The following is excerpted from “One Mother’s Thoughts — Milk 101: The Skinny on Pasteurization, Homogenization and Dating of Milk“, from Peach Blog‘s May 9th newsletter. Text bolding added for emphasis by The Bovine:
“HOMOGENIZATION
Fat is less dense than water so cream (fat) floats above the watery part of the milk, naturally. Homogenization forces the cream (fat) to stay combined with the watery part by exposing the milk to high pressure, turbulence, and shock waves. When milk is homogenized, it MUST be pasteurized, as it goes rancid very quickly. On the other hand, HTST Pasteurized milk does not NEED to be homogenized because it won’t separate as the enzymes are not destroyed as much because only light pasteurization is used. Spokane Family Farm’s milk falls into this category. It is Pasteurized Non Homogenized, and can still be used for cheese making. UHT Ultra Pasteurized milk is ALWAYS homogenized to mix in the unsightly dead sludge that would form at the bottom of the carton without homogenization (out of sight out of mind). Making cheese with UHT Ultra Pasteurized milk will not work as there are not enough live enzymes remaining to grow.
PASTEURIZATION
Pasteurization is not intended to kill all pathogenic micro-organisms so even pasteurized milk has beneficial buggies.
HTST (Pasteurization) requires heating milk to 145 degrees for half an hour. This milk has a shorter date stamp. Organic Valley stamps this milk 18 days from the day it is bottled. This one works well for cheese making but people tend not to buy it because they are looking for the longest dated milk.
UHT (Ultra Pasteurization) requires using heat and pressure to reach 280 degrees for a few minutes. This milk has a longer date stamped on the carton. Organic Valley stamps a date 56 days from the day it was bottled.
UHT (Flash Pasteurization) kills the most stuff. This is the milk you will find in aseptic containers sitting on the grocery shelf.
Raw Milk is not pasteurized or homogenized at all; it is straight from the cow or goat, cooled quickly, and date stamped (9 days for raw cows milk, 21 days for raw goats milk). Raw milk does not go rotten, it just sours, which has been used for its human health effects since humans have been using milk….”
The Bovine 
I would not want to use this info in court as it is not right,sorry
still one vote
OK, so Bernie, set us straight. What’s not right about it?
Here’s part of what Nina Planck says about why milk is homogenized:
“Homogenization became common soon after pasteurization. It solved two practical problems in the dairy industry. The first was the cream line. With pasteurization, milk could be shipped long distances. In transit the cream rose to the top, which meant the most valuable part of the milk-the fat-was unevenly divided from one customer to another. Homogenization distributes the cream evenly, so everyone gets a share.
The other problem, according to author and dairy farmer Joann Grohman, was purely aesthetic. After pasteurization, dead white blood cells and bacteria form a sludge that sinks to the bottom of the milk. Homogenization spreads the unsightly sludge throughout the milk and makes it invisible. Ironically, white blood cells and beneficial bacteria are one of the healthiest things about raw milk. But once they’re zapped with heat they’re useless, and rightly regarded as a waste product….”
from: http://www.ninaplanck.com/index.php?article=milk_homogenized
I started in the milk pasteurization business when there were two choices ,cream top and homogenized. In those days the milk on the farm was milked by hand and put into a tin eight gallon can then some farmers ran tap water over the warm can to cool it down and others just left it for the dairy to pick up. At the dairy we would dump the milk into stainless steel vats through a strainer to catch any straw ect. The vats had a space between the outer shell and inner shell were steam and cold water could flow this is how pasteurizing works first we would run steamy water through the shell until the milk in the inner shell would reach about one hundred and sixty at this temperature we would hold it for thirty minutes at this point the steam was turned off and cold town water was turned on so the milk would begin to cool and then it would be pumped through a filter to the homogenizer which was left at zero p.s.i. for cream top and set to fifteen hundred p.s.i. for homogenized so that the customer could drink a smooth well blended product with out the cream rising to the top and on to a cooling plate to bring the milk down to the temperature of the town water and into the bottler this milk was then sold in home delivery that day and had a life expectancy of three/four days, remember this is when mom stayed home . This practice killed all the germs that are harmful to humans. From this point other equipment was added but never for improved health reasons it was because mom and dad both had to work to afford to raise the family and would buy milk at the store once or twice a week and they did not want spoiled milk(spoilage ocher’s in all milk raw or pasteurized as we do not kill all the germs just the harmful ones . The High Temperature Short Time pasteurizer replaced the vat system to improve production volume per day the cool filtered or UTS system was introduced to kill as many good and bad bacteria’s in the milk to achieve longevity for the product because the government got rid of all small local dairies in favor of the big three and now your milk takes up to fourteen days just to get to some stores but by doing this you change the flavor and take out the bacteria that is good for us . Over time a lot has changed beginning at the farm as instead of old tin cans we now put milk into a stainless steel vat that cools it down to forty F. and there are samples taken at the farm with every pick up by stainless steel ,insolated trucks and the lab can detect a problem shipment in forty eight hours . I have gotten a little of track here but I am attempting to show you that the homogenize is used for and that all milk is filtered and sludge never seen that in thirty years of dairy it must be at farm level and never shipped to the dairy, I have also tried to point out that the milk is handled totally different now then it was when the milk laws were invented as and you can probably see . I would have to write an article to explain every thing but I hope this helps
still one vote
I would be willing to bet that the milk in Michcal Schmidts farm tank is as good for you as the milk that was pasteurized up till the seventies as the farm handling is better ,milk cooled and the bactiria levels are way lower at the moderan farm,remember pasteurization only kills about sixty five % of bactiria in those days
Bernie, thanks for the explanation. Were you taking exception to the statement that it’s “necessary” to homogenize UHT pasteurized milk to hide the sludge that forms during pasteurization? You mention the milk is filtered before the processing you described begins. However, I think this author is specifically referring to sludge that forms as a result of the UHT pasteurization process, which I imagine is a process you wouldn’t have used, and is only used now to achieve extremely long shelf life.
Sorry for my mistake and you are right ,I have no knowledge of the fisical make up of UHT treatment of milk ,but I did have Gay Lea package millions of Sun Rise carton milk with this process because my plant was running at full capacity and sales for our local product would not stop growing. The Dairy inspection team gave me permission to build a new plant in Wingham but that was the same year that the Farm Products Marketing Commission and the Milk Marketing Board (dairy farmers of Ontario ) had the secrete meetings about me and stop shipping milk to my plant in favor of the new dairy that entered Canada that year.
Bernie
I’m surprised that raw milk only gets a date stamp of 9 days. I’ve been drinking raw milk for over three years now and almost three year from a purebred Jersey herd. I get the Jersey milk once every two weeks and have never had it go sour in two weeks time. Once I had a little left over and it started to sour at 16 days, and of course, I drank it anyway 🙂
I remember reading somewhere that Organic Pastures had lab tests done where their raw milk was inoculated with pathogenic bacteria and then tested a day or two later and the pathogens were gone. Seems to me the keys to the best milk quality are healthy cows and sanitary milk handling – not pasteurization. I want those good microbes and enzymes!