Food waste is such a huge problem – we indulge in shopping, and let’s be honest at the end of the week a lot of our food lands in the garbage bin. I hate wasting food, especially knowing so many people starve – it should be fined. To reduce your food waste, good planning is of the essence. However, there is another factor that plays into this: many people don’t actually know how long food stays edible and rather than take a risk, they throw it away. These days, with a few exceptions, food keeps a lot longer than the “best by ” dates printed on the package.
I myself am a very bad combination: I am a bit of a hypochondriac and additionally a biochemist. Do you remember the saying “ignorance is bliss”? Well some days I wish I didn’t know what I know😊 My brain tends to go to the worst-case scenario: if I eat something that has been in the fridge for 3 days I will die! This may be a little bit over dramatic – but the question remains: how long do certain foods keep? And what happens after that point? So I decided to get into research mode and write an article about it!
Now please take all this with a pinch of salt, I can not predict your actions or see into your fridge. As you will see later on in the text, many things play a role like temperature and hygiene. Also I am not a medical doctor, although I do have a doctorate in biochem😊 and I do know my stuff. Always be critical, be reasonable and don’t sue me!
What happens when food spoils?
Food spoils when harmful microorganisms contaminate our food, grow on it and/or secrete some chemicals that are toxic for us. The most common food born pathogens are salmonella, E.coli and the norovirus for example. Sometimes the microorganism itself is harmful, sometimes they secrete harmful and dangerous toxins. However not all microorganisms are harmful – for example we need many good bacteria for our digestion. The good bacteria in our body is called our microbiome. Generally, the microbiome describes all of our bacteria, but the term is usually used to designate beneficial bacteria.
Food spoils when left too long in certain conditions like humidity or at room temperature. Food will also spoil when refrigerated, but at a lot slower pace. One thing that I wanted to talk about is the “best by” dates. In my eyes these dates are just guidelines, except for meat. I always consume the meat before the date it says on the packaging. For the rest I try not to be too strict and trust my senses. In most of the cases, products won’t spoil for weeks after there “Best by” dates, and are absolutely safe for consumption. A good example is cheese – initially this product is left for months to ripen under certain conditions and then suddenly someone decides it gets a “best by” date..
What role does temperature and humidity play?
I will mostly talk about bacteria, although food can also spoil through fungal or viral contamination. Between a certain temperature range, bacteria will feel very comfortable and given a source of food and water, they will divide or grow very quickly. This happens the quickest at a temperature range between roughly 5°C and 60°C depending on the microorganism. This temperature range is commonly called “the danger zone”. Temperature strongly influences how quickly microorganisms can grow. Harmless baker’s yeast for example divides once every 90 minutes, whereas E. coli can divide as quickly as once every 20 minutes. This means that food at room temperature can spoil extremely quickly. If you forget certain foods outside overnight, it is safest to discard it completely.
If you store food in your fridge, 4°C or under is an ideal temperature as it inhibits bacterial growth to a certain extent. However, cooling your fridge down to such low temperature is also a non-negligible energy expense, so nowadays you have the option of buying fridges with different temperature zones. Freezing your food is also a great option to preserve it, if you want to prepare foods in advance or make sure you have certain foods and vegetables ready even out of season. How the quality of your foods is affected, depends on certain factors like water content or freezing temperature. But generally, if done right, freezing will preserve your foods for a good while without major loss of quality.
Some foods and how long they keep!
Meat is tricky. Many of us enjoy a rare steak , raw carpaccio of beef tartar. For these dishes, make sure the quality of your meat is impeccable. Make sure to always keep your meat refrigerated as well as separated from other foods you may want to consume raw. Keep them packaged or in a closed (plastic/glass) box. Minced meat should be consumed within the same day, maybe the day after. Minced meat is finely chopped up and carries a high load of contaminating bacteria. The same goes for poultry – make sure to cook it within a day or two. After it is cooked, meat will keep a few more days in the fridge, so if you know you won’t be able to eat it, then either cook it or freeze it, so it won’t get wasted.
- Fruit & veggies
Fruit and vegetables differ greatly when it comes to storage and “best by” dates. With fruit and vegetables, you can generally go by your senses – if they look and smell ok, they should be. Store vegetables like potatoes in a dark and cool place, this avoids them starting to sprout. Some fruits and vegetables like moisture, some don’t. Produce like salad, asparagus or rhubarb like moisture and should be kept in the fridge. Tomatoes, onions or garlic don’t like moisture and should be kept at room temperature at a dry place.
A great way to preserve seasonal fruits and veggies is to freeze them – that way you have them available all year round. Different foods lose quality when frozen, so they shouldn’t be kept in the freezer for too long. A few months is usually a good guideline, as soon as it is longer than a year, products often loose flavor and/or quality.
- Rice & honey
Rice and honey are 2 of the only foods that will never spoil. First and foremost, when properly sealed, honey has almost no water, a prerequisite for microorganism growth. Honey is made primarily of sugar – a highly hygroscopic chemical (it attracts water). Sugar pulls moisture out of any microorganism that would come in contact with honey and in effect dry it out. If left unsealed, honey would accumulate moisture and eventually spoil. Through the action of enzymes in bee secretions, honey is also highly acidic and contains hydrogen peroxide – both factors that prevent microorganisms growth and survival! White rice has been found to stay edible for 30 years when kept in an oxygen free environment and at low temperatures. Brown rice not so much (only around 6 months), as it contains some natural oils in its outer coating.
Eggs are always tricky – useful Facebook hacks promise to show you if your eggs are still fresh or not. Especially if you prepare food with raw eggs like mayonnaise or certain salad dressings, it is extremely important that you can trust your eggs are fresh and won’t make you sick as they can carry pathogens like salmonella (although nowadays chickens are usually vaccinated against these bacteria.).
If eggs are handled properly and their shell is undamaged they can keep for quite a while (a few weeks even). The problem with eggs is when the shell is damaged, bacteria can enter the egg, grow and spoil the product. The same goes for hard boiled eggs. Although they are commonly kept even at room temperature, the shell should be undamaged as the egg offers an ideal environment for bacteria to grow. To avoid bacterial growth or slow it down, always keep eggs refrigerated. You can also easily freeze them without their shell in a suitable container. Frozen they can keep up to a year.
- Oils and fats
Oils and fats can go bad. When in contact with humidity or oxygen (sometimes even light), they can go rancid and lose their flavor. But fats and oils carry another risk – botulism. This ubiquitous bacterium likes environments low in oxygen and can start producing it’s highly poisonous toxin. That’s why you should never use fresh herbs or vegetables like garlic to make your own infused oils. Produce needs to either be heated to a certain temperature or acidified below a certain pH for it to become safe.
There are many ways of reducing food waste, but knowing how to handle your food products is very important too. Generally cooked food will keep another couple of days in your fridge, especially if refrigerated quickly after it was prepared.
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