What tests do you perform on incoming raw milk?
Hello All,
I am curious as to how other dairy folks test their incoming milk.
I am at a small cheese plant, we currently take samples from the incoming tanker and do the following tests in house: antibiotics (prior to unloading), petrifilm coliform, petrifilm APC. We send out milk to an external lab for the following tests: listeria spp, salmonella, staph aureus, somatic cells, IRMA (butterfat), added water.
We have the farm samples that we save in case of a positive result on antibiotics, but at this time we are not sending them out for analysis.
Do you test farm samples or tanker samples? I think we should test tanker samples because I would rather have the information of the milk as it is when we are receiving it, rather than the milk as it is at the dairy farm. When we receive mixed loads (unusual as we mostly make product from our own dairy farm), we are doing the in-house micro tests on the individual farms.
I am just curious as to what other dairy people are doing with their incoming raw milk testing, specifically what tests and do you test tanker samples or farm samples. Do you think it is necessary to test for the bad pathogens or is the coliform test adequate? (At my old job we never tested milk for listeria/salmonella/staph.) Thank you all for taking a look, I appreciate the assistance.
Cheers
It depends what you're using it for. If you're making raw milk cheeses, that sounds reasonable. If you're making pasteurised products, it does sound like overkill and would you get the results back in time anyway? I would also argue it's cheap and easy to do added water testing in house and you'd want to do that as a positive release for your tanker. Also as your antibiotic test is in house and prior to unloading, it's a rapid test. You need to be aware that rapid tests don't pick up all antibiotic contaminants...
Thanks GMO. We make mostly pasteurized, but occasionally do make raw milk cheese (like 2 vats in the past year). I am really curious as to what you think about tanker samples vs. farm samples. Do you have an added water test machine that you would suggest? The one I am familiar with is great, but way outside our budget.
Thanks GMO. We make mostly pasteurized, but occasionally do make raw milk cheese (like 2 vats in the past year). I am really curious as to what you think about tanker samples vs. farm samples. Do you have an added water test machine that you would suggest? The one I am familiar with is great, but way outside our budget.
Hi peevie,
From a Principle POV, The haccp interpretation of the above would probably be "PRP vs Verification".
The haccp answer would be that both are necessary except that, based on risk/findings, the frequency/density of the latter would probably (hopefully) be a lot less. Regardless, customer requirements may result in ba lot of both.
HACCP/FS is the Name of the Game. :smile:
Good morning. The tests that are done for incoming raw milk are called "platform tests". They are just to inform you if you can accept the milk or not. The following are basic tests to determine acceptability : dye reduction test(10 or 30 minute resazurin), SG(to determine adulteration), acidity, antibiotic presence.....
Farm tests in the UK tend to be through a farm scheme and related to payments (i.e. farmers with "cleaner" milk get higher prices for it). Intake testing tends to be at tanker level as that is timebound and related to positive release into the facility.
I have no experience in raw milk cheese making but it scares me witless if I'm honest especially blue and mould ripened cheeses like bries etc.
Since you are in the US you are required to test for antibiotics and follow the FDA protocol for antibiotic testing which is Appendix N from the Pasteurized Milk Ordinance.
Other tests beyond this are for your own quality purposes. Furthermore, the milk you buy is likely from some type of cooperative. The cooperative handles all of the dairy farm, or producer samples, and testing for component analysis, somatic cell counts, and bacteria levels. There are regulatory requirements for the somatic cell counts, but also as someone else mentioned producers with lower bacteria and somatic cell counts will be paid more or receive bonuses for the better quality milk.
I would recommend you take samples from the tanker yourself, don't rely on drivers. From that tanker sample you should monitor the bacteria quality testing coliform, SPC, and LPC (lab pasteurized count). For you, LPC is important because it gives an indicator of what microbes can potentially survive pasteurization and affect your cheese yields. Additionally, check acidity or pH, and you can do a specific gravity for water adulteration. Although, I think the water adulteration is a far less common issue than it was 10 or 15 years ago in the US. In our facility, since we started last year we have received almost 400 milk loads and not a one had an issue with water adulteration. We use a cryoscope, to test, but that's more to test and monitor our internal water adulteration as the milk goes through the process.
Component testing from the tanker you'll want to do as well. Note, if your SNF is abnormally low on the raw milk then that is also an indicator of water adulteration. It will affect the SNF first, before the fat.
I'm also a big believer in the organoleptic quality of the incoming raw milk. Odor, color, and taste can be great indicators of the quality of the milk. One of the things to look for is when the tanker is first opened at the dome....what is the first odor coming out? This will be a good indicator of the milk quality. Additionally, visually the color such as a slight pink hue which can indicate blood, or hairs or flies floating on top of the milk in the tanker.
All good things to look for. Hope this helps.
Water adulteration I agree doesn't happen frequently but I have known poorly managed CIP on farms which has been picked up by freezing point depression, i.e. they failed to drain the tanks properly by accident not by any malicious action but it saved having CIP contaminated milk.
Everything that Ryan M said. Always make sure the tanker is well agitated (15 min) prior to pulling your samples. Testing a sample that is mostly butterfat skews results.
Also, I would advise declaring that you discovered a positive antibiotic tanker, but rather that you have a presumptive positive. I have tested a lot of milk in my day, and only the USDA can confirm positive tankers.
Best of luck to you
Since you are in the US you are required to test for antibiotics and follow the FDA protocol for antibiotic testing which is Appendix N from the Pasteurized Milk Ordinance.
Other tests beyond this are for your own quality purposes. Furthermore, the milk you buy is likely from some type of cooperative. The cooperative handles all of the dairy farm, or producer samples, and testing for component analysis, somatic cell counts, and bacteria levels. There are regulatory requirements for the somatic cell counts, but also as someone else mentioned producers with lower bacteria and somatic cell counts will be paid more or receive bonuses for the better quality milk.
I would recommend you take samples from the tanker yourself, don't rely on drivers. From that tanker sample you should monitor the bacteria quality testing coliform, SPC, and LPC (lab pasteurized count). For you, LPC is important because it gives an indicator of what microbes can potentially survive pasteurization and affect your cheese yields. Additionally, check acidity or pH, and you can do a specific gravity for water adulteration. Although, I think the water adulteration is a far less common issue than it was 10 or 15 years ago in the US. In our facility, since we started last year we have received almost 400 milk loads and not a one had an issue with water adulteration. We use a cryoscope, to test, but that's more to test and monitor our internal water adulteration as the milk goes through the process.
Component testing from the tanker you'll want to do as well. Note, if your SNF is abnormally low on the raw milk then that is also an indicator of water adulteration. It will affect the SNF first, before the fat.
I'm also a big believer in the organoleptic quality of the incoming raw milk. Odor, color, and taste can be great indicators of the quality of the milk. One of the things to look for is when the tanker is first opened at the dome....what is the first odor coming out? This will be a good indicator of the milk quality. Additionally, visually the color such as a slight pink hue which can indicate blood, or hairs or flies floating on top of the milk in the tanker.
All good things to look for. Hope this helps.
RyanM,
Thank you so much. This is great information. I really really appreciate your assistance.
Cheers
Everything that Ryan M said. Always make sure the tanker is well agitated (15 min) prior to pulling your samples. Testing a sample that is mostly butterfat skews results.
Also, I would advise declaring that you discovered a positive antibiotic tanker, but rather that you have a presumptive positive. I have tested a lot of milk in my day, and only the USDA can confirm positive tankers.
Best of luck to you
hi ronrico,
Perhaps you meant against declaring ..... ?
I spent the last 3 years of my career working as Milk Intake Technician with a large dairy in UK so I have a bit of first hand experience with milk intake testing. We unload up to 2 million litres of milk in a 24 hours.
We had to do 4 main test on each milk tanker that comes on site.
1. Antibiotic testing (beta star)- takes 5 minutes to complete
2. Freezing point depression (fpd) test - 5 min in a cryoscope
3. Taste test- less than 2 minute using microwave oven to pasteurize milk
4. Temperature
5. Milk acidity test (this is only carried out when milk temperature is higher than 8°C but <10°C
I do have a list somewhere of which rapid tests detect which antibiotics but be certain that there isn't a single test which detects them all and even where they are detected, it may not be sensitive enough to be at the maximum legal limit. It's worth knowing as people assume as they're doing an antibiotic test it will pick up all antibiotics. If it's a rapid test, it certainly won't. I'm always concerned canny farmers may use that to their advantage.
I have worked in milk plant and norm was - antibiotic, cryoscopy, DMC, blood, taste and smell. I now work in a cheese plant and all we test for is antibiotic, T.A., coliform and yeast and we compare our raw micro testing to our pasteurized milk sample. Numbers are always <10 for both coliform and yeast.
We also do finished product testing.
I do have a list somewhere of which rapid tests detect which antibiotics but be certain that there isn't a single test which detects them all and even where they are detected, it may not be sensitive enough to be at the maximum legal limit. It's worth knowing as people assume as they're doing an antibiotic test it will pick up all antibiotics. If it's a rapid test, it certainly won't. I'm always concerned canny farmers may use that to their advantage.
It is tricky because no single test that screens all antibiotics. We do a beta-lactam, and my state inspector is happy with what we are doing on that. I did get a memo that tetracycline will start to be required, but at super wonky intervals. The guidance document might as well have been in greek, it was so hard to understand. Thankfully we have an excellent relationship with our state guys, and one of the few things I am confident about is that we are currently doing our antibiotics tests properly. We are not a confirmation lab, we only do presumptive positive. We are organic, and while I know some organic sometimes producers break the rules, we have yet to have a presumptive positive in the two years I have been here. Thank you for looking at the post and sharing.
It is tricky because no single test that screens all antibiotics. We do a beta-lactam, and my state inspector is happy with what we are doing on that. I did get a memo that tetracycline will start to be required, but at super wonky intervals. The guidance document might as well have been in greek, it was so hard to understand. Thankfully we have an excellent relationship with our state guys, and one of the few things I am confident about is that we are currently doing our antibiotics tests properly. We are not a confirmation lab, we only do presumptive positive. We are organic, and while I know some organic sometimes producers break the rules, we have yet to have a presumptive positive in the two years I have been here. Thank you for looking at the post and sharing.
As long as you are doing the correct type of test. The state and PMO require test kits to have capability of testing for 5 different beta lactams. As long as you have a PMO approved test kit you are fine. The only thing you should look into, just in case, is your reporting for any presumptive positive result. There are specific reporting methods for each state regardless if you are a screening lab (such as yourself) or if you are a confirmation lab. There is a form to send to your state. I've attached our California state guide to reporting antibiotic tanker positive samples.
As far as the tetracycline, I believe that will be the State inspectors who will be sampling and sending to state labs for testing. At least that is how I interpreted the document. You should discuss with your State inspector to verify. Our State inspector hasn't brought it up yet and he does a lot of dairy farms inspections, and only a few processing plants like us.
Attached Files
I have worked in milk plant and norm was - antibiotic, cryoscopy, DMC, blood, taste and smell. I now work in a cheese plant and all we test for is antibiotic, T.A., coliform and yeast and we compare our raw micro testing to our pasteurized milk sample. Numbers are always <10 for both coliform and yeast.
We also do finished product testing.
Curious...why test for yeast? It typically does not grow in fluid milk. I mean....it almost never grows, especially in raw milk as there isn't time for it to develop, additionally it is typically outcompeted by the TPC bacterial flora.
Also...I wonder, really you get less than 10 CFU/mL on coliform of raw milk? That doesn't sound right....I mean, it is possible, but it is highly unlikely. My experience is with larger dairies though in California and Nevada. We do have tankers that are negative for coliform, but typically they average around 50 to 100 CFU/mL which is still very good for raw milk.
When I've tested raw milk for coliforms I have to admit I've never found it but don't test it routinely. Not sure about yeast growth in milk, I'd be surprised if it doesn't but it certainly can grow in cheese and as they're making some raw milk cheeses it might be useful to know for that. Some yeasts are desirable though for flavour development.
Surprised the US antibiotic laws are so lenient that you only need to test for such a narrow range? Irrespective of this, if you can test for more, I would. For one, it may impact your starters if you have antibiotic presence and if the farmers know there are some they can "get away with", it could be a worry.
When I've tested raw milk for coliforms I have to admit I've never found it but don't test it routinely. Not sure about yeast growth in milk, I'd be surprised if it doesn't but it certainly can grow in cheese and as they're making some raw milk cheeses it might be useful to know for that. Some yeasts are desirable though for flavour development.
Surprised the US antibiotic laws are so lenient that you only need to test for such a narrow range? Irrespective of this, if you can test for more, I would. For one, it may impact your starters if you have antibiotic presence and if the farmers know there are some they can "get away with", it could be a worry.
LOL...they are not lenient at all. It is one of the most regulated parts of the milk and dairy industry in the US. Just because you don't test every antibiotic under the sun doesn't mean they are there...for one, many antibiotic families just are not available for the farmers to use. Secondly, anything that may be available is strictly controlled. Of the ones that are most available, approved to be used, and most widely used are the beta lactam family of antibiotics; hence why this is the one of target. Of course, industry changes and soon we will see more monitoring of the tetracyclines because they are becoming a larger concern. There's not really anyone "getting away" with anything on the antibiotic front in the US.
In terms of yeast in fluid milk...it just isn't there. Where would it come from? How would it out compete the normal bacteria flora? It doesn't. Sure, it is a concern with cheeses or cultured products because the lower water activity in those products promote yeast and mold growth while inhibiting general bacteria in comparison.
Hi Ryan,
Not my area but -
Aerial contamination is negligible under normal conditions. However, Bacillus, Clostridium, moulds and yeasts may use the aerial route to contaminate the milk. This may lead to low quality milk and milk products.
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In my almost 20 years experience in dairy I've never come across raw milk that was barny in flavor to the point where yeast was a potential contaminant in question. Yeast does not grow well on fresh milk and is out-competed by the other normal bacterial flora.
However, in different coutnries and regions there may be more prominent issues with yeast in fresh milk such as regions that have high humidity or temperature swings.
I've only seen yeast problems in cultured milk products, not in fresh or bottled milk.