Membrane separation technology has the advantages of low environmental pollution, low energy consumption, no need to use additives, avoiding thermal damage to products, and concentrating or separating materials while filtering, making it more and more used in dairy processing. Practical value and broad application prospects.
The current applications of membrane separation technology in dairy processing mainly include:
① Application of reverse dialysis technology in concentrated whey;
② The application of nanofiltration technology in the desalination and concentration of whey, circulating processing water, circulating alkaline and acid cleaning liquid, concentration and purification of sugar liquid, protein hydrolysate and fermentation liquid;
③ The application of ultrafiltration technology in protein concentration, separation and purification;
④ Application of microbial filtration technology in removing microorganisms, spores, viruses and antibodies;
⑤ Application of electro-membrane filtration in the selective separation and purification of charged components (such as biologically active proteins, peptides and other small molecular weight components with similar molecular weights but different charged components), hydrolysate treatment, and recovery of lactoferrin.
In milk production, membrane separation technology can be used for degreasing, sterilization and concentration of large-molecule casein substances. The size of bacteria in milk is generally greater than 0.2μm, and the size of fat particles is between 0.1-2μm, so the use of microfiltration membrane can remove bacteria in milk.
For skimmed milk, its quality does not change much before and after microfiltration sterilization. In the study of whole milk, it was found that the use of 1.8μm alumina membrane for microfiltration can reduce the number of bacteria by a factor of two, while 98% of the fat is removed, while the protein is better retained in the filtered milk.
Membrane separation technology can be used to prepare liquid cheese with high protein content (>20%-22%) in cheese production, as a raw material for soft or semi-hard cheese. Treated by ultrafiltration membranes, fat and protein remain in the concentrated liquid, while lactose, dissolved protein, minerals and other trace components remain in the whey liquid, so that the ratio of protein to fat reaches the normal level of cheese and becomes a liquid standard cheese.
Actually, it is proved that the production of cheese by ultrafiltration method can increase the cheese output by 10%-30%, reduce the consumption of rennet by 70%-85%, and realize the continuity and automation of production. At the same time, in the process of producing fresh cheese by lactic acid fermentation of skimmed milk or whole milk, the aqueous phase containing lactose and inorganic substances needs to be separated from the fermented yogurt system, while all the protein and fat remain in the retentate. Traditionally, evaporative concentration method or centrifugal separation method is used, which not only consumes high energy, but also destroys some heat-sensitive components in milk and affects product quality. By adopting ultrafiltration and reverse osmosis membrane technology, instead of evaporative concentration or centrifugal separation process, cheese and sweet yogurt with satisfactory quality can be produced.
The main purpose of whey processing is to recover the protein in the whey. Compared with traditional evaporation and concentration, membrane technology can not only reduce protein denaturation caused by heating, but also has obvious advantages in product purification. At present, in the recovery of whey protein, the commonly used process is to use ultrafiltration to concentrate and separate the whey. Whey protein powder with a protein content of 35% to 85% can be obtained through ultrafiltration separation. With the help of the full filtration of the continuous dilution of the concentrated phase, a whey protein powder with higher protein content can be obtained. In addition, the introduction of ultrafiltration and the combined reverse osmosis technology can remove lactose and ash from the membrane permeate while concentrating the whey protein. This greatly expands the application range of dry whey. The ultrafiltration and reverse osmosis introduced improved the quality of whey protein. Compared with the products produced by traditional technology, the protein content has increased by nearly 4 times and the lactose content has been reduced by about 40%.
Membrane separation technology provides a new method for ensuring the quality of dairy products, product development, improving the efficiency of dairy enterprises, and increasing profits. It has become a powerful processing method to ensure the safety of dairy products without destroying the nutritional content of dairy products. The discovery, purification and verification of new functional ingredients in the dairy industry has opened up a new path and created new conditions for the development of food health functions.