Interest in non-bovine dairy is growing as farmers look for ways to reduce risk in their business. Until recently, most New Zealand sheep and goat milk platforms have tended to be large and far apart.

Animal numbers and milk volumes will typically be low in the early stages of a sheep or goat-milking operation, potentially making processing unfeasible. Smaller milkers have mainly supplied local cheese-makers who may only want to buy milk once a week.

But as more farmers consider milk sheep or goats on a standalone basis, or alongside bovine dairying, there is growing interest in novel ways to store milk for processing and marketing further afield. The aim is to stabilise milk so it can be aggregated into lots for sale, possibly to a processor some distance away.

Some sheep and goat milkers wanting to stabilise their product often resort to freezing milk, perhaps in pails or 2-litre bladders which are stored and transported for domestic use or exported to yoghurt and cheese manufacturers. Using the conventional method of freezing milk (done slowly and in bulk), the quality of milk deteriorates when the frozen milk is stored*.

To help overcome issues with slow bulk freezing, researchers at Massey University and GNS Science, led by Professor Richard Archer, have developed a rapid freezer to enable non-bovine milk to be stored for long periods without jeopardising product quality.

This new rapid freeze technology allows milk to be aggregated until volumes are large enough to be sold for processing. It also allows milk to be stored until a processor needs it.

Professor Archer’s team is investigating how and why freezing milk impacts milk quality, Using the knowledge gained, the aim is to design a simple, affordable freezer system suitable for on-farm use.

They have found that the most important factors for thawed milk quality are speed of freezing, final storage temperature and storage time.

Best quality is achieved when freezing is as fast as possible (within a minute or two), when the frozen milk is kept as cold as possible (below – 20° C) and the storage time is minimised (weeks better than months). Rapid freezing followed by storage at temperatures below -20°C can maintain high milk quality for months, although some kinds of milk product are more sensitive to freeze-thaw than others.

Although the focus of the rapid freezing project is sheep milk, the technology is suitable for other non-bovine milks including goats and deer, and also for non-dairy liquids such as fruit juice/smoothies.

The unit being designed for on-farm or near farm use at the moment is likely to have a 1000L capacity. A day’s product would probably fill ½ bins flat out.

Rapid freeze technology allows farmers to store milk for multiple days.  It also makes it possible to take the freezer to the milk (it works well with a mobile milking platform), so two or three farmers could share a freezer and collect milk over a month, until there is sufficient volume to send to a drier such as the one at FoodWaikato.

Post-freezing product applications would include cheese, powder, yoghurt and ice cream.

Now that the rapid freezing technology is developed, Professor Archer’s team is working with a New Zealand company to develop a freezer that is simple to operate, robust and requires minimal labour input. Ensuring the equipment complies with relevant regulations is also a major consideration.  It is hoped the new freezer will be available for purchase within the next 12 months.

If you are interested in learning more about the rapid freeze technology and its suitability for your farm, please contact Richard Archer (Phone 06 356 9099 extn 84557).

Acknowledgement: The rapid freezing work is being undertaken as part of the Food Industry Enabling Technologies (FIET) project, funded by MBIE.

Written by Tim Fulton on behalf of the Sheep and Goat Milk NZ team. This is based on the article written by Jolin Morel, Lindsay Robertson and Professor Richard Archer, Massey University: School of Food and Advanced Technology, and the Riddett Institute that was published in Goat and Sheep Milk New Zealand (Issue 1) earlier this year.


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