Ensuring Milk Quality: A Comprehensive Guide to Milk Testing Equipment

By Dairy Farming Hut

Cows, Goats, Sheep

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One of the essential things dairy farmers should do is test the quality of the milk they produce. So many factors could go wrong and adversely affect the milk, which could lead to severe health risks. That’s why the government controls milk production so strictly. So, how can you test the quality of your milk, and what kind of milk testing equipment is generally used?

The essential equipment you need to test the quality of your milk are bacteria counters, refractometers, fat meters, pH meters, somatic cell counters, and lactose meters. Some variations exist on the basic tools; for example, rapid testers can give instant results in some cases.

Selling bad quality milk can harm your customers and hurt your business and reputation. That’s why it’s vital to get the right tools and use the correct methods to confirm the quality of your milk. Let’s look at the factors a dairy farmer should test and find some tools and equipment you can use to ensure the milk’s quality.

Bacterial Count Tests On Milk

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Bacterial count tests are arguably one of the most vital tests for a dairy farmer to perform. These tests count the number of bacteria present in the milk they produce. It isn’t possible to eliminate bacteria entirely, and you wouldn’t want to because there are good bacteria in milk as well.

However, it is crucial to ensure that there aren’t too many harmful bacteria in the milk you produce because high quantities of harmful bacteria can cause several problems, like:

  1. It could cause the milk to spoil sooner than it should. Milk spoilage, in general, is caused by the rapid growth and spreading of bacterial colonies, especially bacillus cereus. That’s why it’s vital to identify if the presence of this bacterium (and others like it) is too high so that the milk won’t spoil too soon.
  2. Some of the bacteria in milk could cause foodborne illnesses like salmonella, listeria, and E. coli. These bacteria could cause severe illness and even death, so you must detect them before they spread from your dairy farm.

How To Perform Bacterial Count Tests?

There are two popular types of bacterial count tests. Both are effective, and many dairy farms use these tests. They are:

  • The SPC Test: SPC stands for “standard plate count,” and it’s the simplest of the two tests, though it’s far from simple. It would be best to use a petri dish to grow bacteria from a milk sample. Once the colonies have grown, you count the number of colonies to determine how many types of bacteria are present in the milk.
  • The TBC Test: TBC stands for “total bacterial count.” It uses a liquid culture medium and bacterial incubator to grow the bacteria outside of a petri dish, after which the turbidity of the liquid is measured to determine how many bacterial colonies are present in the milk.

Of the two, the SPC test is easier to do and requires less equipment. However, most professionals consider the TBC test to be the more reliable of the two tests since it can detect more different types of bacteria, including ones that won’t grow in a petri dish.

Rapid Bacteria Test

There is a rapid testing method that detects the metabolic activity of living cells in milk called the Resazurin test. Whereas SPC and TBC tests usually take approximately 48 hours, the resazurin test could give results in as little as 10 minutes to three hours.

To perform a Resazurin test, you dissolve a tablet of dye in a glass of distilled water, which you then mix with a milk sample. The milk should change to a blue color. After a while, the color will begin to fade due to how the bacteria metabolize and destroy the dye.

You can determine the milk’s general safety by comparing the milk’s color to a color chart after the allotted time. If the milk is too faded, it’s not considered safe for consumption.

Though the Resazurin test is accepted by many health, food, and agriculture associations, it’s not considered to be as effective as SPC and TBC tests, mainly because it only gives a general safety guideline instead of indicating how many bacteria are present in the milk. It's typically used as a screening test in dairy processing facilities to determine if further testing or processing steps are required to ensure milk safety and quality.

Somatic Cell Tests In Milk

Another approach to testing, if milk is safe for consumption, is called the somatic cell test.

Somatic cells are white blood cells. One of the primary purposes of white blood cells is to remove infection and disease from the body. So, if the milk contains too many white blood cells, it most likely indicates that the cow has an infection or inflammation in its mammary glands.

Apart from the obvious health risks this poses, it could also adversely affect the milk's taste, smell, and general quality.

Somatic Cell Counters

The equipment dairy farmers and laboratories use to perform somatic cell tests are called Somatic Cell Counters. These sophisticated machines are not easy to operate and definitely not cheap.

Lactoscan Somatic Cell Counter

Farmers pour a sample of milk through a small hole in the machine, after which it goes through the testing process. Some devices could take a few hours before they will give complete results to indicate if the somatic cells present in the milk are within safe limits or not.

Most modern somatic cell counters have built-in microscopes that trained staff can use to confirm if the test results are accurate.

Rapid Somatic Cell Counting Options

Though somatic cell counting doesn't take very long, the machines are so technical and impractical for all but the largest dairy farms that most farms must ship samples to dedicated laboratories for testing. This causes severe delays.

For that reason, many dairies prefer to use one of two rapid tests that they can perform on-site and only occasionally do detailed somatic cell counts. The two rapid-testing methods are:

  • PortaSCC: This patented product is based on simple strips that change color within 45 minutes after being exposed to a milk sample. The color of the strip can then be compared with a provided color chart to test if the milk is safe or not.
  • Handheld Cell Counter: These small handheld devices can return the results of a somatic cell count within minutes with a high level of accuracy.

These tests are practical, though they are not a replacement for complete somatic cell counts. There's also plenty of preparation that you must do before you can use rapid tests. For example, fat cells can quickly interfere with the readings and results, so you should remove most of the fat cells from the sample before using them.

Thankfully, both tests come with detailed instructions on preparing your samples for testing, and the rapid tests can help smaller dairy farms get basic somatic cell tests done without third-party involvement.

Acid-Base (pH) Tests For Milk

pH tests determine how acidic a milk sample is. High acidity levels indicate the presence of a high concentration of lactic acid, which generally shows high bacterial deterioration. When the lactic acid content of milk gets too high, it will eventually thicken and curdle, so high acidity (a low pH reading) means the milk is close to spoiling.

High pH (in other words, low acidity) in milk isn't a good thing, either. It indicates that the cows could be infected with mastitis. This happens because the infection causes the cows' immune systems to release chemicals like histamine, leading to higher blood levels, which causes more alkaline presence in the milk since blood plasma has high alkaline content.

Even though somatic cell counts give a more reliable indication that a cow might be infected with mastitis, pH tests are simple, quick, and affordable ways to screen for such infections.

Milk should generally test between 6.6 and 6.8 pH. Any reading higher than that could indicate the presence of mastitis, while a lower reading usually means that the milk is close to spoiling.

pH Testing Equipment

The Acid-Base test is perhaps the easiest and most affordable for a dairy farm of any size since you can pick up pH testers almost anywhere. Be sure to get one rated for liquids and preferably specifically for milk to ensure accuracy.

The pH tester has a metallic probe that you can insert into the milk sample. The probe measures the voltage that's generated by the hydrogen ions in the milk, which gives it an indication of the acidity or alkalinity (pH) level.

The test usually takes only a few seconds, but it's not a bad idea to sanitize the probe and redo the test to be sure. Accuracy can often be unpredictable, especially when the device's battery needs replacing.

Apera Instruments Value Series PH850-DP Portable pH Meter Kit for Dairy Products and Liquid Food
  • Equipped with Swiss LabSen 823 pH/temp Electrode designed for dairy products and liquid food e.g. milk, yogurt, sauce, jam, etc.
  • Automatic multi-point calibration with slope data display, an indicator of your pH electrode’s condition
  • Built-in temperature sensor enables automatic temperature compensation
  • IP57 rugged structure design for in-field use and the foldable stand supports use as a benchtop meter.
  • Self-diagnosis ensures the meter will be properly calibrated and guides you on how to fix common problems

Fat And Protein Tests

These tests have less to do with the safety of the milk and more with the quality and nutritional value. There are various tests that dairy farmers can do, often directly at the farm, to see if their milk is of high enough quality to meet the standards set by the government and the buyers. The tests check the number of solids in the milk to give their results. In particular, they look for the following:

Fat Count

Higher fat content in milk is seen as an indicator of high-quality milk. That's because fatty acids are essential nutrients that humans and animals need to live, and part of the reason why we consume milk in the first place.

That might sound contradictory to health advice of the last few decades, but modern research has shown that fatty milk can be healthier and isn't the major contributor to heart disease that many think it is.

On the contrary, the fat content in milk helps our bodies better absorb the other nutrients contained in milk, like vitamins A, E, and D. This is so significant that manufacturers often have to add vitamins A and D to low-fat and skim milk to boost its nutritional value or supplement the milk with Omega-3 fatty acids to accommodate for the lack of natural fat.

The fat content in one milking session will differ. The first milk drawn from the cow will have lower fat content; as the milking proceeds, this level increases. So farmers should never test only a sample drawn at the beginning or the end. Test an overall sample after milking, instead.

Protein Count

The protein count is also vital as it's one of the crucial nutrients contained in milk. Because of this, a higher protein count is an essential indicator of higher-quality milk.

Apart from its nutritional value, research published in the National Library of Medicine indicates that milk proteins are essential for the following reasons:

  • Milk proteins prevent or delay the development of cancer
  • They have immunomodulatory aspects, which means they can help the body fight against infection and disease
  • They help to kill microorganisms, like bacteria or mold
  • Milk proteins help prevent tooth decay
  • They can help lower blood pressure
  • They can actually help combat bad cholesterol, thereby fighting heart disease.

Now that we know higher fat and protein counts equate to better quality milk, we can look at the different devices, tools, and methods you can use to test it.

Centrifuge Tests

A centrifuge is a popular laboratory device used to separate the contents of liquids from their base. Scientists often use centrifuges to test blood samples, but they can be just as helpful in testing milk quality. A centrifuge separates the solid components, like fat and protein, from the liquid base of the milk, after which the fat and protein content from the sample can be measured.

There are two specific pieces of equipment you will need to do this test:

This test is also known as the Gerber Method. It's been around since the 1890s after Dr. Niklaus Gerber developed it in Switzerland, and the method is still the accepted standard in the United States, Europe, and much of the world.

ONiLAB Lab PRP Benchtop Centrifuge 6x15mL/10mL/7mL/1.5-5ml, 300-5000rpm(Max. 2600xg RCF),LCD Digital Desktop Lab Centrifuge Timer 30sec-99min, Two Quick Start Programs
  • Easy to use and quite operation – Timer rang 30sec-99min or without limit (continuous running). Rotor speed can be set and displayed by RPM or G-force. Defined program by knob will be stored and activated when power on; Two programs P1/P2 for choose, easy to start the procedure by one key. Easy-to-read processing display and sound alert. Automatic lid-lock release after running; Noise≤56dB
  • Safety – Door lid-interlock prevent opening the centrifuge lid until the rotor has stopped spinning and automatic lid-lock release when operation has stopped to save processing time. Overspeed detector in running. Automatic internal self-testing after turned on. Conforms to international safety standards and regulations marked with CE, cTUVus and FCC
  • High Lab Quality Material – Maintenance-free brushless DC motor enables strong stirring power for quick rotating, long life and safety. High quality ABS engineering plastic casing and rotor ensure that the tubes rotate smoothly and safely and is not easily damaged. Cast iron base and specially designed vacuum suction feet for stable operation that reduces the chance of moving during operation
  • Widely Applications – LCD Digital control and display the time (30sec-99min) and speed (300-5000rpm, up to 2600xg). ONiLAB DM0506 low-speed centrifuge, supplied with built in fixed angle rotor A6-15P with adaptors which can hold up to 15mL/10mL/7mL/1.5-5mL×6 tubes. It is widely used for separation routine practice
  • One Year Warranty from ONiLAB: We are manufacturer that has more than 20 years experience in the field of lab products, for this machine we provide 1 year warranty, Any questions, please contact us directly and we will provide best service to each customer

Spectrophotometry Tests

Spectrophotometers are incredibly useful devices that can provide a wealth of information about milk quality. It uses color technology to determine and indicate various aspects of our milk.

One significant advantage of spectrophotometry is that the test does not need you to remove and contaminate a sample to get results. Modern spectrophotometers are portable devices that can give you instant results without having to touch the milk sample at all.

UV-5100B UV/VIS Spectrophotometer Ultraviolet Visible Spectrophotometer 190-1000nm Wavelength Range 2nm Bandwidth
  • Users can set wavelength automatically through arrow keys to avoid operation errors.
  • UV-5100B users a rigid die-cast aluminum base as its optical mount to ensure instrument stability and reliability.
  • UV-5100B is equipped with USB port to connected with a PC to display spectrum scanning, kinetics and multi wavelength testing results on the screen. The software is optional.
  • UV-5100B can set up various standard curves according to customer's solutions and find the concentration of unknown solutions.
  • UV-5100B can display wavelength, absorption and transmittance with 5 results per screen. It also has a memory store of up to 200 results.

How Spectrophotometer Works on Milk?

Spectrophotometry is based on light and color. The process works as follows:

  1. The milk sample is placed in a glass container in the machine.
  2. The spectrophotometer shines a normal light through a diffraction grate. This grate acts like a prism separating the light into its different component wavelengths (colors).
  3. The grating rotates to ensure that only one wavelength of light at a time can exit it and reach the milk.
  4. A detector, located on the other side of the sample, reads the light that passes through the sample and compares two things:
    a) Transmittance, or the amount of light that passes through the sample.
    b) Absorbance, or the amount of light that the milk sample absorbs.
  5. A digital display shows the information that the machine gathered.

Based on the sensor's information, the spectrophotometer can offer insights into many aspects of the milk, including its protein, fat, sugar (lactose), and moisture contents, as well as its chemical composition.

One significant advantage of having a spectrophotometer in your dairy is that you can test the milk at various stages of the production cycle. This allows you to quickly identify potential problems before you spend too much time and money on milk that won't meet the required standards.

You could say that a spectrophotometer measures the density of milk to determine the number of solids like protein and fat it contains. Despite how inaccurate that sounds, the US Department of Agriculture approves spectrophotometry as a reliable food and dairy analysis method.

With this in mind, and considering the potential time and money savings you could gain from not processing sub-standard milk, no dairy farm should be without a spectrophotometer.

Testing Milk For Tetracycline

Another factor that dairy farmers should test their milk for is the presence of tetracyclines and other antibiotics. Tetracycline is a common antibiotic used to treat various infections and diseases in cows, including liver abscesses, respiratory diseases, shipping fever, and foot rot.

Dairy farmers often mix antibiotics like tetracycline with animal feed to help treat and prevent these and other diseases.

It becomes a problem when traces of tetracycline and other antibiotics find their way into the cows' milk. Drinking milk that's contaminated with tetracycline can cause a range of health issues for humans. Some examples are:

  • Allergic reactions. Some people are allergic to certain antibiotics, including tetracycline.
  • Developing bacterial resistance, which means that the bacteria in your body may develop a resistance to antibiotics, so when a doctor prescribes antibiotics, it has little or no effect.
  • Teratogenicity, or the possibility that the tetracycline could cause defects in a fetus during the first trimester of pregnancy.
  • Children under 12 years old can develop permanent teeth discoloration if they drink milk contaminated with traces of tetracycline.

The US Food and Drug Administration and World Health Organization determined that the safe level of tetracycline residue in milk is 100ng/g. As long as your milk is below this level, it is safe for consumption and sale.

Tetracycline Tests

Rapid tetracycline tests are readily available from most veterinarians and farming stores. They are most commonly dropper tests, where you place a drop from the milk sample in an orifice. Within ten minutes, you will get a reading indicating whether the milk's tetracycline levels are within safe levels.

These tests can also detect tetracycline variants like chlortetracycline and oxytetracycline. Some combination tests also offer results for other antibiotics and chemicals.

Rapid Mastitis Tests

Bovine mastitis is a common problem that dairy farmers face. It can be caused by bacterial infections or trauma to the cow's udder, creating an inflammatory response in the mammary glands.

Though mastitis doesn't have many adverse effects on humans, the bacterial infection that causes it can. Apart from that, mastitis poses a significant problem for dairy farmers since it leads to reduced milk production, a cow that might not be able to produce milk again in the future, and the possibility of the disease spreading to other cows, causing massive losses for the business.

Testing For Mastitis

We already mentioned that some of the other tests we already covered could indicate the presence of mastitis. Examples are the pH test, where a high pH could point to mastitis, and the somatic cell test, which shows possible diseases, including mastitis.

But there is a rapid mastitis test option available that could more clearly indicate the presence of the disease. These mastitis indicator cards are meant to be used directly after milking. You can test each quarter of the udder separately to clearly see where the infection is.

The aspect that sets these tests apart from others is that they are an effective early detection method. If you do these tests regularly, you can notice the signs of mastitis early enough to treat the disease before it spreads or reduces your dairy farm's productivity.

Important Note Regarding All Milk Testing Tools

Whatever milk testing tool or equipment you use, remember that multiple variables could cause false positives or negatives. For example, the prewash you use to clean a cow's udders could cause a false positive on the rapid mastitis tests if you don't dry it off before testing. Some testing equipment must be calibrated before they will give accurate results.

With all tests, it's important to read (and follow) the instructions carefully, run a test multiple times with different samples, and get professional input if you're unsure. It's always best to be 100% safe when working with milk. After all, lives are literally at stake.


There are many tests that dairy farmers must do to test the quality of their milk. New testing tools are coming out every year, and the size of your farm will determine which of these will be practical for you. As long as you regularly do the basic tests like bacterial counts, somatic cell counts, and pH tests, you should be able to keep a firm hand on the production on your dairy farm.

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