Long before packets of freeze-dried cultures for milk existed, there were dairy ferments. Cheese, yogurt, and kefir are probably second only to beer in the pantheon of fermented foods. However, in the modern world, 100 percent wild fermentation in dairy products is rare. There are many cheeses made from raw milk, though, and the fermentation of these is a joint effort between wild microbes and cultivated bacteria. Cheesemakers who use this approach rely heavily on wild microbes to produce a superior, nuanced cheese, but hedge their bets for optimal acidification and flavor by adding a pinch of commercial cultures. For those who want to play on the wild side, a deeper understanding of the concerns and the process is necessary.
I like to think of the teat surface as a garden from which wonderful microbes can be collected. This collection can’t happen without paradigm shifts away from the extensive udder sanitation that’s practiced on most modern dairies. But wait, didn’t I just warn you about all of the spores floating around? How can reducing sanitation help?
We’ve used lacto-fermentation regularly at Pholia Farm when making our commercial cheeses. I find it amazingly informative to the daily practices of the farm, as well as to my cheese-making. I also employ it during the classes I teach. It’s a method well worth using when making cheeses at home. The practice will help you more deeply understand and troubleshoot fermentation and issues with a mother culture. Making raw milk cheese gives you a chance to observe environmental microbes and natural milk systems at work in cheese-making, and the complex relationship these microbes share with those that exist in a raw milk source.
Probiotics. The new darling of health and advertising. Do cheeses really contain any of these amazing, essential microbes?
While I have no letters after my name (unless I capriciously add them), it doesn’t require a university degree to understand that bacteria, both beneficial and hurtful, can only live under certain contidions. I am a cheesemaker and I study science as it relates to dairy. I know what cultures I add to milk to make cheese. Very few of these are currently considered probiotic. And even if they were, when cheese is aged, the bacteria gradually die off as they run out of food to metabolize. So even when probiotic cultures are used, they do not survive longterm aging*. In fact, I was at a conference in England this last summer where research into genetically modifying probiotic bacteria to survive cheesemaking and aging was discussed. (Without much enthusiasm on the part of the artisan cheesemakers present, I might add!)
* I did find that some aged cheeses are commercially being designed to include probiotic bacteria that survive long term aging. These cheeses are labeled as containing probiotics and are not available widely as of yet. I think you can expect to see more products such as this in the future- if nothing else, they will be introduced for the market value they will bring.
I was doing some research today for my latest book (on raw milk production and consumption). I was reading a on probiotics that I chose for it’s high ranking and great reviews on Amazon. After perusing the front chapters, I skipped to the section containing information about cheese and dairy products – and immediately had to begin putting yellow highlighter frowny faces in the margins (my system for reviewing books). At first I wondered if perhaps my information was wrong, but then found another contradiction that basically confirmed that the author was not really aware of at least this portion of his subject. (I sure hate it when what you think is going to be a reputable source, turns out to be suspect.)
So lets go over a few basic things that you can always apply to probiotics -to help determine for yourself if a food is a good source of these helpful bacteria.
In order to be probiotic, the bacteria must survive the harsh environment of our stomach and travel on to the next portions of our digestive system. Not very many bacteria have this capability – the stomach is one of the first defenses against bacterial contamination of food!
Probiotic bacteria in food must have a source of nourishment – or they will die (unless, of course, they are held in stasis through something such as freezing). This is true of all bacteria. Once a food is fully fermented, the bacteria begin to perish unless fermentation is suspended – through refrigeration or some other means. Even then, their life span is limited.
High heat, such as scalding or boiling, kills all but bacteria that are capable of forming spores that protect them from the heat. So even if milk or cheese or whey contains probiotic bacteria if it is cooked they will die.
The bacteria currently considered probiotic include only a couple of strains regularly used in making cheese. A fresh cheese that uses these bacteria as a part of its fermentation process will likely have some of these helpful microbes still living, but the longer a cheese is aged, the fewer bacteria remain alive. Aged hard cheeses are not sterile, but the life forms found on and around them are typically environmental, not those that were added during the cheesemaking process. In cheeses made using high heat and added acid, such as whey and milk ricotta, any probiotic bacteria in the whey will be killed during the high heat treatment (along with enzymes and milk’s natural defensive systems).
Bottom line, don’t look to aged cheeses as a probiotic source, yogurt is a no-brainer if probiotics are your goal! Instead, enjoy aged, natural cheeses for what they are meant to be – deliciously preserved (usually through fermentation) milk.
P.S.: So where can you find information on probiotics that you can trust? Hard to say! Popular topics are a magnet for publishers and writers. The best advice is to consult more than one source, preferably those that list scientific studies as their sources – but of course all the studies that will be helpful have not been done, nor is science a static subject.
Oh, here are a couple of sources I used to write this post:
Vet. Med. – Czech, 47, 2002 (6): 169–180 Review Article 169 – Lactic Acid Bacteria, Probiotics and the Immune System
R. HERICH, M. LEVKUT
Department of Pathology, University of Veterinary Medicine, Košice, Slovak Republic
J Dairy Sci. 1987 Jan;70(1):1-12.
Survival of lactic acid bacteria in the human stomach and adhesion to intestinal cells.
Conway PL, Gorbach SL, Goldin BR.
I was recently visiting England to attend “The Science of Artisan Cheesemaking” conference and had the great additional luck to visit an amazing farmstead creamery- Hill Dairy in Somerset. Not only was the facility quite possibly one of the most well thought out and constructed small creameries that I have ever visited, but owners Will and Caroline Atkinson, were as charming and lovely as their picturesque English farm. Since I got back to the US, we have been corresponding about a problem that Hill Dairy was experiencing both during my visit and on and off for a good part of this fall. A problem, unfortunately, that caused the loss of many batches of cheese milk and is a problem that plagues many farmstead cheesemakers (sometimes even without their knowing). High coliform counts.
First a bit about the large bacterial family called coliforms. These microbes live in the environment of the farm, especially bedding, feed, and soil. But some of them also live in the lower intestine (not only of cows and goats, but of people too) the most well-known being Escherichia coli, better known by its abbreviated name “E. coli”. The presence of E. coli in milk or cheese can be translated as the presence of feces, that’s right, poo. While E. coli and poo in milk are not desirable in any circles, it doesn’t necessarily mean that the milk is unsafe. It is the ne’re-do-well coliform cousin E. coli 0157:H7 that can wreak horrible damage when ingested. (There is another variant that surfaced recently in Germany that is just as nasty and there will no doubt be more variations in the future that will cause horrific food borne illnesses, sickness, and death). So while coliforms do not necessarily mean the presence of pathogens (illness causing microbes) their numbers are a good gauge of milk cleanliness. The higher the general coliform count, the higher your odds that some might be bad.
Currently most data say that high quality raw milk should have fewer than 10 cfu’s (that’s colony forming units) per milliliter of milk. Some states allow for higher counts and the “fewer than 10”number is somewhat arbitrary, but let’s pretend for now that it’s a great standard. Here at our farm our petri-film plate counts (done on every cheese batch – see my previous posts if you want to know how to do these) show our total coliforms at usually 3-5 cfu’s per ml. Awesome, right? Well, when I got back from England our counts shot up to over 400cfu/ml. Fortunately for both us and Hill Dairy, tests showed that none of the coliforms were from fecal sources, no E. coliforms. (You can buy petri film plates that will grow E. coli’s in a different color than regular coliforms). Interestingly, but not surprisingly, our APC (which counts total bacteria numbers) didn’t look that bad – until you looked closely and could see that there were tiny air bubbles all over the plate (from the gas produced by the coliforms) and these bubbles had lifted the film from the plate – making it look as though there were not that many colonies growing.
So what do high numbers of “harmless” coliforms do to milk and cheese? Well, these guys eat lactose – that’s milk sugar, (as do starter cultures) and produce both lactic acid and carbon dioxide – that’s gas. The problem with them is that they grow very fast and can often out-compete the added starter culture during a slow fermentation, just like what is done to make most fresh cheeses and lactic set bloomy rinds (like the Atkinson’s were making – and yes it is legal to make them with raw milk in the UK). At Pholia Farm, we make long-aged, low moisture cheese that use a faster acid development and rennet, so we would not have known about our high coliform counts if we were not doing routine lab tests on every batch. While these coliform types are unlikely to make our cheese unsafe, it tells us that something is far from ideal with our process – something that could lead to unsafe food. We don’t only make cheese, we drink our raw milk – we care that it is of the best quality possible for many reasons.
Okay, so both our farm and Hill Dairy had much higher than normal counts, what did it mean and what did we do about it to resolve the problem? The most common causes of high coliforms are dirty teats, poor milking technique, and dirty equipment. While this may seem like an easy fix, when your counts suddenly go from great to horrendous, it can be very confusing. So let’s go over a step by step procedure for trouble shooting coliform counts – with as little financial investment as possible!
Observe that animals are coming into the parlor relatively free of manure and debris – dairy clipping udders can help.
Verify that established teat and udder cleaning methods are being performed properly and that udder cleaning solutions and sanitizers are effective.
Verify that milking equipment with parts that need replacing, especially rubber parts, are up to date for recommended replacement times.
Verify that cleaning steps for equipment are effective – this includes chemical strength and effectiveness for your water type, temperatures, time, air slug velocity, etc. Swabs can be taken at various points in system and cultured for total bacteria counts to verify effectiveness.
Perform “hyper-cleaning” following guidelines from chemical manufacturer or other dairy representative. This often includes a double strength, double time cleaning and manual cleaning to verify the removal of bio-films and residue that might have occurred from less than ideal parlor practices.
Verify milk chilling process, if used (even with proper chilling, high enough coliform counts will be a problem in lactic technology cheeses)
Don’t be surprised if trouble shooting takes place over many days before you completely conquer the problem. All it takes is one step to be missed, and the problem reasserts itself. For example, our problem seems to have come from our neglect (later in the season) of dairy clipping our ladies udders, combined with wet weather, combined with me forgetting to replace a couple of rubber parts inside of the milking claws , combined with a bit too casual milking and udder cleaning techniques. I would fix one problem, but not all problems at one time. Everything needed to be zeroed out, you might say, before our counts went completely back to our normal low. It took several weeks of implementing new techniques and replacing parts and hyper-cleaning to shape things back up. During that time the count dropped from the 400, to 100 plus, then to the high 30’s, and finally to under 10.
If you experience a similar extended issue, here are some things you can do so that you don’t lose product, and future income, while you whip things back into shape:
Pasteurize the milk.
Thermize, aka heat shock, the milk (lower temperature than pasteurization, not recognized in the US, so cheeses made from thermized milk are not considered pasteurized)
Switch from lactic cheeses (such as surface ripened and fresh soft) to an aged, quickly cultured and rennet style cheese. (Verify that no E. coli is present)
Switch from freeze-dried direct set culture to bulk starter or mother culture that will provide a faster growing starter bacteria population. (if coliform counts are too high, though, this may not be enough)
Remember that if you are not testing each batch of cheese milk and are making a rennet coagulated, quickly acidified cheese, you may never know that your milk is less clean than it could be! If you do experience a problem, don’t feel alone and remember that keeping sanitation standards high on the small farm, or any farm for that matter, is an ongoing, major challenge. It is a great reminder of how quickly things can change – for the worst.
Awhile back the FDA raised the maximum number of somatic cells that Grade A goat milk can contain from the former limit of 1,000,000 to 1,500,000. Our state (Oregon) followed suit just this year and adopted the new limit for goat milk and also lowered the cow level from the FDA level of 750,000 to 500,000. While I applaud the cow levels, I am concerned about the goat levels.
Just what are somatic cells and why do they matter?
I have read and heard somatic cells in milk referred to as “pus”. This is not correct! Somatic cells (SC), by simple definition, are “body” cells. In milk, these can be normal skin cells (epithelial) shed by the milk ducts (more on that in a bit), portions of the cells (cytoplasmic particles), or white blood cells (leukocytes) that are present in order to fight off an udder infection (white blood cells are also present in “pus”). So let’s talk about why a healthy udder matters and the difference between the epithelial and white blood cells.
First, udder health correlates with the animal’s health and wellbeing. If you believe in the humane treatment of animals, then this should be important! Second, milk produced by a less than vibrantly functioning udder will not be of superior quality – either for drinking or making cheese. A healthy udder is created and maintained by a nutritionally, physically, and emotionally balanced animal. (Yes, they do have emotional needs!). While I won’t be covering all of these needs here, it is important that you remember that they are the foundation for the production of superior milk).
White blood cells migrate into the udder in order to fight off microorganisms that could cause, or are causing, an udder infection – the same job they do throughout our own bodies. When they are called to the battle front within the udder their presence is indicative of a problem. The problem could be unseen, meaning you can’t see any difference in the milk or the udder – no swelling, heat, clumps in the milk, etc. This is called “sub-clinical” mastitis and is the most common form of mastitis (udder infection). When a severe udder infection is present, it is called “acute”. Animals can suffer greatly from an acute case of mastitis – including loss of the affected part of the udder to gangrene or even death.
How Cow’s and Goat’s Differ
Now, let’s go over one of the unseen differences between goat and cow milk. Understanding starts with remembering that the udder is a gland. The mammary gland, to be exact. All glands (we have lots of them – from our armpits to our stomach) secrete their products in one of three ways. Two of these are pertinent to milk secretion – apocrine and merocrine. I am not telling you this to add more words to your Scrabble game, but instead to explain some very important differences between cow and goat milk. Glands that secrete via the apocrine system also shed parts of the cell wall lining. Goats and humans secrete milk via the apocrine approach, while cows milk is shed via the merocrine system which keeps the secretory cell intact. Kind of cool, kind of gross, don’t you think? From this you can rightly conclude that goat milk will have a “naturally” higher somatic cell count (SCC) than cow milk (when cells are counted using the same method traditionally used on cow milk).
What is a Normal, Healthy Somatic Cell Level in Goat Milk?
So if goats naturally have a higher SCC, why am I concerned about the legal limit being raised? In my experience, which is not all encompassing of course, a SCC over 300,000 in our goats, means there is a very low-grade problem. How do I know this? Every month a person comes to our farm and collects a milk sample from each individual milking doe. This sample is then tested at a certified laboratory for many things, including SCC. If the count comes back over 300,00 then we march out to the parlor (as we already do twice daily) and do a California Mastitis Test (CMT) on that doe. The CMT will show the difference in SCC between each half of the udder (or each quarter if you are testing a cow). If they are different, then It is not normal, one side has a problem. By following this policy we have (knock-on-wood) never had an acute case of mastitis and or current herd average (from tests covering about 10 years) SCC is 104,000.
Note: SCC are usually read MINUS three zeros. So 162,000 will appear on test results as 162. Anything below 1,000 is usually not counted and will appear as zero.
I have always wondered if perhaps Nigerian Dwarf goats, our breed, have a lower average than the big girls. We have two full sized goats, LaMancha’s. Their average SCC are 109-125,000 (higher than our total herd average). The current average of all dairy goats in the states covered by our testing association is 625,000. When looking at the 2011 summary, where the data is analyzed from several standpoints, Nigerian herds average 121,000 while standard goats average 783,000. If looked at by milk production volume, does producing about 3,000 pounds of milk or more are the highest at 939,000. Herd size (meaning if you have only a couple of goats versus 31 or more) seems to matter as well, but not as much as milk production volume. So many factors may come into play, but I still have to wonder if this higher limit won’t have the unhelpful effect of causing some producers to ignore even more subclinical mastitis cases instead of jumping on top of the situation before it gets out of hand. Having known commercial producers who have gone from high counts to low by improving techniques and removing animals with chronic subclinical cases does make me feel that the higher limit is a mistake.
What can You Do to Monitor Your Animals and Treat High SCC’s ?
If you have goats or cows and are not on a program where their milk is regularly tested, I highly advise performing a CMT (or other SCC’ing test) EVERY MONTH. By doing this you will find little problems and be able to address them before antibiotics are needed)
So what do we do when one side of the udder has an obvious (decide through CMT) problem? First you must rule out problems with milking equipment and general health of the animal. Of course, when it is just on one side, then you have to assume an udder infection of some sort. Before you resort to antibiotic usage, you can try some organic and old fashioned remedies. I used to do peppermint oil rubs to the udder and give the doe an oral dose (about 60 ml) of her own milk – to hopefully stimulate an antibody response. I
have recently added a common certified organic producer’s technique of orally dosing the animal with garlic “tea”. What a miracle it has been! We soaked peeled garlic cloves in water (be sure to keep refrigerated as botulism is a risk if not) then dosed the doe with 40-60ml 3x a day and her SCC went from 722,000 and 652,000 on the next test (the CMT showed a problem on one side) to, are you ready? One thousand. Yup. Garlic. Thank you!
Some animals have chronic infections that even garlic cannot clear up. A milk sample should be sent to a certified lab for culture and if appropriate antibiotic therapy can be used. There are some dairy animals now, though, carrying the antibiotic resistant form of Staph aureus (Methicillin-resistant Staphylococcus aureus) these animals should, unfortunately, be culled – removed permanently (not simply passed to another herd!)
So no matter how you feel about the new SCC limit, I hope you will take your animal’s welfare and the quality of your milk so seriously that you will set your own standards. Try to not accept less than the best – no matter what the regulations say!
Environmental testing of food contact surfaces and other surfaces that workers might easily touch and then cross contaminate a product can help you quickly find gaps in your food safety program. If you read an earlier post I did on the subject, then you may remember that here at our tiny farmstead creamery, we do an APC on the milk used for each batch of cheese. This spring we made some changes in our general procedures that lead to increased bacteria counts in our milk. By using swab testing, we were able to pinpoint where the problem was originating- before the bacteria levels became too high.
We had made several changes on the dairy farm side of processing. First, we greatly shortened the time in which the milk goes from the body temperature of the animal to refrigeration temperatures. Second, we changed some of the cleaning products to more environmentally friendly variations. When I say “environmentally friendly” in this case I mean products that break down quickly into less harsh compound or elements and are therefore easier on a septic system- ours is an oversized domestic system that handles the waste water from our home, dairy, and creamery. Due to the heavy use of cleaning and sanitizing products, our septic tank was functioning at less than optimum and costing us quite a bit in maintenance.
Since rapid chilling of milk is one of the best ways to limit bacterial growth, our problem of rising bacteria counts meant that either the equipment was not being cleaned adequately, or that bacteria was being introduced- in large numbers- at another step in the process. I mentioned we are a very small farm, so it was quite easy to gather the entire team (myself, our daughter, and one intern) and go over the possibilities. After I completed a milking and what I felt was a thorough cleaning and sanitization of the equipment, I swabbed the inside of one of the sections that collects milk from the animal (called a “claw”). After plating and incubating the results showed many cfu’s, there should have been almost zero. (See the photo later)
Swab Testing: What You’ll Need
Incubator- We use the small, inexpensive version sold by Nelson Jameson (about 90.00)
Once you have gathered your supplies, you can begin taking samples. It is a good idea to test far more surfaces in the beginning of a testing program than you may need to do on follow up tests – this will help establish a baseline of awareness. Once enough tests confirm that cleaning protocols (SSOP’s – sanitization standard operating procedures) are effective, you may be able to decrease the number of surfaces tested as well as the frequency.
Steps for Successful Swab Testing
Using a sharpie or marker, write the source of the sample and date taken on the Quick Swab container.
When you are ready to swab the surface, bend the neck of the liquid filled end of the Quick Swab so that the nutrient broth contained in the bulb flows into the end that contains the swab. Squeeze the bulb so that all of the solution is drained.
Twist apart and remove the swab from the tube. Hold the tube so that the broth solution remains inside once the swab is removed.
Rub the end of the swab, holding it at a slight angle so that the sides make some contact with the surface, on the desired area to be sampled. Rub the swab three times over an area of roughly 3-4 square inches.
Return the swab to the broth and close the tube.
Shake the tube for about 10 seconds to mix the sample into the broth.
Remove the swab from the tube, squeezing it inside the neck of the tube to remove as much of the solution from the absorbent material as possible.
Peel back the film on the sample plate (APC or other) and carefully pour the solution onto the center of the plate. It tends to run out very quickly and is tricky to do properly (as you might notice from the photo of the “claw” sample later in this article).
Use the plate spreader to gently press the sample into the plate. Use the flat side for coliform plates and the recessed side for APC plates.
Allow the plate to sit for about 1 minute so that the liquid sample will gel with the plate.
Incubate as directed for the type of sample being run. (For APC it is 90F for 48 hours, for coliform plates incubate at 90F for 12 hours).
Coliform Plates- How are they Different, When and How to Use
When you open a pack of coliform count Petrifilm plates you will immediately notice two things that are different from the APC plates. First, they are red instead of white. Next, the plate is thicker and has a circular “well” that helps contain the sample of fluid, while the APC plates are flat. When you use the plastic plate spreader on a fluid sample on the APC plates, you use the side of the spreader that has a recessed area. When spreading a sample on a coliform plate, use the flat side of the spreader. Coliform plates are a little bit more expensive then the APC plates, at about 75-80 cents each. Coliform plates that differentiate between total coliforms and e. coli are even more costly at about 1.50 each. You can also purchase “rapid” count plates that will give you results in just a few hours.
So why should you choose to run a coliform sample over an APC sample? In general it is best to focus on coliforms when testing surfaces, especially those that might come in contact with raw or finished product. While other bacteria will always be present in a cheesemaking facility, coliforms are from fecal sources and should not be expected or tolerated on surfaces inside the processing area. If a total coliform count reveals no coliforms, then purchasing and using the more expensive e.coli specific plates is not strictly needed. (These policies should be determined by each facility in consultation with a food safety specialist, however. This article is based solely on our experiences here at our own farm)
A coliform plate is read differently than an APC plate. When you look at the incubated Petrifilm coliform plate, you may see multiple small, red dots, just like you do on the APC plate (although they are more difficult to see thanks to the red background color of the plate – which is intentional). Coliform cfu’s will also have a red dot, but it will be surrounded by a little ring of air – a gas pocket produced by the bacteria. Unfortunately (or fortunately depending on how you look at it) the samples I took for this article did not grow any coliforms. Perhaps I should have swabbed the milking parlor floor drain, which would no doubt have created quite a high count plate for you to see!
Lessons in Swabbing
Here at Pholia Farm, swab testing has helped us determine the frequency of cleaning door handles, light switches, and other hand contact surfaces as well as the efficiency of our cleaning protocols for the cheese vat, milk cans, and milking equipment. Thanks to this quick and easy test we were able to pinpoint the gap in our process – in this case inadequate cleaning products – and make immediate changes. In our case, we returned to our former CIP detergent and will be attempting to offset the damage to our septic system flora by regularly treating the system with beneficial bacteria treatments. Of course, the long term lesson is that there will always be something to try to improve and compromises made – whether that is in the use of chemicals that are not as “green” as we would like or in costs and time spent trouble shooting problems. Being a small cheesemaker also means being alert and adaptable, there is nothing boring about this career!
It is important to remind you that you may not provide testing or plate counts to others unless you are a certified professional working in a certified facility. When first developing a testing frequency protocol, it is advisable to include certified lab testing and consultation with a food safety professional.
Yogurt not only provides valuable probiotic bacteria to the young ruminant, but it is easy to digest and can remain at room temperature in free choice bucket feeders without fear of growing unwanted pathogens. Making yogurt for kids and calves is a simple and inexpensive process. At Pholia Farm, we feed pasteurized goat milk and goat milk yogurt blended to a feedable consistency and served in free choice bucket feeders. We make the yogurt in the same manner as one would for personal consumption, but with a little less attention to details such as stray goat hairs and incubation temperature. Here is how we do it:
Heat milk to 180F
Cool to 130F
Stir in about 1-3 TB per gallon of yogurt from the previous batch or store purchased plain yogurt or use 1/2 tsp of powdered yogurt culture (purchased from a culture supply company such as Dairy Connection)
Place pot in an ice chest to hold temperature- add 125 F water for better temperature control. Even easier, you can simply leave the pot to sit on the counter if the room is fairly warm. The resulting yogurt won’t be quite as thick, but it will work for kids.
After 12 hours the yogurt should be set.
Store in refrigerator.
Don’t forget to retain a bit to start your next batch!
There you have it, bon appetit to your young animals!
Thanks to Suzanne Willow of Willow-Witt Ranch in Ashalnd, Oregon, I found out about this awesome little booklet by Peggy Beals called “Safe Handling- Consumers’ Guide- Preserving the Quality of Fresh, Unprocessed Whole Milk”. The booklet is meant to be distributed to members of cow and goat shares, buying clubs, and on farm milk customers. It isn’t free, but the low cost of 5.00 (or less in bulk) can be readily included in the price of the herdshare, subscription, or however it is that compensation for milk is obtained.
If you are selling, bartering, or processing raw milk for consumption I urge you to order a few copies of this great publication. In fact, I wouldn’t even consider selling milk to anyone who hasn’t read it! The information contained within puts the knowledge of the beauty and fragility of unprocessed milk into the hands of the consumer-making them your partner in providing wholesome food. This knowledge and it’s application will help us all keep the right to drink raw milk.
I have always had trouble with folks who want to blindly believe that raw milk is ALWAYS superior to processed. Peggy’s booklet starts with “Three Principles of Milk Quality”- Provide a healthy life for the cows, Prevent contamination, and Preserve Taste and Nutrition. It then goes on to share how all of these principles can be achieved through choices and actions by the producer and the consumer. I’m telling you, this booklet is a gem!
The 32 page booklet (now in its 4th edition with sales in the thousands) is available online through the Farm to Consumer Legal Defense fund at: https://www.farmtoconsumer.net/EducationalProducts.asp Purchases are made directly from Peggy, but this link with form is useful. You can also email her directly and order at firstname.lastname@example.org. Prices start at 5.00 per copy and drop to 2.50 each when you order over 100. Perfect opportunity for clubs, CSA’s, and coops to save some bucks.
Whoever you are, if you believe in the right to purchase, sell, and consume unprocessed, intact milk, then you owe it to the cause to provide education to all parties concerned. This booklet will be your ally in that mission.
Just a quick update on our little Nelson Jameson incubator and the aerobic plate count petrifilm plates: It dawned on me that that is a great way to test our cheese brine for its microbiological safety. Ran the first test on Friday and the brine, which is about 6 months old now, had zero growth. Very reassuring.
Also, I had told you all that you would have to purchase a plate spreader, but low and behold, a new one comes with every packet of petri film.
My lab geek mentor, Shawn Fels from The Rogue Creamery, is coming out in a few weeks to do some cool air quality checks – for molds and yeasts- in our creamery. I’ll update everyone on those. He’ll be using some fancy equipment, but also petrifilm plates specifically for counting fungi.
Who would have thought having your own on-farm lab would be so easy- and affordable? I am kicking myself for not trying this sooner. Doing our own, in house, milk quality tests will help our small, licensed dairy to stay on top of cleaning regimens and milk quality. Even though our results will not be official (you have to be a certified lab to have official results) they will still assist us and even help inspectors know that our food safety program is more complete. So just what is a “plate count and how do you do it yourself?
Plate counts were traditionally preformed by taking a small sample of a substance and pouring or swabbing it onto a glass petri dish that held had a gelled growth medium. The plate was then kept warm for a certain number of hours after which a lab technician would literally count the number of “dots” on the plate. The dots were each a cluster of bacteria called a “colony forming unit” (cfu for short). The most common plate test is the “standard or aerobic plate count” (SPC or APC).
Fortunately for us, 3M makes a wonderful, simplified product called Petrifilm Plates. These plates are ready to use, needing no added growth medium. They are also inexpensive, costing about .70 cents each (for the aerobic count) and come in a box of 100. You will also need an incubator and luckily, a compact, low tech unit (costing about 70.00) is sold by the same company from which we already buy a lot of our supplies, Nelson Jameson (www.nelsonjameson.com). They also sell the 3M Petrifilm plates and other needed
supplies. In addition to the aerobic count plates, it is a good idea to also buy coliform plates (a box of 50 is 38.00). You will need a count plate spreader (a little plastic disc made especially for spreading the sample onto the Petrifilm plate) and, if you want to do swab tests on dry surfaces, 3M Quick Swabs work great. The Quick Swabs are a bit more expensive, about 1.50 each and come in a box of 50.
The SPC grows all kinds of bacteria from milk or swabs of surfaces- even the good bacteria. For example, if you took a sample of milk during cheesemaking, the plate count numbers would be through the roof, but that is what you would want. Milk fresh from the udder, however, should have very low counts, preferable less than 1,000 cfu per milliliter.
Step by Step Instructions for Plating a Milk Sample
Obtain a 1 ml sample of milk using a sterilized 1ml syringe or a pipette.
Lift the film on the room temperature Petrifilm plate and place the sample in the center.
Lower the film gently.
Center the plate spreader, smooth side up, over the sample, lower onto film and press firmly to spread the sample in an even circle.
Place the Petrifilm in the incubator at 90 F (note: the compact incubator from Nelson Jameson states that the shelf temperature is 10 degrees lower than the thermometer readout, so adjust your temperature accordingly) and incubate for 48 hours.
After 45-50 hours (48 is ideal) remove the plate from the incubator.
Using a fine tipped Sharpie pen, count each red dot, no matter how small, using the pen to mark as you count (so that you don’t double count any cfu’s).
If the plate has very few red dots, then count the entire plate. If there are quite a few, you can count one square and multiply the result by 20. Do this with several squares so that you get an accurate average. (Each square represents 1 square centimeter and the plate area is 20 square centimeters, thus the multiplication by 20)
If an undiluted sample grows too many cfu’s it is impossible to get a good count, since the plate will be over crowded with overlapping colonies. You can carefully dilute the sample with sterile water by 50% and then multiply the resulting count by two. (For example, say I diluted the ml of milk with half sterile water and then count between 200 and 250 cfu’s per square. I would then multiply that number by two for 400-500, and then multiply that by 20 for 4,000-5,000 cfu/ml.)
Another useful Petrifilm plate is called the coliform count plate. These have a growth medium that will only allow for coliforms (harmless and bad) to grow. So if you want to know how many of those cfu’s on your standard count are coliforms, this test is a great follow up. Coliforms are the most common problem bacteria in milk and in a cheese plant (and sometimes the deadliest). So low coliform counts from work surfaces and equipment, as well as in milk and brine, are a great confirmation of good processes. Coliform counts should be much lower than SPC’s, a reading of less than 10 cfu/ml is ideal.
Petrifilm plates should be stored in a cool, dry area. Be sure to tightly seal the individual film packets. They are so sensitive that they can simply be exposed (with the cover film pealed back) to the air and culture contaminants via that route. So you don’t want to expose them until ready to inoculate.
You should know that you may not run tests for anyone other than yourself. You can let people run their own using your incubator, but you may not run a test and provide a count result, that is only for certified professionals. It doesn’t mean you can’t have a “plating party” and show others how to count their own!
There are several other Petrifilm plates that I will probably try out on our farm, including staph aureus for udder health, and yeasts and molds, for cheese quality. I’ll be sure to share whatever I learn with all of you. But for now, this is enough to work on. Oh, as a way of logging our results, I plan on take a photograph of each counted plate and keeping those on file.
I finally plugged in the little petri-film incubator we purchased from Nelson Jameson and I am, at the moment, cooking our first anaerobic plate counts. It took me a long time to get around to this, but I think it will go a long way toward making sure our milk is super clean, as well as our process.
The films must incubate for 48 hours, so I don’t have any exciting things to share with you guys, other than I am pleased that I finally tried it! My friend at Rogue Creamery, Shawn Fells, showed me how to do these simple, on-site quality tests for milk and environment, but I was still intimidated, I have to admit! Turns out it is as easy as squirting 1ml of milk on a plate and sticking it in to cook (much simpler than making dinner, right?).
I’ll write a full description of how to do it (maybe a YouTube video for you all too?) once I figure it out and have a better idea on how to implement it as a part of our quality assurance program.
Oh, the little incubator was under 100.00 and the plates are about 7.00 each. Still cheaper than shipping samples out for testing (or having your inspector let you know your milk is not as clean as hoped).
So pictures and updates to come, unless I botched the entire process….