How to not make my macarons rip?

Question

I just made a batch of macarons. This is my third total batch of them, and they become increasingly better - alas compared to my previous batch, these don't show much if any improvement even though I've changed how much I mix the macaron mass and how I pipe them.

Recipe:

~150g egg-whites
~70g finest sugar (not powdered!)
Mix with an older Kenwood chef until stiff and glossy
1 very flat teaspoon of vanilla extract (so about half a deep spoon)
~3g of powdered green food coloring
More mixing with the Kenwood until well mixed, still stiff and glossy

~150g sifted almond meal
~250g sifted powdered sugar
pinch of salt
Mix well

Mix the almond/sugar stuff into the egg-whites using a rubber spatula until the consistence allows me to pour a figure-eight without globs breaking off

Pipe onto trays, let sit some 10-15min and rap every ~5min (rap 4 times, turning tray 90 deg after a few hits/raps)

Bake for 20min, middle height of oven¹, at 150C

The first tray went into the oven as soon as the latter hit 150C:

The second tray had to wait for some ~20min while the other baked, during that time I rapped it a few times more but mostly let it sit:

What can I do to prevent my macarons cracking / how to change my recipe and/or process?

I see that there are positive results by letting them sit for more time, so I'm thinking about letting them sit ~1 hour next time I make a batch, and def rap them every 15min or so. What other changes/improvements should I make to my recipe?

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_{¹what's that called in english? I call it "Mittlere Backofenrille" in German}

Answer 1

While there is no standard, products marketed as Almond Meal typically have larger grains than products marketed as Almond Flour. I am not sure if this could be the cause of your problem, but I would recommend trying an Almond Flour, or grinding your Almond Meal in a food processor.

Also, I notice that while your second batch is much less cracked, it still is not well risen. I believe your problem may be oven temperature and heat circulation, and you can confirm this by watching your macarons in the oven. I don't know a silver bullet solution, but I am putting some more analysis below, which I hope is still helpful.

For comparison, a well risen macaron has a "belt":

This belt is essentially a crack of its own, and the difference between belted macarons and yours would be the stage of cooking when the crack forms.

In either case, the shape of your macarons is controlled by the release of moisture as steam.

First, the heat of the oven will crisp the outside shell of the macaron. As it cooks from the outside in, moisture in the batter will start to evaporate. The meringue traps air in little pockets, and the steam expands in these pockets, ideally so that the shell will nicely and uniformly rise until a belt opens up to release the steam. A similar process happens when baking bread, and this is why bread bakers will cut slits on top of their loaves.

When bringing the macarons back down to room temperature, the steam contracts again. Typically, cracks on the top of macarons (also choux pastries) occur when temperature changes too quickly. The pressure inside will suck in the outer shell and cause it to collapse.

Is it possible that you took your first batch directly out of the oven (possibly into chilly air)?

I believe that rapping the baking sheet helps break any especially large air pockets, to help keep the rise uniform. But you would want to do this as little as possible, to avoid deflating the smaller air pockets in the merengue.

Based on my understanding, I have the following recommendations:

Watch your macarons while baking. Does the belt form midway through baking, or never at all?

• If the belt forms, but collapses later, and before you actually open the oven, then your oven may be circulating heat badly. This is unlikely, and it would only happen if your merengues somehow cool off while they're still in the oven.

• If it forms, but collapses when you take your macarons out of the oven, try instead simply opening the oven door and turning the oven off. Leave the merengues on the middle rack. The air inside the oven will mix with outside air and cool down more gradually. You can also try baking your macarons longer, in case your [oven + bake time] happens to be leaving them underbaked, but I don't think this is happening.

• If the belt never forms, your merengue is probably deflated. Try leaving them sitting for 10 minutes, and only rapping them once. Also try whipping stiffer peaks.

Lastly, I have an extra comment for the second bullet point – I noticed that the crusts of your merengue are a light brown, while the insides are a light green. Your outside is browning and your merengues are possibly overbaked. Try either reducing the bake time by a few minutes, or putting aluminum foil over the merengues to stop the browning of the outsides.

If you do the aluminum foil trick, be extremely careful to place your foil in the oven very quickly. Before they're finished baking, the macarons are especially sensitive to temperature drops, so you can't let in too much cold outside air.