A cooler way to deliver milk

Milk is a staple in most households. But getting it from the dairy factory to supermarket shelves relies on diesel-powered refrigeration systems that burn fuel and generate emissions.

Emeritus Professor Mohammed Farid from the University of Auckland's Faculty of Engineering and Design is developing a cleaner way to keep milk cold on its journey to supermarket shelves.

His portable cooling unit uses panels filled with phase change materials - materials engineered to melt and solidify at precise temperatures, storing and releasing thermal energy to keep conditions steady.

Paired with four small fans and a temperature controller, the unit maintains milk at 4-5 degrees Celsius, the ideal range for preserving quality and shelf life.

"At 5am in the morning, when delivery drivers start loading milk bottles into trucks, they can bring the unit and load it in with the bottles," he explains.

"The fans operate on and off according to the controller in the unit. That controls the coolness and distributes it throughout the truck, helping to keep temperatures steady."

The unit is designed to match the performance of diesel-powered air conditioning units in standard delivery trucks, without the environmental consequences.

The materials are particularly helpful in mitigating fluctuating temperatures when truck doors are opened throughout the day.

"If you don’t control the temperature well, it can really impact the quality of milk," he says.

"You might not see or feel the damage on the mouth, but when you put it in your fridge at home, it may spoil more quickly."

Farid is a world-leader in phase change materials, having worked on the subject for 30 years at the University of Auckland, and for many years prior to that elsewhere.

His spinout company PhaseFoam developed the unit, which is currently being trialled with ELS Distribution, a Takanini-based distributor delivering milk from Fonterra across the country.

Three PhD graduates, Anila Antony, Mehran Shahraeeni , and Ruby-Jean Clark, have been working on the development of this technology.

Trials have been conducted over the summer months to ensure the system can withstand higher temperatures. The testing replicates real delivery conditions, stopping just short of the milk being sold in supermarkets.

Alongside the truck unit, PhaseFoam has also developed thinner 10mm panels designed to absorb heat through repeated door openings.

The concept of minimising food spoilage was first tested in a chilly bin by a group of Farid’s undergraduate students, who monitored carbon dioxide emissions, before later being trialled in industrial refrigerated containers.

While that trial was conducted at a university level and is not yet commercialised, Farid says it demonstrates how phase change materials could be applied more widely to the storage and transportation of chilled foods, including ice cream, yogurt and butter.

Beyond food, he says the same principles could potentially be adapted for pharmaceuticals or chemicals that require similar stable environments.