We cook meat to make it nicer to eat because it is more tender and flavorful than raw meat, and to make it safe to eat by killing harmful bacteria that may be on the meat. In order to be become better at cooking meat, it helps to know what meat consists of and what happens to it when we cook it. And so I am writing a series of articles about this topic. In this second part I will start by explaining the factors that affect the tenderness of raw meat, and finish with how to tenderize meat. In the following parts I will cover succulence, flavor, appearance, and food safety.

Factors affecting tenderness

Tenderness is the amount of force that is needed to bite through and chew meat. The three most important factors that determine meat tenderness are:

1. the cut, from which part of the animal did it come
2. quality of the meat: how the animal was treated while alive and how it was slaughtered
3. the breed, the age of the animal, and whether the animal was male or female

1. The cut

Meat is muscle, and most muscles are used to power the animal. Muscles have to be strong, and they are strong because they are a composite structure of two types of fibers. These are muscle fibers that cause movement by changing in length, and collagen fibers that reinforce the muscles and (with the help of tendons) connect them to the bones. The muscle fibers are organized into bundles at different levels by collagen sheaths. The bundles are visible in the meat as the ‘grain’. Tender meat is fine-grained with a thin and weak collagen sheath, whereas tough meat is coarse-grained with thicker and stronger collagen.

Whether meat is tender or tough depends on what the muscle was used for while the animal was still alive. Small muscles that do not have to do a lot of heavy work during the animal’s life are finer grained and are tender as meat. Large muscles that do the heavy work are coarser grained and will yield tougher meat. With this knowledge, you can figure out how tender a cut of meat is going to be by thinking about where it used to be on the animal and what the muscle was used for during its life. Here are some examples:

• (tender)loin: tender
• shoulder, rump, leg: intermediate
• neck, shank: tough

2. Quality of the meat

The quality is determined by how the animal was treated while it was still alive and how it was slaughtered and butchered. For example, if cattle has been kept in the rain in cold weather before slaughtering such that the animals are shivering, the rigor mortis will set in too soon and the meat will be tough. As a consumer we can’t control such factors directly. But we can control it by choosing to buy meat from a reputable butcher. In most cases, farming practices and slaughterhouse practices that will produce better meat, are also the more expensive ones. Better meat doesn’t necessarily mean it will be more tender. Organic meat that has grown more slowly, will have more flavor but may be less tender than non-organic meat of a younger animal that has grown more quickly.

3. Breed, age, and sex

Tenderness is not just the result of diet and how the cattle are raised, genetics also play their part. Some breeds are known for being more tender.

The age of the animal is also an important factor. As the animal matures, the fascicles (bundles of muscle fiber wrapped by collagen) thicken and more cross-links will strengthen the collagen. And so the meat of older animals is tougher than that of younger animals.

Finally, male animals have larger and stronger muscles than females, and so the meat of females is more tender.

How to tenderize meat

The four main strategies to tenderize meat are (in the order that they are usually applied):

1. aging
2. slicing and pounding
3. marinating
4. cooking

a. Aging

When an animal has been slaughtered and rigor mortis has set in, enzymes in the meat called calpains and cathepsins will continue to function and will break apart the muscle tissue so that the meat will become tender. At refrigerator temperatures (5C/40F) this will go on for about 48 hours in chicken, and up to 21 days in beef. Pork (5 days) and lamb (7 days) are in between. Some interesting facts about aging:

• If meat has already been aged for the maximum time as indicated above, additional aging will make no difference for the tenderness.
• To achieve tenderness, wet aging (vacuum packed) is the same as dry aging. The difference is in the flavor: dry aging will concentrate the flavor because water will evaporate from the meat, and if done for a very long time (longer than 4 weeks or so) it will add nutty/cheesy flavors.
• If beef hasn’t been aged, you can speed up the process of aging by increasing the temperature as described in this post about warm aging.

b. Mechanical

Muscles gain their strength from their structure, and thus meat will become tender if you break down the structure by cutting through the collagen reinforcement present in the meat. This is why meat sliced against the grain (thus severing the bundles of collagen in the meat) is more tender.

Pounding is also a way to make meat more tender, although it is most often used to flatten cuts that are already quite tender and in those cases one has to be careful not to destroy the structure of the meat.

A special way of mechanically tenderizing the meat is by jaccarding it. You may have seen a butcher ‘staple’ a steak or another piece of meat. This isn’t really stapling, but in fact inserting a lot of very thin and very sharp blades into the meat. This will slice through the collagen structure and thus make the meat more tender. You may think that piercing the meat will make it lose juices, but it will actually help to keep the meat more juicy, because the meat will shrink less and thus less juices will be forced out.

c. Marinating

A classic way to tenderize meat is to marinate it in a marinade that contains some form of acid, such as vinegar, wine, yogurt, or fruit juice. The acid in the marinade will break down muscle fibers as well as connective tissue. Some fruit juices, such as kiwi, pineapple, or papaya, contain enzymes that will tenderize the meat even further. Many famous recipes like boeuf bourguignon, coq au vin, or chicken tandoori use an acidic marinade to tenderize meat from older animals before cooking it. Nowadays, we eat meat of (much) younger animals and the wine or yogurt is added more for the flavor than to actually tenderize the meat as that is no longer necessary.

When marinating, it is important to consider that the speed at which a marinade penetrates into the meat is in fact quite slow. Cutting meat into smaller pieces before marinating is usually the best solution to this. Many classic recipes that will tell you to marinate an entire roast overnight do not make a lot of sense, because the marinade will require much longer than overnight to reach the core of the meat. This is of course only a problem if the meat is so tough that the tenderizing effect of the marinade is needed. If that is not needed and you want to keep the roast whole, you may consider skipping the marinating step and just using the marinade ingredients to make the sauce.

Most marinades contain salt, which also helps to tenderize muscle fibers. However, salt doesn’t tenderize the connective tissue.

d. Cooking

When meat is cooked, it becomes tender as the high temperature forces the proteins to denature. It is the connective tissue that makes the meat tough, so the most important factor is collagen turning into gelatin, which starts to happen above 52C/126F. The speed at which this happens increases with the temperature. At temperatures just above 52C/126F it is very slow and it can take days to dissolve the collagen into gelatin.

At temperatures above 85C/185F even tough cuts only require hours of cooking to become tender, and in a pressure cooker (where temperatures can reach 115C/240F) even tough cuts can become tender in less than an hour.

There is a drawback though to using high temperatures to quickly tenderize meat that is very tough. As I explained in the previous post about juiciness, above 57C/135F the collagen in the meat will start to contract and thus squeeze out the juices. The first thing that will happen if you heat meat above 85C/185F (which is what happens in traditional braising and stewing recipes) is that the meat will actually become very dry and very tough because of the shrinking collagen. Cooking it longer will subsequently make it tender and flaky, but it will remain dry (no matter how much liquid you add to the pan). This is where fat comes in to save the day, but that is the topic of another article. Another solution is of course to use sous-vide cooking to cook the meat at a temperature that is so low that the collagen won’t contract as much so the meat will stay juicy, but long enough for the collagen to convert into gelatin.

Further reading: Modernist Cuisine, by Nathan Myhrvold et al.