Summary of typical Process Control Points

The following is a typical summary of where records or measurements should be made during processing.

Ingredients and ingredient preparation

  • Records provided by Quality Control of when ingredients are drawn from new deliveries especially if the ingredient quality has changed. This would include when flour is taken from a different silo.
  • Records of daily checks of temperatures of bulk handled liquids.
  • Records of the times when solutions and suspensions (e.g., premixes, milk powder) were made and the quantities involved.
  • Records of scrap materials used and dough remaining at the end of the production run.

Metering of ingredients

Ingredient metering errors are the major source of biscuit processing problems. Typically, they cause many more quality problems than variations in ingredient quality.

The mixing operator is the most likely person to notice irregularities of the metering systems and he may have to be the person who makes corrections.

  • Records are required of apparent and actual malfunctioning of weighers or metering pumps.

Mixing of doughs

For each type of product mixing instructions and dough specifications must be provided for the mixing operator.

From time to time changes in procedures may be required. The reasons for these changes to routine may be as a result of plant stoppages, changes in ingredient properties and difficulties in later stages of the process which require small changes in formulation or dough mixing.

It is very easy for a small problem to become a large one if records are not made and actions communicated as required. If the mixer operator works in isolation from his colleagues on the baking plant he is not fulfilling his duty to be involved with product quality.

As an operator becomes more familiar with the process and generally more competent he may be tempted to "help the efficiency" by making changes that he is confident will be right but for which he does not have authority. The problem of this is that his action may not be in accord with what others are doing and the combined effect may result in unexpected difficulties. Therefore any ideas for change that fall outside given authority should be agreed at supervisor level before they are initiated.

Generally to maintain smooth processing, changes should be kept to a minimum and should only be made based on reliable measurements and against preset limits.

All changes in the mixing department must be recorded and communicated forward down the plant so that no one has a surprise when a different dough arrives!

Handling of dough after mixing

What happens to a dough after mixing and before being used in the dough piece forming plant are clearly defined in the Process Standards Document. To ensure compliance with these standards,

  • ├é┬árecords are required of times when new doughs are tipped. (If necessary these may be compared with the records of when the doughs were released from the mixer).
  • for fermented doughs, a record should be made if the surface is unusually dry and if the volume of the dough is different from standard (indicating that the fermentation may not have been normal).

Dough piece forming

Sheeting of dough

The sheeter feeds the dough to the rest of the forming plant whether it be a series of gauge rolls or includes a laminator. Unfortunately the speed that the dough naturally feeds from a sheeter is usually not constant. The speed depends on the height of dough in the hopper (the higher the faster the dough feed) and the dough consistency. The consistency will change due to dough age, temperature and the placement of the cutter scrap.

As the feed from the sheeter varies, the feed to the first gauge roll will be affected and if not adjusted this will affect the dough throughout the plant. There is therefore a need to make continual adjustments to keep the feed from the sheeter and thus the feed to the first gauge roll in control.

Dough piece forming

At start up it is important to set the speed of the cutter, rotary moulder, depositor etc. to give the desired number of dough pieces. This determines the production speed.

Also at start up it is necessary to adjust to give dough pieces of the weight set on the Process Standards Document. It is also necessary to check that the weights from both sides of the plant are equal. Thereafter it is not normal to regularly measure the dough piece weight and record this. If there is some interruption of the forming machine plant it will be wise to check the dough piece weights again.

Instructions to increase or decrease dough piece weights or to adjust the side to side weights will come from the control point after baking.

(It would be very useful to have an in-line continuous weight monitor to detect changes in dough piece weights before they are placed on the oven band. However such a machine is not yet available.)

The cutting pressure will affect the penetration of docker pins. Each time an adjustment to the cutting pressure is made a check is needed on both the dough piece weight and on the docker penetration.

For embossed cutting, checks for dough piece weight must be made when adjustments are made.

Rotary moulding

The speed of the moulder determines the production rate.

Adjustment will be required from time to time to ensure minimum tails on the dough pieces. When an adjustment is made for this or the extraction pressure a check should be made on the dough piece weight from both sides of the machine. It is not normal to record these measurements.

Extrusion and wire cutting

Weight control from extrusion machines is very sensitive to the dough consistency and the height of the dough in the feed hopper. Changes often affect the extrusions or deposits unevenly across the band so very great effort should be made to keep the level of dough in the feed hopper as even as possible and the age of the dough constant.

Laminating

It is very common to find that the placing of laminations is wrong. If vigilance is not maintained subsequent gauging and dough piece weight uniformity will be affected.

The number of laminations and the quantity of filling dust affect the development of the dough piece during baking. These may be used as control criteria in which case the settings must be recorded at least when changes are made.

It is normally difficult to measure the quantity of filling dust being deposited so control may be entirely visual.

NB On some laminators it is difficult to see if the filling dust is being deposited correctly. In these cases extra vigilance is necessary as an empty flour dust hopper or partial blockage will affect the baked cracker quality.

Dough piece decorating

Control of dough piece decoration (milk/egg wash, application of sugar, salt or nuts, printing) is normally only visual and no records are kept.

Baking

The baking time is defined as the time from entry of the dough piece into the oven to the time when it exits. There are normally bake time indicators on the oven which relate to the speed of the oven band. They are not all accurate but as the plant is set up using the instruments provided the "bake time" should be that which is indicated.

The productivity of the plant is determined by the speed that biscuits are being made and this is determined by the speed of the cutter, rotary moulder, depositor etc. and not the baking speed. The two will only be related if the dough pieces are always placed at the same distance apart on the oven band. Placing with similar distances all round to other dough pieces is important to give even colouration all round the biscuits.

The exit of the oven is a major process control point. Facilities must be in place here to measure and record against time,

  • biscuit weight
  • biscuit size (length, width, diameter, thickness)
  • biscuit colouration (top and bottom surfaces)
  • biscuit moisture content
  • biscuit appearance (surface blisters, cavitation on the underside, etc.)

Control charts or monitoring instruments will allow assessment of whether each biscuit parameter is in control or not. If not, action is required and monitoring instruments will alarm for operator intervention or on sophisticated plants will activate adjustments automatically.

BISCUITS THAT ARE FOUND TO BE SUBSTANDARD MUST BE REJECTED IMMEDIATELY OR MARKERS PLACED ON THE COOLING CONVEYOR TO INDICATE THE FACT TO WORKERS LATER ON THE PRODUCTION LINE.

ACTION IN THE EVENT OF OVEN BAND STOPPAGE

If the oven band should stop due to a power failure or mechanical fault it is essential that action is taken to wind the band either manually or with an auxiliary power supply (batteries). If the band is not wound on overheating and fire will occur in the oven which could lead to serious damage to the oven and the oven band.

All operators must know how to wind out an oven band and to know where the hot, burnt or biscuits that are on fire must be discharged. If they are allowed to pass to a canvas conveyor fire will spread.

Oil spraying

Oil sprayed onto biscuits immediately after baking may or may not have flavour included. The oil is relatively expensive so the amount applied should be checked regularly.

Secondary processes

Cream sandwiching

Sandwiching changes the biscuit weight and thickness. The weight is straightforward to check by the same method as was used at the oven exit. The thickness is less easy to measure because the cream is soft after the creaming machine. To wait until the cream has cooled is not satisfactory.

Vigilance is required to ensure that stacking of biscuits immediately after the sandwiching machine does not cause skewing or wedging of the soft sandwich.

The appearance of cream sandwiched biscuits is determined not solely by the weight of cream but also by the volume of cream. It is therefore necessary to control the density of the cream being applied. This done at the cream mixing stage.

Chocolate coating

Chocolate pick-up control

Despite the importance of correct chocolate weight on biscuits, it is difficult to monitor the chocolate pick-up in a continuous way. Basic or intuitive ways are used.

Chocolate temper control

Modern enrobers have excellent temper control and by circulating the chocolate through a warming and retempering phase optimum temper is maintained.

Older systems require more supervision and sometimes checks with special instruments.

Wafers

Sheet weights

Fundamental to the eating quality of wafer sheets is their weight. There should be a system in place for measuring and recording random samples of wafers for weight.

Sheet colouration and moisture content

The baked colouration and moisture content of wafer sheets are closely related. Not only should the general colouration of wafer sheets be monitored but also the variations from a complete round of plates of the wafer oven. Excessive variation will indicate that plate settings require engineering attention

Conditioning

Where wafer sheets are conditioned prior to cream sandwiching or chocolate coating regular checks for weight or moisture content should be in place to ensure that the conditioning tunnel is operating correctly.

Cream sandwiching

The cream used to make a wafer book is the most expensive item of the wafer product. Either an automatic checkweigher or regular manual measurements must be made to ensure that the correct percentage of cream is being used.

Handling and Packaging

Pack weight control

Legislation is very strict on pack weights. Offering for sale packs that are underweight is an offence. There must be systems in place to monitor pack weights and to record average weights at regular intervals. In many cases an automatic checkweigher will be in place immediately after the wrapping machine to detect and reject light weight packs. These checkweighers need to be regularly checked for calibration. Many checkweighers can electronically record pack weight variation over given intervals of time.

Pack seal integrity

Use of moisture-proof films to protect biscuits is a waste of money if the seals are not complete. Constant vigilance is required to ensure that the wrapping machine is making good and complete seals.

Foreign matter scanning

Inclusion of dangerous or unfortunate items within a biscuit or the biscuit pack is a matter for continuous concern. Attention to general factory hygiene is the first requirement but it is also wise to set an automatic metal detector immediately after the wrapping machine. This machine will reject packs that contain fragments of most metals.

There are more sophisticated scanners that can detect glass and other dense particles.

All scanning machines should be checked at regular intervals for correct performance.

Best before by date marking

It may be illegal to offer for sale packs without some form of date marking. Constant attention is needed to ensure that the code printer on the wrapping machine is performing correctly.