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Preserving Tips

1. Background

2. Freezing 

3. Drying

4. Smoking 

5. Vacuum packing

6. Canning/ Bottling

7. Fermentation 

8. Preserving with Salt 

9. Preserving with Oil 

10. Preserving with Sugar

11. Preserving with Acid 

12. Preserving in Alcohol 



1. Background to preserving and why.

Understanding the principles of each method means when you see a recipe in a book or on the internet you will know which parts are important, what you can and can’t adapt and if things go wrong you will have a better idea why.

Food spoils because of enzymes, microorganisms, bacteria, moulds and yeasts.

To preserve food one must control these.

Enzymes: cause browning, controls ripening, enzyme action continues to ripen fruits and vegetables and this needs to be stopped to prevent over ripening or spoilage.

Microorganisms (Bacteria):  Important for food safety. Need to kill any unwanted microorganisms and stop any new ones dropping in.

Mould and yeasts: Rotting, fermenting and spoilage.

These are generally controlled by heat.

Enzyme action can be stopped at 75°C, usually by blanching. Browning can be stopped with salt and acid eg. lemon juice on cut fruit.

Some bacteria need higher heat as they can have heat resistant spores which can survive up to 6 hours of heating.

Most cooking doesn’t continue heating for that long. However these bacteria are sensitive to acid so normally they are only found in low acid foods such as meat, fish and low acid vegetables. To kill them they need high temperatures for a long period of time and this is often only achieved by canning or using a pressure cooker.

Moulds: Usually grey & fluffy with no foul smell.  If mould is small and can easily be removed it is safe to eat the food.  Moulds are killed if food is heated to 60°C for 30 minutes or shorter times if temperature is higher.

Yeasts:  Causes fermentation and have a fermented taste and smell. If growing inside container /jar the lid will be distended because they produce gas.  They alter taste and texture so undesirable to eat. Yeast is sensitive to heat (destroyed above 60°C)

Both yeasts and moulds are in the air so can grow in air spaces in jars, bottle quickly in sterlised jars.

Evidence of spoilage will be:

Sour smell, mushy food, Rotten / decay – smells like bad eggs, gas may break seal.

Discard without tasting.

Toxin – unseen and looks and smells as it should. Clostridium botulinum is the scary one here It can kill quickly. Low acid foods are safer frozen as the low temperatures prevents the bacteria forming toxins.

The other method of preservation is to make an uninhabitable environment for those unwanted spoilers by reducing the temperature, water availability, high sugar, salt or acid.

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2.Freezing preserves by reducing temperature and water activity

Freezing Tips

  • Turn freezer down low before starting so items freeze faster with smaller ice crystals.
  • Freeze small portions so it freezes faster and freezer stays cold – (smaller ice crystals achieved)
  • Remove air from bags or containers (try vacuum pumps) for better freezing.
  • Headspace required for expansion in liquid items
  • To free flow, freeze items on a tray uncovered before sealing in zip lock bags.
  • A bacterium multiplies on thawing so thaw in the refrigerator and when freezing have clean hands and freeze into clean containers.
  • Remember after freezing is complete return freezer to normal setting


Blanching vegetables destroys enzymes and any bugs you may not have seen.

To Blanch: Boil water in a large saucepan. Using a basket drop in prepared vegetables. Return quickly to the boil quickly and start timing. Usually only a few minutes, remove basket and drain and quickly cool for a few minutes in ice cold water. (A colander in a clean sink of ice water works well)  Drain and freeze. Cook these items for a shorter time than fresh and there is no need to thaw.

Exceptions to blanching are capsicum, chilli peppers and onions.

Avocado can be mashed with lemon juice and returned to skins and wrap them in foil or plastic and freeze.


 Always pick ripe fruit washed and dried fruit can be packaged as it is for jam making or use later in cooking.

Berries are easily free flow frozen, store in a zip lock bag.

Raw puréed fruit can be frozen without sugar, add ascorbic acid or lemon juice to prevent browning.

Raw sweetened fruit is good for desserts or cooking later, sprinkle cut fruit with caster sugar stand for 3 minutes toss so all is covered with sugar before packing into bags or containers, removing air.

Raw fruit which tends to brown can also be dropped into sugar syrup (An equal quantity of sugar dissolved in equal quantity water) then frozen.

Or freeze cooked fruit. Don’t overcook and cool it quickly and freeze in suitable portion sizes.


Tomatoes can be frozen whole for later cooking keep for just 4 months if tomatoes are blanched or puréed keep for 12 months.

Herbs can be washed, drained and freeze whole or chopped for use in cooking. Kaffir lime leaves, parsley work well. Basil chopped and made into ice blocks with water or oil. Alternately make pesto and freeze. This helps it to keep its flavor and colour.






2-3 months

Fruits and Vegetables

9-12 months



9-12 months



3 months


Poultry & Meats

9-12 months



If a breakdown or power outage occurs:

  • Keep freezer door shut.
  • Thawed food refrozen- not harmful just loses quality, flavour and nutrition.
  • If ice crystals still present refreeze but use sooner than recommended
  • Completely thawed, but cold, bread cakes ok, vegetables throw away, fruit cook or make jam, refrigerate meats or seafood to cook immediately

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3.Drying – preservation by reducing water activity

Drying has the advantage of being low weight and takes up less space when storing.

A dehydrator costs power and it can take at least a day for most items longer for bigger pieces and high moisture items like tomatoes, plums and grapes.

You can also use the oven on fan bake 50°C, with door open to let out moisture.

Air drying is unpredictable in Auckland. It needs 8-30 days for different fruits and longer if there is high humidity or rain.

Try drying in a glasshouse or carport where it is hot and there is good air circulation.

Maybe build a sun dryer here’s an example.

Fruits work well but brush cut edges with lemon juice or syrup to reduce browning. Or make fruit leathers from pureed fruit.

Vegetables which you may like to try are beans, peas, carrots, celery onions, mushrooms and corn.

Herbs - Small leaf herbs like thyme, oregano can be washed and tied in bundles then hung in a warm, airy place to dry, or dried in the dehydrator.

Larger herbs leaves can be blanched to retain colour then dried in a dehydrator or oven until they are dry enough to crumble.

Dry seeds for cooking such as coriander, celery, dill, fennel. Harvest stem when seeds are ready to drop and hang in bunches over something to catch them or a paper bag in a warm airy place then thresh the seeds out before storing in jars or tins.

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Smoke is antimicrobial and anti-oxidant but smoking alone doesn’t preserve food. To preserve the food it needs to be dried or salt cured. The smoking gives the vulnerable exterior more protection from bacteria.

Hot smoking is usually applied to meats and fish and imparts flavor and extends shelf life for a few extra days.

Hot smoking can be done in oven, wok, hooded BBQ or a purchased smokehouse.

Cold smoking below 30°C is slow. To protect it from bacteria during the smoking process it is usually brined. It is important it is done correctly and needs a specially built smoker.

For more info try this Book: The Kiwi Sizzler Smoking Book – Chris Fortune

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5.Vacuum packing - preserves food by excluding oxygen.

Suitable for nuts, coffee where it extends the normal shelf life and retains quality and flavour.  Due to reduced oxygen fresh fish, meat and vegetables can last up to 5 times longer and it helps retain quality when freezing.

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6.Canning/ bottling

In America canning is the same as bottling. But food can be preserved both in glass jars or metal can. Metal cans require specialized equipment.

The principle of bottling is that the cooked food is sealed in a sterilized container without air.

You need to ensure the product going into them is free of pathogens or the process eg. canning (high temperature for long time cooks the product) kills the pathogens.

The safest way is to use sugar and acid to act as preservatives.

Fruits are easy and safe and are usually kept in sugar syrup. Because fruit are low risk for food poisoning it is possible to use a light syrup and reduce the sugar or even use no sugar at all, though once opened they need to be used quickly.

Alternately replace up to ¼ of sugar with honey. (Raw honey should be sterilised)

It usually requires some sugar because bottling requires firm fruit which are often not fully ripe, therefore less sweet.

How to Bottle fruit:

1. Firstly make syrup by bringing the sugar and water to the boil


Light syrup

1 cup sugar

3 cups water

Medium syrup

1 cup sugar

2 cups water

Heavy Syrup

1 cup sugar

1 cup water

*You will need 1 -2 cups of syrup per 1 litre jar

2. Wash, peel, core, stone if required. Place cut fruit in salt or acid (lemon juice or ascorbic acid) solution so they don’t brown until they can be packed into jars. Depending on bottle method either cook or pack into jars

*Approx. 1 litre jar per kg fruit

Open Pan Method

Open pan where the fruit is cooked in a preserving pan then packed into sterlised jars when hot (remove air with knife or skewer) and topped up with boiling syrup to overflowing and sealed using seals and rings. Be sure no fruit pulp is on rim before sealing.  Refrigerate or redo any jars which haven’t sealed once cooled.

To reprocess any jars they need to be emptied out cleaned, resterilised and repeat the entire process. Alternately refrigerate and eat immediately.

Water bath method

This method needs a container/pot with lid into which the preserving jars while sitting on a trivet can be fully immersed in water. This water is kept boiling.

Pack fruit cold or cook firm fruit partially before packing into hot sterlised jars. Leave a 2cm gap at top of jar, pour in boiling syrup or water up to 1 cm and wipe rim with a scalded cloth. Place prepared seal and screw on band loosely. Lower into the water bath. Don’t let the jars touch each other. Process for the recommended time, then lift out and tighten bands. Cool away from draughts, remove bands once sealed. Refrigerate or reprocess and jars which haven’t sealed.

Don’t let them cool in the water bath, they will overcook.


Oven method

Heat oven to 140°C. Prepare fruit as per cold pack method above. Cover jars with foil. Stand jars on an oven rack in the centre of the oven, don’t let them touch each other or sit them on a tray. Place a baking dish below to catch any drips or spills.  Process to set times and then remove one by one to a draught free spot where you top up with boiling syrup or water, wipe with scalded cloth and seal with sterlised seals and screw on the bands.(Can’t use seals before processing as the rubber on the bands will break down and not seal).


Processing times for different products are listed in on the box of seals, Edmonds cookbook, other preserving books and easily found on the web.

Bottling Tips:

  • Used uncracked jars with no chips on rims.
  • Always use new seals, bands can be reused.
  • Wipe and label jars before storing in a cool dark place.


To Sterilise jars: Wash in hot soapy water or in the dish washer and then place in oven at 120°C for 15 minutes, place seals in boiling water, bring to boil for 1-2 minutes, ensure bands are clean.


Vegetables, meat and fishare a real risk of botulism, despite the heating spores can live past boiling point and happily multiply in low acid environments.  To be safe don’t taste food from the jar and heat for 15 minutes before serving. Where this isn’t practical I suggest freezing or pickling. Homemade baked beans, spaghetti in sauce, soups and tomato pulp can work because these products will all be cooked well before eating.

Bottle beetroot using vinegar, cook, peel and slice beetroot and make a hot syrup using 2 ¼ cups vinegar, ¼ cup water sugar and salt. Add beetroot and bring to boil before packing and sealing as per the open pan method for fruit. The vinegar and heat will destroy any pathogens.

Tomato sauces and purees can also be bottled, because of the long cooking times to reduce the tomato liquid to a pulp. Seal and process in a pressure cooker or water bath.

Whole tomatoes need to be packed with water which has acid added ¼ teaspoon citric acid per 500ml jar. Processed in pressure cooker or water bath.

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Fermentation for the production of alcohol or vinegar is another way of using excess produce, but the fermentation of foodstuffs for health benefits is growing. History has seen most cultures consuming some sort of ferment eg yoghurt / cheese/ kefir, sauerkraut, kimchee, fermented corn and fermented soy beans.

By fermenting these products it extends their life and they are often consumed in the winter months when fresh vegetables are scarce. The natural probiotics in these products help with our immune system making winter time a great time to consume them.

All of these encourage the growth of the desired bacteria so there is no room for other types.

To find out more about this try these books

Wild fermentation by Sandor Ellix Katz

Weston A. Price - books and website

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8.Preserving with Salt

This needs about a 20% salt solution in brine or salt cured which dehydrates the product (less water activity makes an inhospitable environment). This provides an environment for good bacteria eg lactobacillus acidophilus, which lowers the pH making the food inhospitable to the other bacteria, sugar is often added to control the salty taste.

Nitrates and nitrites although undesirable and controversial are also often used to cure meat and contribute the characteristic pink color, as well as inhibition of clostridium botulinum.Care needs to be taken that correct amounts are used.

Preserving lemons use both salt and acid in the lemon juice

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9.Preserving with Oil

Oil excludes air but many bacteria can grow in oil so it’s important anything preserved totally in oil is free of any bacteria and the jars and lids are sterilised. The New Zealand climate is often too warm and humid for safe storage so ensure it is kept quite cool or refrigerated.

Ensure no part of the food sits above the oil

Otherwise use oil to sit on top of a brined or acidic solution. eg. olives, preserved lemons, vegetables, pesto.

Books to try:

            Preserving the Italian Way - Pietro Demanio

Preserving Food without Freezing or Canning – The Gardeners and Farmers of Centre Terre - Vivante

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10.Preserving with Sugar - Jams and Jellies

Jams & Marmalade - stewed fruit with sugar and cooked until it sets adding pectin if required.

Jellies- are clean/ clear set fruit syrup. Time consuming, lower yields and high sugar, good for some fruits which don’t make good jam eg. grape, guava, elderberry. Delicious to make mint or parsley jelly.

Conserve – The process is a little different and resulting in whole pieces of fruit. Less pectin is extracted from the fruit so they do not set as well as jams. They sometimes use less sugar thus reducing their keeping times..

Candied / crystalized fruits- are fruits which have been cooked then cooked in sugar syrups with higher sugar concentrations over a number of days, and then it is dried.


To make Jam

1.    Prepare fruit as soon after picking as possible to preserve natural pectin. Use ripe but not over ripe fruit and cut off any bruising or spoilage.

2.    Soften fruit over a gentle heat in a large pan with water, lemon juice or pectin (if recipe calls for it).

3.    Add sugar and dissolve while stirring then bring to the boil and boil rapidly until setting point is reached.

4.    Bottle while hot into sterlised jars and cover.


Usually to every kilo of fruit add 900g -1kg sugar.

Batches between 1- 3kg of fruit  work the best


Setting tests

Test for setting the easiest being lifting from a spoon and the liquid will change from drips to large drips or flakes. 

Take a little and sit in a saucer until cool meanwhile take the pan from the heat so as not to overcook. When it sets and the top forms a film and wrinkles it will set on cooling. It always sets more when cooled.

Reach a temperature 105°C with a sugar thermometer. But don’t rely on the thermometer alone perform the other tests as well.


Most common reasons for failing to set are due to differences in water and pectin in various fruits and even different seasons, varieties and times when picked.

This chart is only a guide always test for setting.



Fruits high in pectin


Fruits with medium pectin

Fruits low in pectin

Black currants









Plums ( sour)






Red currants



Cooking Apples







Plums (sweet)



Pectin can be added by using a pectin liquid or powder or using jam setting sugar which has added pectin. Pectin stock can be made from  tart apples, citrus peel, gooseberries or red currants.

Acid in the form of lemon juice is added to low acid fruits to help setting. 1 -2 tablespoons is usually added per kilo of fruit.


Jam Tips:

Jams use a lot of sugar and this cannot be reduced without risking the jam not setting, fermenting or going mouldy. Reduced sugar jams need to be refrigerated and used quickly. Sealing using the  waterbath will also help for longer keeping.

A steady rolling boil of the jam is required  for a good set. Unset jam can be re-boiled, but if there is not enough pectin will not set and it will be hard and chewy. If unset remove from jars and add pectin before re-boiling the jam until setting point is reached

Stir often in the early part and when heating the sugar to prevent it sticking and burning.

A preserving pan with sloping sides is the best type of saucepan to use. It also needs to be large enough for the jam when the volume is increased as it boils up.

Scum or foam is common in most jams and looks unattractive. Remove scum by with a spoon before bottling or adding a teaspoon or two of cold butter.


Jellies are made by cooking fruit with water until soft.

The pulp is then strained for at least 1 hour or overnight through jelly bag made of fine cotton or linen.  The resulting juice is boiled up with sugar Usually in the ratio of 1 cup sugar for every 1 cup of juice.

This is boiled like jam and tested for setting in the same way as for jam.

Jelly needs added acid or pectin or high pectin fruit for a good set.

Be sure not to squeeze the jelly bag while the pulp is dripping or the jelly will be cloudy.



Conserves are made in two different ways.

1.    A thick sugar syrup is made with sugar and water before adding the fruit and cooking until setting point.

2.    Fruit and sugar are mixed together and left overnight for the sugar to draw out the juices. It is then cooked up and tested using the same method as jam making.

These methods draw less pectins from the fruits so will give a softer set. Adding pectin is recommended.

Always cut the fruit to the size desired in the finished jam because conserves don’t cook down the fruit and they have larger pieces of fruit.


Fruit Butters & Cheeses

These use fruit cooked then pureed. Sugar is added before further cooking. Fruit butters have a softer set and fruit cheeses are cooked down until firm and able to be cut. They are often served with cheese. 


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11.Preserving with Acid


Pickles, Chutneys, Relishes and Sauces use acid and sugar to preserve.

Pickles are often brined first (soaked in salt or salt water overnight) to draw out water from the vegetables and astringency from onions.

Relishes are usually more sour with the vegetables finely chopped.

Chutneys are sweet often using fruits and vegetables.

Sauces have similar ingredients to a chutney and it is sieved or strained to give a thick puree.

Ketchup is a sauce but it usually is tangier due to more vinegar being added.

Chutneys or relishes are cooked enough when they are thickened and there is no free liquid when a spoon is drawn through the centre of the saucepan. Watch it closely at the end so it doesn’t burn.

A sauce is thickened enough when a teaspoonful is placed on a saucer and it doesn’t weep any liquid.

There are many great recipes for relishes, pickles, chutneys and sauces so here’s a few tips.

Tips for Pickles Chutneys, Relishes and Sauces

·         Sterlise jars and lids well

·         Use not metallic lids with high acid products

·         Use a quality vinegar, use white vinegar for clear products where  you want the flavor of the other ingredients to come through.

·         Use malt vinegar for colour and flavor.

·         Use white and brown sugar in the same way as the vinegars.

·         Don’t reduce the vinegar or sugar content in a recipe as this is the preservative, you can always add a little more for a slightly more sour or sweet flavor.

·         Use fresh spices avoiding dusty old spices.

·         Cook with the lid off and stir often to prevent sticking and burning

·         Use a quality heavy based stainless steel saucepan or preserving pan to cook these products in. Don’t use copper, aluminum or cast iron this can taint your pickles.

·         Use plain salt without iodine or free flowing agents to avoid cloudiness, taints or residues.

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12.Preserving in Alcohol

Any fruits work well preserved in alcohol. Use clean unblemished fruit and spirits such as brandy, gin, vodka, rum, whisky or grappa. Add sugar if wished and entirely cover the fruit in alcohol. Leave for at least 6 weeks