Preservation
without chemical additives
(Except salt, sugar, alcohol and vinegar)
It is useful to have some prior knowledge when you preserve food yourself. When you understand why food deteriorates and spoils, and how to avoid deterioration, it is easier to preserve successfully.
Microorganisms
Microorganisms are the main reason why food spoils and becomes dangerous, and under certain conditions, all microorganisms will flourish and increase in size.
1) Good food hygiene
2) Use of high temperatures
3) High concentrations of sugar, acid and salt.
4) Removal of air are important measures to keep microorganisms away.
Enzymes
Enzymes are proteins that are found in all plants and are active for a long time after harvest. They act as catalysts for change and initiate and accelerate chemical processes that, for example, provide a breeding ground for microorganisms.
For example, when apples discolor after being cut in half, this is caused by an enzyme reaction. If the surface of the cut comes into contact with something acidic or alkaline, the discoloration process will be much slower.
This is why cut fruit is often dipped in lemon water or salt water when preserving. Enzymes thrive at temperatures between 29 and 50°C. At temperatures above 60°C they begin to deteriorate. Below the freezing point they stop working, but they start working again as soon as they are warmed up.
Types of bacteria
Bacteria increase rapidly in number at temperatures between 20 and 40°C.
They go into hibernation when placed in the freezer and are destroyed at temperatures up to 100°C.
The fact that food is spoiled by bacteria can sometimes be difficult to detect.
And although the vast majority of bacteria are harmless, some bacteria contain harmful toxins making it important to take certain precautions.
Molds and other fungi
Fungal spores are present in almost every airspace around us and will take root in almost any type of food. In the beginning, they form long and thin mycelial strands, followed by the well-known gray-green puffball-like fruiting. Mushrooms hibernate at temperatures below 0°C, they thrive in temperatures between 10 and 38°C, and are greatly reduced at temperatures from 60 to 88°C. A little mold on the top of an opened jar of jam must not be removed with a spoon and ignored. The jam is poisoned by potentially dangerous toxins.
Yeast fungi
Most yeast fungi are not harmful, but they can spoil food. Most species are destroyed at temperatures above 60°C, and inactivated at temperatures below 0°C.
Types of preservation
Preservation by boiling
Almost all harmful microorganisms die at high temperatures. When food is packaged completely hermetically to protect it from attack by microorganisms, it is best to cook the food in the heat-resistant packaging in which it will be stored. You can only use boil-proof trays and jars.
The temperature to be reached depends on the moisture content of the product, the acid content and the duration of cooking.
At high temperatures, microorganisms are destroyed more quickly in water-containing products than products with little water. Acid intensifies the destruction of microorganisms during cooking. The temperature therefore does not need to reach 100°C when boiling acidic fruit. Cooking must last long enough for the entire contents of the packaging to reach the desired temperature. The consistency of the contents will therefore have a major impact on cooking time.
Boiling in a water bath at 98°c
This method is suitable for whole or divided fruit and vegetables cooked in a sugary brine, vegetables and mushrooms cooked in acidic brine, sweet must and acidic vegetable juices. At the bottom of the kettle there must be an insulating grate so that the jars do not stand directly on the bottom of the kettle.
The jars are placed so that they do not touch each other and enough water is added to cover 2 cm above the jars. When cooking in open bottles, the water level should be about 2 cm below the top of the bottle. The exact temperature must be reached within 20-40 minutes.
If the product is heated more quickly, it will not be thoroughly heated. If the water is heated later, fruit in particular can easily boil out. Once the water bath has reached the correct temperature, this must be maintained throughout the cooking period. Then remove the jars immediately and cool them down.
Preheating and cooking in a water bath
When cooking food that takes a long time to heat through, the product is first heated to the boiling point in a saucepan and filled into heated jars. Fill the jars to 1/2 cm below the lid and seal them immediately with a rubber band and metal clamp or other suitable sealing method. They are then immediately placed in a boiling water bath and boiled for 10-15 minutes and cooled immediately after that.
Storage
Always check that the jars are hermetically sealed, otherwise the contents must be used without storage or the process can be repeated. Storage in a refrigerator, cold room or other dark room with a temperature between 3-10°C is ideal.
Sugar preservation
The most common ways to preserve sugar are in the form of jams, marmalades and jellies, but there are also a number of other techniques. Jams, marmalades and jellies are all made from fruits and berries that are cooked and more or less starch, sugar and acid are added.
Jams have a less firm texture with remaining pieces of berry or fruit. Marmalade has a firm consistency, the fruits or berries are pureed. Gelè also has a firm consistency, but is transparent and is made from the juice of the fruit or berries.
The advantage of homemade sugar-preserved products is that there are no chemical additives or pesticide residues. What's more, the vitamin C content is much higher than in industrially preserved products. It is the high sugar content that makes it suitable for storage, and the right ratio of sugar to pectin that gives it its jelly-like consistency.
The natural sugar content of fruit and berries is often insufficient and sugar must be added up to 65% of the total weight. A concentration of 60% sugar creates an environment that is hostile to microorganisms.
Sufficient acidity is found in apricots, strawberries, currants, rowan, blackcurrants, gooseberries, sour cherries and cranberries. Blackberries, blueberries, raspberries, peaches, elderberries and sweet apples need to be acidified. Fresh lemon juice works well for this purpose.
Pectin is a type of dietary fiber found naturally in many fruits and berries. Apples (unripe), fire quinces, quinces, currants, blackcurrants and gooseberries are the most pectin-rich and often do not need added pectin when they are sugar-preserved. Apricots, blackberries, strawberries and plums contain somewhat less pectin. While blueberries, raspberries, elderberries and cherries contain minimal pectin. Unripe fruits contain the most pectin, with the content decreasing as they ripen. Pectin is available in several varieties on store shelves, but if you want to avoid added pectin altogether, you can add pectin-rich fruits and berries to pectin-poor fruits and berries. Another option is to make your own pectin-rich fruit or berry concentrate. In low-pectin jams, marmalades or jellies, you can replace 1/3 of the fruit with this concentrate and add it after all the sugar has been added.
Pectin concentrate: Rinse (and cut fruits such as apples, fire quinces and quinces into eighths with skin and core). Pour water over the fruit (3.5 dl of water per kg of fruit) and bring to a rapid boil. Cook on a low heat for 40 minutes. Strain into boil-proof jars (e.g. Norges jars), close and cook on a low to medium heat for 10 minutes.
Vinegar preservation
Food preserved in vinegar is often the type of food referred to as 'pickled'. For vinegar preservation to be successful, the acetic acid content must be at least 5%. Few microorganisms can survive in such concentrated acetic acid. Vinegar preserves are easy to make, and you don't need to consider pectin and acid levels as with sugar preservation.
Vinegar preserves have many uses - they can be stirred into soups, added to stews and casseroles, served with marinated or smoked fish, and used as an ingredient in a sandwich.
Salt preservation
High concentrations of salt keep yeasts, bacteria and molds at bay. Salt is also used to extract water from food, which also has a preservative effect.
Alcohol preservation
For alcohol to be effective in preservation, the alcohol content must be at least 40%.
Oil preservation
Oil is very useful as a top fill to minimize air space before sealing, and also serves as a very good flavor additive in many products.
Drying
Fruit, vegetables, mushrooms and herbs can all be preserved by drying. The water content is reduced so that microorganisms have nothing to grow in. The disadvantage of drying is often a loss of flavor, but it can also have a flavor-enhancing effect. In addition, there can be a fairly significant loss of nutritional content. Vegetables can also lose their ability to absorb moisture.
To avoid this, they should be dried at lower temperatures. The danger is that unfortunate enzyme changes can take place. What is a good temperature varies from plant to plant. Blanching (pouring boiling water over and leaving to soak) some vegetables for a few minutes in lightly salted water destroys the enzymes that discolor and cause vitamin C loss during drying. Sweetening fruit before drying also has a preservative effect.
The fruit must not be dried at too high a temperature. In the beginning, fruit should be dried at between 40°C and 60°C so that the surface does not become too hard or the juice runs out. Later, the temperature is increased to 70-80°C until the fruit or berries have some water content left. Then the temperature is lowered to avoid loss of flavor and color. Fruit can be pre-dried and post-dried in the sun. When no juice comes out of the fruit or berries when you press them, the drying process is complete.
Freezing
Freezing is the preservation technique that best preserves the original appearance and taste of what is being preserved. When stored in a freezer for as long as 1 year, the temperature must be at least -18°C.
Fruit and berries should be frozen when fully ripe and firm, and should be frozen immediately after harvest. Stems, cores and any peel are removed. Larger fruits are cut into smaller pieces. Fruit varieties that oxidize quickly and turn brown are dipped in lemon water (5 grams of lemonade per liter of water).
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