The Science of Marinades

Every year as grilling season rolls around, dads, moms, and general appreciators of summer cookouts knock the rust off their Webers, oil their grates, and gingerly navigate their home’s outdoor fire code. And for those who enjoy meat (and even those who don’t), many are making and using marinades to add flavor and improve texture and juiciness.

But questions about marinades linger. What are the essential elements of a marinade? What exactly does a marinade accomplish? How long should you marinate for? Is it true that marinades are just "surface treatments" that don't penetrate deeply? Are all acids in a marinade harmful to the texture of proteins if left for too long? And, are marinades even worth it?

As with most things, there's no easy answer to any of this, as it depends both on the marinade and the type of food being marinated. While this article can't account for every possible variable, we can look at some of the biggest factors. There's plenty we can learn by examining the basic science of marination as well as running tests of our own to better understand what happens when foods are marinated.

Understanding how marinades function isn't just an academic matter—it can influence how we concoct marinades and how we apply them. Since the whole point of marination is to enhance the foods we cook, we might as well make sure we're getting the best possible result when doing it. The time to submerge ourselves in the topic is now.

What is Marination?

Marination is a broad term, but the crux of it involves soaking some food in a flavorful liquid before you cook it, usually for anywhere from 30 minutes to 24 hours.

A basic marinade will contain some combination of the following:

• Water: Water can come in the form of juice, wine or beer, a condiment like soy sauce, or just straight-up water.
• Salt: Essential for basic seasoning and moisture retention*, salt can come from condiments or pure salt.
• Sugar: Whether refined, raw, brown, or in the form of a sweet ingredient like honey, sugar seasons the exterior of meats and enhances browning and caramelization.
• Aromatics: These might include herbs, spices, fresh aromatics like garlic and ginger, or even fruit rinds.
• Fat: Liquid fats such as olive oil, vegetable oil, and even sesame oil are added for flavoring; they also conduct heat more efficiently than water, so the surface of meat may cook faster when fat is present.
• Acid/Base/Enzyme: These ingredients alter the texture of meat by denaturing or digesting proteins like actin, myosin, or collagen; these effects can be pronounced depending on the concentration of the additive and the amount of marination time you choose.

*Salt partially dissolves proteins in meat (primarily myosin, which is responsible for muscle contraction), such that those proteins don’t contract as much when cooked. If the proteins don’t contract as much, the meat holds onto more water, so it tastes juicier and more tender. For a detailed explanation, read Kenji’s primer on brining here.

Why Marinate?

With respect to meat proteins, the common reasoning looks something like this: 

1. Marinating seasons the meat, primarily via salt.
2. Marinating sometimes enhances the exterior of meat by promoting browning.
3. Marinating keeps (or makes) meat tender when cooked.
4. Marinating flavors meat via aromatics, spices, or other ingredients.

Now let’s be real: Those are all broad claims. So we’ll start with what we know with certainty. 

Yes, marinating seasons meat protein via salt, and it does so effectively. We know this because osmosis and the diffusion of salt in proteins is a proven process. Heck, we have entire guides dedicated to brining and dry brining; brining, after all, is exactly what salt in a marinade is doing. I’d even go so far as to say that the most important ingredient in any marinade is salt, period. So no disputes there.

And for sure, marinating can enhance the exterior of meat by promoting browning. Many marinades contain sugar (in the form of sucrose, fructose, even glucose), which promotes browning and caramelization (see: the Maillard reaction and caramelization). In these cases, a nice crust or char can form on the surface of meat, which can have a pleasing effect on both texture and flavor.

But what about those last two claims about marination improving tenderness and flavor? The answer to whether those are true, unfortunately, is: It depends. And to really unpack those ideas, we have to start asking more specific questions. 

Here are some questions that can help us more fully explore those claims:

1. Does time in a marinade matter? 
2. Do seasonings other than salt make a difference in flavor, especially at the interior of the meat being marinated?
3. Does fat make a difference in flavor, including at the interior? 
4. Do acids, bases, or enzymes make a difference in the meat's texture and quality?

Question 1: Does Time in a Marinade Matter? (Answer: Yes)

People have all sorts of opinions on how long you should marinate meat. Two hours, 6 hours, 48 hours, exactly 18 minutes—and those recommendations often get downright Draconian in their reasoning. While I can't tell you how long you should soak your meat in the marinade you might be using right now, I can show you some trends by employing some basic testing.

To answer this question, I mixed a basic marinade of soy sauce, water, sugar, grated garlic, and vegetable oil (in a ratio of 4:3:2:1:0.5 by weight). I poured a measured amount of this mixture into separate bags containing 3-ounce samples of chicken breast, pork tenderloin, and flank steak, and marinated each sample for varying durations (0 minutes, 30 minutes, 1 hour, 4 hours, 8 hours, 24 hours). I staggered each test so that I could cook each sample at the same time and compare them fairly.

You may ask, why no acid in this marinade? Firstly, soy sauce is slightly acidic (around 5.0 pH). Plus, the inclusion of stronger acids or bases (or enzymes) in a marinade drastically complicates our ability to assess effects of base ingredients like salt, sugar, or aromatics. For more on acids, bases, and enzymes, see the relevant section below.

Here’s chicken breast (1-inch thickness) marinated at various times, prior to cooking:

Not much to note here visually, but I did notice that the 24-hour sample felt noticeably firmer than the other samples—almost like a gummy bear.

Here are the same samples of chicken breast after cooking in a carbon steel skillet to an internal temperature of 150°F:

And some selected cross-sections for good measure:

General Observations for Chicken

• Four-, 8-, and 24-hour samples were more deeply seasoned (saltier) than all the other samples, with the 30-minute sample tasting least seasoned.
• There was visible caramelization and char on samples marinated for at least one hour, with 8- and 24-hour samples showing the most intense coloration.
• The 24-hour sample was moist, but also rubbery and ham-like. There was an unpleasant springiness to the meat when chewed—almost crunchy between the teeth.
• Tasters preferred the 1- to 8-hour samples, with slight preference to the 4-hour sample for its perceived balance of seasoning, tenderness, and juiciness.
• Zero- and 30-minute samples showed virtually no seasoning at the interior; they tasted drier and less succulent than longer-marinated samples

Next is the same test with samples of pork tenderloin and flank steak.

Pork tenderloin (1-inch thickness), cooked to 140°F and rested:

General Observations for Pork

• Unlike the chicken samples, the 24-hour marinated pork did not taste over-cured or overly chewy; it was moist and well seasoned.
• The 0-minute, 30-minute, and 1-hour samples were relatively unseasoned in comparison to the longer-marinated samples; they were also less juicy.
• It seems that pork tenderloin holds up better to longer marination than chicken breast.

Flank steak (3/4-inch thickness), cooked to 125 degrees and rested:

General Observations for Beef

• The best tasting samples came at the 4-hour mark and longer, with slight preference for the 8-hour flank steak.
• The 24-hour marinated sample did not taste gummy, crunchy or over-cured.

The Bottom Line

Time in a marinade definitely matters as far as its brining effect is concerned. In general, longer marination results in deeper seasoning, better moisture retention, and increased levels of browning or char (provided that there is sugar in the marinade). But we can’t necessarily make firm conclusions on optimal timing; it depends on the meat you are using, the pH of your marinade (read Question 4 below), and even your personal preference for seasoning. But using a relatively inert marinade for poultry and red meats, there seems to be a window between 1 hour and 8 hours where the benefits of seasoning and moisture retention are greatest. For chicken breast, the meat can over-cure and become almost crunchy if you marinate it too long; for beef and pork, you’ve got some more wiggle room. Do note, though: A marinade with an acid, base, or enzyme would drastically affect this timing as well.

In contrast, shorter times in a marinade don’t deliver much of a payoff in terms of deep seasoning (or even surface seasoning) or moisture retention. It seems that there isn’t enough time for the marinade to adhere and penetrate even the first millimeter of meat. But keep in mind, this testing didn’t include more delicate proteins like fish, shrimp, or lobster—which have slightly different protein structures and permeability (so a shorter marination time may be adequate in those cases).

Question 2: Do Seasonings Other Than Salt Make a Difference in Flavor? (Answer: Maybe)

Kenji has written at length about skipping aromatics in a brine. The reason? Salt is a small molecule that passes easily through the semipermeable membrane of meat tissue; aromatics like pepper and garlic are much bigger molecules. Salt is also a highly charged molecule, so water in and around meat is more attracted to it than less-charged (non-polar) molecules.

But sound reasoning aside, people still put all kinds of flavorings and aromatics in their marinades—garlic, sugar, liquid smoke, bouillon powder, bay leaves, citrus rinds, the list is never-ending. And certainly, these ingredients contribute to the flavor of the exterior of the meat. After all, what would a dish like beef galbi be without the charred, smoky, sweet-savory flavor that results from the combination of asian pear, garlic, and various aromatics hitting a hot grill?

But do these seasonings truly penetrate beyond the surface? Just to be thorough, I performed some basic tests.

Below are six samples of chicken breast, each treated with a different seasoning in a 10-percent salt brine: sugar, MSG, grated garlic*, pepper, cumin, and five-spice seasoning. I marinated each sample for 8 hours and then cooked the chicken sous vide in a 150°F water bath for one hour. For comparison’s sake, I also repeated the test without salt (0-percent brine).  

I evaluated each sample for flavor penetration by cutting off the outermost 2 millimeters of meat on all sides, compared against a control sample of “unflavored” (salt brine–only) chicken, as well as a completely unseasoned sample.

General Observations

• For pepper and cumin, there was no detectable flavor penetration; I couldn’t taste any spice at the interior.
• Garlic and five-spice seasoning showed the faintest hint of seasoning in the interior, but it was almost imperceptible compared to the unseasoned control sample.
• The flavor of sugar-treated chicken was mostly salty at the interior; there was little to no detectable sweetness.
• The MSG sample showed the greatest transformation: very umami, with a ham-like flavor and texture.
  

I selected these seasonings based on a couple premises: A) Molecular weight correlates loosely with degree of permeability through meat since smaller molecules can generally pass through that semipermeable membrane more easily, and B) molecules that dissociate in water into ions can permeate meat tissue to an extent.

Sugar is a huge molecule (342.3 g/mol, compared to salt’s 58.44 g/mol) that doesn’t dissociate into ions in water. It’s far too big to penetrate meat tissue—which we observe in testing. Similarly, piperine, the compound responsible for the pungency of black pepper, is another large molecule (285.35 g/mol) with no magnetic charge—and we don’t taste it in the interior either. Cuminaldehyde, the aromatic oil responsible for cumin’s flavor, is also pretty large (148.21 g/mol), so it should not season meat deeply.

The results for garlic and five-spice seasoning were unexpected, though. Both garlic's allicin (162.28 g/mol) and five-spice's eugenol (164.2 g/mol; one of the molecules responsible for the flavor of clove and cinnamon) are relatively large molecules compared to salt. We wouldn’t expect much flavor penetration based on our initial premise, but I did detect the faintest hint. It could be that these molecules are slightly more polar (charged) than, say, cuminaldehyde or piperine, so they may be able to reasonably pass through that semipermeable membrane. But that’s just an educated guess at best.

Finally, the MSG sample gave the most surprising result. MSG has molecular weight (169.11 g/mol) similar to allicin or eugenol, but it readily dissociates in water into sodium and glutamate ions. The charged nature of this molecule probably makes it easier to pass through meat tissue, and we may have observed this in testing: The MSG sample seemed almost like cured ham, with a distinct savory flavor. 

The Bottom Line

Beyond the surface of meat, it seems like for the most part, they do not. If you truly want your seasonings to penetrate to the interior of your meat, you might choose ingredients with flavor molecules that are smaller, and preferably ones that can dissociate in water into smaller, charged ions. Or you might consider manipulating the meat itself: Cutting it smaller for increased surface area, injecting a marinade into it, or pounding or roughly massaging it to break up muscle tissue might help a marinade penetrate more deeply.

Question 3: Does Fat Improve Flavor Inside the Meat? (Answer: Not Really, But You Should Still Use It)

You’ve probably heard the cook’s adage: Fat carries flavor. After all, how many recipes have you read that tell you to toast or “bloom” your spices in oil? Many flavor molecules are relatively nonpolar, meaning they don’t readily dissolve in water, but they do dissolve in fat or oil, which acts as a nonpolar solvent. So cooking your spices and aromatics in oil does tend to intensify their flavors. But the question remains: Can fat deliver those flavors deeper into meat?

I set up four samples of chicken breast using four different flavorings, and stirred each flavoring with a measured amount of vegetable oil. (None of these samples included salt or any other ingredients.) I marinated each sample for 8 hours and cooked them at 150°F for one hour. Concurrently, I repeated this test but briefly cooked the aromatics in oil by microwaving the mixtures for 2 minutes (until they were bubbly, slightly browned, and fragrant).

General Observations

• I didn’t detect flavor at the interior of any sample!

The Bottom Line

Fat doesn’t seem to “carry” flavor deeper into meat through marination. And if we think about this from a molecular perspective, this observation tracks. The permeability of meat to certain molecules largely depends on both their size and magnetic charge. Fats are large nonpolar molecules, and they lack charge, so they shouldn’t pass through meat very easily (if at all).

So why do so many cooks use oil in marinades? Despite their inability to transfer flavor into the meat, fats still deliver plenty of flavor to the surface. They also play double duty to conduct heat and lubricate food to keep it from sticking on a hot surface. But as far as adding flavor that you can detect through to the center of your meat? Don’t count on it. 

Question 4: Do Acids, Bases, or Enzymes Make a Difference in Texture or Quality? (Answer: Yes)

It’s common practice to add acids like lemon juice, vinegar, or buttermilk to marinades. These ingredients lower the pH of the mixture, which helps to denature proteins by changing their shape. In the best case, this denaturation can tenderize meat. Acids can also increase the water-holding capacity of meat. As Serious Eats contributor Nik Sharma explains in his exploration of the effects of different acids on meat texture, changing the shape of proteins exposes certain amino acids, which provides new opportunities to bind water. 

But acids are just one player in a wider field of additives that can alter the texture and juiciness of meat. For example, there’s plenty of evidence to support the notion that raising the pH of a marinade (with say, baking soda or baking powder) also improves water-holding capacity. Why? High pH makes it harder for intramuscular proteins to associate and bond tightly when cooked; water gets trapped in the spaces between proteins, so the meat holds on to more water and stays juicy. Even Kenji stumbled upon this trick to keep shrimp plump and juicy. Finally, baking soda is a common addition to marinades in Chinese cooking—an essential step for velveting.

Apart from pH, we can also harness the power of enzymes—specifically proteases, such as those found in pineapples, to tenderize meat. Instead of denaturing (unfolding) proteins in the way that acids do, proteases cut proteins (like collagen) into smaller building blocks—the constituent amino acids. That means that proteins treated with protease tend to be very tender, almost falling apart in texture. Among proteases, bromelain (from pineapple), papain (from papaya), and ficin (from the fig tree) are some of the most common enzymes used to tenderize meat in industrial food preparations.

To illustrate and compare the differences between these treatments, I set up a basic test: 3 samples of chicken marinated for 8 hours each using a different “marinade”: a solution of 10-percent baking soda, a solution of 10-percent lactic acid, and pure pineapple juice (grated and strained from the core of a fresh pineapple*). I cooked each sample for one hour at 150°F in a sous-vide bath. I weighed each sample before marination, after marination, and after cooking to track any water loss. I also repeated this test with salt in each sample, and kept a control sample of plain, 10-percent brined chicken for comparison.

*Canned pineapple fruit or juice does not contain any active bromelain. The easiest way to obtain bromelain is to juice a fresh pineapple, or grate the flesh.

Here are the samples after 8 hours of marination:

The baking soda sample looks relatively raw in comparison; the lactic acid sample looks opaque, almost cooked at the exterior; the pineapple sample is slightly cooked but with visible striations in the meat that weren’t apparent at the start.

Here are the same samples after cooking:

General Observations

• All samples were relatively tender compared to the untreated, 10-percent–brined chicken.
• Lactic acid yielded the least tender meat, with a slightly “squeaky” texture between the teeth; the meat lost roughly 22 percent in water weight.
• Pineapple gave the most tender, fall-apart texture; but the exterior was mushy, pasty, and categorically unappetizing. Total weight lost was 32 percent after cooking.
• Baking soda resulted in the juiciest meat by far. The texture was slightly less tender than pineapple. Total weight lost was 5 percent.

Overall, all three methods showed a tenderizing effect. The most dramatic effect came from pineapple juice (bromelain), but it came at the cost of a nearly inedible exterior. This mushy, pasty quality is probably why most cooks recommend marinating in pineapple juice for shorter time periods—30 minutes to 4 hours at most.

The pineapple sample also showed the most water loss despite its fall-apart texture. 

Baking soda produced the most striking result at the interior. Check this out:

I didn’t poke those holes. Those gaps are likely evidence of proteins failing to bond and contract due to the elevated pH. Instead, water became trapped in these spaces, and I could see that water pressing out from these gaps as I sliced through the sample. But despite baking soda’s effectiveness, there was a drawback: Using such a high concentration of baking soda gave the chicken a metallic, ammonia-like aroma.

The Bottom Line:

Acids, bases, and enzymes all work to tenderize or retain moisture in meat.

• Enzymes give a more fall-apart, broken-down interior, but don’t help meat retain ‘juiciness’;
• acids have a mild tenderizing effect and help to retain water; 
• and bases seem to produce the juiciest, most plump interior.

The big caveat? Mind your concentrations of these additives as well as timing, since they can quickly transform the meat from palatable to mushy (bromelain), metallic tasting (baking soda), or inedible. Finally, don’t mix acids and bases in a marinade! They won’t work because they neutralize each other, so pick one or the other.

Conclusion: Is Marinating Worth It?

After all this testing and research, we can (kinda, sorta) answer the question: Is marinating really worth your time? Well, yes, somewhat. But not for the reasons you may have thought. If you take away one idea from this article, it’s this: Marination is mostly a brine and otherwise a surface treatment. The benefits are maximized through cooking—over high heat, over a grill, in a hot oven. That cascade of flavors resulting from caramelization of sugars, and the heating of aromatics, spices, and fats all occur at the surface and maybe even the first millimeter of meat, though to be fair, those are all benefits that would also occur when a marinade is applied right before cooking. 

Marination is mostly not a method for injecting flavor into the interior of proteins. Beyond salt, and a select few ingredients like MSG, there are few ways to season the interior without resorting to physically manipulating the meat so that the marinade can penetrate, such as injecting flavorings with a syringe. And apart from flavor, if you really want to transform the interior texture of meats, consider adding an acid, base, or enzyme to your marinade.

There are still plenty of questions to ask here: Does marination work better for certain proteins, or certain thicknesses of meat? And how does marination affect vegetables? But for most marination scenarios, this guide is a good starting point, one that should give you enough information to help you navigate the ingredients and timing when marinating meats.