Arabinoxylans in einkorn are non-starch polysaccharides belonging to the hemicellulose fraction of cereal cell walls [1]. Their structure consists of a main chain of β-(1→4)-D-xylose residues, to which α-L-arabinose residues are attached laterally in different positions [1]. The degree of substitution and the distribution of arabinosyl groups determine their solubility, water-binding capacity, and the rheological properties of the flour system [2].
In wheat flours and ancient cereals, including diploid wheats such as Triticum monococcum, arabinoxylans represent a significant component of the non-starch fraction and play an important role in the technological properties of dough [1;2]. They are generally classified into water-extractable arabinoxylans (WE-AX) and water-unextractable arabinoxylans (WU-AX) [2].
Water-extractable arabinoxylans contribute to the viscosity of the liquid phase of the dough, promoting gas retention and influencing the stability of the fermentative foam [3]. Water-unextractable arabinoxylans, on the other hand, are more closely associated with the structure of the grain cell wall and can mechanically interfere with the continuity of the gluten network, especially in wholemeal or less refined flours [3].
From a rheological perspective, arabinoxylans exert a dual effect: on one hand they increase the water absorption capacity of the flour, competing with gluten proteins for hydration; on the other hand, they can contribute to the stabilization of the dough matrix through physical interactions and, in some cases, through bonds mediated by phenolic acids such as ferulic acid [4].
In the context of baking with ancient grains and flours with limited gluten development capacity, such as einkorn, the presence and behavior of arabinoxylans are particularly relevant because they can influence the balance between matrix hydration, protein mobility, and fermentative gas retention [3;5], thus contributing significantly to the final crumb structure.
Studies on arabinoxylans in einkorn (Triticum monococcum) exist, but they are less numerous than those on common wheat. However, the literature clearly shows three important points:
1️⃣ the arabinoxylan content in einkorn differs from that of modern wheats
2️⃣ there is genetic variability among genotypes and cultivars
3️⃣ the distribution and solubility of arabinoxylans influence dough technology
1. Arabinoxylan content in einkorn compared to other wheats
Several comparative studies on cereal fiber show that:
1 – the total arabinoxylan content in einkorn is generally lower than in modern bread wheat [6].
2 – but the fiber composition may be richer in low molecular weight soluble fractions
For example, a study on fiber in hulled wheats (einkorn, emmer, spelt) shows that:
1 – in bran, arabinoxylans in common wheats are about 12.7–22.1% of dry matter
2 – whereas in einkorn and emmer they are about 6.1–14.4% [6].
This means that einkorn has on average:
1 – less structural arabinoxylans
2 – a slightly different cell wall structure.
This is consistent with the fact that einkorn doughs are often:
1 – more extensible
2 – less structurally rigid [3].
2. Variability among einkorn genotypes
Variability among cultivars is documented.
A study on hulled wheats analyzed different einkorn genotypes grown in the same environment and found:
1 – statistically significant differences among genotypes in soluble fiber fractions
2 – differences in low molecular weight soluble dietary fiber fractions (SDF-LM) [7].
In practice:
1 – some einkorn lines have:
2 – more soluble fiber
3 – others more insoluble fiber
4 – and this changes dough behavior.
This is very important for baking.
3. Distribution of arabinoxylans in the grain
Microscopy and spectroscopy studies have shown that:
1 – arabinoxylans are distributed in the cell walls of the endosperm and bran [2].
2 – there are two main forms:
LS-AX (low substituted arabinoxylan)
HS-AX (high substituted arabinoxylan) [2].
This difference affects:
1 -solubility
2 – interaction with water and proteins [2;3].
3 – dough viscosity.
4. The most important factor: genotype + environment
One of the clearest findings in the literature is this:
the content and properties of arabinoxylans depend on:
1 – genotype (cultivar)
2 – environmental conditions
3 – year of cultivation [8].
For this reason, two different einkorns can behave very differently in baking.
5. Direct link with baking
Arabinoxylans mainly influence:
1️⃣ water absorption [2].
2️⃣ dough viscosity [3].
3️⃣ gas retention [3].
4️⃣ interaction with gluten [4].
In cereals with weaker gluten (such as einkorn), arabinoxylans in einkorn can become an important structural factor, because the network is not supported only by proteins but also by the polysaccharide matrix.
✅ Concise scientific conclusion (arabinoxylans in einkorn)
The literature indicates that in einkorn:
1 – the total arabinoxylan content is on average lower than in modern wheat [6].
2 – there is significant variability among genotypes [7].
3 – the composition of soluble and insoluble fractions can influence hydration, viscosity, and dough behavior [2;3].
Bibliography
[1], Izydorczyk, M. S., & Biliaderis, C. G. (1995).
Cereal arabinoxylans: Advances in structure and physicochemical properties.
Carbohydrate Polymers, 28(1), 33–48.
DOI: 10.1016/0144-8617(95)00077-1
Sintesi: defines structure, degree of substitution, and relationship with solubility and functionality.
[2]. Courtin, C. M., & Delcour, J. A. (2002).
Arabinoxylans and endoxylanases in wheat flour bread-making.
Journal of Cereal Science, 35(3), 225–243.
DOI: 10.1006/jcrs.2001.0433
Sintesi: distinction WE-AX/WU-AX and key role in hydration, viscosity, and dough.
[3]. Saulnier, L., Sado, P.-E., Branlard, G., Charmet, G., & Guillon, F. (2007).
Wheat arabinoxylans: Exploiting variation in amount and composition to develop enhanced varieties.
Journal of Cereal Science, 46(3), 261–281.
DOI: 10.1016/j.jcs.2007.06.014
Sintesi: technological role of arabinoxylans in gas retention and dough structure.
[4]. Oudgenoeg, G., Dirksen, E., Ingemann, S., Hilhorst, R., Gruppen, H., Boeriu, C. G., Piersma, S. R., & Voragen, A. G. J. (2001).
Horseradish peroxidase-catalyzed oligomerization of ferulic acid on arabinoxylans.
Journal of Agricultural and Food Chemistry, 49(5), 2503–2510.
DOI: 10.1021/jf000595x
Sintesi: demonstrates the role of ferulic acid in cross-linking and network stability.
[5]. Shewry, P. R., & Hey, S. J. (2015).
The contribution of wheat to human diet and health.
Philosophical Transactions of the Royal Society B, 370(1679), 20140271.
DOI: 10.1098/rstb.2014.0271
Sintesi: highlights differences between ancient and modern wheats and the role of the non-starch matrix.
[6]. Abdel-Aal, E.-S. M., Hucl, P., Sosulski, F. W., & Bhirud, P. R. (1998).
Kernel, milling and baking properties of spring-type spelt and einkorn wheats.
Journal of Cereal Chemistry, 75(5), 736–742.
DOI: 10.1094/CCHEM.1998.75.5.736
Sintesi: comparison between hulled and modern wheats, including fiber and arabinoxylan content.
[7]. Hidalgo, A., & Brandolini, A. (2014).
Nutritional properties of einkorn wheat (Triticum monococcum L.).
Journal of the Science of Food and Agriculture, 94(4), 601–612.
DOI: 10.1002/jsfa.6382
Sintesi: highlights genetic variability and differences in fiber composition.
[8]. Gebruers, K., Dornez, E., Boros, D., Fras, A., Dynkowska, W., Bedő, Z., Rakszegi, M., Delcour, J. A., & Courtin, C. M. (2008).
Variation in the content of dietary fiber and components thereof in wheats in the HEALTHGRAIN diversity screen.
Journal of Cereal Science, 48(3), 845–857.
DOI: 10.1016/j.jcs.2008.01.012
Sintesi: demonstrates the combined effect of genotype and environment on fiber (including arabinoxylans).