Almost all milk now sold is ultra-pasteurized, or UHT (ultra high temperature, the method of ultra-pasteurization). And no wonder. The “sell by” date is well over a month away and the stores love that. But UHT is for the store’s benefit, not yours, and my earlier enthusiasm has faded.
A “sell by” date is not the same as an expiration date, I now realize. The “sell by” date is the last date it can leave the store. The expiration date is the last date it should be consumed. Milk only has a “sell by” date because, of course, they have no way of knowing when you open it.
Once opened and stored in your refrigerator, UHT milk will go bad in about five days, the same as milk pasteurized the old way.
This is unfortunate because I relied on the “sell by” date on the milk container in my refrigerator to tell me when to throw it out and buy new. My experience has been that expired UHT milk does not smell or taste sour, but still gives me indigestion. I have no warning of milk gone bad until after I have drunk it. The only solution I can think of is to mark on the milk container the date I opened it.
Many claim the UHT process changes the taste. I can only take their word for it. My old taste buds cannot detect any difference. They say the high temperature gives the milk a caramelized flavor. Sounds good to me. I love caramel flavor.