At Popular Mechanics, we celebrate our cultural idiosyncrasies with great enthusiasm. That established, we are happy to acknowledge a popular event known as Braai4Heritage (formerly National Braai Day), which takes place on 24 September. The man behind the movement is legendary braaimeester Jan Scannell (also known as Jan Braai), and its patron is none other than Emeritus Archbishop Desmond Tutu. In keeping with PM’s sci-tech leanings, this article examines our national obsession from a somewhat different angle. Be brave, learn something, and do not go yuck! (C’mon… do you really think beef grows in plastic punnets?)
What is meat, anyway? That’s easy: it’s mostly the muscle tissue of an animal. Muscles are made of bundles of cells called fibres, and are (roughly) composed of 75 per cent water, 20 per cent protein, and 5 per cent fat, carbohydrates and assorted proteins.
Each cell is crammed with filaments made of two proteins: actin and myosin. In a live animal, these protein filaments make muscles contract and relax. Both actions require enormous amounts of energy, which they get from the energy-carrying molecule ATP (adenosine triphosphate). The most efficient generation of ATP requires oxygen, which muscles get from circulating blood.
How does muscle turn into meat?
It’s mostly about chemical reactions. After an animal is slaughtered, blood circulation stops, and muscles exhaust their oxygen supply. Muscle can no longer use oxygen to generate ATP and turn to anaerobic glycolysis, a process that breaks down sugar without oxygen, to generate ATP from glycogen, a sugar stored in muscle.
The breakdown of glycogen produces enough energy to contract the muscles, and also produces lactic acid. With no blood flow to carry the lactic acid away, the acid builds up in the muscle tissue. If the acid content is too high, the meat loses its water-binding ability and becomes pale and watery. If the acid is too low, the meat will be tough and dry.
Lactic acid build-up also releases calcium, which causes muscle contraction. As glycogen supplies are depleted, ATP regeneration stops, and the actin and myosin remain locked in a permanent contraction called rigor mortis. Freezing the carcass too soon after death keeps the proteins all bunched together, resulting in very tough meat. Ageing allows enzymes in the muscle cells to break down the overlapping proteins, which makes the meat tender.
Okay, so what happens when meat is cooked?
Individual protein molecules in raw meat are wound up in coils, which are formed and held together by bonds. When meat is heated, the bonds break and the protein molecule unwinds. Heat shrinks the muscle fibres both in diameter and in length as water is squeezed out and the protein molecules recombine or coagulate. Because the natural structure of the protein changes, this process of breaking, unwinding and coagulating is called denaturing.
What gives meat its flavour?
Most of meat’s flavour develops when it is cooked. The amount of fat in meat infl uences its flavour, as does a process called the Maillard reaction. Flavour can be added to meat through brining and marinating. The Maillard reaction occurs when the denatured proteins on the surface of the meat recombine with the sugars present. The combination creates the “meaty” flavour and changes the colour. For this reason, it is also called the browning reaction. The Maillard reaction occurs most readily between 150 and 260 degrees Celsius. When meat is cooked, the outside reaches a higher temperature than the inside, triggering the Maillard reaction and creating the strongest flavours on the surface. The reaction produces the compelling aromas we have come to associate with the braai: as many as 600 components have been identified in the aroma of beef.
What makes meat juicy and tender?
Juiciness and tenderness are two very important factors when it comes to meat quality. Both factors are influenced by the cut of meat you choose and how long the meat is cooked. The more a muscle is used, the stronger, and therefore tougher, the cut of meat will be. And the longer meat is cooked, the more liquid it loses and the tougher it becomes. Factors that also influence tenderness and juiciness are the animal’s age at slaughter, the amount of fat and collagen (connective tissue) contained in particular cuts and, to a small degree, brining (see box).
Collagen is a long, stiff protein that is the most prevalent protein in mammals. It’s made up of three separate molecules composed of amino acid chains, twisted around each other in much the same way that fibres are twisted around each other to form a rope. This structure is what makes the collagen so strong; its strength is also what makes it more difficult to break down. The more collagen there is in a piece of meat, the tougher it is to cut and to chew.
Skin is mostly collagen, as are the tendons that connect muscles to bones. For cuts that are high in collagen, cooking with methods that use slow, moist heat, such as stewing or braising, are the best. Collagen is soluble in water and when it is cooked slowly with moist heat, it becomes gelatin. You can also make collagen less tough by slicing up meat into smaller pieces, which makes the fibres smaller and easier to break apart.
Congratulations! You now know enough to become extremely boring when you next gather with friends around a braai fire. Now go forth and burn some meat.
For more information about Braai4Heritage (National Braai Day), visit www.braai4heritage.co.za
Brining and marinating
Marinades are usually made up of three components – acid, oil and herbs. The acid helps to partially denature the meat’s proteins, opening up “tunnels” in the meat structure where flavour can seep in. But marinades mostly penetrate only the surface. They work best on meats such as chicken breast and fish because the muscle structure is not as dense as it is in steak.
For denser meat, marinades work best when the meat is cut into smaller pieces so the marinade can penetrate a larger surface area. However, if marinades are left on too long, the acids can “cook” the surface, causing the meat to dry out. Some meats, such as pork and steak, can marinate for hours. Other less dense cuts of meat, such as chicken breast and most fish, only need to stay in a marinade for a short time.
Brining meat (that is, putting meat into a salt-water solution) adds moisture to the meat through osmosis. Osmosis happens when water flows from a lower concentration of a solution to a higher concentration through a semi-permeable membrane. In meat, this membrane is the plasma membrane that surrounds the individual cells.
When meat is placed in a brine, its cell fluids are less concentrated than the salt water in the brining solution. Water flows out of the cells in the meat and salt flows in. The salt then dissolves some of the fibre proteins and the meat’s cell fluids become more concentrated, thus drawing water back in. Brining adds salt and water to the cells so that when the meat is cooked and water is squeezed out, there is still water left in the cells because water was added before cooking. Just thought you’d like to know.
Excerpts from The Exploratorium’s Science of Cooking were used with permission. (C) Exploratorium, www.exploratorium.edu
Related article: Eco-friendly tips for Braai4Heritage
Tackle the following DIY projects in time for Braai4Heritage:
1) Make your own flawless backyard steel braai
2) Convert a bin into a stylish smoker
3) Build your own braai cart , including step-by-step plans