Handling of Dough after Mixing

Removal from the mixer

When the mixing of a batch of dough is complete it is normal to eject it from the mixer it immediately into either a tub/trough or directly into a feed hopper. This leaves the mixer free for a new mix. If, for any reason, it is desired to retain the dough in the mixer bowl for a period and the mixer has a water jacket around the bowl, ensure that the temperature of this jacket is similar to that of the temperature of the freshly mixed dough. If it is higher or lower there will be a local change of temperature of the dough which will mean that the dough will have a variable consistency when it is being machined into dough pieces.

In the case of vertical spindle mixers the mixing bowl is the tub which is used to take away the dough. In other cases, after the end of mixing, the mixer is opened or the bowl is tilted to remove the dough. In many cases the ejection of the dough is not completely automatic and some "help" is required. This should be done with care to ensure that no dirt or other materials become included in the dough. Use only metal tools to aid with the movement of the dough and do not hit the beaters or sides of the mixer bowl otherwise metal fragments may be lost into the dough.

Aim to completely empty the mixer, any dough that remains will behave like scrap dough and may affect the quality of the dough in the next mixing.

The dough will be used either without delay or after standing for a specified period.

Standing the dough

The period of time and the temperature conditions while dough is stood prior to use will be critical for all types of dough. The main types will be described.

Semisweet dough

It is considered best to mix these doughs to a relatively high and specified temperature (for example 41°C). After removal from the mixer, these doughs begin to cool and dry at the surface eventually becoming hard and crusty. As a result of the mixing action, and the heat which is developed, the gluten becomes extensible (it can be pulled out without breaking). As the dough stands and/or cools the extensibility and consistency of the dough deteriorate fairly rapidly. It is therefore desirable to use the dough without delay and at all times to protect it from cooling and drying. The size of each mixing of dough should be as small as possible compatible with the ingredient metering and mixing cycle time to produce a new dough and the rate that the dough is used.

Fermented cracker dough (Cream crackers and Soda crackers)

Yeast is used to modify the quality of many cracker doughs by a process known as fermentation. The yeast cells grow and multiply, feeding on components in the warm dough. In the undisturbed dough where there is no oxygen, the products of fermentation are alcohol, which can be smelt, and carbon dioxide gas, which is held in the dough as bubbles and causes it to rise in the tub. If the fermentation period is longer than 8 hours other changes will also occur in the dough as a result of bacterial growth. These changes include acid production and flavour change which contribute to the quality of the baked cracker.

Cracker doughs are relatively wet so must be protected from drying and the action (growth) of the micro-organisms is affected very much by the temperature of the dough. It is therefore critical to both mix the dough to a specified final temperature and to store it at a similar temperature so that the fermentation action is uniform within the dough and from one dough to the next.

Traditional fermentation of cream crackers and soda crackers (saltines) is for a long period, about 16 hours, This is called the sponge and dough method. The sponge is a relatively wet dough and after fermentation it is remixed with the addition of flour and some sodium bicarbonate. Modern techniques involve shorter periods of about 4 hours or less and here the mixing is "all in" and no remixing is involved.

It is normal to ferment cracker doughs in rooms that have controlled humidity (of 80-90%RH) and temperature. Great care must be taken not to leave doors open as it takes sometime for the humidity and temperature conditions to return to the desired levels if they are allowed to fall. If the storage area does not have humidity control close fitting lids must be placed over the tubs.

Fermentation procedures vary from product to product and from factory to factory. Sometimes there is a remix stage which may involve additions of other ingredients.

Enzyme modified cracker doughs

Another type of cracker dough requires the action of an enzyme which alters the nature of the gluten. The enzyme is a proteinase and is added during mixing as either a powder or a liquid. The amount of the action is dependent on time, the quantity of the enzyme that is used and the temperature. The temperature/time/enzyme quantity relationship is specified relative to the time taken to process a batch of dough and the amount of enzyme modification required for a particular product. If the speed of the reaction is too fast there may be a significant difference between the biscuits made from the start of a dough batch compared with the end, if the reaction is too slow there will be many tubs of dough waiting on the factory floor and mixing of the first dough of a production run may be at an inconvenient time.

It is essential that the temperature of the mixed dough is close to the specified value and the time that the dough stands is precisely controlled. As for fermenting doughs, humidity control is required to prevent surface drying.

Short doughs

The mixing time after flour is incorporated into a short dough is typically very short. This ensures that little or no gluten is formed. The dough is short, the opposite of extensible: it cannot be pulled out without breaking. There is a period after mixing when water is absorbed by the flour and any other cereal ingredients. The dough thus appears to be drying and becomes much less sticky. It also becomes harder. These changes soon stabilise and thereafter little gluten can be formed if the dough is mixed or worked in dough piece forming machinery.

The combination of the need to have little gluten in a soft dough and yet a more or less uniform consistency of dough while a batch of dough is being formed into dough pieces, places special requirements on the handling of short dough.

It can be shown that the change in consistency due to the water being absorbed becomes slower and slower. The maximum effect is in the first 30 minutes or so, thereafter the change is less noticeable although it does continue for several hours. It is therefore recommended that all short doughs are allowed to stand, without any agitation, for at least 30 minutes after completion of mixing.

If the holding period for short dough is in the hopper of a sheeter, or pre-sheeter, make sure that the dough is not "mixed" by the action of any agitators such as those that are designed to prevent bridging of the dough over the rollers. "Mixing" by agitators may result in a tough dough similar to the effect of over-mixing.

It will be appreciated that because of the changes which occur during standing the consistency of a short dough may be much softer at the end of mixing than can be tolerated by the rotary moulder or other dough piece forming machinery. Some experience is therefore needed to estimate the optimum consistency of a dough at the end of the mixing time.

There are some sugar and syrup rich short doughs that are exceedingly sticky after mixing. The stickiness reduces during the standing period. If this standing period is very long even the stickiest doughs become manageable in a sheeter or rotary moulder.

Removal of dough from the tub

Dough contained in a tub or trough is taken to the appropriate hopper and is transferred normally by tipping but sometimes by manual transfer. There are various mechanisms for tipping. In each case great care must be taken to ensure that dirt does not fall into the dough from external parts of the tub, such as its wheels or the forks of a tub tilter.

Empty tubs should always be covered to prevent dirt collecting in them prior to them being used for more fresh dough.