The Importance of Pasteurizing Sheep Milk: What You Need to Know?

Sheep milk has slowly gained popularity in the United States dairy industry. Of the 40,000 estimated dairy farms in the US, only 200 are sheep dairy farms. However, people are learning of the health benefits of sheep milk and the advantages of sheep farming as a whole.

United States law states that sheep milk must be pasteurized to cross state borders. The consumption of unpasteurized sheep milk is legal in most states. However, each state has its own legislation regarding selling raw sheep milk at retail outlets for human and animal consumption.

Sheep milk (and milk from other ruminants) ought to be pasteurized before sale to limit the likelihood of foodborne diseases spreading across the country. Many dairy sheep farmers can consume raw sheep milk on their property. However, it makes more business sense for them to pasteurize it depending on the state in which they live.

Do You Need To Pasteurize Milk From Sheep?

Pasteurized sheep milk is intended for fluid milk or the production of soft products, including cheeses and yogurts. According to the FDA (Food and Drug Administration), Grade "A" sheep milk must be pasteurized before it is sold. The FDA's Primary Milk Ordinance (PMO) specifies the requirements and legalities around all Grade "A" milk that comes from animal or plant origin.

This said, many people enjoy drinking whole, unpasteurized sheep milk, and it is legal to do so in all 50 states. They believe the pasteurization process destroys some of the natural goodness within the milk. Hence, they prefer to drink it raw. Some people use raw milk for their animals, too. However, Michigan is the only state that prohibits the sale of raw milk in any form for animal feed.

While the FDA's PMO doesn't apply to milk gathered and consumed on private premises, it does apply to those selling their milk commercially. Additionally, each state has laws regarding selling unpasteurized sheep milk and other dairy products.

As a commercial dairy sheep farmer, it is in your best interests to pasteurize the milk from your sheep. Sheep milk is gaining popularity, yet the laws surrounding unpasteurized dairy remain stringent. In addition, by pasteurizing your sheep milk, you will expand your market considerably. For example, you could sell your sheep's milk beyond the borders of your state.

A Glance At State Laws Regarding The Sale Of Raw Sheep Milk

Under the United States Federal Regulation 21 CFR § 1240.61, the interstate distribution and sale of raw (unpasteurized) milk is prohibited. PMO regulations and individual state regulations on raw milk are broadly summarized below:

Since April 2016, only 13 states have allowed the sale of whole raw milk in retail stores. They are the following:

• Arizona,
• California,
• Connecticut,
• Idaho,
• Maine,
• Nevada,
• New Hampshire,
• New Mexico,
• Oregon (only raw sheep and goat milk may be sold, not cow's milk),
• Pennsylvania,
• South Carolina,
• Utah (where the dairy farmer must own the retail outlet in question), and
• Washington.

Seventeen states permit the sale of unpasteurized milk only on the farm on which it was produced. They are:

• Arkansas,
• Illinois,
• Kentucky (excluding cow's milk),
• Kansas,
• Massachusetts,
• Minnesota,
• Mississippi (excluding cow's milk),
• Missouri (delivery of raw milk directly to consumers is also allowed),
• Nebraska,
• New York,
• Oklahoma,
• Rhode Island (excluding cow's milk),
• South Dakota (delivery of raw milk directly to consumers is also allowed),
• Texas,
• Vermont (delivery of raw milk directly to consumers is also allowed),
• Wisconsin, and
• Wyoming (delivery of raw milk directly to consumers is also allowed).

Eight states only allow the onsite sale of unpasteurized sheep milk through "herd-share" agreements. They are as follows:

• Alaska,
• Colorado,
• Michigan,
• North Dakota,
• Ohio,
• Tennessee,
• Virginia,
• West Virginia.

Why Pasteurizing Sheep Milk Is Required By The FDA?

Raw produce, including sheep milk, is a potential source of dangerous bacteria and microorganisms. In the "right" conditions, harmful bacteria can multiply to hazardous toxicity levels and pose a severe health risk to susceptible consumers. For example, many illness outbreaks in the United States have been traced back to raw milk brimming with pathogenic bacteria.

For example, the CDC (Centers for Disease Control and Prevention) reported 127 outbreaks linked to the consumption of raw milk products between 1993 and 2012. The outbreaks are often incorrectly assumed to be food poisoning, and the affected parties are diagnosed too late.

Some examples of pathogenic bacteria found in produce, including dairy, include E. Coli, Listeria, Staphylococcus, Campylobacter, and Salmonella. These foodborne diseases are particularly harmful (or fatal) to developing children, pregnant women, older adults, and people with compromised immune systems, e.g., people with cancer or HIV/AIDS.

Pasteurization also reduces the number of microorganisms found naturally in milk. If left unchecked, these microorganisms alter the taste of the milk and shorten its shelf-life.

Therefore, the FDA recommends that all milk be pasteurized, whether on a commercial scale or at home. Additionally, the pasteurization process has only minor effects on the taste and nutritional value of the milk.

Home pasteurization involves heating raw milk slowly to a specific temperature (165°F) to kill off most of the microorganisms in raw sheep milk. Then after 15 seconds at that temperature, the milk must be cooled down rapidly and stored in a clean container in the refrigerator to prevent further growth.

But how do commercial dairies pasteurize sheep milk? The process is the same as pasteurizing cow's milk, except that sheep's milk is already homogenized, whereas cow's milk is not. Therefore, some dairies might skip the separating and homogenizing parts of the process outlined later.

How Is Sheep Milk Pasteurized On A Commercial Scale?

Sheep milk production differs from cow and goat milk production in its seasonal nature. Depending on the dairy sheep, season, and farming practice employed, the dairy sheep might only produce milk for six months of the year. In addition, since sheep milk is fattier than many other kinds of milk, it is more vulnerable to attack from pathogenic microorganisms.

Raw sheep milk should be drawn using sterilized equipment and cooled promptly to maintain good quality. Doing so will slow down microbial growth and the enzymes in the milk, e.g., proteases and lipases.

Then, before pasteurizing the raw sheep milk, all equipment for transfer, holding, and pasteurizing the milk must be sterilized. Doing so will prevent microbial growth within the equipment. It doesn't help to pasteurize milk in a pasteurizer that is riddled with pathogens. So, cleaning a pasteurizer thoroughly before and after each use is recommended.

Additionally, feed shouldn't be kept in the milking area because of the dust and spores from yeast it might release. The spores can settle on the fatty sheep milk and spoil a whole batch of milk or cause foodborne illness further down the consumer chain.

How To Clean A Sheep Dairy Pasteurizer?

The pasteurizer should be thoroughly cleaned before running sheep milk through it. The cleaning process should wash out any sediment and sterilize the equipment, inside and out.

• Step 1: Rinse the entire pasteurizing unit with warm or tepid water. Let the water runoff as wastewater.
• Step 2: Run a cycle with a suitable acidic cleaner or acid-boiling water to break down sediment.
• Step 3: Rinse the acidic cleaner with clean, chlorinated water (not untreated), and allow it to dry thoroughly. The water source should be tested for contaminants, and the final rinse should be with chlorinated water.
• Step 4: Remove the milk stone (a buildup of milky grime) at least once a month.

How A Commercial Milk Pasteurizer Works?

According to the PMO, raw sheep milk can be stored at refrigeration temperature for 72 hours before it is pasteurized. The ideal temperature for the cooling milk silos is about 39.2°F, but it must be below 42.96°F.

The commercial dairy pasteurizing process is much more intricate than the double-boiler you'd use for home pasteurizing. Simply put, this is what commercial milk pasteurization entails:

1. The Milk Is Tested

The milk is tested before it is collected at the farm and when it arrives at the dairy. This is to see the extent of microbial growth during transit and if it contains antibiotics.

Additional tests include checking the Somatic Cell Count (SCC) within ruminants' milk. Ruminants with infected mammary glands will have a higher SCC, so it's a way to test if the milk is healthy or infected.

2. The Skimmed Milk And Cream Are Separated

Since the fat content of milk varies between breeds, the milk is separated from the cream using a centrifugal separator. The whole raw milk is placed in the centrifuge machine. The machine spins quickly, separating the skimmed milk and the cream. The cream is directed to one section of the pasteurizer, while the skimmed milk is directed to the next section.

3. Some Cream Is Mixed Back Into The Skimmed Milk

While it seems strange to separate the cream and then reintroduce it, there is a valid reason to do so. Only a certain percentage of cream will be reintroduced based on the desired level, e.g., 1%, 2%, or full-cream milk. This is to create standardization in the end product for consumers, as the percentage of cream in sheep milk is not always the same.

4. The Milk Is Homogenized

Homogenization evenly distributes the cream throughout the milk, whereas it would typically separate otherwise. During the homogenization stage, the milk is forced through a tiny gap or mesh in the homogenizer. In this process, the larger fat droplets are broken into smaller droplets, making them less likely to rise to the surface of the milk.

5. The Homogenized Milk Is Then Pasteurized

The milk is pasteurized in a heat exchanger to make it safe to drink. Then, the milk is quickly heated and cooled to destroy microorganisms and harmful bacteria. For example, one pasteurization process entails the milk being heated to a minimum of 161.6°F for 15 seconds.

Heating the milk to 284°F for one to four seconds will kill even more heat-resistant spores, thereby lengthening the shelf-life of the milk. Milk pasteurized at this temperature will last for months, unopened and unrefrigerated.

6. The Milk Is Packaged

The last step of the pasteurization process requires the milk to be packaged under strict hygienic conditions. Otherwise, the pasteurization process would be a waste of time.

The packaging must protect the milk from light, oxygen, and recontamination by microorganisms. Milk cartons are usually made with a cardboard structure lined inside and outside with plant-based polymers.

Different Types Of Heat Treatment For Milk Pasteurization

There are different ways to pasteurize milk commercially. Each has its own benefits in terms of extending the shelf-life of milk. However, all forms of commercial pasteurization kill 99.9% of disease-causing organisms.

They are summarized in the table below.

Table 1: Different Types of Milk Pasteurization on a Commercial Scale

Conclusion

For the budding dairy sheep farmer, it is an excellent idea to invest in an onsite pasteurizing setup or sell sheep milk to a more extensive dairy. Even though it adds to the production costs, the safety measures will protect consumers from potential foodborne diseases. Additionally, it might save the farmer a lot in legal fees if they are sued for damages or medical bills.

Sources:

FDA: Grade "A" Pasteurized Milk Ordinance

ProCon.org: State-by-State Raw Milk Laws

North Dakota Legislative Branch: State-by-State Raw Milk Laws 2016 Update

FDA: The Dangers of Raw Milk: Unpasteurized Milk Can Pose a Serious Health Risk

OregonState.edu: Food Safety & Preservation: Home Pasteurization of Raw Milk

ResearchGate: Processing of Sheep Milk

Science Direct: Sheep Milk

Science Direct: Pasteurized Milk