Why does Half & Half keep longer than milk?

I would think that the more fat it contains the quicker something would go rancid. But while milk’s expiration date is usually no more than a week, half and half is more like a month! Are they able to put more preservatives in it because it isn’t drunken straight? That seems unlikely to me.

Plus those little sealed containers of half and half can remain unrefrigerated much longer than milk (and they’re not vacuum sealed). What gives?

My WAG is that milk has a higher sugar content which is easier for things to grow in.

It is possible that half and half is ultra-pasteurized which would give it a longer shelf-life.
I think this makes sense since rarely is half and half ingested undiluted and the only negative side-effect of ultra-pasteurization appears to be a change in flavor
(tasting ‘cooked’ by some sources – according to http://www.joyofbaking.com/Cream.html).

This is, of course, only a WAG.

I’ll agree with that. Whipping cream is ultra-pasteurized, and it would make sense to apply the same process to half and half. Also, it would make safety sense, as it is more likely to be left out with the coffee and tea than milk.

I disagree about it tasting “cooked”. In my experience, people who make that claim also insist, with religious fervor, of the need to warm the teapot.

Half-and-half is always ultrapasteurized: it sells more slowly than milk so grocers keep it on their shelves longer, and it also used up at home at a slower rate, among other things.

Milk doesn’t need the extra pasteurization since it is used up more quickly.

Certainly you can detect the taste different between ultra pasteurized and not when it’s not mixed with anything? I don’t find the flavor unpleasant but I would say the ultra definitely has a nutty slightly burnt flavor to it.

The little packets are UHT - UltraHigh Temperature pasteurized. Milk, treated by the same process, is also shelf stable for months (as long as it is unopened).

Half and half also contains less water by volume, and more fat. The bacteria that make milk spoil live in the water, and can’t live in the fat.

Because it has double the half-life?

Usually, not always. When I can, I buy fresh non-UHT half-and-half from a creamery. It comes in returnable-for-deposit glass bottles, and it is better than anything you get in a carton.

I think that it’s the butterfat. Have you ever noticed how fast skim milk goes bad? If you’re lucky, it might last a week. It seems to progress to longer shelf (fridge?) life for low fat, 2%, whole, half & half to heavy cream (which practically lasts forever).

Follow-up Q: How long will opened half-and-half stay good in the fridge? My self-imposed limit based on absolutely nothing is 10 days but I’m wondering if I’m throwing away what’s left over after 10 days for no reason?

I’ve noticed that the expiration dates of 2% milk are always later than 1% milk. I brought it up in another thread but was kinda brushed off. This seems to be a consistent fact. I think whole milk is even later but I don’t really buy that so I can’t confirm. Maybe it does relate to milkfat? Intuitively, you’d think that fat makes it spoil faster, but it seems that might not be true.

The skim I bought today has a freshness date of 4/26. The stores say it should be okay for a week past that, and I’ve always found that to be true.

Based on nothing but my own experience (leaving things in the fridge at my place in Vermont) ultra-pasteurized half-n-half will last up to three weeks (opened).

Higher/longer pasteurization. This reduces the number of initial bacteria present in the food and thus increases the amount of time required for them to spoil it.

Higher fat content = lower water activity.
Water activity is the most important anti-microbial factor that is considered for food preservation. It’s the reason why peanut butter/crackers/salted meat/lard/anything dried lasts so long. Hygroscopic chemicals like sugar or salt draw water out of solution and prevent bacteria from effectively using it for themselves. This is why jelly lasts such a long time. Jelly has quite a few yummy nutrients and energy sources for bacteria to consume, but they can’t do so because all the water is being drawn out of solution by the sugar. Paradoxically, if you lowered the sugar, the bacteria would grow more rapidly.

Rancidity is a process that takes place without the aid of any microorganisms. Fat undergoes a series of chemical reactions which oxidize it and create a bunch of unwanted products like butyric acid that smell something awful. This is accelerated by contact with oxygen, light, and free radical producing species. Food manufacturers often use special containers which block light and alter gas concentrations, and antioxidants like BHT to suck up free radicals and prolong the time needed to turn rancid.