Birch and Maple Sap: Chemical Composition
Spring is approaching and nature is waking up. Soon birch and maple sap will start to flow. Some say there's nothing of value in the sap, that it's just slightly sweetened water. Others, on the contrary, claim that sap contains all sorts of substances the human body needs and benefits from. So what's really true?
I browsed the internet and found some factual material. I read with interest an article by specialists from the Faculty of Food Technology at the Latvia University of Agriculture (link provided below). In Lithuanian, the title of this publication translates roughly as: "Determination of Bioactive Compounds and Mineral Substances in Latvian Birch and Maple Saps."
Determination of Bioactive Compounds and Mineral Substances in Latvian Birch and Maple Saps
Māra Kūka1 / Ilze Čakste1 / Endija Geršebeka1
1Faculty of Food Technology, Latvia University of Agriculture, Lielā iela 2, Jelgava, LV-3001, LATVIA
Citation Information: Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences. Volume 67, Issue 4-5, Pages 437–441, ISSN (Print) 1407-009X, DOI: 10.2478/prolas-2013-0069, December 2013
Since Lithuania and Latvia are close neighbors (with a similar climate), it's likely that the chemical composition of Lithuanian birch and maple sap will be similar. First, I suggest looking at the chemical analysis results presented in the publication, and afterward I'll briefly comment on them.
Table 1. Some quality indicators of the saps.
Birch sap Maple sap
Specific electrical conductivity
(EC), μS/cm 629 967
Titratable acidity,
mmol NaOH/L 0,50 0,70
Proteins, mg/L 127 171
Ascorbic acid (vitamin C), mg/L 3,2 8,8
Antioxidants, mg/L 0,35 0,77
P.S. In the article, the EC units are given in S/cm, i.e., units a million times larger. I hope the article's authors won't mind that I corrected the mistake.
Brief comment: we can see that birch and maple sap contain quite a fair amount of various substances. First, I want to draw attention to the EC, which is genuinely high. As a reminder, EC is proportional to the concentration of electrolytes. For comparison, the water EC at the Antaviliai water supply plant in Vilnius fluctuates around 500 μS/cm, meaning this water has fewer dissolved salts than birch sap, and almost half as much as maple sap. Both types of sap contain proteins and even a bit of vitamin C.
To my own embarrassment, I have to admit I don't really know which chemical substances are classified as "antioxidants." Strictly speaking, the term "antioxidant" should really refer to reducing agents. But reducing agents (weaker or stronger) include pretty much all organic substances. So it's unclear why proteins and ascorbic acid are singled out, especially since ascorbic acid is a fairly strong reducing agent. I suspect the authors of the article themselves don't fully understand what antioxidants are. Lately this term has been used widely, especially in advertisements for various supplements. Antioxidants are credited with almost miraculous powers – for instance, it's claimed that they bind "free radicals" and thereby slow down the aging process. One thing is clear: there's still a great deal of uncertainty in this field.
Table 2. Carbohydrate concentrations in the sap.
Birch sap Maple sap
Glucose, g/L 4,46 1,33
Fructose, g/L 5,39 0,55
Sucrose (sugar) 0,58 17,95
Brief comment: we can see that birch sap contains considerably more glucose and fructose than maple sap. Meanwhile, with sucrose (sugar) it's the opposite; maple sap contains about 30 times more sucrose than birch sap. The body can directly absorb only glucose and fructose. Sucrose must first be broken down before it can be absorbed.
Table 3. Mineral substance concentrations in the sap.
Birch sap Maple sap
mg/L Jelgava Ozolpils Tukums Ozolpils
Calcium 53,3 41 61 91
Potassium 41,1 66,4 70,1 78,9
Manganese 0,5 0,52 – 0,24
Iron 0,10 – – –
Sulfates 36,1 34,0 39 62,3
Chlorides – 9,0 9,0 12,0
Phosphates 6,3 7,2 12,6 –
Ammonium 0,06 – 0,10 –
Nitrates 15 15 15 15
Nitrites 0,026 0,039 – 0,378
Brief comment: we can see that both types of sap contain quite a lot of mineral substances. I think the mineral composition of the sap depends mostly on the mineral composition of the soil and groundwater. I'm somewhat surprised by the fairly high potassium ion concentrations; in maple sap, they even exceed the calcium ion concentrations. If that's really the case, it's a good sign. Potassium is very important for the body. On the other hand, the data presented in Table 3 show that tree roots are able to draw the nutrients needed for growth from the soil and groundwater, namely nitrogen, potassium, and phosphorus.
Now, about the promised experiments of my own. Unfortunately, I didn't manage to carry out any more serious testing this year. It so happened that right when the birch and maple sap was flowing, I had some interesting work with water samples. By the time I finished that work, the birch and maple sap had already stopped flowing. I only managed to collect a mere 10-12 mL of birch sap. That amount wasn't enough for a more serious analysis. I only measured the pH and specific electrical conductivity (EC). The results were as follows:
pH …………… 5,78;
EC …………. 833 μS/cm.
The fairly low pH value was somewhat surprising. Then again, all vegetables and fruits are more or less acidic (pH < 7). Why would sap be any different.
The fairly high EC value shows that birch sap contains a good amount of mineral substances (electrolytes).