Some traditions are worth preserving. The slow fermentation of yeast to make bread, the methodical layering of butter and dough for a croissant, and the painstaking reduction of goat's milk over the course of an afternoon to prepare cajeta—a more complex and delicious form of Mexico's famed dulce de leche.
Such time-honored rituals require dedication and lots of patience...wait a minute, scratch that! While I appreciate old-timey techniques as much as the next girl, there's no reason anyone should be sweatin' it out for three hours at the stove. Well, not when it comes to cajeta, anyway. I'm talking 60 minutes, tops.
Just like dulce de leche, cajeta is a thick, sweet confection made from boiled milk—goat's milk in the case of cajeta, and cow's milk in the case of dulce. And, just like its cousin, cajeta is almost universally described as "Mexican caramel." On the surface, that makes sense. They're both gooey and brown, with a similar sort of nuttiness. But it's also a gross oversimplification that erases the unique attributes of Latin America's dairy-centric confections, which aren't caramels at all.
Quick crash course: Caramel is a by-product of thermal decomposition in sucrose, a lovely sort of decay that produces a wide range of carbon compounds with flavors that run the gamut from toasty to burned. Pure caramel is brittle and lean, as in the crispy top of a crème brûlée, but it can also be diluted and enriched by cream.
The traditional point of caramelization is rather high, as sugar itself is dang stable at temperatures below 340°F. That's how pastry peeps create so many boiled-sugar candies that aren't caramel-colored or caramel-flavored at all: fondant (cooked to about 240°F), marshmallows (250°F), nougat (260°F), saltwater taffy (270°F), or even crystal-clear candy "glass" (300°F) and snow-white cotton candy (320°F).
Compared to these non-caramel sugar candies, dulce de leche and cajeta are cooked at even lower temperatures, with milk and sugar simmered at 212°F for the bulk of the process and climbing toward 220°F near the end. Relatively low heat ensures a mellow sweetness, free from the bitter edge of burned sugar. So where does all that toasty/malty/nutty color, flavor, and aroma come from? The Maillard reaction, in particular the browning of lactose (a disaccharide) and lysine (an amino acid); more on that in a bit.
The final defining feature that separates dulce and cajeta from caramel is the inclusion of baking soda (an alkali).
Elevating the milk's pH in the early stages of cooking may hasten the Maillard browning of lactose and lysine, but it has no impact on caramelization. To put that theory to the test, I combined 3/4 cup sugar and 3/4 teaspoon baking soda with a quart of water, then boiled it for an hour to see how alkalinity might affect caramelization over time. The result was a syrup that behaved no differently from one made without soda. In both cases, caramelization didn't occur until the syrup had reached a concentration of 99% and surpassed a boiling point of 340°F. The only difference? The alkalized caramel tasted like soap.
Baking soda doesn't create a soapy flavor in dulce de leche or cajeta because milk itself is slightly acidic, growing more so with prolonged exposure to heat. It's a beautifully balanced equation that allows baking soda to assist with Maillard browning early on, then slowly burn off in the plummeting pH of boiling milk.
Given how often I've mentioned both dulce de leche and cajeta, it's tempting to imagine they're one and the same, reducing their differences to a matter of milk type. Hooo boy, would that be a mistake! Broadly speaking, cow's milk and goat's milk may both contain sugar, fat, protein, and cholesterol, but their exact composition within each category is distinct.
Most famously, goat's milk is comparatively low in the sugar lactose. That makes goat's milk easier to digest for those with lactose intolerance, and less likely to burn. Goat's milk also contains a higher concentration of amino acids, with twice as much lysine and serine, in addition to more alanine, leucine, methionine, threonine, proline, phenylalanine, tyrosine, and valine, too.
Now, before your eyes glaze over, here's the deal: Those are the specific amino acids scientists credit with producing flavor and aroma in Maillard browning, creating notes of caramel (lysine), almond (phenylalanine), persimmon (alanine), fried potatoes (methionine), fresh dates (serine), and rose (tyrosine). Cow's milk has these amino acids, too, but at lower levels, so the specific composition of dulce de leche tends toward glycine (sweet), aspartic acid (fruity), glutamic acid (sour), and tryptophan (not assigned any flavor).
On top of that, goat's milk has five times more cysteine, an amino acid associated with thermal stability and our perception of umami. So, compared to cow's milk, goat's milk is less likely to scorch or curdle, while doubling down on flavor and aroma and quintupling our sense of richness. In short, cajeta is everything you love about dulce de leche, but more delicious and easier to prepare.
Thanks to its unique makeup (low lactose, high cysteine), there's no need to babysit goat's milk for hours over a low flame or stir continually to ensure that it won't scorch—you can toss in a vanilla bean, crank up the heat, give it a few lazy stirs, and have cajeta within 45 minutes of it coming to a boil. (Although, to be totally honest, you do need to stir it a bit more consistently toward the end of cooking, when its thickened texture puts it at greater risk of burning.)
Added to that, most commercial goat's milk is ultra-pasteurized, a process that incidentally makes dairy more resistant to curdling—turning a problem for homemade ricotta into an asset for cajeta.
Unlike caramel, cajeta isn't cooked to a specific temperature, but rather a specific consistency, al punto de cajeta. That translates as "at the point of cajeta" and indicates a mixture so thick, you can easily scrape it aside to see the bottom of the pot.
That can be a frustratingly vague doneness cue for more precision-obsessed cooks, but the truth is, a thermometer won't work here. Because cajeta needs a big pot to prevent overflow as it foams early on, by the time it reduces down to the desired consistency, it's not deep enough to submerge the probe of a thermometer (digital or analog) without touching the bottom of the pot. Even if you transferred the mixture to a smaller container, you'd struggle to get an accurate reading on a thermometer while trying to awkwardly scrape and stir the ever-thickening cajeta around it.
Fortunately, judging cajeta isn't a matter of science so much as taste—it's done when you say it is!
For a thin and saucy cajeta, stop cooking as soon as it's thick enough to momentarily leave a clear trail in the wake of a spatula pulled across the bottom of the pot. For a lusciously thick cajeta, keep going until the "trail" stays open for a full second ("one one-thousand..."). For a spreadable, peanut butter–like paste, the trail should last two full seconds. By three, the cajeta will cool into something akin to fudge.
I'm fond of the "one second" rule, which makes a cajeta that's like a thick sauce while warm, then soft and stretchy once cool (like the center of a Rolo). It's thick enough to drizzle over ice cream or whip into your favorite frosting, but gooey enough for dipping apple slices or just licking straight off a spoon.
And, since it's relatively quick to whip up, you really should do all of the above without hesitation. Your next batch is less than an hour away.