UHT (ultra-high temperature) MILK MANUFACTURING PROCESS

UHT (ultra-high temperature) MILK MANUFACTURING PROCESS :

UHT (ultra-high temperature) Milk

Ultra-high temperature processing (UHT), ultra-heat treatment, or ultra-pasteurization is a food processing technology that sterilizes liquid food by heating it above 135 °C (275 °F) – the temperature required to kill bacterial endospores – for 2 to 5 seconds . UHT is most commonly used in milk production (can be stored 6 months at room temperature) , but the process is also used for fruit juices, cream, soy milk, yogurt, wine, soups, honey, and stews. UHT milk was first developed in the 1960s and became generally available for consumption in the 1970s.

The heat used during the UHT process can cause Maillard browning and change the taste and smell of dairy products. An alternative process is HTST pasteurization (high temperature/short time) , in which the milk is heated to 72 °C (162 °F) for at least 15 seconds.

UHT milk packaged in a sterile container, if not opened, has a typical unrefrigerated shelf life of six to nine months. In contrast, HTST pasteurized milk has a shelf life of about two weeks from processing, or about one week from being put on sale. A significant percentage of milk sold in the US as organic food is UHT treated.

Technology :

     Ultra-high-temperature processing is performed in complex production plants, which perform several stages of food processing and packaging automatically and in succession:

• Flash heating
• Flash cooling
• Homogenization
• Aseptic packaging

In the heating stage, the treated liquid is first pre-heated to a noncritical temperature (70–80 °C [158–176 °F] for milk), and then quickly heated to the temperature required by the process. There are two types of heating technologies: direct, where the product is put in a direct contact with the hot steam, and indirect, where the product and the heating medium remain separated by the equipment's contact surfaces. The main goals of the design, both from product quality and from efficiency standpoints, are to maintain the high product temperature for the shortest period possible, and to ensure that the temperature is evenly distributed throughout.

Direct heating systems: 

Direct systems have the advantage that the product is held at a high temperature for a shorter period of time, thereby reducing the thermal damage for the sensitive products such as milk. There are two groups of direct systems:

• Injection-based, where the high-pressure steam is injected into the liquid. It allows fast heating and cooling, but is only suitable for some products. As the product comes in contact with the hot nozzle, there is a possibility of local overheating.
• Infusion-based, where the liquid is pumped through a nozzle into a chamber with high-pressure steam at a relatively low concentration, providing a large surface contact area. This method achieves near-instantaneous heating and cooling and even distribution of temperature, avoiding local overheating. It is suitable for liquids of both low and high viscosity.

Indirect heating systems :

In indirect systems, the product is heated by a solid heat exchanger similar to those used for pasteurization. However, as higher temperatures are applied, it is necessary to employ higher pressures in order to prevent boiling. There are three types of exchangers in use:

• Plate exchangers,
• Tubular exchangers
• Scraped-surface exchangers.

For higher efficiency, pressurized water or steam is used as the medium for heating the exchangers themselves, accompanied with a regeneration unit which allows reuse of the medium and energy saving.

Flash cooling :

After heating, the hot product is passed to a holding tube and then to a vacuum chamber, where it suddenly loses the temperature and vaporizes. The process, referred to as flash cooling, reduces the risk of thermal damage, removes some or all of the excess water obtained through the contact with steam, and removes some of the volatile compounds which negatively affect the product quality. Cooling rate and the quantity of water removed is determined by the level of vacuum, which must be carefully calibrated.

Homogenization :

Homogenization is part of the process specifically for milk. Homogenization is a mechanical treatment which results in a reduction of the size, and an increase in the number and total surface area, of fat globules in the milk. This reduces milk's tendency to form cream at the surface, and on contact with containers enhances its stability and makes it more palatable for consumers.

Aseptic packaging : (Tetra Pack)

Aseptic Packaging is a specialized manufacturing process in which milk, food, pharmaceutical, or other contents are sterilized separately from packaging. The contents are then inserted into the container in a sterile environment. This method uses extremely high temperatures to maintain the freshness of the contents while also ensuring that it’s not contaminated with microorganisms. Aseptic packaging materials Several materials are layered together to provide the level of protection required for aseptic packaging standards, including:

Polyethylene is used as a barrier on the inner and outer sides of aseptic packaging. These layers protect against moisture entering or exiting the container. Film foil helps preserve the product by keeping light and oxygen out. Packing for milk (Polyethylene (gaurds moisture) + paperboard (strength and stability)+Polyethylene (adhesive)+ aluminium (light, air, odour barrier)+ Polyethylene (adhesive) + Polyethylene (Seals in the flavour)

Advantages of aseptic packaging :

Increased shelf life : Aseptic packaging helps increase shelf life for select products by an estimated six to 12 months without refrigeration. The increased longevity of a product’s lifespan gives manufactures more time to sell their product on retailers’ shelves, and it provides the consumer with more time to use or eat the product before it expires.

Reduced shipping and distribution costs : With the unique materials used in aseptic packaging, select products can be stored at ambient temperatures (approximately 68-77 degrees Fahrenheit). Additionally, aseptic packaging is lightweight and compact when compared to more traditional packaging types. These properties allow manufacturers to cut back on shipping costs by reducing shipping weight and eliminating the need to refrigerate products that would typically require cooler environments during distribution.

No preservatives required : Manufacturers don’t need to use preservatives with the use of aseptic packaging because the sterilization process protects against bacteria. This allows manufacturers to use real ingredients that consumers prefer.

Eco-friendly : Aseptic packaging is a sustainable method that can contribute to a manufacturer’s “Go Green” initiative. The packaging is primarily comprised of renewable resources and uses approximately 60% less plastic than other options. Aseptic packaging also requires less energy to manufacture

Maintains quality of contents : The high-tech aseptic packaging process helps preserve the overall quality of most food products. That means taste, smell, and even nutritional value will not be compromised and consumers can be confident that the product they purchase will be of high quality.

Process:  Collected Milk (From Farmers and Milk collection centers) is brought to the Plant by Milk Tankers===> Milk samples are taken and tested (Quality and Fat Content in LAB)===> After testing Signal is sent to unload the Milk Tanker====> Raw Milk is Stored in big storage tanks (Silos) ====> Milk from Silos is sent to the Plant for pre-treatment ===> Milk goes Through a chiller Bacteria Removal Clarifier once its is passed through the clarification process it is sent To Pasteurization Process ===> in Pasteurization Process milk  is heated to 72.5 degree centigrade for 15 seconds and cooled/chilled back to 4 degree centigrade to remove all the bacteria present in the raw milk  is sent to the storage tanks (Silos) ===> milk from this section goes to the  heat exchanger or ultra high temperature  section (UHT Section) where milk is given a temperature of about 135 to 140 °C (flash heating) and then it is cooled/ temperature is brought down to 20 to 35°C  which  kills all bacterial part remaining (milk has same nutritive value as packed milk)===> milk is standardized and pre-heated sent to  the homogenizer ===>   after the Homogenization process the milk is sent to the packing unit where they are packed with the Aseptic packaging : (Tetra Pack) technology with the help of automation technology and further stored in the cold storage plant till they are dispatched.

Actual working can be seen in the link attached:

https://youtu.be/h1Xp7p1taW0?list=PLCXHbldQAnixT25Z3aSghNIYWWXH4_CC4