Recipes for water
bath canning safely have detailed information on the preparation for fresh fruits
and vegetables (choosing fresh, ripe, high-quality produce), including peeling
and pre-heating these ingredients if required, as well as adding an acidic
ingredient - like bottled lemon juice, vinegar or citric acid - to vegetables,
tomatoes and low-acid fruit varieties. Jar types for water bath canning are also
specific: new lids or seals for water bath canning are recommended, jar sizes
can be up to one litre (one quart) and must be processed in a water bath canner
for the correct time (at your altitude) as per the recipe.
Food spoilage (or
quality/nutritional loss) in fruits and vegetables may be caused by oxygen or
enzymes which are found throughout the tissues of fresh food:
o Moisture
– loss of moisture i.e. lower humidity (dried out/hardened produce) or soggy
produce due to a higher humidity (absorption) or from the cells naturally breaking
down and releasing water;
o Oxidisation
– when oxygen is present, a chain reaction occurs. May start off as colour
darkening/dulling or the production of off-odours/off-flavours;
o Food
enzymes – these chemicals are found naturally in food. Mainly composed of
protein, enzymes speed up chemical changes that reduce colour, flavour and texture
in food;
Food spoilage may
be caused by the growth of undesirable microorganisms, which are found on the
surface of fresh food and on the inside of damaged or diseased food. They
multiply very quickly!
o Bacteria
– microscopic spoilage microorganisms that break down food to create mushy, slimy
and/or smelly spoilt food;
o Mould – as mould grows on food, it produces
enzymes that break the food down. Some moulds also produce harmful toxins.
Mould spores spread from one food to another and can contaminate surfaces
around them i.e. refrigerator;
o Yeast –
multiply to create gas and enzymes, affecting food flavour, odour and
consistency.
The steps in each water bath canning recipe are very
specific to ensure food safety and to preserve (acidic) food for a
long storage period whilst retaining a high quality. Enzymes and yeast are destroyed
via the heat processing in the water bath canner. Processing and the correct acidity
(pH) prevents bacterial growth. Oxygen removal via vacuum sealing (the end result
of the water bath canning process) prevents mould growth. A strong vacuum seal means
moisture is retained in canned food - whilst keeping microorganisms and air
out.
Author: Megan Radaich
Image Credit: Megan Radaich
Publication: www.foodpreserving.org