The Science of Wet Brining Poultry
How to Wet Brine Turkey using Dairy
Hi Friends,
Some conversations come up every year without fail, and one of those centers around brining that pops up right around Thanksgiving. I don’t want to spend my time arguing on whether dry or wet brines are better; that is not an issue I feel very strongly about. I want to briefly discuss why brining is beneficial to turkey and, more specifically, why fermented dairy brines are very good at achieving juiciness and a tender roasted bird. My preferred method is to brine the bird in kefir or buttermilk (you can use them interchangeably in most recipes with great success) with a few spices before I roast it in the oven.
The use of fermented dairies like yogurt and buttermilk to make meat juicer and more tender is not new, it’s been a part of many cultures from Iran to India since ancient times, and that’s the part I often find fascinating in cooking. Many ancient cooking techniques are deeply rooted in science, and people back then didn’t have the same access to technologies as we do. Yet, they achieved processes that produced remarkable results that we still practice today.
To understand how brining with fermented dairies like kefir and buttermilk works, it's essential to know what we are trying to achieve and why. Let's start with juiciness. While this essay focusses on turkey, it also applies to other types of poultry like chicken and squab.
What is Juiciness and Water Holding Capacity in Meat?
One hallmark of meat that’s cooked well is juiciness. Imagine slicing through a dry turkey breast; it’s going to be very disappointing. The juiciness in meat comes from water and from fat (that renders during cooking). Turkey is a lean meat, and it has less fat than chicken, so to make it tastier, the juiciness needs to be increased. Juiciness also goes by another name, Water Holding Capacity (WHC). In meat, 5% of the water present is bound to amino acids on the proteins, while the remaining 95% of water is contained by physical forces such as capillary force in the filaments. The greater the quantity of water bound to the meat, the juicier the meat.
How can Juiciness be improved?
To improve the juiciness of the meat, we need to not only add more water but also make sure it binds well. During cooking, the meat will lose some water due to the shrinkage and change in the structure of the meat (the proteins will denature on heating and lose water). This is where brines and marinades come into play; they help improve water retention, improve flavor and texture.
What is Brining and Marinating? How are they different?
Brining is simply a way to make cooked meat juicier, flavorful, and tender by incubating the meat in a high salt solution. Marination is essentially the same thing but with less salt. Both brines and marinades besides salt can contain cooking acids like lactic acid and/or citric acid; aromatic ingredients like garlic, onions, herbs, spices; tenderizers can be added to either as long as they remain functional (some enzyme-based tenderizers won’t work as well if there’s too much salt in the brine). From a general perspective, marination is a type of brining.
Brines and marinades do not need to be wet; they can be “dry.” There’s still water involved (these reactions still need water to occur), so technically, they’re not really dry, but rather what the dry here refers to is the lack of added water or a liquid like kefir or buttermilk. Some people prefer wet brines and some dry ones. People who like dry brines say the flavor is much more concentrated on the skin, the skin is crispier, and it’s also easier to handle. I’m wading into turbulent waters here. The more important thing is that you should brine your turkey. We're wet brining the turkey in this recipe.
How does the kefir/buttermilk brine work?
pH
In general, the lower the pH, the higher the WHC (meat doesn’t hold water as well at a pH of 5.0 or above); the meat will be juicier.
The use of cooking acids like lactic acid (fermented dairy like kefir, buttermilk, yogurt), citric acid (lemons and other citrus fruits), and acetic acid (vinegar) when included in brines help lower the pH. Of these three common cooking acids, lactic acid is the best. I once ran a series of experiments for Serious Eats to understand why yogurt marinades are so good at maintaining juiciness. It turns out that the lactic acid present in yogurt (and in other fermented dairy products) is much gentler on meat proteins and great at increasing the juiciness of the meat.
Animals synthesize lactic acid and citric acid, while acetic acid is synthesized by bacteria and yeast. Consequently, animal cells have evolved to deal with lactic acid and citric acid but not acetic acid. Lactic is gentle on meat texture and does a really great job at improving water binding and holding. Acetic acid/vinegar is extremely harsh on the proteins in meat, so it’s not a good idea to brine or marinate meat for too long (I usually do an hour or less) as the meat texture looks crumbly on the surface after cooking. Citric acid is synthesized in the cell's mitochondria and rarely comes out of the cell, and when it does, the cells immediately do their best to remove it. Citric acid is somewhere in between lactic acid and acetic acid in its efficiency in brines.
In short, BEST Lactic Acid>Citric Acid>Acetic Acid WORST - fermented dairy marinades are the best.
Ok, so what does pH actually do? The low acidic pH from the acids helps change the electric charges on the proteins in the meat and this, in turn, helps the protein bind more water, and the meat starts to swell up.
Can you use the quick hack of making kefir or buttermilk with vinegar or lemon juice and milk?
My recommendation is don’t; this is a better hack for pancakes (I know some bakers who say this hack doesn't work as well with baking because they've noticed differences in the crumb textures of cakes). There are no lactic acid bacteria involved in this hack and no lactic acid. The bird might smell of vinegar, and that won’t be very pleasant. When vinegar or lemon juice is mixed with milk, the milk proteins curdle. While this mixture will contain phosphates, it won’t contain lactic acid but vinegar and citric acid. When it comes to meat, vinegar or acetic acid is one of the harshest cooking acids, with citric acid right behind it. Leaving the meat in a brine with acetic acid or citric acid for an extended period will take its toll.
Last year Samin Nosrat shared her recipe for buttermilk brined turkey and we discussed the use of kefir as a substitute for buttermilk.
How does Salt Help?
Salt (sodium chloride) does a few things.
A huge reason why salt works so well at increasing the water-holding capacity in meat is its ability to change the electric charges on the proteins in meat. Salt is ionic, i.e., when dissolved in water/brine, it splits into positively charged sodium ions and negatively charged chloride ions. The amino acids present in the turkey proteins also contain electric charges (both positive hydrogen ions and negative carboxylate ions). What happens next is very interesting. The amino acids love to bind the chloride ions from the salt, and in turn, the amino acids release their hydrogen ions into the brine. This lowers the pH and further increases the amount of water that the meat can hold.
Salt helps solubilize some of the proteins in the turkey muscle, weakening some of the structural proteins that make the meat more tender.
The high salt concentration in the brine prevents the growth of harmful microbes.
Salt also provides saltiness and gets into the meat through osmosis. At the start the salt content inside the meat is less than the salt present in the brine. To achieve equilibrium, the salt will start to move inside the meat over time. It won’t go all the way into the deepest part, but it gets through enough to flavor the meat well. This is why longer brining periods work better than shorter ones.
Dairy Phosphates
If you read the ingredients listed on the back of pre-brined meats like a pork tenderloin sold at the grocery store, you might notice in addition to lactic acid/lactate, the word “phosphates” is mentioned. Phosphates are an important player in water retention and are very popular in commercial meat brines. Dairy and fermented dairy contains are rich in phosphates (milk contains several phosphoproteins - proteins rich in phosphates), unlike plant-based milk. When using kefir, buttermilk, or yogurt, those phosphates come into play. Phosphates are also a type of salt and work similarly to table salt (sodium chloride); they’re just much better at water retention in meat. Hence, meat brined in dairy and fermented dairy is very juicy.
Tenderness
So far, I've focussed on water retention using the low pH of lactic acid and the effect of salt and phosphates. I've also mentioned how salt dissolves some muscle proteins and makes the overall texture of the meat better. Another component here that can improve texture and the source for this is the enzymes in the fermented dairy that come from the bacteria. Some of these enzymes called proteolytic enzymes can break down the proteins in the meat, making the meat more tender.
In conclusion, brining in fermented dairy like kefir or buttermilk makes us a tastier turkey by acting on the proteins in meat and making them hold water more efficiently and also by changing the structure of the meat proteins so the turkey textures transforms into something wonderful.
Hopefully, after reading this, I've convinced you of the importance of brining.
Further Recommended Reading:
Food Chemistry by H.-D. Belitz, W. Grosch, P.Schieberle
Lawrie's Meat Science by R.A. Lawrie and D.A. Ledward
Serious Eats - The Science of Yogurt Marinades (by me)
Serious Eats Crisp-Skinned Spatchcocked (Butterflied) Roast Turkey With Gravy Recipe by Kenji-López Alt
Make the Golden Garlic Roast Turkey to see these scientific principles in action.
I always make the sides and dessert but am going to pass this on to my SIL who makes a killer bird already!