While in the last episode of “Ingredients Under the Microscope” we explored the chemistry of osmosis and the importance of water balance ($A_w$), today we enter the laboratory to face the challenge most feared by great leavenists: the Mechanics of Incorporation.
Because, while it is true that candied fruit guarantees humidity and aroma over time, it is equally true that, the moment it enters the mixer, it represents the number one danger to the structure of our Panettone. Let’s see why.
The Geometric Enemy: The “Sharp Edge” Theory
Imagine the gluten network formed after hours of processing as an elastic net, taut and perfect, ready to retain the gases of fermentation. Now, imagine throwing hundreds of small solid cubes into this net.
From a rheological point of view (the science that studies the deformation of matter), the candied fruit cube is a rigid foreign body within a visco-elastic mass.
The problem lies in its geometry: the edges.
If the candied fruit is of low quality (hard) or, worse yet, too cold, its corners act like micro-blades. During the rotation of the machine, these sharp edges “cut” the protein filaments of the gluten you have laboriously built, causing the structure to collapse (the dreaded “network breakage”).
The Hidden Variable: Temperature
Here is where the professional technique that distinguishes an amateur from a master comes into play. Many think the difficulty lies only in the quantity of fruit (the so-called “suspensions” or heavy inclusions), but the true critical variable is the temperature of the candied fruit.
The sugar saturating the fruit reacts to the cold by crystallizing or hardening. A candied fruit taken directly from the fridge or a cold warehouse is a hard projectile. Inserting it into the warm dough (which usually travels at 26-28°C) creates a devastating thermal and mechanical shock.
The Technical Solution: “Tempering” the Suspensions
How do we save our gluten network? With preparation.
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Thermal Softening: Candied fruits must never be inserted cold. Professionals heat them slightly (often in a bain-marie or proofing chamber) to bring them to a temperature close to that of the dough or slightly higher (approx. 30°C / 86°F). The heat softens the sugars and makes the cube “plastic”, eliminating the rigidity of the edges.
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Lubrication: Often, a portion of the butter from the recipe is added precisely at this stage. The fat coats the fruit, creating a slippery film that allows it to “enter” the gluten network without tearing it, but rather sliding between the meshes of the net.
Therefore, creating a large leavened product is an act of balance between opposing forces. We have seen how Chemistry prepares the fruit and how Mechanical Physics determines its structural success. But be careful: adding candied fruit also means adding “hidden” sugars that can block fermentation.
Spoiler: we’ll talk about this in my next publication.
With Passion and Precision,
Katia Oldani Biologist Pastry Chef
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