Why You Can Probably Keep Milk Longer Than You Think (and Why You Should)

Nearly a third of the food produced globally is not eaten each year. This waste often occurs along the supply chain before the food reaches us. But consumers who throw away food because it has spoiled, or because they think it might be spoiled, are also responsible for a large proportion of food waste.

All food production results in greenhouse gas emissions. So food waste isn’t just bad for your pocket – it’s bad for the environment as well.

Recently, Morrisons supermarket announced that it will be switching from placing “use before” dates to “best before” dates on milk. She says this could save seven million liters of her private label milk from being wasted each year.

According to the British charity WRAP, milk is the third most wasted food in the home (after potatoes and bread) with more than 490 million pints thrown out in the UK annually. So changing the advice to encourage people to keep their milk for longer is likely to be good for the planet. But is this move safe for consumers? The short answer is yes.

First, let’s look at the terms “used by” and “best before”, which have confused consumers for a long time.

“Use by” is the date when manufacturers know the product will still be safe. This is based on scientific analysis that has determined how long the product can be stored before there is a risk of any dangerous microbes reaching levels that could cause harm. You’ll see use dates on foods that could pose a risk if stored for a long time, such as cooked meats and dairy products.

The “best before” is about product quality. This date tells you how long you can keep something before the product starts tasting less fresh, or has lower quality (for example, how long you can store bread before it gets a little stale). But this does not mean that the product is not safe to eat after this date. You’ll likely see better before dates on preserved products, such as canned or frozen foods, which you can keep safely for a long time.



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What about milk?

You might think that milk should fall solidly into the “use by” category – it’s a dairy product after all. But in reality, going to a better date before is actually safe for consumers, thanks to a process called pasteurization. During pasteurization, milk is heated for a short time to a high temperature. This kills bacteria that can be present in raw milk and cause infection in humans (often called “pathogens”).

Although the pathogens are killed in the process, some harmless microbes remain in the pasteurized milk. So the milk is stored at a low temperature (in the refrigerator) to slow the growth of these remaining microbes. However, they will continue to grow, and it is the growth of these harmless bacteria that causes the milk to spoil. As the microbes grow, they produce enzymes that help them break down the milk, causing the milk to curdle and produce the “separate” smell we associate with spoiled milk.

In particular, for pasteurized milk (and we need to be very clear that this only applies to pasteurized milk) even as the milk starts to fade, there is no evidence that the microbes growing in the milk will cause you any serious harm. If you drink a large amount of spoiled milk, you may find yourself with an upset stomach but there is no indication that spoiled milk causes infections or severe illness.

Milk accounts for a large proportion of food waste.
victoras / shutterstock

The Best Before Date is the best estimate by manufacturers of how long the milk has to stay in the refrigerator before they can detect any spoilage, either by smell, taste, or both. Each batch of pasteurized milk is different and will have more or less of these harmless bacteria remaining in it, so in fact the best date beforehand is to estimate when the milk with the most bacteria in it has spoiled. But many milk infusions will be good for much longer than that—hence Morrisons change of advice.

smell test

Morrisons advised using a “sniff test” to see if milk is safe to use. This is reasonable advice. If there is no detectable evidence of spoilage, the milk is safe to drink.

If you lose your sense of smell, or you don’t want to smell milk, simply pour a little of it into a cup of boiling water as if you were making a cup of tea. if it clots and then begins to spin; If it mixes naturally, it’s OK to use it.

Should milk be discarded if it begins to spoil? If you’re only using it for drinking, it probably won’t taste very good. But milk that’s starting to shift can be safely used as a substitute for yogurt, yogurt, or sour cream in recipes like buttermilk rice, pancakes, and scones, or it can be used to make cheese sauces.

Obviously, if the milk is really spoiled (if it is completely separated, cheesy and sticky), it should be discarded.



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Again, this advice applies only to pasteurized milk. Raw milk still contains pathogens and should never be consumed after the expiration date.

Also, since different foods naturally contain different types of microbes, this advice cannot be generalized. In other types of foods, pathogens can reach dangerous levels without any real detectable evidence of spoilage. So in general, the advice is to stick to the usage date.

But when it comes to pasteurized milk, we can balance expiration dates with common sense, minimizing the impact of food waste on the planet.

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