Author Topic: Some Data on Raw Milk in Cheese  (Read 289 times)

Offline garbetsp

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Some Data on Raw Milk in Cheese
« on: January 01, 2018, 10:28:37 AM »
I've been researching what I would consider safe guidelines for raw milk usage in cheese making. It's hard to find any solid advice, or even what the actual risks are. Simple googling one easily gets two extreme positions. The FDA in the US thinks that raw milk is a hazardous material and should be handled like a biohazard and *never* be used un-pasteurized. On the other extreme raw milk advocates claim that it will improve everything in ones life.[1] When encountering such polar opposites there's usually a lot of middle ground where the truth is nuanced. Murphy has said there is a simple answer to every problem and it's wrong. I will explore this middle ground and invite discussion and corrections as I'm an aspiring cheese maker sharing my frugal notes.

A bit about myself as introduction. I grew up in dairy country in rural Arkansas and we bought raw milk products from neighbors my entire childhood. Further I was named after my uncle "Cheese", who loved nothing more than cheese. I seemed to have inherited the cheese head gene. I'm very analytical and seek evidence for claims, but also a bit morbid about personal health risks ("Oh my there's a mole I must be dying of cancer"). Given this, I sought out actual statistics and found a paper by Gould at the CDC.[2] This paper compares reported disease outbreaks in the United States over fourteen years between pasteurized and unpasteurized cheese sources.

The first thing that struck me is that the overall numbers were far less than death by snail[3]. That's right, you have far more to fear snorkling for shells than from raw milk. Absent from the report were consumption rates or in statistics what one would call exposure. So raw counts are not as informative, but it's a safe bet that pasteurized consumption is far greater than raw milk. So the counts between the two being close, one can infer the greater risk that raw milk consumption has over pasteurized. If someone has a source for total consumption of milk products in the USA with pasteurization status estimates, I could produce a chart of relative risks and place the risk on a better scale.

The next striking thing about the paper is that the majority of the cases for raw milk (20 or 56%) were from illegally imported Queso fresco and other Mexican cheeses. The plurality for pasteurized were from pre-prepared cheese trays and dip sauces (14 or 39%). Mexican cheese ranked up there with 5 cases (14%) for pasteurized as well. Homemade cheese from raw-milk had 7 cases (19%). The remainder for raw milk is mostly soft cheeses. Oddly, ricotta and mozzarella for raw each had a reported case. Another interesting fact is that hard cheese cases were 2 for raw milk (6%) and 6 for pasteurized (16%). Note that these numbers are quite low for a 14 year period.

What I draw from this is avoid Mexican cheese, especially from shady dealers; better to make it oneself. Most of these are raw milk acid coagulated, then transported and stored in questionable conditions.

Secondly the ricotta and mozarella I make ends up pasteurized by the method (195F), there are "quick" acid coagulated recipes out there I don't use and I suspect these are what is referred to in the case listings. I would personally avoid any recipes with raw milk that don't involve culturing. One is creating a perfect environment for any bad culture to propagate by not adding culture. Similar (but not as egregious) as the Mexican cheese cases.

Third, just avoid all those precut cheese trays and tubs of pre-made cheese dips. Make ones own using your fromager knowledge--no compromises.

Lastly, soft aged cheeses and hard numbers are comparable on the cases stats and it's hard to say much from this data. Personally, I'm going to soft temp pasteurize my raw milk for making soft cheese till I perfect my technique. Semihard cheeses, I'm just going to use raw and age them sufficiently.

Overall, I find the FDA's position on raw milk to be overstated. Pasteurization is important when you have long distribution chains of product sitting on shelves, many hands in the chain, and long periods of time. When making cheese and going straight from farm to culturing, a lot of the risk is mitigated. The FDA is trying to use simple enforceable rules for a large network of milk distribution, whereas the context of artisan cheese production is very different.

[1] Portlandia S05E03, "Healthcare"
[2] L. Hannah Gould, Elisabeth Mungai, and Casey Barton Behravesh. "Outbreaks Attributed to Cheese: Differences Between Outbreaks Caused by Unpasteurized and Pasteurized Dairy Products, United States, 1998–2011". Foodborne Pathog Dis. 2014 July ; 11(7): 545–551. doi:10.1089/fpd.2013.1650.
[3] E. Shockman. "Why snails are one of the world's deadliest creatures." August 13, 2016, PRI Health and Medicine. https://www.pri.org/stories/2016-08-13/why-snails-are-one-worlds-deadliest-creatures

Offline Frodage4

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Re: Some Data on Raw Milk in Cheese
« Reply #1 on: January 01, 2018, 02:51:46 PM »
Hi Garbetsp,
That is one really nice analysis. And your bibliography is impressive! Very few people can quote Portlandia and the CDC's original research in one go. No more snail flavored cheese for me! A cheese for you!

Offline mikey687

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Re: Some Data on Raw Milk in Cheese
« Reply #2 on: January 02, 2018, 03:50:35 AM »
I managed to track down a copy of this book a few weeks ago. I use exclusively raw milk unpastuerised in cheese making so I do a lot of reading up on all the information I can find.

This is a set of scientific papers that have been translated from french into english by the Specialist Cheese Makers Association in the UK. All about how raw milk microbes affect cheese quality and the role of those microbes in unpasteurised cheese making (specifically the risks and benefits they bring).

I'm only half way through, but the detail is very high, and I can really recommend it.

It's out of print now, and I was told I was getting the last copy, but maybe there are some hiding somewhere, or if enough interest is generated they can print some more.
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Offline garbetsp

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Re: Some Data on Raw Milk in Cheese
« Reply #3 on: January 03, 2018, 03:35:09 PM »
Very few people can quote Portlandia and the CDC's original research in one go.

The best part of the Portlandia reference is that when googling which episode it was, I found several websites citing it as evidence of the power of raw milk.  :o


Offline curiouser_alice

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Re: Some Data on Raw Milk in Cheese
« Reply #4 on: January 05, 2018, 08:28:17 AM »
Excellent analysis and thank you very much.  I do not have access to raw milk, being in Virginia, but from everything I have read using it for cheese making poses very little risk.

Offline garbetsp

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Offline Al Lewis

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Re: Some Data on Raw Milk in Cheese
« Reply #6 on: January 05, 2018, 09:50:57 AM »
Simple rule, if using raw milk make cheeses that will be aged at least 60 days.
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Offline GortKlaatu

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Re: Some Data on Raw Milk in Cheese
« Reply #7 on: January 05, 2018, 06:10:57 PM »
Al, that's only to stay in keeping with the US FDA regulations.  ;)   
You know that Europe, South America and Central America does not adhere to that rule for raw milk cheeses--as supported by information like that above.

« Last Edit: January 05, 2018, 06:18:29 PM by GortKlaatu »
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Offline garbetsp

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Re: Some Data on Raw Milk in Cheese
« Reply #8 on: January 08, 2018, 10:59:04 AM »
I found an updated article from the CDC: https://wwwnc.cdc.gov/eid/article/23/6/15-1603_article, or
https://wwwnc.cdc.gov/eid/article/23/6/pdfs/15-1603.pdf

This article paints a starkly different picture. It estimates that the risk is 840 fold greater with raw-milk products across the board. Note that this paper does not differentiate cheese from liquid milk in the data as best I can tell looking over it. I.e., it doesn't estimate risk for cheese versus drinking raw-milk and lumps the two together. It references the previous report that I started the thread with. As a statistician I find this analysis flawed for estimating risk from cheese. I.e. From this I know that raw-milk is risky but have no information on whether cheese from raw-milk is risky. Nor the sub-groups of cheese--acid coagulated vs. cultured, nor the factors of age. Given the previous data, it's quite likely that by lumping this together the risk for cheese from raw milk is massively overestimated.

A recent meeting of the FDA since there was a single case of poisoning that exceeded the 60-day rule they were recommending making it longer. No rule change occurred as artisan cheese producers are lobbying for a removal of this rule. However, if they mitigated risk consistently then raw oysters would be banned.

Offline GortKlaatu

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Re: Some Data on Raw Milk in Cheese
« Reply #9 on: January 08, 2018, 07:39:26 PM »
Almost all information about Listeria infections in dairy is about the milk itself....not much is studied about what happens if it is used for cheesemaking.
Interestingly, there was a study done  in Risk Analysis from June 2016 that says: "However, regardless of the milk status (pasteurized vs. raw), a properly executed cheese-making process (i.e., an appropriate and sudden pH drop) should lead to a similar low risk due to the lack of growth of any contaminating L. monocytogenes. "
[/color]Also, it should be noted that the CDC reports laboratory confirmed Listeria infection at about 1:400,000--and that is from ALL sources (deli meats and hotdogs have often been the most common source, along with smoked seafood, celery and cantaloupe and milk--pasteurized and raw.)
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[/color]And other studies have shown that in European countries that produce and sell raw milk  soft cheeses of less than 60 days that there is still a 3-4 times greater incidence in the US which has been surmised to mean that the source of Listeria is something other than from the milk.
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[/color]So as usual, it boils down to your choice as there is reasonable evidence on both sides of argument with the US taking a much more conservative, hard-line approach.
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Somewhere, some long time ago, milk decided to reach toward immortality… and to call itself cheese.

Offline garbetsp

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Re: Some Data on Raw Milk in Cheese
« Reply #10 on: February 12, 2018, 10:45:14 AM »
Choice quote I just read from "Reinventing the Wheel: Milk, Microbes, and the Fight for REAL CHEESE", pg 136, by the Percival's:

Quote
Even if only a tenth of the raw milk produced was turned into unpasteurized cheese, it would still equate to eating 1.9 pounds of cheese with the risk of death from driving 1 mile.

I think that puts the risk in a clear perspective. Another quote from the book:

Quote
Cheese is not liquid milk.