“UHT processing is being used increasingly for heat-treating milk, as the shelf-life is extended from days to months, and UHT milk can be stored and transported without refrigeration.”
The basis of UHT, or ultra-high temperature, is the sterilization of food before packaging, then filling into pre-sterilized containers in a sterile atmosphere. UHT technology has been widely used in the dairy industry worldwide and is becoming increasingly popular across a range of product segments. This process enables the production of quality shelf stable liquid products, optimizing nutrition, flavour and functional benefits. It is also inexpensive and cost-effective compared to many other food processing technologies.
Advantages of UHT Processing
1. High Quality
2. Longer Shelf Life
3. Processing Conditions independent of container size
Application of UHT
These are wide ranging and include: milk and any milk based beverage, cream, custard, puddings, dairy dessert, caramel sauce, cheese sauce, vegetable purée, soups and broths, juices and fruit pulps, soy milk and nut milks, etc.
How does it work?
There are two principal methods of UHT treatment:
1. Direct Heating
2. Indirect Heating
Direct Heating System
The product is heated by direct contact with steam of potable or culinary quality. The main advantage of direct heating is that the product is held at the elevated temperature for a shorter period of time. For a heat-sensitive product such as milk, this means less damage.
“Many products that are UHT heat treated are not aseptically packaged. They do have the advantage of a longer shelf life at refrigeration temperatures compared to pasteurization, but they are not shelf stable at the ambient temperatures, due to the possibility of recontamination post processing. “
There are 5 basic types of aseptic packaging lines:
• Fill and seal: preformed containers made of thermoformed plastic, glass or metal are sterilized, filled in aseptic environment, and sealed
• Form, fill and seal: roll of material is sterilized, formed in sterile environment, filled, sealed e.g. tetrapak
• Erect, fill and seal: using knocked-down blanks, erected, sterilized, filled, sealed. e.g. gable-top cartons, cambri-bloc
• Thermoform, fill, sealed roll stock sterilized thermoformed, filled, sealed aseptically. e.g. creamers, plastic soup cans
• Blow mold, fill, seal
Indirect Heating System
The heating medium and product are not in direct contact, but separated by equipment contact surfaces. Plate heat exchanger, tubular heat exchanger, scraped surface heat exchanger are some of the heat exchangers commonly used in food industry.
Packaging for UHT processed food products
When the UHT process is coupled with aseptic filling equipment, there is little risk for post-processing environmental contamination, and the expiration date on these products can be 6-12 months at room temperature in your pantry or on the store shelves.
There are several different package forms that are used in aseptic UHT processing:
• flexible pouches
• thermoformed plastic containers
• flow molded containers
• bulk totes