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Preserving, use & nutrition

Wild berries are at their best fresh, but preserving makes them a year-round part of the diet. Berries can be frozen as they are, dried, crushed, juiced and cooked into jams.

Four ways to preserve

Freezing

The best method for retaining nutrients: berries keep in the freezer until the next harvest season. Freeze whole, crushed, as jam or as juice as soon as possible after picking. Sugar is not needed – if you wish, about half a decilitre per litre of berries is enough. Soft-skinned berries such as raspberries and cloudberries are frozen in boxes without rinsing; hard-skinned ones such as lingonberries can go in bags – a bag shaped flat freezes fastest. Thaw berries quickly in a microwave or a warm water bath, which destroys the least vitamin C.

Drying

Dried berries keep their flavour and most nutrients well. The maximum drying temperature is 50 degrees. Sufficiently dried berries are light and hard – they take little space and storage uses no energy.

Fresh crush and raw juice

Lingonberry, cranberry and cloudberry naturally contain plenty of benzoic acid, so they keep as a crush in the cold without sugar, heating or preservatives. Rinse the berries before crushing, put the crush into clean glass or plastic containers and keep the berries covered by juice in the fridge – the crush keeps for months. Raw juice is unheated, 100-per-cent juice; it keeps best frozen.

Preserving with sugar

Jams, marmalades and jellies need quite a lot of sugar (0.5–1 kg per kilo of berries), since sugar builds the structure, binds the berries' water and inhibits yeasts, moulds and bacteria. Juice made by boiling or steaming takes 200–400 grams of sugar per litre; low-sugar juice is best stored frozen. Finished jam, marmalade or jelly is stored cold.

Shop-bought frozen berries, jams and juices complement your own harvest. Remember, though, that imported frozen berries are not recommended for use without heating.

Why berries every day?

Berries are nutrient-rich yet light: plenty of vitamins, minerals, fibre and polyphenolic compounds relative to their energy. The recommended amount is about two decilitres a day – for example on morning porridge, in yoghurt, in cooking and in baking.

Sea buckthorn and cloudberry are rich in vitamin C – about one decilitre covers the daily need.
Bilberry and lingonberry are rich in polyphenolic compounds; wild bilberries have 3–5 times more anthocyanins than cultivated highbush blueberries.
Many berries also provide vitamins E and A as well as folate.
The nutritional value keeps best when berries are eaten fresh – or frozen.

Energy and fibre per hundred grams

Berry	Energy (kcal)	Fibre (g)
Bog bilberry	38	2.4
Cranberry	32	3.5
Cloudberry	55	6.3
Bilberry (wild)	65	3.3
Rowan berry	75	6.5
Lingonberry	56	2.6
Sea buckthorn	57	3.6
Raspberry	48	3.7
Crowberry	44	9.5

Source: Finnish Institute for Health and Welfare, Fineli 2026.

Basic recipes

Lingonberry juice (raw juice)

Ingredients

4 l lingonberries
2 l water
25 g tartaric or citric acid
6 dl sugar

Method

Clean the berries and crush them with a food mill, blender or masher.
Boil the water and let it cool. Pour the cooled water over the berry crush and stir in the tartaric or citric acid.
Let the mixture stand for two days in the cold, stirring a few times.
Strain the juice through a muslin cloth. Measure the juice and stir in 300 g of sugar per litre until dissolved. Bottle.

Juice made from acidic berries keeps in a good storage place without pasteurising until Christmas; keeping it the whole season requires freezing or pasteurising. Instead of lingonberries you can use crowberries or cranberries.

Basic jam recipe

Hard-skinned berries (lingonberry, cranberry, rowan berry)

Ingredients

1 kg (approx. 2 l) berries
3–4 dl water
600–700 g (7–8 dl) sugar

Method

Boil the water and sugar for about 10 minutes and add the cleaned berries.
Simmer the jam over low heat for about half an hour. Shake the pot now and then so the berries don't stick, and skim off the foam.
Jar the jam brim-full into well-washed, heated jars and seal immediately with lids you have sterilised by boiling.

Soft-skinned berries (raspberry, bilberry, bog bilberry, cloudberry)

Ingredients

1 kg (approx. 2 l) berries
500–700 g sugar or 500 g jam sugar and 0.5 dl water

Method

Layer the cleaned berries and sugar in a pot and let the berries release their juice in a cool place for a few hours.
Heat the juicy berries slowly to the boil and simmer gently for about half an hour until the berries sit evenly in the syrup. Do not stir – shake the pot and skim the foam with a slotted spoon.
Jar the hot jam brim-full into well-washed, heated jars and seal immediately with lids you have sterilised by boiling.

Instructions: Luonnonmarjat tutuiksi guide (Marttaliitto ry & Arktiset Aromit ry). Nutrition facts: THL, Fineli.

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