Industrial Applications of Ultrafiltration(UF) membranes
Other than ETP's and STP's, Ultrafiltration membranes are used in various processing Industries like Food industry, Dairy Industry, Dyes Desalting, Purification of "Optical Brightener Agent" & Pigment (like TiO2), Metal Recovery, Pharmaceutical Industry.
Fig 1.1 Ultrafiltration Process in Whey concentration
1.1 Dairy Industry
a. Whey concentration
Ultrafiltration is the next leg on the Membrane filtration spectrum in Food Industry. It is characterized as having a molecular weight cut-off range (MWCO) from about 3000 to 100,000. The most common cut-off is the dairy standard of 10,000 MW. This is the traditional size for the fractionating of whey proteins from lactose commonly used to produce whey protein concentrates (WPC) of 35% to 85%WPC's.
b. Cheese production
In the cheese vat, Ultrafiltration of milk is yet another way of increasing solids. The major difference between reverse osmosis and ultrafiltration is that reverse osmosis retains all of the milk solids while ultrafiltration allows lactose and many milk minerals to pass through the membrane. This often has a benefit to the cheesemaker, as this cheese will produce less whey to handle and increase the throughput of existing cheese vats.
Fig 1.2 Comparison of Traditional and Ultrafiltration way of making soft cheese
c. Milk concentration
Ultrafiltration is being used to increase the percentage of protein in fluid milk as a method of fortifying proteins in fluid milk. This allows the flavor and mouth feel enhancing properties of milk proteins to be achieved naturally as opposed to adding non-fat dry milk which often leaves a cooked flavor in the fluid milk as well as increased sweetness from the excess lactose in NFDM. The resulting non-fat or low fat varieties have the flavor and mouth feel of whole milk product without the higher fat.
Fig 1.3 Ultrafiltration process of Milk Concentration
d. Ice cream processing
In the Ice cream industry, Ultrafiltration of milk ahead of the mix is mainly used to alter the lactose content. Increasing the protein level of ice cream allows for greater water mobilization, however adding Non fat dry milk solids increases the overall lactose content which contributes to sandiness from crystal formation during freezing. Ultrafiltration removes lactose in the permeate along with some milk minerals. Using ultrafiltration you can increase protein without the side effect of increased lactose concentration and achieve a longer shelf life because of less heat shock in the freeze thaw cycle.
Production of lactose-free, sugar-free or low-carbohydrate Ice cream can be achieved using ultrafiltration in conjunction with diafiltration (addition of water) to remove up to 96% of the lactose found in milk. The final ice cream product can be in the range of less than one gram of carbohydrate per serving in the final product. The addition of a sugar substitute will satisfy the sweet tooth consumer and fill the need of ice cream in the growing "carb-free" dieters market being driven by the successful Atkins and Sugar Buster diets.
1.2 Food Industry
a. Crude Palm Oil (CPO) concentration
Ultrafiltration (UF) is a membrane technology that has been applied for crude palm oil (CPO) degumming. It is considered as an alternative for the conventional CPO degumming technology because of its lower energy consumption, no need for the addition of chemicals, and almost no loss of natural oil. Using UF of the CPO-isopropanol mixture at crude oil concentrations of 30 % and 40 %, we can able to reject more than 99 % phospholipids when the feed temperature is from 30 °C to 45 °C and nearly 93 % phospholipids when the feed temperature is from 40 °C to 45 °C. Industrial regulations expect that high-quality oil must contain more than 95 % neutral TAGs and 0.5 % or less FFA
The crude oil extracted from palm oil fruits is also rich in palmitic acid, β-carotene, and vitamin E, along with some undesirable compounds, such as phospholipids, free fatty acids (FFA), pigments, and proteins5–6. CPO is composed of a vast number of triglycerides (TAGs) and 6 % diglycerides (DAGs) that naturally consist of FFA7 . Industrial regulations expect that high-quality oil must contain more than 95 % neutral TAGs and 0.5 % or less FFA. Industrial regulations expect that high-quality oil must contain more than 95 % neutral Triglyceride (TAGs) and 0.5 % or less Free Fatty Acids (FFA). At high concentration of CPO The large particles that accumulated on the membrane surface and blocked the membrane pores were TAGs.
At low concentrations of CPO, the dominant fouling mechanism was standard blocking, representing small particles attached inside the membrane pore, and causing pore constriction (reduction in pore size). The compound that was possibly blocking the membrane pores was fatty acid, since fatty acids are smaller than phospholipid-isopropanol micelles. At low concentrations of CPO, a sufficient amount of phospholipid-isopropanol micelles was formed, with pore constriction providing high rejection of phospholipids. On the other hand, small molecules, such as fatty acids, can enter the membrane pores.
Ultrafiltration Membrane
Fig 1.4 UF Membranes used in Concentration of CPO
b. Vegetable Oil processing
Membrane separation technology can be substituted into conventional vegetable oil refining to overcome these challenges. SRNF M membranes can be used for the solvent recovery as an alternative to solvent evaporation as well as deacidification stage. Moreover, solvent resistant ultrafiltration membranes with suitable Molecular Weight Cut-Off (MWCO) can be used for efficient separation of phospholipids and the recovery of commercial lecithin from crude oils.
