Packaging foods in glass
Practical Action
Self-adhesive labels can be bought, fixed to a backing
(or 'release') paper in rolls or sheets. They can be
applied by hand, by small hand held machines or by
powered labellers. The type shown in Figure 19 can
apply 30-40 labels per minute.
Quality control
This should be seen as a method of saving money and
ensuring good quality products and not as an
unnecessary expense. The time and effort put into
quality control should therefore be related to the types
of problems experienced or expected. For example,
glass splinters in a food are very serious and every effort
should be made to prevent them, whereas a misaligned
label may not look attractive but will not harm the
customers.
Figure 19: Powered labelling machine
Faults can be classified as:
Critical
likely to harm the customer or operator or make the food unsafe (eg glass splinters)
Major
likely to make the package unsuitable for use in the process or result in a serious loss of
money to the business (eg non-vertical bottles that would break in a filling machine)
Minor
likely to affect the appearance of a pack (eg ink smudges on the label)
Critical faults should always be checked for, whereas others may be examined, if they are
causing problems.
For glass containers the critical faults are broken, cracked, or chipped glass, strands of glass
stretched across the inside of new packs, or bubbles in the glass that make it very thin in
places. Major faults are variations in the size and shape of containers and minor faults
include uneven surfaces, off colours in the glass, rough mould lines and faults with the label.
One further quality control measure that is important with glass containers is to check
variations in the weight of jars and bottles as these variations will affect the fill-weight.
Random samples should be taken from the delivery of containers (eg 1 in 50 containers) and
weighed. The heaviest pack should then be used to calculate the final filled weight required.
Quality control needs trained staff, an established procedure and some equipment and
facilities. Staff are the most important and all operators should be trained to look out for
faults in the product or package. One staff member should have responsibility for checking
the packaging.
All glass jars and bottles should be checked for critical faults and if second-hand, checked
for contamination before washing. Other quality control checks include:
the filled weight (to ensure that the net weight is the same as that declared on the label)
the appearance of the pack
a proper seal formed by the cap
the presence and position of the correct label.
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