Birch sap may be consumed both fresh and naturally fermented. When fresh, it is a clear and uncoloured liquid, often slightly sweet with a slightly silky texture. After two to three days, the sap starts fermenting and the taste becomes more acidic.
Birch sap is collected only at the break of winter and spring when the sap moves intensively.
Birch sap collection is done by drilling a hole into the tree trunk and leading the sap into a container via some conduit (a tube or simply a thin twig); the sap will flow along it because of the surface tension. The wound is then plugged to minimise infection.
Birch sap has to be collected in early spring before any green leaves have appeared, as in late spring, it becomes bitter. The collection period is only about a month per year.
No published evidence exists to quantify the long-term impacts of sap harvest on birch tree and birch forest health, or birch timber quality. However, the wounds caused by tapping birches consistently lead to dark staining in the wood. In one study, infection and wood decay had spread from more than half of old tapping holes.
In comparison to maples, birch trees are considered far less tolerant to the wounds caused by tapping, so more conservative harvesting practises have been recommended by trade bodies such as the Alaska Birch Syrupmakers Association.
In Slavic regions the sap is known as birch juice as in Russia (Russian: берёзовый сок, romanized: byeryozovyi sok), Belarus (Belarusian: бярозавы сок, romanized: biarozavy sok, Byarozavik), Bulgaria (Bulgarian: брезов сок, romanized: brezov sok), Poland (Polish: sok z brzozy, oskoła), Ukraine (Ukrainian: березовий сік, romanized: berezovyi sik).
|Nutritional value per 100 g (3.5 oz)|
|Energy||4.6 kcal (19 kJ)|
|Dietary fiber||0 g|
less than 0.1 g
|†Percentages are roughly approximated using US recommendations for adults.|
Birch sap contains heterosides (betuloside and monotropitoside), 17 amino acids including glutamic acid, as well as minerals, enzymes, proteins, betulinic acid and betulin, antioxidants, sugar (fructose, glucose and small amounts of sucrose) and vitamins (C and B(group)). Contrary to popular belief, there is no xylitol in birch sap (xylitol is a sugar alcohol that is industrially produced using high temperature and sulfuric acid, or through fermentation).
Nutritional and medicinal uses
|Region||Medicinal use||Cosmetic use|
|Belarus||lung diseases, gout, sickness||washing hair|
|Czech Republic||poor health, infertility||against freckles|
|Estonia||(prevention of) eye diseases, skin diseases, source for vitamins||washing hair, against freckles and to bleach the skin|
|Hungary||stomach and lung diseases||against freckles|
|Poland||“revitalization”, kidney stones||washing hair in order to strengthen it|
|Romania||kidney stones, jaundice, as milk-rennet, scab, diuretic||hair colouring, to remove sunspots and moles|
|Russia||externally against sores, to help children during teething||washing face|
|Ukraine||treating skin diseases, source of vitamins, diuretic||against freckles|
|United Kingdom||tonic, rheumatism, first nourishment for new-born children||prevention of baldness|
|United States||Poor health|
Commercial birch sap and derivative products
Birch sap may be consumed both fresh and naturally fermented. Fresh birch sap is highly perishable; even if refrigerated, it is stable for only up 7 days. Shelf life can be prolonged by freezing or preservation techniques. Existing preservation techniques include:
- Nothing i.e. bottled fresh sap (shelf life: 2–5 days refrigerated)
- Filtered with a 0.22-μ net (shelf life: 3 weeks refrigerated)
- Collected under anaerobic conditions (shelf life: 1 year ambient)
- Added sugar (3 g per 100 ml)
- Heat pasteurized, pasteurization should be conducted under specific temperature levels and times (shelf life: 1 year ambient). Although level of Vitamin C is lower than fresh saps', all other benefits are preserved.
- Frozen at −25 °C (shelf life: 2 years)
Concentrated birch sap is used to make birch syrup, a very expensive type of syrup mainly made from paper birch in Alaska and Canada, and from several species in Latvia, Russia, Belarus, and Ukraine.
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- Kallio, H; Ahtonen, S (1985). "Identification of the Sugars and Acids in Birch Sap". Journal of Food Science. 50 (1): 266–269. doi:10.1111/j.1365-2621.1985.tb13328.x.
- Nicole & Olivier Lhomme, NICOLL-Nature, Le Bio Logis, La sève de bouleau
- Alaska Birch syrupmakers association Petition to US Food and Drug Administration for establishment of Standard of Identity for birch syrup, including the Alaska Birch Syrupmakers' Association Best Practices. July 18, 2005.
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