Author Topic: Milk, Pasteurized - Souring At 4 Days  (Read 2697 times)

Tatoosh

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Milk, Pasteurized - Souring At 4 Days
« on: March 02, 2011, 04:29:48 AM »
I am curious as to why our locally produced milk sours in 3 to 4 days.  I initially thought it was because the dairy was using "thermization"* and not true "pasteurization" to treat their milk.  But when I talked to the head of the small co-op dairy, he assured me their "pasteurization" was the 72C for 15 seconds, which is much hotter than "thermization".

A bit of background.  The dairy is located just outside of Baguio City, Benguet which is roughly 5000 feet in elevation and located in the Cordillera (mountain range) on the island of Luzon in the Philippines.  It is not the heavy heat of the lowlands here, with temperatures running around 70-75 during the days and dropping around 60 at night, for most of the year.  Sure, we get a heat wave and things can get in the 80's or even 90's for a little bit, but not long.  And a friend who laughed at me for buying blankets when I visited him in Guam spent one very chilly night shivering under a sheet when he stayed at a local hotel here and the temps went way into the low fifties.  That doesn't happen often but it can.

So it's not oppressive heat that is turning the milk.  Milk in the USA will last for a week if stored in a refrigerator.  Is that due to being homogenized?  The milk here is not homogenized.  Or perhaps US milk is lower fat from the fat content being stabilized and somehow that effects shelf lfe? I'm puzzled by the short life span of the co-op's milk. 

Any dairy folk out there that can illuminate what is going on?  And is there any simple ways to extend the shelf life of their milk.  I know a number of people that won't buy the dairy farm milk simply because it won't store long enough. 

Thanks or as they say here, "Salamat Po"

Tatoosh

* Thermization description at Wikipedia: http://en.wikipedia.org/wiki/Thermization

smilingcalico

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #1 on: March 02, 2011, 05:45:26 AM »
Does the milk you get remain refrigerated the whole time? There is definitely something odd going on here.  I work at a dairy that sells raw goat milk which gets a shelf life of 2 weeks. True, goat milk is naturally homogenized, but I don't think homogenization is the issue.  There are 2 things I would mention. Pasteurization does not kill all bacteria, so if it's not being kept at refrigerated temperature the whole time, you'll still find quick spoilage.  Also, if the containers the milk goes into aren't sterilized, pasteurization means nothing. What can you do? You could pasteurize the milk again yourself then maintain refrigereation.  A second option I haven't used, but have read a little about is to add hydrogen peroxide to the milk.  I don't have any amounts to tell you of how much to add, but the info is probably on the web somewhere.  It is used in asceptic packaging, and it breaks down into water and oxygen.  I am sure the second option sounds very taboo, but if it works (and I don't know for a fact that it does) then it could be a viable option.  I would love to hear other comments about this, as it's probably a concern for many others.

Tatoosh

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #2 on: March 02, 2011, 08:15:42 AM »
On our part, normally we refrigerate the milk as soon as we get it, carrying it from the dairy home in a cooler with blue ice inside.  Sometimes when we are out and about, we hear milk is available (usually first come - first serve) so we head over.  Those times no cooler, but we head right home, a 10 to 30 minute trip depending on traffic.  Usually the lesser amount of time.

Now the dairy does their pasteurization and they do keep it in a chiller, but I'm not sure when they put it in there.  I have arrived and found it packaged and in a chest freezer that is not running.  So that may be part of the problem.  However they know about the importance of chilling milk and have told me to bring a cooler, particularly when getting raw milk which is also available.

Once home, it is always kept in a very cool refrigerator and never left out for any lengthy period of time.  But the milk will turn in 4 days maximum, regardless. 

I will do some research about the hydrogen peroxide.  I was looking at that anyway as disinfectant for my (home) cheese making equipment. I was reading about the effect of chlorine on rennet and looking for something that won't have such a strong effect on it if somehow there is a trace exposure to the disinfectant in my vat or utensils. 

Tatoosh

MrsKK

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #3 on: March 02, 2011, 07:35:59 PM »
How cool is your refrigerator?  My raw milk at home is good for up to a week.  I don't drink it after that point because there is always fresh available, so why would I want to drink older milk?  However, friends were getting milk from us a year ago and said that it was only good for a few days, probably in the range of what yours is doing.  After researching everything else, they put a thermometer in their fridge and discovered that it was only cooling to about 45-46 degrees Fahrenheit, so about 7 degrees Celcius.  Once they got their refrigerator fixed and started keeping it at 38* F, (3.3*C)  their milk kept for a week, too.

I would never pick up milk and transport it for 30 minutes without VERY cold conditions.  How large is your cooler and how many Blue Ice packs are you using?  I would recommend that you freeze water in gallon or half gallon sized plastic bottles, using several of them to surround your milk.  For best quality, the coldest you can keep it is the goal.

Also, have you been able to tour their facility to see what their milking practices are?  How clean is the facility?  It would give you an idea of how clean they are with the milk.  It concerns me that they are keeping the milk in a chest freezer that isn't turned on..

I hope you get this figured out soon.  Think about it - adding peroxide to the milk might keep it from souring, but you are basically ending up with dead bacteria in your milk...

Tatoosh

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #4 on: March 02, 2011, 09:39:18 PM »
The 30 minutes would be at the top end of the trip, but it has happened.  The coolers we use are not that big, one is hard sided and we would put one or two medium-large blue ice blocks in it.  The second is one of the smaller soft side carriers and it would only take one blue ice pack.  And we were carrying smaller amounts, 2, 3 or 4 liters maximum in almost all cases.

The refrigerator is *normally* one cold puppy!  I have had to break ice off my meat in the meat chiller and more delicate fruits such as Papaya and melon occasionally come out frozen.  That said, checking is worthwhile.  And it is small,so sometimes it gets "overstuffed" and I have found the door not sealing.  That is not the normal routine though and wouldn't explain the continual 3 or 4 day life of the milk.  My last cable probe style thermometer died recently so I will stick my insta-read thermometer in the fridge for a few and see if I can discern what is going on in there. 

And as I mentioned, perhaps elsewhere, the dairy itself only guarantees the milk for three days.  So I don't think it's a "just me" problem.  That said, thank you very much for nudging me toward better transport of the milk.  As I am moving toward cheese making, I will definitely rethink how we transport and how cold we store it. 

One of the things slowing us down is the need for a second refrigerator.  Another expat is getting ready to return to the States and we will take his refrigerator, a nicely sized 12 or 14 cubic foot to augment my little 7 cubic foot unit.  That will allow me some storage space finally.  Woo Hoo! 

smilingcalico

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #5 on: March 03, 2011, 03:50:29 PM »
LOL, Mrs.KK, your response was great, but I had to laugh about the dead bacteria in the milk due to adding hydrogen peroxide. That is what we are striving for. That is also what pasteurization accomplishes! 

Tatoosh

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #6 on: March 03, 2011, 11:00:15 PM »
I would love to figure the "going bad" aspect of this.  I will pasteurize my raw milk, even though I do understand there are benefits to using it raw, but the downside, particularly here in the Philippines are just too drastic to risk it.  I have to no control over the dairy practices and while they are very nice people, that won't make some that gets sick better. 

Now, even my UHT heavy cream goes bad after awhile.  I don't use it a lot since my electric ice cream machine broke, but occasionally I get tired of coffee mate in my coffee and long for something that's actually dairy to mix in.  Milk is a bit thin, even the whole cream milk.  If I can get the local dairy milk and its resulting components, such as cream to be fairly stable, I can make a batch of half and half for my coffee, which will then be the envy of many of my coffee swilling friends from North America and Europe. 

And if there is a simple way to keep the milk good for a week or so, similar to the milk we bought in the USA and threw in the fridge, that would benefit the dairy here since they often have excess milk.  The expats often won't buy it, preferring a more stable if less tasty UHT product. 

I won't be adding HP to milk I want to make cheese with, but if a few drops per liter is safe for human consumption and along with proper storage, would provide a reasonable shelf life, I will check it out.   However, a quick search on the internet had me bumping into a reference where the FDA has a maximum of Hydrogen Peroxide in for human consumption at 5 PPM or five parts per million.  So ...

ppm = (mass of solute / mass of solution) x 10^6        <-- from Answers.com
3.00 = (mass of solute / 2000 g) x 10^6
3.00 / 10^6 = mass of solute / 2000 g
2000(3.00 / 10^6) = mass of solute
0.00600 g = mass of solute (Answer)

So we would have something along the lines of 2000(5.00 / 10^6) which, if my handy dandy calculator is correct, would be about five drops in 50 liters.  One drop of hydrogen chloride per ten liters or 0.05 milliliters.  We are getting down where it is too small for my old eyes to measure. 

So it goes. 

coffee joe

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #7 on: March 04, 2011, 12:59:13 AM »

Temperature during the entire collection and transportation process of milk is the most important factor for shelf life. Milk quality before cooling is problematic in Tropical countries. Here in Brazil we find that most farmers create their own problems with milking by hand in unsanitary conditions. Conditions are also often critical in high number of cows with Mastitis and somatic cell count well over 1,000,000. These factors will all decrease the shelf life of milk even with proper cooling. Often down to but a few hours. 
While we work hard to keep our milk to strict standards of < 7,000 total Bacteria/Ml, most producers here have a hard time keeping under the legal maximum of 750,000. Cooling does not help milk that starts out with this level of contamination.
USDA Grade A milk quality standards allow a maximum of 100,000 bacteria/ml in raw bulk milk.

Tatoosh

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #8 on: March 04, 2011, 06:19:12 AM »
In my post I said Hydrogen Chloride, and I meant, Hydrogen Peroxide, of course.  My bad, I'm hunting some Calcium Chloride and me little brain got all befuddled. 

CoffeeJoe, thanks for the info on count acceptability. Down the road if I make cheese for commercial use, such in a pizza shop, I may just have some samples checked so I know what I am dealing with, providing I can find a lab locally.  The co-op's equipment is rudimentary, nothing to check fat level, nothing to separate cream out.  So doing cultures and checking counts is likely not done.

Is there any way I can tell, as a consumer, if the cattle have mastitis? I do know they have and use milking machines, since I directly inquired if they were milking the cows teats all the way or leaving some for sharing with calves. They assured me that they were milking their cattle all the way down using milking machines, not by hand. 

Tatoosh (a sour old guy with a taste for sweets)

coffee joe

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #9 on: March 04, 2011, 09:39:20 AM »
To test for Mastitis, we use the CMT or California Mastitis Test. This is done twice a month on the entire herd. Another very simple test, done before every milking is the first "squirt" is taken by hand before placing the milking machine onto a cup with a black screen cover. Mastitis will show as small globules of white upon the screen.

Both are very simple and inexpensive if done regularly.
http://www.infovets.com/demo/demo/dairy/d100.htm

MrsKK

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Re: Milk, Pasteurized - Souring At 4 Days
« Reply #10 on: March 06, 2011, 02:53:50 PM »
LOL, Mrs.KK, your response was great, but I had to laugh about the dead bacteria in the milk due to adding hydrogen peroxide. That is what we are striving for. That is also what pasteurization accomplishes! 

Yeah, it's those high allowable somatic cell counts that get to me - and the thought of all that dead stuff floating around in the milk I drink.  Exactly why I keep my own cow, know how healthy she is and how clean my milking practices are.
 
I know that not everyone can do that.  When the day comes that I can't keep my own cow anymore, I probably won't drink milk anymore, nor make cheese.  I pray that day is many decades in the future!