Rotary moulding process
Cotton belts (woven) are widely used in the biscuit baking industry, and some have been replaced by synthetic materials, but not always with positive results. An example of this is in the application of endless extraction webs in the rotary moulding process. A newly installed endless woven belt, is of a ‘coarse surface texture’ and needs to be surface treated uniformly with water or steam, so as to prevent differential tension/contraction, before commencing production.
This treatment is usually only required pre-production and there-after the moisture/fat expressed from the rotary moulded dough pieces, are absorbed into the weave of the web. I have experienced some elaborate methods of treating these woven belts, with flour, water, or fat - flour blends and also sugar syrups, all with varying degrees of success, and considerably reduced ‘life span’ of the extraction web, compared with the water or steam only application.
Synthetic webs have been used as a replacement for the endless woven web, but they too require some surface treatment to aid the extraction of dough pieces from the moulding roll onto the surface of the web. The function of this web is to influence the suction of the dough pieces from the moulding roll and transfer them onto the panning web and then onto the oven band without distortion of the dough pieces
In the laminating of Cracker Dough, cotton webs have been used extensively for transferring the dough sheet between gauging rolls. Their surface finish is critical in ‘relaxing’ the dough sheet between the reduction gauging rolls, to prevent the dough sheet from ‘shrinking’ on the belt.
In my application of ‘cold air’ to the dough sheet prior to lamination, I have preferred a porous web, to surface skin the dough sheet, and subsequently, influence the increase in stack-height of the crackers. This is due to the ‘cold air’ that has been trapped between the dough sheet layers, rapidly expanding in the hot oven.
Gauge roll processing
As the dough sheet passes through the gauging rolls, cotton webs are used to transfer the dough through each of the rolls. The web surface texture is critical in contributing to the ‘reduced’ dough sheet relaxing between each stage, until being discharged from the final gauge roll, again with the objective to prevent ‘shrinkage’.
As the dough sheet is transferred onto the relaxation web, the surface finish is of a different texture than the previous web, this allows the dough sheet to gently relax, due to the differential speeds of the feeding web and the cutting web, influencing the extensibility of the dough sheet and preventing longitudinal shrinkage of the biscuit/cracker.
The cutting web, has a different surface texture from the previous webs, as the objective is to adhere the dough sheet to the web, to prevent pick-up from either the embossing and or the rotary cutting roll, without distorting the dimensions or shape of the dough pieces.
Photo source: Arville