The Maillard Reaction: The Chemistry Behind Cooking

I know my typical post on here involves recipes, but this is Kitchen Chemistry, and I am a chemist, so you have to expect that some chemistry will slip in here every once in a while. It just so happens that this year is the 100th anniversary of the Maillard reaction (pronounced May-yard), discovered by the eponymous and well-mustachioed Louis-Camille Maillard. You probably have no idea what the Maillard reaction is, but you most certainly know its application: it's the chemistry behind the browning of food when cooked.

When you subject food to high temperatures in a relatively low-moisture environment (a.k.a. sauteing, grilling, baking, but not boiling or microwaving), it browns. What's happening is that the sugars in the food are reacting with the amino acids that are also in the food, resulting in a number of new compounds. The specific compounds will vary among different kinds of food, but generally they're responsible for the pleasant taste and texture of cooked food.

Now, wait a minute, you might ask: table sugar can brown to make caramel, but there's no amino acids around there (OK, maybe you're not asking that, but I'll answer anyway). This is the result of another non-enzymatic browning reaction: carmelization. In this case, the sugars are reacting with other sugars, producing rearranged compounds, fragmenting and polymerization, all of which change and enhance the flavor of the food.

Of course, it's not really that simple (if you've taken chemistry, you should know that it's never that simple - otherwise people like me wouldn't have a job!). Since most foods have both sugars and amino acids, often a combination of these two reactions occurs when they're cooked. Also, even if you assume that only one of the Maillard reaction or carmelization are at work, still as many as hundreds of new compounds can be made. Despite discovering the reaction, Maillard never really understood it. It was about 40 years later that an American chemist, John E. Hodge, delved deeply and worked out the various processes at work. Impressively, he did the work himself. In case you weren't yet convinced of the complexity of the reaction, here's a schematic from his paper in Journal of Agricultural and Food Chemistry:

Basically, there are three stages to the reaction:

• The sugar and amino acid combine to form a glycosylamine.
• The glycosylamine, which is unstable, undergoes an Amadori rearrangement - atoms get moved around, and what was a cyclic compound gets opened up into a linear chain.
• This intermediate (which is also an intermediate of glycation in the body; that's right, your body does the Maillard reaction too - except in the body it's not good) reacts in different ways, branching out to form a wide array of nitrogen-containing products, both small molecules and polymers.

Is this really a big deal? Well, turns out, it is, for a couple of reasons. The discovery was the first to really explore the chemical basis behind the flavors and smells in food, and led to the establishment of food science. Also, while a large number of the compounds produced upon cooking are pleasant and desirable, some of them, particularly in processed foods, can be dangerous. It's been a long goal of food chemists to find ways to process food in ways that minimize the harmful compounds while enhancing the pleasant ones, such as enzymatic pre-processing to break down the amino acid asparagine, which forms some amount of acrylamide (a carcinogen) in the Maillard reaction when it is present in food. It must also be a big deal, because a group of chemists recently convened in France near Maillard's hometown for a conference celebrating the 100th anniversary of the discovery, complete with a large tower of profiteroles.

Still not convinced? At the conference, Nobel Laureate Jean-Marie Lehn contended, “The Maillard is, by far, the most widely practiced chemical reaction in the world.” That's because people like you are running this reaction every time you cook. See? You are a chemist after all. :)

Apple, Gouda, and Walnut Salad with Cider Vinaigrette

If you're me, then when fall comes, you can't get enough of apples. That means that when it comes time for lunch, you want to throw together a salad that involves apples. And you want to make it as full of apples as you can, so of course you make that cider vinaigrette recipe that you've had bookmarked for about a year. Luckily, this will not be challenging, and in about ten minutes you'll have a fresh and delicious salad, and you will be satisfied. I made this for myself, but I've scaled the recipe to throw together for four.

Ingredients

8-10 cups leafy greens (I used a salad mix from the market; pick your favorite)

2 medium apples, cored and roughly chopped

1/2 cup walnuts

4 oz gouda cheese, shaved (or gorgonzola cheese)

Cider Vinaigrette:

taken from NPR's Kitchen Window

1 cup apple cider, boiled down to 1/2 cup*

2 Tbsp cider vinegar

1 tsp maple syrup

1 shallot, finely minced (or 1/8 tsp garlic powder + 1/8 tsp onion powder)

1/2 tsp salt

black pepper, to taste

1/4 cup extra virgin olive oil

Directions:

1. Blend dressing ingredients together (or shake vigorously in a sealed jar). Store in a sealed container in the fridge for up to a week.

2. Toss together salad ingredients, and drizzle with dressing. Serve immediately.

Serves 4-6

*OK, full disclosure - I used 1/2 cup apple cider as is, which tasted just fine. It made for a thin vinaigrette, though, and I like mine a bit thicker.

Cinnamon Apple Syrup; Or, Upcycling Apple Peels

I've mentioned how much I love apples, and how much my day was made when I brought home 4 pecks of apples (McIntosh, Jonathon, Golden Delicious and Braeburn). Recently, two of those pecks went into a giant pot to be cooked down into a delicious applesauce, which was processed and resulted in 5 quarts of homemade applesauce taking their proud place in my pantry. More recently, another peck became some heavenly apple butter. The by-product of this process, of course, was a rather large pile of apple peels. In the spirit of not letting such a useful by-product go to waste (perhaps the apple version of "everything but the squeal"), I cobbled together a recipe to make use of the perfectly good peels. This tasty and apple-y syrup can be used on top of waffles, pancakes, ice cream, baked apples, or whatever you might like to eat with syrup. I had apple cider around, so added that in to give even more apple flavor, but it's not necessary. Also, although I was going through a rather large quantity of peels, this recipe can be scaled down easily if you didn't go apple crazy. You can add the cores to the steeping step too; just make sure to cut off the stems and the bottom end. If a sweet syrup isn't your thing, there are other ways you can use peels, like this, or this.

Note on the apple peels: if you're buying non-organic apples from the grocery store, make sure that you wash them thoroughly if you wish to use the peels. They're covered with pesticides and wax, which you probably don't want to eat. Mine were directly from an orchard that uses minimal pesticides, so a quick soak in vinegar and water was sufficient.)

Ingredients

4 quarts (16 cups) apple peels

6 cups brown sugar

2 quarts (8 cups) water

4 cups apple cider (or more water)

2 Tbsp ground cinnamon or 2 sticks

1 tsp ground nutmeg

1/4 cup lemon juice (if canning)

Directions

1. Combine apple peels, water, cider, sugar, cinnamon, and nutmeg in a 6 quart slow cooker. Turn cooker on high, and allow mixture to steep for 3-4 hours.

2. Place a double thickness of cheesecloth in a colander, and place over a 6 quart stockpot. Pour (or scoop, if your slow cooker bowl is not removable) contents into colander, gently pressing to extract the liquid. Discard peels, or come up with yet another use for them!

3. Take strained liquid and bring to a boil, stirring occasionally. Turn heat down and allow to simmer, with stirring, until liquid is a thin syrup (reduced to about half the liquid volume). This may take 2 or more hours.

4. At this point, syrup can be poured directly into jars to refrigerate, or processed. In order to process, sterilize 4 pint glass jars by boiling in a large canning pot, and ladle some of the hot liquid into a small bowl with the lids to sterilize them as well.

5. Just before pouring syrup into jars, add lemon juice and stir well. Ladle into jars, leaving 1/2" headspace. Wipe rim clean and place lids on top, screwing bands finger tight.

6. Process jars in a boiling water bath for 10 minutes from the time a full boil is reached. After 10 minutes, turn off heat and allow jars to rest for 5 minutes in pot. Carefully remove from pot and place on a dry towel. Allow to cool, undisturbed, for 12-24 hours. After 2 hours or so, gently push down center of lids to make sure they've sealed (if they pop back, they haven't sealed).

Makes 4 pints

Vegan Apple Flaxseed Walnut Muffins

No, I'm not vegan. The great thing, though, is you don't have to be vegan to enjoy these muffins, and you don't have to feel guilty about indulging either. With whole grains, oil replaced with apple butter, and healthy fats and protein from the flax seeds and walnuts, there's a lot to like about these muffins. They're hearty, and yet light, with just the right amount of sweetness from a little maple syrup. Also, they're screaming with apple flavor (grated apples, diced apples, and apple butter), and anything that's made with apples is going to be good. If there's anything better than that, it's that the muffins come together quickly. Really, there's no downsides here.

Ingredients

2 cups spelt flour (or whole wheat flour)

1 Tbsp flax seed

1 tsp baking powder

1 tsp baking soda

1 tsp ground cinnamon

1/4 tsp ground allspice

pinch nutmeg

1/2 tsp salt

2 Tbsp ground flaxseed + 5 Tbsp water

1/3 cup maple syrup

1/4 cup apple butter (or applesauce)

3/4 cup coconut milk (or almond or soy, if you have on hand)*

1 cup peeled, grated tart apple (1 large or 2 small)

1 cup diced, unpeeled sweet apple (1 medium)

1/2 cup chopped, toasted walnuts

Directions

1. Combine flax seed and 5 Tbsp water in a small bowl; set aside for 10-15 min, or until a gel has formed.

2. Meanwhile, combine flour, whole flax seed, baking powder, baking soda, cinnamon, allspice, nutmeg, and salt in a medium mixing bowl.

3. In a separate bowl, combine flaxseed gel, maple syrup, apple butter, and grated apple.

4. Stir wet ingredients into dry, just until combined.

5. Gently fold in chopped apple and walnuts.

6. Spoon batter into a muffin pan lined with paper cups or lightly greased. Top muffins with extra chopped walnuts if desired.

7. Bake muffins in a 350 degrees F oven for 30 min, or until tops are golden .

8. Allow muffins to cool in pan for 10 min, then switch over to a wired cooling rack. Allow to cool completely, but also don't feel guilty about grabbing a still-warm muffin to stuff in your face. :)

*If you have unsweetened coconut lying around, don't go buying a can of coconut milk. It's really easy to make your own, and you can make exactly as much as you want. For the amount in this recipe, I put 1/2 cup coconut in a blender, then added 1 1/4 cup boiling water, and blended for 15-20 sec. Allow to sit for 5-10 min, then filter through a fine mesh colander to remove solids. I also let the solids dry out, so I can incorporate them when I make this.