|Appropriate Food Packaging (Tool)|
|4 Filling and labelling|
Filling equipment is designed to handle solid foods, liquid foods or powders. In general manual filling methods are most commonly used for small-scale production. For each type of filler, however, a number of options of scale are available. These range from more convenient and accurate manual fillers through semi-automatic equipment up to fully automatic high speed systems.
4.1.1 Fillers for solids
The types of small-scale equipment for filling solid foods such as confectionery and dried foods is somewhat limited. In practice most producers fill by hand as the high cost of semi-automatic bag fillers cannot be justified by relatively low production rates. A scoop of known volume can be a useful way of obtaining similar weights of product in each pack. Ideally the scoop should fill some 90% of the required net weight into the pack. The pack is then passed on to a second operator who places it on a scale and adds product, from a smaller scoop, until the required net weight is reached.
Filling speeds can be increased by using a volumetric powder filler of the type shown in Figure 4-2.
At larger scales of production, plastic bags can be filled using small bagging machines or form-fill-seal equipment as has been described in Chapter 3.2.2. When filling into cardboard cartons the nomogram in Figure 4-1 is useful for determining the size of carton that is required.
Before using the nomogram, it is necessary to know the bulk density of the product (volume occupied by a known weight; usually 100 g). To measure bulk density 100 g of product is placed in a measuring cylinder. The cylinder is then tapped gently on a table, to settle the product down, and the volume occupied by the 100 g read off.
Tea bag filling is a somewhat specialized area of solid packaging as fairly high speed packing is necessary in order to reach an economic throughput. Tea bag paper is a special type of paper that combines great wet strength with porosity and heat sealability. Tea bagging machines work on the basic principle of form-fill-seal and small machines with outputs of 100 bags per minute are commercially available.
When using the machine in Figure 4-2 the lower valve is closed and solid product flows down and fills the tube. The top valve is then closed. On opening the bottom valve a measured volume of product falls out of the outlet. The distance between the two valves can be adjusted, allowing for good net weight control. Such fillers are not, as far as is known, commercially available, but can easily be built in a local workshop from drawings available from ITDG.
4.1.2 Liquid fillers
At the simplest level, liquids can be filled into containers using jugs. Small liquid gravity fillers can be made from a vessel such as bucket fitted with outlet taps (Figure 4-4). Two or five-gallon plastic tubs or double-walled water coolers with taps make useful fillers if the product is not too hot. At higher temperatures a stainless steel bucket can be used A small stirrer may be needed to prevent particles of food from settling out in the filler. Outputs of some 1000 packs per day are possible with such fillers.
Some products, such as sauces, flow rather slowly through a small tap and a different approach is required. A simple low cost filler (Figure 4-5) has been used successfully for such products. A large plastic funnel is cut so that the stem just fits into the bottle neck. A length of plastic rod acts as a simple on-off valve. In practice a team of four using such fillers with two people to cap bottles could produce some 6000 packs of sauce per day.
Several companies produce small hand-operated or semi-automatic powered volumetric fillers (Figure 4-6). These essentially consist of a piston working in a cylinder which pumps a known quantity of liquid food into the container. A whole range of cylinder sizes from few millilitres up to a litre or more are available. The length of the stroke of the piston is adjustable, allowing good net weight control.
Another approach is to use small vacuum fillers. These are commercially available and can also be made very easily locally. Figure 4-7 shows the principle of a locally made vacuum filler that has been successfully used for hot filling fruit juices. Vacuum is obtained from a water Venturi pump attached to a tap. These are obtainable from laboratory suppliers. One good feature of vacuum fillers is the fact that they give a constant fill level as when the level in the bottle being filled rises to the vacuum tube the juice starts to suck out of the bottle.