Food

Heres The Clever Chemistry That Can Stop Your Food Rotting

The Conversation

A hotel in Reykjavk has on display a McDonalds burger and fries, apparently undecomposed after 2,512 days and counting. It was bought on October 30, 2009, the day that the last McDonalds in Iceland closed. But you dont have to go to Reykjavk to see it: it has its own webcam so you can watch it from your armchair.

What stirs this dinner so long-lived? Well, I havent examined this particular burger myself, but chemical reaction make meat to decompose and understanding them can help us to keep meat most effective and for longer.

Lets start with uncooked rice in many people minds its a foodstuff that will retain for a long while. Experts reckon that polished lily-white rice will retain for 30 times when properly sealed and stored in a chill, dry place. This means in an airtight container with oxygen absorbers that remove the gas that they are able oxidise molecules in the rice.

Hotter food goes off faster; as you may recollect from school science lessons, chemical reactions are faster at high temperature because hotter molecules have more vitality and so are more likely to react when they collide. Its one reason “were having” fridges. But there is a limit. Above a certain temperature( approximately 50 -1 00 C ), the enzymes in a bacterium get denatured their active locate, where its catalytic activity happens and it bind to molecules to carry out reactions on them, loses its shape and can no longer carry out reactions.

Back in the 19 th century, Louis Pasteur invented the process that bears his epithet. Pasteurisation kills the bacteria that stir meat come off and today this is applied mainly to milk. Milk that has been pasteurised by heating to merely over 70 C will retain for two to three weeks when chilled, while UHT milk, make use of heating to 140 C, will keep in airtight, sterile containers for up to nine months. Raw milk left in the fridge would last only a few days.

Living off the property

The short life of meat was the reasons why medieval armies lived off the property by scavenging, but in 1809 a Frenchman identified Nicholas Appert won a award offered by his government for a process for retaining meat. He showed that meat sealed inside a container to exclude air and then cooked to a high enough temperature to kill microbes such as Clostridium botulinum prevented for a long time.

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Clostridium botulinum bacteria. Shutterstock

Hed invented canning, which came into widespread use, and not just for feeding armies and jaunts it was immediately taken up by the civil sector, too. Tinned meat surely works. Sir William Edward Parry, for example, took 26 tons of canned pea soup, beef and mutton with him in 1824 on his expedition to find the Northwest Passage. One of these mutton cans was opened in 1939 and be considered to be edible, if not very palatable.

Conversely, cold slackens germ proliferation. Continuing meat at around 5C in a fridge slackens microbial proliferation but it doesnt stop saying that. People living in very cold regions like the Arctic detected this sooner, of course, without the is necessary to fridges. And watching the Inuit fish under thick-skulled frost made Clarence Birdseye the notion of fast-freezing meat; this creates smaller frost crystals than ordinary suspend, ensuing in less damage to cell walls, so the meat is not simply prevents for longer but also savours better.

Sugar and spice and all things nice

Beginning with communities in hotter parts like the Middle East, dried meat has been around for thousands of years the earliest cases are thought to date back to 12,000 BC. Drying meat, whether using the sunlight( and breeze) or modern factory procedures, removes liquid from the cells of the microbes that break down meat. This stops them reproducing and ultimately kills them.

An extension of this is the use of salt( or sugar) to conserve meat. While salt beef and pork may conjure up conceives of the Royal Navy in the days of Jack Aubrey and Stephen Maturin heroes of Patrick O’Brians Napoleonic novels the process goes back much further than that.

Master and Commander: Aubrey and Maturin.

In the Middle Ages, salted fish like herring and cod is commonly eaten in northern Europe, and fish was of course essential during Lent. The cells of microbes have walls that are permeable to water but not to salt. When the cell is in contact with salt, osmosis takes place, so liquid moves out of the cell in order to try to equalise the salt concentration inside and outside the cell, and eventually so much better liquid is removed from the cell that it dies. No more bacteria.

Sugar has a similar consequence, just think of fruit preserves, jam-pack or jellies. Smoking also dehydrates out meat. Some of the molecules formed when timber is burned, like vanillin, will add flavours, while others, including formaldehyde and organic acids have preservative properties.

Freeze-drying is an up-to-date route of removing liquid from meat, perhaps this is the kind of coffee that you use. Modern manufacturers are tapping into something that the Incas in the High Andes developed 2,000 years ago to prepare freeze-dried potatoes, known as chuo. The practice continues today. Potatoes are left out overnight, when freezing temperatures are guaranteed, then they trample on them, bare-footed, to mash them up. The scald sunlight then accomplishes the number of jobs you have a meat that will retain for months, meat either for the Inca armies or the peasants of Bolivia and Peru.

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T urmeric: hidden powers. Shutterstock

How about spices? Well, both onion and garlic have antimicrobial properties. There is evidence that the use of spices in warmer climates is linked with their antimicrobial properties, so adding them to meat going to be able to preserve it.

The antibacterial activity of some spices , notably cinnamon and coriander, is probably due to the aldehydes reactive molecules containing a CHO group, formed by oxidising alcohols and including hexenal, the molecule we smell when grass is freshly cut they contain.

The spice that has got most attention is turmeric, made from the roots of a plant in the ginger household, Curcuma longa , and especially a molecule it contains, called curcumin. Turmeric was used in meat in the Indus valley over 4,000 years ago, as well as in medicine. Today, it may be a useful cause molecule against Alzheimers malady, as well as possibly interfering with various signalling pathways to participate in cancers.

So there is sound science behind the processes used to preserve meat and some of these substances may have hidden benefits to our health. That hamburger in Iceland, however, is still a mystery. There surely have been slew of media tales trying to get the bottom of its apparent immortality but the only route to be sure would be to topic it to rigorous scientific enquiry. Perhaps Ill book my flight.

The ConversationSimon Cotton, Senior Lecturer in Chemistry, University of Birmingham

This article was originally published on The Conversation. Read the original article.

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