Most locally produced pasteurized milk in Hong Kong is sold in cartons, plastic bottles or glass packaging. Imported ultra-high temperature (UHT) processed milk using aseptic packaging technologies are also available in the market.
Pasteurization is a milk sterilization process during which raw milk of four degrees Celsius is heated to a temperature range between 72C and 85C for fifteen seconds while homogenization also takes place.
The processed milk is then cooled down to a minimum of 4C and maximum of 0C for further packaging. Dairy products must be delivered and stored below 4.4C to ensure their quality.
The durability is between 12 to 20 days, and 99.99 percent of pathogens such as Salmonella, Escherichia coli and Listeria are killed during pasteurization.
The UHT processing is a technology which treats milk at 139C to 142C for two to four seconds together with homogenization. The UHT-processed milk will be cooled down to room temperature immediately and proceed to aseptic packing directly.
UHT milk can be delivered at room temperature. Their durability is up to 180 to 360 days. Once opened, the product must be stored below 4C and consumed within a few days. UHT processing can kill all bacteria and inhibit reproduction of pathogens.
However, the nutrients in UHT milk are greatly reduced. The texture of UHT milk is also not as good as pasteurized milk. Since UHT milk is easier to be stored and delivered, it is relatively cheaper.
Powdered milk also goes through a high standard processing. Because of its long shelf life, it can withstand long-distance delivery and be made into ice cream, dairy beverages and desserts.
In terms of packaging, carton boxes are the most hygienic option. Plastic bottles are not as eco-friendly because of the material. Glass containers consume a lot of energy during packaging, delivery and storage, and milk in glass containers also has shorter shelf life. The last two types of packaging, it must be said, are not popular among manufacturers.
This article appeared in the Hong Kong Economic Journal on May 14
Translation by John Chui
[Chinese version 中文版]
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