How to pasteurize milk at home, according to
http://www.bchealthguide.org:
"If you're living out in a rural part of British Columbia and can't get your hands on commercially pasteurized milk, you can use this method for home pasteurization:
First, make sure your milk bottles and caps are completely disinfected. Boil them in water for 10 minutes, or pop them in a preheated oven at 212º F (100º C) for about 20 minutes.
Pour your raw milk into the upper part of a double boiler. Slowly bring the temperature up to at least 145º F (63º C) and hold it right there for no less than 30 minutes. You’ll need to stir it frequently so it doesn't burn and to ensure the heat stays consistent throughout.
Use a clean, dependable thermometer to check the temp constantly. Stick the thermometer about 2/3 of the way down into the milk—don't just let it rest against the bottom or the sides of the pot. If the temperature dips below 145º F (63º C), crank the heat back up to at least 145º F (63º C) and restart your 30-minute timer from scratch.
To cool the milk, quickly place the top part of the double boiler into an ice water bath. Give it a good stir every so often to speed up the cooling process.
Once it's cooled down, pour the milk into those sterilized bottles and stash them in the fridge at 40º F (4º C).
Pasteurized milk stored in the refrigerator should stay good for up to two weeks."
Pay close attention to that last bit. Since we aren't using any additives, milk processed this way should remain usable for two weeks if you keep it refrigerated.
Here is one more Q&A from that same site. This one refers to the laws in British Columbia.
"Do people add additives or preservatives to pasteurized milk?
According to the law, vitamins A and D have to be added to pasteurized milk. Beyond that, nothing else is allowed to be added to the milk."