FILLING AND SEALING
PACKAGED FOODS
Introduction
This Technical Brief describes the methods for filling and sealing food containers in small-scale
processing. For more detailed information on packaging materials used for foods, see Technical
Brief: Packaging Materials for Foods, and the special considerations when packaging foods in
glass containers are described in Technical Brief: Packaging Foods in Glass.
The requirements when filling foods into containers are:
To accurately fill the correct amount of food to prevent under-filling (a legal requirement in
most countries) and to prevent product ‘give-away’ by overfilling.
To avoid spillage or contamination of the sealing surface so that the container can be
properly sealed.
The ability to maintain the quality of a food for the required shelf life depends mostly on adequate
sealing of containers. A wide variety of closures are used to seal containers, to suit the properties of
different foods and their expected shelf life. However, seals are the weakest part of containers and
also suffer more frequent faults, and precautions needed to adequately seal containers are described
below.
Filling
Solid foods are either in the form of large pieces (e.g. cut fruit and fish) or particles that flow
like liquids (e.g. powders, rice, beans, maize etc.). At a small scale of operation, large pieces are
usually packed by hand whereas powders and small particulate foods can often be filled using
similar fillers to those used for liquids. These fillers are described in this Technical Brief.
Liquids can be either thin (e.g. milk, wines and juices) or thick (viscous) such as oils, pastes,
creams, sauces or jams. No one type of filling machine is suitable for all types of foods and the
selection of suitable equipment depends on the viscosity, temperature, particle size and foaming
characteristics of the product, and the production rate required.
Filling thin liquids and particulate foods
The simplest manual filler is a jug, but this is often too slow. A simple manual filling machine for
liquids is made by fitting one or more taps to the base of a large bucket or tank. The bucket should
be stainless steel for filling hot acidic liquids (e.g. fruit juices) or food-grade plastic for cold filling.
The taps should be ‘gate-valve’ types and not domestic water taps, which are more difficult to clean.
In manual filling, the amount of food dispensed into the container is judged by the operator, and
training is required to ensure that consistent volumes are filled into every container.
There are a variety of dispensing machines that control the volume of liquid that is filled into each
container, and do not rely on the judgement of an operator. Timed gravity fillers are an economical
type of volumetric filling machine, but the range of applications is limited to low-viscosity liquids
that do not foam (e.g. bottled water and alcoholic spirits). The product is contained in a tank above
a set of pneumatically operated valves. Each valve is independently timed to deliver precise amounts
of liquid under gravity into the containers. Another type of filler is a ‘dispenser’ that is fitted with a
3-way valve (Fig. 1). In the first position the valve allows a cylindrical chamber to fill from a tank
above. It is then moved to the second position to empty the food into a container below. The volume
of food in the cylinder can be adjusted to fill different sized containers.
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