As the confectionery industry continues to evolve, manufacturers strive to push the boundaries of taste and texture within a single product. This pursuit has spurred the development of a diverse array of fillings, each distinct in nature and capable of delivering unique sensory experiences. 

Confectionery fillings are an essential part of various sweet treats, such as filled chocolates, gummies, licorice, and more. Some of the most common fillings are:

• Jelly/syrup fillings: Used mostly in gummies and marshmallows. It’s a non-stabilized mix of sugar solids in water. Uses gums such as Xanthan to provide thickness or other additives to get a firmer texture. Non-crystalline.
• Fondants: Micro-crystalline sugar suspended in a saturated syrup usually made of water, sucrose and corn syrup. It could also contain gelatin, starch or gums to modify its texture and flow. High crystalline content.
• Creams/Crèmes: Similar to fondant but slightly aerated.
• Liquor fillings: Fondants infused with alcohol. 
• Syrup fillings in chocolate: Obtained by an in-product process involving invertase breaking the sugar molecule of a sugar paste into fructose and glucose within the chocolate to produce a syrup. 

An important consideration in this context is moisture migration, which occurs when there is a difference in water activity between two components. When the water activity of one component is higher than that of another, moisture tends to migrate from the higher water activity component to the lower one. This can lead to undesirable changes in texture in both components, rendering the product unacceptable. Ensuring water activity equilibrium is essential to preserve the overall quality of the product.

Even when fillings can have different textures and consistencies, it’s general process is very similar.

Mixing and sugars dissolution: Granulated sugar is mixed with water and heated to create a sugar syrup. It’s very important to assure all large crystals are completely dissolved to form smaller crystals afterwardsto achieve a smoother texture. Corn syrup or glucose helps control crystallization.

Cooking: Either continuous or batch process can be used, cooking to the right temperature to assure crystals are dissolved is crucial. 

Cooling: In the case of creams and fondants, it should be done statically. For example, in a cooling wheel all the way to the beating temperature. This controls the nucleation and, therefore, the final crystallization rate and size. For syrups and jellies, this step might only be needed if adding a protein stabilizer such as gelatin.

Frappe addition (optional): For creams, this will impart the slightly aerated characteristics. 

Beating (optional): For fondant and creams, intense agitation is applied to generate massive nucleation of sugar crystals. 

Stabilizer Incorporation (optional): If used, stabilizer is added to the syrup mixture.

Minor ingredients incorporation (optional): Fats, nuts, flavorings and colorants are added at this stage to achieve the desired taste and appearance.

Secondary process: Filling will be sent to co-extrusion, forming, molding, enrobing, etc depending on the intended finished confection. 

The greater challenge when manufacturing fillings is reducing the extent of moisture migration. Some ways to achieve this are:

• Apply a barrier film between the moist and dry phases. This barrier film must have a low permeability. Lipids, in specific, shorter length systems, are widely used (palm kernel oil, coconut oil, milk fat).
• Introduce obstacles to the movement of the water. The thicker the barrier, the lower the permeance to let water migrate.
• Balance water activity of the filling and the confection.
• Invertase will soften or liquify filling depending on the addition level. It can also decrease water activity.