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:
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 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….”