pasteurisation

Milk from the farm to the table

/ dairymilkmaid / Leave a comment

Ever wanted to know what happens to milk between the farm and your glass? This lightly edited story from the Gippsland Murray Goulburn newsletter explains it all really well.

Separation and standardisation
Separation of animal milk, be it goat, sheep or cow is a naturally occurring phenomenon, which has been observed and tinkered with by man for many centuries. Indeed, as recently as the mid-1900s, milk was separated on farm and consigned as cream in cans to the dairy processor, with the whey by-product being fed to the farm’s pigs (MMM note: We had cream cans until the early 1960s when power finally arrived here and a refrigerated vat took their place).

These days, separation of cream from skim milk is done via multi-level centrifugal force separators in a process refined in 1879…Cream, which is lighter than milk, is driven by centrifugal force (MMM note: the same “spinning” force that pushes water out of clothes during the spin cycle of your washing machine) to the surface of the milk and flows off to a holding vessel. Standardisation of milk involves the adjustment of the fat content by addition of cream or skim milk as appropriate.

Pasteurisation
Along with correct cooling, pasteurisation is one of the most important processes in the treatment of milk. If carried out correctly, this process will supply milk with a longer shelf life. Simply, the process of pasteurisation is to heat milk to 70-75 degrees C but for only five to seven seconds, upon which most bacteria will be killed.

Ultra High Temperature (UHT)
Like pasteurisation, UHT treatment is heat treating milk for a given time at a given temperature…UHT takes the temperature to 135-140 degrees C but only for five to seven seconds. Importantly, the UHT process for milk is a continuous, aseptic (fully enclosed and sterile) treatment and packaging process. Shelf life of six months or more can be obtained if the milk is of the highest quality.

Homogenisation
Homogenisation is a process invented in 1899 to stabilise fat emulsion against gravity separation. Essentially, milk is forced through a small passage at great velocity, causing the fat globules to fracture into much smaller ones. The newly-created fat globules will stay free and more stable and be less likely to separate out. This process will also enhance whiteness, flavour and mouth-feel of the milk. The downside of homogenised milk is its restriction in other processes such as cheese making. Also, the product is more susceptible to light damage.

There’s a bit more to the article, including a discussion of ghee, milk powder, casein and yoghurt – topics for other days!

About raw milk products

/ dairymilkmaid / 11 Comments
Farmstead cheese

Photographer: Michael Robinson, pic courtesy of Cheese Slices

Did you know there is such a thing as “Real Milk Activism”? These activists believe the only real milk is unpasteurised milk.

Currently, it is illegal in Australia to sell unpasteurised “raw” milk but Food Standards Australia New Zealand (FSANZ) is conducting a review that could (although it is unlikely, I suspect) see it hit the shelves.

Milk has caused very little illness in Australia over the past decade. According to the FSANZ paper A Risk Profile of Dairy Products in Australia:

Microbiological survey data for pasteurised dairy products in Australia show a very low incidence of hazards of public health significance in these products. Overseas data demonstrates that pathogens are frequently isolated from raw milk and raw milk products. Pathogens were detected in raw milk in 85% of 126 surveys identified in the literature.

In surveys of raw milk cheese pathogens were rarely detected. Pathogens are found infrequently in pasteurised milk and pasteurised milk products.

In Australia, illness from dairy products is rare. Between 1995-2004, there were only eleven reported outbreaks directly attributed to dairy products, eight of which were associated with consumption of unpasteurised milk. In other Australian outbreaks, dairy products were an ingredient of the responsible food vehicle identified as the source of infection. However,
dairy products are a component of many foods and it is often difficult to attribute the cause of an outbreak to a particular food ingredient. Microbiological survey data for pasteurised dairy products in Australia show a very low incidence of hazards of public health significance in these products.

While commercial dairy products have rarely been identified as sources of food-borne illness in Australia, there have been a number of reports of outbreaks associated with consumption of dairy products internationally. Unpasteurised dairy products are the most common cause of these dairy-associated outbreaks of illness.

Among the risks that are neutralised by pasteurisation are salmonella, listeria and e coli.

Raw milk cheeses may be on their way

FSANZ recently recommended permission for non-pasteurised hard to very hard cooked curd cheeses on the provision that there are new processing requirements for cheese production that state storage time, and moisture content requirements for these cheeses to ensure product safety.

FSANZ says it will “continue to look at permissions for other raw milk cheeses through a new proposal that will use the technical work already undertaken under P1007”.

Prominent cheese officionado, Will Studd, says the changes will be insignificant.

Raw drinking milk to remain illegal in Australia
In the words of the FSANZ:

The assessment work for P1007 concluded that raw drinking milk presents too high a risk to consider any permission in the Code. In the new proposal, FSANZ will be reviewing the current exemption that allows raw goat milk.

For raw drinking milk, even extremely good hygiene procedures won’t ensure dangerous pathogens aren’t present. Complications from bacteria that can contaminate these products can be extremely severe, such as haemolytic uraemic syndrome (HUS) which can result in renal failure and death in otherwise healthy people.

People with increased vulnerability to diseases caused by these bacteria include young children, elderly people, people with compromised immune systems and pregnant women and their foetuses.

What if a farmer sells you raw milk?

I wouldn’t ever sell it to you. I would lose my dairy farmer’s licence and face five-figure fines, as one man did for selling raw milk for “cosmetic purposes” earlier this year. Worse still,  I couldn’t live with myself if, despite our best efforts to deliver clean milk, one of your children fell ill. Sure, we drank it as kids with no ill-effects and the risks are low but they are there and it is illegal.

Even after pasteurisation, milk is one of nature’s superfoods. Drink it, enjoy it and let your children thrive on it.

By the way, for a good discussion of the raw milk cheese debate, check out the Food Sage blog.

About UHT milk

/ dairymilkmaid / 7 Comments

Here’s an interesting AAP newswire story about UHT:

Despite the supermarket heavyweight’s price war on fresh milk, sales of UHT milk are on the rise and now account for nearly 10 per cent of total milk sales. However, statistics from Dairy Australia show that most Australians still prefer fresh milk on their cereal.

UHT milk sales increased eight per cent from 195 million litres to 211 million litres in 2009/2010 over the year before, accounting for 9.3 per cent of total milk sales for the same period.

Associate Professor Frank Zumbo of the University of NSW, said the rise of UHT milk sales was currently not a threat to the big supermarkets as the long life product was low maintenance and did not require refrigeration costs.

“If the trend continued, it would be troubling, but at the moment it’s clear consumers have a strong preference for fresh milk,” he said.

The number was off a low base, where UHT had traditionally had a very low percentage of the market, he told reporters on Friday.

“But we are seeing the owners of UHT brands trying to lift their profile through increased advertising.”

A survey of 2,500 milk drinkers by consumer research centre Canstar Blue found that out of all Australians who had purchased milk in the past six months, those drinking Devondale UHT milk said they were happier than consumers of other brands, based on overall satisfaction, taste, health benefits and packaging.

Canstar Blue manager Rebecca Logan said the results were surprising, given the attractive prices offered by major supermarkets on fresh milk.

“There’s no doubt long life milk has come a long way over the years and consumers are responding to its convenience and long shelf life,” Logan said in a statement on Friday.

The average Australian drinks 102 litres of milk a year, according to Australian Dairy Farmers.

So, what is UHT milk?

UHT stands for Ultra-High Temperature and refers to the pasteurisation process – the heating of milk to ensure it is free from nasty bugs. Rather than being heated at 74 degrees Celsius for about 15 seconds, it is heated at about 140 degrees Celsius for just two seconds.

There is little nutritional difference between “fresh” and “long life” milk and according to Curtin University scientists, UHT milk is more environmentally-friendly than “fresh” milk.

Which milk do we drink at the farm?

I’m often asked whether we drink milk straight from the vat. Well, no, actually we drink Devondale UHT milk, which is where some of our milk ends up, anyhow. It’s safer than raw milk and easier to get out of the pantry than out of a 17,500 litre vat!