Science: DIY Butter (and more!)

Cooking is science. It's actually a subset of materials science! Integral to cooking are the concepts of kinetics, phase transformations, and organic chemistry. Cooking is the perfect way to learn these intuitively.

Today, I'll explain a simple experiment I did in the kitchen.

The impetus was purchasing a half-gallon of heavy cream from Costco one month ago. The purpose was to make ice cream. In one batch, I didn't dilute the heavy whipping cream at all. I whipped it up with fruit in a blender and froze it. The result is a low-sugar/high-fat ice (heavy) cream. It's not very palatable...

I make yogurt with a traditional method. I suppose every Indian family in the world might prepare yogurt this way, maybe Persians and Greeks as well.

1. Pasteurize: heat milk (any kind) to boiling, killing off nearly all bacteria that grew since the industrial pasteurization process
2. Cool: let milk sit until it reaches a bathtub-appropriate temperature
3. Innoculate: whisk in active yogurt (maybe 1 tsp yogurt per gallon milk), seeding the milk with lactobacs (Lactobacillus cultures)
4. Incubate: store milk at room temperature until yogurt sets

The whole process takes maybe 6 hours. It's so simple and healthy; I don't understand why anyone would buy yogurt if they have the means to prepare this.

After my ice cream debacle, I thought about trying the yogurt-making process with heavy cream. What would result? I did a little reading and I discovered cultured butter.

Now that I'm done with the background, I'll explain the experiment with theory interspersed.

Cream has a higher fat content than milk, naturally formed from vertical phase separation in milk. In other words, the cream separates and rises to the top of the milk vat. Homogenized milk has some of that cream mixed in, and lactobacs turn homogenized milk into yogurt. Surely lactobacs can turn cream into a thicker, more acidic substance: creme fraiche. I vaguely recall this from a South Park episode, but this is basically thick, extra fatty yogurt that French people use in soups and sauces and desserts. Punjabi people use it too! Makes me wonder what food would be like if France colonized India instead...

1. Pasteurize: heat cream (any kind) to boiling, killing off nearly all bacteria that grew since the industrial pasteurization process
2. Cool: let cream sit until it reaches a bathtub-appropriate temperature
3. Innoculate: whisk in active yogurt (maybe 1 tbsp yogurt per gallon cream), seeding the milk with lactobacs (Lactobacillus cultures)
4. Incubate: store cream at room temperature until creme fraiche/crema sets

Creme fraiche/crema is great, but let's whip it and make butter. Churned, the small fat globules in cream smash together, merging to form large globs and eventually small masses of butter. Chemically identical to each other and distinct from the water, these masses attract and form a butterball. Any whipped cream will, eventually, form butter. Fermented cream, when whipped, forms cultured butter. The difference is lactobacs. Eating the milk sugars in cream, the lactobacs release lactic acid and other flavor compounds. Among these molecules, most of the water-soluble chemicals leave in the water: buttermilk! Thick, tangy buttermilk is a byproduct of lactic acid fermentation enjoyed in beverages, sauces, biscuits, and breadings. Great, and we get butter!

1. Chill: cool creme fraiche below room temperature (use ice bath)
2. Churn: blend until butterball precipitates
3. Separate: separate buttermilk from butterball
4. Extract: squeeze residual buttermilk from butterball (use ice bath)

Cultured butter is beyond great! Butter contains a decent amount of water, and thanks to lactobacs, this water is actually buttermilk in cultured butter. Use in baking, or mix in a little salt to complete this rich, complex butter. Or keep going! A compound butter is merely a solid solution with butter solvent. Mix in garlic, pepper, chives, onions, herbs, whatever you want, and freeze it so you have little butter bombs you can toss into a hot pan. Alternatively, one can melt the butter, kill all the lactobacs, and boil all the water out to make ghee. Ghee has a long shelf life and great temperature stability.

I skipped something important in processing: chilling. A beginner's mistake I made was blending crema at room temperature. The kinetic energy from the blending action heated the creme to steaming hot. Any butter that formed had melted; hence, I saw a yellow liquid. I chilled this liquid in an ice bath to thicken before mixing on a slower setting. The thick cream gently mixes, further thickening, until a phase transformation happens. Suddenly, instead of mixing a thick liquid, the blender mixes a loose solid. Using a blender instead of a traditional butter churner, I saw the transformation in real time. The next step involved squeezing buttermilk out of the butterball. Heat from my hands melted the surface of the butterball. I needed more ice to press the buttermilk from the butter. I left a lot of water in my first batch of homemade butter. A cheesecloth would make things easier.

There you have it! Starting with heavy cream and a little bit of yogurt, you can make crema, buttermilk, and cultured butter (and compound butter or ghee if you like). It's not vegan, but it really underscores the versatility of dairy. Remember that these innovations herald all the way back to simpler times, when pastoral nomads grazed their herds and flocks over the central Asian steppes. Early science and agriculture cemented dairy products in cuisines across the globe. Now we can enjoy them easily, and even perform some food alchemy of our own.

In a later post, I'll experiment with dairy alternatives to see what kind of fermentation I can get in a vegan mixture.