A long while back, I was at Safeway looking at the different brands of milk they carried and most of them had an expiration date of a week or 2, but there was this one brand, Darigold that had an expiration date of at least a month and a half away. I asked an attendant walking by if he knew why this particular milk lasted so much longer and if there was any preservatives in it. He shrugged and said he wasn’t sure.
I mean, to have milk last that long, one must’ve added a whole bunch of preservatives in it.
Let me step back and give a little explanation of why I was looking into this. This milk isn’t cheaper, but if I recalled correctly, it cost about $0.10 to $0.20 more. But I hardly eat at home, and I never eat breakfast. Work has milk if I really wanted milk and the only time I’d ever get to drink milk at home would be on the weekends. So assuming I do eat cereal every weekend, that’s only 2x per week. A regular half gallon of milk would most likely be only utilized about 50% before I pour it down the drain. Therefore, I was very interested in this Darigold milk that lasts 1.5 months.
Anyway, Xyon, Aurash, and I were talking about milk awhile back. I hope I spelled Aurash’s name correctly. Anyway, Xyon hates milk with a passion. Well, more like he doesn’t like the taste. Aurash actually likes milk and would like to drink or use it more, but he is lactose-intolerant (sorta like my father), which is a condition where his stomach lacks an enzyme to break down lactose in milk, which ends up causing upset stomachs. I mentioned to him about Lactaid which actually makes milk products for lactose-intolerant people or he could opt for pills which do the same thing.
Anyway, back to the story, we got to the point of pasteurization and Xyon was telling us how the pasteurization process was initially developed to kill bacteria in beer from causing it to taste bad. The pasteurization process actually involves heating a liquid to a certain temperature where all the bacteria die. However, this process also ends up breaking down a bunch of organic material which causes milk to expire really fast. The process is no longer used for beer since as you can see, beer can last for months. However, they adapted this process to milk to kill off most bacteria.
I brought up the ultra-pasteurization milk that I had seen and purchased and he also didn’t know much about it, but if it was ultra-pasteurized, the name itself seems to imply strong pasteurization which should lead to shorter shelf life.
I went home and searched for pasteurization on Wikipedia. This is what I found out:
Pasteurization typically uses temperatures below boiling since at temperatures above the boiling point for milk casein micelles will irreversibly aggregate (or “curdle”). There are two types of pasteurization used today: high temperature/short time (HTST) and ultra-high temperature (UHT). There are two methods for HTST pasteurization: batch and continuous flow. In the batch process, a large quantity of milk is held in a heated vat at 63 °C (145 °F) for 30 minutes, followed by quick cooling to about 4 °C (39 °F). In the continuous flow process, milk is forced between metal plates or through pipes heated on the outside by hot water. UHT processing holds the milk at a temperature of 138 °C (250 °F) for a fraction of a second. Milk simply labeled “pasteurized” is usually treated with the HTST method, whereas milk labeled “ultra-pasteurized” or simply “UHT” must be treated with the UHT method.
Pasteurization is typically associated with milk, first suggested by Franz von Soxhlet in 1886. HTST pasteurized milk typically has a refrigerated shelf life of two to three weeks, whereas ultra pasteurized milk can last much longer when refrigerated, sometimes two to three months. When UHT pasteurization is combined with sterile handling and container technology, it can even be stored unrefrigerated for long periods of time.
Very interesting. Looks like from now on I’ll be picking up more Darigold Ultra-Pasteurized milk. The image of my milk above has an expiration date of July 27 2007 and was actually purchased 2 weeks ago. Usually, 2 weeks after I purchase a carton of milk, I’ll need to pour it down the drain already. This one has almost an entire month left!
What I really want to know is, how long does unpasteurized milk last. I found this site: A Campaign for Real (Raw) Milk!, which is a group trying to bring back unpasteurized milk because it’s “natural”. I’ve read it a bit, but not really for or against it. It’s interesting though that the pasteurization not only destroys bad bacteria, but also good bacteria along with helpful enzymes and vitamins. However, they didn’t mention anything about expiration dates or shelf life.