Author Topic: UV "Pastuerized Milk" for use in cheese making  (Read 1165 times)

Offline Mike Richards

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UV "Pastuerized Milk" for use in cheese making
« on: September 03, 2012, 09:22:31 PM »
I've seen a few things about "pasteurizing" milk with ultraviolet light instead of heat.  I haven't found any discussion on the implications this has for cheese making.  The two things that I think about are that 1. no heat is used, so there's no heat "damage" to the milk, and 2. all the natural flora in the milk would also likely be inactivated.  I do wonder what effect the uv has on the protien structures, though from the little I know, I don't imagine it would have a significant impact.

I've seen little uv-light sticks you can get to "purify" water (for camping and such).  I have doubts they would work in milk as well as they do in water--though I don't know much about milk's transmissivity in the uv range or what other issues would be involved.

Does anyone know more about this topic? 
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Offline FRANCOIS

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #1 on: September 03, 2012, 11:02:19 PM »
I haven't seen it used commercially for milk.  It would be very difficult with a high solids liquid like milk to pasteurise.  Even more difficult with cream.  Also regulators would have to accept it as a 6log kill technology, so you'd have to actually build it, test, document and apply for regulatory approval.  It's much easier just to use steam.

Offline linuxboy

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #2 on: September 04, 2012, 01:27:28 PM »
UV pasteurization was on the NCIMS 2011 agenda (from innovation center for US Dairy), but as of right now only water processing through UV is part of the PMO. My guess is we are 2-5 years out for field trials in the US. I have run some trials with it, and one can achieve 5-6 log reduction with it effectively. If you want to use it experimentally, get a calf milk (waste milk) UV pasteurizer, or an apple juice UV pasteurizer. It takes several cycles at moderate power to work, and you have to design the cavitation and flow rate and overall chamber just right to accommodate milk. There is room to grow for current designs. It's also possible to import UV pasteurization units from Europe if you want ready made. There are a few universities doing alternative pasteurization research out there, such as OSU.

There is no heat damage to the milk, but there is some protein damage. In trials, it has not led to flavor defects or changes. But it is not the same as raw milk. More like somewhere in the middle between raw and pasteurized.

Have done a moderate amount of research, would be easiest if you ask direct questions.
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Offline FRANCOIS

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #3 on: September 04, 2012, 05:53:57 PM »
How does it work for cream?  We are seperating the raw milk, pasteurising milk seperate from cream, and recombining to a specific P:F ratio.  I could see it on milk perhaps, but cream would be difficult.  Our cream is 40% solids.

Offline linuxboy

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #4 on: September 04, 2012, 06:05:33 PM »
I don't see it working for cream. The reason it works at all for milk is that if you create a thin enough sheet, and put a reflective surface on the other side of the emitter, and introduce cavitation, eventually, with enough passes, enough of the milk is in contact with the UV to where it's reasonable to say there's 5 log. For cream, there's tons of issues. Like what about fat agglomeration... would need to be homogenized to ensure even contact. Or might need to crank up the power, which has the potential to do weird things to fat and protein, and that might be a food safety concern. I might be wrong here, but I don't think anyone has done the work for cream specifically.

But I think for milk it will eventually be passed because it uses a ton less energy than HTST, and all the world is concerned with that.
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Offline Mike Richards

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #5 on: September 04, 2012, 09:09:02 PM »
It seemed like a more efficient, and perhaps less injurious method of pasteurizing to me.  But, like I said, I wasn't sure of the degree it impacts other molecules within the milk.  If I were in a position to do so, I think I'd enjoy doing research in the area of non-heat pasteurization of milk and its effects on cheese quality.  I should have gone into food science.  :)

At first, I didn't have any specific questions, I was just interested in the application of technology.  Now, I do have a couple questions, though.  When you say cavitation, I presume you mean the same thing I mean when I say it--the direct conversion of a liquid to a gas due to a localized drop in pressure.  I can see how that would be beneficial to irradiation by a dramatic reduction in density and, thus, an similarly dramatic increase in penetration (and thus, saturation) of the uv light.  Is this correct?

If so, doesn't that kind of handling of the milk also cause damage itself?  I've been reading about how excessive handling messes up the membrane that coats the fat particles which can increase problems with rancidity.

Also, do you know if the uv inactivates enzymes already present in raw milk like pasteurizing does?  I presume the answer to this question is, "It depends on the level of irradiation."  More specifically then, when irradiating milk at the level required to effect the 5-6 log reduction in pathogens, what kind of effect is had on enzymes?

Again, I'm not asking because I need to know, just because I'm interested.  I find this all very fascinating and really enjoy learning more.  Thanks!
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Offline linuxboy

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Re: UV "Pastuerized Milk" for use in cheese making
« Reply #6 on: September 05, 2012, 08:50:39 AM »
Sorry, wrong word. I meant agitation... turbulence. When you're pumping milk to be in contact with the emitter, you can design it so that the maximum milk volume will be in contact with the UV. To do this, the milk needs to be in motion and be agitated enough to keep moving and exposing new milk.

And no, the reactor design itself tends to be pretty benign. What may do damage is the pump impeller. It tends to increase ADV (fat breakdown), exactly as you noted.

enzymes are proteins, and the current body of research suggests that whey proteins are denatured even at normal moderate levels. There's not much about the degree or how duration affects denaturation extent. But it does happen. Which enzymes do you mean specifically?
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