Application of sugar on a fried doughnut
The doughnut are best liked when dusted on with sugar. Simple at first sight, to do it at a high capacity, evenly and in a clean way is a challenge.
The doughnut is a flour based dough, formed, fried and cooled.
The coating ingredient may consist in :
– A light spray of fat or diluted syrup on top to improve adhesion if the remaining fat from the frying phase is not enough
– A finely ground sugar, icing sugar or more often a “deco” mix, made of icing sugar, starch, fat and flavour
How does it work?
The coating principle relies on the application of the ingredients through dribbling over the articles or tumbling in a powder bed.
The operation occurs usually in an enrober , powder applicator , which can be either topical dusting conveyor, a tumbler or a screw .
Typically, the doughnuts are deposited on a conveyor whose upper surface is already covered with the sugar mix. While the doughnuts are mover forward by the conveyor, the overhead trough delivers a curtain of mix. The doughnuts are totally covered with sugar mix. The excess is shaken off by means of a rotating came or similar device. The excess is recovered to be recycled. During recycling, the sugar mix may be sifted to remove agglomerates, thus preserving its initial functional quality.
It is usually a continuous operation in an industrial line. The coating sequences run as follows
Sugar dosing and application
Sugar sieving and recycling
There are various solutions to dust sugar on a doughnut: in a tumbler saturated with the sugar mix or a screw conveyor large enough to accommodate the different doughnut sizes.
Continuous screw sugar dusting system
How do you measure your success?
Key quality features
The main evaluation crietria are
Even distribution of the sugar. Coating the side or not decides on the choice of the coating technique
The system should not affect the overall shape by crushing or cause losses of particles (shear)
The coating should hold or not been absorbed during the further cooling, freezing and handling operations
Key quality parameters
The process factors depend on the product and the technique used
The shape, texture and state (temperature) affect the distribution and adhesion
Plain sugar – of different size particle sizes – or special sugar mixes are available
Design and operation
The motion applied to the product depends on principle (conveyor, screw, vibrating tray), design and operation (speed)