What Does Ultra High Temperature (UHT) Pasteurization Mean?
Ultra-High-Temperature Pasteurization or Ultra-Pasteurization, is the process where milk and milk products are heated up to 137℃ for 4 seconds and then quickly cooled down. This is done to destroys all the harmful bacteria present in milk and prevent it from contamination. In this blog, you will get an in-depth understanding about the Ultra Pasteurization process in the dairy industry.
What Does UHT Pasteurization Mean?
UHT processing is a continuous flow of heat applied to milk at a higher temperature for a few seconds. Further packed directly into a hermetically sealed container in an aseptic process. UHT processing is also known as Aseptic Processing.
The milk processed using ultra high temperature have a shelf-stable life of two to three months without the need of refrigeration. It has longer shelf as compared to milk which is processed by using regular pasteurization method. UHT Pasteurization retains the nutritional value of milk due to the speed of the pasteurization process.
Ultra-high temperature or Ultra-pasteurization
This method entails heating the milk to 137℃ and maintaining it at this temperature for just 4 seconds using a UHT Sterilizer module. It is then packaged in sterile conditions using an Aseptic Filling Machine. Also, the packaging material is treated using hydrogen peroxide and made sterile. The shelf life thereby extends to 30-90 days.
The UHT treatment process needs special UHT milk processing equipment manufactured by reliable UHT milk processing plant manufacturers. You will need to invest in a correct UHT Sterilizer/Pasteurizer machine to heat the milk to the necessary temperature with the safety guards and quickly cool it down.
There are different sectors that applies UHT in the food processing industry.
UHT Application in Dairy
- White Milk
- Flavoured Milk
- Cream (20% Fat)
- Buttermilk / Lassi
- Milk Shakes
- Soya Milk
- Fruit Juice and Concentrates
Other Than Dairy
- Fruit Juice
- Baby Foods
- Tomato Products
- Vegetable Soups and Stews
Ultra-Pasteurization Process of Milk
While most milk goes through a standard pasteurization process, UHT milk goes through ultra-pasteurization, which safely heats the milk to a higher-than-usual temperature. This, like regular pasteurization, kills bacteria in the milk that may be harmful or cause the milk to spoil, producing milk with a longer life. It’s then packaged in sterilized containers, also known as aseptic packaging, which helps keep the milk fresher longer.
UHT milk can sit out unrefrigerated for about three months until the seal is open. For milk to be considered Ultra Pasteurized, it must be heated to not less than 137° for four seconds. In Ultra Pasteurization method, aseptic processing involves heating the milk using commercially sterile equipment and filling it under aseptic conditions into hermetically sealed packaging.
Steps in a UHT process are
- Preheating
- Homogenization
- Heating to sterilization temperature
- Holding at sterilization temperature
- First Cooling
- Homogenization (alternative position for direct or indirect systems)
- Final Cooling
- Aseptic Packaging
Varying levels of pasteurization include lower to higher temperatures
- Low Temperature, Long Time (LTLT): Milk is heated up to 63℃ and maintained at this degree for 30 minutes. The process lengthens its shelf life to 2-3 weeks.
- High Temperature, Short Time (HTST): At a higher temperature of 72℃. Milk is maintained at this temperature for 15 seconds. With pasteurization, the milk will stay fresh for around 30 days when stored in the fridge.
Methods of UHT Processing
Ultra Pasteurization kills all heat-resistant spore forming bacteria and inactive enzymes and yeasts in milk. Along with this, it also achieves a longer shelf life of milk. Ultra Pasteurization can be done using two processing methods; Direct Heating & Indirect heating.
Direct Heating Systems
The food item is directly exposed to the hot steam under carefully monitored circumstances. A rapid 140°C processing temperature is reached and maintained for 4 seconds. Flash cooling lowers the temperature in a vacuum vessel. The nutritional characteristics won't be impacted by the brief process.
Direct contact with potable or culinary-grade steam heats the product. Direct heating's primary benefit is that the product is kept at the high temperature for a shorter amount of time. This means less damage to milk, that is sensitive to heat. Direct heating systems come in three varieties: electric, injection, and infusion.
Indirect Heating Systems
Food products and steam or refrigerant are separated by a barrier that serves as a heating or cooling medium. One side of the partition allows the heating medium to flow through, while the other side allows food products to pass through the partition plate, which transfers heat. The same thing happens when it cools down. The food product and the heating medium do not come into direct touch during the procedure.
The product's flow rate, the food material's physical characteristics, processing time, and cleaning are all crucial factors to take into account. Equipment contacts surfaces keep the product and heating medium apart rather than in direct contact. The heat exchangers frequently found in food are plate and tubular heat exchangers.
Nutritional Value of UHT Milk
Due to the rapidity of the pasteurization process, milk's flavor and nutritional value are not significantly affected by ultra-high temperature pasteurization. Heating partially denatures whey protein, especially β-lactoglobulin. Denaturing the whey protein, however, has no effect on milk's nutritional content. Additionally, UHT processing can decrease the availability of lysine, an amino acid, by 3.0% to 6.5%, which is regarded as insignificant. It has been established that UHT milk has no effect on body weight or the risk of cardiovascular disease.
Changes Occurred in Milk During UHT
- UHT-Pasteurized Dairy Lasts Longer: The pasteurization prolongs the product’s shelf-life by a few months, leading it to be an extremely cost-effective alternative. It also does not taste the same as regular pasteurized milk, due to the cooked taste acquired by the milk sugars (lactose).
- UHT-Pasteurized Dairy Have Nil Bacteria: The high heat needed during UHT pasteurization causes the milk to be completely bacteria-free. They remain fresh and fit for human consumption only until their seals are broken. Once the packets are open, they need to be refrigerated and consumed as soon as possible.
You might also like: How Do Milk Pasteurizers Help to Keep Milk Fresh?
In conclusion, Determining the right pasteurization process for your dairy product is a complex decision with several variables to consider. You will need to think about the type of product you are pasteurizing, its raw material quality, composition, packaging type, composition, viscosity, the temperature profile expected, the flow rate, and any pressure drops be involved. Having the right UHT pasteurization equipment is necessary to consider this as an option for your needs.