light, humidity, moist, oxidation factors and revival with various grades.
Recent progresses and advances in commercial production technology of vitamins have been improved with stability and have made capability of accordance with micronutrients possible. Generally speaking, minerals are less susceptible to chemical and physical factors.
In the course of procession period and after a period of industrial heat treatment, most minerals and vitamins are preserved as much as 70- 100 percent at large but with the repetition of heat treatment, percentage of these nutrients are changed. Stability of most nutrients at liquid milk during storage operation is good but vitamin “C” which is analyzed or decomposed easily under the influence of light and oxygen is an exception to the said rule. Pasteboard packs can store nutrients better than plastic materials. Moreover, pasteboard packs are resistant against destructive effects, light, flavor and odor. In the same direction, enriched powdered milk, which is stored in environment temperature for a period of 24 months, can safeguard 90 100 percent of vitamins “E1″, “C”, “B6″, “B2″ and “B” during storage operation. If the powdered milk is stored for a period of five months, its 55- 75 percent of vitamin “A” will be reduced considerably.
Various types of micronutrients of the powdered milk can be perished during storage and preservation operation. Given the said issue, storage of powdered milk is of paramount importance. To get rid of this problem, a suitable amount of these materials should be added to milk.
Quality Control (QC)
To ensure favorable amounts of micronutrients and before using them in final product, necessary tests should be repeated. For this aim, special methods and equipment should be accessed certainly. For unstable nutrients like vitamin “C”, accurate QC and plan should be taken into consideration. Vitamins “A” and “D” can be determined using HPLC (High Performance Liquid Chromatography) quantitatively.
This method is accurate and precise but its parts and equipment are expensive and needs to be manipulated by specialists and technicians.
Spectrometric methods are cheap which can be supplied with fair and reasonable price in a way that working with them is rather easy and comfortable. It should be noted that quantitative methods for rest micronutrients include fluorometer method for vitamins “B1″ and “B2″.
It should be noted that spectrophotometric method us for minerals like iron and calcium.