The cells of fresh fruits and vegetables naturally contain water, which means they can break down (perish) rather quickly after being harvested, packaged, and shipped to the store. Even if you purchased “farm direct” (or grew your own fresh produce), having a larger quantity of fresh food than required equals quality/nutritional loss or food spoilage (food waste) if food preserving techniques i.e. water bath canning are not undertaken at the correct time.
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

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