Milk powder Mohammed Sabah
Presentation structure • Introduction • General process description • Specifications necessary toDrying milk • manufacture • Food and health uses • Reconstitution • Nutritional value • Export market • Use in biotechnology • Hygienic Aspects • Insolubility • Deterioration • Other types of milk powder.
Introduction • Powdered milk or dried milk is a manufactured dairy product made by evaporating milk to dryness. • One purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. • Another purpose is to reduce its bulk for economy of transportation.
General process description • Production of the milk powder takes a place in several stages: raw milk handling, liquid treatment, milk concentration, drying and milk powder handling. The most important stage before the drying is milk concentration. This is often done by means of vacuum evaporators because of their low overall energy consumption. In general, drying processes are characterized by high energy requirement. Removing water by drying is more costly than by vacuum evaporation. Therefore, as much water as possible will be removed during the concentration stage. The latest evaporator technology makes it possible to remove more than 55 % water. After the concentration stage the concentrated milk with a dry solids content of 40 – 45 % is fed to the drum dryer.
Specifications necessary to Drying milk Acidity should be less than 0.15%. Increased acidity for simple varying reduce the solubility of milk powder. The significant increase in the acidity of the milk lead to clotting of Casein.
Approximate Composition (% w/w) of Some Types of Powder Powder From Constituent Whole Milk Skim Milk Whey Sweet-Cream Buttermilk Fat 26 1 1 5 Lactose 38 51 72-74 46 Casein 19.5 27 0.6 26 Other proteins 5.3 6.6 8.5 8 ‘Ash’ 6.3 8.5 8 8 Lactic acid — — 0.2–2 — Water 2.5 3 3 3
manufacture • In modern times, powdered milk is usually made by spray drying. • Pasteurized milk is first concentrated in an evaporator to approximately 50% milk solids. • Alternatively, the milk can be dried by drum drying.
Milk powder manufacturing process There are several ways to manufacture milk powder, but the most quality and widely used at the moment is a spray drying method Spray drying process. Method and principle: Milk is concentration by evaporation before entering the drying tower (50-60% dry matter), then milk is sprayed by machine gun installed in the top of the conical tower.
SPRAY DRYING • Spray drying involves atomizing concentrated milk into a hot air stream (180 ͦC – 200 ͦ C). The atomizer may be either a pressure nozzle or a centrifugal disc. By controlling the size of the droplets, the air temperature, and the airflow, it is possible to evaporate almost all the moisture while exposing the solids to relatively low temperatures. Spray drying yields milk powders with excellent solubility, flavor and color. This is the most common procedure for manufacturing milk powders. • The spray drying process is typically a two-stage process that involves the spray dryer at the first stage with a static fluid bed integrated in the base of the drying chamber. The second stage is an external vibrating fluid bed.
BASIC MILK POWDER PRODUCTION Sieve = غربال Pack كومه=
Food and health uses Powdered milk is frequently used in the manufacture of infant formula, confectionery such as chocolate and caramel candy, and in recipes for baked goods where adding liquid milk would render the product too thin. It is widely used in many developing countries because of reduced transport and storage costs (reduced bulk and weight, no refrigerated vehicles).
Nutritional value • Milk powders contain all twenty-one standard amino acids, the building blocks of proteins, and are high in soluble vitamins and minerals. • According to USAID, the typical average amounts of major nutrients in the whole milk powder are (by weight): • 25_27% protein, • 36_38% carbohydrates (predominantly lactose) • 26-40% fat • 5-7% ash • calcium 1.3%, • potassium 1.8%.
Export market European production of milk powder is estimated around 800.000 tons of which the main volume is exported in bulk packing or consumer packs. Brands on the market include "Nido", from the company Nestlé, "Incolac" from the company Belgomilk, and "Dutch Lady" from FrieslandCampina.
Hygienic Aspects • The causes for milk powder to be bacteriologically unacceptable or evenunsafe can be of three kinds: 1. In the fresh milk, bacteria are present that are not killed by the heat treatments to which the milk is subjected before and during drying.
Hygienic Aspectscontinue… 2. Conditions during the various process steps until the product is dry do allow growth of some bacterial species 3. During manufacture, incidental contamination may occur. The level of contamination is generally low and remains low if the bacteria involved cannot grow.
Insolubility • Insolubility can be estimated in various ways. • In all tests, powder is dissolved in water under standardized conditions (concentration, temperature, and duration and intensity of stirring), and then the fraction that has not been dissolved is estimated (e.g., volumetrically after centrifugation or via determination of dry matter). • The result is called the insolubility index.
DETERIORATION • The most important variable determining the rate of undesirable changes in milk powder is the water content. • When comparing different types of powder, it is probably easiest to consider water activity (aw).
DETERIORATION Continue… • Maillard reactions increase considerably with water content and with temperature. • They lead to browning and to an off flavor. • Autoxidation of the fat and the ensuing tallowy off-flavor pose a difficult problem when storing whole milk powder. • The rate of autoxidation strongly increases with decreasing aw.
DETERIORATION Continue… • Loss of nutritive value during storage primarily concerns loss of available lysine due to Maillard reactions. • Storage at 20°C at a normal water content does not cause an appreciable loss; at 30°C, a loss of 12% after storing for 3 years has been reported. • Extensive Maillard reactions cause a decrease in protein digestibility and formation of weak mutagens.
DETERIORATION Continue… • Of greater concern is the loss of vitamin A in vitamin-fortified skim milk powder, due to its oxidation. • This especially occurs if the vitamin preparation is dissolved in oil and then emulsified into the skim milk before atomization. • Usually, dry added preparations are more stable.
OTHER TYPES OF MILK POWDER: 1.Roller-dried milk looks completely different from spray powder in the microscope. It consists of fair-sized flakes. Due to the intense heat treatment during the drying it has a brownish color, a strong cooked flavor, and the availability of lysine has been considerably reduced, by 20 to 50%.
Continue… 2.Freeze-dried milk consists of coarse, irregularly shaped, and very voluminous powder particles, which dissolve readily and completely. • However, the fat globules show considerable coalescence, unless intense homogenization has been applied. • In most cases, damage due to heat treatment is minimal.