Coating a chewy candy with sugar crystals
A sugar-coated candy shows tiny sugar crystals stuck to its whole surface. It enhances the chewing experience by combining the inner mellow texture and the grittiness of the surface.
The core is generally a chewy candy: a hot sugar, gelatine, starch and flavour solution is poured in in pre-formed shape moulded in starch, then left to set, and ultimately separated.
The main ingredient is caster sugar, calibrated sugar crystals.
The liquid used to stick the sugar crystals is simply water turned into a food-grade steam.
How does it work?
The process consists in 2 operations: liquid and powder addition.
They are carried out in 2 different systems to avoid build-ups. The coating sequences run as follows
Wetting by steam to dissolve the surface
Addition of sugar in excess
Sieving and recycling of the excess sugar
The main operation occurs in a rotary tumbler. The candies travel on a conveyor. They pass through a hood where steam is injected. The combined action of heat and water partially melts the candy surface which becomes sticky. The wet candies are discharged in the tumbler.
The tumbler consists in one inner cylinder concentric to an outer cylinder.
The inner cylinder receives both the wetted candies and the sugar. Its end is perforated to remove the excess sugar.
The sugar in excess falls on the inner wall of the outer cylinder. A helical screw is built between the inner and outer cylinder. Its direction is such as to pull back the excess sugar toward the infeed zone where it falls onto the wetted candies again.
The feeder is adjusted to dose the quantity of sugar removed by the coated candies.
The bed of sugar is maintained to a level such as to allow immersion of the candies into a bed and prevent excess friction and force the crystal into the wetted surface.
It is a continuous operation. The rotation speed is adjusted to achieve a minimal residence time.
After coating, the product needs a short setting time for the moisture to equilibrate, the wetted sugar to dry and crystallize again
Steam station and sugar coating tumbler, courtsey of DF Drouven GmbH
How do you measure your success?
Key quality features
Although a simple operation, the outcome must be evaluated
The candy is homogenously coated with sugar. It is measured partially by the pickup rate and visually evaluated.
The sugar crystals adhere firmly to the candy
The sugar crystals retain the brightness and have not been dissolved into the surface
Key quality parameters
The process has fixed and variable parameters to chose and play with:
Tumbler length, diameter and helical screw design, inner volume
Rotation speed and tilt angle
To adjuts the residence time and dynamic volume of candies and sugar.
Adjusting the powder dosage in excess to provide a bed of sugar in which the candies roll