Unit 20: Introduction to biscuit- Making

UNIT 20: INTRODUCTION TO BISCUIT- MAKING
What is the biscuit?
One of the difficulties in writing about biscuits is that the very word means different things to different people. In America the word ‘biscuit’ is used to describe a chemically leavened bread- type product the nearest equivalent of which in the UK might be a scone. The products known as ‘biscuit’ in the UK are called ‘cookies and crackers’ in the USA. Throughout this book – which is being written by an English man – the word ‘biscuit’ is used as a generic term to include ‘biscuit’, Cookies and Crackers’.
Outline of the Basic Processes used in Biscuit – Making
Commercial biscuit manufacture comprises a series of highly mechanized operations, which progressively covert the original ingredients into the finished products. Dough mixing is still frequently carried out as a batch operation but the remainder of the processing steps is now usually continuous. The design of equipment used at each stage can vary quite widely and the operating conditions have been determined by previous experience refined by an on – going process of trial and error. The changes taking place during each of the processing stages and the factors affecting these changes are the subject of this unit.
Ingredient metering
Most large biscuit factories now receive and store their main ingredients – flour, fat, sugar, syrups, ect. – in bulk. The required amounts of these ingredients are then metered automatically in to appropriate dough mixer as required. However smaller ingredients and ‘chemical’ ( salt. Sodium bicarbonate, aerating agent, ect.) are still frequently weighed out and added to the mixers by hand.
Dough mixing
With the possible exception of some yeast – leavened products subject to a long fermentation process, biscuit dough mixing is much more than a mere intermingling of the ingredients. Some processing also takes place. Dough mixing conditions fall into two man groups. One group consists of the hard doughs where the flour protein is converted into a gluten network. The second group consists of the short and soft doughs, where the conditions are chosen to minimize the formation of a gluten network. The hard doughs are very stiff and tight, particularly during the early stages of mixing, and require considerable amounts of work input from the mixer motor. This work is converted to heat via frictional forces and produces a significant increase in the temperature of the dough. It is for this reason that such doughs are sometimes known in the USA as’hot’ doughs. With short and soft doughs the work input to the doughs during mixing is small and the temperature of the finished dough depends primarily on the temperatures of the major ingredients at the time they enter the mixer.
Formation of the dough piece
Biscuit – shaped dough pieces for crackers and semi – sweet products are cut from continuous sheets of hard dough. The stiff, visco – elastic properties of these doughs require them to be formed into sheets of the required thickness by rolling with heavy steel rolls. Cracker doughs require extensive processing to build up a series of thin layers, or laminations, in the final dough sheet. These laminations are necessary in order to obtain the desired flaky structure in the finished biscuit. Doughs for making semi – sweet biscuits on the other hand, if treated with an appropriate dough – conditioning agent, merely require rolling in order t obtain a suitable sheet from which dough pieses can be cut.
Some short doughs are also cut from a continuous dough sheet but owing to their lack of conhesion such dough are more difficult to handle in this manner. The majority of short doughs are currently formed into the shapes required by compression into dies engraved on a carefully designed roller. The equipment used for this processing known as a rotary moulder. Doughs which are to be formed on a rotary moulder require somewhat less water to be added to the doughs during mixing compared with those which are to be sheeted ad cut. Short doughs with a high fat content, i.e. soft doughs, are usually formed into the required shape by extrusion, the extrusion dough being subsequently cut to the required size by an oscillating wire (wire – cut cookies) or a guillotine (root - or bar – press products).
Baking and cooling
Large scale biscuit baking is now universally carried out in tunnel ovens (usually referred to incorrectly as ‘travelling ovens’) varying in length from about 30 to about 150 m. The products travel through the ovens on continuous baking supports which may be up to 1.2 m wide. Baking times vary from about 1 min to about 15 min, according to the product. Apart from some cracker products, which may be oil sprayed immediately after baking, most biscuit must be cooled considerably before they can proceed to sencondary processing or packaging. This cooling in normally achieved by transferring the biscuits in a single layer or in a shallow ‘penny stack’ formation, onto a canvas conveyor and allowing them to travel around the factory for a time which may be typically one – a half to times the baking time.