How is milk powder made? Generally, the process of making milk powder is to collect fresh raw milk or raw goat milk. Some designs use vacuum evaporation tanks to concentrate milk into cakes, then dry them into powder, and then enter the factory for inspection or filtration and purification for standardization. Some designs are to spread the initially concentrated milk on a heated drum, peel off the marked thin milk film and then make it into powder. It is also necessary to choose the instantaneous sterilization method of high temperature for a short time or ultra-high temperature, and add some sucrose to make the baby sweet when drinking milk powder, or concentrate it in vacuum. The most common method is spraying. This method is to vacuum concentrate concentrated milk to 1/4 of the original volume, then spray hot air into the drying room in mist, dehydrate it, make it into powder, then quickly cool and sieve it, and then package it into finished products.
Practice the production process of raw milk project acceptance → data pretreatment → heating sterilization → concentration → spray drying → cooling → sieving powder → packaging → loading → inspection → finished products.
1. Acceptance and pretreatment of raw milk: raw milk must be fresh and cannot be mixed with abnormal milk. The specific gravity should be 1.028 ~ 1.032 (20℃), the acidity should not exceed 20 T, the fat content should not be lower than 3. 1%, and the milk solid content should not be lower than 1652. The number of miscellaneous bacteria shall not exceed 200,000 /ml. Qualified milk should be filtered and purified.
2. Preheating sterilization: The purpose is to kill microorganisms in milk and destroy the activity of enzymes. Generally, high-temperature short-time sterilization method or ultra-high-temperature instantaneous sterilization method is adopted. If a chip or tube sterilizer is used, the usually adopted sterilization conditions are 80 ~ 85℃ for 30 seconds or 95℃ for 24 seconds. If the ultra-high temperature instantaneous sterilization device is used, it is 120 ~ 150℃ and held for 1 ~ 2 seconds.
There are three ways to add sugar when producing sweetened milk powder:
(1) Add sugar during preheating and sterilization;
(2) pulverizing sucrose, sterilizing, mixing the powder with sprayed milk powder, and canning;
(3) Add some sugar during preheating and sterilization, and then add the remaining sugar when canning.
In general, methods (2) and (3) can be used to produce sweetened milk powder with a sugar content of 35%. However, according to national standards, the sucrose content in sweetened milk powder should be below 20%.
3. Concentration: The sterilized raw milk should be concentrated in vacuum immediately. Generally concentrated to about 65438 0/4 of the raw milk volume. Concentrating equipment, generally small dairy plants use single-effect vacuum concentration pots, larger dairy plants use double-effect or triple-effect vacuum evaporators, and some also use chip vacuum evaporators. The concentrated milk after concentration should be filtered, generally using a double filter.
4. Spray drying: firstly, the filtered air is sucked by the blower, heated to 130 ~ 160℃ by the air heater, and then sent to the spray drying room. At the same time, the filtered concentrated milk is pumped by a high-pressure pump to a sprayer or a milk pump to a centrifugal spray turntable, and the sprayed 10 ~ 20 micron milk drops fully contact with hot air for intense heat exchange and mass exchange, so that the water can be quickly removed and evaporation drying can be completed instantly. Then settled at the bottom of the drying chamber, continuously discharged by the powder discharging mechanism, and cooled in time. Finally, sieving the powder and packaging.
5. Powder discharging and cooling: the milk powder in the spray drying room should be discharged quickly and continuously and cooled in time to avoid lowering the product quality due to long heating time. The commonly used powder discharging machinery in dairy industry includes screw conveyor, roller valve, vortex gas seal valve and electromagnetic oscillation powder discharging device. Advanced production technology is to connect the processes of powder discharging, cooling, powder screening, powder conveying, powder storage, weighing and packaging into a continuous production line. After the powder is discharged, it should be screened and dried immediately. So as to cool the product in time. Spray-dried milk powder should be cooled to below 30℃ in time. At present, fluidized bed powder cooling device is widely used.
6. Weighing and packaging: Milk powder should be packaged in tinplate cans, glass cans or plastic bags immediately after cooling. According to the different storage period and use requirements, it can be divided into small pot sealed packaging, plastic bag packaging and large packaging. For milk powder that needs long-term storage, it is best to use 500g tinplate cans for vacuum filling and sealing packaging, and the storage period can reach 3-5 years. For short-term sale, they shall be packed in polyethylene plastic bags, each containing 500g or 250g, and sealed by welding with high-frequency electric heaters. Small package weighing requires accuracy and speed, and generally adopts automatic capacity or weight weighing canning machine. Milk powder in large packages is generally supplied to people with special needs, and it is also divided into canned and bagged. Weight per can12.5 kg; Each bag weighs 12.5 kg or 25 kg.
Product quality standard: 1. Sensory index: pale yellow dry powder, no impurities such as clots, and the taste and smell of sterilized milk.
2. Physical and chemical indicators: moisture is not higher than
3.00%, fat not less than 26%, acidity not more than 20 T, solubility index not less than.
1.5ml, impurity degree not higher than 16ppm, lead (calculated as pb) not higher than 0.5ppm, copper (calculated as Cu) not higher than 4ppm, mercury (calculated as Hg) not higher than 0.03ppm, bhc not higher than 0.3ppm and DDT not higher than 0.2ppm. ..
3. Microbiological indicators: the number of miscellaneous bacteria shall not exceed 50 000 /g, the coliform group (approximate value) shall not exceed 90/100 g, and no pathogenic bacteria shall be detected.