Cream Sandwiching

Types of creamed products

Cream sandwiched biscuits occupy a significant place in the world biscuit market. The term "cream" implies a non aqueous aerated mixture of sugar and fat.

Typically, two identical thin biscuits (the shells) contain a layer of sweet or savoury (non sweet and usually salty) cream. There are many variations on this basic type. For example the shells may be dissimilar in shape or colour and one shell may have a hole (or holes) through which the cream can be seen or in which jam is deposited. Cream sandwiched biscuits may be enrobed with chocolate to form a count line (a product that is wrapped and sold individually) or they may form the centre of a moulded chocolate bar.

The sandwich may be formed with wafer sheets in which case it may have multiple, two or more, layers of cream between wafers forming a "book".

The same type of cream may be deposited on a biscuit base but with no topping biscuit followed by chocolate enrobing.

The cream offers extensive opportunity for variations in flavours, colours and improved acceptability of a biscuit. The weight of cream is typically around 25% of the creamed sandwich, but amounts within the range 15-36% can be found. In general, the larger and thicker the biscuit shells the lower the percentage of cream. Wafer biscuits with two or more layers of cream usually are much richer, about 70% of cream by weight.

Methods of cream application

The operation of biscuit creaming was originally entirely manual involving the stencilling of the cream onto a base followed by the addition of a top. The stencil was cut in metal sheet of thickness appropriate to the thickness of the cream required and the shape of the stencil was appropriate to the size of the base biscuit. The base was located under the stencil hole, cream was filled and smoothed into the hole either with a palette knife or from a swinging hopper and the biscuit was then taken away with the cream adhering. The stencil plate was maintained at a temperature slightly higher than the cream to reduce preferential sticking of the cream to it. The cream needed to be fairly fluid but rigid enough to maintain a shape as the biscuit was withdrawn from the stencil plate.

3c-Creaming-stencil-thumbSequence for forming a cream sandwich by stencilling

This system was mechanised and creaming machines are still sold which operate on the stencil principle. They are usually intermittent in action allowing location of the biscuit beneath the stencil, filling of the stencil hole and then removal of the biscuit to a "topping" station where the top biscuit is pressed on to make the sandwich. Although this type of machine is relatively slow in action, the system does allow a second deposit such as jam to be applied on the precisely located biscuits before the top shell is placed.

Stencilling requires a fairly fat rich cream to maintain the desired fluidity and because the stencil plate thickness is fixed the only means of weight control is by changing the density of the cream. This is not easily achieved with most mixing equipment.

A second method of cream application is by means of multi-nozzled depositors, across a wide conveyor, of the cake batter type. The depositor head may lower and travel with the biscuit in a continuous motion or the head may be fixed and the biscuits moved intermittently. This system relies on the extruded deposit breaking away from the nozzle as the latter is raised so the cream must be quite fluid and the biscuit relatively heavy if clean operation is to be achieved. Suction systems have been devised to hold the biscuits down where necessary, but this is an engineering complication. The topping arrangement is similar to that for the stencilling machine. The quantity of cream deposited can be finely adjusted by the pressure in the depositing pipe and also by constriction of individual nozzles.

3c-Creaming-capping-thumbSequence for forming a cream sandwich by depositing and capping

Stencilling and depositing machines usually require the presentation of biscuits in rows on a conveyor up to one meter wide. Although this arrangement is possible as an in-line system, it is usual to feed the biscuits from magazines providing the appropriate number of lanes. These magazines are hand filled and an exactly similar magazine is required to provide the biscuits for the tops of the sandwiches. Speeds of up to 45 and 60 rows per minute are typical for stencilling and depositing machines respectively. The wide (row type) arrangement is ideal for cooling and subsequent presentation to a chocolate enrober.

In order to handle stiffer (lower fat content creams) and to increase production speeds, there are extrusion and wire cutting machines to meter and deposit the cream. Although the systems are sometimes referred to as stencilling, this is not accurate and there is a clear difference from the true stencilling arrangements. Cream from a hopper is pushed out of a nozzle of appropriate shape, the cream is located onto the biscuit base and it is then severed from the nozzle with a taut wire. Machines of this type operate on a continuous motion which extracts a biscuit from a magazine feed onto a pinned chain. The biscuit is transported under a rotating nozzle arrangement such that as a nozzle and biscuit coincide there is an extrusion of cream which presses onto the biscuit and is then cut off with the wire. The creamed base moves onwards to a topping station where the pin pushing the biscuit extracts a top biscuit and the two are pressed together under a wedge or roller (see figure 5).

3c-Creaming-wire-cut-thumbSequence for forming a cream sandwich by extrusion and wire cutting

Most machines of this type, cream only one to four lanes of biscuits, but at speeds of up to 800 biscuits per minute per lane. Lane multiplication devices allow a doubling or quadrupling of the number of lanes as they leave the machine for the purposes of biscuit cooling and penny stacking. It will be appreciated, however, that this arrangement means that longer narrower cooling conveyors are required than those that follow the stencil type machines.

Baker Perkins developed a full width creaming machine of this extrusion and wire cutting type with as many tracks as there are lanes on the oven band. Only every other biscuit is creamed, the alternate biscuits being used to provide the top biscuit of the sandwich. This machine can run at baking plant speeds, reduces the handling needed to fill biscuit feeders and presents the biscuits for cooling and subsequent enrobing in an ideal arrangement. It is, however, very inflexible being limited to a given number of lanes of biscuits for each cream extrusion cylinder. Changing the cylinders and other parts to suit different biscuit sizes or numbers of lanes is a major task.

The extrusion creaming machines not only handle firmer creams, but also allow some weight adjustment at the point of cream application. A disadvantage is that at very high speeds there is frequently damage to the biscuits as they are taken from the feeding magazines. Very fragile or irregularly shaped biscuits, also oval shapes, are difficult or impossible to handle. The lane multiplication and stacking of sandwiches with soft cream may result in distortions that are not suitable for packaging when the cream is set.

Mixing and handling of creams

Cream may be mixed on batch or continuous systems. The difficulties of handling soft, sticky, messy masses of cream have encouraged interest in continuous mixing systems.

The batch systems usually commence with block or pumped quantities of plasticised fat. Bulk handling of plasticised high dilatation fats needs to be critically controlled because the plasticity is easily lost if the temperature rises too high. When the sugar and other ingredients are added the temperature of the whole must be lower than that required in the mixed cream. By a beating and blending action the mass is slowly warmed and there is incorporation of air. At the end of mixing the cream should have a desired temperature, density and consistency. It is difficult to precisely control all these three features in relation to one another (though consistency is ill-defined) unless close attention is given to the temperatures and qualities of the ingredients. The ranges in properties of the mixed cream that are acceptable depend on the type of creaming machine and the type of fat being used. It is advisable to regularly monitor the cream properties and to relate variations with creaming machine performance and biscuit weight control.

Cream densities vary from 0.75 to 1.15g/cc. In general the low density creams are used on depositor type machines and the highest densities on extrusion wire cut machines.

Many creams are difficult to discharge from the mixer, will not flow into pumping systems and have to be man-handled. There are, therefore, potential labour and hygiene problems.

Pumping a mixture of fat and sugar presents particular wear problems and oil seals are sensitive to the abrasive nature of sugar.

Process control considerations

The cream sandwiching operation requires attention to four key parameters,

1. The weight of the sandwiched biscuits must be to specification.

2. The alignment of the sandwiched biscuits must be accurate both after creaming and after cooling otherwise the biscuits will look untidy and may not fit into the packaging.

3. The thickness of the sandwich must be correct and even, not wedged. This can be adjusted by pressure immediately after sandwiching. Wedging may occur if the sandwiches are badly stacked after creaming and before cooling, while the cream is still soft.

If the density of the cream is not within specification the filling may be pressed out from the sandwich and will "soil" adjacent biscuits and look untidy, alternatively at the correct weight the deposit may look very small and not extend near enough to the edges of the sandwich.

4. The sandwiches must not fall apart after cooling. Adhesion of the shells to the cream is related to the previous consideration, pressure after sandwiching. A optimum pressure is required and a significant change in fat solids due to cooling. It is the development of fat crystals in cream that has been pressed into the shells that causes adhesion. Thus if the cream density is low and little pressure is required to give sandwiches of the correct thickness the cooled biscuits may fall apart.

Creamed biscuit cooling

In most cases creamed sandwiches are held in a cooling tunnel to set the cream before the biscuits are packed or further processed. Sometimes no cooling is done and the sandwiches are immediately and mechanically fed to wrapping machines. The latter arrangement saves space and time, but there is much risk of product spoilage due to the squeezing out of the cream. Only firm low fat type creams, or biscuits containing very little cream, are suitable for handling without cooling. It is unsatisfactory to manually transfer freshly creamed sandwiches to wrapping machines as the pressures involved in picking up the biscuits distort their size and shape.

Where cooling is done, this should be enough to effect a desired firmness of the cream on the hottest day. Cooling air temperatures should be adjusted so that the biscuits are not taken to below the dew point otherwise condensation will spoil the biscuit shell quality.

It is best that the biscuit shells should be as cool as possible before creaming, as cooling of creamed sandwiches is a slow process.