The palatability of a backed product is enhanced by a glaze which gives it a shine reflecting the light.
Base
There is a very wide range of baked product which van be glazed : doughnut, croissant, bun, bread ...
Ingredients
The glazing ingredient may differ depending on the product but can be classified into main categories :
Light glaze provided by milk, milk protein, soy protein, egg;
Medium glaze with a glucose syrup;
Heavy glaze provided by:
A sugar fondant,
Chocolate, in this case the operation refers as enrobing rather than just glazing.
Process
The glaze must be prepared ant its preparation can be thoroughly different according:
Light glaze : dispersion or dilution of a protein-rich powder or of a concentrated slurry into a lighter suspension,
The preparation must be kept cold to prevent microbial growth;
Medium glaze : dilution and heating of a concentrated glucose syrup,
The preparation must be kept hot to keep the viscosity low and allow the application;
Sugar fondant : the preparation involves dispersion of fine sugar in a concentrated sugar solution,
The preparation must be kept at constant temperature and agitation to maintain its physical properties - whiteness, viscosity and crunch - resulting from the balance between dissolved and finely crystallized sugar;
Chocolate : the solid chocolate must undergo a complex operation called tempering : melting, cooling, partiel re-melting,
The preparation involves a complex system which ensures melting, agitation, circulation and temperature control before use.
The coating operation consist in applying the glaze on the product while avoiding losses on the immediate surrounding:
The product enters the coating zone;
The coating is applied - see the next heading,
Losses are recovered or cleaned;
The coating is stabilised by either adequate way:
Baking,
Drying,
Cooling;
It is a continuous operation in most cases.
Coating system
Different coating systems can be used:
Spraying for accurate application of a low viscosity liquid;
Curtain and recovery/recycling of excess in the case of the thick application of a viscous fluid;
The difference between the systems lie in the engineering details designed to cope with constraints : cooling/heating, recycling, cleanliness and cleanability.
Key
The process displays critical factors to control:
Ingredient composition - concentration, solid particles - in the way it influences its physical behaviour;
Viscosity control by temperature control;
Precision of application : dosage and targeting;
Hygiene as the product itself or the production environment offer ideal conditions for a microbial growth.
Among the glazed products, the croissant is a star.
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